Reactions of electrophilic alkynes with some iron and tungsten sulphur, selenium, and arsenic complexes

Abstract

Reactions of [Fe(AsMe₂)(CO)₂(η⁵-C₅H₅)], [W(AsMe₂)(CO)₃(η⁵-C₅H₅)], and [W(SR′)(CO)₃(η⁵-C₅H₅)] with activated alkynes CF₃CCCF₃ and/or MeO₂CCCCO₂Me afford metallacyclic complexes [[graphic omitted]sMe₂}(CO)(η⁵-C₅H₅)], [[graphic omitted]sMe₂}(CO)₂(η⁵C₅H₅)](R = CF₃ or CO₂Me), and [[graphic omitted]R′}(CO)₂(η⁵-C₅H₅)](R = CF₃, R′= Prⁿ; R = CO₂Me, R′= Prⁱ or Prⁿ) or the η²-vinyl complex [W{η²-C(CF₃)C(CF₃)C(O)SR′}(CO)₂(η⁵-C₅H₅)] when R′= Prⁱ. The photoiytic reaction of [W(SePh)(CO)₃(η⁵-C₅H₅)] with CF₃CCCF₃ gives an alkyne derivative [W(SePh)(CO)(CF₃C-CCF₃)(η⁵-C₅H₅)]. A similar species [W(SC₆H₄Me-4)(CO)(CF₃C-CCF₃)(η⁵-C₅H₅)] was obtained from the thermal reaction of [W(SC₆H₄Me-4)(CO)₃(η⁵-C₅H₅)] with F₃C-CCF₃via metallacyclic [[graphic omitted]C₆H₄Me-4}(CO)₂(η⁵-C₅H₅)] and η²-vinyl [W{η²-C(CF₃)C(CF₃)C(O)SC₆H₄Me-4}(CO)₂(η⁵-C₅H₅)] intermediates. In contrast, [[graphic omitted]Prⁿ}(CO)₂(η⁵-C₅H₅)] isomerises via an η²-vinyl analogue into the S-bonded vinyl ketone complex [[graphic omitted]Prⁿ}(CO)₂(η⁵-C₅H₅)] as a result of a 1,3 SR′ shift across the metallacyclic ring. Such a shift is also observed on thermal isomerisation of [[graphic omitted]R′}(CO)₂(η⁵-C₅H₅)](R′= Me or Prⁱ) but this proceeds via a avinyl intermediate [W{C(CO₂Me)C(CO₂Me)SR′}(CO)₃(η⁵-C₅H₅)] to give both S- and O-metallated isomeric vinyl ketone derivatives. The mechanism of the shift is discussed in terms of three alternative pathways which are determined by the nature of the group R on the alkyne. The η²- vinyl complexes [W{η²-C(CF₃)C(CF₃)C(O)SR′}(CO)₂(η⁵-C₅H₅)](R′= Me or Prⁱ), on reaction with two-electron donor ligands L = CO, CNBu^t, PMe₂Ph, or P(OMe)₃, afford η³-lactone derivatives [W{η³-C(CF₃)C(CF₃)C(SR′)OC(O)}(CO)L(η⁵-C₅H₅)] as a result of cyclisation of the η²-vinyl ligand with a co-ordinated carbonyl group.