Quantum-chemical calculations of molybdenum chloride clusters Mo13C24, Mo13Cl26, and Mo13Cl30

Abstract

Quantum-chemical calculations of the structures and thermodynamic stabilities of isomers of molecular clusters of lower Mo chlorides Mo13Cl24, Mo13Cl26, and Mo13Cl30, as well as of the Mo13Cl26− anion of cuboctahedral or icosahedral structure, have been performed by the DFT B3LYP method with the use of the Lanl2dz basis set for the Mo atoms and the 631G(d) basis set for the Cl atoms. The highest symmetry polyhedra are considered: Mo13Cl30 and Mo13Cl24 have a structure of centered icosahedron and cuboctahedron with bridging Cl atoms sitting atop the midpoints of 30 and 24 edges, respectively. In both cases, calculations lead to a rapid increase in the Mo-Mo distance to the values that are evidence of the absence of metal-metal bonds; hence, the cluster structure, in its classical meaning, is not retained. Both the neutral cluster Mo13Cl26 and the Mo13Cl26− anion—a symmetric icosahedron, in which Cl ions sit atop the centers of 20 faces and 6 Cl atoms are terminal, and a cuboctahedron, in which 14 Cl atoms are located on the three- and fourfold axes over the centers of molybdenum faces and 12 terminal Cl atoms are located on twofold axes. For both the neutral cluster and the anion, stable structures have been obtained. In both cases, the total energies are lower for the initial icosahedral configuration.