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Publication Type
Journal Article
UWI Author(s)
Author, Analytic
Dasgupta, Tara, P.; Holder, A.A.
Author Affiliation, Ana.
Chemistry; Faculty of Pure and Applied Sciences
Article Title
Synthesis, acid hydrolysis and formation of the [(H3N)5CoOMoO3]+ ion in aqueous solution
Medium Designator
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Connective Phrase
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Journal Title
Journal of the Chemical Society. Dalton Transactions
Translated Title
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Reprint Status
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Date of Publication
1996
Volume ID
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Issue ID
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Page(s)
2637-2643
Language
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Location/URL
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ISSN
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Notes
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Abstract
The complex [(H3N)5CoOMoO3]ClO4 has ben synthesised and charcterised by elemental analysis, UV/VIS and infrared spectroscopy. The kinetics of its acid hydrolysis has been studied using the stopped-flow technique over the ranges 0.01 [H+] 0.45 mol dm-3, 24.9 35.6 C, 0.04 I I.0 mol dm-3 (NaClO4). The rate of reaction is inversely dependent on [H+] due to the expansion of the co-ordination of the molybdenum (vi) from four to six on protonation, along with resonance stabilisation. The rate constant (k1) for the hydrolysis is 5.09 0.02 s-1 at 24.9 C for which DH = 82 1 kJ mol -1 and DS = 43 5 J K-1 mol-1. The kinetic of formation of the complex from pentaammineaquacobalt (III) and molybdate (vi) ions has been studied using the stopped-flow method over the range pH 7.13-8.46 and at 25.0-35.9 C, I = 1.0 mol-1dm-3. Over this pH range both [Co(NH3)5(OH2)]3+ and [Co(NH3)5(OH)]2+ ion react with HMoO4 - to give [(H3N)5CoOMoO3]+, and the rate constants are (2.03 0.05) x 106 and (2.73 0.05) x 105 dm3 mol-1 s-1, respectively at 25.0 C. Both acid hydrolysis and complexation are very rapid, suggesting a mechanism involving cleavage of the MoVI-O not the CoIII-O bond. Details of both mechanisms are discussed....
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