SOLID-STATE STUDIES INTO THE POSSIBLE REARRANGEMENT MECHANISMS FOR THE FLUXIONAL BEHAVIOR OF THE TETRANUCLEAR CARBONYLS M4(CO)12 AND THEIR DERIVATIVES

The deformation from an idealised geometry, observed in the solid state for a given cluster species, may indicate the paths taken by the cluster in ligand fluxionality processes. A number of single-crystal X-ray structures of M4(CO)12-n(L)n clusters (M = Co, Rh, Ir; n = 1-5) have been examined in order to elucidate any geometric trends in their ligand envelope deformations. It has been revealed that the complementary geometries adopted by M4(CO)12-n(L)n species may be both metal- and ligand-dependent. Iridium species adopt T(d)-cubeoctahedral structures, but the available data provide no clear picture for the complementary geometry adopted by cobalt or rhodium species. Additionally, tripodal ligands have been shown to stabilise D3h (icosahedral) ligand polyhedra.