Highly Stereoselective Proton/Hydride Exchange: Assistance of Hydrogen Bonding for the Heterolytic Splitting of H2

The dihydrido amine complex [Ru(H)2PMe3{HN(CH2CH2P i Pr2)2}] and H2O exhibit highly unusual, stereoselective H+/H− exchange, as derived using 1H 2D EXSY NMR spectroscopy. While H RuA rapidly exchanges with H2O [k = 337(20) L mol−1 s−1], no direct H RuB /H2O proton exchange was detected. Methylation of the pincer amine nitrogen results in unselective slow exchange of both hydrides with H2O. These results emphasize the important role of hydrogen bonding of N with Brønsted acids (e.g., water) for heteroloytic H2 activation with Ru−amide hydrogenation catalysts, which was confirmed computationally.