Formation of novel η2-vinyl complexes by nucleophilic attack at co-ordinated hexafluorobut-2-yne; implications for the stereochemistry of addition and insertion reactions of co-ordinated acetylenes. Crystal and molecular structure of [Mo{SC5H4NC(CF3)·C(CF3)}-(CF3CCCF3)(η-C5H5)]

Abstract

Reactions of Tl (LL)(LL^–= pyridine-2-thiolato), pyrimidine-2-thiolato, or thiazoline-2-thiolato) with the bis-hexafluorobut-2-yne complexes [MCl(CF₃CCCF₃)₂-(η-C₅H₅)](M = Mo or W), give products [M {(LL)-C(CF₃)·C(CF₃)}(CF₃CCCF₃)(η-C₅H₅] containing a novel η²-vinyl ligand resulting from nucleophilic attack of LL^–on an alkyne ligand whereas with [WCl(CF₃CCCF₃)₂-(η-C₅H₅)] the thallium(I) salt of 2-mercaptopyridine N-oxide unexpectedly promotes cyclopentadienyl group displacement to give the co-ordinatively unsaturated bis-hexafluorbut-2-yne complexes [W(SC₅H₄NO)₂(CF₃CCCF₃)₂]; and [W(SC_5H4NO)(CF₃CCCF₃)₂]; the structure of [Mo{SC₅H₄NC(CF₃)·C(CF₃)}(CF₃CCCF₃)(η-C₅H₅)] has been determined by X-ray crystallography.