Crystal structure of poly[[di-μ(2)-aqua-aqua­sodium] 4-amino-3,5,6-tri­chloro­pyridine-2-carboxyl­ate trihydrate], the sodium salt of the herbicide picloram

In the structure of the title complex, {[Na(H(2)O)(3)](C(6)H(2)Cl(3)N(2)O(2))·3H(2)O}(n), the sodium salt of the herbicide picloram, the cation adopts a polymeric chain structure, based on μ(2)-aqua-bridged NaO(5) trigonal–bipyramidal complex units which have, in addition, a singly bonded water mol­ecule. Each of the bridges within the chain, which extends parallel to the a axis, is centrosymmetric, with Na⋯Na separations of 3.4807 (16) and 3.5109 (16) Å. In the crystal, there are three water mol­ecules of solvation and these, as well as the coordinating water mol­ecules and the amino group of the 4-amino-3,5,6-tri­chloro­picolinate anion, are involved in extensive inter-species hydrogen-bonding inter­actions with carboxyl and water O atoms, as well as the pyridine N atom. Among these associations is a centrosymmetric cyclic tetra­water R (4) (4)(8) motif, resulting in an overall three-dimensional structure.