62637-81-4Relevant academic research and scientific papers
Synthetic analogs for evaluating the influence of N-H...S hydrogen bonds on the formation of thioester in acetyl coenzyme a synthase
Ariyananda, Piyal W. G.,Kieber-Emmons, Matthew T.,Yap, Glenn P. A.,Riordan, Charles G.
, p. 4359 - 4369 (2009/10/16)
A series of square planar methylnickel(II) complexes, (dppe)Ni(Me)(SAr) (dppe = 1,2-bis(diphenylphosphino)ethane); 2. Ar = phenyl; 3. Ar = pentafluorophenyl; 4. Ar = o-pivaloylaminophenyl; 5. Ar = p-pivaloylaminophenyl; (depe)Ni(Me)(SAr), (depe = 1,2-bis(diethylphosphino)ethane); 7. Ar = phenyl; 8. Ar = pentafluorophenyl; 9. Ar = o-pivaloylaminophenyl; 10. Ar = p-pivaloylaminophenyl), were synthesized via the reaction of (dppe)NiMe 2 (1) and (depe)NiMe2 (6) with either the corresponding thiol or disulfide. These complexes were characterized by various spectroscopic methods including 31P NMR, 1H NMR, 13C NMR and infrared spectroscopies and in most cases by X-ray diffraction analyses. Solid state and solution measurements establish that 4 and 9 contain intramolecular N-H...S bonds. Carbonylation of the complexes 2-4, 7-10 leads to (dRpe)Ni(CO)2 and MeC(O)SAr via the intermediacy of the acylnickel adducts, (dRpe)Ni(C(O)Me)(SAr), detected at low temperature by 31P NMR spectroscopy. Consistent with experimental observations, density functional theory results reveal that the intramolecular hydrogen bond in 9 stabilizes the acylnickel adduct compared with its non-hydrogen-bonded adduct, 10. Oxidative addition of MeC(O)SC6F5 to (dRpe)Ni(COD) followed by spontaneous decarbonylation proceeds in variable yields generating 3 and 8.
Proton Transfer to Nickel-Thiolate Complexes. 1. Protonation of [Ni(SC 6H4R-4)2(Ph2PCH2CH 2PPh2)] (R = Me, MeO, H, Cl, or NO2)
Autissler, Valerie,Clegg, William,Harrington, Ross W.,Henderson, Richard A.
, p. 3098 - 3105 (2008/10/09)
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.
