Inorganic Chemistry, Vol.37, No.7, 1454-1457, 1998
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 bearing 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), Co (2), and Ni (3), revealed a distorted octahedral coordination geometry for the three metal centers. All complexes are isostructural and triclinic, P (1) over bar. Crystal data : 1, a = 7.996(2) Angstrom, b = 11.601(2) Angstrom, c = 17.105(4) Angstrom, alpha = 91.287(1)degrees, beta = 100.409 (1)degrees, gamma = 101.196(1)degrees, Z = 2; 2, a = 7.932(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 measurements over a temperature range of 2-300 Ii for complexes I and 3 showed antiferromagnetic coupling between the nitroxide and metal nucleus unpaired electrons, with -J = 57(1) cm(-1) for 1 and -J = 181(15) cm(-1) for 3. EPR spectra of frozen solutions (115 Ii) show a weak signal centered 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.