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Cobalt(II) and cobalt(III) complexes with 4'-(4-cyanophenyl)-2,2':6',2''-terpyridine
Zhong Yu1, Atsuhiro Nabei, Takafumi Izumi
1Department of Chemistry, Faculty of Science and Engineering, Kinki University, Higashi-Osaka, Osaka 577-8502, Japan.
Abstract:
4'-Cyanophenyl-2,2':6',2''-terpyridine (cptpy) was employed as an N,N',N''-tridentate ligand to synthesize the compounds bis[4'-(4-cyanophenyl)-2,2':6',2''-terpyridine]cobalt(II) bis(tetrafluoridoborate) nitromethane solvate, [Co(II)(C(22)H(14)N(4))(2)](BF(4))(2) x CH(3)NO(2), (I), and bis[4'-(4-cyanophenyl)-2,2':6',2''-terpyridine]cobalt(III) tris(tetrafluoridoborate) nitromethane sesquisolvate, [Co(III)(C(22)H(14)N(4))(2)](BF(4))(3) x 1.5 CH(3)NO(2), (II). In both complexes, the cobalt ions occupy a distorted octahedral geometry with two cptpy ligands in a meridional configuration. A greater distortion from octahedral geometry is observed in (I), which indicates a different steric consequence of the constrained ligand bite on the Co(II) and Co(III) ions. The crystal structure of (I) features an interlocked sheet motif, which differs from the one-dimensional chain packing style present in (II). The lower dimensionality in (II) can be explained by the disturbance caused by the larger number of anions and solvent molecules involved in the crystal structure of (II). All atoms in (I) are on general positions, and the F atoms of one BF(4)(-) anion are disordered. In (II), one B atom is on an inversion center, necessitating disorder of the four attached F atoms, another B atom is on a twofold axis with ordered F atoms, and the C and N atoms of one nitromethane solvent molecule are on a twofold axis, causing disorder of the methyl H atoms. This relatively uncommon study of analogous Co(II) and Co(III) complexes provides a better understanding of the effects of different oxidation states on coordination geometry and crystal packing.
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