Diruthenium imido dihydride complexes [(Cp*Ru)(2)(mu-NAr)(mu-H)(2)] (Ar = Ph (2a), p-MeOC6H4 (2b), p-ClC6H4 (2c), 2,6-Me2C6H3 (2d); Cp* = eta(5)-C5Me5) have been synthesized by hydrogenation of the corresponding bis(amido) complexes [Cp*Ru(mu-NHAr)](2) (1a-d). Reductive elimination of the N-H bond from 2a-c in the presence of arene yields the amido hydride complexes [(Cp*Ru)(2)(mu-NHAr)(mu-H)(mu-eta(2):eta(2)-arene)] containing a pi-bound arene. The rate and kinetic isotope effect for this reaction are consistent with a mechanism involving initial rate-determining reductive elimination of an N-H bond to produce the c oordinatively unsaturated amido hydride species {(Cp*Ru)(2)(mu-NHAr)(mu-H)} (A) followed by rapid trapping of this species by an arene. The existence of A is also supported by the reversible interconversion of [(Cp*Ru)(2)(mu-NHPh)(mu-H)(mu-eta(2):eta(2)-C7H8)] with the tetranuclear complex [(Cp*Ru)(4)(mu(4)-NHPh)(mu-NHPh)(mu-H)(2)] (4), a dimerization product of A through a mu(4)-NHPh bridge. DFT calculations provide structures of A and transition states for the N-H reductive elimination. Two distinct reaction pathways are found for the N-H reductive elimination, one of which involves direct migration of a mu-hydride to the mu-NAr ligand, and the other involves formation of a transient terminal hydride species.