The reactions of ammonia, pyridine (py), N-methyl imidazole (N-Melm), tetrahydrothiophene (tht), and piperidine (pip) with Re(CO)3(H 2O)3+, 1+, were investigated employing aqueous conditions under atmospheric dioxygen. The reaction of Br in aqueous ammonia led to [Re(CO)3(NH3)3]Br (Br) as the only product isolated. For the aqueous reactions of Br with py, N-Melm, and tht, mixtures of products are formed because of competition between the bromide and added ligand, even when the ligand is present in excess. Substitution of the PF6- anion for Br- leads to the clean formation of [Re(CO)3L3][PF6] ([PF6]-[PF6]) for py, N-Melm, and tht, respectively, as the only products observed. Reaction of [PF6] with pip produces the dimeric species, (pip)(CO)3Re(μ-OH) 2Re(CO)3(pip), 6. Reactions of Br were also performed in methanol for comparison purposes. The reaction with pip in this solvent led to the analogous dimer, (pip)(CO)3Re(μ-OMe)2Re(CO) 3(pip), 7; however, reactions with py, N-Melm, and tht gave Re(CO)3L2Br, 8-10, respectively, as the only products. The crystal structures of compounds Br-10 are reported.