问题：关于四三苯基磷钯的催化活性的疑问
类型：求助 (悬赏分:3分)
提问：wangguiyin
等级：▲
版块：有机化学问题(jimuwei,fpcwin1211,netpanda,yjgzfl,Ftian,)
信誉：70%
回复：6
阅读：761
时间：2009-09-02 13:56:37 编辑加入/取消收藏订制/取消短消息举报该贴

我现在正做一个反应，最后一步是用四三苯基磷钯做催化剂将酯基还原成羟基，我对反应中做了微小的调整。但现在出现一个现象，我的催化还原反应进行得不彻底。我想请教大家四三苯基磷钯的什么条件下催化活性最高。

回复人：wangguiyin,▲ () 时间：2009-09-04 14:14:16 编辑	1楼
claymore, 你能告诉我它的应用范围吗？

回复人：claymore,★★★★★ (C-H活化，kumada,suzuki,stille,negishi.cross-coupling.) 时间：2009-09-02 18:42:50 编辑

2楼

Tetrakis(Triphenylphosphine)Palladium(0)Submitted By D. R. Coulson
Checked By L. C. Satek And S. O. Grim
(Inorg. Synth. #21)HTML by Rhodium

2 PdCl2 + 8 PPh3 + 5 NH2NH2·H2O → 2 Pd(PPh3)4 + 4 NH2NH2·HCl + N2 + 5 H2O
Preparations of phosphine and phosphite complexes of palladium(0) have been reported to result from reduction of palladium(II) complexes in the presence of the desired ligand1-5. The products are generally formulated as PdL4-n (where n = 0, 1), depending on the nature and amount of the ligand used. A related complex, [Pd(PPh3)2]n has also been reported6.
Although this preparation is similar in concept to these previous ones, advantage is gained in being able to obtain a high yield of Pd(PPh3)4 in one step from palladium dichloride.
Procedure
A mixture of palladium dichloride (17.72 g, 0.10 mol), triphenylphosphine (131 g, 0.50 mol), and 1200 mL of dimethyl sulfoxide is placed in a single-necked, 2-L, round-bottomed flask equipped with a magnetic stirring bar and a dual-outlet adapter. A rubber septum and a vacuum nitrogen system are connected to the outlets. The system is then placed under nitrogen with provision made for pressure relief through a mercury bubbler. The yellow mixture is heated by means of an oil bath with stirring until complete solution occurs (~140°C). The bath is then taken away, and the solution is rapidly stirred for approximately 15 min. Hydrazine hydrate (20 g, 0.40 mol) is then rapidly added over approximately I min from a hypodermic syringe. A vigorous reaction takes place with evolution of nitrogen. The dark solution is then immediately cooled with a water bath; crystallization begins to occur at ~125°C. At this point the mixture is allowed to cool without external cooling. After the mixture has reached room temperature it is filtered under nitrogen on a coarse, sintered-glass funnel. The solid is washed successively with two 50-mL portions of ethanol and two 50-mL portions of diethyl ether. The product is dried by passing a slow stream of nitrogen through the funnel overnight. The resulting yellow crystalline product weighs 103.5-108.5 g (90-94% yield)Note 1.
A melting point determinationNote 2 on a sample in a sealed capillary tube under nitrogen gave a decomposition point of 116°C (uncorrected). This compares with a similar determination (115°C) performed on the product prepared by the method of Malatesta and Angoletta1.
Properties
The Pd(PPh3)4 complex obtained by this procedure is a yellow, crystalline material possessing moderate solubilities in benzene (50 g L-1), dichloromethane, and chloroform. The compound is less soluble in acetone, tetrahydrofuran and acetonitrile. Saturated hydrocarbon solvents give no evidence of solution. Although the complex may be handled in air, it is best stored under nitrogen to ensure its purity.
In benzene, molecular-weight measurements suggest substantial dissociation1,4:
Pd(PPh3)4 Pd(PPh3)4-n + n PPh3
Solutions of the complex in benzene rapidly absorb molecular oxygen giving an insoluble, green oxygen complex, Pd(PPh3)2O27. This oxygen complex has been implicated as an intermediate in a catalytic oxidation of phosphines2,8.
Related displacements with acetylenes9 and electrophilic olefins6 have been reported to give complexes formulated as [Pd(PPh3)2 (olefin or acetylene)]. Also, oxidative additions of alkyl and aryl halides have been shown to occur giving palladium(II) complexes, Pd(PPh3)2(R)Cl10. As a catalyst, the complex has been shown capable of dimerizing butadiene to give 1,3,7-octatriene11.
Notes

The checkers worked on one-third of the stated scale, obtaining a yield of 37.4 g (97%).
The checkers report that decomposition temperature does not appear to be a good criterion of identity or purity since it is not very reproducible.

[该帖子已被claymore在2009-09-04 15:48:25编辑过]

回复人：claymore,★★★★★ (C-H活化，kumada,suzuki,stille,negishi.cross-coupling.) 时间：2009-09-04 22:17:40 编辑	3楼

回复人：hongtou,▲ () 时间：2009-09-04 22:28:31 编辑	4楼
学习了，谢谢

回复人：wangguiyin,▲ () 时间：2009-09-05 14:56:04 编辑	5楼
claymore, 谢谢你，但你没有理解我的意思，我想要的是在什么条件下它的催化活性最高。既它要求的反应体系的酸碱对它的活性有影响吗？ [该帖子已被wangguiyin在2009-09-05 15:02:48编辑过]

回复人：wangguiyin,▲ () 时间：2009-09-07 09:29:29 编辑	6楼
已经打分了！

得分人：claymore :3,

问题讨论没有结束...

您尚未进入本论坛,登录之后才可以回贴

6msec