Andrew Yeh

The 3-(3′-pyridyl)sydnone complex of pentacyanoferrate(II)

Abstract The 3-(3′-pyridyl)sydnone (3-PySd) complex of pentacyanoferrate(II) was prepared and characterized both in aqueous solution and in the isolated state. A comparison of 1 H NMR results between the free and the coordinated ligand indicates that the metal center is coordinated to the ligand through the pyridine nitrogen atom. A metal to ligand charge transfer band was observed at λ max =410 nm and ϵ max =3.20×10 3 M −1 cm −1 . The rate constants of formation and dissociation of the complex were measured; the k f and k d values at μ=0.10 M(LiClO 4 ), pH=5 and T =25 °C are 5.62×10 2 M −1 s −1 and 3.23×10 −3 s −1 , respectively. A cyclic voltammetric study of the complex has shown that the Fe II Fe III oxidation is a reversible one-electron process with E 1 2 =0.54 V versus NHE. The strong electron withdrawing power of the sydnone is demonstrated by both the spectral and the electrochemical properties of the title complex in comparison with those of the pyridine and 3-substituted pyridine complexes. This result is consistent with the assignment of the sydnones to the family of non-benzenoid aromatic compounds.