Preparation of Stable Triplet Carbenes and Its Application to Stable High-Spin Molecules

稳定三重态卡宾的制备及其在稳定高自旋分子中的应用

基本信息

批准号：
09304059
负责人：
TOMIOKA Hideo
金额：
$ 18.18万
依托单位：
MIE UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

This research was undertaken to stabilize and isolate a triplet carbene and to use it as a spin unit for stablehigh-spin organic molecules.Steric protection is an ideal method of stabilizing the triplet carbene since a protecting group when introduced near carbene center not only blocks the carbene center from external reagents but also results in thermodynamic stabilization by increasing the central bond angle. However, clue to a voracious appetite of carbenes for electrons, this strategy encounters limitation when alkyl groups are employed as protecting group. In this light, it is crucial to develop a new protecting group which is sterically congesting but unreactive toward triplet carbenes. We found the oretically bulky yet poor H donating alkyl groups such as bicyclo[2.2.2]octyl and triptycyl groups and heteroatomsubstituents such as bromine and trifluoromethyl groups are effective kinetic protectors toward triplet carbenes and were able to generate triplet diphenylcarbene surviving more than one hour in solution at room temperature.We also found serendiptously that the precursor diazomethanes for those stable triplet carbenes are also fairly stable and can be used as a building block for preparing poly(diazo) compounds. For instance, we were able to introduce ethynyl group at the para position of sterically congested diphenyldiazomethanes and to prepare tris- and hexakis(diazo)-methanes by subsequent coupling reaction using l, 3,6-tri(iodo)benzene. Polycarbenes generated from those poly(diazo) compounds were shown to have high spin states.

这项研究的目的是稳定和分离三重态卡宾，并将其用作稳定的高自旋有机分子的自旋单元。空间保护是稳定三重态卡宾的理想方法，因为在卡宾中心附近引入保护基团时，不仅会阻止外部试剂的卡宾中心，但也通过增加中心键角导致热力学稳定。然而，由于卡宾对电子的贪婪需求，当使用烷基作为保护基团时，该策略遇到了限制。有鉴于此，开发一种空间拥挤但对三重态卡宾不发生反应的新保护基团至关重要。我们发现，体积大但供氢能力差的烷基（例如双环[2.2.2]辛基和三蝶基）和杂原子取代基（例如溴和三氟甲基）是三线态卡宾的有效动力学保护剂，并且能够生成存活时间超过一小时的三线态二苯基卡宾我们还偶然发现，那些稳定的三重态卡宾的前体重氮甲烷也相当稳定，可以用作制备聚（重氮）化合物的结构单元。例如，我们能够在空间拥挤的二苯基重氮甲烷的对位引入乙炔基，并通过随后使用1,3,6-三(碘)苯的偶联反应制备三-和六(重氮)-甲烷。由这些聚（重氮）化合物生成的聚卡宾具有高自旋态。