Ruthenium(II) porphyrin catalyzed imine aziridination and crystal structures of (meso-tetrakis(pentafluorophenyl)porphyrinato)ruthenium(II) complexes containing PhN=CH(p-ClPh), CPh2, and pyridine ligands

A (meso-tetrakis(pentafluorophenyl)porphyrinato)ruthenium(II) complex of PhN=CH(p-ClPh) is prepared by reacting [Ru(F-20-TPP)(CO)] (1) with a benzene solution of N-(p-chlorobenzylene)aniline. The crystal structure of {Ru(F-20-TPP)(CO) [PhN=CH(p-ClPh)]} (10) shows the coordinated imine ligand in a cis configuration. Comparison with X-ray crystal-lographic data for [Ru(F-20-TPP)(PY)(2)] (11) revealed the axial Ru-N bond length of the imine complex (2.203 Angstrom) to be slightly longer than that of the bis(pyridine) complex (2.108 Angstrom). Spectral and structural data revealed the Ru-N(imine) bond to have single-bond character, and the Ru=C bond in [Ru(F-20-TPP)(CPh2)] (7) has a bond distance of 1.842 Angstrom, indicative of multiple-bond character. In the presence of diazo compounds, {Ru(F-20-TPP)(CO)[PhN=CH(p-ClPh)]} (10) and other related complexes mediated diastereoselective imine aziridination with product yields up to 86%. The mechanism is suggested to involve activation of the imine and diazo compounds by the ruthenium(II) porphyrin catalyst followed by nucleophilic addition of the imine to the diazo ester and subsequent cyclization to give the aziridine.