Coordination chemistry of 2,4′-bipyridine. Synthesis and structures of Co(2,4′-bipyridine)2(NO3)2(H2O) and Cd(2,4′-bipyridine)2(NO3)2(H2O)2

Synthesis and characterization of two coordination complexes of 2,4′-bipyridine, Co(2,4′-bipyridine) 2 (NO 3 ) 2 (H 2 O) ( 1 ), and Cd(2,4′-bipyridine) 2 (NO 3 ) 2 (H 2 O) 2 ( 2 ), are described. Complex 1 was obtained by reacting Co(NO 3 ) 2 · 6H 2 O and 2,4′-bipyridine in a mixture of water and ethanol at room temperature, while 2 was synthesized from Cd(NO 3 ) 2 · 4H 2 O and 2,4′-bipyridine under hydro(solvo)thermal conditions at 90°C. In both complexes the metal centers only coordinate to the 4-pyridyl nitrogen atoms of the 2,4′-bipyridine ligands, with the rest of the coordination sites occupied by nitrate groups and water molecules. In 1 , the 2-pyridyl nitrogen atoms of the 2,4′-bipyridine ligands form intermolecular hydrogen bonds with both hydrogen atoms of the coordinated water molecule, resulting in a two-dimensional (2-D) polymeric network. In 2 , all the hydrogen atoms of the two coordinated water molecules are engaged in intermolecular hydrogen bonding with the 2-pyridyl nitrogen atoms of the 2,4′-bipyridine ligands and the oxygen atoms of the coordinated nitrate group; a 2-D hydrogen-bonded polymeric network is also obtained. Complexes 1 and 2 are the first coordination complexes of 2,4′-bipyridine to be characterized by X-ray crystallography.