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Title: Reactivity of coordinated anlido base in base hydrolysis of cis-(bromo)(2-aminothiazole)-bis-(ethylenediamine)cobalt(III) cation
Authors: Dash, Anadi C
Pradhan, Jyotsnamayee
Issue Date: Jul-1991
Publisher: NISCAIR-CSIR, India
Abstract: Evidence is presented in support of cobalt(Ill) promoted NH-deprotonation of coordinated 2-aminothiazole in cis-[Co(en)2(2-aminothiazole)Br]2+ which undergoes base hydrolysis via SN1 (CB) mechanism. The pKNH of coordinated 2-aminothiazole is 12.8 ± 0.1 at 25°C and I =0.1 mol dm-3. The amido conjugate base undergoes H2O or Br- substitution at cobaIt (ID) centre 107 times faster than its conjugate acid analogue. This dramatic rate enhancement is predominantly due to considerably low activation enthalpy (∆H =46 ± 5 kJ mol-1) for the substitution reaction of amido base. The negative value of the activation entropy (∆S = - 39 ± 20 J K-1 mol-1) is consistent with the fact that the solvation sphere of the transition state is relatively more ordered than that of the initial state.
Page(s): 601-603
ISSN: 0975-0975(Online); 0376-4710(Print)
Appears in Collections:IJC-A Vol.30A(07) [July 1991]

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