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)]

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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.

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