Molecular structure and crystal organization of neutral and ionic derivatives of [M4(CO)12](M = Co, Rh or Ir) clusters and a bonding study by extended-Hückel calculations

Abstract

The molecular and crystal structures of neutral and ionic derivatives of [M₄(CO)₁₂](M = Co, Rh or Ir) clusters have been studied by a combined use of molecular-orbital calculations of the extended-Hückel 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.