Direct evidence for a rate–determining chelate ring closure mechanism during the reaction of 2,2′-bipyridine with the hexakis(dimethyl sulphoxide)-aluminium(III) ion in nitromethane solution
Abstract
Stopped-flow Fourier-transform n.m.r. experiments reveal two distinct stages in the reaction between the [Al(Me2SO)6]3+ ion and 2,2′-bipyridine in [2H3]-nitromethane solution, substitution of the first solvent molecule (at 298·2 K, 10–3k1= 2·0 dm3 mol–1 s–1, ΔH‡= 75·9 ± 4·3 kJ mol–1, ΔS‡=+ 73 ± 16 J K–1 mol–1) being much faster than the rate of displacement of the second solvent molecule (at 298·2 K, 102k2= 3·9 s–1, ΔH‡= 92·0 ± 1·7 kJ mol–1ΔS‡= 36·6 ± 6·3 J K–1 mol–1).