Synthesis and experimental electron density of bis(heterocyclic) azines:: The case of 6,6′-bis(chloromethyl)-2,2′-bipyrazine

The synthesis and reactivity of mono- and bis(chloromethyl)-2,2'-bipyrazines toward nucleophiles are reported. The reactivity of the bipyrazine ring is explained in terms of allylic substitution and rearrangement mechanisms. A new family of monofunctionalized bipyrazine derivatives as molecular building blocks for supermolecules has been obtained, opening access to unsymmetrical ligands. The low-temperature crystallographic structure and the experimental electron density distribution of 6,6'-bis(chloromethyl)-2,2'-bipyrazine have been determined on the basis of high-resolution X-ray diffraction data. The electron density of the molecule has been accurately analyzed using the topological properties of its gradient and Laplacian features. The reactivity of these bidentate molecules in metal complexation is related to the shape of the atomic basins and may be explained in terms of a key/lock-type interaction. The results are compared with corresponding data for 2,2'-dimethyl-6,6'-diphenyl-4,4'-bipyrimidine.