OPTICALLY-ACTIVE TRANSITION-METAL COMPLEXES .7. IRON AND RUTHENIUM COMPLEXES WITH THE OPTICALLY-ACTIVE CYCLOPENTADIENYL LIGAND PCP - SYNTHESES AND LIGAND-EXCHANGE REACTIONS

The optically active complexes [PCpFe(CO)(2)](2) and [PCpRu(CO)(2)](2) (PCp = pinene-fused cyclopentadiene) have been converted into half-sa ndwich complexes PCpM(CO)(2)X (X = Cl, Br, I, CH3, COMe, COPh COMes) b y either oxidative or reductive methods. Ligand exchange of one of the diastereotopic carbonyl ligands for a Lewis base L (L = tertiary phos phine or phosphite) generates diastereomeric complexes PCpML(CO)X with pseudo-tetrahedral chirality at the metal centre. Diastereomeric rati os increase with increasing steric bulk of the new ligand, with upper limits of 64% de. With M = Ru, both photochemical and thermal methods of ligand exchange are possible for X = halogen, giving rise not only to different but also reverse ratios of diastereomers. Optical inducti ons by thermal ligand exchange are significantly higher and are shown to be of thermodynamic origin.