4,5-Dicarboxytriazole (H3Dcbt) has been found to be a dinucleating ligand with behavior similar to that of other dicarboxyazolates previously reported. A new family of anionic complexes of this ligand with Rh(I) and Ir(I) using cyclooctadiene, CO, and PPh3 as ancillary ligands have been prepared. The salt [NBu4][Rh2(Dcbt)(CO)4]·0.4CH2-Cl2 crystallizes in the monoclinic space group P21/c with a = 14.210(4) Å, b = 16.161(4) Å, c = 15.296(4) Å, and β = 114.42(2)° and with four anions and four cations per unit cell. The final R value was 0.036. The planar anions [Rh2(Dcbt)(CO)4]− form dimers separated by cations. The short distance between the rhodium atoms in the dimer is associated with metal-metal interactions. The product [NBu4][Rh2(Dcbt)(CO)2(PPh3)2] crystallizes in the triclinic space group P1̅ with a = 17.714(8) Å, b = 12.969(8) Å, c = 13.406(8) Å, α = 108.15(4)°, β = 101.38(4)°, and γ = 95.95(4)° and with two anions and two cations per unit cell. The final R value was 0.053. The triphenylphosphine is situated trans to N due to the larger trans effect of the ring N atom. The electrochemical oxidation of [NR4][Ir2(Dcbt)(CO)4] (R = Pr, Bu) yielded the partially oxidized conductive materials [NR4]0.5[Ir2(Dcbt)(CO)4]. The stoichiometry based on elemental analyses was corroborated by X-ray photoelectron spectroscopy (XPS). This technique showed also that the oxidation is metal centered. An EXAFS study indicated that the coordination sphere of the iridium is preserved upon oxidation. The pressed pellet conductivities of these partially oxidized salts are in the range 10−4–10−5 Ω−1 cm−1. © 1993, American Chemical Society. All rights reserved.
|Publication status||Published - 1 Jan 1993|