Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Novel metal complexes (R4N)[Ni(ddds)2] (R = Me, Et and nBu, ddds = 5,6-dihydro-1,4-dithiin-2,3-diselenolate) have been prepared and their crystal structures determined. The intraligand Se-Se distance is longer than that between the inner sulfur atoms of the five-member ring of the M(dddt)2- sulfur analogue and is almost equal to the S-S distance in the six-member ring. Consequently, two-dimensional intermolecular close contacts are expected, and observed in Ni(ddds)2 complexes. The neutral Ni(ddds)2 species was obtained by electrochemical oxidation from the monoanionic (nBu4N)[Ni(ddds)2] complex. X-Ray crystal structure analyses of this neutral species show that two Ni(ddds)2 are connected by the two Ni-Se bonds. Thus, the Ni(ddds)2entities form [Ni(ddds)2]2dimers which are arranged face-to-face and rotated by about 90° with respect to each other. The electrochemical behavior of (nBu4N)[Ni(ddds)2] indicates the possible formation of cation-radical species. The room temperature magnetic susceptibility measurements showed that the (R4N)[Ni(ddds)2] complexes are paramagnetic with μeff = 1.77-1.83 μB, corresponding to one unpaired electron per molecular formula. The temperature dependence of the magnetic susceptibility of (Et4N)[Ni(ddds)2] is indicative of weak long-range antiferromagnetic ordering below 9 K. The dimerization in [Ni(ddds)2]2results in a strong antiferromagnetic spin coupling within the dimer, and explain the non magnetic state observed for this compound.
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