Synthesis, spectroscopic properties and electrochemistry of Rh2(ap)4(R) where R = CH3 or C6H5 and ap = 2-anilinopyridinate anion

Two sigma-bonded Rh25+ complexes, Rh2(ap)4(C6H5) and Rh2(ap)4(CH3), where ap = 2-anilinopyridinate anion were synthesized and examined as to their electrochemical and spectroscopic properties in nonaqueous media. Rh2(ap)4(C6H5) was also structurally characterized. The presence of the phenyl axial ligand on Rh2(ap)4(C6H5) does not bring about a significant structural effect on the ap framework as compared to Rh2(ap)4Cl or Rh2(ap)4(CCH) but the Rh–Rh and Rh–Caxial bond lengths are both elongated due to the strong electron-donating effect of the phenyl group. The two sigma-bonded dirhodium compounds each undergo a single reversible one-electron reduction to in situ   generate a stable Rh24+ complex and two reversible one-electron oxidations to give stable compounds in Rh26+ and Rh27+ oxidation states. These redox reactions occur at E1/2 = −0.79, 0.28 and 0.93 V for R = CH3 and −0.71, 0.35 and 0.95 V for R = C6H5. The ESR spectrum of Rh2(ap)4(CH3) has g⊥ and g|| values of 2.17 and 1.89 while Rh2(ap)4(C6H5) has an ESR spectrum with signals at 2.17 (g⊥) and 2.00 (g||), consistent with the odd electron in each dimetal unit being localized on only one of the two metal centers in Rh25+.

Two sigma-bonded Rh25+ complexes, Rh2(ap)4(C6H5) and Rh2(ap)4(CH3), where ap = 2-anilinopyridinate anion were synthesized and examined as to their electrochemical and spectroscopic properties in nonaqueous media.Figure optionsDownload as PowerPoint slide