CRYSTAL-STRUCTURES AND PHYSICAL-PROPERTIES OF BEDT-TTF CHARGE-TRANSFER SALTS WITH (MO6CL8)X-6(2-) ANIONS (BEDT-TTF = BIS(ETHYLENEDITHIO)TETRATHIAFULVALENE, X = CL, BR)

The crystal structures of three charge transfer salts of BEDT-TTF (bis (ethylenedithio)tetrathiafulvalene) with metal cluster anions [Mo6Cl8] X-6(2-)(X = Cl, Br) are reported, together with their electrical condu ctivity and magnetic properties. beta ''-(BEDT-TTF)(4) [Mo6Cl8]Br-6 . 2THF is triclinic P (1) over bar, a 9.690(2), b 12.540(5), c 19.509(5) Angstrom, gamma 92.89(2)degrees, Z = 1 and isostructural with the cor responding X = Cl salt. Both salts show metal-insulator transitions, a t 190 and 265 K, respectively. (BEDT-TTF)(4)[Mo6Cl8]Cl-6 . 2CH(2)Cl(2) is triclinic P (1) over bar, a 10.290(1), b 12.877(1), c 18.024(3) An gstrom, gamma 91.50(1)degrees, Z = 1 and likewise undergoes a metal-in sulator transition, at 60 K. Though the BEDT-TTF packing mode is also beta '', the symmetry of the stacks is different. alpha-(BEDT-TTF)(4) [Mo6Cl8]Cl-6 . 2DMF is monoclinic P2(1)/n, a 9.676(9), b 10.20(1), c 4 3.37(5)degrees, Z = 2. It is semiconducting due to charge localization within the BEDT-TTF layer.