Transition metal mediated asymmetric synthesis. II. Complete resolution of (2R,5S)-(-)-Tricarbonyl[1-5-η-(2-methoxy-5-methylcyclohexadienyl)]iron(1+) hexafluorophosphate(1 -) by selective crystallization of enantiomers

The resolution of tricarbonyl(1-5-η-cylcohexadienyl)iron(1+) salts can be achieved by selective crystallization of enantiomers. The magnitude of the specific rotatory power of the title salt (1) was increased to a limiting value which was shown to correspond to optical purity, by a direct, n.m.r. method, after alkylation with dimethyl malonate. Reduction of the optically active salt defined the absolute configuration of (2R,5S)-(+ )-tricarbonyl[l-4-η-(2-methoxy-5β-methylcyclohexa-1,3-diene)]-iron(0). The chiroptical properties of the products are discussed.