Large Solvent Isotope Effect Associated with the Hydrolysis of Allylindium Iodide

Allylindium halides are valuable allylating reagents, which can even be applied in aqueous solutions. Previous 1H NMR spectroscopic investigations suggested that these reagents are stable for several hours in D2O, whereas ESI-mass spectrometric experiments in H2O pointed to much shorter lifetimes. To resolve this seeming discrepancy, the present study systematically examines the solvolysis of allylindium iodide in H2O, D2O, and mixtures thereof by both analytical methods. Kinetic measurements find a large kinetic isotope effect (KIE = 12.0 ± 1.5 at 298 K), which fully explains the different behavior in H2O and D2O. Moreover, new intact and partially hydrolyzed allylindium intermediates are detected. Additional experiments on solutions of allylindium iodide in CH3OH, CH3OD, and EtOH observe ions identical or similar to those present in aqueous solutions, but determine a somewhat smaller kinetic isotope effect.