1,2-Bis(anilido)ethane Complexes of Calcium and Potassium: Synthesis, Structures, and Catalytic Activity

Abstract

The metalation of 1,2-bis(anilino)ethane with excess KH leads to the formation of the potassium complex [(thf)3K2{1,2-(PhN)2C2H4}] (1). Complex 1 quantitatively reacts with anhydrous CaI2 in THF yielding insoluble KI and dinuclear [(thf)5Ca2{1,2-(PhN)2C2H4}2] (2) after crystallization from a mixture of THF and hexane. Addition of N,N,N′,N′′,N′′′,N′′′-hexamethyltriethylenetetraamine (hmteta) yields [(hmteta)Ca{1,2-(PhN)2C2H4}] (3). The complexes 1 and 2 proved to be inactive as catalysts in hydroamination reactions of diphenylbutadiyne with secondary amines. However, a mixture of 1 and 2 (K:Ca ratio of 2:1) mediated the addition of N-methyl-aniline and 1,2-bis(anilino)ethane to one of the C≡C triple bonds of diphenylbutadiyne. Addition of 18-crown-6 ether (18C6) leads to the formation of the sparingly soluble potassium complex [{(18C6)K}2{1,2-(PhN)2C2H4}] (5) and the insoluble calcium complex [(18C6)Ca{1,2-(PhN)2C2H4}] (6). The calciate-mediated hydroamination reaction is regiocontrolled, but E- and Z-isom...