A new coordination mode of 6-methyl­nicotinic acid in trans-tetra­aquabis­(6-methyl­pyridine-3-carboxyl­ato-κO)cobalt(II) tetra­hydrate

The title compound, [Co(C₇H₆NO₂)₂(H₂O)₄]·4H₂O, contains a Co^II ion lying on a crystallographic inversion centre. The Co^II ion is octa­hedrally coordinated by two 6-methyl­pyridine-3-carboxyl­ate ligands in axial positions [Co—O = 2.0621 (9) Å] and by four water mol­ecules in the equatorial plane [Co—O = 2.1169 (9) and 2.1223 (11) Å]. There are also four uncoordinated water mol­ecules. The 6-methyl­pyridine-3-carboxyl­ate ligands are bound to the Co^II ion in a monodentate manner through a carboxyl­ate O atom. There is one strong intra­molecular O—H...O hydrogen bond, and six strong inter­molecular hydrogen bonds of type O—H...O and one of type O—H...N in the packing, resulting in a complex three-dimensional supra­molecular structure.