Discrete Variational (DV)-X? Calculations of Incomplete Cubane-Type Molybdenum Clusters [Mo3X4(H2O)9]4+ (X= O,S)1

Abstract

Electronic structures of two incomplete cubane-type clusters [Mo3X4(H2O)9]4+ (X =O, S) have been calculated by the discrete-variational (DV)-Xα method. The calculations explain the experimental results of valence-band X-ray photoelectron spectra, electronic spectra, and reactivity difference toward acetylene. The net charge of Mo in [Mo3S4(H2O)9]4+(S) is more negative than that of Mo in [MO3O4H2O)4+] (O), and the bridging sulfur atoms are the main negative charge-source for the molybdenum atoms in the cluster S. As for S,levels of HOMO (45e) and LUMO (46e) consist mainly of Mo 4d andμ-S 3p atomic orbitals, and contribution ofμ3-S 3p to the orbitals is not large. The existence of Mo-Mo, Mo-μ-S, and Mo-μ3-S bounds is clear from the contour maps of the orbitals. As for O levels of HOMO (40e) and LUMO (41c) consist mainly of Mo 4d andμ-O 2p atomic orbitals. Contribution ofμ3-O 2p to the orbitals is not large except in the orbital 30a1,. The existence of Mo-Mo, Mo-μ-O, and MO-μ3-O bonds also is appreciable from the contour maps of the orbitals.