Octahedral Metal Clusters

Abstract

THE bonding in the Mo₆Cl₈⁴⁺ and Ta₆Cl₁₂²⁺ cations, both of which contain an octahedron of metal atoms, has recently been rationalized in terms of a 40-electron model¹. The edges of the metal octahedron define the orientation of twelve bonds (type A) while the faces of the octahedron define the position of another eight (type B). In Mo₆Cl₈⁴⁺ twenty-four metal electrons fill the A orbitals and sixteen chlorine σ electrons fill type B. In Ta₆Cl₁₂²⁺ the roles of the sixteen metal and twenty-four chlorine σ electrons are interchanged. It is now possible to speculate on the occurrence of other metal octahedra if we require that this 40-electron rule be obeyed.