Hydrogen-bonded layers directed by the [3-O3S-C6H4-PO3H]2- dianion: catena-poly[[silver(I)-mu-4,4'-bipyridine-kappa2N:N'] 3-[hydroxy(oxido)phosphinoyl]benzenesulfonate trihydrate] and catena-poly[[[tetraaquacobalt(II)]-mu-4,4'-bipyridine-kappa2N:N'] 3-[hydroxy(oxido)phosphinoyl]benzenesulfonate].

Both title compounds, {Ag(2)(C(10)H(8)N(2))(2).3H(2)O}(n), (I), and {Co(C(10)H(8)N(2))(2)(H(2)O)(4)}(n), (II), respectively, contain similar novel symmetric dimeric O(3)S-C(6)H(4)-PO(3)H anions formed via two shared (O...H...O) H atoms on twofold positions between two -PO(3)H(-) groups. The two-coordinate Ag(I) structure features one-dimensional polymeric chains of {Ag(4,4'-bipy)(2+)}(n) (4,4'-bipy is 4,4'-bipyridine), weakly linked by pi-pi interactions, separated by the anionic dimers which are stabilized into layers by hydrogen bonding to three water molecules. In (II), a twofold crystallographic axis runs through the one-dimensional {Co(4,4'-bipy)(H(2)O)(4)}(n) chains containing six-coordinate Co(II); three-dimensional packing is provided by hydrogen bonding using all sulfonate and -PO(3)H(-) O atoms as acceptors and the Co-bound water H atoms as donors. In this latter case, the benzenesulfonate aromatic rings are also constrained to a mirror plane. This report illustrates how a previously unreported dianion can affect the crystallization of polymeric metal complex cations.