▁Illustr ative ▁is ▁the ▁synth esis ▁of ▁the ▁bis ( tri phen yl ph osph ine ) ▁complex ▁Fe ( CO ) 3 ( P ( C 6 H 5 ) 3 ) 2 . ▁ ▁This ▁transformation ▁can ▁be ▁accomplished ▁phot och em ically , ▁but ▁it ▁is ▁also ▁induced ▁by ▁the ▁addition ▁of ▁Na OH ▁or ▁Na B H 4 . ▁ ▁The ▁catal yst ▁attacks ▁a ▁CO ▁lig and , ▁which ▁l abil izes ▁another ▁CO ▁lig and ▁toward ▁substitution . ▁ ▁The ▁elect roph il icity ▁of ▁Fe ( CO ) 4 L ▁is ▁less ▁than ▁that ▁of ▁Fe ( CO ) 5 , ▁so ▁the ▁nucle oph il ic ▁catal yst , ▁dis eng ages ▁and ▁attacks ▁another ▁mole c ule ▁of ▁Fe ( CO ) 5 . ▁ ▁Ox id ation ▁and ▁reduction ▁Most ▁metal ▁car b ony ls ▁can ▁be ▁hal ogen ated . ▁ ▁Thus , ▁treatment ▁of ▁Fe ( CO ) 5 ▁with ▁hal og ens ▁gives ▁the ▁f err ous ▁hal ides ▁Fe ( CO ) 4 X 2 ▁for ▁X ▁= ▁I , ▁Br , ▁Cl . ▁These ▁species , ▁upon ▁he ating ▁lose ▁CO ▁to ▁give ▁the ▁f err ous ▁hal ides , ▁such ▁as ▁iron ( II ) ▁ch lor ide . ▁ ▁Red u ction ▁of ▁Fe ( CO ) 5 ▁with ▁Na ▁gives ▁Na 2 Fe ( CO ) 4 , ▁" t et rac ar b ony l fer rate " ▁also ▁called ▁Coll man ' s