Diastereomeric (alkyne)pentacarbonyldicobalt complexes containing the chiral phosphine ligand (R)-(+)-Glyphos have been synthesized and separated chromatographically. The isolated, optically pure diastereomeric complexes have been employed in intermolecular Pauson-Khand reactions, using anhydrous N-methylmorpholine N-oxide as the reaction promoter under mild conditions, to give high yields of cyclopentenone products in good to excellent enantiomeric excesses.