Precursor Synthesis A series of manganese (Mn) complexes were targeted for a systematic precursor study on all-nitrogen and mixed nitrogenoxygen coordinated Mn complexes employing acetamidinate, guanidinate, formamidinate, and ß-ketoiminate ligands. While a logical variation of the coordination sphere going from all-nitrogen (acetamidinates, guanidinates and formamidinates) to mixed oxygen/nitrogen-coordination(ß-ketoiminates) helps to understand its impact on the structural features (e.g. nuclearity, bonding features) and reactivity towards potential co-reactants such as water or oxygen, the incremental but specific variation of the side-chain and backbone substitution enables the evaluation of the influence of the ligands on their physico-chemical properties (e.g. volatility) of the compounds. As a starting point, we synthesized the known but not fully characterized Mn acetamidinates Bis(N,N´diisopropylacetamidinato)manganese(II) (I) and Bis(N,N´ditertbutylacetamidinato)manganese(II) (II), slightly modifying the procedure reported by Gordon et al. . The complexes were obtained by facile salt-metathesis reaction of MnCl2 and the respective lithiated ligand in an equivalent mixture of diethylether and tetrahydrofuran. (Scheme 1) This procedure was transferred for the synthesis of the formamidinates and guanidinates (namely Bis(N,N´-diisopropylformamidinato)manganese(II) (III), Bis(N,N´-ditertbutylformamidinato)manganese(II) (IV), Bis(N,N´-diisopropyldimethylgunidinato)manganese(II) (V), Bis(N,N´-ditertbutyldimethylgunidinato)manganese(II) (VI), Bis(N,N´-ethyltertbutyldimethylgunidinato)manganese(II) (VII)). In all cases, removal of the solvent mixture was followed by extraction of the compounds (yellow to orange in color) with dichloromethane (DCM). After crystallization, the crystalline solids with yields ranging from 55 % to 87 % for compounds I to V were obtained. The attempts on the synthesis of N,N´-ditertbutyl-2dimethylamido-guanidinato)manganese(II) (VI) forwarded an insoluble orange powder. The solid may correspond to bis-(dimethylamido) manganese(II) , described as a poorly soluble Scheme 1. Schematic representation of the synthetic pathway for the targeted all-nitrogen coordinated manganese complexes. Scheme 2. Schematic representation of the synthetic pathway for the targeted mixed oxygen-nitrogen coordinated manganese ß-ketoiminate complexes. oligomer in the literature, which may have formed through sterically induced deinsertion of N,N'-di-tertbutylcarbodiimide. A low yield of 20 % obtained for the asymmetric N,N´-ethyl-tertbutyl-2-dimethylamido-guanidinato)manganese(II) (VII) supports this finding, as the steric demand is still high, but lower compared to the di-tertbutyl congener. The handling during purification and analyses of these compounds revealed an untypically high fragility against moisture and oxygen from the ambient air. The high stability and demanding reactivity of all oxygen coordinated manganese ß-diketonates and the experiences based on our previous studies on iron , cobalt , nickel , zinc and tin ß-ketoiminates, which have shown high thermal stability and appropriate reactivity towards water and oxygen as well as general promising physico-chemical precursor properties of this precursor class, motivated us to investigate the influence of a mixed oxygen nitrogen coordination sphere on the precursor properties of manganese complexes. This systematic variation of the coordination sphere from all N to mixed O/N coordination enables a comparison in terms of reactivity for both precursor classes. Consequently, four manganese ß-ketoiminates (namely Bis(4-("alkyl"amino)pent-3-en-2-onato)manganese(II) ßI-ßIV) with a systematic side chain variation (alkyl(R) = methyl, ethyl, isopropyl, tertbutyl), were additionally synthesized. Similarly, to I-VI, all these targeted Mn(II) complexes were synthesized via simple salt-metathesis reaction as shown in Scheme 2. Crystalline solids of compound ßII -ßIV could be isolated by extraction in DCM and subsequent crystallization at -30°C with appreciable yields (62 % -78 %). Only compound ßI resulted in a waxy orange solid with a lower yield of 40 % after purification. The synthesis of all the targeted complexes in this study was confirmed by elemental analysis and showed the expected elemental composition.