Structural, Magnetic and Catalytic Properties of a Self-Recognized μ-Oxo-Bridged Diiron(III) Bis(benzimidazole) Complex

The inherent nonplanarity and C2 symmetry of the dimethyl-substituted bis(benzimidazole) ligand (Me2BBZ)
results in two distinct atropisomers that, when separated, have been suggested to have potential for chiral recognition
and catalysis. Here is reported the synthesis and characterization of a diiron μ-oxo-bridged bis(benzimidazole)
complex, 1, that provides indirect support for this hypothesis. Dimerization of a racemic solution of iron−Me2BBZ monomers via the μ-oxo bridge yields (+,+) and (−,−) diastereomers whose complementary association
can be attributed to the inherent sidedness of the metal−Me2BBZ interaction surface, and to the differences in
the torsional angles of the phenyl(benzimidazole) units (34°) and the Schiff base linkages (54°). These results
highlight the steric differences between the phenyl(benzimidazole) and Schiff-base portions of the ligand, features
that could be important in the chiral recognition of ligands and in differentiating substrate trajectories as required
for asymmetric catalysis. For completeness, studies of 1 in the catalytic epoxidation of styrene are also reported.