Photolytic C-Diazeniumdiolate Disassembly in the & beta;-Diketiminate Complexes [(LM)-L-Me(O2N2CPh3)] (M = Fe, Co, Cu)

The reaction of [K(18-crown-6)][O2N2CPh3] with [(LCo)-L-Me(& mu;-Br)(2)Li(OEt2)] (L-Me = {(2,6-(Pr2C6H3)-Pr- i )NC(Me)}(2)CH) generatesthe trityl diazeniumdiolate complex, [(LCo)-L-Me(O2N2CPh3)] (1), in moderate yield.Similar metathesis reactions result in the formation of the Fe andCu analogues, [(LM)-L-Me(O2N2CPh3)] (Fe, 2; Cu, 3), which can also be isolatedin moderate yields. Complexes 1-3 were characterized by ultraviolet-visible (UV-vis)spectroscopy, and their solid-state structures were determined byX-ray crystallography. These complexes were further characterizedvia H-1 NMR spectroscopy (in the case of 1 and 2) or EPR spectroscopy (in the case of 3). Irradiationof complexes 1 and 2 with 371 nm light generatesthe known dinitrosyl complexes, [(LM)-L-Me(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, [(LM)-L-Me(& kappa;(2)-O,O-ONNO)], which are formed by photoinduced homolysis of the C-Nbond of the [O2N2CPh3] ligand. Incontrast, irradiation of complex 3 with 371 nm light,in the presence of 1 equiv of PPh3, led to the formationof the Cu(I) complexes, [(LCu)-L-Me(PPh3)], [((ArNCC)-C-Me(NO)C-Me NAr)Cu(PPh3)] (6), and [((ArNCC)-C-Me(NO)C-Me NAr)Cu](2) (7), of which the latter two are products of & gamma;-nitrosation ofthe & beta;-diketiminiate ligand. Also formed in this transformationare Ph3CN(H)OCPh3, Ph3PO, and N2O, along with trace amounts of NO. Photolysis of the C-diazeniumdiolatecomplexes,[(LM)-L-Me(O2N2CPh3)] (L-Me = {(2,6-(Pr2C6H3)-Pr- i )NC(Me)}(2)CH; M = Fe, Co), resultsin complete disassembly of their C-diazeniumdiolateligands to yield [(LM)-L-Me(NO)(2)] via a proposedhyponitrite intermediate.

Automated summary

The reaction of [K(18-crown-6)][O2N2CPh3] with [(LCo)-L-Me(& mu;-Br)(2)Li(OEt2)] generates the trityl diazeniumdiolate complex, [(LCo)-L-Me(O2N2CPh3)] (1). Similar metathesis reactions result in the formation of the Fe and Cu analogues, [(LM)-L-Me(O2N2CPh3)] (Fe, 2; Cu, 3). Complexes 1-3 were characterized by spectroscopy and their structures were determined by X-ray crystallography. Photolysis of the C-diazeniumdiolate complexes, [(LM)-L-Me(O2N2CPh3)] (L-Me = {(2,6-(Pr2C6H3)-Pr- i )NC(Me)}(2)CH; M = Fe, Co), results in the disassembly of their C-diazeniumdiolate ligands to yield [(LM)-L-Me(NO)(2)] via a proposed hyponitrite intermediate.