The reactions of RuH2(H-2)(2)(PCy(3))(2) (1) with N-2, CO2 and CS2 afford respectively RuH2(N-2)(2)(PCy(3))(2) (2), RUH(O-2-CH)(H-2)(PCy(3))(2) (3), and RuH2(S2CH2)(PCy(3))(2) (4); the two former reactions are reversible under dihydrogen atmosphere. The reaction of 1 with pyrazole yields RuH(H-2)(NNC3H3)(NNHC3H3)(PCy(3))(2) (5), which shows hydrogen bonding between the pyrazole and pyrazolate groups. The pi-bonded phenoxo derivative RuH(eta(5)-C6H5O)(PCy(3))(2) (6) has been obtained by reaction of 1 with phenol. Complex 6 under H-2 yields RuH2(eta(6)-C6H5-OH)(PCy(3))(2) (7) whereas dehydrogenation of cyclohexanone occurs with or without hydrogen acceptor to give Ru(eta(5)-C6H5O)(C(6)H(10)PCy(2))(PCy3()) 8. Finally, 8 reacts with H-2 to give a mixture of 6 and 7.