Using an exchange reaction involving one PCy3 ligand in HRu(CO)Cl(PCy3)2 (1) for one IMes, a ruthenium−hydride complex HRu(CO)Cl(PCy3)(IMes) (2) has been prepared. Complex 2 is an active catalyst in the hydrogenation of alkenes. A TON of 24000 h-1 has been obtained at 100 °C under 4 atm of hydrogen. Addition of HBF4·OEt2 as cocatalyst enhanced the catalytic activity.
