A New Conducting Molecular Solid Based on the Magnetic [Ni(dmf)6]2+ Cation and on [Ni(dsit)2]22- (dsit=1,3-dithiole-2-thione-4,5-diselenolate) Showing an Unprecedented Anion Packing

The synthesis, X-ray structure, magnetic and transport properties of the compound Ni(dmf)6 [Ni(dsit)2]2 (dmf=dimethylformamide, DSIT=1,3-dithiole-2-thione-4,5-diselenolate) are described. This compound crystallizes in the monoclinic space group P21/c, with a=18.709 (6), b=22.975(5), c=20.418(5) ?, BETA=99.31(2)° and Z=6; its structure consists of [Ni (dsit)2]22- dimers and isolated [Ni(dmf)6]2+ cations both centrosymmetric and noncentrosymmetric. The dimers are packed forming chains along the [101] direction with short Se·Se interdimer contacts. Additional interchains S·S contacts render this structure a threedimensional character, never observed so far in other [Ni(dsit)2]- salts. This compound exhibits semiconducting behavior with a room temperature conductivity (1 S cm-1) much higher than those reported for other salts of the [Ni(dsit)2]- anion. Tight-binding band structure calculations were used to analyze the origin of the semiconducting properties of this salt. The magnetic susceptibility shows Curie behavior with C=1.25 emu K mol-1, typical of isolated Ni (II) ions as expected for the octahedrally coordinated [Ni(dmf)6]2+ cations.