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Titration Calorimetry System for Measurement of Formation Enthalpies of Organometal Complexes

用于测量有机金属配合物形成焓的滴定量热系统

基本信息

批准号：
12554025
负责人：
ISHIGURO Shin-ichi
金额：
$ 8.45万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

With the aim of calorimetric measurement for the formation of organo-transition metal complexes, we prepared a new vessel for titration calorimetry. The volume of initial test solution is reduced to 4 ml with a new vessel (2 cmφ x 4 cmh). Heat sensor is a couple of thermistors, which can detect temperature changes by 10^<-5> degree. In the present work, we studied complexation of soft-metal soft-ligand Ag^+-EPh_3 (E = P, As, Sb) systems in acetonitrile, which is a stronger π acceptor but weaker σ donor than dimethyl sulfoxide (DMSO). The formation constant of [Ag(EPh_3)]^+ reduced in the order P > As > Sb, and the mono-, bis-, tris- and tetrakis-PPh_3 complexes are formed in AN. The result is compared with that in pyridine (Py), which is a stronger π acceptor and σ donor than DMSO. The soft Ag^+ ion thus shows a specific dπ-π interaction with AN and Py but not with DMSO. The [Ag(PPh_3)_4]^+ is found in AN but not in DMSO and Py. Enthalpies of transfer of individual [Ag(PPh_3)_n]^+ (n = 0-3) species from DMSO to AN show that the value is close to zero for n=0 and become more positive for the complex with increasing n, indicating that the specific dπ-π Ag^+-AN interaction is weakened by bound PPh_3 ligand. Similarly, enthalpies of transfer of individual [Ag(PPh_3)_n]^+ (n = 0-3) species from DMSO to Py show that the value is negative and large for n=0 and become less negative for the complex with increasing n, and the value is slightly negative for [Ag(PPh_3)_3]^+. This indicates that the specific dπ-π Ag^+-Py interaction is almost disappeared by bound PPh_3 ligand. These facts leads to the conclusion that weakened dπ-π interaction and weak σ donating ability of AN is essential for the formation of tetrahedral [Ag(PPh_3)_4]^+ complex.

为了对有机过渡金属络合物的生成进行量热测量，我们研制了一种新的滴定量热计容器。用新的血管(2 cmφx 4cmh)将初始试液的体积减少到4ml。热敏传感器是一对热敏电阻，可以探测到10度-5度的温度变化。在本工作中，我们研究了软金属软配体Ag2+-Eph3(E=P，As，Sb)体系在乙腈中的络合作用。乙腈是一种比二甲基亚砜更强的π受体，但更弱的σ供体。[Ag(Eph3)]~+的形成常数按P&gt；As&gt；Sb的顺序减小，在AN中形成了单、双、三和四元的PPh_3络合物。与吡啶(Py)相比，吡啶(Py)是一种更强的π受体和σ供体。因此，软的Ag~+离子与An和Py表现出特定的d-π-π相互作用，但与二甲基亚砜没有。[Ag(PPh_3)_4]~+在An中存在，而在DMSO和Py中没有。[Ag(PPh_3)_n]~+(n=0~3)物种从二甲基亚砜向AN的转移热表明，当n=0时，[Ag(PPh_3)_n]~+向An的转移热值接近于零，而随着n的增加，络合物的转移反应变得更正，表明PPh_3配基的结合减弱了d-π-π与Ag~(++)的相互作用。同样地，[Ag(PPh_3)_n]~+(n=0~3)物种从DMSO到Py的转移热值表明，当n=0时，[Ag(PPh_3)_n]~+为负值，随着n的增加，负值变小，而对于[Ag(PPh_3)_3]~+则略为负值。这表明，结合的PPh_3配体几乎消除了d-π-π与Ag~(++)-Py的相互作用。这些事实表明，弱的dπ-π相互作用和弱的σ供体能力是形成四面体[Ag(PPh_3)_4]^+络合物的必要条件。