Heterometallic coordination framework by sodium carboxylate subunits and cobalt (III) centers obtained from a highly hydrogen bonding stabilized cobalt (II) monomeric complex

•Coordination octahedral cobalt and nickel complexes•Formation of new unusual structures with Z′ = 4•Good correlation of Wiberg Bond Indices (WBIs) with experimental hydrogen bonding interactions•Heterometallic coordination framework obtained by addition of sodium hydroxide•Oxidation of the cobalt atom in (3) confirmed by reduction of the coordination bond distances

Coordination cobalt and nickel complexes (1) and (2) were obtained serendipitously by the reaction of M(NO3)2·6H2O (M = Co and Ni) and methyliminodiacetic acid (H2L) in a mixture of solvents. The X-ray diffraction showed the unusual structures with Z′ = 4 of (1) and (2), showing the four monomers highly stabilized by hydrogen bonding interactions which corresponds to the tris-(aqua)-(N-methyliminodiacetato)-cobalt (II) and nickel (II) respectively. The Wiberg Bond Indices (WBIs) were computed on (1) and (2) to evaluate the stability of the hydrogen bonding interactions and showed a good correlation with the experimental X-ray diffraction data. Finally, the complex [Co (L)2 Na]n (3) corresponds to the heterometallic coordination framework which was obtained by addition of a second equiv. of methyliminodiacetic acid (H2L) in basic sodium hydroxide media. The oxidation of the cobalt atom in (3) was confirmed by the experimental coordination bond distances observed by XRD, which are in the range from 1.882 to 1.957 Å.

Graphical abstractCoordination cobalt and nickel complexes (1) and (2) were obtained serendipitously by the reaction of M(NO3)2·6H2O (M = Co and Ni) and methyliminodiacetic acid (H2L) in a mixture of solvents. The X-ray diffraction showed the unusual structures with Z′ = 4 of (1) and (2), showing the four monomers highly stabilized by hydrogen bonding interactions which corresponds to the tris-(aqua)-(N-methyliminodiacetato)-cobalt (II) and nickel (II) respectively.Figure optionsDownload full-size imageDownload as PowerPoint slide