Synthesis, X-ray crystal structures and properties of chromiun complexes with semiquinonate and catecholate

摘要

The reaction of tris-tetrahalogeno-o-benzosemiquinonate chromium(III) complexes, [Cr~(III)(X_4SQ)_3](X = Cl 1a or Br 1b), with bis (cyclopentadienyl) cobalt [Co~(II)Cp_2], tetramethyltetraselenafulvalene (TMTSF) and tetrakis (methylsulfanyl) tetrathiafulvalene (TMT-TTF) afforded four charge-transfer compounds, [Co~(III)Cp_2][Cr~(III)(X_4SQ)_2(X_4Cat)] (X = Cl 2a or Br 2b), [TMT-TTF][Cr~(III)(Br_4SQ)_2(Br_4Cat)] 3b and [TMTSF][Cr~(III)(Br_4SQ)_2(Br_4Cat)] 4b, where Cat is catecholate. The paramagnetic [Cr~(III)(X_4SQ)_2(X_4Cat)]~- complexes are commonly formed by cocrystallization with a diamagnetic [Co~(III)Cp_2]~+ cation for 2a centre dot C_6H_6 and 2b, and paramagnetic TMT-TTF~(centre dot +) and TMTSF~(centre dot +) cations for 3b centre dot C_6H_5CH_3 and 4b centre dot 2CH_2Cl_2, respectively. The one-electron reduced complexes, [Cr~(III)(X_4SQ)_2(X_4Cat)]~-, with two semiquinonate and one catecholate ligands were isolated and crystallographically characterized. The crystal structures of 2a centre dot C_6H_6 and 3b centre dot C_6H_5CH_3 consist of alternating stacks of cations and anionic complexes, which form one-dimensional column structures. On the other hand, the anionic complexes in 4b centre dot 2CH_2Cl_2 form a hexagonal honeycomb network, whose cavities are occupied by the dimerized cation molecules. The temperature dependence of the magnetic susceptibilities reveals that all the [Cr~(III)(X_4SQ)_2(X_4Cat)]~- complexes are in a ground state of S = 1/2, which results from the intramolecular antiferromagnetic interaction between Cr~(III)(d~3) and two semiquinonates. In addition, 3b and 4b have a contribution of the paramagnetic TMT-TTF~(centre dot +) (3b) and TMTSF~(centre dot +) (4b) cations. In all compounds weak intermolecular magnetic interactions were recognized from the decrease of the (X_m)T values at low temperature.