Reactions of some iron and tungsten mercapto-complexes with electrophilic acetylenes leading to novel metallacycles. The crystal and molecular structure of the η2-vinyl complex [W{η2-C(CF3)C(CF3)C(O)SMe}(CO)2(η5-C5H5)]

Abstract

Reactions of [Fe(SR′)(CO)₂(η⁵-C₅H₅)] with activated alkynes CF₃CCCF₃ and MeO₂CCCCO₂Me give heterocyclic complexes [[graphic omitted]R′}(CO)(η⁵-C₅H₅)](R′= alkyl or aryl, R = CF₃ or CO₂Me). Related derivatives [[graphic omitted]R′}(CO)₂(η⁵-C₅H₅)](R′= Me or Et) obtained from [W(SR′)(CO)₃(η⁵-C₅H₅)] and the alkynes in hexane at 20 °C undergo a sequence of thermal isomerisations above 25 °C involving initially a novel 1,3 shift of the SR′ ligand across the eneone ligand to give the η²-vinyl complex [W{η²-C(R)C(R)C(O)SR′}(CO)₂(η⁵-C₅H₅)](R = CF₃ only) followed by S-bonded vinyl ketone complexes [[graphic omitted]R′}(CO)₂(η⁵-C₅H₅)] and ultimately O-bonded vinyl ketone derivatives [[graphic omitted]}(CO)₂(η⁵-C₅H₅)] and co-ordinatively unsaturated alkyne complexes [W(SR′)(CO)(RCCR)(η⁵-C₅H₅)](R = CF₃ only). An X-ray structure determination of the η²-vinyl complex [W{η²-C(CF₃)C(CF₃)C(O)SMe}(CO)₂(η⁵-C₅H₅)] reveals the first example of a vinyl group bonded to a metal via both carbon atoms and therefore acting as a three-electron donor ligand. The structure consists of an approximately octahedrally co-ordinated tungsten atom bonded to an η⁵-C₅H₅ ligand which occupies one face of the octahedron. Two carbonyl ligands occupy two octahedral sites while the third is occupied by the η²-C(CF₃)C(CF₃)C(O)SMe ligand which adopts an orientation such that the vinylic C–C axis lies approximately parallel to one of the W–CO axes.