Polyhedron Vol. 12, No.9, pp. 1083-1092, 1993 Printed in Great Britain 0277-5387193 $6.00+ .W 0 1993 Pergamon Press Ltd zyxwvutsr NICKEL(II) COMPLEXES OF 1,7-BIS(BENZIMIDAZOE2-YL)-2,6-DITHIAHEPTANE (BBDHP). CRYSTAL AND MOLECULAR STRUCTURE OF fNi2(BBDHP)&Cl)~ JCl~ * 5H,O l 2EtOH AND Ni(BBDHP)Br, l EtOH l 1/2Bu*OH R. CARBALLO” and A. CASTIREIRASP Departamento de Quimica Inorginica, Universidad de Santiago de Compostela, E- 15706 Santiago de Compostela, Spain and W. HILLERg and J. STR;iHLE Institut fiir Anorganische Chemie der Universitiit Tiibingen, Auf der Morgenstelle 18, D-7400 Tiibingen, Germany zyxwvutsrqponmlkjihgfedcbaZYXWVU (Received 15 October 1992 ; accepted 2 December 1992) Abstract-The synthesis and characterization by elemental analyses, mass, IR and electronic spectrometry and conductance and magnetic measurements of compounds with the general formulaNi(BBDHP)X2 *nSolv. is reported [x = Cl, Br, I, C104 or NO3 ; Solv. = H20, EtOH or Bu’OH ; n = 2-5 ; BBDHP = 1,7-bis(benzimidazol-2-yl)-2,6_dithiaheptane]. The structures of [Ni(BBDHP)@-C1)]2ClZ - 5H,O * 2EtOH (II) and Ni(BBDHP)Br, * EtOH - 1/2Bu’OH (IV) were determined by single-crystal X-ray diffraction. A molecule of II exhibits a dimeric structure involving two approximately symmetrical chlorine bridges. In both complexes the nickel atom has an octahedral environment with cis coordination of the two halide ligands [av. N&-Cl = 241.6(l), av. Ni-Br = 256.9(9) pm] and the BBDHP in a symmetrical-cis arrangement [av. Ni-S = 243.6(2), av. Ni-N = 207.1(4) pm]. In both compounds the crystal packing is governed mainly by hydrogen bonds involving benzimidazole groups, halide atoms and water molecules. Metal complexesof sulphur-nitrogen chelating ligands have attracted considerableattention because of their interesting physicochemical prop- erties, pronounced biological activities’-3 and as modelsof the metalloprotein and metalloenzyme activesites,sinceit is well known that histidine imidazole nitrogen atoms and methionine thioether sulpliur atoms play key roles in the coordination of metals at the active sites of numerous metallo- *Present address: Departamento de Quimica Puray Aplicada, Universidad de Vigo, Spain. t Author to whom correspondence should be addressed. $ Actual address : Anorganisch-chemisches Institut der Technischen Universitlt Miinchen, Lichtenbergstr. 4, D- 8046 Garching, Germany. biomolecules, 4 whereby linear tetradentate chel- ating ligands with an NSSN-donor system are some of the most utilized.’ As part of our comprehensive research into com- pounds formedby transition and post-transition metal@) ions and polydentate ligands, 6-‘4 this paper describes the synthesis and structural characterization of nickel(I1) complexes of the ligand 1,7-bis(benzimidazole-2-yl)-2,6dithiaheptane (BBDHP), whichalso has an N2S2 donor system via two benzimidazole nitrogen atoms and two thio- ether sulphuratoms.’ ST’6 These complexes, with chlorine and bromine as counter-ions, have already beenpartiallystudied,16 but we have now com- pleted that study and also have determined the crys- tal and molecular structure. 1083