Metal-promoted reactions of 2-cyanopyridine: iron(II), cobalt(II), nickel(II), and copper(II) complexes of O-methylpyridine-2-carboximidate

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Abstract
Reaction of 2-cyanopyridine (2-CNpy) with copper(II) chloride in methanol solution can give three different products, viz., [(2-CNpy)2CuCl2], (I); [(Mepy)CuCl2], (II)[Mepy =O-methylpyridine-2-carboximidate]; or [(Mepy)2(H2O)2Cu]Cl2, (III), (II) and (III) were also prepared directly from O-methylpyridine-2-carboximidate. Methyl 2-picolinate may be obtained in 78% yield from (II); this constitutes a new route to this otherwise difficulty accessible ester. Complexes of O-ethyl- and O-n-butyl-pyridine 2-carboximidates, analogous to (II), were prepared from 2-cyanopyridine with the appropriate alcohol as solvent. [(Mepy)2Cu](ClO4)2, [(Mepy)2(H2O)BrNi]Br, [(Mepy)3Co](ClO4)2, [(Mepy)2CoCl2], and [(Mepy)CoCl2],H2O were prepared from 2-cyanopyridine. [(Mepy)3Fe](ClO4)2,H2O is low-spin; this result, and the high value of Δ(12,800 cm.–1) found for [(Mepy)3Ni](ClO4)2, confirm that O-methylpyridine-2-carboximidate is a strong-field ligand of the α-di-imine type. [(np)CuCl2](np = 2-picolinic acid N-methylamide) and [(np)3Ni](ClO4)2 were prepared and their spectra compared with the isomeric complexes of O-methylpyridine-2-carboximidate. Pyridine 2-carboxamide was obtained in 54% yield via the copper(II)-promoted hydration of 2-cyanopyridine. Spectroscopic, magnetic, and conductimetric results for the complexes are presented and are briefly discussed.

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