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Homoleptic hexa and penta gallylene coordinated complexes of molybdenum and rhodium

Abstract:

The reactions of molybdenum(0) and rhodium(I) olefin containing starting materials with the carbenoid group 13 metal ligator ligand GaR (R = Cp*, DDP; Cp* = pentamethylcyclopentadienyl, DDP = HC(CMeNC6H 3-2,6-iPr2)2) were investigated and compared. Treatment of [Mo(η4-butadiene)3] with GaCp* under hydrogen atmosphere at 100 °C yields the homoleptic, hexa coordinated, and sterically crowded complex [Mo(GaCp*)6] (1) in good yields ≥50%. Compound 1 exhibits an unusual and high coordinated octahedral [MoGa6] core. Similarly, [Rh(GaCp*) 5][CF3SO3] (2) and [Rh(GaCp*) 5][BArF] (3) (BArF = B{C6H 3(CF3)2}4) are prepared by the reaction of GaCp* with the rhodium(I) compound [Rh(coe) 2(CF3SO3)]2 (coe = cyclooctene) and subsequent anion exchange in case of 3. Compound 2 features a trigonal bipyramidal [RhGa5] unit. In contrast, reaction of excess Ga(DDP) with [Rh(coe)2(CF3SO3)]2 does not result in a high coordinated homoleptic complex but instead yields [(coe)(toluene)Rh{Ga(DDP)}(CF3SO3)] (4). The common feature of 2 and 4 in the solid state structure is the presence of short CF 3SO2O•••Ga contacts involving the GaCp* or rather the Ga(DDP) ligand. Compounds 1, 2, and 4 have been fully characterized by single crystal X-ray diffraction, variable temperature 1H and 13C NMR spectroscopy, IR spectroscopy, mass spectrometry, as well as elemental analysis. © 2011 American Chemical Society.