At elevated temperatures (90-130 degrees C), complexes of the type TpRu(PMe3)(2)X (X = OH, OPh, Me, Ph, or NHPh; Tp = hydridotris(pyrazolyl) borate) undergo regioselective hydrogen-deuterium (H/D) exchange with deuterated arenes. For X = OH or NHPh, H/D exchange occurs at hydroxide and anilido ligands, respectively. For X = OH, OPh, Me, Ph, or NHPh, isotopic exchange occurs at the Tp 4-positions with only minimal deuterium incorporation at the Tp 3- or 5-positions or PMe3 ligands. For TpRu(PMe3)(NCMe)Ph, the H/D exchange occurs at 60 degrees C at all three Tp positions and the phenyl ring. TpRu(PMe3)(2)-Cl, TpRu(PMe3)(2)OTf (OTf = trifluoromethanesulfonate), and TpRu(PMe3)(2)SH do not initiate H/D exchange in C6D6 after extended periods of time at elevated temperatures. Mechanistic studies indicate that the likely pathway for the H/D exchange involves ligand dissociation (PMe3 or NCMe), Ru-mediated activation of an aromatic C-D bond, and deuteration of basic nondative ligand (hydroxide or anilido) or Tp positions via net D+ transfer.