On the Problem of Monodentate Coordination of Carboxylic Acid Hydrazides

The examples of monodentate coordination of the chelatophoric group in the X-ray structurally characterized metal coordination compounds with arylhydroxycarboxylic acid hydrazides are analyzed. It is established that the opening of the five-membered chelate ring, stable under ordinary conditions, and the violation of the Chugaev ring rule are caused by the pi-pi interaction of the dichloro substituted benzene rings of the organic radicals of hydrazides and by the blocking of the uncoordinated carbonyl oxygen atom by strong hydrogen bonds.