Porphyrin-Stabilized Nitrenium Dication

Abstract

An azepine-fused Ni^II -porphyrin dimer was synthesized by oxidative amination of β-β linked Ni^II -porphyrin dimer, and its N-aryl congener was synthesized by twofold Buchwald-Hartwig amination of β-to-β linked and dichlorinated Ni^II -porphyrin dimer. Oxidation of the NH congener gave neutral aminyl radical and nitrenium ion successively in a similar manner to the previously reported NH-bridged Ni^II -porphyrin dimer. Oxidation of the N-aryl congener afforded formal nitrenium dication in a single-step two-electron oxidation. Stable nitrenium dications that are isoelectronic to neutral trivalent boron compounds and tertiary carbocations are rare. The chemical stability of the nitrenium dication was improved by chlorine substitution at the most reactive β-position. The structural, optical, magnetic, electrochemical properties of these compounds were fully characterized.

Keywords: aminyl radicals; azepine; dications; nitrenium ions; porphyrin dimers.