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(η6-arene)-Ru­(II) complexes have shown the ability to rapidly perform the heterolytic cleavage of H2 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 [(η6-C6H6)-Ru­(2,6-(CH3)2-C6H3NC­(CH3))2CH]­OTf (1) showed excellent activity in the catalytic release of a single equivalent of H2 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 H2 at elevated pressures.