A theoretical analysis of high-nuclearity metal carbonyl clusters

Abstract

Stone's tensor surface Harmonic methodology has been applied to high-nuclearity transition-metal carbonyl cluster compounds with 13–44 metal atoms. In these close-packed metal clusters the metal atoms lie on concentric spheres and the orbital interactions can be simplified significantly if the orbitals are assigned pseudo-spherical symmetry labels. Two limiting bonding situations have been identified and represented in terms of general electron-counting rules. If the radial bonding effects predominate the clusters are characterized by 12n_s+Δ_i valence electrons, where n_s is the number of surface atoms and Δ_i is the characteristic electron count of the interstitial moiety. If radial and tangential bonding effects are important then the total number of valence electrons is 12n_s+ 2(S_s+S_i– 1), where S_s and S_i are the number of skeletal bonding molecular orbitals associated with surface (S_s) and interstitial (S_i) moieties.