Transition metal complexes with pyrazole-based ligands. XIX. Diaquabis(3,5-dimethyl-1H-pyrazole-1-carboxamidine-kappa2N,N')metal(II) dinitrate, with metal = Co and Ni.

The two title isostructural and isomorphous complexes, [M(C6H10N4)2(H2O)2](NO3)2 (M is Co or Ni), contain the transition metal in a distorted octahedral geometry, coordinated by four N atoms of two neutral bidentate organic ligands in the equatorial plane and two water O atoms molecules in the axial positions. The cation is centrosymmetric, with the transition metal located on an inversion centre. The structures are stabilized by a three-dimensional network of hydrogen bonding.