Z-Selective Olefin Metathesis Reactions Promoted by Tungsten Oxo Alkylidene Complexes

Abstract

Addition of LiOHMT (OHMT = O-2,6-dimesitylphenoxide) to W(O)(CH-t-Bu)(PMe[subscript 2]Ph)[subscript 2]Cl[subscript 2] led to WO(CH-t-Bu)Cl(OHMT)(PMe[subscript 2]Ph) (4). Subsequent addition of Li(2,5-Me[subscript 2]C[subscript 4]H[subscript 2]N) to 4 yielded yellow W(O)(CH-t-Bu)(OHMT)(Me[subscript 2]Pyr)(PMe[subscript 2]Ph) (5). Compound 5 is a highly effective catalyst for the Z-selective coupling of selected terminal olefins (at 0.2% loading) to give product in >75% yield with >99% Z configuration. Addition of 2 equiv of B(C[subscript 6]F[subscript 5])[subscript 3] to 5 afforded a catalyst activated at the oxo ligand by B(C[subscript 6]F[subscript 5])[subscript 3]. 5·B(C[subscript 6]F[subscript 5])[subscript 3] is a highly active catalyst that produces thermodynamic products (~20% Z).