Formation of mixed-metal alkoxides mediated by the reactivity of coordinated pinacol - Synthesis and molecular structures of Ce2Ti2(mu(3)-O)(2)(mu,eta(2)-OCMe2CMe2O)(4)(OPri)(4)((PrOH)-O-i)(2) and of Ce2Nb2(mu(3)-O)(2)(mu,eta(2)-OCMe2CMe2O)(4)(OPri)(6)

The addition of pinacol to mixtures of titanium and cerium isopropoxides as well as the use of insoluble titanium and cerium pinacolate synthons was i nvestigated as a route to M-Ce (M=Ti, Nb) species. Pinacol was able to prom ote the formation of mixed-metal species and the first Ce-Ti and Ce-Nb spec ies namely Ce-2Ti(pin)(2)(OPri)(8) and [M2Ce2(mu(3)-O)(2)(mu,eta(2)pin)(4)( OPri)(6)H-x] [M = Ti, x = 2; M = Nb, x = 0; pin = OCMe2-COMe2] were isolate d and characterized by FT-IR and H-1 NMR. The latter were also characterize d by X-Ray diffraction. Their structures are based on a rhombus compressed along the M...M direction with 6-coordinated metals. The pinacolate moietie s act as bridging-chelating ligands. The metal-oxygen bond lengths vary acc ording to M-O(pin)<M-mu(3)-O<M mu-O(pin)<Ce-OPri<Ce-mu(3)O. (C) 1999 Elsevi er Science Ltd. All rights reserved.