Nitrosyl–nitro redox couples with metal phthalocyanines: synthesis and characterization of nitro derivatives of cobalt and iron phthalocyanine, dioxygen activation, oxygen-atom transfer and stoichiometric and catalytic oxidation of terminal olefins

Abstract

The complexes [Co(pc)(NO₂)(py)]·dce, [Co(pc)(NO₂)(py)]·thf, and [Fe(pc)(NO₂)(py)](pc = phthalocyaninate, py = pyridine, dce = 1,2-dichloroethane and thf = tetrahydrofuran) have been isolated as stable crystalline materials. Their molecular and electronic structures have been investigated by IR and UV/VIS spectra, X-ray powder patterns, thermogravimetric and magnetic susceptibility measurements and Mössbauer spectra. The complexes should be regarded as six-co-ordinate low-spin cobalt(III) and iron(III) species. Reference is also made to their corresponding five-co-ordinate nitrosyl derivatives, [Co(pc)(NO)] and [Fe(pc)(NO)]. The Co(pc)– and Fe(pc)–NO/NO₂ systems have been studied with regard to their dioxygen activation and oxygen-atom-transfer reactions, in the oxidation of terminal olefins to the corresponding methyl ketones. Whereas oxidation with the Co(pc)–NO/NO₂ redox couple is nearly stoichiometric, catalytic and selective oxidation occurs with the parallel Fe(pc) system.