Carboxylatobis(pentafluorophenyl)thallium(III) compounds, Tl(OCOR)(C6F5)2 (R = Ph, Me, or C6F5), have been prepared by a metathesis reaction between bromobis(pentafluorophenyl)thallium(III) and the appropriate sodium or ammonium carboxylate in aqueous ethanol. They are considered to have dimeric structures with bridging carboxylate groups. With 1, 10- phenanthroline (phen), the complexes Tl(OCOR)(C6F5)2 phen, which are monomeric in benzene and acetone, are obtained. The complexes, Tl(OCOR)(C6F6)2 bipy (bipy = 2, 2'-bipyridyl; R = Ph or Me) can be prepared only by using excess ligand. They decompose to Tl(OCOR)(C6F5)2 compounds on attempted recrystallization, partly dissociate into Tl(OCOR)(C6F5)2 and bipyridyl in benzene and acetone, and undergo ligand exchange with 1, 10-phenanthroline to give Tl(OCOR)(C6F5)2 phen complexes. By contrast, Tl(OCOC6F5)-(C6F5)2 bipy has been prepared without using excess ligand and can be recrystallized unchanged. It is monomeric in benzene, but dissociates slightly in acetone. The complexes, Tl(OCOR)(C6F5)2(phen or bipy), are considered to contain five-coordinate thallium.