Co-ordinatively unsaturated alkyne complexes of molybdenum and tungsten. Reactions of [MCl(CF₃C=CCF₃)₂(η-C₅H ₅)] (M = Mo or W) with heterocyclic thiolates leading to η²-vinyl complexes

Reactions of Tl(SR) (SR^- = pyridine-2-thiolate, pyrimidine-2-thiolate, or thiazoline-2-thiolate) with the bis(hexafluorobut-2-yne) complex [MoCl(CF₃C=CCF₃)₂(?-C₅H ₅)] give products [Mo{C(CF₃)-C(CF₃)RS}(CF₃C=-CCF ₃)(?-C₅H₅)] containing a novel ?²-vinyl ligand resulting from nucleophilic attack of nitrogen on a co-ordinated alkyne. The same pyridine-2-thiolate complex is obtained from the reaction of [MoCl(CF₃C=CCF₃)₂(?-C₅H ₅)] with the thallium(I) salt of 2-mercaptopyridine N-oxide, in addition to [Mo{C(CF₃)=C(CF₃)C(CF₃)=C(CF ₃)SC₅H₄NO}(?-C₅H₅)]. The complex [WCl(CF₃C=CCF₃)₂(?-C₅H ₅)] reacts with thallium(I) pyridine-2-thiolate to give the ?²-vinyl complex [W{C(CF₃)-C(CF₃)NC₅H₄S}(CF ₃C=CCF₃)(?-C₅H₅)], whereas with Tl(SC₅H₄NO) cyclopentadienyl-ligand displacement is also observed giving the co-ordinatively unsaturated bis(hexafluorobut-2-yne) complexes [W(SC₅H₄NO)₂(CF₃C=CCF ₃)₂] and [W(SC₅H₄N) (SC₅H₄NO)(CF₃C=CCF₃)₂].