Nickel complexes with N2O donor ligands:: Syntheses, structures, catalysis and magnetic studies

Two new terephthalato-bridged tetranuclear polymeric Ni-II complexes, namely [Ni4L41(mu-tp-kappa(4)-O)(H2O)(2)(mu-tP-kappa(2)-O)center dot 2C(2)H(5)OH center dot CH3OH center dot 3H(2)O (1) and [Ni4L42(mu-tP-kappa(4)-O)(H2O)2(mu-tp-kappa(2)-O)]center dot 3H(2)O (2) [L-1 = N-(3-aminopropyl)-5-bromosalicylaldirnine and L 2 = N-(3-aminopropyl)salicylaldimine], are reported along with the syntheses and structures of the dicyanoargentate-bridged polymeric complexes [Ni(L-1)(H2O)-{Ag(CN)(2)}](alpha) (3) and [Ni(L-3)(MeOH){Ag(CN)(2)}]alpha (4) [L-3 = N-(3amino-2,2-dimethylpropyl)-5-bromosalicylaldimine]. All four complexes are found to be effective heterogeneous catalysts for the epoxidation of alkenes such as styrene, a-methylstyrene and cyclohexene in the presence of tert-butyl hydroperoxide. The variable -temperature magnetic susceptibility measurements (300-2 K) of complex 1 show a fair degree of antiferromagnetic coupling between the Ni-II centers. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)