NO and NO Release from the Trityl Diazeniumdiolate Complexes [M(ONCPh)] (M = Fe, Co).

Reaction of MBr with 3 equiv of [K(18-crown-6)][ONCPh] generates the trityl diazeniumdiolate complexes [K(18-crown-6)][M(ONCPh)] (M = Co, ; Fe, ) in good yields. Irradiation of and using 371 nm light led to NO formation in 10 and 1% yields (calculated assuming a maximum of 6 equiv of NO produced per complex), respectively. NO was also formed during the photolysis of , in 63% yield, whereas photolysis of led to the formation of NO, as well as PhCN()OCPh, in 37 and 5% yields, respectively. These products are indicative of diazeniumdiolate fragmentation via both C-N and N-N bond cleavage pathways. In contrast, oxidation of complexes and with 1.2 equiv of [Ag(MeCN)][PF] led to NO formation but no NO formation, suggesting that diazeniumdiolate fragmentation occurs exclusively via C-N bond cleavage under these conditions. While the photolytic yields of NO are modest, they represent a 10- to 100-fold increase compared to the previously reported Zn congener, suggesting that the presence of a redox-active metal center favors NO formation upon trityl diazeniumdiolate fragmentation.