MOLECULAR-STRUCTURE AND CRYSTAL ORGANIZATION OF NEUTRAL AND IONIC DERIVATIVES OF [M(4)(CO)(12)] (M=CO, RH OR IR) CLUSTERS AND A BONDING STUDY BY EXTENDED-HUCKEL CALCULATIONS

The molecular and crystal structures of neutral and ionic derivatives of [M(4)(CO)(12)] (M = Co, Rh or Ir) clusters have been studied by a combined use of molecular-orbital calculations of the extended-Huckel type and packing analysis. The problem of the existence of two structural forms, namely the 'all-terminal' structure with no bridging carbonyl ligands and the 'bridged' structure with three edge-bridging carbonyls. in the solid state has been addressed. The presence of intermolecular hydrogen bonding interactions of the C-H ... O type between carbonyl groups and the hydrogen atoms of the cations has been investigated.