Thiocyanato adducts of chromium(II) carboxylates and the molecular structure of tetraethyl-ammonium tetra-μ-propionatodiisothio-cyanatodichromate(II) |
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| Authors: | Peter D Ford Leslie F Larkworthy David C Povey Andrew J Roberts |
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| Institution: | Department of Chemistry, University of Surrey, Guildford GU2 5XH, England |
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| Abstract: | X-Ray crystallographic studies on NEt4]2Cr2(O2CC2H5)4(NCS)2] show that the Cr–Cr separation (2.467Å) in the dinuclear anion is one of the longest known. The thiocyanato groups are N-bonded, and the results emphasize the known sensitivity of the quadruple Cr–Cr bond to the nature of the axial ligands. The compound crystallises in the tetragonal space group P4/mnc with two molecules per unit cell, the dimensions of which are a = b = 9.785(1), c = 21.186(2) Å. Magnetic investigations from room to liquid nitrogen temperature on the tetra-μ-propionato complex and on NMe4]2 Cr2(O2CCH3)4(NCS)2] show that both complexes have been obtained free from paramagnetic chromium(III) impurities. Their weak paramagnetic susceptibilities (Xcr is approx. 200 x 10?6 cm3 mol?1 at 295 K and 50 x 10?6cm3mol?1 at 90 K) are inherent, and are ascribed to temperature independent paramagnetism at low temperature plus para-magnetism arising from slight population of the triplet state (2J  700 cm?1, g = 2, N = 50 x 10?6cm3mol?1) at higher temperatures. |
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| Keywords: | Author to whom correspondence should be addressed |
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