Steric and Conjugational Electronic Effects on the Configuration of Acylated Hydrazines

Article abstract of DOI:10.1021/ja00275a038

The crystal structures of twelve N,N'-acylated cyclic hydrazines are described.In five adducts of 1,2,4-triazolidine-3,5-dione with various cyclopentadiene derivatives, it is shown that the configuration of the triazolidinedione moiety with respect to the bicycloheptyl rings is highly sensitive to very small differences in steric effects.The degree of flattening of the N atoms at the N-N bond is determined by the steric repulsions of the substituents.The average valence angle (α_av) at the nitrogens ranges between 110.5 and 112.0 deg.Increasing the size of N,N' rings and replacing the urea-type nitrogen of the triazolinedione ring by carbon is shown to cause significant flattening at the hydrazine nitrogens, and five of the other seven structures described here are nearly flat at nitrogen (α_av greater than 119 deg).