Mapping The Pathway To Organocopper(Ii) Complexes Relevant To Atom Transfer Radical Polymerization

The rare organocopper(II) complex [Cu(Me(6)tren)(CH2CN)](+) (Me(6)tren = tris(2-(dimethylamino)ethyl)amine) has emerged as an important model of potential byproducts in copper-catalyzed-atom transfer radical polymerization. This complex has been generated by controlled potential electrolysis of [Cu(Me(6)tren)(NCMe)](2+) in the presence of BrCH2CN. Time-resolved UV-vis and continuous wave and pulse electron paramagnetic resonance (EPR) spectra identified [Cu(Me(6)tren)Br](+) as an intermediate. Hyperfine sublevel correlation and electron nuclear double resonance spectroscopy of samples at different timepoints reveal signals that are assigned to a C-bound cyanomethylate ligand, with distinct N-14 and H-1 hyperfine coupling constants in comparison with the corresponding N-bound acetonitrile and bromido complexes. The experimental EPR data are supported by density functional theory calculations to understand how the geometries of the species involved produce distinct spectroscopic signatures, and a clear picture of how this unusual organocopper(II) complex is formed has emerged.