An Interpretation of Gated Behavior: Kinetic Studies of the Oxidation and Reduction Reactions of Bis(2,9-dimethyl-1,10-phenanthroline)copper(I/II) in Acetonitrile
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- 作者：Nobuyoshi Koshino ; Yoshio Kuchiyama ; Hiroshi Ozaki ; Shigenobu Funahashi ; and Hideo D. Takagi
- 刊名：Inorganic Chemistry
- 出版年：1999
- 出版时间：July 12, 1999
- 年：1999
- 卷：38
- 期：14
- 页码：3352 - 3360
- 全文大小：149K
- 年卷期：v.38,no.14(July 12, 1999)
- ISSN：1520-510X
文摘
Reduction reactions of Cu(dmp)22+ (dmp = 2,9-dimethyl-1,10-phenanthroline) by ferrocene (Fe(Cp)2 = bis(cyclopentadienyl)iron(II)), decamethylferrocene (Fe(PMCp)2 = bis(pentamethylcyclopentadienyl)iron(II)), andCo(bpy)32+ (bpy = 2,2'-bipyridine) and oxidation reactions of Cu(dmp)2+ by Ni(tacn)23+ (tacn = 1,4,7-triazacyclononane) and Mn(bpyO2)33+ (bpyO2 = N,N'-dioxo-2,2'-bipyridine) were studied in acetonitrile for thepurpose of interpreting the gated behavior involving copper(II) and -(I) species. It was shown that the electronself-exchange rate constants estimated for the Cu(dmp)22+/+ couple from the oxidation reaction of Cu(dmp)2+ byNi(tacn)23+ (5.9 × 102 kg mol-1 s-1) and Mn(bpyO2)33+ (2.9 × 104 kg mol-1 s-1) were consistent with thedirectly measured value by NMR (5 × 103 kg mol-1 s-1). In contrast, we obtained the electron self-exchange rateconstant of Cu(dmp)22+/+ as 1.6 kg mol-1 s-1 from the reduction of Cu(dmp)22+ by Co(bpy)32+. The pseudo-first-order rate constant for the reduction reaction of Cu(dmp)22+ by Fe(Cp)2 was not linear against the concentrationof excess amounts of Fe(Cp)2. A detailed analysis of the reaction revealed that the reduction of Cu(dmp)22+involved the slow path related to the deformation of Cu(dmp)22+ (path B in Scheme 1). By using Fe(PMCp)2 (theE
value is 500 mV more negative than that of Fe(Cp)2+/0) as the reductant, the mixing with another pathwayinvolving deformation of Cu(dmp)2+ (path A in Scheme 1) became more evident. The origin of the "GatedBehavior" is discussed by means of the energy differences between the "normal" and deformed Cu(II) and Cu(I)species: the difference in the crystal field activation energies corresponding to the formation of pseudo-tetrahedralCu(II) from tetragonally distorted Cu(II) and the difference in the stabilization energies of the tetrahedral andtetragonal Cu(I) for the activation of Cu(I) species. The reduction reaction of Cu(dmp)22+ by Fe(PMCp)2 confirmedthat the mixing of the two pathways takes place by lowering the energy level corresponding to the less favorableconformational change of Cu(I) species.
value is 500 mV more negative than that of Fe(Cp)2+/0) as the reductant, the mixing with another pathwayinvolving deformation of Cu(dmp)2+ (path A in Scheme 1) became more evident. The origin of the "GatedBehavior" is discussed by means of the energy differences between the "normal" and deformed Cu(II) and Cu(I)species: the difference in the crystal field activation energies corresponding to the formation of pseudo-tetrahedralCu(II) from tetragonally distorted Cu(II) and the difference in the stabilization energies of the tetrahedral andtetragonal Cu(I) for the activation of Cu(I) species. The reduction reaction of Cu(dmp)22+ by Fe(PMCp)2 confirmedthat the mixing of the two pathways takes place by lowering the energy level corresponding to the less favorableconformational change of Cu(I) species.