Photolytic C -Diazeniumdiolate Disassembly in the β-Diketiminate Complexes [ Me LM(O 2 N 2 CPh 3 )] (M = Fe, Co, Cu).

The reaction of [K(18-crown-6)][O 2 N 2 CPh 3 ] with [ Me LCo(μ-Br) 2 Li(OEt 2 )] ( Me L = {(2,6- i Pr 2 C 6 H 3 )NC(Me)} 2 CH) generates the trityl diazeniumdiolate complex, [ Me LCo(O 2 N 2 CPh 3 )] ( 1 ), in moderate yield. Similar metathesis reactions result in the formation of the Fe and Cu analogues, [ Me LM(O 2 N 2 CPh 3 )] (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 1 H 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, [ Me LM(NO) 2 ] (M = Co, 4 ; Fe, 5 ), along with Ph 3 CH and 9-phenylfluorene. We propose that 4 and 5 are formed via the putative hyponitrite intermediates, [ Me LM(κ 2 - O , O -ONNO)], which are formed by photoinduced homolysis of the C-N bond of the [O 2 N 2 CPh 3 ] ligand. In contrast, irradiation of complex 3 with 371 nm light, in the presence of 1 equiv of PPh 3 , led to the formation of the Cu(I) complexes, [ Me LCu(PPh 3 )], [(ArNC Me C( N O)C Me N Ar)Cu(PPh 3 )] ( 6 ), and [(ArNC Me C( N O)C Me N Ar)Cu] 2 ( 7 ), of which the latter two are products of γ-nitrosation of the β-diketiminiate ligand. Also formed in this transformation are Ph 3 CN( H )OCPh 3 , Ph 3 PO, and N 2 O, along with trace amounts of NO.