The complexes [(C5R5)RuH(dippae)] [R = H (1a), Me (2a); dippae = 1,2-bis(diisopropylphosphinoamino)ethane] and [(C5R5)RuH((R,R)-dippach)] [R = H (1b), Me (2b); (R,R)-dippach = (R,R)-1,2-bis(diisopropylphosphinoamino)cyclohexane] have been prepared and characterized. The cationic ruthenium(IV) dihydride derivatives [(C5R5)RuH2(dippae)][BPh4] [R = H (3a), Me (4a)] and [(C5R5)RuH2((R,R)-dippach)][BPh4] [R = H (3b), Me (4b)] are also reported. No significant intramolecular interaction between the amino protons and the hydrogen atoms bound to the metal has been observed in any of these compounds. The X-ray crystal structure of 4a was determined. The proton-transfer processes over the monohydrides 2a and 2b with HBF4 center dot OEt2 have been studied by NMR spectroscopy. Dicationic dihydride complexes [CpRuH2(LH)](2+) [LH = dippaeH(+) (5a), (R,R)-dippachH(+) (5b)] and [Cp*RuH2(LH)](2+) [LH = dippaeH(+) (6a), (R,R)-dippachH(+) (6b)] result respectively from the protonation of either the monohydrides 1a,b or 2a,b or the dihydrides 3a,b or 4a,b at one of the NH groups of the phosphinoamine ligands by an excess of HBF4. These dicationic derivatives exhibit fluxional behavior in solution. In the course of the protonation of 1a with HBF4 center dot OEt2, a cationic dihydrogen complex and a dihydrogen-bonded derivative have been identified as intermediates by NMR spectroscopy. Another dihydrogen species, namely, [CpRu(H center dot center dot center dot HOOCPh)((R,R)-dippach)], was also identified in the course of the reaction of 1b with benzoic acid in toluene-d(8). The reaction of 1a with 0.5 equiv of 1,1,1,3,3,3-hexafluoroisopropanol generates a hydride species having a very short (T-1)(min) of 6.5 ms at 400 MHz, an experimental fact for which no satisfactory explanation has yet been found.