New carbide clusters in the cobalt subgroup. Part 17. Preparation and structural characterization of the mixed-metal octahedral dianion [Co2Rh4C(CO)13]2– as its [PPh4]+ salt

The title complex has been prepared by direct reaction of [Co3C(CO)9Cl] with [PPh4][Rh(CO)4] in the molar ratio 1 : 4 in tetrahydrofuran solution, and characterized by chemical and crystallographic methods. The anion belongs to the family of octahedral carbide-carbonyl clusters (86 valence electrons) with 13 ligands. The Co atoms are found to be contiguous with no trace of Co/Rh disorder. The ligand distribution differs from that of the analogous homometallic species [Co6C(CO)13]2– and [Rh6C(CO)13]2–. The factors controlling the ligand arrangements in the three species are discussed. The compound [PPh4]2[Co2Rh4C(CO)13] crystallizes in the triclinic space group P, with a= 13.358(3), b= 21.981(2), c= 11.526(1)Å, = 94.779(9), = 107.62(1), = 78.35(1)°, and Z= 2.6 273 Reflections were used to solve and refine the structure to R= 0.048, R= 0.058.