Reactions of coordinated ligands, Part III(1). Kinetics of lodination of malonate and pyruvate in malonato(pentaammine)-cobalt(III), malonato-bis-(ethylenediamine)cobalt(III) and pyruvato(pentaammine)cobalt(III) ions

Abstract

The kinetics of iodination of malonate and pyruvate in the title complexes are reported at 35.0 °C and I=0.3 M. The reaction is first order in substrate and zeroth order in [I2]. This result is commensurate with rate determining enolisation of the active methylene and methyl groups of the malonate and pyruvate respectively. The reaction is catalysed by H2O, OH− and by the buffer anions used. The rate data suggest that the malonate methylene group in the [Co(en)2-O2CCH2CO2]2+ chelate is considerably more active towards electrophilic substitution than is the case in [Co(NH3)5O2CCH2CO2]2+.