Synthesis, molecular structures, fluxional properties and catalytic activity of a series of alkyne complexes of molybdenum(II) and tungsten(II) containing phosphite donor ligands

Abstract

Treatment of [MoI₂(CO)(NCMe)(η²-R′C₂R″)₂] with one equivalent of P(OPh)₃ in diethyl ether at room temperature afforded the crystallographically characterised complexes [MoI₂(CO)(NCMe){P(OPh)₃}(η²-R′C₂R″)] (R′ = R″ = Me or Ph; R′ = Me, R″ = Ph) which have five different ligands attached in a pseudo-octahedral arrangement. Reaction of [MI₂(CO)(NCMe)(η²-R′C₂R″)₂] with two equivalents of P(OR)₃ in diethyl ether at room temperature gave high yields of the bis(phosphite) complexes [MI₂(CO){P(OR)₃}₂(η²-R′C₂R″)] {R = Ph, R′ = Me, R″ = Ph (M = Mo only); M = Mo or W, R = Me, R′ = R″ = Me or Ph (M = Mo only), R′ = Me, R″ = Ph (M = W only); R′ = Me, R″ = Ph (M = W only); R = Et, R′ = R″ = Me or Ph (M = Mo only), R′ = Me, R″ = Ph (M = W only); R = ⁱPr, R′ = R″ = Me or Ph (M = Mo only), R′ = Me, R″ = Ph (M = W only); R = ⁿBu, R′ = R″ = Me, Ph (M = Mo only for both complexes)}. The crystal structures for [MI₂(CO){P(OR)₃}₂(η²-R′C₂R″)] {M = Mo, R = Me, ⁱPr; R′ = R″ = Me; M = Mo, R = Ph, R′ = Me, R″ = Ph; M = W, R = Et or ⁱPr; R′ = R″ = Me; R′ = Me, R″ = Ph (R = ⁱPr only)} have been determined, and all have trans-phosphite ligands except for M = Mo, R = R′ = R″ = Me which has cis-phosphite groups. The trimerisation of MeC₂Ph by the reaction of [MoI₂(CO)(NCMe)(η²-MeC₂Ph)₂] with P(OⁱPr)₃ to give the crystallographically characterised trimer of MeC₂Ph, 1,2,4-trimethyl-3,5,6-triphenylbenzene, is also described. The fluxional properties of selected complexes have been investigated.