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

The reaction of [WCl(2)(NAr)(2)(DME)] (1) with excess Me(3)Al affords the dimethyl complex [WMe(2)(N{Ar} AlMe(2){mu-Cl})(NAr)] (2), which on treatment with THF or MeAlCl(2) yields [WMe(2)(NAr)(2)(THF)] (3) and [WMe(2)(N{Ar} AlMe(Cl){mu-Cl})(NAr)] (5), respectively. Complex 3 is unstable in solution dissociating to form [WMe(2)(NAr)(2)] (4) that may be isolated as an adduct with PMe(3), [WMe(2)(NAr)(2)(PMe(3))] (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 C(2)H(4)/C(2)D(4) (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.