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Sydnone Complexes of Pentacyanoferrate(II)
Author(s) -
Shi ChengHsiang,
Wang ShiaoTsun,
Yang ShiaoYun,
Yeh Andrew,
Tien HsienJu
Publication year - 1998
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.199800013
Subject(s) - chemistry , sydnone , mesoionic , ligand (biochemistry) , moiety , medicinal chemistry , ring (chemistry) , electrochemistry , aqueous solution , kinetics , pyridine , stereochemistry , inorganic chemistry , electrode , organic chemistry , biochemistry , physics , receptor , quantum mechanics
The 3‐methylsydnone (CH 3 Sd) and 3‐phenylsydnone (PhSd) complexes of pentacyanoferrate(II) were prepared in aqueous solution by the reaction of Fe(CN) 5 OH 2 3− with excess ligand. Metal to ligand charge transfer transitions were observed for both complexes at 442 nm (CH3Sd) and 494 nm (PhSd), respectively. The reduction potentials were measured with the E f values of 0.65 and 0.67 V (vs. NHE) for CH 3 Sd and PhSd, respectively, at 25 °C, μ = 0.10 M LiClO 4 and pH = 5. The kinetics of the substitution reaction were also investigated, and k f and k d values (25 °C, μ = 0.10 M LiClO 4 ,pH = 5) are (5.4 ± 0.2) × 10 −2 M −1 s −1 and (1.4 + 0.1) × 10 −5 s −1 (CH3Sd), (8.8 ±0.1) × 10 −2 M −1 s −1 and (4.7 ±0.1) × 10 −5 s −1 (PhSd). The k f values for both sydnone complexes are approximately four orders of magnitude smaller than other pentacyanoferrate(II) complexes with neutral ligands. The difference may arise from the mesoionic character of the sydnone compounds rather than via a different reaction mechanism. Spectroscopic, kinetic and electrochemical results all suggest that the sydnone ring shows a better π‐backbonding stabilization with Fe(CN) 5 3− moiety than that of the pyridine ring.