16-electron elongated dihydrogen complex stabilized by agostic interaction

A 16-electron dicationic dihydrogen complex $[Ru(\eta^2-H^{...}H)(PP)_2]-[OTf]_2\hspace{2mm}[4; PP )= (C_6H_5CH_2)_2PCH_2CH_2P(CH_2C_6H_5)_2]$ 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 \AA, which falls under the category of elongated dihydrogen ligands.