Structural, magnetic and catalytic properties of a self-recognized mu-oxo-bridged diiron(III) bis(benzimidazole) complex

The inherent nonplanarity and C-2 symmetry of the di methyl-substituted bis (benzimidazole) ligand (Me(2)BBZ) results in two distinct atropisomers that , when separated, have been suggested to have potential for chiral recognit ion and catalysis. Here is reported the synthesis and characterization of a diiron mu -oxo-bridged bis(benzimidazole) complex, 1, that provides indire ct support for this hypothesis. Dimerization of a racemic solution of iron- Me-2-BBZ monomers via the mu -oxo bridge yields (+,+) and (-,-) diastereome rs whose complementary association can be attributed to the inherent sidedn ess of the metal-Me(2)BBZ interaction surface, and to the differences in th e torsional angles of the phenyl(benzimidazole) units (34 degrees) and the Schiff base linkages (54 degrees). These results highlight the steric diffe rences between the phenyl(benzimidazole) and Schiff-base portions of the li gand, features that could be important in the chiral recognition of ligands and in differentiating substrate trajectories as required for asymmetric c atalysis. For completeness, studies of 1 in the catalytic epoxidation of st yrene are also reported.