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Just following the Senate bill (S. 3458) that was introduced to protect home health payment, a companion bill (H.R. 6932) was introduced in the U.S. House of Representatives that would eliminate the Centers for Medicare and Medicaid Services' (CMS) ability to reduce reimbursement rates for home health care.
The Bipartisan Budget Act (BBA) of February 2018 authorized CMS to make rate adjustments on the basis of assumptions of provider behavior in response to payment model changes. CMS responded by proposing a 6.42 percent rate reduction in its annual update in July.
H.R. 6932, sponsored by Reps. Ralph Lee Abraham (R-LA-5), Scott DesJarlais (R-TN-4), Vern Buchanan (R-FL-16), Terri Sewell (D-AL-7), and Garrett Graves (R-LA-6), removes the authorization for CMS to impose rate adjustments that are assumption-based changes, instead requiring that observed evidence of provider behavior change be the method for determining rate adjustments. Additionally, the legislation calls for a phase-in of the adjustment should it exceed two percentage points.
Keith Myers, Chairman of the Partnership for Quality Home Healthcare, also applauded the legislation in a joint statement with NAHC. "The Partnership applauds this group of Senate and House lawmakers for introducing these vital pieces of legislation, which will better align Medicare payment with patient care by ensuring payment adjustments are made based on observed behavioral changes among providers. With more and more seniors – especially seniors who are frail and suffer from multiple chronic conditions – requiring home healthcare, it is critical that payment reforms are based on actual behaviors, not arbitrary assumptions, so that home healthcare services are not disrupted."
Please urge your U.S. Congressman to support H.R. 6932.
As part of payment reforms to the Medicare Home Health benefit, CMS is going well beyond congressional intent and is proposing deep cuts to reimbursement rates based on assumptions about provider behavior. No data or evidence was used in their assumptions. This will undoubtedly harm home health patients and providers.
In February, Congress passed the Bipartisan Budget Act (BBA) of 2018. Included in this law were various reforms to the Medicare Home Health benefit. One such provision called for budget neutrality in any change to the payment model, so that future spending would remain consistent with projections of current spending levels. Additionally, Congress authorized CMS to make changes in reimbursement rates based on assumptions of actual provider behavior in response to the payment model reforms.
CMS has since taken this authority and proposed a 6.42% rate reduction in 2020. These reductions are based on the assumptions that providers will up-code and also add additional visits to LUPA cases to obtain the full episodic payment rather than data of actual provider behavior.
It is notable in their finalized rule for the Skilled Nursing Facilities, CMS states that they did "not have any basis on which to assume the approximate nature or magnitude of these behavioral responses." It is vastly inconsistent for assumptions to be made about one provider type, but not another.
Legislation (S. 3458) introduced by Senators Kennedy and Cassidy seeks to remedy these inconsistencies by removing the ability to adjust rates based on assumptions, but rather in response to observed evidence of behavioral changes. Please urge your Senators to support S. 3458.


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Retail pot ban won't make ballot
KENNEBUNK — Sometimes, the gears of government move slowly, and when the question is how or even if to open up a brand new industry, that may not be a bad thing, Kennebunk selectmen say.
At a July 18 workshop, selectmen agreed to work on an ordinance to ban growing and testing marijuana for commercial purposes, as well as the manufacture of products containing the product. Also scheduled to get the nix were retail stores and so-called marijuana social clubs.
Although the state legislature has recently pitched a 20 percent tax on the marijuana sales — including a 10 percent excise tax and a 10 percent sales tax — with 5 percent of the total haul funneled to towns allow commercial harvesting and/or dedicated retail shops, selectmen said the carrot proffered was too small to move their collective cart.
"I don't care what the taxes are, the money just isn't worth it," Selectman Ed Karytko said. "The consequences of what could happen aren't worth any amount we might get paid."
Planning board members attended that session and a draft of the proposed ban, presented by town attorney Natalie Burns, was made available. The hope was to have the planning board review the draft and hold the public hearing required of all zoning ordinances changes, then make a recommendation on passage back to selectmen, who had already signaled an intent to put it on the November warrant.
However, the planning board has had a full docket of late, planning director Judy Bernstein has said, and did not get to the issue until its Aug. 14 meeting. That session did not include a public hearing.
"Our charge to them was to come back to us with an ordinance to ban this, but all they really did was talk about whether they thought it was a good idea or not," Karytko complained at the Aug. 22 selectboard meeting.
"I'm a big fan of the planning board, but in this case they shouldn't really be thinking about whether this is right or wrong, or whether we should or should, they should basically be writing that ordinance and that's it."
"The wheels are in motion," Town Manager Michael Pardue said, noting the the planning board is scheduled to take the issue up again at its Sept. 11 meeting.
In the meantime, Pardue said, the board will need to extend for a second time the moratorium put in place last fall, soon after the statewide vote that legalized marijuana for recreational use.
Following that November 2016 vote, Kennebunk residents agreed Feb. 28 by a vote of 366-83 to adopt a moratorium on licensing retail marijuana operations of all types while the state legislature works out the rulemaking involved in permitting such operations.
That temporary ban was backdated to Oct. 25, and was set to expire April 9. However, on March 28 selectmen extend the moratorium an additional 180 days, to Oct. 6.
"I know the planning board is trying to do their due diligence, but the reality is that the matter before everyone right now is to consider prohibiting retail marijuana sales until such time as due diligence can continue for however long is necessary," Pardue said.
Selectmen are expected to extend the moratorium at their first meeting in October. That will keep anyone from submitting an application until the town passes a full local ban on retail operations — even then marijuana will still remain legal for small scale personal cultivation and use — or creates the zoning language needed to say where such shops can operate.
However, some selectmen, including board chairman Dick Morin, were in favor of taking unilateral action even without the planning board on board, as it were.
"Let's go on the record right now that if they don't come to a conclusion on the 11th [of September], we will on the 12th," he said. "We are looking for a no. That's all we want. We can turn no into yes later, but we are looking for a no right now to be able to proceed with getting this thing on the ballot and taken care of.
"The state of Maine is in a state of flux with this. They have not issued any rules or regulations, they have absolutely no idea what they are doing, or where they are going," Morin said. "It makes no sense to study this and study this when there is not where to go."
Selectman Blake Baldwin agreed, saying, "It's a fool's errand to suppose more data is going to provide both the answer and the question."
He and others on the board suggested that with a ban in place, the town can always vote to lift the ban once state rulemaking is complete, probably after February 2018.
"This is not Moses coming down from the mountain with the tablets," Baldwin said. "We can pass and then change as circumstances warrant, as more data becomes available that might change people's minds. But right now this isn't even close, based on what I am hearing from people in the community."
However, Town Clerk Merton Brown said that a Sept. 12 vote by the selectboard would not leave enough time to hold the necessary public hearings and still have absentee ballots ready 45 days before the election.
"We have a charter, and we would have to have the first public hearing at the meeting on the 12th," he said. "To make the November ballot you'd have to decide tonight if it was even going to go on the warrant."
The left the board back at Pardue's suggestion to stand pat with the moratorium. In that case, two more renewal would be needed before the annual town meeting in June, unless selectmen choose to stage a special town meeting at some point before that.
That leaves the question open as to whether the June vote will remain the board preference to present residents with a full ban on retail marijuana operations, or if, by then, the development of state permitting rules with encourage a drive toward zoning language to permit use in certain areas of town, under given conditions.
"I just want to get this out of a neutral gear in the planning board and moving forward so we can get some actual votes," Morin said.
Morin pointed out that, while the town can renew a moratorium on certain development applications for an unlimited number of times, those renewals are, in theory at least, contingent on demonstrating the town has continued to work on and made progress toward resolving the conditions that created the need for the ban in the first place."
Staff Writer Duke Harrington can be reached at firstname.lastname@example.com.

subset: commoncrawl


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Can anybody guide to put a different font in 9300i. Where is the font folder in file manager
Its a amazing phone to use in coparision to any of the business phone..its fun
The phone is awesome its got everything i need like excel and powerpoint and camera is not at all needed as i have a 6mpix digicam
I believe that this phone is a great phone for the price. My only problem is no camera. other than that this is a great phone.
at last there is SKYPE for 9500/9300i :) but only chatting function works..
As mentioned on nokia and your websites that nokia 9330i support MPEG4 files but it doesnt support the mpeg4 files and I have got in writing from nokia care that it will not support mpeg4 as claimed my the company
Sorry I forgot to add, if someone wants to be a photographer kindly buy a Digi SLR Camera phones are not meant to be used a cameras where one can do his little hobby and waste time sending it to others and creating a complete idiot of himself.
I have just read few opinions posted by some, one of the guys want to run Mpeg4 and the other wants a camera another one wants to hear music while surfing net. God bless them and one of the guys is getting his money back from Nokia, great. But I would just like to say that I found this phone great. But before we start calling Nokia names we should know what we need and do a little bit of survey before buying any product, I am very satisfied with this handset, this works better than 9300 and wlan works just fine.
i just luv this phone got alot of functions bit slow but o k nokia is a top dog
Really nice phone to use...very slick compared to other communicators...good speed...nice web browser with mouse cursor...& very simple to use...the full keyboard is very useful for sending mail & sms's...excellent phone
It's a nice phone.easy to use,but the software is really slow...i must wait a few second to open application...no camera,no vibration its ok...like 9210i...
Is Nokia 9300i can HELP ?
Im browsing (gprs connection) use opera & Nokia web.
Why when someone send message to me the ALERT not ring ?
The message reveived but i can't hear the sound (my songs),Thank you
No camera? this phone sux! some people says, if you wants a camera, why not buy a camera. if you wants music, why not buy mp3 player. But why buy all those when you can have all in one device? would you carry all those equipment around all time? this phone works great but no camera, its like 1/10 for me where the full functionality of a divice would score 9/10.... its only lack of camera..... sorry... 1,1,1 vote for you....
As mentioned on nokia and your websites that nokia 9330i supports MPEG4 files but it doesnt support the mpeg4 files.I have got this thing in writing from NOKIA CARE (Green Park, Delhi) that it will not support mpeg4 as claimed by the company. Now Nokia people are ready to refund my money and take back the handset so that they can fool other people.


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What factors affect the led light quality? How to know the led light is good or not? Today we will introduce some normal factors, to make you feel clearly when choose led bulbs, led light fitting, led ceiling lamp.
1. CRI (Ra)
CRI Represented by Ra, the maximum figure 100 is the best. Energy saving lamp is 80~90, LED is 70~90, our LED light reach more than 80.
2. Luminous Flux (lm)
Luminous Flux represented by lm, used for explain the total amount of light glow. The larger of lm, the more light it emit.
3. Luminous Efficiency (Lm/w)
Luminous Efficiency is Luminous Flux divided by Power, is a important index of energy saving light. Luminous efficiency of LED light can reach more than 80. Our LED light can reach more than 90.
4. Power Factor (PF)
Power Factor show the ability of output of active power. Power Factor is Actural Power divided by Apparent Power, that is PF=P/U*I. General PF is between 0.5 to 0.6, Europe has strict requirement of Power Factor, should reach 0.9, comply to EMC standard. The larger of PF, the lower of current, will save energy.
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Author David Grossman will receive the Israel Prize in literature this year, Education Minister Naftali Bennett announced on Twitter.
"I was very excited to inform David Grossman on the decision to award him the Israel Prize in literature on the State of Israel's 70th year," Bennett wrote. "Grossman is one of the most exciting, deep and influential voices in Israeli literature."


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from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. In a photolithographic way.
Sorry, no etymologies found.
For the most accurate and fine-featured applications and the mass production of micro shims, Tecan uses Photo Electro Forming (PEF) - where the parts are grown electrochemically into a photolithographically-defined resist mould.
For low-cost tooling and rapid prototyping of burr and stress-free parts in a range of metals up to 1. 5mm thick, Tecan uses Photo Chemical Machining (PCM) - where the parts are produced by selectively removing metal by chemical etching through a photolithographically-defined resist layer.
MEMS structures are photolithographically patterned in alternating layers of deposited polysilicon and silicon dioxide, and then are "released" by dissolving away the silicon dioxide layers.


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[Social Awareness]
Wake up, sportsfans! You're better than this!
by Michelle N.
It was brought to my attention, in my newsfeed the other night (The Animal Rescue Site- add on Facebook and a daily FREE click helps feed shelter animals) that some rather disturbing things are going on in the Ukraine.
In preparation for Euro2012, they are 'cleaning up', taking care of the stray dog/cat issue. They've been known to use some rather callous approaches to animal control, but the new method they've chosen is something so incomprehenisble, I was unable to sleep after reading about it.
Apparently, using poison and shooting these animals wasn't quick or effective (or heartless) enough, so they've spent $20,000 on a mobile incinerator, with the official use being cleaning up the carcasses of dead dogs and cats who have been hit by cars, etc. They lead you to believe the animals are put down first, but the cheap, ineffective drugs they are using aren't the same things they use at your local vet, and more than a few people believe these animals are still alive when they are bagged, gathered up and thrown into a 900 degree celsius furnace. All of this needless suffering, for a SOCCER GAME. The money allotted for humane animal control is suspiciously missing. It certainly wasn't used for spaying/neutering.
I encourage all compassionate people to share this, to sign petitions, to boycott the game. This story needs to be told. This has been going on since 2007. I don't want to believe I live in a world where this is acceptable, where people look away and ignore it. I don't care where you stand on animal rights issues, this is beyond the pale in terms of cruelty. If you watch the game, I hope you remember this. If you enjoy the game, knowing what you know- what does that say about you?


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The best reason for Maine to expand Medicaid eligibility to the limits of the federal Affordable Care Act is that it would be good public policy.
It would make about 69,000 uninsured Mainers eligible for the program.
Ample research shows that people with health insurance are healthier and live longer than those without it. They are also less likely to end up in emergency rooms because they seek earlier interventions in less costly settings.
Uncompensated charity care in emergency rooms is one of the cost drivers in health care that all insured Mainers and taxpayers are paying for as health costs climb.
Gov. Paul LePage has so far refused to accept that argument, insisting instead that Maine trim its Medicaid rolls, calling the cost shift "welfare reform."
Even if LePage doesn't accept the underlying public policy argument, however, there are still strong reasons for Maine to participate in the Medicaid expansion, as Republican governors in other states have come to see.
The first is the cost: There isn't any, at least at first. If states extend Medicaid eligibility to people with an annual income up to 138 percent of federal poverty limit — $15,000 a year for an individual or $25,500 for a family of three — the federal government would pay 100 percent of the additional cost for the first three years of the program.
After that, it would pay no less than 90 percent. Accepting the federal money now does not obligate the state later, and Maine could chose to opt out of the program in three years if it doesn't want to pick up the cost.
That convinced Florida's Republican Gov. Rick Scott, who abandoned a rhetorical stance similar to LePage's and announced his state would accept the funds.
Maine has an opportunity to benefit even more than Florida, because, even without the expansion, Maine exceeds the federal minimums for Medicaid eligibility. If Maine complied with the ACA, the state would receive the 100 percent subsidy for those recipients, instead continue to pay 40 percent of their coverage as we do now.
The second reason Maine should participate is the economic benefit that would flow from what could be $100 million per year in federal spending.
That money goes to hospitals, clinics and doctors who maintain offices and employ people. It's money ultimately spent on real estate, property taxes, groceries — even to the contractor who plows snow from the parking lot.
Why would Maine say no to these funds? That was enough to convince New Jersey's Republican Gov. Chris Christie to drop his opposition to the ACA and expand Medicaid in his state.
And LePage should remember that Mainers pay federal taxes, too, so while he takes a principled stand on not expanding MaineCare eligibility, we will help subsidize expanded Medicaid in New Hampshire, Massachusetts, Connecticut and New York while we struggle to balance our budget at home.
That's what swayed Arizona's Republican Gov. Jan Brewer, who stopped blocking her state from participating.
LePage and these other governors were opposed to the health care reform act. Republicans tried to stop it in Congress. They tried to stop in the courts. Mitt Romney promised to repeal it if he was elected president.
All of those efforts, however, failed. LePage does not have to agree that expanding MaineCare eligibility is the right public policy, but he can't argue that it's not the law of the land.
He can continue to hold an ideological position that has been abandoned by other ACA opponents, or he can take a more pragmatic view, based on reality.
The reality is that expanding MaineCare eligibility is the right thing to do for a variety of reasons. Maine proves nothing by holding out.
Varsity Maine
Local roundup: Monmouth girls basketball holds off Madison
Nation & World
President Trump seeks to assure opponents of abortion rights that he stands with them
Varsity Maine
Hall-Dale girls basketball outlasts Dirigo in OT
Pelosi cancels overseas trip, saying Trump raised security risk
Nation & World
Chicago police officer goes to prison for killing black teenager


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Dinitrogen-Transition Metal Complexes Synthesis Properties and Significance.код для вставкиСкачать
[51] Th. Kauffmonn, Angew. Chem. 76, 206 (1964); Angew. Chem. internat. Edit. 3. 342 (1964). [52] Cf. M . J . S. Dewar, Angew. Chem. 83,859 (1971); Angew. Chem. internat. Edit. 10, 761 (1971). [53] R. Eidenschink and Th. Kauffmann, Angew. Chem. 84,292 (1972): Angew. Chem. internat. Edit. 1 1 , 292 (1972). [54] W Bannwarth, Diplomarbeit, Universitat Miinster 1974; W Bannwarth, R . Eidenschink, and Th. Kauffmann, Angew. Chem. 86, 476 (1974); Angew. Chem. internat. Edit. 13, 468 (1974). [55] A cycloaddition of this type might take place in the formation of a cyclic dimer (39%) during the actlon of sodium on a-methylstyrene ( M . Kolobielski and H. Pines, J. Amer. Chem. SOC.79, 5820 (1957)). [56] G Boche and D. Martens, Angew. Chem. 84, 768 (1972); Angew. Chem. internat. Edit. I I , 724 (1972) [57] G Boche, personal communication 1973 [58] J . E. Mulraney and D . Savage, J. Org- Chem. 36, 2592 (1971). [59] T h e reactions of (63) and similar compounds with alkenes and other unsaturated compounds are now in the course of thorough investigation: cf. ref. [54]. [60] Rearrangement of 1,3-diphenylpropyne to 1.3-diphenylallene by bases: E. V Dehmlow. Chem. Ber. 100. 3260 (1967): H . A. Staab and H.-A. Kurmeier. ibid. 101, 2697 (1968). [61] D. Serbach, Angew. Chem. 81. 690 (1969): Angew. Chem. internat. Edit. 8. 639 (1969). and literature cited therein: mechanism: K . D. Berlin, 8.S . Rathore and M Peterson, J. Org. Chem. 3U, 226 (1965). [62] R . B. Bates, L. M . Kroposki, and D. E . Potter, J. Org. Chem. 37, 560 (1972). [63] A. Alemagno, T Baccetti, and C. Rizzi, Gazz. Chim. Ital. 102, 311 (1972). [64] L. Claisen, Ber. Deut. Chem. Ges. 36, 3673 (1903); J . Goerdelrr, J . Ohm, and 0 . Tegrmeyer, Chem. Ber. 89, 1534 (1956): R. L. Letsinger and D. F . Polhrt, J. Amer. Chem. SOC. 78, 6079 (1956); H . Kloosrerzirl, J . A. A. can Drunen, and P. Galama, Chem. Commun. 1969, 885; P. Eberhard and R. Huisgen, J. Amer. Chem. SOC. 94, 1345 (1972). [65] 1,3-Diphenyl-2-azaallylsodiumand -potassium were prepared in solution by the thermal ring opening of cis-1,2-diphenyl-l-aziridinylsodiumand -potassium in THF at 20°C 1191, a s well a s by the action of N a N H l or K N H 2 on N-benzylidenebenzylamine in ether at 0 ° C [17, 661 A solution of 1,3-diphenyl-2-azaallylmagnesiumbromide was obtained by the action of mesitylmagnesium bromide on N-benzylidenebenzylamine in THF at 67°C C661. [66] D. Beryrr and Th. Kauflmann, unpublished work. [67] Cf. P. Hrrmbach and R. Traunmiiller Chemie der Metall-Olefin-Komplexe. Verlag Chemie, Weinheim 1970; W P. Giering and M . Rosenblum, J . Amer. Chem. SOC.93,5299 (1971): A. Rosau, M Rosenblum, and J . Tancredu, ibid. 95, 3062 ( 1 973). Dinitrogen-Transition Metal Complexes: Synthesis, Properties, a d Significance By Dieter Sellmann[*] Compared to the large number of CO complexes, N 2 complexes are still rare. In certain cases they may be formed from N 2 gas and metal compounds under physiological conditions, and are therefore frequently considered as possible intermediates in N z assimilation. However, despite numerous attempts it has not yet been possible to reduce the N Z ligand of a fully characterized N z complex to N H 3. This negative evidence recently prompted the discoverers of the first dinitrogen complex, the [Ru(NH&N2lZ@ ion isolated in 1965, to express doubt whether such complexes really d o play a part in the enzymatic reduction of N2. The latest findings nevertheless incline toward a somewhat more optimistic view. Thus, the mild partial reduction of the N 2 ligand in metal complexes with inert gas configuration, hitherto considered nonreducible,justifies the hope that a suitable system permitting the catalytic reduction of molecular nitrogen under normal conditions will one day be found. Even apart from any technical potential, the N complexes constitute an interesting chapter of modern inorganic chemistry. 1. Introduction Under normal conditions molecular nitrogen is usually found to be chemically inert. Thus, reactions involving the Nzmolecule generally require drastic conditions, e. g. elevated temperatures and pressures, as in the Haber-Bosch process. However, nature is capable of converting atmospheric nitrogen enzymatically during N 2 assimilation into ammonia and amino acids under mild physiological conditions ( 1 5 "C, 0.8atm. N2, aqueous medium). In chemistry, only one defined reaction of the N 2 molecule is currently known which also proceeds under physiological conditions: the reaction with metal compounds to yield dinitrogen complexes. This reaction [*] Dr. D. Sellmann Anorganisch-chemisches Laboratorium der Technischen Universitat 8 Miinchen 2. Arcisstrasse 21 (Germany) Angew. Chem. internat. Edit. / Vol. 13 ( 1 9 7 4 ) I N O . 10 can clearly be considered as a model for the absorption of atmospheric nitrogen by the Nz-assirnilating enzymes in nature. Hence the fundamental significance of the reaction and its products. What features characterize the reaction partner, which allows reduction of the normally inert molecular nitrogen during the course of assimilation? Biochemists are trying to answer this question by the isolation and study of the nitrogen-assimilating enzymes, the nitrogenases; purely chemical means are employed by chemists attempting to simulate nature in uitro by fixing molecular nitrogen to synthetic compounds. Since transition metalsespecially molybdenum and iron-are present in the nitrogenases, systems containing these metals are of particular interest. What the chemist wants is a defined system in which he can follow the reduction of the Nzmolecule step by step. 639 Isolable and unambiguously characterizable model substances thus appear especially important. Nz-fixing chemical systems can be roughly divided into protic and aprotic. The impetus which led to the investigation of the aprotic group was the observation that Ziegler-Natta catalysts and similar compounds absorb nitrogen and reduce it to nitride-type products. The fundamental difference between these systems and the nitrogenases lies in their aprotic character: the hydrolytic susceptibility of the organometallic components ( e . g. Grignard reagents, alkylaluminum derivatives, alkali metal naphthalides) makes rigorous exclusion of water essential. The reactions which proceed in such systems are therefore reminiscent of the well-known reaction between nitrogen and lithium to give Li3N. Coupled with the fact that, with few exceptions, unambiguously characterized compounds could not be isolated, this proved to be a disadvantage compared with the second group, the protic systems. These are capable of existing in aqueous or other proton-containing solvents, and the reaction with molecular nitrogen yields welldefined products, the N 2 complexes, which will be discussed below I. 2. Definition, Nomenclature, Possible Modes of Bonding Dinitrogen complexes are coordination compounds which contain the Nz molecule as ligand. The first example of this class of compounds was discovered by Allen and Senoff in 1965[']. The attempted synthesis of ammine complexes from RuC13 and hydrazine hydrate did not yield the expected [Ru(NH3)6I2@ion but the stable complex [(NH&RuN2]CI2 instead. Long before thisdiscovery, the realization that Nz-assimilating bacteria require molybdenum in order to fix atmospheric nitrogen had led to the hypothesis that dinitrogen-transition metal complexes play a part in this process[3! However, numerous unsuccessful attempts to prepare such complexes as well as subsequent theoretical considerations led to the assumption that these compounds were not stable. The isolation of the first stable N z complex, and the hope ofobtaining information on N 2 assimilation through the study of this new class of compounds, stimulated an intensive search for further examples. The result is a respectable number of new dinitrogen complexes; compared with the hundreds of complexes formed by the isoelectronic carbon monoxide, however, they must still be considered a rarity. According to the IUPAC rules14a1,the N2 molecule is named "dinitrogen" when it is a formally uncharged ligand in coordination compounds. Other proposals such as "nitrogenyl" (by analogy with "carbonyl"), "nitrogeno", or "nitrogen" should therefore be avoided. In principle, several possibilities are conceivable for the linkage between dinitrogen and metals (Scheme 1). These are in particular : terminal ("end-on") bonding [ ( I ) ] , lateral ("side-on", or "edge-on") bonding [ ( 2 ) ] , bridge bonding via one of the N atoms [(3)], terminal bridge bonding via both N atoms with a metal atom on each nitrogen [ ( 4 ) , ( 5 ) ] o r two metal atoms on each nitrogen [ { 6 ) ] . ( 1 ) and (3) correspond to the bonding in terminal and bridged carbonyl complexes respectively, (2) is comparable to the bonding in acetylene com- 640 plexes. In (I), (2),and ( 4 ) the triple bond in the N2 molecule is largely retained, but not so in ( 3 ) , ( 5 1 , and (6). ( 5 ) is therefore to be regarded as a complex of the doubly depro- Scheme 1. Linkage possibllities of the N 2 ligand tonated diimine HN=NH, and (6) as a fully deprotonated hydrazido complex, rather than as dinitrogen complexes. So far, only bonds of types ( I ) , ( 4 ) , and (6) have been unequivocally demonstrated in Nz complexes; (2) has been postulated. The structural unit (6) is present in the complex [{(PhLi)3Ni)2N2.2Et2OI2[*1. Here the two Ni atoms and the two atoms of the N2 molecule occupy the corners of a distorted tetrahedron: two such [Ni2N2] units are bridged cia two Li atoms. A side-on 71 bond between the N 2 molecule and the metal centers is considered as a possibility; accordingly, ethylene readily displaces the N z ligand from the complex. The length of the N-N bond was found by X-ray structure analysis to be 1.35A, the highest value yet encountered in a N2 complex. This value approaches that of an N-N single bond (1.47 8)and points to a considerable activation of the N 2 molecule[4b~. A Pt complex, formed from ~is-[PtC12(PPh3)~] and hydrazine, contains the structural unit (3) in protonated form'51(Fig. 1). Flgure 1. Schematic structure of [jPt(PPh,)>N2Hi2]". Molecules related to terminal N2 complexes include N 2 0 , HN,, CH2N2,C,H5NYXe, and 1,10-Bi,H,(N2)2,which may be considered as an internal diazonium salt[h1.These nonmetallic compounds containing the N grouping are not discussed here, nor are substances such as azobenzene, Ph-N=N-Ph, which are only formally related to bridged N complexes. 3. Preparation of Nitrogen Complexes Table I summarizes the data on unequivocally characterized N complexes. Apart from chloride and ammonia, phosphanes and hydride ions appear remarkably often as coligands of Nz. It was not until very recently that N 2 complexes were synthesized with arene and CO ligands. In view of the high sulfur content of the nitrogenases, it is surprising that so far only one very unstable and poorly characterized N Z [*] For abbreviations see Table I , footnote [a]. Angew. Chem. internat. Edit. 1 Vol. 13 (1974) 1 No. 10 Table I . Some dinitrogen complexes. ~~~~ . ~~ .- - ... . -__ . . Complex [a] . . ~ Color ... _- . 2145 [h] 2132 [b] 21 12 [h] . . . ... yellow-orange d" 2040 orange dark red yellow d 'l d' d" orange d ', 2000 [L] 1925 [L] 1911 [d] 199x 1957 [d] [L] I975 ~ _.. ~~~ reddish-brown yellow yellow yellow yellow red . . ... -. .. ~ ~ . - 2169 [b] 2141 [b] 1925 [el 19x0 [c] 2060 [d] 7060 d" d" d" d" d" d' - . ycllow orange d6 d" d white white yellowish ycllouish yellowish d" d '' d" d" d6 2147 rgl 2 I 70 21 14 [g] H hite d 2157 [g] d" 20x5 20x2 2057 202x 2 I20 217s [d] [g] 2093 [fl 19x9 [gl 2057 2090 ?' rg] - r110 [g] 2220 [g] 2190 M d '' d" hitr nhite yellowish ~ d '' d6 ... ~~ . 2090 [d] 1x75 [f] 2 IS2 [g] 2105 [c] . - - orange ~ -. . ..- . ... - 2076 [d] ~~ hlue red red brown brown .- . -. [d] ~~ red rcd-orange hlack yellowish ).ellow - [g] .- - 12x0 1910 [h] 1910 -~ dark red yellowish red-blac k red gold yellow gold brown - 187.5 2054 [h] 1660 1761 2100 [h] 20x0 dark hroiln dark red dark red [a] Ahhre\iations: acac = 3.5-pcntanedionate, Cy = cyclohexyl ; das =ethylenehisldiphenylarsanc)Ph,AsCH2CH2AsPh2, dcpe = cthylcnebis(dieth~1phoaphaiic) Lt, PCH,CH PEt ; diphos = ethylenchis(dipheny1phosphane) Ph, PCH > C H , PPh, : dmpe = ethylenehis(dimethy1phosphane) Me, PCH ,CH PMe, ; dpsc = 1.2his(pheny1thio)ethaiie PhSCH,CH,SPh; en=ethylenediaminc; Et -ethyl; h m b = hexamethylhenrenc, M =metal: Mc=methyl. mes=mesitylenc: Ph-phenyl; THF=tetrahydrofuran; tol=toluene. [b] In herane. [c] in toluene; [d] in benrenc; [el in chloroform. [f] in tetrahydrofuran; [g] in n u j o l ; [h] in the Raman spectrum. [I] Recently the first N, complex with a porphyrin ligand was prepared: ~~?r~i~~-o~taethylporphinato(dinitrogen)tetrahydrofur~inosniium(i~). see J . W Birchlrr. a n d P. D. Snirrh. Angew Chem.. in press. , , , complex with a sulfur-containing ligand is known: trans[M O ( N ~ ) A P M ~(PhSCH ~ P ~ ) 2CH ~ SPh)]. Table 1 does not include N 2 complexes obtained by matrix isolation at low temperatures (ca. - 196"C), e . g . CrN2, NiN2, PtN 2I 7 I , Ni(N dn,Pd(N2),181, and Ni(CO)3N2l9]. Angew. Chrm. internat. Edit. Vol. 13 ( 1 9 7 4 ) I No. 10 Thus far three possibilities exist for the preparation of N, complexes: 1 ) Direct reaction of N z with a metal complex, frequently under strongly reducing conditions. 641 2) Conversion of a metal complex with ligands containing N-N bonds, e. g. N2H4 or N?. 3) Formation of an N2 triple .bond in a metal complex by reaction of ligands such as NH3 with a nitrogen-containing reagent, e. g. H N 0 2 . 3.3. Formation of an N 2 Ligand from an N 1 Ligand Ammine complexes can be diazotized with nitrous acid, but this method is of very limited application. [Os(NH,)5N21Ze + HNOz + c . i s - [ O ~ ( N H , ) ~ ( N 2 ) 2+] ~2~H 2 0 (15) 3.1. Direct Methods 4. Structure of Dinitrogen Complexes A metal complex in the presence of excess ligand is reduced under N, by metals, metal amalgams, or hydrides. N, [WCI,(PMe,Ph),]+Na/Hp --j A toluene [MoCI,(PMe,Ph),]+Na + NaBH, [FeHCl(depe),] [W(N,),(PMe,Ph),] (1) [Mo(N,),(PMe,Ph),] (2) [FeH(N,)(depe),]BH, a,,~~ne + NaCl (3) Alkylmetal compounds may also be used as reducing agents. Presumably they introduce an alkyl group into the metal complex; the ensuing olefin elimination produces a hydride complex which then reacts with the NZ. Suitable reactants include AIEt,(OEt), AlEt,, and Al(iBu),. AIMe, yields mainly methyl complexes. 4.1. Molecular Structure That the metal-N-N or metal-N-N-metal unit in terminal N z complexes is approximately linear is apparent from the strong IR absorption of the N z stretching vibration; a side-on linkage of the N 2 ligand, as in ethylene or acetylene complexes, would produce only weak IR absorption. Clear evidence for a linear arrangement is provided by X-ray structure analysis (Fig. 2), although accurate determination of bond lengths failed in many cases owing to disorder phenomena. N I N C) Figure2. Schematic structures of(a)[CoH(N&PPh,),], (b) [ O S ( N H ~ ) ~ N ~ ] " , and (c) [ { R u ( N H ~ ) ~ } z N ~ ) ~ " . Labile ligands in metal complexes can be displaced by Nz. These are the clearest reactions of molecular nitrogen; they proceed under mild conditions and are frequently reversible. [CoH,(PPh,),] + N, EtOH + N, [Ru(NH,),H,O]'" [Ru(NH,),N,]~" 2[C5H,Fe(dmpe)acetone]" + N, - + H,O (8) acetone [/C,H5Fe(dmpe)},N,]2@ [(hrnb)Cr(CO),] 17) d [CoH(N,)(PPh,),l +.H, + 2acetone + T H F 3 [(hrnb)Cr(CO),THF] + CO 2[(hrnb)Cr(CO),THF] THF + N, [ j(hmb)Cr(CO),/,N,] (9) (10a) + 2THF ( l o b ) In some cases the intermediates cannot be isolated but immediately react further with Nz, as in the reaction according to eqs. (1Oa) and (lob). 3.2. Conversion of a Ligand with N-N Bonds into N2 + PhCON, 0-C CHCI, truns-[lr(N,)CI(PPh,),] /O\ [(PPh,),Cl,Re--N=N-CPh] + ZPPh, truns-[ReC1(N,)(PPh3),] [C,H,Mn(CO),N,H,] (RuCl(das),N,]PF, + 2H,02 + NOPF, - + HCI + PhC0,Me (11) (12) CU'".THF -40 [C,H,Mn(CO),N,] [RuCI(N,)(das),]PF, 642 + PhCONCO +4H,O + by-products Since the nitrogenases also reduce acetylene (to ethylene), it should be pointed out that the structures of (end-on) N Z complexes bear not the slightest resemblance to the acetylene complexes in which the two C atoms of the C z H 2 are linked to the metal in the same manner. Instead, they are similar to acetylide complexes, e. g. Kz[Cr(C0)3(C-CH)3][561. 4.2. Bonding Most systematic syntheses of N, complexes were successful by this method. rruns-[lr(CO)C1(PPh,),] Table 2 summarizes the most important data. The N-N distances of coordinatively bound dinitrogen are only marginally greater than in the free N2 molecule. The complex [{(PhLi)3Ni) 2Nz-2Et20]2[4bJ,which contains the structural unit (6) (Scheme 1) and in which ~ N - N = 1.35A, is an exception, as is [ReC1(PMezPh)4-N z-MoC14(0Me)] with ~ N - N = 1.21 A[67b! For comparison, the length of the NN double bond (in diazomethane) is 1.24A and that of the N N single bond (in hydrazine) is 1.47 (13) (14) The structures of N 2 complexes largely resemble those of the analogous isoelectronic C O complexes, thus revealing similarities in electronic structure. However, while carbon monoxide forms numerous mono- and poly-CO complexes, only a few monocomplexes are known for dinitrogen; among the higher complexes, only bis-N, species have been reported. The reason for this, and for the generally greater stability of CO complexes, lies in the electronic differences between N,and CO. The following discussion of the bonding properties of NZ and CO should throw some light on this aspect. Figure 3 shows the molecular orbital scheme of dinitrogen, as derived Angew. Chem internat. Edit. 1 Vol. 13 (1974) 1No. I0 Table 2. Molecular data for some dinitrogen compounds 1.0976 1.12 [b] 1.12 1.106 1.06 [b] 2.10 1.84 1.89 1.97 1.81 1.11 1.10 2.01 1.124 1.12 1.35 1.21 1.928 1.79 1.79; 1.89 1.34 1.24 1.18 1.13 1.134 1.128 180 180 180 1481 [481 1481 [a] M =metal, C, N. or 0. [b] No accurate determination possible. from UVr571an photoelectron spectra[581, as well as from theoretical calculations[59! 0 0 1 xg antibonding degenerate pair in xy- and xz-planes, - 7 eV, unoccupied @ 30, weakly bonding - 15 58 eV, occupied (2e.) me 0 0 a=N 1 K, bonding degenerate pair in xy- and xz-planes, - 17.1 eV, occupied (4 eC) C-0 bond from 1.128 to 1.115A in the ionization CO-+CO*. The ionization N,+NY, on the other hand, results in a lengthClearly ening of the N-N bond from 1.098 to 1.117 the electron distribution in C O and N2 will also differ because carbon and oxygen have different radii, electronegativities, ett., whereas dinitrogen is a homonuclear molecule. C O possesses a small dipole moment (p=0.2D). Calculations of the electron-density distribution also show that the C atom exhibits a greater lone electron pair charge density than the 0 atom~"*]. The metal-dinitrogen bond in N 2 complexes can be described according to the MO method by overlapping of the 30, and In, orbitals of the dinitrogen with suitable d orbitals of the metal (Fig. 4). 20" weakly antibonding -18.7eV occupied ( 2 e - l 2 0 ~bonding - 35.5 eV (estimated) occupied ( 2 e . ~ ) Figure 3. Molecular Orbital scheme of dinitrogen The exceptional stability of dinitrogen compared to other diatomic molecules is a consequence of its low-lying three highest occupied bonding molecular orbitals. The actual H O M O is a bonding 3 0 , orbital of very low energy. Hence the ionization energy of N is considerable (1 5.58 eV), approximating to that of argon (15.75 eV). The LUMO, 1 n,, lies 8.6 eV above the 3 G~orbital, i. e. so high that it can be occupied at best by electrons from alkali metals and other strongly electropositive metals. The absence of orbitals in the energy range between the two, i.e. precisely that range in which the occupied and unoccupied orbitals participating in chemical reactions are located, largely explains the low reactivity of the N, molecule. While the M O scheme of carbon monoxide is very similar to that of dinitrogen, essential differences are noted in the much lower energetic stability of the highest occupied a and of the lowest unoccupied x* orbitals ( - 14.0 and 6 eV respectively) and in the smaller energy difference between these two orbitals, which is lower by 0.6 eV. In addition, the highest occupied 0 orbital in CO possesses weak antibonding character; this can be deduced also from the shortening of the ~ Angew. Chem. internat. Edit. 1 Vol. 13 (1974) 1 No. I0 Figure 4. Scheme of the M-N2 bond. As in the case of the M-CO bond, a donor bond is postulated involving the 3 0, electrons of dinitrogen and an unoccupied metal d orbital. The resulting increased electron density at the metal is reduced by back-bonding from nonbonding occupied metal d orbitals to the antibonding l n , orbital of the dinitrogen. The result is a synergetic 0-71double bond, i.r. a strengthening of the 0 bonding leads to the simultaneous strengthening of the II bonding. This type of bonding explains why N 2 complexes are less stable than C O complexes. Most metal complexes possess d orbitals (e. g. e, and t2, orbitals) whose energies correspond better to those of the 0 and n* orbitals of CO than to those of the N Z molecule. This enhanced interaction increases the stability of the C O complexes. The bond scheme illustrated in Figure 4 also explains why electronic variations result in largely analogous effects in N, and C O complexes. 643 What physical changes are to be expected in the N2 molecule as a result of coordination if the above model of the M-N2 bond is correct'? The N-N bond should become weaker on complex formation, since the electrons of the M-N o bond come from a bonding orbital ofthe N 2and those of the M-N n bond are transferred to an antibonding N2 orbital. However, this conclusion has recently been disputed. According to theoretical calculations, the removal of electrons from the 3o, orbital should reduce the electron repulsion between the two N atoms and thereby strengthen the N 2 CT bondlh1I. The weakening of the N2 triple bond would then be mainly due to the x back-bonding. The overall weakening of the N, triple bond and consequent activation of the N, molecule on complexing are clearly demonstrated by the marked drop in the N, stretching frequency, which falls by several hundred wave numbers from the value of 2331 cm- I recorded for the free molecule (Raman spectrum). Furthermore, the N2 molecule in terminal N 2 complexes is subject to strong electronic polarization, which accounts for the high intensity of the vN2 absorption in the IR spectrum. This polarization is also confirmed by the ESCA spectra of N 2 complexes. Metal-bound and terminal N atoms exhibit separate N-Is emissions, e. g. at 399.9 and 397.9 eV for [ReC1(N2)(diphos)z], whereas the emission of the free N2 molecule is observed at 41 1 eV. These values afford a charge difference of approximately 0.4 e between the two N atoms, the terminal one bearing the greater negative chargeIb2.631. Attempts to determine the properties of the N2-bonding coordination site in N2 complexes have been based primarily on comparative studies, and particularly on systematic variation of the coligands ofdinitrogen. However, since the stability limits of N z complexes are very narrow owing to the unfavorable energy of the N 2orbitals, only a few examples are available for studying the effect of the variation of coligands on the metal-N2 bond. Thus the reaction according to eq. (1 1 ) can only be effected with triphenylphosphane; tris(p-toly1)phosphane or methyldiphenylphosphane no longer yield isolable has not been finally resolved. Mossbauer spectra of trans[FeH(X)(de~e)~lBPh4(X= N2, C0)suggest that CO is a better o-donor and n-acceptor ligand than NLrzz1.The same can be concluded from IR intensity measurements on analogous CO and N2 complexedh6'. Such behavior can also be deduced from the electronic properties, i. e. the energy of the molecular orbitals, of the two molecules. However, for the compounds [CSHSM(CO)ZNZ] (M = Mn, Re) and [ArCr(C0)2N2] (Ar = benzene, mesitylene, and hexamethylbenzene) it appears from the 'H-NMR and IR spectra that both the cyclic ligands and the CO groups must accommodate a greater electron density in the N2 complexes than in the corresponding tricarbonylmetal complexes. In these compounds therefore the ratio of o-donor to n-acceptor strength must be greater for dinitrogen than for carbon monoxide[' I h . "1. '. Surprisingly, almost the same N2 stretching vibration frequency is often observed in dinuclear N 2 complexes as in the corresponding mononuclear complexes; examples include [ ( R U ( N H ~ ) ~ } ~ N(2100cm-') ~]~' and [ R U ( N H ~ ) ~ N ~ ] ' ~ (2130cm-I). Since the N-N triple bond of the N2 molecule is weakened by coordination to one transition metal, bonding to two transition metals was expected to result in further weakening. This expectation is fuIfilled only in some cases. An explanation for this phenomenon is provided by the bonding scheme of the M-N-N-M bond. If the CT bond component is regarded as largely constant, and the changes in M-N and N-N bonds are attributed mainly to variations in the x system, the scheme shown in Figure 5 applies to the TC bonds ofcomplexes with approximate fourfold symmetry, such as the complex [(RU(NH,),},N.,]~@ or the complex [( PMe, Ph),ClRe-N,-CrCI,(THF),] lS5. "'I. Experience has shown that the central metal of an N2-bonding complex must exist in a low oxidation state and possess a relatively high electron density. A fitting example is [Ru(NH~)~CO]", the CO analog of [ R U ( N H ~ ) ~ N ~ ] ~ ' [ ~ ~ I . Despite the formal double positive charge on the ruthenium, the CO compound exhibits one of the lowest vco frequencies (1919cm-') ever observed in terminal CO complexes. The effect of electron density is also apparent from the series [ ( b e n ~ e n e ) C r ( C O ) ~ N(VN] ~ ] = 2145 cm- I), [(mesitylene)Cr(CO),N,] (vN2= 2132 cm-'), and [(hexamethylbenzene)Cr(CO)2N2] (vN,=21 12cm- I). Introduction of the "ekctrondonating" CH3 substituents into the benzene ring increases the electron density at the chromium. As a result the frequency of the N 2 stretching vibration decreases; the bond scheme in Figure 4 indicates that this phenomenon should be associated with a strengthening of the M-N bond. Accordingly, the stability of the N2 complexes increases in the above sequence" '1. N 2 and CO ligands influence the central metal in very similar fashion; thus, both exert approximately the same trans effect on the Ir-X bond in the complexes rran~-[IrX(X')(PPh~)~] (X = CI, Br ; X'= N,, CO)1641.The much-discussed question of the o-donor and n-acceptor properties of Nz and CO 644 6x3 ___ 3e 2b Figure 5. Qualitative molecular orbital scheme for dinuclear N L complexes with approximate fourfold symmetry. The four-center molecular orbitals indicated in Figure 5 are obtained by linear combination of Md,,, Np,, and M'd,, orbitals. The z-axis is determined by the CT bond. A set of energy levels, whose energies increase with increasing nodal number of the molecular orbitals, corresponds to the molecular orbitals. Since, in addition to the orbitals shown, there exists an equivalent set of x molecular orbitals, formed from the Md,,, Np,, and M'd,, orbitals, the energy levels are degenerate. For the sake of simplicity they are designated as le, 2e, erc. The 6 bonds formed from the Md,, orbitals contribute Angew. Chem. internat. Edit. / Vol. 13 ( 1 9 7 4 ) / No. 10 practically nothing to the bonding; they correspond to the 1 b and 2 b levels. For energetic reasons the I e and 4e levels correspond largely to the bonding and antibonding x molecular orbitals I x,, and 1 xIIrrespectively, of the Nz molecule in Figure 3. The 2e and 3e levels possess mainly metal character, as d o the t b and 2 b levels. and of the N-N bonds The strengths of the M-N-N-M thus depend chiefly on the occupancy of the e levels. Four electrons of the two N atoms fill the 1 e level. This possesses bonding character for the N atoms; owing to its partial metal character, however, a weaker N-N bond results than in the free Nr molecule. The progressive occupation of higher levek with the 12d electronsofthe two Ru" centers ( M = M ' ) leads to a marked weakening of the N-N bond in the 2e level, as the orbitals are antibonding with respect to the N-N bond. The filling of the I b and 2 b levels leaves the N-N bond unaffected, while the occupancy of the 3e level strengthens the N-N bond since the orbitals are bonding with respect to the N atoms. Altogether there are thus five bonding filled orbitals-the bonding character of the filled M-N-N-M CT orbital must of course also be taken into account here-as against two antibonding filled orbitals with respect to the N-N bond: there is therefore hardly any difference between the N z bonding in [ I R u ( N H ~2Nr]40 )~~ and that in [Ru(NH,)jN,]'@. However, if the metal atoms d o not possess sufficient electrons to fill the 2 b and especially the 3c levels, a much reduced v x 2 frequency is observed compared to the mononuclear complex [ReCl(N2)(PMe2Ph)4] ( v y 2 = 1925 cm-I); examples include [ReCl(PMe,Ph)4-NrCrC13(THF)2]( v N ~ =1875cm- I ) , in which the Re' and Cr"' centers can contribute a maximum of nine electrons, and [ReC1(PMe~Ph)-NN-TaCIs] ( V Y ? = 1695),in which the metal atoms can contribute only six electrons for occupation of the levels. This effect is particularly well illustrated in [ReCl(PMe2Ph)4N2-MoC14(OMe)]. This complex, containing one more electron, exhibits a V V ? frequency of 1660cm-'. In accordance with the low V N ? frequency, X-ray structure analysis shows the long N-N distance of 1.21 A for the Re-N-N-Mo unit 1' 7hl. Figure 5 also illustrates the difficulty of reducing the N, unit in such complexes. The electrons taken up first fill the 2 b and 3e levels and thereby strengthen the N r bond. This is clearly no longer the case when a lowering of the fourfold symmetry resolves the degeneracy of the e levels. Such may be the case in the Fe and Ti complexes mentioned in Section 5.4. Most of the N z complexes isolated so far obey the inert gas rule and are diamagnetic. Exceptions include [ C O N A P P ~ ~and ) ~ ] [ { ( C s H ~ ) z T i i ~ N las ] , well as adducts of Lewis acids to [ReCI( N ,)( PMe zPh)J]. 5. Chemical Reactions of Dinitrogen Complexes increasing thermal lability of the N2 complex; the residual coordinatively unsaturated complexes can be stabilized by the addition of other ligands, r . ~HzO, . NHJ, pyridine, PPh3, or solvent molecules. In the absence of such donors, the resultingcomplexes are frequently suitable as highly reactive catalysts for the polymerization of olefins. These Nz complexes thus bear some resemblance to aliphatic diazo compounds which yield the reactive carbenes on loss of Nz. 5.1. Oxidation N 2 complexes are particularly sensitive to oxidizing agents. Strong oxidizing agents are therefore frequently used for the quantitative determination of NZIh8j. If the N2 complexes are very stable they can sometimes be oxidized by one unit without loss of the N z 1igandl''l: The oxidized complexes are less stable than the starting compounds, in agreement with the increase of 80-100cm-' in the vx2 frequency which indicates a weakened M-N bond. Some complexes undergo reversible electrochemical oxidation, 0.9.the [ ( N H ~ ) ~ R U - N ~ - - O S ( N H ~ ) S ] ~ ion ' (0.I V, rotating platinum electrode) to the ion with a fivefold positive charge[")l. Generally, however, the oxidized complexes undergo rapid secondary reactions with loss of the N 2 ligand. 5.2. Displacement or Exchange Reactions Very stable N z complexes can undergo displacement reactions in which the M-N, unit is retained. These include the diazotization of the exceptionally stable [Os(NH.3)sN2]" ion to the [ O S ( N H & ( N ~ ) ~ ] ~ion[321. ' (The [ O S ( N H ~ ) ~ N ~ion ]~' is so stable that it resists several hours' boiling in conc. HCI.) The Re--N, unit in [ReCI(N,)(PMe,Ph),] is also very stable and is still retained on the displacement of all the phosphane ligands" 81. More numerous, however,are the reactions resultingin displacement of the N, ligand. Among them. the reversible exchange reactions of the N r ligand with Hz and water [eqs. (7) and (8)respectively] are of significance for the course of N2 assimilation. Ammonia too-the final stage of N 2 assimilation --can displace the Nz group in dinitrogen complexes, sometimes even reversibly: [ R L I ~ N H . J ) - N ~ ] ' "+ N H , The discovery of the [ ( N H J ) ~ R U N ~ ] complex " nurtured the hope that a pathway for definite reduction of the N r molecule under mild conditions had been found, a hope that was not at first fulfilled. Attempts to reduce the complex-bound N2 ligand usually results in its liberation. This reaction becomes easier with Anquw. Chrm. internal. Edit. 1 Vol. 13 ( 1 9 7 4 ) f No. 10 + [ C O H ( N L ) I P P ~ J+~ ]N H J [ C O H ( N H . ~ ) I P P ~ . % IN ~ ]I + [ R U ( N H ~ ) ( , ]+ ' ~ Nz (19)1-"hl (20) The exchange reactions of the Ru system have been very thoroughly studied, especially by thermochemical methods. The heat of reaction A H 7 - 18.350.9kcal/mol found for eq. (8) clearly indicates the strong tendency to form the [Ru(NH3)5N2I2' ion. The greater stability of the analogous CO compound is again evident from the heat of reaction['": 645 + [ R U ( N H ~ ) S H ~ O ] ~CO " A H = -36.1 ? 1.6 kcalirnol [ R u I N H ~ ) s C O ] ~ *+ H 2 0 terized, they certainly contain an N-N unit. Solvolysis of these complexes results in evolution of N2 and in partial reduction of the N 2 ligand to hydrazine and ammonia. Thus Furthermore, the N2 ligand in [Ru(NH3)5Nz12@can rotate a red complex isolated from the (PPh3)2FeC1s/isoin the complex, the metal-bound and the terminal N atoms C3H7MgC1/Nz/ether system has been postulated to have the interchanging places. This is deduced from the isomerization structure: of [ ( N H ~ ) S R U - ~ ~ N S ~ Nto] *[ @ (NH~)~RU-'~N='~N]~@, which proceeds at 25°C in aqueous solution with a half-life OEtz OEtz I I of ca. 2 hand is approximately 45 times faster than the exchange (Ph3P)zF I e-N- N-F e( P P h , ) reaction with H z O according to eq. (8). Thus isomerization H proceeds without dissociation of the N 2 Iigand; the dihapto structure (2) of the M-Nz group in Scheme 1 is postulated (If this structure is correct then the complex does not possess as a transition state1"]. However, recent studies of the Ru-N fourfold symmetry, in contrast to the Ru and Re complexes cast doubt upon this hypothesis, since the basic discussed in Section 4.2.) Solvolysis of this complex with assignment of the VR"-N vibration to the Ru-N2 unit could HCl/ether at -50°C yields 10% of hydrazine alongside be wrong. Monohapto-dihapto bonding isomerism for the N2 decomposition products and N21421. ligand was recently demonstrated by "N-NMR and IR specA deep blue complex of formula [{(C5H5)2Ti}2Nz], for which troscopy in [(C5Me5)2TiNz]at -61 oC172b! structure ( S a ) in Scheme 1 is postulated, can be isolated + 121) 5.3. Lewis Base Reactions As explained in Section 4.2, the terminal N atom in the M-N-N unit is probably negatively polarized. Mononucleat N Zcomplexes can therefore react as Lewis bases. This leads to symmetrical N z complexes [ I N H ~ ) ~ R u N z ] "+ [ ( N H ~ ) S R U I H ~ O ) + ]~" [ ( N H J ) ~ R u - N ~ - R u ( N H ~ ) ~+] H ~ ~2 0 (22) AH = - 6.7 kcal/rnol from the (C,H,),TiCI/CH,MgI/N, system. Solvolysis of this complex with methanolic HCl yields mainly dinitrogen; however, hydrazine and ammonia also apbear as minor product S[39*'. While these experiments show that it is possible in principle to reduce complexed dinitrogen, they have the disadvantage that with the compounds mentioned it is not possible to convert a definite Nz complex into a definite N,H, complex ( x = l or 2, y = 1, 2, 3, or 4). This was first accomplished by the reaction of well-defined bis-(dinitrogen) complexes of molybdenum and tungsten with concentrated HC11741: as well as asymmetric N Z complexes: [ ( N H ~ ) ~ R U N ~+ ] "[ I N H ~ ) J O S I H ~ ~ + )]~" [ I N H J ) ~ R u - N ~ - O S ( N H ~ ) ~ ]+~ "H 2 0 [(PMe2Ph)aCIReN2] + [C~CIIITHF),] - [(PMe,Ph),CIRe--N2---CrCIl(THF)2] + TH F (23) (24) According to eq. (24) a series of asymmetric N2 complexes can be prepared in which the CrCl,(THF), grouping is replaced by TiCI,(THF),, PF,, AlEt,, TaCI,, NbCI,, and many other Lewis acids'401. In principle, the same reactions are observed for N2-bridged complexes as for terminal N2 complexes. As a further reaction type dissociation can yield terminal N 2 complexes, e. g . according to eq. (25): One N 2 ligand is eliminated, the central metal is oxidized, and the other N z ligand is reduced to an N2H2 moiety. The authors favor a diimine complex of the type H\ M-N-N, H for the M-NzH2 group. However, IR and 'H-NMR spectroscopic data d o not rule out a metal hydrazido structure M=N-NH,[*~]. The formation of N-C bonds in the reaction of N 2 complexes withe. g . acyl chlorides had been observed previously[z0b-'Odl. A metal-hydrazido structure has been confirmed for [W(N*H2)Cl(diphos)2]BPh4 by X-ray structure analysis. The observed relatively short N-N distance of 1.37 suggests bond as in partial double bond character of the M--N-N [W2N-.-NH2]@ 1831, A 5.4. Reduction As mentioned at the beginning of Section 5 , most attempted reductions of N z complexes result in a loss of the N z unit. However, this is not always the case: [CoN,(PEt,Ph),], for instance, can be reduced to an anionic N, complex : [CoNdPEt2Ph),] + Na/Hg 4 Na[N2Co(PE12Ph)i] (26) Neither loss nor reduction of the N 2 ligand occur in this reaction. Greater interest attaches to the reactions of some complexes isolated as solids from nonaqueous systems of the ZieglerNatta type. Although they have not yet been definitely charac646 6. Dinitrogen Complexes and Other Potential Intermediates of N z Assimilation Coordination of dinitrogen to a metal was suspected to be the decisive step in N 2 assimilation long before the isolation of active nitrogenase extracts from natural sources and the synthesis of stable N2 complexes. Biochemical studies have contributed greatly to our understanding of N2 assimilation, but it has not been possible to isolate any intermediates. Even today, all we know for certain is that the process Angew. Chem. infernat. Edit. / Vol. 13 ( 1 9 7 4 ) / No. 10 starts with atmospheric nitrogen and yields ammonia. Recent years have seen the synthesis of model substances which enable the chemist to develop precise and experimentally verifiable concepts concerning the reduction of dinitrogen to ammonia. the reduced forms of the N 2 molecule possibly existing in deprotonated form, e. g. diimine as monoanion [:N=NHI0. Which of the steps postulated in the scheme have so far been verified in vitru? It is unlikely that the N2 molecule takes up six electrons and six protons and decomposes to ammonia in a single step; a stepwise reduction is much more probable. Study of the intermediates therefore acquires considerable significance because such information is indispensable for the simulation of N2 assimilation in vitru and for the development of technical catalysts for reduction of gaseous dinitrogen, e. g. to hydrazine under normal conditions. 1) Coordination of gaseous dinitrogen under physiological conditions is possible [ e . g. eqs. (7)-( lo)]. In the complexes isolated so far the dinitrogen is invariably bound in the end-on and never in the side-on mode. 2) Displacement of the end-product NH3 by Nz can be reproduced e. g. according to eq. (1 9). A series of mechanisms has been proposed in recent years for the reduction of dinitrogen with nitrogenase~['~!In accordance with biochemical data, the most likely alternatives postulate two-electron reduction steps and unaminously assume that the dinitrogen is reduced to ammonia via diimine and hydrazine (Scheme 2) 4) In Scheme 2, diimine complexes are postulated as intermediate stages. Until recently diimine was only known as an unstable intermediate, e. g. in organic hydrogenations with hydrazine, or as the decomposition product of HN3, N 2 H 4 or alkali metal tosylhydrazides at low temperatures (ca. - 196°C)~77-80!Lately, however, it has been stabilized under normal conditions by complexation in [transN ~ H z { C ~ H ~ M ~ ( Cand O ) [cis-NzH~{Cr(C0)~}~]. ~}~] 1 H\ L .M;N-N;( - Nli -+ H Ic L,M-NH~ + 3) Hydrazine complexes are well known. In addition, hydrazine is formed in the reduction of gaseous nitrogen with V2' salts in alkaline solution[76' and by the hydrolysis of the Fe-N2 and Ti-Nz complexes mentioned in Section 5.4. The most conclusive argument for hydrazine as an intermediate, however, is probably the synthesis of the [MCI z(N2Hz)(dipho~)2] (M = Mo, W) complexes according to eq. (27). / These complexes are formed by the oxidation of hydrazine complexes'81~821: H M'L,) H H~N-(M'L,) 4 NH, Scheme 2. Intermediates of N2 reduction, greatly simplified According to this scheme, the first step in assimilation involves coordination of dinitrogen to one or two metal centers (the actual number has not yet been established). They may be the same or different (e. g. M = M' = M o or M = Mo, M'= Fe) and in the resting phase, z.e. in the absence of dinitrogen, they probably exist as aquo complexes. Presumably, the oxidation state of the metal centers changes during reduction of the dinitrogen, e. g. L,M" + L , M ' o r L,M" The trans and cis structures of the diimine in the manganese and chromium complexes respectively are readily deduced from their IR spectra. The IR spectrum of [cisN2H2{Cr(C0)5)2 1 is particularly clear. Since the typical absorptions of the Cr(C0)s groups are confined to the 21CK1800 and 800-350cm- ' regions, bands outside these regions can be safely assigned to the N2H2 ligand vibrations. From group theory considerations, three IR-active vibrations v,?(NH), G,,(HNNH), and r(HNNH) are anticipated for trunsN,H,, but five IR-active vibrations for.cis-diimine [v,, and v,(NH), 6,- and F,(HNNH), and v(N=N)] 40r'-7qJ 20 0 4000 3500 3000 limabsi 2500 2000 2000 - 1800 1600 1400 1200 1000 800 600 600 400 0 LI [cm-11 Figure 6. IR spectra (KBr) of [NLHI{CT(CO),)~],_..[ N 2 D z ( ( C r ( C 0 ) ~ ) , ] .and ["N2H2{Cr(COs)2] (only those regions that change compared with the spectrum of the N,H, complex). Angew. Chem. infernat. Edit. / Val. 13 ( 1 9 7 4 ) N o . I0 647 A glance at the IR spectrum of [N2H2{Cr(C0)5)2](Fig. 6) immediately shows that in the regions involved (4000-2100 and 1800--800cm-') there are five absorptions, which in itself points to a cis structure for N ~ H zDeuterium . and "Nlabeling confirm that the absorptions are in fact due to N z H 2 vibrations and allow assignment of the absorption to vibrational forms of the diirnine. Thus, it is seen that e.y. the absorptionat 1415cm-' canonly bedue to the N-N stretching vibration, which, however, might be coupled to the Cr-N stretching vibrations[841. What is extremely surprising in the synthesis of the diimine complexes is the fact that the tungsten-diimine complex also occurs in the cis form, although it is best prepared from the mononuclear hydrazine [lCO),WN,H,] + H,OL Cuzo THF Na,SO, O'C 141 a ) International Union of Pure a n d Applied Chemistry: Nomenclature of Inorganic Chemistry, Butterworths, London 1970: b) K . Jorius, Angew. Chem. 85. 1051 (1973): Angew. ('hem. internat. Edlt. 12. 997 (1973): C. Ki-iigcrand Y - H f i u I , Angew. Chem. 8 5 . 105 I (1973):Angew. Chem. internat. Edit 12, 998 (1973) [5] G. C. Dohiriaon. R. Muson. C. B. Roherrsoii, R. L:go. F . Corifi, D. Monrlii, S. Ciwini. a n d F . Bor~uti,Chem. Commun. lY67. 739 161 M.: H . Knoth. J. Amer. Chem. SOC. 88, 935 (1966). [7] J . K . Biirdert, M . A. Gruhuni. and J. J . 7iirncr. J. C. S Dalton Trans. 1972. 1620. [8] H. Huhrr. E. P. Kurirlig, M. Moskorits, a n d G. A. O m . J . Amer Chem. Soc. Y.5. 332 ( 1 973). 191 A. J . Ri,.\i, J. Organometal. Chem. 40. C 7 6 (1972). [ 101 D. .Si,llmurin and C. Mor.se/, Z. Naturforsch. 27 h, 465 ( 1972). [I I ] D. S~/J?ILI~IJI and G Alui.srl. Z. Naturforsch. 27h. 718 (1972). [I21 M . Hidui, K . Timiiiuri, Y C'ihirlu, a n d A . Miwrio, Chem. Commun. 1969. 1392: 7 A. Giwrgi, a n d C. D. Srrhold, Inorg. Chem. 13. 2544, 2548 (1973). [c~s-NLH, /W(CO),/.,] (30) +by-products This could signify that in the complex cis-diimine is thermodynamically more stable than trans-diimine. A decision as to which of the two isomers is more stable in the free state has so far been impossible, both experimentally and by calculation[8h].The preferential formation of the cis-diimine complexes in the case of chromium and tungsten gains importance by the fact that reduction of substrates by nitrogenases most probably also proceeds stereospecifically in the cis position: thus, the reduction ofC,D, yields exclusively cis-deuterioethylene. As, furthermore, the diimine complexes undergo redox reactions -under mild conditions in which N2, N2H4, and NH3complexes are formed, they are suitable models for studying the intermediate stages in Nr assimilation; just as the likely synchronous abstraction of two H atoms converts the binuclear chromium-hydrazine complex into the diimine complex, so the synchronous addition of two hydrogen atoms to a binuclear dinitrogen complex could reduce the latter to a cis-diimine complex. 7. Outlook for the Future The first seven years of N z complex chemistry were marked by the search for new N z complexes and the failure to reduce the dinitrogen bound in them. Very recently a new development has begun to emerge. Now that it has been demonstrated experimentally that complex-bound dinitrogen can be reduced under relatively mild conditions and all the reduction states of the N z molecule have been identified, the prospects of finding a catalyst system allowing in vitro reproduction of the processes occurring In N 2 assimilation under mild conditions appear brighter than ever before. [I,] M . Arc,stu and A. S u ( c o , Garz. Chim. Ital. 102. 755 (1972)- [I41 M . L. H. G r ( w a n d W E . S i l w r t h o r n , J. C. S. Dalton Trans. lY73, 30 I. [ 151 B. Bcll. J C1iuii. a n d G. J Lriglr, Chem. Cornmun. iY70, 842. [I61 D. Si4lrnuriii, Angew. Chem. 83. 1017 (1971): Angcw. Chem. internat. Edit. 10. 919 (1971) [I71 D. Sdlmorin. J. Organometal. Chem. 36, C27 (1972). [I81 J. Cllrrft.J . R. Dihwrth, a n d G J. Leigh. Chcm. Commun. 1Y69, 687: cf. also M . E. EOlj a n d A . P Gin.\h(n~, J. Amer. Chem. SOC. Y5, 2042 ( 1973) [I91 J . Cliutt, J. R. Diiworth, a n d G J . Leigh. J. Orgmometal. Chem. 21, P49 (1970) [20] a ) J. Chutt. J. R. Diiiwrrh. H . P. Gitnz, G. J. Li,igh, a n d J . R. Sunrlvrs. Chem. C o m m u n . lY70. 90; b ) J . Cllurt, J . R. Dilrvorrh, a n d G. J Leigh. J . C . S. Dalton T r a n s 1973, 612: c ) J. Chutr, G. A. Hrufh, a n d G. J . Lrigli, J . C. S. Chem. Comm. 3972. 444; d j J. Organometal. Chem. 57, C 6 7 (1973). [21] A Suiio a n d M . Arcsro, Chem. C o m m u n . lY(i8, 1223 [22] G. M B u i r u ~ ) f trM. . J. Muj.a. a n d B E. Prutrr. Cheni. C o m m u n . IY6Y. 5x9. [23] W H. Kriorh, J Amer. Chem. Soc. YO, 7172 ( 1968). [24] P. G. Doiiglri.~,R D. Fdt/iurti. a n d H. G. Mrrzger. Chem. C o m m u n . lY70. 889. [25] A. D. Allcri. F . Bortoriilc!, R 0. Hurri\, S r n o f f , J. Amcr. Chcm. Soc. KY. 5595 (1967). V P Reimulu, a n d C. 1.: [26] L. A . P. Kurie-Mugiiire, P. F . Shrriiluri. F. Busolo, and R G. Prurson, J. Amer. Chem. SOC.YO, 5295 (1968). [27] Y. G. Borodko, A. K . Shiioiw. and A. E . Shilor, Dokl. Akad Nauk SSSR 176, 1297 (1967). [2X] B. 5~11,J . Churt, a n d C. J . Leigh, Chem Commun. lY70, 576. [29] J . Cliufr. G. J. Leigh, and R. L. Richurds, J. Chem. Soc. A 1970, 2243. [30] J . Chorr. D. P Melri1le. a n d R. L. Richariis, J Chem. SOC. A 1Y71, 895 [31] A D. Allrri a n d J. R. Srrrrris, Chcm. C o m m u n . 1967. 1147. [32] H. A. Schrir/cygi,r, J . N . A r m o r , and 11. Tiiiihe, J Amer. Chem. SOC. YO. 3263 ( 1968). [33] G. Sp&r a n d /.. M u r k o , lnorg Chim. Acta 3. I26 (1969). [34] a ) A. Suwo a n d M. R&sr, Chem. Commun lY6Y. 471 : b) A. Yumurnoro. Kuu:iiiiii,, L. S f i r . a n d S. Ikedu. ihrd lY67, 73. S. [2] A. D. .4//rri and C. V Si~iio//, Chem. C o m m u n . 1Y65. 621. [35] M . Arrstrr, C. F . Nohili,, M . R o . w a n d A. Sulco, Chem. Cornmun. IY71. 781. [36] L. Y Ukhiri. A . Y Shi~rrsor,a n d M. L. Khirlrkr1, Isv. Akad Nauk SSSR, Ser. Khim lY67. 957 [37] J . 1'. Co//miri, M . Kiiboru, F . D Vustine, J . Y Sun, a n d J. CV K u n g . J. Amer. Chem. SOC.YO. 5430 (1968). [38] S. C. Srirusrui~ua n d M. Bigorgne, J. Organometal. Chem. I # , P30 1 1969) [39] a ) I'u G. Borodko, / N . IrleIu. L M. Kuchupiria, S. 1. S u h z h o . A. K Shiloca, a n d A E Shilov, J. C . S. Chem. Comm. IY72. I17X: b) J. E. Bercuw. R. H Murrii-/I, L. C. Brll, a n d H. H . Bririt:ingrr, J. Amer. Chem SOC. 94, 1219 (1972): c) E . €. IWI Turnelm,W Crcrnei.. N . Klorntschi, a n d J . S. Miller, J. C . S. Chem. Comm. IY72, 481; d j cf. also J . H . Ewhrn, J Organometal. Chem. 57, 159 (1973). [40] J . Churi. J. R. Dilnorth, G. J . Leigh. and R. L. Richurds, Chcm. Cornmun. IY70, 955: cf. also J Churr, R. 11. Cruhrrw, E . A. J r f f r r i . a n d R. L. Rii.hurds. J. C. S. Dalton Trans. 1973, 1167. [3] H . Borreis. Arch. Mikrobiol. I . 333 (1930). [41] W. E. Siicrrrhorn. Chem. C o m m u n . IY71. 1310 Received. May 23. 1973 Supplemented: December 14, 1973, March 18, 1974, a n d June 19. 1974 [A 1000 I€] G e r m a n version: Angew. Chem. 56.692 (1974) Translated by Express Translation Service, London [ I ] Selection of earlier reviews: a ) A. D. A l l m . R. 0. Harris, B. R. Lor.s<hrr. J . R Ster-cri.\, a n d R. N . W / l i t r / < , j ~Chem. , Rev. 73, I I (1973): b) J. Churr a n d G J. LcrgIi, Chem Soc. Rev. 1 , 121 (1972). c) J . Chutr a n d R. L. Richards in J . R. Postgurr- T h e Chemistry and Biochemistry of Nitrogen Fixation. Plenum Press. London 1971, p 57: d j G. Henrici-Olirc' a n d S O/rw< Angew. Chem. # I . 679 { 1969): Angew. Chem. internat. Edit. X, 650 (1969): e ) Yu C; Borodko a n d A . E. Shrlor, Russ. Chem. Rev. 38, 355 (19691. 648 Angew. Chem. infernaf. Edit. / Vol. 13 (1974 j 1 No. 10 [42] Yu G. Borodko. M . 0. BroUman, L . M . Kachaplna, A . E . Shilot, and L . Yu. Ukhin, Chem. Commun. 1971, 1185. [43] 0 . F. Ifarrison, E. Weisshrryrr, and H . Taube, Science 159, 320 (1968). [44] C. Creutz and H . Tauhe, lnorg. Chem. I @ , 2664 (1971). [45] A . D. Allen, Section Lecture, XIII'h Intern. Con[. Coord. Chem., Zakopane 1970. 1461 R. M . Magnusson and H . Taube, J. Amer. Chem. Soc. 94, 7213 (1972). [47] P. W Jolly and K . Jonas, J. Organometal. Chem. 33, 109 (1971). [48] Tables of Interatomic Distances etc., Special Publications No. I 1 and No. 18 of the Chemical Society, London 1958, 1965. 1491 F. Borfomley and S. C. Nyhurg. Acta Crystallogr. B 24, 1289 (1968). [50] J . E. Fwgu.\.son, J L. L o w , and W T Robinson, Inorg. Chem. 1 1 , I662 ( I 972). [51] B. R. D a i s and J . A . Ibers, Inorg. Chem. 9, 2768 (1970) [52] B R. Daris and J . A Ibers, Inorg. Chem. 10, 578 (1971). 1531 B . R. Ducis, N. C. Poyne, and J . A . Ibers, Inorg. Chem. 8, 2719 (1969). [54] T Cichida, E Cchida, M . Hidai, and T Kodomo, Bull. Chem Soc. Jap. 44. 2883 (1971). [55] J . M . Treitel, M . T Flood, R . E . March, and H . B. Gr aj , J. Amer. Chem. SOC.91. 6512 11969). [56] R. Nast and H. Kohl, Chem Ber. 97,207 (1964). [ 5 7 ] C . Hrrzherg Molecular Spectra and Molecular Structure 1. 2nd Edit. van Nostrand, Inc.. Princeton 1955. p 551. [58] M . A . I . A/-Johourr, 0. P. May, and D . W Xirner, J. Chem. SOC. 1965, 616: D W Turner and D . P . M a y , J . Chem. Phys. 45, 471 (1966). [59] R. S. M u l l i k m , Can. J. Chem. 36, 10 (1958). [60] C. Edmisron and K . Ruedmhrrg. J. Chem. Phys. 43, S97 (1965). [61] K . G. Cauitoti, R. L. D e Kock, and R . f Fenske, J Amer. Chem Soc. 92, 5 I 5 ( 1970). [62] G. J . Lpigh, J . N . Murrrl, W Brrmser,and W G. Procror, Chem. Commun. 1970. 1661. [63] P. Finn and W L. Jolly, Inorg. Chem. 1 1 , 1434 (1972). [64] J . Chart, D. P. Melrilli,, and R. L . Richards, J Chem. Soc. A 1969. 2841. [65] A . D. Allen, 1 Eliades. R. 0. Harris. and !4 P. Rrinsalir, Can. J. Chem. 4 7 . 1605 11969). [66] D. J . Darensboirr.g, Inorg. Chem. 10. 2399 (1971). 1671 a ) J . Charr. R . C. Fay, and R. L. Ridiard.\. J. Chcm. Soc. 4 1Y71. 702, b) M . M e r c e r . R . H . Crabtree. and R L . Rirliards. J. C. S. Chem IY73.XO8. [6R] D. E. H o r r i s o ~ iand H . Tairhe. J Amer. Chem. SOC. XY. 5706 (1967). [69] J Chart, C. J . Lrigh, and R . L. Ricliurd\. J. Chem. Soc. A IY70, 2243. [70] a ) C. M . Elson, J . Gulms. and J . A . Page. Can. J . Chem. 4Y. 207 (1971); b) A . Yamumoto, S. Kota:irrrie, L. S. Pu. and S. lkcdu. J. Amer. Chem. Soc. 89, 3071 (1967). [71] J N. Armor and H . Tairhc,, J. Amer. Chem. SOC.YZ, 2560 (1970). 1721 a ) M . W Bee. S. F. A . K e r r k , and D. B Poiwii. J. C. S. Chem. Comm. 1972. 767; b) J . E . Bn.cmt. E . Rosenhrrg, and J . D. Roberts. J. Amcr. Chcm SOC.96, 612 (1974). [73] G. D. Wart, J. Amer. Chem. Soc. 94, 7351 (1972). [74] J . Chart, G . 4 . H r o i h , and R. L. Riiliurds. J. C. S . ('hem. Comm. 1972, 1010. [75] Cf. [ic], pp. 89, 90, and 101 as well as [ I b]. [76] A . Shiloc, N . Denisor. 0. Eliirior, N. S l i i r r u l o ~ .N. Shiri u l o i ~ i .and A. Shilow, Nature 231, 460 (1971): cf. also G . N. S(.hruir:er, P. A. Doviriwij~. R. H . Frazier, and G . W K i , J . Amer. Chem. Soc. 94, 7378 (1972). [77] S N . Forirr and R. L. Hud.>on. J. Chem. Phys. ZX, 719 (1958). [78] K. Rosengren and G. C Pinienfel. J . Chem. Phys. 43. 507 (1965). [79] A . Fomberri. Can. J. Phys. 46, 1005 (1968). [80] N . Wihrrg, H . Bat.hhirhrr, and G. Fis<bcr, Angew. Chem. 84, 8x9 (1972): Angew. Chem. internat. Edit. I I , 829 (1972). [ X I ] D. Sellnmtln, J. Organometal. Chem. 44, C 4 6 (1972). Et&I/. J . Organomctal. Chcni. 4Y. C 22 [82] D. Sellmarin, A. Brand!, and R . ( 1973). [83] G. A. H ~ a f h R. , M u s o ~ i ,and K . M. Thoniir, J. Amer Chcm Soc 96, 259 ( I 974). [84] D. Sellmann, A . Brundl, and R . Endell, Angew. Chem. 85. 1122 (1973): Angew. c h e m . internat. Edit. 12, 1019 (1973). I851 D. Sellniann, A . Brondl, and R. Endell. Angew Chem. 85, 1121 (1973). Angew. Chem internat. Edit. 12, 1019 (1973) [86] Cf. J . A l s f r r and L . A . B i m e i i r . J Amcr. Chcm. Soc. 84. 1261 (1967). L. J . Schoad and H . B. Kiiiso., J. Phys. Chem. 73. 1901 (1969): L. R~~duri. W J . Hehre, and J A . Pople. J. Amer. Chem. Soc. 93. 2x9 (1971) The Helicenes By Richard Henri Martin[*] "Helicene" is the name introduce1 by Newman in 1955, to describe the benzologues of phenanthrene in which the extra ortho-condensed rings give rise to a (regular) cylindrical helix. The pioneer work of Newman in this field cannot be overemphasized; his brillant synthesis and resolution of [6]helicene, achieved eighteen years ago, will remain as a landmark, for it opened the way to the study of a fascinating class of synthetic molecules. In the following review, an attempt is made to summarize the present state of our knowledge in this rapidly expanding field. 1. Introduction compounds is due to the unique combination of these three properties in a single molecule. The helicenes are characterized by a helical structure made up of ortho-condensed aromatic rings, by the presence of a powerful inherently chiral chromophore, and by the possibility of interactions ( e . g . electronic interactions) between overlapping aromatic rings. The scientific interest raised by these We shall deal first with the nomenclature of these compounds. The "class name" is "helicene"; "carbohelicenes" contain only carbon atoms in the skeleton, "heterohelicenes" at least one hetero-aromatic ring. In this review helicenes that are made up of benzene rings only are referred to as "all-benzenehelicenes"[**]."Double helicenes" are helicenes containing ['I Editorial nore: The expression "benro-heliccnes" is unsuitablc. sincc thc prefix "benzo" denotes, according to I U P A C rule A-21 4. the annelation of ;I benzene ring The expressions "benzoid helicenes" or "henzenoid heliccncs" could be misunderstood for the terms "benzoid" and "benzenoid" are ~ i s u a l l ~ used in the sense of "benrene-like" andlor "aromatic". [**I Prof. R H. Martin D. Phil. Service d e Chimie Organique. Fac. Sc. Uriiversite Libre de Bruxelles Av. F. D. Roosevelt, 50 8-1050 Briixelles (Belgium) Angew. Chem. internat. Edit. Vol. 13 (l974) 1 No. 10 649


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There is this little spot where the wind always whispers to me when I am in most need of wisdom. Not far from my home, on the southwest summit of Stone Mountain, I find comfort in sitting upon a rock under a gathering of strangely dwarfed pine trees. The view is spectacular, especially at sunset […]Read more
The Wasp and the Wind
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Sony Xperia S is been SELLING LIKE "HOTCAKE" in UK & EUROPEAN MARKETS!!!! It's a CHAMPION Smartphone so far....!!!! Keep in Mind ultimate Sony Hyabussa & Mint are coming later this year - 2012!!!!
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action kamen #1, 07 Apr 2012Just purchased this phone 48 hours ago, I wonder what accesories from SONY they have... ... moreYour review is honest. Could you please tell me what are the major differences you have found between iOS and android... I never have used an apple product. :-)
cherub, 30 Mar 2012good fone to try .........if it has MC slot and minimum SAR value for physical health.
High S... moreHi,
what U mean by SAR???
may i know that sony xperia LT 26U having outlook synchronise facilities available or not?
[deleted post]Dear Andy...
It Works in Silent Mode
This is what he said about the
Ola Lilja Molén, Sony Mobile Communication head of Southeast Asia markets.
"It features the iconic design including the transparent element encircling the base of the phone that illuminates when receiving calls, texts and notifications."
But I think the transparent element is not working like what HE said, right? I really love it if it does like this, perhaps on ICS update?
Anonymous, 06 Apr 2012i hv used dis phone but i am confused shud i buy dis or wait for samsung galaxy nexus n galaxys3wait for samsung
action kamen #1, 07 Apr 2012Just purchased this phone 48 hours ago, I wonder what accesories from SONY they have... ... moreA good smartphone...!


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Peer reviewed
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ERIC Number: EJ929454
Record Type: Journal
Publication Date: 2008
Pages: 16
Abstractor: As Provided
Reference Count: 35
Sibling Outcomes from a Randomized Trial of Evidence-Based Treatments with Substance Abusing Juvenile Offenders
Rowland, Melisa D.; Chapman, Jason E.; Henggeler, Scott W.
Journal of Child & Adolescent Substance Abuse, v17 n3 p11-26 2008
This study examined the substance use and delinquency outcomes for the nearest age siblings of substance abusing and delinquent adolescents that participated in a randomized clinical trial evaluating the effectiveness of integrating evidence-based practices into juvenile drug court. The sample of 70 siblings averaged 14.4 years of age, 50% were male, 71% were African-American, and 27% were white. Measures of sibling substance use and delinquency were collected at four points in time (i.e., pretreatment, 4 months, 12 months, 18 months). Multilevel Longitudinal Models were used to evaluate whether changes in sibling substance use and delinquency paralleled the treatment effects observed for their substance abusing delinquent brothers and sisters in the juvenile drug court study. Parallel sibling outcomes were obtained for substance use but not for criminal behavior, and possible reasons for the divergence in these results were discussed. The findings add meaningfully to the literature on the effects of evidence- and family-based treatments on siblings. (Contains 1 figure and 2 tables.)
Descriptors: Siblings, Delinquency, Adolescents, Substance Abuse, Outcomes of Treatment, Program Effectiveness, Crime, Youth Programs, Contingency Management, Probability, Predictor Variables
Routledge. Available from: Taylor & Francis, Ltd. 325 Chestnut Street Suite 800, Philadelphia, PA 19106. Tel: 800-354-1420; Fax: 215-625-2940; Web site: http://www.tandf.co.uk/journals
Publication Type: Journal Articles; Reports - Research
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A


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I have a gap inbetween my 2 front teeth an a twisted fang. Would you say this was a simple straightness of teeth or a more complicated.
I have had the gap all my life but would really like it closed. The twisted fang is not bothering me as much but if I could get them both done that would be ideal.
Is there a price range depending on if I just get the gap closed or will it be pretty much same price for both gap and fang. I Look forward to reading your response, Thanks
Dr Hussein Shaffie
The Sandford Dental Implant and Cosmetic Centre
306 Broadway, Bexleyheath, Kent, DA6 8AA
Web: www.thesandford.com Tel: 02083037051
Email: [email protected]


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Winner of 19 Gambero Rosso Tre Bicchieri Awards, Cantina Terlano is a wine growers' cooperative founded in 1893 in South Tyrol. Join Master Sommelier Peter Neptune for a wine dinner featuring Terlan's wines and experience one of our favorite producers in Alto Adige.
Peter Neptune is one of only 236 individuals in The World to hold the wine industry's most prestigious title: Master Sommelier. He is a 30-year veteran of the wine business, beginning as a sommelier in New York City, where he trained and worked for 10 years. Upon returning to his native California, Peter entered into the wholesale wine trade. For seventeen years he has been at California's leading fine wine wholesaler, The Henry Wine Group, where he is Senior Vice President of Corporate Training & Wine Education.


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Lebanon Begins Offshore Oil And Gas Exploration
BEIRUT, May 29 (Reuters) - Lebanon's search for its first oil and gas reserves began on Tuesday after authorities approved an exploration plan submitted by a consortium of France's Total , Italy's Eni and Russia's Novatek.
Energy and Water Minister Cesar Abi Khalil said in a televised statement that exploration started after authorities gave the go ahead on Monday. Lebanon hoped to launch a second offshore licensing round by the end of 2018 or early 2019, he said.
In February Lebanon signed its first offshore oil and gas exploration and production agreements with the Total-Eni-Novatek consortium for offshore Blocks 4 and 9.
Part of Block 9 contains waters disputed with neighbouring Israel but the consortium has said it has no plans to drill in the disputed area.
Khalil said exploration of the two blocks would last up to three years and the first well is expected to be drilled in 2019, providing all government departments grant necessary licenses and permissions "on time and without delay".
Khalil has served as energy minister since December 2016 but is currently a caretaker minister because Prime Minister-designate Saad al-Hariri has not yet formed a government after parliamentary elections on May 6.
Until drilling begins Lebanon will not know what reserves lie in its waters. Khalil said exploratory wells will be dug in the areas with the highest probability of commercially viable discoveries based on seismic studies.
(Reporting by Lisa Barrington; Editing by Mark Potter and Susan Fenton)
Generated by readers, the comments included herein do not reflect the views and opinions of Rigzone. All comments are subject to editorial review. Off-topic, inappropriate or insulting comments will be removed.


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Wandin Florist Classes
Wandin Florist workshops are designed for those that want to get straight into creating and arranging. If you share our passion for flowers then these workshops are for you. Our workshops are highly informative and suitable for beginners through to advanced floral decorators and for people of all ages and backgrounds. Class sizes are limited so it is essential to make a reservation. At the workshops you can provide your own tool kit or pre-order a kit from us, we will supply the flowers and other accessories required to complete your floral arrangement. Light snacks and refreshments will be provided, and most importantly you will be able to take your work of art home to impress your family and friends with your talent. Wandin Florists also provide workshops for large group bookings, corporate clients that have specific requirements.
Demonstrations are fun and interactive and crammed with great ideas and inspiration.
We Provide The Flowers
We prepare it all & you will be inspired by the many tips we will share with you.
All class and kit payments will be required upfront in full to secure your spot.
Our expert florists will provide general flower care instructions whilst showcasing a collection of floral displays that you can watch come together You will be inspired by the many tips we will share with you. Relax, enjoy, and get a 'behind the scenes glimpse' of our expert floral creations either in our in-house classes or of site in our workshops.
Class Mailing list:
If you would like your name on our list to ensure your spot for our next demonstration, workshop or classes email us today – firstname.lastname@example.com.
2019 Posy creations
Date : June 22nd & 29th - Saturday
Time: 11pm - 1pm
Cost: $100 per person.
Kits available fo $45
Where: Wandin Florist
Address- 384 Warburton Hwy Wandin North
Inclusions: Vase & Flowers
Refreshments & light supper providedAll equipment supplied & flowers provided**Take home your creation and a new skill!
2019 Terreriums
Date : July 13th & 20th - Saturday
Time: 11 - 1pm
Cost: $85 per person.
Glass Terrerium - can be bought to class or purchases for an additional $15
Kits available fo $45
Where:Wandin Florist
Address:384 Warburton Hwy Wandin North
Terrarium Classes - Master the art of terrarium making with two of the Yarra Valleys craftiest mini landscapers, Kim Armour & Gayle Marshall from Wandin Florist. In this fun and interactive workshop, you'll learn all about terrarium design, plant selection for both open & closed terrariums, soil composition, and terrarium care, along with some secrets for terrarium success! Everything you need to create your own unique terrarium will be provided, all you need to bring is a glass container and your imagination! All other materials will be supplied including a variety of unique ferns and indoor plants, moss, soil, rocks, plastic figurines and other items to create your terrarium.Come & get your hands dirty and join us for a fun afternoon of creating your own miniature world that will stay green all year long!


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