Dioxomolybdenum(vi) and dioxotungsten(vi) complexes supported by an amido ligand

Abstract

Stepwise addition of one equivalent of n-butyllithium and trimethylsilyl chloride to 2-tert-butylmercaptoaniline affords the new ligand 1-(Me₃SiNH)-2-(t-BuS)C₆H₄ (LH), that reacts with one equivalent of butyllithium to its lithium salt LLi. Dioxodichloromolybdenum [MoO₂Cl₂] and dioxodichlorotungsten dimethoxyethane [WO₂Cl₂(dme)] react in tetrahydrofuran solution at low temperature with two equivalents LLi to monomeric dioxomolybdenum(VI) [MoO₂L₂] (1) and dioxotungsten(VI) complex [WO₂L₂] (2) employing two bidentate amido thioether ligands. The crystallographic determination of the molecular structures of 1 and 2 show evidence for M⋯S contacts. The reaction of [MoO₂Cl₂] with LLi in tetrahydrofuran solution at room temperature leads next to 1 to two compounds where silyl group migration from nitrogen to oxygen atoms occurs forming [Mo(NL′)₂(OSiMe)₂] (3) and [Mo(NL′)₂(OSiMe₃)L] (4, L′ = N-2-t-BuSC₆H₄) as determined by NMR spectroscopy. Compound 4 was isolated in low yield and its molecular structure determined by X-ray crystallography. Higher yields of a bisimido complex can be obtained by the direct reaction of one equivalent of LLi with [Mo(NAr)₂Cl₂(dme)] (Ar = 2,6-Me₂C₆H₄) forming [Mo(NAr)₂LCl] (5).