A Simple Approach toward Enantiomerically Pure Fischer Carbene Complexes of Chromium and Molybdenum: Chiral Modification of the Metal Fragment

Replacing two carbonyl ligands of the common pentacarbonyl fragment by the suitable chiral biphosphite ligand 2 allows for the novel synthesis of stable chiral Fischer carbene complexes of molybdenum and chromium. In the case of the phenyl molybdenum complex 1, this exchange reaction yields complex fac-3, which can be thermally isomerized to mer-3. The thermal reaction exchange of methyl, phenyl, and alkenyl chromium carbene complexes 4a−c with ligand 2 affords directly the complexes mer-5a−c. Two of the novel complexes, fac-3 and mer-5a, have been characterized in the solid state.