Synthesis of a tetramethoxy and an amphiphilic tetrahydroxy hemilabile N,P,N-ligand. Coordination behavior towards rhodium(I) and application to hydroformylation of styrene or hydrogenation of trans-cinnamaldehyde

A tetramethoxy hemilabile N,P,N-ligand and the corresponding amphiphilic tetrahydroxy ligand have been synthesized via ortho-lithiation of N,N-bis(2-methoxyethyl)-benzenamine and N,N-bis[2-(methoxymethoxy)ethyl]-benzenamine, respectively. The coordination behavior of the ligands towards rhodium(I) in solution was investigated and, according to 1H-, 13C- and 31P-NMR data, at room temperature both ligands are coordinated to the metal in a N,P,N-tridentate mode without any Rh–O interaction, whereas at low temperature a P–Rh–N bridged dimeric species was also found together with the most favored tridentate monomer. The rhodium complex of the former ligand was applied to hydroformylation of styrene and the complex of the latter ligand was evaluated in the hydrogenation of trans-cinnamaldehyde.