American Chemical Society
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Linear Trichromium Complexes with Direct Cr to Cr Contacts. 2. Compounds with Cr3(dipyridylamide)43+ Cores

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posted on 2000-01-25, 00:00 authored by Rodolphe Clérac, F. Albert Cotton, Lee M. Daniels, Kim R. Dunbar, Carlos A. Murillo, Isabel Pascual
Seven compounds having in common a Cr3(dpa)43+ core (dpa = di(2-pyridyl)amide ion) have been prepared and all shown to have an unsymmetrical chain of three Cr atoms. This chain can be described as a pair of quadruply bonded CrII atoms to which a CrIII atom is attached. No symmetrical chain has been found, contrary to a previous preliminary report. The seven compounds have been well characterized crystallographically, and their short and long Cr to Cr distances (Å, in parentheses) are:  1 [Cr3(dpa)4Cl2]Cl·2CH2Cl2·THF (2.12, 2.47), 2 [Cr3(dpa)4Cl2]AlCl4·CH2Cl2 (2.011, 2.555), 3 [Cr3(dpa)4Cl2]FeCl4·CH2Cl2 (2.009, 2.562), 4 [Cr3(dpa)4Cl2]I3·THF·2H2O (2.08, 2.49), 5 [Cr3(dpa)4Cl2]PF6·2CH2Cl2 (2.08, 2.48), 6 [Cr3(dpa)4(BF4)F]BF4·2CH2Cl2 (1.900, 2.595), 7 [Cr3(dpa)4ClF]BF4·CH2Cl2·C6H14 (2.039, 2.507). Magnetic susceptibility measurements on 1 and 2 reveal μeff = 3.85 ± 0.05 μB from 10 to 300 K.