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.