Toggle Main Menu Toggle Search

Open Access padlockePrints

Proton Transfer to Nickel-Thiolate Complexes. 1. Protonation of [Ni(SC 6H4R-4)2(Ph2PCH2CH 2PPh2)] (R = Me, MeO, H, Cl, or NO2)

Lookup NU author(s): Dr Valerie Autissier, Emeritus Professor Bill CleggORCiD, Dr Ross Harrington, Professor Richard Henderson


Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


The kinetics of the equilibrium reaction between [Ni(SC6H 4R-4)2(dppe)] (R= MeO, Me, H, Cl, or NO2; dppe = Ph2PCH2CH2PPh2) and mixtures of [lutH]+ and lut (lut = 2,6-dimethylpyridine) in MeCN to form [Ni(SHC6H4R-4)-(SC6H 4R-4)(dppe)]+ have been studied using stopped-flow spectrophotometry. The kinetics for the reactions with R = MeO, Me, H, or Cl are consistent with a single-step equilibrium reaction. Investigation of the temperature dependence of the reactions shows that AG‡ = 13.6 ± 0.3 kcal mol-1 for all the derivatives but the values of ΔH‡ and ΔS‡ vary with R (R = MeO, ΔH‡ = 8.5 kcal mol-1, ΔS‡ = -16 cal K-1 mol -1; R = Me, ΔH‡ = 10.8 kcal mol-1, ΔS‡ = -9.5 cal K-1 mol-1; R = Cl, ΔH‡ = 23.7 kcal mol-1, ΔS‡ = +33 cal K -1 mol-1). With [Ni(SC6H4-NO 2-4)2(dppe)] a more complicated rate law is observed consistent with a mechanism in which initial hydrogen-bonding of [lutH] + to the complex precedes intramolecular proton transfer. It seems likely that all the derivatives operate by this mechanism, but only with R = NO2 (the most electron-withdrawing substituent) does the intramolecular proton transfer step become sufficiently slow to result in the change in kinetics. Studies with [lutD]+ show that the rates of proton transfer to [Ni(SC6H4R-4)2(dppe)] (R = Me or Cl) are associated with negligible kinetic isotope effect. The possible reasons for this are discussed. The rates of proton transfer to [Ni(SC 6H4R-4)2(dppe)] vary with the 4-R-substituent, and the Hammett plot is markedly nonlinear. This unusual behavior is attributable to the electronic influence of R which affects the electron density at the sulfur.

Publication metadata

Author(s): Autissler V, Clegg W, Harrington RW, Henderson RA

Publication type: Article

Publication status: Published

Journal: Inorganic Chemistry

Year: 2004

Volume: 43

Issue: 10

Pages: 3098-3105

ISSN (print): 0020-1669

ISSN (electronic): 1520-510X

Publisher: American Chemical Society


DOI: 10.1021/ic030322e


Altmetrics provided by Altmetric