The structure of α‐(1,2‐dithiole‐3‐ylidene) ketones and α‐(1,2‐dithiole‐3‐ylidene) aldehydes studied by means of n.m.r. spectroscopy

Abstract

Abstract1H and 13C n.m.r. studies of a series of twelve 1,2‐dithiole‐3‐ylidene ketones and aldehydes have shown that the geometry of the carbon backbone is the same as found in 1,6,6aλ4‐trithiapentalenes. No evidence has been found which favours a bicyclic structure for the system. A linear correlation of observed 13C chemical shifts with calculated charge densities is found to be valid. The observations are in agreement with a structure which is a hybrid between a true ketonic structure and a true mesoionic structure.By using the difference in the 13C chemical shifts of ortho and meta carbon atoms in substituent phenyl groups it is possible to qualify the degree of coplanarity of the phenyl groups with the backbone of the molecule.