The reaction of the ruthenium polyhydrides RuH2(PPh3)(4) and RuH2(H-2)(2)(PCy3)(2) with the previously reported dendrimers Gx-N(CH2PPh2)(2) (first, second, and third generations; G(1), G(2), and G(3)) cleanly leads to the new complexes [G(x)-N(CH2PPh2)(2)] RuH2(PPh3)(2) (1-G(x)) and [G(x)-N(CH2PPh2)(2)]RuH2(H-2)(PCy3), which exist as a mixture of isomers (3'-G(x), 3 ''-G(x) 4'-G(x), and 4 ''-G(x)). Complexes 3-G(x)/4-G(x) were shown to accommodate a stretched dihydrogen ligand and to display a high temperature for the minimum of the T-1 relaxation time, in agreement with their binding to the dendrimer in solution. The reactivity of these complexes with CO, leading to new dihydrido carbonyl ruthenium complexes (2-G(x), 5-G(x)), is described.