New Organic Metals Based on BETS Compounds with MX4- Anions (BETS=bis(ethylenedithio)tetraselenafulvalene; M = Ga, Fe, In; X= Cl, Br).

Crystal structures and electrical properties of BETS compounds with tetrahedral anions, MX4− (BETS = bis(ethylenedithio)tetraselenafulvalene; M = Ga, Fe, In; X = Cl, Br) were examined. Every κ-type salt is metallic below 50 K. λ-(BETS)2FeCl4, which is isomorphous to the superconductor GaCl4 salt, undergoes a sharp metal-insulator transition at 8 K.