TRANSITION-METAL COMPLEXES OF 2 RELATED PYRAZOLE CONTAINING LIGANDS - 3,6-DIMETHYL-1,8-(3,5-DIMETHYL-1-PYRAZOLYL)-3,6-DIAZAOCTANE (DDAD) AND 1,4-BIS(2-ETHYL-(3,5-DIMETHYL-1-PYRAZOLYL))-PIPERAZINE (BEDP) - SYNTHESIS, SPECTROSCOPY AND X-RAY STRUCTURES

Several coordination compounds with the ligand 3,6-dimethyl-1,8-(3,5-dimethyl-1-pyrazolyl)-3,6-diazaoctane (ddad) were obtained: (Cu, Ni)(ddad)(BF4)2, Co(ddad)(H2O)(BF4)2, (Co, Ni, Cu, Zn)2(ddad)Cl4, Co3(ddad)2(NCS)6 and Cu2(ddad)(NCS)3. Five X-ray structures were obtained, viz. of [Cu(ddad)](BF4)2, [Ni(ddad)](BF4)2, Ni(ddad)(NCS)2, [Ni(bedp)](H2O)(BF4)2 and [Cu(bedp)](H2O)(BF4)2, but the data did not allow the calculation of very accurate bond lengths. However, the basic coordination geometries were obtained in all cases. The coordination by the ligands is square planar, while Ni(ddad)(NCS)2 contains additional trans coordinating thiocyanate anions. The asymmetric unit of [Cu(ddad)](BF4)2 contains two almost identical [Cu(ddad)]2+ species. The coordination of the copper atoms in both molecules is intermediate between tetrahedral and square planar. One molecule [Cu(ddad)]2+ is the (R,R) diastereoisomer of the ligand and the other is the (S,S) diastereoisomer. The chloride compounds are, except for Ni(II), all dinuclear with MN2Cl2 chromophores. The nickel(II) compound contains square planar Ni(ddad)2+ cations and tetrahedral NiCl4(2-) anions. The thiocyanate compound of Ni(II), which is isomorphous with the corresponding Zn(II) compound, has octahedral MN2N2'N2" chromophores. The cobalt compound crystallizes as [Co(ddad)(NCS)]2Co(NCS)4 with five coordinate cobalt in the cation. With copper thiocyanate ddad forms the mixed-valence compound Cu2(ddad)(NCS)3, with [Cu(ddad)]2+ and [Cu(NCS)3]2-. With the ligand, 1,4-bis(2-ethyl-(3,5-dimethyl-1-pyrazolyl))-piperazine (bedp) the compounds [(Ni, Cu)(bedp)](H2O)(BF4)2, (Ni, Co)(bedp)(NCS)2, Zn2(bedp)(NCS)4, (Ni, Co, Cu, Zn)2(bedp)Cl4 and Cu2(bedp)(NCS)3 were obtained. The chloride compounds form dinuclear compounds (similar to ddad) with MN2Cl2 chromophores. However, in addition to the green form of [Ni(bedp)][NiCl4] a purple isomer Ni2(bedp)Cl4, with a tetrahedral NiN2Cl2 chromophore, was obtained. The ligand field spectra of Ni(bedp)(NCS)2 and the isomorphous cobalt compound show typical octahedral chromophores. With copper thiocyanate a mixed-valence compound was formed, with a structure likely to be similar to the corresponding ddad compound, viz. [Cu(II)(bedp)][Cu(I)(SCN)3].