In pursuit of a stable peroxynitrite complex—NO x ( x=1–3) derivatives of Tp t-Bu,MeCo

Abstract

Reaction of Tp t-Bu,MeCo(O 2) with NO yielded a mixture of Tp t-Bu,MeCo(NO 2) ( 2) and Tp t-Bu,MeCo(NO 3) ( 3) rather than the desired stable peroxynitrite complex Tp t-Bu,MeCo(OONO). Complexes 2 and 3 have been independently synthesized and characterized, including a crystal structure determination of 2. Reaction of Tp t-Bu,MeCo(N 2) with NO yielded the paramagnetic cobalt nitrosyl Tp t-Bu,MeCo(NO) ( 4), a {Co(NO)} 9 complex that has also been structurally characterized. Exposure of 4 to O 2 in solution yielded 2 exclusively, while the major product of the same reaction carried out in the solid state was 3. A labile peroxynitrite complex is considered a likely intermediate in these reactions; indeed, in situ IR spectroscopy revealed the formation of a intermediate tentatively assigned as such in the reaction of Tp t-Bu,MeCo(O 2) with NO at −78 °C.