Proton magnetic resonance studies of the active methylene group in some cobalt(III) malonato-cations

Abstract

The protons of the methylene group of co-ordinated malonate in the complexes [Co(en)₂(mal)]⁺ and [Co(bipy)₂(mal)]⁺ have been shown to exchange with deuterium in D₂SO₄–D₂O solutions. The rates are of the first order in D₃O⁺ concentration. For the ethylenediamine complex ΔH^‡ is 27·4 kcal mol^–1 and ΔS^‡ is +27 cal mol^–1 K^–1 and for the bipyridyl complex ΔH^‡= 18·4 kcal mol^–1 and ΔS^‡ is –1·0 cal mol^–1 K^–1.