Both title compounds, {[Ag(2)(C(10)H(8)N(2))(2)](C(6)H(5)O(6)PS).3H(2)O}(n), (I), and {[Co(C(10)H(8)N(2))(2)(H(2)O)(4)](C(6)H(5)O(6)PS)}(n), (II), respectively, contain similar novel symmetric dimeric [O(3)S-C(6)H(4)-PO(3)H](2-) 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)(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)](2+)}(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.