Catalytic H/D exchange of (hetero)arenes with early-late polyhydride heterobimetallic complexes: impact of transition metal pairs

Abstract

Metal-catalyzed hydrogen isotope exchange (HIE) has become a valuable method for incorporating deuterium and tritium into organic molecules, with applications in a wide range of scientific fields. This study explores the role of transition metal cooperativity in enhancing catalytic hydrogen/deuterium (H/D) exchange using early-late heterobimetallic polyhydride (ELHB) complexes. A series of four ELHB complexes, of general formula [M(CH₂tBu)₃(H)_xM'Cp*], combining early transition metals (M = Hf, Ta) with late metals (M' = Ir, Os), were synthesized and evaluated for their catalytic activity in HIE of (hetero)arenes. Hafnium-iridium and hafnium-osmium complexes showed a clear improvement in catalytic efficiency and reaction rate over monometallic analogues, suggestive of metal-metal synergy. Conversely, the tantalum-based heterobimetallic complexes showed lower catalytic performance, revealing that not all metal combinations are equally effective. These results underline the importance of careful metal selection to optimize transition metal cooperativity, and open up new possibilities for the design of more efficient H/D exchange catalysts.