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Kinetics of the reactions between [S2MoS2CuSC 6H4R-4]2- (R = MeO, H, Cl or NO2) and CN-: Substitution mechanism at a 3-coordinate Cui site

Lookup NU author(s): Professor Richard Henderson



The kinetics of the reaction between [S2MoS 2Cu(SC6H4R-4)]2- (R = MeO, H, Cl or NO2) and CN- to form [S2MoS2CuCN] 2- have been studied in MeCN using stopped-flow spectrophotometry. In all cases, the rate law is of the form, Rate = {k1R + k2R[CN-]}[S2MoS 2Cu(SC6H4R-4)2-]. It is proposed that both k1R and k2Rcorrespond to associative substitution mechanisms. The k2R pathway involves attack by CN- at the copper site followed by dissociation of the thiolate. The k1R pathway involves attack of the solvent (MeCN) at the copper site, followed by dissociation of the thiolate to form [S 2MoS2Cu(NCMe)]-. Subsequent rapid substitution of the coordinated solvent by cyanide produces [S2MoS 2CuCN]2-. The evidence that both the k1R and k1R pathways involve associative mechanisms are: (i) the 4-R-substituent on the thiolate ligand has a similar effect on both k1R and k2R, with electron-withdrawing 4-R-substituents facilitating substitution; (ii) both the k1R and k2R pathways are associated with similar activation parameters (for for k1H: ΔH‡ = 5.5 ±0.5 kcal mol-11, ΔS‡ = -23.9 ± 2.0 cal deg-1 mol-1; for k2H: ΔH‡ = 2.3 ±0.5 kcal mol-1, ΔS‡ = - 23.9 ± 2.0 cal deg-1 mol-1) and (iii) addition of C6H5S- results in a similar increase in both k1R and k 2R. © The Royal Society of Chemistry 2005.

Publication metadata

Author(s): Lin P, Smyth L, Waldram A, Henderson RA

Publication type: Article

Publication status: Published

Journal: Dalton Transactions

Year: 2005

Issue: 19

Pages: 3173-3178

Date deposited: 09/07/2010

ISSN (print): 1477-9226

ISSN (electronic): 1477-9234

Publisher: Royal Society of Chemistry


DOI: 10.1039/b508389c


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