Tetrathiafulvalenes and Selenium-containing Analogues

The discovery that the charge-transfer salt derived from tetrathiafulvalene (54 R = H) and tetracyanoquinodimethane (55) has metal-like behaviour, and shows a remarkable electrical conductivity over a wide temperature range, has stimulated a large volume of work on the design and synthesis of organic metals .  

Details have been given for the preparation of tetrathiafulvalene (TTF) by deprotonation of 1,3-dithiolium fluoroborate and hexafluorophosphate. Improvements in the synthesis have been suggested, and modifications described for deuteriated TTF. Oxidation of the dihydro-compound (46) with manganese dioxide to give TTF has been reported.  

The dithiolium cation-deprotonation route has also been applied to the synthesis of various tetrasubstituted derivatives of TTF (54 R = Me, Et, Ph, 

A second route to TTF derivatives involves desulphurization of l,3-dithiole-2-thiones (or, better, deselenization of 2-selones see below) with phosphines or phosphites. For the preparation of tetracyano-TTF (54 R = CN), the use of triphenyl phosphite is recommended alternatively, 4,5-dicyano-l,3-dithiole-2-one is reported to be deoxygenated in high yield by trimethyl phosphite.  

Symmetrical bis(benzo)-derivatives of TTF have been prepared by the deprotonation route, by desulphurization with triethyl phosphite, by generating 

---