ZINC COORDINATION-COMPOUNDS WITH IMIDAZOLINE AND IMIDAZOLE DONOR LIGANDS

By reaction of the two bidentate bisimidazoline ligands 1,2-bis(2-imidazoline-2-yl)ethan (BIE) and 1,2-bis(2-imidazoline-2-yl)benzene (BIB) with zinc bromide under various reaction conditions the complexes [ZnBr2(BIE)] (1), [ZnBr2(BIB)] (2), [Zn(BIE)2]Br2 (3) and [Zn(BIB)2](BPh4)2 (4) were synthesized and characterized. In all compounds the zinc atom is tetrahedrally coordinated, either by a bidentate ligand and two bromine ligands, or by two of the chelate ligands. Zn-N-bond distances for 1 - 4 range from 1.966(2) to 2.013(3) angstrom and the Zn-Br distances from 2.372(1) to 2.403(1) angstrom. [3-(imidazole-1-yl)-1-oxopropyl]benzene (IOB) was prepared as a novel imidazole ligand which carries a keto-O atom in 1,5-position to the pyridine-N atom. The zinc in [ZnCl2(IOB)2] (5) is coordinated by two ligands and two Cl atoms forming a distorted tetrahedral ZnN2Cl2 unit (Zn-N: 2.013(3) and 2.029(2) angstrom; Zn-Cl: 2.226(1) and 2.242(1) angstrom). The colourless compounds 1 - 5 were characterized by IR, H-1-NMR, X-ray absorption spectra and single-crystal X-ray structure analysis. Space groups and structural data: 1: P2(1)/c, a = 7.717(2), b = 22.814(5), c = 8.026(2) angstrom, 8 = 1 17.58(2)degrees (140 K), R = 0.0283; 2: Cc, a = 11.831(3), b = 11.677(1), c = 11.846(1) angstrom, beta = 114.55(2)degrees, R = 0.0237; 3: P4(2)/n, a = 7.931(1), c = 16.945(1) angstrom, R = 0.0312; 4: P2(1)/c, a = 18.666(2), b = 16.615(2), c = 19.786(2) angstrom, beta = 99.17(1)degrees, R = 0.0472; 5: P2(1)/c, a = 9.173(2), b = 9.230(1), c = 28.357(3) angstrom, beta = 96.63(1)degrees, R = 0.0317.