The solution chemistry of cobalt(II) ketophosphine complexes CoX(2)[Ph(2)PCH(2)C(O)Ph](2) (1a, X = Cl; 1b, X = Br; Ic, X = I):has been examined and compared to that of [CoX(2)(PPh(3))(2)] (2a, X = Cl; 2b, X = Br; 2c, X = I). All the complexes undergo a tetrahedral-octahedral equilibrium in methanol. This is facilitated by solvent coordination rather than-by the ligand’s keto functions. Some degree of ligand displacement also occurs. The crystal structure of la has been elucidated, showing a pseudotetrahedral cobalt(II) geometry. Along interligand hydrogen-bond, not present in powder samples, is observed between the methylene group of a Ph(2)PCH(2)C(O)Ph ligand and the ketone function of the other Ph(2)PCH(2)C(O)Ph ligand. la reacts with Na[Co(CO)(4)] to afford-the crystallographically characterized, metal-metal bonded centrosymmetric complex Co-2(CO)(6)[Ph(2)PCH(2)C(O)Ph](2) (5) (C = Co = 2.666-(1) Angstrom). The reactivity of 1a with AgBF4 and TlPF6 has also been examined and compared to that of 2a where the latter is reacted in the presence and absence of excess phosphine. Notable reaction products include the square planar cobalt(II) complex [Co{Ph(2)PCH(2)C(O)Ph}{Ph(2)PCH(2)C(O)Ph}Cl]PF6 (6), which slowly transforms;in solution to the octahedral complex [Co{Ph(2)PCH(2)C(O)Ph}(2){Ph(2)PCH(2)C(O)Ph}Cl]PF6 (7). Reaction with AgBF4 under similar conditions affords the silver phosphine complex Ag{Ph(2)PCH(2)C(O)Ph(2)Cl} (8). 2a reacts with AgBF4 to give [Ag-(PPh(3))(2)]BF4, but additionally in the presence of PPh(3) gives(Ph(3)P)(2)Ag(mu-Cl)(2)Co(mu-Cl)(2)Ag(PPh(3))(2) (13). The latter formulation involving a central CoCl42- core, and an almost linear Ag-Co-Ag arrangement has been confirmed by single-crystal X-ray diffraction. The solid state structures of 1a, 5, and 13.0.5OEt(2) have been determined by single-crystal X-ray analysis. 1a crystallizes in the monoclinic space group P2(1)/c with Z = 4 in a unit cell of dimensions a = 10.985(2) Angstrom, b = 17.236(4) Angstrom, c = 19.547(4) Angstrom, and beta = 104.87(2)degrees. 5 crystallizes in the triclinic space group P ($) over bar 1 with Z = 1, a = 8.916(2) Angstrom, b = 11.177(7) Angstrom, c = 12.009(4) Angstrom, alpha = 81.15(5)degrees, beta = 76.39(2)degrees, and gamma = 67.47(3)degrees. Complex 13-0.5OEt(2), crystallizes in the monoclinic space group P2(1)/c with Z = 8, a = 21.840(5) Angstrom, b = 17.664(6) Angstrom, c = 36.890(7) Angstrom, and beta = 93.14(2)degrees.