An electrochemical investigation of intermediates and processes involved in the catalytic reduction of dinitrogen by [HIPTN3N]Mo (HIPTN3N = (3,5-(2,4,6-i-Pr3C6H2)(2)C6H3NCH2CH2)(3)N)

作者：Munisamy Thiruvengadam; Schrock Richard R^*

来源：Dalton Transactions, 2012, 41(1): 130-137.

DOI：10.1039/c1dt11287b

The redox properties of [HIPTN3N]Mo complexes (where HIPTN3N = (3,5-(2,4,6-i-Pr3C6H2)(2)-C6H3NCH2CH2)(3)N) involved in the catalytic dinitrogen reduction cycle were studied using cyclic voltammetry in fluorobenzene with Bu4NPF6 as the electrolyte. MoN2 (Mo = [HIPTN3N]Mo, E-1/2 = -1.96 V vs. Fc(+)/Fc at a Pt electrode), Mo N (E-1/2 = -2.68 V vs. Fc(+)/Fc (Pt)), and [Mo(NH3)]BAr'(4) (Ar' = 3,5-(CF3)(2)C6H3, E-1/2 = -1.53 V vs. Fc(+)/Fc (Pt)) each undergo a chemically reversible one-electron reduction, while [Mo=NNH2]BAr'(4) (E-1/2 = -1.50 V vs. Fc(+)/Fc (Pt)) and [Mo=NH]BAr'(4) (E-1/2 = -1.26 V vs. Fc(+)/Fc (Pt)) each undergo a one-electron reduction with partial chemical reversibility. The acid employed in the catalytic reduction, [2,4,6-collidinium]BAr'(4), reduces irreversibly at -1.11 V vs. Fc(+)/Fc at Pt and at -2.10 V vs. Fc(+)/Fc at a glassy carbon electrode. The reduction peak potentials of the Mo complexes shift in the presence of acids. For example, the reduction peak for MoN2 in the presence of [2,4,6-collidinium]BAr'(4) at a glassy carbon electrode shifts positively by 130 mV. The shift in reduction potential is explained in terms of reversible hydrogen bonding and/or protonation at a nitrogen site in Mo complexes. The significance of productive and unproductive proton-coupled electron transfer reactions in the catalytic dinitrogen reduction cycle is discussed.

• 出版日期2012