ic051329u_si_005.cif (20.91 kB)

Phosphato, Chromato, and Perrhenato Complexes of Titanium(IV) and Zirconium(IV) Containing Kläui's Tripodal Ligand

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posted on 09.01.2006, 00:00 by Yi, Qian-Feng Zhang, Tony C. H. Lam, Eddie Y. Y. Chan, Ian D. Williams, Wa-Hung Leung
Treatment of titanyl sulfate in dilute sulfuric acid with 1 equiv of NaLOEt (LOEt- = [(η5-C5H5)Co{P(O)(OEt)2}3]-) in the presence of Na3PO4 and Na4P2O7 led to isolation of [(LOEtTi)3(μ-O)33-PO4)] (1) and [(LOEtTi)2(μ-O)(μ-P2O7)] (2), respectively. The structure of 1 consists of a Ti3O3 core capped by a μ3-phosphato group. In 2, the [P2O7]4- ligands binds to the two Ti's in a μ:η22 fashion. Treatment of titanyl sulfate in dilute sulfuric acid with NaLOEt and 1.5 equiv of Na2Cr2O7 gave [(LOEtTi)2(μ-CrO4)3] (3) that contains two LOEtTi3+ fragments bridged by three μ-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(μ-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)2F] (7) and [{LOEtZr(ReO4)2}2(μ-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 Na2WO4·xH2O and wet CH2Cl2 afforded the hydroxo-bridged complexes [{LOEtZr(H2O)}3(μ-OH)33-O)][OTf]4 (12) and [{LOEtZr(H2O)2}2(μ-OH)2][OTf]4 (13), respectively. The solid-state structures of 13, 6, and 1113 have been established by X-ray crystallography. The LOEtTiIV complexes can catalyze oxidation of methyl p-tolyl sulfide with tert-butyl hydroperoxide. The bimetallic Ti/ 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.