137 - J . C HEM. SOC. DALTON TRANS. 1 813 1994 Preparation,...

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J. CHEM. SOC. DALTON TRANS. 1994 1813 Preparation, Crystal Structure and Magnetochemistry of [NEt,] [V,Cl,(thf ),]CH,CI, (thf = tetrahydrofuran) t Joe R. Rambo, Stuart L. Bartley, William E. Streib and George Christou" Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405-4001, USA The reaction between [VCl,(thf ),I and [NEt,],[VOCI,] resulted in CI- transfer from the [VO]'+ reagent and the formation of anionic V"' products. In MeCN solution, the product was the known [NEt,] [VCI,(MeCN),], whereas in CH,CI, solution the new complex [NEt,] [V,Cl,(thf),]~CH,CI, 4 was obtained. The structure of the anion of 4 consists of a face-sharing bioctahedron with three p-CI- ions. The V V distance of 3.1 76(2) A precludes metal-metal bonding. Variable-temperature magnetic susceptibility (xm) studies on solid samples of 4 in the temperature range 5.0-300 K have been performed. The data were satisfactorily fitted to the theoretical xrnys. T expression for a d24 dinuclear complex. The fitting parameters obtained were J = -48(1) cm-l (H = -WS,-S,), g = 1.90 and a 4.1 % paramagnetic impurity. The V"' ions are thus antiferromagnetically coupled. We are engaged in a research programme directed towards the development of certain aspects of the chemistry of vanadium with oxygen and/or sulfur ligation. This work is stimulated by the relevance of this area to vanadium involvement in crude oil hydrotreating processes; crude oil vanadyl impurities are reduced and transformed to sulfides under processing con- ditions, ultimately to insoluble vanadium sulfides (primarily V2S3 and V,S,), which deposit on and poison the supported molybdenum hydrodesulfurization catalyst. We have been preparing a number of vanadium species of various nuclearities and oxidation In many cases, these complexes have been paramagnetic and have involved magnetic exchange interactions between the constituent V"' and/or V" ions. As a result, we have sought to characterize these interactions via magnetochemical methods. It is particularly relevant to this work to note that, in contrast to, e.g., Cu" systems, relatively few dinuclear V"' (or V") systems have been magnetochemically characterized; a contributing factor to this is undoubtedly the usual air- and moisture-sensitivity of V"' systems, and the tendency of [V0l2 + complexes to be mononuclear. In this paper, we describe a product obtained from the reaction between [VCl,(thf),] (thf = tetrahydrofuran) and [VOC1,]2 - . We have shown earlier that this reaction in a 3 : 1 ratio in MeCN, and in the presence of Na,(edt) (H,edt = ethane-l,2-dithiol) and a reducing agent leads to the formation of the V"' complex [V,0(edt)2C18]z-. To assist in under- standing this transformation (and others currently being investigated), it was important to determine the product of the reaction between [VCl,(thf),] and ~OC1,I2- alone. For example, 0x0-bridged V"'V'v mixed-valence species were considered to be one type of possible product. In fact we have now established that the reaction between pCl,(thf),] [VOC1,I2- leads to C1- ion transfer and the formation of the V"' species [VCl,(MeCN),]- or LT,Cl,(thf),]- in MeCN or CH2C12, respectively. We herein describe these results in detail,
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This note was uploaded on 01/20/2012 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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137 - J . C HEM. SOC. DALTON TRANS. 1 813 1994 Preparation,...

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