First cation radical mixed-valence hybrid salts of the paramagnetic octahedral cluster Nb₆Cl₁₈^3-. Preparation, crystal structures, and conducting and magnetic properties of pentakis(2,3,6,7-tetramethyl-1,4,5,8-tetra-selena- and -thia-fulvalenium) hexachloro(dodeca-μ₂-chloro-octahedro-hexaniobate)

Electrically conducting single crystals of (D)5Nb 6Cl18(CH2Cl2)0.5 [D = 2,3,6,7-tetramethyl-1,4,5,8-tetra-selena- and -thia-fulvalene (TMTTF) and (TMTTF) in (1) and (2) respectively] have been grown electrochemically; their unique crystal structure shows a one-dimensional stack with a periodicity twice that of the Bechgaard salts; the observed Curie-Weiss behaviour of the magnetic susceptibility demonstrates the presence of one non-interacting spin per unit-cell; this is not purely a cluster spin as indicated by e.s.r. spectroscopy.