While protonation (HBF4 or HO3SCF3 = HOTf) or methylation (MeOTf) of Os(H)(2)X(2)L(2) (L = (PPr3)-Pr-i, X = Cl, Br) abstracts halide and causes aggregation to form (L(2)OsH(2))(2)(mu-X)(3)(+), protonation of Os(H)(2)I(2)L(2) forms a species whose -7.5 ppm H-1 NMR chemical shift has a short T-1min characteristic of an H-2 complex (or short H/H contact). This is also supported by a significant isotopic perturbation of resonance for OsH(3)I(2)L(2)(+), although no J(HD) is observed in OsHD(2)I(2)L(2)(+). In contrast, Os(H)(2)I(2)L(2) is converted by MeOTf into L(2)Os(H)(2)(OTf)I, then L(2)-Os(H)(2)(OTf)(2), a non-octahedral Lewis acid which binds H2O to form the intramolecularly hydrogen bonded L(2)Os(H)(2)(OTf)(2)(H2O), whose intramolecular fluxionality has been characterized (H-1 and P-31 NMR). The complexes L(2)Os(H)(2)(OR(f))(2) (OR(f) = OCH2CF3 and OCH(CF3)(2)) are synthesized from L(2)Os(H)(2)Cl-2 and TlOR(f). The X-ray structure of L(2)Os(H)(2)(OCH2CF3)(2) shows evidence for O-->Os pi-donation. Protonation of L(2)Os(H)(2)(OR(f))(2) (R(f) = CH(CF3)(2)) with HBF4 forms (L(2)OsH(2))(2)(mu-F)(3)(+), which is also inefficiently formed by fluoride abstraction (25 degrees C) by L(2)Os(H)(2)(OCH2CF3)(2), even in the solid state. Protonation of the monochloride L(2)Os(H)(3)Cl gives equimolar (L(2)OsH(2))(2)(mu-Cl)(3)(+) and L(2)OsH(7)(+), both the initial site of protonation remains unknown. Crystal data for [OsH2((PPr3)-Pr-i)(2)(OTf)(2)][OsH2((PPr3)-Pr-i)(2)(OTf)(2)(H2O) ] at -172 degrees C : a = 19.916(3) Angstrom, b = 20.260(4), c = 19.824(3), alpha = 115.54(1)degrees, beta = 115.03(1), gamma = 63.57(1) with Z = 4 in space group P (1) over bar. Crystal data for ((PPr3)-Pr-i)(2)(OsH2(OCH2CF3)(2) at -175 degrees C : a = 8.831(2), b = 16.680(4), c = 19.820(5), beta = 93.97(1)degrees with Z = 4 in space group P2(1)/c.