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)(Bu^tO) 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.