The Ru2 and RuNi derivatives of 1,8-bis(10,15,20-trimesityl-5-porphyrinato)anthracenea recently reported cofacial diporphyrin ligand comprising two hindered porphyrins spanned by an anthracene bridgehave been synthesized. Both Ru2(DPAHM) and RuNi(DPAHM) are extremely reactive species that apparently contain 14-electron Ru(II) centers and, as is the case for their monoporphyrin analog, ... [Show full abstract] (5,10,15,20-tetramesitylporphyrinato)ruthenium [Ru(TMP)], must be rigorously protected from oxygen, nitrogen, and other ligating agents. In addition, these electron-deficient Ru(II) porphyrins all appear to bind aromatic solvents such as benzene and toluene, the weakest ligating solvents in which these Ru(II) porphyrins have been found soluble. Ru(TMP) and its metallodiporphyrin analogs, Ru2(DPAHM) and RuNi(DPAHM), catalyze H2/D2 exchange in benzene solution and as solids. When adsorbed on a particularly nonpolar carbon support, these Ru(II) porphyrins all manifest significant activity with respect to catalytic H2/D2 exchange [approximately 40 turnovers s-1, when normalized for Ru(II) content]. In addition, these molecules slowly catalyze the exchange of H2 into deuterated aromatic hydrocarbons and, in the absence of solvent, the exchange of D2 into CH4. Kinetic studies of H2/D2 exchange catalyzed by these Ru(II) porphyrins on carbon supports indicate that exchange is likely to be effected by one face of a single Ru(TMP) moiety. The activity of each supported catalyst was suppressed by the presence of ligands, either exogenous (CO irreversibly and N2 reversibly) or from polar functionalities on the surface of the supporting matrix.