Reduction Reaction of the Copper(II) Complex Bearing 1,3-Di(pyridine-2-carboxaldimino)propane (pitn) by Decamethylferrocene in Acetonitrile

• Published in: Journal of solution chemistry Vol. 43; no. 9-10; pp. 1479 - 1486
• Main Authors: Yamada, Atsutoshi, Watanabe, Yuki, Moda, Kyoko, Itoh, Sumitaka, Ishihara, Koji, Inamo, Masahiko, Hassan, Refat Moustafa, Takagi, Hideo D
• Format: Journal Article
• Language: English
• Published: 01.10.2014
• Subjects: Acetonitrile; BEARINGS; COPPER COMPOUNDS; Crystals; DIHEDRAL ANGLE; Electron transfer; Ion pairs; MATHEMATICAL ANALYSIS; PROPANE; Rate constants; Reduction; Saturation
• ISSN: 0095-9782; 1572-8927
• DOI: 10.1007/s10953-014-0248-2

The reduction reaction of the Cu(II)-pitn complex (pitn = 1,3-di(pyridine-2-carboxaldimino)propane) by decamethylferrocene [Fe(Cp*)2] was examined in acetonitrile. The observed pseudo-first-order rate constants exhibited saturation kinetics with increasing excess amount of [Fe(Cp*)2]. Detailed analyses revealed that the reaction is controlled by a structural change prior to the electron transfer step, rather than a conventional bimolecular electron transfer process preceded by ion pair (encounter complex) formation. The rate constant for the structural change was estimated to be 275 + or - 13 s-1 at 298 K ( Delta H* = 33.3 + or - 1.0 kJ times mol-1, Delta S* = 86 + or - 5 J times mol-1 times K-1), which is the fastest among gated reactions involving CuN4 complexes. It was confirmed by EPR measurement and Conflex calculations that the dihedral angle between the two N-N planes is significantly large (40[degrees]) in solution whereas it is merely 17.14[degrees] in the crystal.