128 - J . C H E M . S OC., C H E M . C O M M U N . , 1563...

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J. CHEM. SOC., CHEM. COMMUN., 193 1563 (NEt4)3[V602S4(edt)6]: A Model for the Adsorption of Naked [VO]2+ Units on Vanadium Sulfide Surfaces Keith A. York, Kirsten Folting and George Christou" Department of Chemistry and the Molecular Structure Center, Indiana University] Bloomington, IN 47405, USA (NEt4)3[V602S4(edt)6].EtCN 2 (edtH, = ethane-l,2-dithiol) has been obtained in small yield (5-10%) from (NEt4)Na[VS(edt)2]; complex 2 has a structure comprising two VO2+ units bound to a [V4S4] core and thus represents a model for the adsorption of [VO]2+ species on the surface of V sulfides during crude oil hydrotreating processes. Our continuing interest in non-organometallic V sulfide chemistry derives from the desire to elucidate possible intermediates forming during the conversion of crude oil vanadyl porphyrin impurities into insoluble V sulfides during industrial hydrodesulfurization (HDS) and hydrodemetalla- tion (HDM) processing of heavy crudes.1 The formation of V sulfides (primarily V2S3 and V3S4) has deleterious conse- quences on the activity of the supported Mo HDS catalyst, although they are themselves good HDM catalysts, catalyzing the further conversion of vanadyl species into V sulfides.2 The mechanism of this transformation is believed to involve initial Lewis acid-Lewis base interactions between the VO(por) (por = porphyrin) molecules and the V sulfide surface, followed by demetallation and subsequent reduction of the porphyrin ring to a chlorin.3--5 The liberated [VO]2+ entity becomes bound to surface S groups, as determined by EPR and EXAFS studies on used catalysts that indicate [VO]2+ groups in a VOS4 first-coordination sphere .2.697 This is summarized in Scheme 1. The surface-bound [VO]2+ groups subsequently get sulfided and reduced to form another layer of the growing V sulfide crystalline phase. Thus, the crude oil V impurities catalyze their own removal (autocatalytic HDM activity).2 We have for a long time sought a molecular system to model the surface-bound [VO]2+ units viz. a complex containing [VO]2+ groups bound to a [VxSy] aggregate. Such a complex has, to-date, been unknown, but we herein report the attainment of such a species from the hydrolysis of the thiovanadyl complex (NEt4)Na[VS(edt),] (1; edtH2 = ethane- 1,2-dithiol) -8 Addition of 1 equiv. of HNEt3C1 to a solution of complex 1 in EtCN led to a darkening of the solution colour from orange-brown to deep brown-black. The solution was main- tained at room temp. overnight, NaCl removed by filtration,
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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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128 - J . C H E M . S OC., C H E M . C O M M U N . , 1563...

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