Covalent nature of the metal-halogen bonds in trinuclear osmium carbonyl halides

Comparison of the results of the electrochemical reduction of trinuclear osmium carbonyl halides with linear structure, Os₃(CO)₁₂X₂, and nonlinear structure, Os₃(CO)₁₀(-X)₂ (X=I, Br, and Cl) with mononuclear carbonyl halides of transition metals indicates covalent nature of the metal-halogen bonds in these compounds. Chemical dissociation does not occur upon dissolving the trinuclear osmium carbonyl halides in acetonitrile and the cleavage of the Os-X bonds is a result of the electrochemical reduction. The observed order for ease of reduction of the trinuclear osmium carbonyl halides coincides with the change in the E_1/2 values in the reduction of the mononuclear carbonyl halides of transition metals and alkyl halides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 459–460, February, 1990.