Synthesis and electrical resistivity of diiodotetrakis(isocyanide)rhodium(III) cation-7,7,8,8-tetracyano- p-quinodimethane (TCNQ) radical anion salts and x-ray crystal structure of diiodotetrakis(4-methylphenylisocyanide)rhodium(III) +TCN ⨪ Salt

Abstract

Four simple and two complex TCNQ ⨪ radical anion salts with diiodotetrakis(isocyanide)rhodium(III) cations were prepared; [Rh(RNC) 4I 2] +TCNQ ⨪ (R = 4-MeC 6H 4, 4-MeOC 6H 4, 2,6-Me 2C 6H 3, and 2,4,6-Me 3C 6H 2) and [Rh(RNC) 4I 2] +(TCNQ) 2 ⨪ (R = C 6H 5 and 4-MeC 6H 4). The complex salts exhibit relatively small electrical resistivities, 8.3 Ω cm for R = C 6H 5 and 30 Ω cm for R = 4-MeC 6H 4, while resistivities of the simple salts fall in the range 5.1 × 10 3–3.0 × 10 6 Ω cm as compacted samples at 25 °C. Electronic absorption spectra and magnetic susceptibilities indicate that the simple salts in the solid state involve the monomeric TCNQ ⨪ radical anion, except for [Rh(4-MeC 6H 4NC) 4I 2] +TCNQ ⨪ in which the TCNQ ⨪ radical anion exists in a column with a weak electronic interaction. A single-crystal X-ray analysis of [Rh(4-MeC 6H 4NC) 4I 2] +TCNQ ⨪ revealed the columnar structure of the TCNQ ⨪ radical anion with an equal interplanar spacing. The monoclinic crystal, space group C2/ c, has cell dimensions a = 7.4690(8), b = 24.759(2), c = 22.875(3) Å, β = 92.95(1)°, and Z = 4. Least-squares refinement, based on 3299 independent reflections with | F o|>; 3σ( F), produced as R factor of 0.054.