Ligand effects upon deuterium exchange in arenes mediated by [Ir(PR3)2(cod)]+.BF-4

A series of complexes of general form [Ir(PR 3 ) 2 (cod)] + has been prepared and used, without isolation, to mediate deuteration of a range of model substrates. The data suggest that, with many substrates, basicity of the phosphine ligands bound to iridium is an important factor influencing substrate selectivity and the efficiency of deuteration. In addition, the spectrum of activity of iridium complexes bearing pure donor ligands is different in many cases to that of complexes where the ligands are known to be π‐acids. Copyright © 2003 John Wiley & Sons, Ltd.