Synthesis and Characterization of New Dicationic Dihydrogen Complexes of Ruthenium

Abstract

A series of new dicationic dihydrogen complexes of the type trans‐[Ru(η2‐H2)(L)(dppm)2][X]2 (L=CH3CN, CH2˭CHCN, C6H5CN, C6H5NC, CO; X=BF4, OTf; dppm=Ph2PCH2PPh2) have been prepared by protonating the precursor hydrides using either HBF4 · Et2O or HOTf. The variable temperature spin‐lattice relaxation times (T 1, ms) and the H, D coupling constants of the η2‐HD isotopomers indicate the intact nature of the H‐H bond in these derivatives. The H‐H distances of the dihydrogen complexes bearing trans‐nitrile ligands are not significantly affected by the sterics and the electronics of the nitrile. On the other hand, the H‐H distances of the dihydrogen complexes bearing either isonitrile or CO ligand are comparable to those possessing chelating diphosphine ligands of greater bite angle. Also, the thermal stabilities of these complexes are significantly less than those bearing diphosphines of greater bite angle. The trans‐[Ru(H)(CH3CN)(dppm)2][BF4] complex has been characterized by X‐ray crystallography.