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配合物的形成进行量热测量，我们准备了用于滴定量热的新容器，用新容器（2 cmφ x 4 cmh）将初始测试溶液的体积减少到4 ml。是一对热敏电阻，可以检测 10^<-5> 度的温度变化。在本工作中，我们研究了软金属软配体 Ag^+-EPh_3 (E =乙腈中的 P, As, Sb) 体系，其 π 受体比二甲基亚砜 (DMSO) 更强，但 σ 供体更弱 [Ag(EPh_3)]^+ 的形成常数按 P > As > Sb 的顺序降低，并且AN 中形成单、双、三和四-PPh_3 配合物，结果与吡啶 (Py) 相比，更强。因此，软 Ag^+ 离子与 AN 和 Py 具有特定的 dπ-π 相互作用，但与 DMSO 没有。 [Ag(PPh_3)_4]^+ 存在于 AN 中，但未存在于 DMSO 和 DMSO 中。 Py. 单个 [Ag(PPh_3)_n]^+ (n = 0-3) 物质从 DMSO 到 AN 的转移焓表明该值接近于零n=0 并且随着 n 的增加，复合物变得更加正，表明特定的 dπ-π Ag^+-AN 相互作用被结合的 PPh_3 配体减弱，类似地，单个 [Ag(PPh_3)_n]^+ 的转移焓。从 DMSO 到 Py 的 (n = 0-3) 种物质表明，当 n=0 时，该值为负值且较大；随着 n 的增加，该复合物的负值变得较小，并且当 n=0 时，该值稍微为负值[Ag(PPh_3)_3]^+ 这表明特定的 dπ-π Ag^+-Py 相互作用几乎被结合的 PPh_3 配体所消除，这些事实导致了 dπ-π 相互作用减弱和 σ 贡献能力弱的结论。 AN 对于四面体 [Ag(PPh_3)_4]^+ 配合物的形成至关重要。