Abstract
A spectroscopic study of 1,5-benzodiazepines, their 2,3-dihydro-and 2,3,4,5-tetrahydro-derivatives, and the analogous 2,3 dihydro- and 2,3,4,5-tetrahydro-1,5-benzothiazepines is reported. New examples of the dihydro- and tetrahydro- derivatives have been synthesized. The least known tetrahydro- diazepines and thiazepines have been examined in most detail - vibrational, electronic and NMR spectroscopy, and mass spectrometry, have been employed to determine the effect of progressive methyl substitution upon the conformation of the seven-membered ring. When the ring is symmetrically substituted, inversion that is rapid on a NMR time scale takes place at room temperature. When asymmetrically substituted, the heterocycles exist in fixed chair conformations - a progressive flattening of the chair occurs with increase in methyl substitution. Compounds derived from the reaction of transition metal salts with 2,4-disubstituted-1,5-benzodiazepines and their monocations have been examined and the possibility of coordination of the diazepinium cation discussed. The compounds prepared are formulated as simple tetrahalometallates and metal sulphate salts of the diazepinium cation -a previously assigned structure for the latter salts is corrected. The structure of the anion in some diazepinium chlorocuprates has been found to depend upon the substitution of the diazepine ring. When 1,5-benzodiazepine bases are treated with metal salts, the base tends to revert to the delocalized cationic structure rather than coordinate to the metal. The possibility of a copper-promoted bromination of. the delocalized diazepinium cation has been investigated. Nickel(11) and copper(11) complexes of the tetrahydrobenzo-diazepines have been prepared. Progressive methyl substitution of the diazepine ring increases the ease of preparation and the stability of the complexes; with the 2,2,4-trimethyl-derivative, for example, square-planar complexes are obtained. A decrease in methyl substitution allows the approach of further coordinating molecules or ions and the formation of coordinate species.