与卟啉金属化机制相关的铜（II）离子与5,10,15,20-四苯基卟啉的顶位配合物的形成与去质子化动力学。通过EXAFS光谱确定的乙腈中铜（II）-吡啶配合物的结构。

Formation and Deprotonation Kinetics of the Sitting-Atop Complex of Copper(II) Ion with 5,10,15,20-Tetraphenylporphyrin Relevant to the Porphyrin Metalation Mechanism. Structure of Copper(II)-Pyridine Complexes in Acetonitrile As Determined by EXAFS Spectroscopy.

作者信息

Inada Yasuhiro, Sugimoto Yumi, Nakano Yuko, Itoh Yuki, Funahashi Shigenobu

机构信息

Laboratory of Analytical Chemistry, Faculty of Science, Nagoya University, Nagoya 464-8602, Japan.

出版信息

Inorg Chem. 1998 Oct 19;37(21):5519-5526. doi: 10.1021/ic980420d.

DOI:10.1021/ic980420d

PMID:11670696

Abstract

The formation of a sitting-atop (SAT) complex of Cu(II) ion with 5,10,15,20-tetraphenylporphyrin (H(2)tpp) in acetonitrile has been observed, and the kinetic parameters for the formation were determined as follows: k(S0) = (3.6 +/- 0.1) x 10(5) mol(-)(1) dm(3) s(-)(1) at 25.0 degrees C, DeltaH(S0)() = 56 +/- 5 kJ mol(-)(1), and DeltaS(S0)() = 46 +/- 19 J mol(-)(1) K(-)(1). The (1)H NMR spectrum of the SAT complex (Cu(H(2)tpp)(2+)) indicated that two pyrrolenine nitrogens coordinate to the Cu(II) ion and that two protons bound to the pyrrole nitrogens remain. The protons were abstracted by the addition of pyridine (py) as the Brønsted base to give the Cu(tpp) metalloporphyrin. In the presence of py, the product for the reaction of the Cu(II) ion with H(2)tpp was Cu(tpp) instead of the SAT complex. The observed conditional rates for the formation of Cu(H(2)tpp)(2+) and Cu(tpp) were interpreted by the contribution of Cu(2+), Cu(py)(2+), and Cu(py)(2)(2+) species, and the second-order rate constants of the SAT complex formation were k(S1) = (3.5 +/- 0.3) x 10(4) mol(-)(1) dm(3) s(-)(1) for Cu(py)(2+) and k(S2) = 90 +/- 2 mol(-)(1) dm(3) s(-)(1) for Cu(py)(2)(2+). Deprotonation rates were measured by following the reaction between the SAT complex and py as a function of the py concentration, and the second-order rate constant was determined to be (2.3 +/- 0.1) x 10(2) mol(-)(1) dm(3) s(-)(1). The present kinetic results have indicated that the SAT complex exists during the course of the metalation process and that the SAT complex formation is a rate-determining step.

摘要

已观察到在乙腈中铜（II）离子与5,10,15,20-四苯基卟啉（H₂tpp）形成了一种坐顶（SAT）配合物，并且测定了该形成过程的动力学参数如下：在25.0℃时，k(S0) = (3.6 ± 0.1) × 10⁵ mol⁻¹ dm³ s⁻¹，ΔH(S0)⁰ = 56 ± 5 kJ mol⁻¹，以及ΔS(S0)⁰ = 46 ± 19 J mol⁻¹ K⁻¹。SAT配合物（Cu(H₂tpp)²⁺）的¹H NMR谱表明两个吡咯啉氮原子与铜（II）离子配位，并且与吡咯氮原子相连的两个质子保留。通过加入作为布朗斯特碱的吡啶（py）来夺取质子，从而得到Cu(tpp)金属卟啉。在py存在下，铜（II）离子与H₂tpp反应的产物是Cu(tpp)而非SAT配合物。通过Cu²⁺、Cu(py)²⁺和Cu(py)₂²⁺物种的贡献来解释观察到的Cu(H₂tpp)²⁺和Cu(tpp)形成的条件速率，SAT配合物形成的二级速率常数对于Cu(py)²⁺为k(S1) = (3.5 ± 0.3) × 10⁴ mol⁻¹ dm³ s⁻¹，对于Cu(py)₂²⁺为k(S2) = 90 ± 2 mol⁻¹ dm³ s⁻¹。通过跟踪SAT配合物与py之间的反应随py浓度的变化来测量去质子化速率，并且确定二级速率常数为(2.3 ± 0.1) × 10² mol⁻¹ dm³ s⁻¹。目前的动力学结果表明SAT配合物在金属化过程中存在，并且SAT配合物的形成是一个速率决定步骤。