The compound [Re-II(terpy)(PPh(3))(2)Cl](+) (with counterion Cl- (I) or OTf(-) (II)) has proven to be a useful synthon in the synthesis of a series of Re(I) and Re(III) compounds. Compound I can be oxidized in the presence of Cl- to form [Re-III(terpy)(PPh(3))Cl-2](+) (IV) or Re-III(terpy)Cl-3 (V). Compound II can be reduced in the presence of cyclohexenone to form Re-I(terpy)(PPh(3))Cl(eta(2)-cyclohexenone) (VI). The chloride on compound VI undergoes facile substitution to form a series of Re(I)-terpyridyl derivatives (VII-XIII). The electrochemistry of these compounds has been studied and compared to that of other known rhenium compounds using an electrochemical parametrization model. A correlation is drawn between the number and strength of pi-acidic ligands and the deviations of the observed II/I reduction potentials from the predicted values. An X-ray crystal structure determination for II is also reported. [Re-II(terpy)(PPh(3))(2)Cl]OTf (II) crystallizes in the triclinic space group P (1) over bar (No. 2) with Z = 2 and lattice parameters a 14.552(7) Angstrom, b = 15.726(7) Angstrom, c 12.215(3) Angstrom, alpha = 109.09(2)degrees, beta = 96.98(3)degrees, and gamma = 98.42(4)degrees at -80 degrees C.