Homoleptic Hexa and Penta Gallylene Coordinated Complexes of Molybdenum and Rhodium

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(CMeNC6H3-2,6-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{C6H3(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 CF3SO2O···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.