A Mononitrosyl Diiron(II) Compound Catalyzes the Reduction of Nitrite to Nitric Oxide

A diiron(II) compound, [Fe2(HPTP)(NCS)3(DMF)] (1), mediated the direct reduction of nitrite (NO2-) to nitric oxide (NO) in 100% yield and allowed the generation of a mononitrosyl diiron(II) compound, [Fe2(HPTP)(NCS)3(NO)] (2). Compound 2 is a rare [FeII{FeNO}7] species, which featured Fe-N and N-O distances of 1.768(4) Å and 1.142(5) Å, respectively, <Fe-N-O angle of 158.2(4)°, νNO = 1765 cm-1, EPR signal centered at <g> = 2.00 characteristic of an S = 1/2 ground state, and released NO to regenerate 1 within 36 h in DMF. Interestingly, 2 could also reduce NO2- to NO in 100% yield, and thus the formation of 2 did not inhibit the quantitative reduction of NO2- to NO by 1. It was also observed that the redox reaction of PhS- with the Fe(III) centers, generated after the reduction of NO2- to NO, to regenerate 1 and PhS-SPh was much more facile than the reaction of the in situ generated 2 with PhS- to produce the dinitrosyl iron complex (DNIC), [Fe(SPh)2(NO)2]1-. The reduction of NO2- to NO by 1 and 2 has been made catalytic with a TON of 20 and 16, respectively. Compound 2 is the only [FeII{FeNO}7] compound that can catalyze the reduction of NO2- to NO.