Reaction of nitrogen monoxide with a macrocyclic superoxorhodium(III) complex produces an observable nitratorhodium intermediate

The rapid (kgreater than or equal to10(6) M-1 s(-1)) reaction between NO and L-2(H2O)RhOO2+ (L-2 = meso-Me-6-[14]-ane-N-4) generates two strongly oxidizing, scavengeable intermediates, believed to be NO2 and L-2(H2O)-RhO2+. A mechanism is proposed whereby a peroxynitrito complex L-2(H2O)RhOONO2+ is formed first. The homolysis of O-O bond produces NO2 and L-2(H2O)Rho(2+) which were trapped with ABTS(2-) and Ni([14]aneN(4))(2+). In the absence of scavengers, the decomposition of L-2(H2O)RhOONO2+ produces both free NO3- and a rhodium nitrato complex L-2(H2O)RhONO22+, which releases NO3- in an inverse acid-dependent process. The total yield of L-2(H2O)RhONO22+ is 70%. In a minor, parallel path, NO and L-2(H2O)RhOO2+ react to give nitrite and the hydroperoxo complex L-2(H2O)RhOOH2+.