Inorganic Chemistry, Vol.45, No.1, 328-335, 2006
Phosphato, chromato, and perrhenato complexes of titanium(IV) and zirconium(IV) containing Klaui's tripodal ligand
Treatment of titanyl sulfate in dilute sulfuric acid with 1 equiv of NaLOEt (L-OEt(-) = [(eta(5) -C5H5)Co{P(O)(OEt)(2)}(3)](-)) in the presence of Na3PO4 and Na4P2O7 led to isolation of [(LOEtTi)(3)(mu-O)(3)(mu(3)-PO4)] (1) and [(LOEtTi)(2)(mu-O)(mu-P2O7)1 (2), respectively. The structure of 1 consists of a Ti3O3 core capped by mu(3)-phosphato group. In 2, the [P2O7](4-) ligands binds to the two Ti's in a U:172,171 fashion. Treatment of titanyl sulfate in dilute sulfuric acid with NaLOEt and 1.5 equiv of Na2Cr2O7 gave [(LOEtTi)(2)(mu-CrO4)(3)] (3) that contains two LOEtTi3+ fragments bridged by three mu-CrO42--O,O' ligands. Complex 3 can act as a 6-electron oxidant and oxidize benzyl alcohol to give ca. 3 equiv of benzaldehyde. Treatment of [LOEtTi(OTf)(3)] (OTf- = triflate) with [n-Bu4N][ReO4] afforded [{LOEtTi(ReO4)(2)}(2)(mu-O)] (4). Treatment of [LOEtMF3] (M = Ti and Zr) with 3 equiv of [ReO3(OSiMe3)] afforded [LOEtTi(ReO4)(3)] (5) and [LOEtZr(ReO4)(3)(H2O)] (6), respectively. Treatment of [LOEtMF3] with 2 equiv of [ReO3(OSiMe3)] afforded [LOEtTi(ReO4)(2) (ReO4)(2)F] (7) and [{LOEtZr(ReO4)(2)}(2)(mu-F)(2)] (8), respectively, which reacted with Me3SiOTf to give [LOEtM(ReO4)(2)(OTf)] (M = Ti (9), Zr (10)). Hydrolysis of [LOEtZr(OTf)(3)] (11) with Na(2)WO(4)center dot xH(2)O and wet CH2Cl2 afforded the hydroxo-bridged complexes [{LOEtZr(H2O)}(3)(mu-OH)(3)(mu(3)-O)][OTf](4) (12) and [{LOEtZr(H2O)(2)}(2)(mu-OH)(2)][OTf](4) (13), respectively. The solid-state structures of 1-3, 6, and 11-13 have been established by X-ray crystallography. The LOEtTiIv complexes can catalyze oxidation of methyl p-tolyl sulfide with tert-butyl hydroperoxide. The bimetallic TV Re complexes 5 and 9 were found to be more active catalysts for the sulfide oxidation than other Ti(IV) complexes presumably because Re alkylperoxo species are involved as the reactive intermediates.