Formation of substituted cyclopentadienyl ligands on tungsten via reactions between the alkyne complexes [W(CO)(R1C2R2)3](R1= R2= Ph or Et; R1= Me, R2= Ph) and the alkylidyne compounds [W(CR)(CO)2(η-C5H5)](R = C6H4Me-4 or Me); X-ray crystal structures of [W2(µ-CO)2(CO)(η-PhC2Ph)(η-C5Ph4R)-(η-C5H5)] and [W2(µ-EtC2Et)(CO)4(η-C5Et4R)(η-C5H5)](R = C6H4Me-4)

Abstract

In octane under refiux the compounds [W(CO)(R¹C₂R₂)₃](R¹= R²= Ph or Et) react with [W(CC₆H₄Me-4)(CO)₂(η-C₅H₅)] to give the ditungsten complexes [W₂(µ-CO)₂(CO)(η-PhC₂Ph){η-C₅Ph₄(C₆H₄Me-4)}(η-C₅H₅)] and [W₂(µ-EtC₂Et)(CO)₄{η-C₅Et₄(C₅H₄Me-4)}(η-C₅H₅)], respectively. The structures of these products have been established by X-ray diffraction studies. In the former species a short W–W bond [2.586(1)Å] is asymmetrically bridged by two CO groups, and a PhC₂Ph ligand is terminally bound to one tungsten atom. In the latter molecule a hex-3-yne ligand transversely bridges a W–W vector [3.003(1)Å]; three carbonyl groups are terminally attached to the tungsten atoms and one is semi-bridging. Reaction of [W(CMe)(CO)₂(η-C₅H₅)] with [W(CO)(PhC₂Ph)₃] also affords an alkyne-bridged ditungsten compound [W₂(µ-PhC₂Ph)-(CO₄),(η-C₅MePh₄)(η-C₅H₅)]. The species [W(CO)(MeC₂Ph)₃], containing an unsymmetrical alkyne, reacts in octane under reflux with [W(CC₆H₄Me-4)(CO)₂(η-C₅H₅)] to give the complex [W₂(µ-MeC₂Ph)(CO)₄{η-C₅Me₂Ph₂(C₆H₄Me-4)}(η-C₅H₅)], produced as an isomeric mixture. The spectroscopic data (i.r. and n.m.r.) for the new compounds are reported and discussed and a possible mechanism for their formation suggested.