Dioxomolybdenum(VI) and -tungsten(VI) complexes with tetradentate aminobis(phenol)s

Abstract

Aminobis(phenol) ligands (H 2L n ) carrying either a dimethylamino, a pyridyl or a methoxy sidearm donor were used in the preparation of new tungsten and molybdenum complexes. Treatment of [W(eg) 3] (eg = 1,2-ethanediolate dianion) with H 2L n under hydrolytic conditions in a CHCl 3–MeOH mixture gave the cis-dioxotungsten(VI) complexes [WO 2(L n )] in good yields. The corresponding molybdenum complexes [MoO 2(L n )] were prepared from [MoO 2(acac) 2] and respective ligands. The solid-state structures of two molybdenum and one tungsten compounds were determined by single crystal X-ray diffraction, which revealed that the dianionic aminobis(phenolate) backbones of the ligands have coordinated to the metal centre as [O,N,O] donors, whereas the last coordination sphere has been occupied by a N or O donor atom of the ligand sidearm. All synthesized new complexes can catalyse the oxotransfer reaction between benzoin and dmso at 120 °C.