A NEW TYPE OF MIXED-LIGAND COMPLEX WITH NITROXYL RADICALS

The reaction of Cu(hfac)2 with hydroxylamines RLH(RLH = 1-hydroxy-2,2,5,5-tetramethyl-4-R-3-imidazoline; R = Me, Et, i-Pr, Ph) in inert atmosphere on heating gives rise to the partial reduction of Cu(II) to Cu(I) and yields mixed-ligand mixed-valent complexes of the composition Cu2(hfac)3(RL)2 (RL = the 2,2,5,5-tetramethyl-4-R-3-imidazolinyl-l-oxyl nitroxide; R = Me, Et, i-Pr, Ph). The reaction of Cu(hfac)2 with RLH in inert atmosphere at ambient temperature yields Cu(hfac)2(RLH). Cu(hfac)2(MeL) and [Cu(hfac)2]3(RL)2 (R = Et, i-Pr, Ph) complexes are formed by the reaction of these reagents in air. The X-ray diffraction study of catena-poly{[bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)copper(II)]-mu-(4-ethyl-2,2,5,5-tetramethyl-3-imidazolinyl-1-oxyl-O:N3)[(1,1,1,5,5,5,-hexafluoro-2,4-pentanedionato)copper(I)]-mu-(4-ethyl-2,2,5,5-tetramenthyl-3-imidazolinyl-l-oxyl-N3:O)} (monoclonic, space group P2(1)/c, a = 9.056 (3) angstrom, b = 19.622 (6) angstrom c = 26.029 (6) angstrom, beta = 100.48 (2)-degrees, V = 4548 (2) angstrom 3, Z = 4) has shown that the compound has polymeric structure with the alternation of Cu(hfac) and Cu(hfac)2 fragments bridged by EtL. The O atoms of EtL are coordinated to Cu2+ ions, while the imine N atoms of EtL are coordinated to Cu+ ions. Experimental dependence mu-eff(T) analysis for Cu2(hfac)3(RL)2 has shown that the exchange interaction in tricentered exchange clusters N-O-Cu2+-O-N is ferromagnetic (J = 7.5-25.5 cm-1), while intercluster exchange interaction is antiferromagnetic (J'z = -0.06 to -2.72 cm-1).