Exploring the reactivity of tungsten bis(imido) dimethyl complexes with methyl aluminium reagents: implications for ethylenedimerization

Abstract

The reaction of [WCl₂(NAr)₂(DME)] (1) with excess Me₃Al affords the dimethyl complex [WMe₂(N{Ar}AlMe₂{μ-Cl})(NAr)] (2), which on treatment with THF or MeAlCl₂ yields [WMe₂(NAr)₂(THF)] (3) and [WMe₂(N{Ar}AlMe(Cl){μ-Cl})(NAr)] (5), respectively. Complex 3 is unstable in solution dissociating to form [WMe₂(NAr)₂] (4) that may be isolated as an adduct with PMe₃, [WMe₂(NAr)₂(PMe₃)] (6). While complex 2 is inert towards ethylene, complex 3 reacts rapidly to afford a mixture of methane and but-1-ene (1 : 4). Neither complex 2 nor 3 react with propylene. Reaction of 3 with a C₂H₄/C₂D₄ (1 : 1) affords a mixture of isotopomers that is consistent with complete isotopic scrambling. The structures of complexes 1, 2, and 3 have been determined by X-ray diffraction.