BIMETALLIC CO-NI CARBIDE CLUSTERS - SYNTHESIS AND CRYSTAL-STRUCTURE OF THE [CO2NI10(CO)20C]2- AND [CO3NI9(CO)20C]2- DIANIONS

The synthesis, chemical behavior and single crystal X ray structure of two new CoNi bimetallic carbide clusters, namely [Co2Ni10(CO)20C]2- and [Co3Ni9(CO)20C]2-, are reported. The first complex was isolated in ca. 30% yield among the products of the reaction of Co3(CO)9CCl with [Ni6(CO)12]2-, while the second was obtained quantitatively by reaction with protonic acids of the previously reported [Co3Ni9(CO)20C]3-. The two compounds are isostructural and show a metal frame which can be regarded as derived by distortion of a tetra-capped triangulated dodecahedron of D2d symmetry; the statistical (Co and Ni atoms being undistinguishable) idealized symmetry of the metal frame is only D2 owing to progressive deformations toward a tetra-capped tetragonal antiprismatic geometry, which are probably related to the steric requirements of the interstitial carbide atom.