SYNTHESIS, STRUCTURE AND PHYSICAL-PROPERTIES OF TETRATHIAFULVALENIUM SALTS OF THE FERRACARBORANE COMPLEX COMMO-[3,3'-FE(1-(C4H3S)-1,2-C2B9H10)(2)]

The sandwich complex commo-[3,3'-fe{1-(C4H3S)-1.2-C2B9H10}(2)](-)1 and its tetrathiafulvalenium salts [ttf](5)[Fe(C2B9H10C4H3S)(2)] 2 and [t tf] [Fe(C2B9H10C4H3S)(2)] 3 were synthesised in order to study the eff ect of the thiophene:(C4H3S) group on the crystal packing, electrical and magnetic properties of ttf-metallacarborane salts. The crystal str ucture of 2 features unusual two-dimensional networks of ttf units whi ch extend in the a and c directions. Each ttf sheet contains stacked t rimers of ttf units, which propagate along the a direction, and bridgi ng ttf units, which lie between the ttf stacks approximately orthogona lly to the ttf units within the trimers. The trimers are linked along the c direction via short S ... S contacts (3.56 Angstrom) with these bridging ttf units. In contrast, the crystal structure of compound 3 c ontains discrete stacked dimers of [ttf](.+) cations. Whilst crystals of 2 are semiconducting (sigma(300K) = 2 x 10(-3) S cm(-1)) with an ac tivation;energy of 0.22 eV, those of 3 are insulating (sigma(290K) les s than or equal to 10(-7) S cm(-1)). Both compounds exhibit weak ferro magnetic interactions between the unpaired spins of their [Fe(C2B9H10C 4H3S)(2)](-) anions, with small positive Weiss constants of 1.9 and 0. 5 K respectively.