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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|
|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.|
|Appears in Collections:||IJC-A Vol.30A(07) [July 1991]|
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