UC Santa Barbara

The reaction of [K(18-crown-6)][O₂N₂CPh₃] with [^MeLCo(μ-Br)₂Li(OEt₂)] (^MeL = {(2,6-ⁱPr₂C₆H₃)NC(Me)}₂CH) generates the trityl diazeniumdiolate complex, [^MeLCo(O₂N₂CPh₃)] (1), in moderate yield. Similar metathesis reactions result in the formation of the Fe and Cu analogues, [^MeLM(O₂N₂CPh₃)] (Fe, 2; Cu, 3), which can also be isolated in moderate yields. Complexes 1-3 were characterized by ultraviolet-visible (UV-vis) spectroscopy, and their solid-state structures were determined by X-ray crystallography. These complexes were further characterized via ¹H NMR spectroscopy (in the case of 1 and 2) or EPR spectroscopy (in the case of 3). Irradiation of complexes 1 and 2 with 371 nm light generates the known dinitrosyl complexes, [^MeLM(NO)₂] (M = Co, 4; Fe, 5), along with Ph₃CH and 9-phenylfluorene. We propose that 4 and 5 are formed via the putative hyponitrite intermediates, [^MeLM(κ²-O,O-ONNO)], which are formed by photoinduced homolysis of the C-N bond of the [O₂N₂CPh₃] ligand. In contrast, irradiation of complex 3 with 371 nm light, in the presence of 1 equiv of PPh₃, led to the formation of the Cu(I) complexes, [^MeLCu(PPh₃)], [(ArNC^MeC(NO)C^MeNAr)Cu(PPh₃)] (6), and [(ArNC^MeC(NO)C^MeNAr)Cu]₂ (7), of which the latter two are products of γ-nitrosation of the β-diketiminiate ligand. Also formed in this transformation are Ph₃CN(H)OCPh₃, Ph₃PO, and N₂O, along with trace amounts of NO.