Attack by allenes on a bridging alkylidyne ligand at a ditungsten centre: formation of a bridging allyl-η3-W1,σ-W2-alkylidene ligand

Abstract

The alkylidene bridged compounds [(Me3SiCH2)2W(µ-CSiMe3)]2(1), [(Me3SiCH2)(ButO) W(µ-CSiMe3)]2(2) and [(PriO)2W(µ-CSiMe3)]2(3) each react with allenes R1CHCCHR2, where R1= R2= H, Me or R1= Me, Ph and R2= H, to give, by C–C bond formation between the tertiary carbon atom of the allene and the bridging carbon atom of one of the µ-CSiMe3 ligands, a bridging ligand which is a formally a π-allyl to one tungsten atom and a terminal alkylidene to the other; the rate of reactions follows the order (1) > (2) > (3); CH2CCH2 RCHCCH2 > RCHCCHR, and the C–C bond formation is stereoselective.