82374-13-8Relevant articles and documents
Synthesis, structure, spectroscopy, and magnetism of transition-metal compounds with bridging hexafluorosilicate groups. Crystal and molecular structure of catena-(μ-hexafluorosilicato)tetrakis(N-vinylimidazole)cobalt(II)
Driessen, René A. J.,Hulsbergen, Frans B.,Vermin, Willem J.,Reedijk, Jan
, p. 3594 - 3597 (2008/10/08)
A new class of linear-chain compounds containing the SiF62- ion as a bridging ligand is described. The compounds have the general formula M(viz)4SiF6, with M = Mn, Fe, Co, Ni, Cu, and Zn and with viz = N-vinylimidazole. The compounds are prepared by addition of viz to alcoholic solutions containing metal(II) hexafluorosilicate in the ratio 4:1. Spectroscopic properties of the compounds agree with the chromophore MN4F2, most likely having a trans geometry. Detailed study of the magnetic susceptibility in the region 4-90 K shows the metal ions to be weakly antiferromagnetically coupled. Such a coupling is not observed for the Ni(II) compound, where the presence of a positive zero-field splitting of the ground-state triplet prevents the observation of any magnetic coupling. The X-ray structure of Co(viz)4SiF6 shows that Co(II) has a tetragonal coordination geometry, consisting of four equatorially coordinated N-vinylimidazole ligands and two F atoms belonging to different SiF62- anions. The SiF6 groups connect the Co(viz)42+ ions by forming strictly linear chains with a sequence -F-Co-F-Si-. The compound crystallizes in the tetragonal space group P42/n, with a = 12.594 (3) ? and c = 7.683 (2) ? and two formula units per unit cell. The structure was solved by standard heavy-atom techniques and refined by least-squares techniques. The residual R factor was 0.033 for 533 independent reflections considered as observed (I > 2σ(I)). Intensities were measured on an automatic four-circle diffractometer with use of Mo Kα radiation. Bond distances are Co-N = 2.097 (2), Co-F = 2.143 (2), Si-Feq = 1.667 (1), and Si-Fax = 1.699 (2) ?. All bond angles for Co and Si are close to 90 and 180°.
