Some New Dicationic Dihydrogen Complexes of Ruthenium

Abstract

A series of new dicationic dihydrogen complexes of ruthenium of the type trans-[(dppe)2Ru(η2-H2)(RCN)][BF4]2 [dppe = Ph2PCH2CH2PPh2; R = CH3, CH3CH2, CH3CH2CH2, CH2=CH, p-CH3−C6H4−CH2, C6H5, and (CH3)2N] have been prepared by the protonation reaction of the precursor hydrides, trans-[(dppe)2Ru(H)(RCN)][BF4] using HBF4·OEt2. The variable temperature spin-lattice relaxation times (T1, ms) and the H, D coupling constants of the η2-HD isotopomers indicate the intact nature of the H−H bond in these complexes. It was found that the spectroscopic and chemical properties of these derivatives are not very sensitive to the change in the trans nitrile ligand. The pKa values of the dihydrogen complexes have been determined using the equilibrium: trans-[(dppe)2Ru(H)(RCN)][BF4] + HBF4·OEt2 ⇄ trans-[(dppe)2Ru(η2-H2)(RCN)][BF4]2 + Et2O by 1H NMR spectroscopy.