Reduction of the {Co(NO)}(8) cobalt-nitrosyl N-confused porphyrin (NCP) [Co(CTPPMe)(NO)] (1) produced electron-rich {Co(NO)}(9) [Co(CTPPMe)(NO)][Co(Cp*)2 ] (2), which was necessary for NO-to-N2 O conversion. Complex 2 was NO-reduction-silent in neat THF, but was partially activated to a hydrogen-bonded species 2⋅⋅⋅MeOH in THF/MeOH (1:1, v/v). This species coupling with 2 transformed NO into N2 O, which was fragmented from an [N2 O2 ]-bridging intermediate. An intense IR peak at 1622 cm(-1) was ascribed to ν(NO) in an [N2 O2 ]-containing intermediate. Time-course ESI(-) mass spectra supported the presence of the dimeric [Co(NCP)]2 (N2 O2 ) intermediate. Five complete NO-to-N2 O conversion cycles were possible without significant decay in the amount of N2 O produced.

Successful synthesis and characterization of the six-coordinated complex [Ru(STTP)(CO)Cl] (1; STTP = 5,10,15,20-tetratolyl-21-thiaporphyrinato) allowed the development of the coordination chemistry of ruthenium-thiaporphyrin through dechlorination and metathesis reactions. Accordingly, [Ru(II)(STTP)(CO)X] (X = NO(3)(-) (2), NO(2)(-) (3), and N(3)(-) (4)) was synthesized and analyzed by single-crystal X-ray structural determination and NMR, UV-vis, and FT-IR spectroscopic methods. An independent reaction of STPPH and [Ru(COD)Cl(2)] led to [Ru(III)(STTP)Cl(2)] (5), which possessed a higher-valent Ru(III) center and exhibited good stability in the solution state. This stability allowed reversible redox processes in a cyclic voltammetric study. Reactions of [Ru(S(2)TTP)Cl(2)] (S(2)TTP = 5,10,15,20-tetratolyl-21,23-dithiaporphyrinato) with AgNO(3) and NaSePh, also via the metathesis strategy, resulted in novel dithiaporphyrin complexes [Ru(II)(S(2)TTP)(NO(3))(2)] (6) and [Ru(0)(S(2)TTP)(PhSeCH(2)SePh)(2)] (7), respectively. The structures of 6 and 7 were corroborated by X-ray crystallographic analyses. Complex 7 is an unprecedented ruthenium(0)-dithiaporphyrin with two bis(phenylseleno)methanes as axial ligands. A comparison of the analyses of the crude products from reactions of NaSePh and CH(2)Cl(2) with or without [Ru(S(2)TTP)Cl(2)], further supported by UV-vis spectral changes under stoichiometric reactions between [Ru(S(2)TTP)Cl(2)] and NaSePh, suggested a reaction sequence in the order of (1) formation of a putative [Ru(II)(S(2)TTP)(SePh)(2)] intermediate, followed by (2) the concerted formation of PhSe-CH(2)Cl and simultaneously a reduction of Ru(II) to Ru(0) and finally (3) nucleophilic substitution of PhSeCH(2)Cl by excess PhSe(-), resulting in PhSeCH(2)SePh, which readily coordinated to the Ru(0) and completed the formation of bis(phenylseleno)methane complex 7.

Facile nitrite reduction was achieved using [Fe(II)(HCTPPH)NO] as the starting compound to react with NaNO(2). Stoichiometric studies allow the isolation of both {Fe(NO)}(6) and {Fe(NO)}(7) nitrosyl complexes and provide insight into the proton and electron transfer processes during the nitrite reduction. Treating [Fe(CTPP)NO] with acid or oxidizing [Fe(HCTPP)NO] with AgClO(4) yields intermediate [Fe(HCTPP)NO](+). The conversion cycles starting from {Fe(NO)}(6) [Fe(CTPP)NO] to {Fe(NO)}(6) [Fe(HCTPP)NO][ClO(4)] then to {Fe(NO)}(7) [Fe(HCTPP)NO] and vice versa were constructed.