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

Treatment of [MoI2(CO)(NCMe)(eta(2)-R'C2R")(2)] with one equivalent of P(OP h)(3) in diethyl ether at room temperature afforded the crystallographicall y characterised complexes [MoI2(CO)(NCMe){P(OPh)(3)}(eta(2)-R'C2R")] (R'=R" =Me or Ph; R'=Me, R"=Ph) which have five different ligands attached in a ps eudo-octahedral arrangement. Reaction of [MI2(CO)(NCMe)(eta(2)-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)(eta(2)-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 = Pr-i, 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)}. T he crystal structures for [MI2(CO){P(OR)(3)}(2)(eta(2)-R'C2R")] {M = Mo, R = Me, Pr-i; R' = R" = Me; M = Mo, R = Ph, R' = Me, R" = Ph; M = W, R = Et o r Pr-i; R' = R" = Me; R' = Me, R" = Ph (R = Pr-i only)} have been determine d, 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 reactio n of [MoI2(CO)(NCMe)(eta(2)-MeC2Ph)(2)] with P((OPr)-Pr-i)(3) to give the c rystallographically characterised trimer of MeC2Ph, 1,2,4-trimethyl-3,5,6-t riphenylbenzene, is also described. The fluxional properties of selected co mplexes have been investigated.