New organometallic dioxotungsten(vi) complexes containing N2S tridentate ligands: the synthesis and reactivity of chloro and alkyl derivatives

Abstract

A new series of N-benzyl aliphatic N₂S tridentate proligands HLⁿ (n = 2–4) derived from 2-[(2-mercaptoethyl)aminomethyl]pyridine (HL¹) has been prepared via the sequential reactions of trimethylsilylation, N-benzylation, and hydrolysis. A previously reported aromatic N₂S tridentate proligand, 2-[(2-mercaptophenyl)aminomethyl]pyridine (HL⁵), is also employed as an ancillary ligand. Reaction of these proligands HLⁿ (n = 1–5) with [WO₂Cl₂(DME)] (DME = 1,2-dimethoxyethane) in the presence of triethylamine leads to the formation of cis-dioxotungsten(VI) complexes [WO₂(Lⁿ)Cl] (n = 1–5). Treatment of the chloro derivatives [WO₂(Lⁿ)Cl] (n = 1, 5) with the Grignard reagents RMgX (R = CH₂SiMe₃, C₆H₄^tBu-4; X = Cl, Br) resulted in ligand substitution reaction and the formation of the first reported alkyl complexes of the type [WO₂(Lⁿ)R] (n = 1, 5; R = CH₂SiMe₃, C₆H₄^tBu-4).