Unusual Bis(imido)metalloporphyrins. The synthesis of M(4-R-TPP)(NC6H4NO2)2 (M=Ru, R=H; M=Os, R=Cl) and structural study of the osmium derivative

Reaction of [Ru(TPP)]2 with p-nitrophenylazide yields Ru(TPP)(NC6H4NO2)2 in high yield as indicated by 1H NMR spectroscopy. All attempts to isolate a pure crystalline sample of this new bis(arylimido)ruthenium porphyrin were unsuccessful due to its high reactivity. Os(4-Cl-TPP)(NC6H4NO2)2 was synthesized and structurally characterized. The structure of Os(4-Cl-TPP)(NC6H4NO2)2 is similar to the previously characterized Os(TTP)(NC6H4NO2)2 but quite different from other bis(imido)osmium complexes. The imido bonds in the new bis(arylimido)osmium porphyrin are bent with average OsNC bond angles of 142.5° suggesting the imido ligands act as four-electron donors. The eclipsed orientation of the imido ligands indicates the presence of one π bonding and one non-bonding molecular orbital. In solution, 1H NMR spectroscopy indicates the structure of Os(4-Cl-TPP)(NC6H4NO2)2 is dynamic with free rotation around the imido NC and NOs bonds.