Diastereoselectivity at chiral metal center of half-sandwich-type ruthenium complexes with planar-chiral cyclopentadienyl ligands in multiple ligand transfer reaction

Abstract

The triple ligand transfer reaction between planar-chiral cyclopentadienyl–ruthenium complexes [Cp′Ru(NCMe) 3][PF 6] ( 1) (Cp′ = 1-(COOR 2)-2-Me-4-R 1C 5H 2; R 1 = Me, Ph, t-Bu) and iron complexes CpFe(CO)(L)X ( 2) (L = PMe 3, PMe 2Ph, PMePh 2, PPh 3; X = I, Br) resulted in the formation of metal-centered chiral ruthenium complexes Cp′Ru(CO)(L)X ( 3) in moderate yields with diastereoselectivities of up to 68% de. The configurations of some major diastereomers were determined to be S Cp ∗ R Ru ∗ by X-ray crystallography. The diastereoselectivity of 3 was under kinetic control and not affected by the steric effect of the substituents on the Cp′ ring of 1 and the phosphine of 2. Although the double ligand transfer reaction between [Cp′Ru{P(OMe) 3}(NCMe) 2][PF 6] ( 7) and CpFe(CO) 2X ( 8) produced Cp′Ru{P(OMe) 3}(CO)X ( 9), the selectivity at the ruthenium center was low.