We report the preparation, crystallization, and molecular structures of the redox pair (octaethylporphinato)bis(pentamethylene sulfide)osmium(II) and (octaethylporphinato)bis(pentamethylene sulfide)osmium(III) hexafluorophosphate. Both complexes have the osmium atom centered in the porphyrin plane with required inversion symmetry. The average Os-II = N-p 2.050(9) Angstrom and the axial Os-II-S distance is 2.352(2) Angstrom. The average Os-III-N-p is possibly shorter, at 2.046(2) Angstrom, and the axial Os-III-S distance is longer, at 2.382(2) Angstrom. Crystal data for [Os(OEP)(PMS)(2)]: a = 10.540(6) Angstrom, b = 10.620(6) Angstrom, c = 11.001(4) Angstrom, alpha = 99.21(3)degrees, beta = 95.35(3)degrees, gamma = 117.41(3)degrees, triclinic, space group P (1) over bar, V = 1059.3 Angstrom(3), Z = 1, unique observed data = 4895, R(1) = 0.047, R(2) = 0.063. Crystal data for [Os(OEP)(PMS)(2)]PF6: a = 10.449(8) Angstrom, b = 11.161(7) Angstrom, c = 11.523(2) Angstrom, alpha = 98.04(3)degrees, beta = 104.63(2)degrees, gamma = 111.93(7)degrees, triclinic, space group P (1) over bar, V = 1164.4 Angstrom(3), Z = 1, unique observed data = 5390, R(1) = 0.036, R(2) = 0.047.