Unique structural topologies involving metal-metal and metal-sulfur interactions: salts of [Ni(C3S5)(2)](x-) with cis-anti-cis-dicyclohexyl-18-crown-6 complexed counter ions

Preparation by electrocrystallisation has been carried out for the salts [Rb(anti-dchyl-18c6)](2)[Ni(dmit)(2)] 1, [Rb(anti-dchyl-18c6)][Ni(dmit)(2)] 2, [Cs(anti-dchyl-18c6)](2)[Ni(dmit)(2)] 3 and [Cs(anti-dchyl-18c6)(1.5)][Ni(dmit)(2)](6) 4 (anti-dchyl-18c6 = cis-anti-cis-dicyclohexyl-18-crown-6, dmit = C3S5). Salts 1 and 3 involve the planar dianionic nickel complex sandwiched by two metal-crown units. This leads to short Rb+. . . Ni and Rb+ . . . S interactions in 1 and the shortest recorded Cs+ . . . Ni distance of 3.47 Angstrom in 3, presumably stabilised by the four surrounding S atoms at 3.73-4.44 Angstrom. DFT calculations on the dianionic salts 1 and 3 indicate an essentially electrostatic interaction between the [Ni(dmit)(2)](2-) complex and the Rb+ or Cs+ ion and show frontier orbitals qualitatively similar to those previously derived from EHMO calculations on molecular conductors containing [Ni(dmit)(2)]. Salt 2 consists of non-stacked nickel complexes arranged in chains linked by S . . . Rb+ interactions through the terminal sulfurs with the Rb+ ion placed exactly within the plane of the crown oxygens. Magnetic susceptibility measurement indicated weak antiferromagnetic interactions. Salt 4 shows a 2-D sheet of nickel complexes stacked in a herringbone arrangement separated by layers of counter ions complexed by the crowns in a disordered manner with the anion : cation ratio of 6 : 1 uniquely high among [Ni(dmit)(2)](x-) salts. Salt 4 displays semiconductor behaviour with sigma (RT) = 10(-2) S cm(-1).