title: Polymeric diaqua(mu(2)-2,2'-bipyrimidinyl-kappa4N1,N1':N3,N3')-di-mu(3)-hydroxy-bis(mu(5)-benzene-1,3,5-tricarboxylato-kappa5O1:O2:O3:O3:O5)tetracobalt(II) dihydrate.
abstract: The structure of the title compound, [Co(4)(C(9)H(3)O(6))(2)(OH)(2)(C(8)H(6)N(4))(H(2)O)(2)].2H(2)O, contains three separate species, namely the mu(5)-bridging C(9)H(3)O(6)(3-) anion, the doubly chelating and therefore mu(2)-bridging C(8)H(6)N(4) ligand (bipyrimidine, BPM), and the dihydrated diaquadihydroxy tetranuclear cationic cluster, [Co(4)(OH(-))(2)(H(2)O)(2)](6+).2H(2)O, which lies on a crystallographic centre of symmetry, as does the BPM ligand with, in this case, the centre of symmetry coincident with the midpoint of the C-C bond joining the six-membered rings. Within the cation cluster, the Co atoms of one pair are five-coordinate and those of the other six-coordinate.