Synthesis and molecular structures of nitrosoarene metalloporphyrin complexes of ruthenium

Abstract

Several new ruthenium porphyrins containing nitrosoarene ligands have been synthesized and characterized by IR and ¹H NMR spectroscopy, and by single-crystal X-ray crystallography. Bis-nitrosoarene complexes of the form (por)Ru(ArNO)₂ (Ar = aryl group; por = TPP, TTP; TPP = tetraphenylporphyrinato dianion, TTP = tetratolylporphyrinato dianion) were prepared in good yields from the reaction of the nitrosoarenes with (por)Ru(CO). The IR spectra of the complexes (as KBr pellets) display new bands in the 1346–1350 cm⁻¹ region due to ν_NO. Reactions of the (por)Ru(ArNO)₂ complexes with excess pyridine and 1-methylimidazole produce the mono-nitrosoarene complexes (por)Ru(ArNO)(py) and (por)Ru(ArNO)(1-MeIm), respectively. The IR spectra of these mono-nitrosoarene complexes reveal a lowering of ν_NO by 14–44 cm⁻¹, a feature consistent with the replacement of one of the π-acid ArNO ligands with the more basic pyridine and 1-MeIm ligands. The solid-state molecular structures of two members of each of the three classes of compounds, namely (por)Ru(ArNO)₂, (por)Ru(ArNO)(py) and (por)Ru(ArNO)(1-MeIm) were determined by single-crystal X-ray diffraction, and reveal the N-binding mode of the ArNO ligands.