To overcome the separation difficulty of the palladium-based homogeneous catalyst, the palladium complex can be anchored on various supports such as silica, polymers and nanoparticles. For the same purpose, we describe a general and facile method to immobilize palladium bis(phosphine) complexes on the basis of the technique widely used for metal–organic framework (MOF) synthesis, yielding a mesoporous coordination polymer palladium-CP1. Although palladium complexes are generally not stable enough to allow further manipulation, we succeeded in preparation of a palladium coordination polymer without by-product Pd clusters or nanoparticles. The fresh palladium-CP1 catalyst exhibits a yield close to 55% for tolane at room temperature and 24 h in Sonogashira coupling of iodobenzene and phenylacetylene, as compared with a yield of 89% for its homogeneous counterpart [Pd(PPh3)2Cl2]. Furthermore, this catalyst is stable enough to be reused more than four times with no Pd and Zn leaching. Therefore this new immobilization method offers great promise for the produce of recyclable palladium heterogeneous catalysts with higher activity and higher thermal and chemical stability in the future.
为克服
钯基均相催化剂的分离困难,可将
钯络合物固定在各种载体上,如
二氧化硅、聚合物和纳米粒子。出于同样的目的,我们描述了一种基于
金属-有机框架(MOF)合成技术的一般且简便的方法,用于将
钯双(膦)络合物固定在载体上,从而产生一种介孔配位聚合物
钯-CP1。尽管
钯络合物通常不够稳定,无法进行进一步操作,但我们成功制备了一种
钯配位聚合物,没有副产物Pd簇或纳米粒子。新鲜
钯-CP1催化剂在室温下对
甲苯的转化率接近55%,在24小时内对
碘苯和
苯乙炔进行Sonogashira偶联,而其均相对应物[Pd(PPh3)2Cl2]的转化率为89%。此外,这种催化剂足够稳定,可以重复使用四次以上,且不会析出
钯和
锌。因此,这种新的固定化方法为生产可回收的
钯非均相催化剂提供了巨大的前景,这些催化剂在未来具有更高的活性、更高的热稳定性和
化学稳定性。