Two tetracobalt cluster complexes: Preparation and molecular structures ofCo4(mu-dppm)(2)(mu-CO)(3)(CO)(5) and Co-4(mu-CO)(3)(CO)(6)(eta-C6H6)

The crystal and molecular structures of the title complexes (1) and (2) are described. Each contains a Co-4 tetrahedron, one face of which is edge-bri dged by three mu -CO ligands. In (1), a pair of mutually orthogonal Co-Co b onds are bridged by the two dppm (dppm = bis(diphenylphosphino)methane) lig ands. The structure of the benzene complex was determined at 153 and 300 K; as with other arene-Co-4 clusters, the eta (6)-benzene ligand sits on the apical (i.e. non-CO-bridged) Co atom.