Formation of N-Hydroxyalkylpyridine-2-Carbox-Amidines and 2-Pyridinyl-2-Oxazolines in the Coordination Sphere of Nickel(ii)

Condensation of pyridine-2-carbonitrile (2-CNpy) with 2-aminoethanol (L1), l-amino-2-propanol (L2) and 2-amino-l-butanol (L3) in ethanolic solutions of Ni(II) salts proceeded readily at room temperature to form stable complexes, which contain the amino form of N-hydroxy-alkylpyridine-2-carboxamidines (amL-NH2). The crystal structure of complex [Ni(N-2-hydroxyethylpyridine-2-carboxamidine)2]Cl2 · 3.5H2O and IR data confirm N,N,O-coordination of N-hydroxyalkylpyridine-2-carboxamidines (via the nitrogen atom of the pyridine ring, the nitrogen atom of the C = N- group and the oxygen atom of the hydroxyl group). The electron density distribution and structure of the amino form of amL-NH2 are suitable for cyclization accompanied by ammonia elimination and formation of the appropriate oxazoline. On the other hand, substituted 2-amino-2-ethyl-l,3-propandiol (L4) formed in alcoholic solutions of Ni(II) complexes containing 2-(2-pyridinyl)-4-ethyl-4-hydroxymethyl-2-oxazoline (oxaL4) only. The influence of amino alcohols and nickel(II) salts, as well as reaction conditions on amidine or oxazoline formation is discussed.