STABILIZATION OF A NITROXIDE WITH A BETA-HYDROGEN BY METALS - STRUCTURE AND MAGNETIC-PROPERTIES OF ADDUCTS OF N-OXY-N-TERT-BUTYL-(2-PYRIDYL)PHENYLMETHANAMINE WITH MN(II), NI(II), AND CO(II) HEXAFLUOROACETYLACETONATES

Transition metal hexafluoroacetylacetonate complexes of a nitroxide be aring a beta-hydrogen, N-oxy-N-tert-butyl-(2-pyridyl)phenylmethanamine (2-PyBNO), were synthesized and characterized. X-ray analysis of the metal-nitroxide complexes M(2-PyBNO)(hfac)(2), where M(II) = Mn (1), C o (2), and Ni (3), revealed a distorted octahedral coordination geomet ry for the three metal centers. All complexes are isostructural and tr iclinic, P (1) over bar. Crystal data: 1, a = 7.996(2) Angstrom, b = 1 1.601(2) Angstrom, c = 17.105(4) Angstrom, alpha = 91.287(1)degrees, b eta = 100.409 (1)degrees, gamma = 101.196(1)degrees, Z = 2; 2, a = 7.9 32(4) Angstrom, b = 11.477(6) Angstrom, c = 17.395(8) Angstrom, alpha = 92.780(1)degrees beta = 101.330(1)degrees, gamma = 101.040(1)degrees , Z = 2; 3, a = 7.862(5) Angstrom, b = 11.353(7) Angstrom, c = 17.423( 10) Angstrom, alpha = 93.583(1)degrees, beta = 101.120(1)degrees gamma = 100.154(1)degrees, Z = 2. SQUID magnetic susceptibility measurement s over a temperature range of 2-300 Ii for complexes I and 3 showed an tiferromagnetic coupling between the nitroxide and metal nucleus unpai red electrons, with -J = 57(1) cm(-1) for 1 and -J = 181(15) cm(-1) fo r 3. EPR spectra of frozen solutions (115 Ii) show a weak signal cente red at g = 2.000 for 1 and a doubler with g(1) = 2.299, g(2) = 2.243, and g(3) = 2.193 for 3.