Metal Derivatives of Carbonyl Hydrides

The mercury compounds HgFe(CO)4 and Fe(CO)4(HgX)2 (X = C1, Br, I), which were the first representatives of non-ionic metal derivatives of iron carbonyl hydrides, were discovered by Hock and Stuhlmann (V, 36). During investigations into the preparation of cobalt carbonyls from cobalt halides under CO pressure, in the presence of another metal as a halogen acceptor, we discovered the mixed metal carbonyls M[Co(CO)4]2 (M = Zn, Cd, Hg, Sn) and M[Co(CO)4]3 (M = In, Tl) (44), e.g., 

The especially stable mercury-cobalt carbonyl, which is readily soluble in organic solvents, forms quantitatively according to the equation 

For this compound, which is closely related to the isoelectronic Hg[Fe(CO)3NO]2 (45) (Section IX) and to Hg[Mn(CO)5]2 (VII, 79), a convenient method of preparation in aqueous solution was discovered in conjunction with E. O. Fischer (46). Moreover, we could make IIg[Co(CO)4]2 react, like Co2(CO)8, with ligands either with substitution of carbon monoxide and formation of Hg[Co(CO)3L]2 (L = PR3, AsR3, SbR3), or by valence disproportionation of cobalt (VII, 80) using nitrogen bases or isonitriles, e.g., 

3 Hg[Co(CO)4]2 + 12L - 3 Hg + 2 [L6Co][Co(CO)4]2 + 8 CO Similar chemistry was observed with mercury-iron carbonyl compounds 

This type of metal carbonyl derivative has lately been the object of numerous investigations by many research groups with particular reference to metal-metal bond synthesis.3 In our laboratory the nitrosyl carbonyliron compounds R3MFe(NO)(CO)3 (M = Si, Ge, Sn, Pb R= C6H5, C4H9) have been prepared, and shown by infrared studies to have a trigonal bipyramidal structure with Cs symmetry (48). 

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