| Popis: |
The preparation, some magnetic, spectral and electrochemical properties of the compounds [Cu3(Bu2dtc)6] [MBr3]2(M = Zn, Cd, Hg) are reported. The crystal structure of the compound [Cu3(Bu2dtc)6] [CdBr3]2 has been determined by a three-dimensional X-ray analysis. The triclinic cell, space group with a = 12.629(4), b = 13.706(4), c = 12.506(4) A and α = 95.84(4). β = 91.45(4), γ = 86.06(3)°, contains one formula unit. Atomic parameters were refined to a conventional R value of 0.05 for 1344 independent non-zero reflections. The structure consists of two centrosymmetric ionic units [Cu3(Bu2dtc)6]2+ and [Cd2Br6]2−. In the cation one copper atom has an apically distorted octahedral S-coordination, with CuS distances of 2.30(1), 2.35(1) and 3.19(1) A. The two other equivalent copper atoms have five-fold pyramidal S-coordinations with CuS distances of 2.21(1), 2.22(1), 2.23(1), 2.23(1) and 2.88(1) A. The Cd2Br ion can be described as a slightly-distorted edge-condensed bitetrahedron. Esr single-crystal spectra prove localisation of the unpaired electron at one copper atom. The I.R. spectra show double CuS and CN stretching frequencies. All these data suggest the compounds to be composed of copper in different states of oxidation. The cation can be described as [(Cu(III)(Bu2dtc)2)2Cu(II)(Bu2dtc)2]2+. The ionic structure is confirmed by conductivity measurements. |
