SYNTHESIS AND CHEMICAL BEHAVIOR OF THE 2- AND 3- DICARBIDE CLUSTERS; X-RAY CRYSTAL STRUCTURE OF 2

Article abstract of DOI:10.1016/0022-328X(85)80352-1

The synthesis and properties of the new dicarbidocarbonyl bimetallic clusters ^2- (I), ^3- (II), and ^3- (III), are described.Compound I, which is paramagnetic, has been synthesized in high yields by redox-condensation of Co3(CO)9CCl with ^2-, whereas the diamagnetic trianions II and III have been respectively obtained by reduction of I, with sodium metal in THF and sodium hydroxide in methanol.The anion I has been isolated in a crystalline state in association with several tetrasubstituted ammonium or phosphonium cations, which are characterized by elemental analysis and by a single-crystal X-ray diffraction study, of the tetraphenylphosphonium salt.The anion I has a metal frame based on a 3,4,3-C_2h stack of metal atoms, which may be regarded as derived by condensation of two either octahedral or trigonal-prismatic moieties.The resulting deca-vertices metal polyhedron encapsulates a C2 fragment showing a short C-C interatomic separation of 1.48 Angstroem.The three cobalt atoms cannot be distinguished from the remaining seven nickel atoms and are probably randomly distributed over the ten vertices.The M-M distances are scattered over the range 2.34-2.80 Angstroem, and each carbide carbon is encapsulated in a seven-vertices cage which may be described as a distorted capped trigonal prism.The carbonyl stereochemistry comprises six carbonyl groups terminally bonded to the atoms of the top and bottom triangular layers, and ten edge-bridging CO which span the ten inter-layer edges.The structure of this decanuclear dicarbide cluster is compared with those reported for related species and a rationalization is offered for the variations of the metal geometry and the C-C interatomic separation.