Reduction of nitrite to nitric oxide and generation of reactive chalcogen species by mononuclear Fe(ii) and Zn(ii) complexes of thiolate and selenolate

Abstract

Comparative reactivity of a series of new Zn(II) and Fe(II) compounds, [(Py2ald)M(ER)] (E = S, R = Ph: M = Zn, 1a^Zn; M = Fe, 1a^Fe; E = S, R = 2,6-Me₂-C₆H₃: M = Zn, 1b^Zn; M = Fe, 1b^Fe; E = Se, R = Ph: M = Zn, 2^Zn; M = Fe, 2^Fe), and [(Py2ald)M]₂²⁺ (M = Zn, 5^Zn; M = Fe, 5^Fe) is presented. Compound 1a^Zn could react with nitrite (NO₂⁻) to produce [(Py2ald)Zn(ONO)] (3^Zn), which, upon treatment with thiols and PhSeH (proton source), could regenerate either 1a^Zn/5^Zn and 2^Zn respectively, along with the production of nitric oxide (NO) where the yield of NO increases in the order ^tBuSH ≪ PhCH₂SH < PhSH < PhSeH. In contrast to this, 1a^Fe, 2^Fe and 5^Fe could affect the direct reduction of NO₂⁻ in the absence of protons to generate NO and [{(Py2ald)(ONO)Fe}₂-μ₂-O] (8^Fe). Moreover, 8^Fe could regenerate 5^Fe and 1a^Fe/2^Fe upon treatment with 4 and 6 equiv. of PhEH (E = S/Se), respectively, along with the generation of NO. Finally, a comparative study of the mononuclear Zn(II) and Fe(II) compounds for the transfer of the coordinated thiolate/selenolate and the generation and transfer of reactive sulfur/selenium species (RES⁻, E = Se, S) to a series of organic substrates has been provided.