Formation of Stable NiIII N‐Confused Porphyrins Aided by a 3‐Ethoxy Group

Abstract

We report the synthesis, characterization and reactivities of two stable Ni(III) N-confused porphyrin (NCP) complexes. Metalation of 3-OEt NCP 1 with NiCl 2 . 6H 2 O in CHCl 3 /EtOH gave 3-OEt Ni(II) NCP 3 initially, which was easily oxidized by air to form Ni(III) complex of NCP inner C-oxide 4 . Bis-ethoxy-modified Ni(III) complex 5 was synthesized by oxidation of 3 with PIFA in ethanol and CHCl 3 . Structures of 4 and 5 were determined by single-crystal X-ray diffraction analysis. An unusual long Ni(III)-C bond (2.170 (9) Å) was observed in 4 . The g-factor (g > 2.1) observed in the EPR spectra of 4 and 5 further confirmed that they are paramagnetic Ni(III) complexes. Comparative experiments showed that the 3- ethoxy group plays an important role in the formation of 4 and 5 . Reduction of 4 and 5 with NaBH 4 regenerated complex 3 .