title: Electron counts for face-bridged octahedral transition metal clusters.
abstract: Kohn-Sham orbital energy patterns were used to rationalize valence electron counts for stable face-capped octahedral clusters [M(6)E(8)L(6)] (E=S, Se, Te, Cl; L=CO, PMe(3), Cl(-)). When L is a pi acceptor such as CO or PMe(3), stable closed-shell clusters are found for 80, 84, and 98 electrons. For L=Cl(-) (i.e. a pi-electron donor), only a count of 84 electrons appears favorable, as is found in [Mo(6)Cl(14)](2-). These counting rules apply to fivefold coordination of M, which becomes unstable if the electron count exceeds 98, for example, for M=Ni. In this case structures with tetrahedrally coordinated M are energetically favored, and this leads to different cluster structures.
authors.affiliation: Theoretical Chemistry, Institute of Physical Chemistry, University of Karlsruhe, 76128 Karlsruhe, Germany.
authors.forename: Peng-Dong
authors.initials: PD
authors.lastname: Fan
authors.forename: Peter
authors.initials: P
authors.lastname: Deglmann
authors.forename: Reinhart
authors.initials: R
authors.lastname: Ahlrichs