A pyridine solution of [Pt(AuPPh3)8](NO3)2 showed surprisingly fast isotope exchange catalysis between D2(gas) and H2O(liquid). Thus, H-2 and HD were produced with a turnover rate of ca. 1.5 min-1 from a pyridine solution of cluster (1 x 10(-3) mmol), D2 (1.3 mmol), and H2O (0.6 mmol) at 1 atm and 30-degrees-C. There have been only a few reports of this catalysis reaction with metal complexes, and the cluster gave a rate at least 2 orders of magnitude faster. P-31 NMR of a pyridine solution of [Pt(AuP-Ph3)8]2+ = M2+ under 0.1 atm of H-2 showed an equilibrium mixture of M2+, M(H)2(2+), and a M(H)+ suggesting that the mechanism for exchange involved reversible deprotonation of M(H)2(2+) to give M(H)+ and PyH+. The dihydrido cluster M(H)2(2+) is known to be in rapid equilibrium with M2+ and H-2.