Diastereoselective Formation of Ruthenium-Isocyanide and -Acetylide Complexes with Planar-Chiral Cyclopentadienyl-Phosphine Ligands

The reaction of ruthenium complexes [(η5:η1-2-Me-4-R-C5H2CO2CH2CH2PPh2)Ru(PR‘3)(NCMe)][PF6] (R = Me, Ph, But; R‘ = Ph, Me, OPh) possessing planar-chiral cyclopentadienyl-phosphine ligands with tert-butyl isocyanide resulted in the diastereoselective formation of
ruthenium-isocyanide complexes (up to >99% de) under kinetic control. The reaction with
phenylacetylene followed by treatment with alumina gave acetylide complexes diastereoselectively (up to >99% de). The configuration of the products was determined by X-ray
analyses as well as NOE measurements. In both reactions, the stereochemistry of the
ruthenium atom in the substrate did not influence the diastereoselectivity of the products,
although the substituent on the cyclopentadienyl ring and the phosphorus ligands on the
ruthenium atom showed steric effects on the selectivity.