Methanolysis of 2-cyanopyridine in the coordination sphere of manganese(II). The structure of Mn₄L₆Cl₂ cluster (L = methyl picolinimidate)

Increased reactivities of molecules coordinated in metal complexes have wide applications in chemistry. The activation of ligands containing the nitrile group upon their coordination to a manganese ion has been exploited in addition reactions of nucleophiles such as amines, alcohols and water. The 2-cyanopyridine as a chelating bidentate ligand can be coordinated to manganese ion from two nitrogen atoms of pyridine ring and carbonitrile group in the presence of non-protonic solvents. The reaction of 2-cyanopyridine and Mn(II) in methanol solution led to the formation of a Mn₄L₆Cl₂ cluster 1 containing O-methyl picolimidate as a ligand (L). The coordination of 2-cyanopyridine to the Mn(II) ion as a chelating bidentate ligand activated the CN triple bond which subsequently suffered a nucleophilic attack by CH₃OH. Complex 1 was characterized by standard techniques including microanalysis, IR spectroscopy, ESI spectrometry, and magnetic susceptibility measurements. The crystal structure of 1 was determined by X-ray diffraction techniques, and the crystallographic studies revealed a planar-diamond array for 1 where the six monoanionic picolinimidates act as chelating ligands through the two nitrogen atoms.