Synthesis and structural characterization of copper(II) complexes of pincer ligands derived from benzimidazole

A few pincer-type ligands, 1,3-bis(2 '-benzimidazolyl) benzene (L-1), 2,6-bis(2 '-benzimidazolyl)pyridine (L-2), and their N-alkylated derivatives were prepared and characterized by IR and H-1 NMR spectroscopy. The N-alkylated benzimidazolyl ligands, 2,6-bis(N-benzylbenzimidazolyl) pyridine (L-3), 2,6-bis(N-allylbenzimidazolyl) pyridine (L-4), and 1,3-bis( N-allylbenzimidazolyl) benzene (L-5) form 1 : 1 complexes with copper nitrate. X-ray diffraction showed that [Cu(NO3)(MeOH)(L-4)](NO3) (7) and [Cu(NO3)(2)(L-3)] (8) are mononuclear complexes, whereas [Cu(NO3)(2)(L-5)]center dot 2DMF (9) exhibits one-dimensional zigzag motif. The chain consists of mutually bridged Cu(NO3)(2) and L-5 ligand. Crystal data: 7, triclinic, P (1) over bar, a = 9.035(3)A, b = 11.149(4) angstrom, c = 14.664(5) angstrom, alpha = 104.856(5)degrees, beta = 99.635(5)degrees, gamma = 99.409(5)degrees, V = 1374.2(8)angstrom(3), Z = 2, and R-1 = 0.0666, wR(2) =0.1753; 8, monoclinic, Cc, a = 12.979(5) angstrom, b = 14.343(5) angstrom, c = 16.966(6) angstrom, beta = 109.958(6)degrees, V = 2968.9( 18) angstrom(3), Z 4, and R1 = 0.0582, wR(2) = 0.1352; 9, monoclinic, P2(1)/c, a = 17.278(6) angstrom, b = 15.234(5) angstrom, c = 16.161(5) angstrom, beta = 111.221(5)degrees, V = 3965(2)angstrom(3), Z = 4, and R-1 = 0.0658, wR(2) = 0.1612.