Intramolecular rearrangement for regioselective complexation by intramolecular CH/π interaction in a hydrophobic cavity of a ruthenium coordination sphere

A Ru^II complex with a hydrophobic cavity formed from two 1-naphthoylamide groups was prepared. Its reactions with β-diketones gave β-diketonato complexes in which hydrophobic π-π or CH/π interactions were confirmed by NMR spectroscopy and X-ray crystallography. In the case of the asymmetric β-diketone benzoylacetone, an isomer with a CH/π interaction was afforded as the sole product owing to thermodynamic control. The reaction was found to involve a novel intramolecular rearrangement from the phenyl-included isomer to the methyl-included one without rupture of Ru-β-diketonato coordination bonds (activation energy 52 kJ mol ^-1). This indicates that CH/π interactions can be more favored thermodynamically than π-π interactions in a suitable hydrophobic environment.