Three cobalt(II) complexes of Py(3)PH(2) (H’s are the dissociable amide H’s), a strong-field ligand with two peptide groups, have been synthesized. They are [Co(Py(3)P)(H2O)]ClO4 . H2O (6), [Co(Py(3)P)(OH)] (7), and [Co(Py(3)P)(OO(t)Bu)].2CH2Cl2 (8). Complex 6 crystallizes in the monoclinic space group C2 with a = 22.695(6) Angstrom, b = 10.284(2) Angstrom, c = 10.908(3) Angstrom, alpha = 90 degrees, beta = 112.17(2)degrees, gamma = 90 degrees, V = 2357.7(10) Angstrom(3) and Z = 4. Its structure has been refined to R = 3.91% on the basis of 1844 I > 2 sigma(I) data. Complex 8 crystallizes in the monoclinic space group P2(1)/n with a = 16.720(4) Angstrom, b = 10.641(3) Angstrom, c = 16.776(3) Angstrom, alpha = 90 degrees, beta = 99.76(2)degrees, gamma = 90 degrees, V = 2941.5(12) Angstrom(3), and Z = 4.