New carbide clusters in the cobalt sub-group. Part 5. Crystallographic characterization of deca-µ-carbonyl-carbido-octacarbonyl-polyhedro-octacobaltate(2–) in its bis(benzyltrimethylammonium) salt

Abstract

The title complex crystallizes in the triclinic space group P with unit-cell dimensions a= 19.02(2), b= 10.37(1),c= 12.81(1)Å, α= 116.43(8), β= 88.90(8), γ= 95.53(8)°, and Z= 2. The structure has been determined by conventional methods from X-ray single-crystal counter data and refined by least-squares calculations to R 0.064 for 3 539 significant diffraction intensities. The [Co₈C(CO)₁₈]^2– anion contains a deformed tetragonal antiprism of metal atoms (D₂ idealized symmetry) with an average Co–Co distance of 2.52 Å. The carbide atom occupies the centre of the cluster; two kinds of Co–C(carbide) distances are present (means 1.99 and 2.15 Å). There are eight terminal carbonyl ligands, one per metal atom, and the other ten carbonyls range from partially bent to symmetrically edge-bridging.