Polyhalogenated BEDT-TTF through chlorination (SO2Cl2, Cl2) and fluorination (®Selectfluor, XeF2) of 5,6-dihydro[1,3]dithiolo[4,5-b][1,4]dithiin-2-one

The electrophilic halogenation of the ethylenic bridge in the 5,6-dihydro[1,3]dithiolo[4,5-b][1,4]dithiin-2-one (1) with SO2Cl2, (R)Selectfluor [1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)] or XeF2 affords the corresponding monochloro, 1,2-dichloro and monofluoro derivatives 2, 3 and 6, respectively. Reaction with Cl-2 gives rise to a pentachloro derivative (5) with syn-Cl-2 addition across the unsaturated double bond of 1 characterised by single crystal X-ray diffraction. Homocoupling of 2, 3 or 6 in P(OMe)(3) affords the corresponding dichloro, tetrachloro and difluoro BEDT-TTFs 8, 9 and 10, respectively, whose electrochemical characteristics show the electron-withdrawing nature of the halogen substituents present on the ethylenic bridge. Electrocrystallisation of 9 in the presence of (n-Bu4N)(2)(Mo6Cl14) affords a mixed-valence salt formulated as [9](3)[Mo6Cl14], whose X-ray crystal structure has been determined and analysed.