Acidolysis of the complexes [Pt(CH3)(terpy)]Y (Y = PF6, CH3SO3, CF3SO3, ClO4, BF4; terpy = 2,2':6',2 ''-terpyridine) with an equimolar amount of CH3SO3 in 2,2,2-trifluoroethanol (TFE) affords the corresponding methanesulfonato derivatives [Pt(OSO2CH3)(terpy)]Y. When Y = NO3 a nearly equimolar mixture of the methanesulfonato and nitrato complexes is obtained, whereas the reaction of [Pt(CH3)(terpy)](CF3SO3) with triflic acid in either dry TFE or CH2Cl2 gives the aqua species [Pt(terpy)(H2O)](SO3CF3)(2), whose X-ray crystal structure is reported. This structure shows hydrogen bonding between the coordinated water molecule and two triflate ions. H-1 NMR evidence is reported that suggests that this hydrogen bonding is partially retained in CD3NO2 solution. The new hydroxido-bridged dimers [Pt-2(mu-OH)(terpy)(2)](X) [X = (ClO4)(3), (PF6)(2)(CF3SO3) (12)] have been isolated and their X-ray crystal structures determined. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).