Crystal structure and conformation of 3-[bis(methylthio)methylene]-pentane-2,4-dione

Abstract

3-[Bis(methylthio)methylene]pentane-2,4-dione (3) crystallises in space group P2₁2₁2, Z= 2, with a= 8.05(1), b= 7.97(1), c= 8.10(1)Å. The molecule is slightly twisted about the axis of the carbon double bond, while its two acyl groups take up a highly twisted E,E-conformation. This latter feature is shown to explain certain unusual features in its i.r. spectrum, which is contrasted with those characteristic of other conformations. It is concluded on spectroscopic evidence that the E,E-conformation is also found for this molecule in solution. The structure was determined from diffractometer data and refined to R 0.045 for 731 observed intensities.