Terphenyl-Ge as µ2-Ge-bis(hexahapto-Trip) Bridging Ligand to Form a New Transition Metal-Only Chelating Lewis Base.

Abstract

Terphenylgermanium Ar*Ge [Ar* = C6H3(2,6-Trip)2, Trip = 2,4,6-C6H2iPr3] was found to act as a novel µ2-Ge-bis(hexahapto-Trip) bridging ligand. Deprotonated terphenyl germanium trihydride [Li(thf)3][Ar*GeH2] (1) undergoes reductive elimination and transfer of hydrogen in reaction with dimeric [(COD)RhCl]2 to yield the dinuclear complex [Ar*GeRh(COE)RhCl(COD)] (2). Subsequent chloride abstraction from compound 2 using Na[BArF4] or Li[Al(OtBuF)4] results in the cationic complexes [Ar*GeRh(COE)Rh(COD)][WCA] (3) {WCA : [BArF4]- (ArF = C6H3-3,5-(CF3)2), [Al(OtBuF)4]-}. Ligand exchange of olefin for CO yields the carbonyl complex [Ar*Ge(Rh(CO))2][BArF4] (4). In an alternative approach to the synthesis of carbonyl complex 4, [Li(thf)3][Ar*GeH2] (1) was treated with [Rh(CO)2Cl]2 leading to the isolation of a hexanuclear rhodium cluster [(µ3-Ar*Ge)2{Rh(CO)2}6(µ3-H)2] (5) in reasonable yield. In reactions with [Rh(CO)2Cl]2 or [Ph3PAuCl] complex 4 abstracts the chloride ligand and forms tetranuclear complexes featuring a GeRh3- or GeRh2Au-rectangle, [Ar*GeCl(Rh3(CO)4)][BArF4] (6), or [Ar*GeCl{Rh2(CO)2}(AuPPh3)][BArF4] (7).