Synthesis and characterization of d2 imido complexes of molybdenum. Crystal structure of [MoCl2{N(mes)}(PhCCPh)(PMe3)2]·0.5PhCCPh (mes = 2,4,6-trimethylphenyl)‡

Abstract

The compound [MoCl₂{N(mes)}(PMe₃)₃] 1 (mes = 2,4,6-trimethylphenyl) has been prepared by the reaction of [MoCl₃{N(mes)}(dme)] (dme = 1,2-dimethoxyethane) with 2 equivalents of PMe₃ and subsequent sodium amalgam reduction, in the presence of 1 additional equivalent of PMe₃. Metathesis reactions of 1 with KX gave [MoX₂{N(mes)}(PMe₃)₃] (X = Br 2 or NCS 3), whereas the anionic bidentate PrⁱOCS₂^– ligand produced the monophosphine compound [Mo{N(mes)}(S₂COPrⁱ)₂(PMe₃)] 4. Substitution of two of the PMe₃ ligands to give [MoCl₂{N(mes)}(PMe₃)(depe)] 5 (depe = Et₂PCH₂CH₂PEt₂) is also feasible, whilst phosphites and other π acceptors provided the corresponding [MoCl₂{N(mes)}L(PMe₃)₂] compounds [L = P(OMe)₃ 6, P(OCH₂)₃CCH₂CH₃ 7, C₂H₄ 8, H₂CCHCO₂Me 9, CO 10, CNBu^t 11, CNMe 12, PhCCH 13 or PhCCPh 14] by substitution of the unique PMe₃ group of 1. Some of these arylimido complexes exhibit dynamic behaviour in solution, due to restricted rotation of the aryl group around the C–N bond. The molecular structure of 14 (as its PhCCPh hemisolvate, i.e. 14·0.5PhCCPh) has been determined by an X-ray study.