A systematic substitution of the terminal chlorides coordinated to the hexanuclear cluster [Re6S8Cl6](4-) has been conducted. The following complexes: [Re6S8(PEt3)Cl-5](3-) (1), cis- (cis-2) and trans-[Re6S8(PEt3)(2)Cl-4](2-) (trans-2), mer- (mer-3) and fac[Re6S8(PEt3)(3)Cl-3](-) (fac-3), and cis- (cis-4) and trans-[Re6S8(PEt3)(4)Cl-2] (trans-4) were synthesized and fully characterized. Compared to the substitution of the halide ligands of the related [Re6S8Br6](4-) and [Re6Se8I6](3-) clusters, the chloride ligands are slower to substitute which allowed us to prepare the first monophosphine cluster (1). In addition, the synthesis of fac-3 was optimized by using cis-2 as the starting material, which led to a significant increase in the overall yield of this isomer. Notably, we observed evidence of phosphine isomerization taking place during the preparation of the facial isomer; this was unexpected based on the relatively inert nature of the Re-P bond. The structures of Bu4N+ salts of trans-2, mer-3, and fac-3 were determined using X-ray crystallography. All compounds display luminescent behavior. A study of the photophysical properties of these complexes includes measurement or the excited state lifetimes (which ranged from 4.1-7.1 mu s), the emission quantum yields, the rates of radiative and non-radiative decay, and the rate of quenching with O-2. Quenching studies verify the triplet state nature of the excited state.