Extended Sandwich Molecules Displaying Direct Metal-Metal Bonds

Treatment of [Cp*IrCl2](2) (Cp* = pentamethylcyclopentadienyl) with Li[BH3(SePh)] at room temperature led to the isolation of a dimetala analogue of hexaborane(10), nido-[(Cp*Ir)(mu-SePh)(2)Ir{(Cp*Ir)SePh}B4H8] (1). Solid-state X-ray structure analysis of 1 showed an extended sandwich molecule with two iridium atoms between Cp* and a [B4Ir] ring. Further, in an effort to synthesize the Rh analogue of 1 under similar reaction conditions, we isolated arachno-[{(Cp*Rh)(mu-SePh)(3)}Rh(mu-SePh)B3H6] (2), a rhodium analogue of tetraboarane(10) in which the {RhB3} unit shows geometric equivalence with a metal pi-allyl {MC3} species. Ir complex 1, having an Ir-Ir bond, can be considered similar to the dizinc sandwich complex [Cp*Zn-ZnCp*] in terms of the valence electron count at the metal centers.