Application of β-Diketiminato Arene-Substituted Ru(II) Complexes in Highly Efficient H₂ Dehydrocoupling of Amine Boranes

Amine borane type substrates show significant potential as safe and effective chemical hydrogen storage materials. β-Diketiminato(η 6 -arene)-Ru(II) complexes have shown the ability to rapidly perform the heterolytic cleavage of H 2 under mild conditions through bifunctional metal-ligand interaction. The presented work explores the applicability of such complexes toward the catalytic dehydrogenation of different substituted amine boranes, in particular, ammonia borane (AB) and N, N -dimethylamine borane (DMAB). Complex [(η 6 -C 6 H 6 )-Ru(2,6-(CH 3 ) 2 -C 6 H 3 NC(CH 3 )) 2 CH]OTf ( 1 ) showed excellent activity in the catalytic release of a single equivalent of H 2 within 0.5 h from a concentrated DMAB solution in THF (3.2 M) at near ambient temperatures. Studies involving structural analogues of 1 allowed insight into the operational dehydrocoupling mechanism. It is concluded from this preliminary work that in solution, 1 forms a homogeneous bifunctional active species that does not undergo deactivation, even after prolonged exposure to H 2 at elevated pressures.