Reaction of [NEt4](2)[ReBr3(CO)(3)] with 2,4-pentanedione (acac) yields a complex of the type fac-Re(acac)(OH2)(CO)(3) (1) under aqueous conditions. 1 was further reacted with a monodentate ligand (pyridine) to yield a fac-Re(acac)(pyridine)(CO)(3) complex (2). Complex 1 was found to react with primary amines to generate a Schiff base (imine) in aqueous solutions. When a mixed-nitrogen donor bidentate ligand, 2-(2-aminoethyl)pyridine, that has different coordination affinities for fac-Re(acac)(OH2)(CO)(3) was utilized, a unique tridentate ligand was formed in situ utilizing a metal-assisted Schiff base formation to yield a complex fac-Re(CO)(3)(3[(2-phenylethyl)imino]-2-pentanone) (3). Tridentate ligand formation was found to occur only with the Re-coordinated acac ligand. Reactions of acac with fac-Re(CO)(3)Br(2-(2-aminoethyl)pyridine) (4) or a mixture of [NEt4](2)[ReBr3(CO)(3)], acac, and 2-(2-aminoethyl)pyridine did not yield the formation of complex 3 in water.