Air-Stable (CAAC) CuCl and (CAAC)CuBH4 Complexes as Catalysts for the Hydrolytic Dehydrogenation of BH3NH3

The first stable copper borohydride complex [(CAAC)CuBH4] [CAAC = cyclic(alkyl)(amino) carbene] bearing a single monodentate ligand was prepared by addition of NaBH4 or BH3NH3 to the corresponding [(CAAC)CuCl] complex. Both complexes are air-stable and promote the catalytic hydrolytic dehydrogenation of ammonia borane. The amount of hydrogen released reaches 2.8 H-2/BH3NH3 with a turnover frequency of 8400 mol(H2) mol(cat)(-1) h(-1) at 25 degrees C. In a fifteen-cycle experiment, the catalyst was reused without any loss of efficiency.