Compounds that contain the anion [MeReO(edt)(SPh)](-) (3(-)) were synthesized with the countercations 2-picolinium (PicH(+)3(-)) and 2,6-lutidinium (LutH(+)3(-)), where edt is 1,2-ethanedithiolate. Both PicH(+)3(-) and MeReO(edt)(tetramethylthiourea) (4) were crystallographically characterized. The rhenium atom in each of these compounds exists in a five-coordinate distorted square pyramid. In the solid state, PicH(+)3(-) contains an anion with a short (d(SH) = 232 pm) and nearly linear hydrogen-bonded (N-H...S) interaction to the cation. Ligand substitution reactions were studied in chloroform. Displacement of PhSH by PPh3 follows second-order kinetics, d[MeReO(edt)(PPh3)]/dt = KPicH(+)3(-)][PPh3], whereas with pyridines an unusual form was found, d[MeReO(edt)(Py)]/dt = KPyH(+)3(-)][Py]2, in which the conversion of PicH(+)3(-) to PyH(+)3(-) has been incorporated. Further, added Py accelerates the formation of [MeReO(edt)(PPh3)], v = k(.)[PicH(+)3(-)].[PPh3].[Py]. Compound 4, on the other hand, reacts with both PPh3 and pyridines, L, at a rate given by d[MeReO(edt)(L)]/dt = k-[4]-[L]. When PicH(+)3(-) reacts with pyridine N-oxides, a three-stage reaction was observed, consistent with ligand replacement of SPh- by PyO, N-O bond cleavage of the PyO assisted by another PyO, and eventual decomposition of MeRe(O)(edt)(OPy) to MeReO3, Each of first two steps showed a large substituent effect; Hammett analysis gave rho(1) = -5.3 and rho(2) = -4.3.