New π-electron donors for organic metals: synthesis of substituted tetrathiafulvalenes with eight- and nine-membered dithiaheterocycles: crystal structure of 5,6,7,8-tetrahydro-1,3-dithiolo[4,5-b][1,4]dithiocine-2-thione

Abstract

Reaction of the dimercapto disodium salt 2 with 1,4-dibromobutane, dibromo-o-xylene, 1,8-bis(bromomethyl) naphthalene and 1,2,4,5-tetrakis(bromomethyl)benzene gave the thiones 3, 5, 8 and 11 respectively. The thiones 5 and 8 were oxidised to give the oxo derivatives 6 and 9. Coupling of the thiones 3, 5 and 8 or their oxo derivatives 6 and 9 in neat triethyl phosphite afforded new ndonors 4, 7 and 10 respectively. Reaction of 2 with dimethyltellurium dichloride gave di-(dithiolo)tetrathiocinedithione 15. The oxidation potentials of the donors 4, 7 and 10 are reported along with the preparation and electrical conductivity measurements of their charge-transfer complexes with 7,7,8,8-tetracyano-p-quinodimethane and 2,3-dichloro-5,6-dicyano-p-benzoquinone. The crystal structure of 5, 6,7,8-tetrahydro-1,3-dithiolo[4,5-b][1,4]dithiocine-2-thione 3 was determined by single-crystal X-ray diffraction. Compound 3 crystallizes in the monoclinic space group P2₁/n with unit-cell dimensions a=4.8048(6)Å, b=9.029(1)Å, c=23.250 Å, β=93.22(1), V=1028.0(2)ų, Z=4 and R=0.046.