Nickel complexes and cobalt coordination polymers with organochalcogen (S, Se) ligands bearing an N-methylimidazole moiety:: Syntheses, structures, and properties

The organochalcogen ligands (S, Se) derived from 3-methylimidazole-2-thione/selone groups mbit (2a), mbis (2b), ebit (2c), and ebis (2d) [mbit = 1,1'-methylenebis(1,3-dihydro-3-methyl-2H-imidazole-2-thione), mbis = 1,1'-methylene-bis(1,3-dihydro-3-methyl-2H-imidazole-2-selone), ebit = 1,1.'-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H-imidazole-2-thione), ebis = 1,1'-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H-imidazole-2-selone)] were synthesized and characterized. Mononuclear Ni-II complexes NiBr(2)mbit (3a), NiBr(2)mbis (3b), NiBr(2)ebit (3c), and NiBr(2)ebis (3d) were obtained by the reactions of Ni(PPh3)(2)Br-2 with 2a, 2b, 2c, and 2d, respectively. However, when the corresponding ligands 2a, 2b, 2c, and 2d were treated with CoCl2 in thf solution Coll 1D coordination polymers (CoCl(2)mbit)(n) (4a), (CoCl(2)mbis)(n) (4b), (CoCl(2)ebit)(n) (4c), and (CoCl(2)ebis)(n) (4d) were obtained. All compounds were fully characterized by IR spectroscopy and elemental analysis. The crystal structures of 2c, 3a, 3b, 3c, 4a, 4b, and 4c were determined by X-ray crystallography. The local geometry around the nickel atom in complexes 3ac was distorted tetrahedron with coordinated S(Se) and two Br atoms, and the organochalcogen ligands form an eight- or a nine-membered ring with the nickel atom included, The cobalt atom coordination polymers 4a and 4b coexist as left-handed and right-handed helical chains, but 4c formed a zig-zag chain with a CH3CN solvent molecule taken up in the channel structure. After activation with methylaluminoxane (MAO), the nickel complexes exhibited high activities for addition polymerization of norbornene (1.42 x 10(8) gPNB-mol(-1)Nih(-1) for 3a). The effects of the Al/Ni ratio, reaction temperature, and reaction time to norbornene polymerization were also investigated. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).