Studies in the Chemistry of Bonds between Metals. I. The Synthesis of Transition Metal Carbonyl Derivatives of Zinc and Cadmium by a Metal-Exchange Reaction

The metal-exchange reactions of a number of transition metal carbonyl derivatives of mercury of the m(2)Hg type (m = Co(CO)(4), Fe(CO)(2)C5H5, Cr(CO)(3)C5H5, Mo(CO)(3)C5H5, and W(CO)(3)C5H5) and the mixed-metal compound C5H5Fe(CO)(2)HgCo(CO)(4) with zinc and cadmium have been shown to be convenient synthetic routes to the novel zinc and cadmium analogs, m(2)Zn and m(2)Cd, and C5H5Fe(CO)(2)ZnCo(CO)(4). A polar solvent such as THF was required to promote the exchange in the case of the molybednum and tungsten derivatives. The conversion of Hg(Mn(CO)(5)](2) to Zn[Mn(CO)(5)](2) occurred in diglyme at 120 degrees. The similarity of the infrared spectra of the new zinc and cadmium compounds with those of the wellstudied mercury analogs indicated that all of the compounds contain linear arrangements of covalently bonded metal atoms. Comparison of the Mossbauer parameters with the infrared data for the M[Fe(CO)(2)C5H5](2) series (M = Zn, Cd, Hg) suggested that both sigma and pi bonding are important in the metal-metal interactions. Mass spectra, reported for the M[Co(CO)(4)](2) and M[Cr(CO)(3)C5H5](2) series, gave a qualitative indication that the metal metal bond strengths decrease in the order Zn > Cd > Hg. Detailed preparations for the mercury derivatives are described in the Experimental Section.