Cyclo-oligomerisation reactions of bis(alkyne) and η2-vinyl complexes of molybdenum and tungsten with t-butyl isocyanide leading to iminocyclopentadiene derivatives

Abstract

Reactions of t-butyl isocyanide with bis(alkyne) complexes [M(SR)(CF₃CCCF₃)₂(η⁵-C₅H₅)](M = Mo, R = C₆F₅; M = W, R = C₆H₄Me-4) and isomeric η²-vinyl complexes [W{C(CF₃)C(CF₃)SR}(CF₃CCCF₃)(η⁵-C₅H₅)](R = Me, Prⁱ, or Bu^t) give bis(isocyanide)-metallacyclic derivatives [[graphic omitted](CF₃)}(SR)(CNBu^t)₂(η⁵-C₅H₅)](7), viaη²-vinyl, [M{η²-C(CF₃)C(CF₃)CNBu^t}(SR)(CF₃CCCF₃)(η⁵-C₅H₅)](M = Mo, R = C₆F₅), or 16-electron monoisocyanide complexes, [[graphic omitted](CF₃)}(SR)(CNBu^t)(η⁵-C₅H₅)](6), isolated for M = W, R = Bu^t. Metallacyclic complexes (6)(R = Bu^t) and (7)(M = W; R = C₆H₄Me-4, Prⁱ, or Bu^t) can be hydrolysed to the iminoacyl oxo complex [W{η³-C(NBu^t)C(CF₃)C(CF₃)C(CF₃)C(CF₃)H}(O)(η⁵-C₅H₅)] whereas thermolysis of (7)(M = Mo, R = C₆F₅; M = W, R = Prⁱ) gives complexes [M(SR)(CNBu^t){η²-C₄(CF₃)₄CNBu^t}(η⁵-C₅H₅)] containing an iminocyclopentadiene ligand bonded in a novel η² manner via the exocyclic C–N bond to the metal.