The synthesis of the novel mixed halide seven-coordinate complex [WBrI(CO) 3(NCMe) 2] and its reactions with alkynes

Abstract

The tris-acetonitrile complex [W(CO) 3(NCMe) 3] reacts in situ with an equimolar quantity of BrI at 0°C to afford a quantitative yield of the seven-coordinate complex [WBrI(CO) 3(NCMe) 2]. Reaction of [WBrI(CO) 3(NCMe) 2] with one equivalent of RC 2R′ (R = R′= Ph or CH 2Cl; R = Me, R′= Ph), in CH 2Cl 2 at room temperature, rapidly gave the dimeric complexes [W(η-I)Br(CO)(NCMe)(η 2 -RC 2R′)] 2 in good yield. 13C NMR spectroscopy suggests that the alkynes are acting as four-electron donors in the dimeric compounds [W(η-I)Br(CO)(NCMe)(η 2 -RC 2R′)] 2. Two equivalents of RC 2R′ (R= R′= Me, Ph or CH 2Cl; R = Me, R′ = Ph) react with [WBrI(CO) 3(NCMe) 2], in CH 2Cl 2 at room temperature, to give the bis-alkyne complexes [WBrI(CO)(NCMe)(η 2-RC 2R′) 2] in high yield. The bis-diphenylacetylene complex, [WBrI(CO)(NCMe)(η 2-PhC 2Ph) 2], can also be prepared by reacting the iodo-bridged dimer [W(η-I)Br(CO)(NCMe)(η 2-PhC 2Ph)] 2 in CH 2Cl 2 at room temperature, with two equivalents of diphenylacetylene. The alkyne ligands are donating an average of three electrons each to the tungsten in these complexes.