The labile nature of the coordinated water ligands in the organometallic aqua complex [Ru(dppe)(CO)(H2O)(3)][OTf](2) (1) (dppe = Ph2PCH2CH2PPh2; OTf = OSO2CF3) has been investigated through substitution reactions with a range of incoming ligands. Dissolution of 1 in acetonitrile or dimethyl sulfoxide results in the facile displacement of all three waters to give [Ru(dppe)(CO)(CH3CN)(3)][OTf](2) (2) and [Ru(dppe)(CO)(DMSO)(3)][OTf](2) (3), respectively. Similarly, 1 reacts with Me3CNC to afford [Ru(dppe)(CO)(CNCMe3)(3)][OTf](2) (4). Addition of 1 equiv of 2,2'-bipyridyl (bpy) or 4,4'-dimethyl-2,2'-bipyridyl (Me(2)bpy) to acetone/water solutions of 1 initially yields [Ru(dppe)(CO)(H2O)(bpy)][OTf](2) (5a) and [Ru(dppe)(CO)(H2O)(Me(2)bpy)][OTf](2) (6a), in which the coordinated water lies trans to CO. Compounds 5a and 6a rapidly rearrange to isomeric species (5b, 6b) in which the ligated water is trans to dppe. Further reactivity has been demonstrated for 6b, which, upon dissolution in CDCl3, loses water and coordinates a triflate anion to afford [Ru(dppe)(CO)(OTf)(Me(2)bpy)][OTf] (7). Reaction of 1 with CH3CH2CH2SH gives the dinuclear bridging thiolate complex [{(dppe)Ru(CO)}(2)(mu-SCH2CH2CH3)(3)][OTf] (8). The reaction of 1 with CO in acetone/water is slow and yields the cationic hydricle complex [Ru(dppe)(CO)(3)H][OTf] (9) via a water gas shift reaction. Moreover, the same mechanism can also be used to account for the previously reported synthesis of 1 upon reaction of Ru(dppe)(CO)(2)(OTf)(2) with water (Organometallics 1999, 18, 4068).