The first three‐dimensional Fe III –Sr II heterometallic coordination polymer: poly[[diaquatetrakis(μ 3 ‐pyridine‐2,3‐dicarboxylato)diiron(III)strontium(II)] dihydrate]

The title compound, poly[[diaqua‐1κ 2 O ‐tetrakis(μ 3 ‐pyridine‐2,3‐dicarboxylato)‐2:1:2′κ 10 N , O 2 : O 2′ , O 3 : O 3′ ;2:1:2′κ 8 O 3 : O 3′ : N , O 2 ‐diiron(III)strontium(II)] dihydrate], {[Fe 2 Sr(C 7 H 3 O 4 ) 4 (H 2 O) 2 ]·2H 2 O} n , which has triclinic ( P ) symmetry, was prepared by the reaction of pyridine‐2,3‐dicarboxylic acid, SrCl 2 ·6H 2 O and Fe(OAc) 2 (OH) (OAc is acetate) in the presence of imidazole in water at 363 K. In the crystal structure, the pyridine‐2,3‐dicarboxylate (pydc 2− ) ligand exhibits μ 3 ‐η 1 ,η 1 :η 1 :η 1 and μ 3 ‐η 1 ,η 1 :η 1 ,η 1 :η 1 coordination modes, bridging two Fe III cations and one Sr II cation. The Sr II cation, which is located on an inversion centre, is eight‐coordinated by six O atoms of four pydc 2− ligands and two water molecules. The coordination geometry of the Sr II cation can be best described as distorted dodecahedral. The Fe III cation is six‐coordinated by O and N atoms of four pydc 2− ligands in a slightly distorted octahedral geometry. Each Fe III cation bridges two neighbouring Fe III cations to form a one‐dimensional [Fe 2 (pydc) 4 ] n chain. The chains are connected by Sr II cations to form a three‐dimensional framework. The topology type of this framework is tfj . The structure displays O—H...O and C—H...O hydrogen bonding.