Synthesis and structures of dioxo-Mo(VI) and -W(VI) amides

Abstract

Treatment of [MO₂Cl₂·(DME)] (M = Mo, W; DME = 1,2-dimethoxyethane) with the lithium reagents LiLⁿ [L¹ = ⁻N(SiMe₃)(2-C₅H₃N-6-Me), L² = ⁻N(SiBu^tMe₂)(2-C₅H₃N-6-Me), L³ = ⁻N(SiBu^tPh₂)(2-C₅H₃N-6-Me)] afforded the corresponding cis-dioxo-Mo(VI) amido complexes [MoO₂(Lⁿ)₂] (Lⁿ = L¹1, Lⁿ = L²2, Lⁿ = L³3) and cis-dioxo-W(VI) amido complexes [WO₂(Lⁿ)₂] (Lⁿ = L¹4, Lⁿ = L²5, Lⁿ = L³6). X-Ray crystallography shows that compounds 1, 2, 4 and 5 are mononuclear with the amido ligands bound to the metal centres in a N,N-chelating fashion forming highly strained four-membered metallacyclic rings with biting angles N_amido–M–N_py around 60°. The Mo–N_amido and W–N_amido distances are comparable which fall in the range of 2.070–2.081 Å.