TpOs(N)(OAc)(2) (2) is formed upon reaction of TpOs(N)Cl-2 (1) with excess silver acetate (Tp = hydrotrispyrazolylborate). Treatment of 2 with protic acids HX gives the osmium(VI) complexes TpOs(N)X-2, where X = trifluoroacetate (TFA, 3), trichloroacetate (TCA, 4), tribromoacetate (TBA, 5), bromide (6), oxalate (X2 = O2C2O2, 7), or nitrate (ONO2, 8). Cyclic voltammetry studies of 1-8 show irreversible reductions of Os-VI to Os-V, varying over a range of 0.63 V. Much smaller relative variations are observed in N-15 NMR chemical shifts, v(OsdropN) stretching frequencies, and optical absorbances. Compounds 1-8 all react with PPh3 by nucleophilic attack at the nitride ligand, yielding TpOs(NPPh3)X-2. The reactions are accelerated by more electron withdrawing ligands X. The relative rates correlate with the peak reduction potentials although the effect is small: the rates vary by only 10(2) while the 0.63 V change in E-p,E-c corresponds to a change in equilibrium constant for electron transfer of similar to10(11). Compounds 1-8 also react with triphenylboron, BPh3, with formation of borylanilido complexes TpOs[N(Ph)BPh2]X-2. However, rate constants for reactions with BPh3 to yield Os-IV boryl-amido complexes do not in general correlate with one-electron-reduction potentials. This is likely due to the mechanism of the BPh3 reactions being a two-step process and not simply nucleophilic attack.