ANTIFERROMAGNETIC INTERACTIONS IN CHARGE-TRANSFER SALTS OF MOLYBDOCENE DITHIOLENE COMPLEXES - THE EXAMPLE OF [CP(2)MO(DDDT)][TCNQ]

Cp(2)Mo(IV)(dithiolene) complexes are prepared by reaction of Cp(2)MoCl(2) with the dithiolene ligands dmit(2-) (2-thioxo-1,3-dithiole-4,5-dithiolate), dmio(2-) (2-oxo-1,3-dithiole-4,5-dithiolate), or dddt(2-) (5,6-dihydro-1,4-dithiine-2,3-dithiolate). Two reversible oxidation waves are observed by cyclic voltammetry for each complex. Cp(2)Mo(dddt) crystallizes in the orthorhombic system, S. G. Pna2(1), with a 16.608(3) Angstrom, b = 11.568(2) Angstrom, c = 7.724(1) Angstrom, and Z = 4. The MoS2C2 plane is folded along the S-S axis by 13(1)degrees. Oxidation of Cp(2)Mo(dddt) with TCNQ affords an insulating 1:1 salt which crystallizes in the triclinic system, S. G. P-1, with a = 9.597(1) Angstrom, b = 10.543(4) Angstrom, c = 12.460(3) Angstrom, alpha = 84.41(2)degrees, beta = 80.94(2)degrees, gamma = 89.41(2)degrees. In the 17-electron Cp(2)Mo(dddt)(.+) cation, the MoS2C2 plane is now folded along the S-S axis by 32.3(2)degrees. Those distortions upon electron count are rationalized by extended Huckel calculations. The structure of [Cp(2)Mo(dddt)][TCNQ] can be described as strongly dimerized (TCNQ(2))(2-) moieties separated by chains of alternatingly spaced Cp(2)Mo(dddt)(.+) cations. The latter exhibit one-dimensional [J/k = -27 +/- 1 K, alpha J = (0-0.2)J] antiferromagnetic interactions, as deduced from-the temperature variations of the magnetic susceptibility.