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.