16-electron elongated dihydrogen complex stabilized by agostic interaction

A 16-electron dicationic dihydrogen complex Ru(eta2-H...H)(PP)2]OTf]2 4; PP = (C6H5CH2)2PCH2CH2P(CH2C6H5)2] has been prepared and characterized by protonating the precursor hydride complex Ru(H)(PP)2)]OTf] (2) using HOTf. The hydride and dihydrogen complexes are stabilized via agostic interaction of the ortho C-H fragment of the phenyl ring on the benzyl group. The intact nature of the H-H bond in this derivative was established from the short spin-lattice relaxation time and the observation of a substantial J(H,D) of 22.0 Hz for the HD isotopomer. The H-H bond distance calculated from J(H,D) is 1.05 A, which falls under the category of elongated dihydrogen ligands.