Formation of mixed-metal alkoxides mediated by the reactivity of coordinated pinacol: Synthesis and molecular structures of Ce 2Ti 2(μ 3-O) 2(μ,η 2-OCMe 2CMe 2O) 4(OPr i) 4(Pr iOH) 2 and of Ce 2Nb 2(μ 3-O) 2(μ,η 2-OCMe 2CMe 2O) 4(OPr i) 6

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The addition of pinacol to mixtures of titanium and cerium isopropoxides as well as the use of insoluble titanium and cerium pinacolate synthons was investigated as a route to M-Ce (M=Ti, Nb) species. Pinacol was able to promote the formation of mixed-metal species and the first Ce-Ti and Ce-Nb species namely Ce 2Ti(pin) 2(OPr i) 8 and [M 2Ce 2(μ 3-O) 2(μ,η 2pin) 4(OPr i) 6H x ] [M=Ti, x=2; M=Nb, x=0; pin=OCMe 2-COMe 2] were isolated and characterized by FT-IR and 1H NMR. The latter were also characterized by X-Ray diffraction. Their structures are based on a rhombus compressed along the M⋯M direction with 6-coordinated metals. The pinacolate moieties act as bridging-chelating ligands. The metal–oxygen bond lengths vary according to M–O(pin)<M-μ 3–O<Mμ–O(pin)<Ce–OPr i<Ce–μ 3O.