Synthesis of the Complex Catalysts Modeling a Reductive Elimination Reaction and Their Functions

1. [Pd_2(mu-Cl)_2（pi-烯丙基）_2]或[PtCl（烯丙基）_4与叔膦发生劈桥反应，再与石灰甲基化，可高产得所需的配合物[（pi-烯丙基）M(Me)(PR_3)] （M= Pd或Pt）。用IR、MS和NMR （^1H, ^<13>C）光谱对所得配合物进行了表征。配合物在固态和溶液中进行了热分解。气相色谱分析表明，钯络合物的主要有机产物是乙烷而不是1-丁烯。这一结果是由甲基桥接pi-烯丙基钯双核配合物的分子间还原消除造成的，该配合物是由膦配体解离形成的。另一方面，铂配合物的分解不产生乙烷，只产生丙烯和甲烷。考察了磷化氢和烯烃对热解组分的加性影响。在钯的情况下，磷化氢和马来酸酐的加入分别以50%和90%的相对比例导致1-丁烯的演化，而在铂的情况下，磷化氢的加和作用没有被识别，只有马来酸酐的加入才促进了偶联反应。在阳极峰电位（1.22 V vs. Ag/AgCl）下控制电位电解铂配合物，发现1-丁烯在摩尔比为50%时的演化。这种促进偶联的作用与在热裂解过程中加入pi-酸的作用相当，并提出了一个涉及阳离子中间体[（pi-烯丙基）Pt(Me)(PR_3)]^+的机制来解释这种作用。将二膦加入到pi-烯丙基铂配合物溶液中，分离出稳定的sigma-烯丙基配合物，但对配合物的分解表明其未发生偶联反应；只有丙烯和甲烷进化而来。

1. Bridge-splitting reactions of [Pd_2(mu-Cl)_2(pi-allyl)_2] or [PtCl(allyl)]_4 with tertiary phosphines, followed by methylations with LiMe afforded the desired complexes [(pi-allyl)M(Me)(PR_3)] (M= Pd or Pt) in high yields.2. The complexes thus obtained were characterized by IR, MS, and NMR (^1H, ^<13>C) spectroscopy.3. Thermolysis of the complexes was carried out in the solid state and in solution. Gas-chromatographic analysis of the evolved gases was revealed that in palladium complexes the major organic product is ethane rather than 1-butene. This result was accounted for by the intermolecular reductive-elimination of ethane from the methyl-bridged pi-allylpalladium dinuclear complex, formed by dissociation of the phosphine ligand. On the other hand, the platinum complexes decompose with no evolution of ethane and with the evolution of propene and methand, exclusively.4. Additive effects of phosphine and alkene on the thermolysis components were also examined. In the palladium case, the addition of phosphine and maleic anhydride resulted in the evolution of 1-butene in a 50% and a 90% relative ratios, respectively, while in the platinum case the additive effect of phosphine was not recognized and the coupling reaction was promoted only in the addition of maleic anhydride.5. The controlled-potential electrolysis of the platinum complex at the anodic peak potential (1.22 V vs. Ag/AgCl) revealed the evolution of 1-butene in a 50% molar ratio. This coupling-promoting effect is comparable to that of the addition of pi-acid in the thermolysis, and a mechanism involving the cationic intermediate [(pi-allyl)Pt(Me)(PR_3)]^+ was proposed to explain the effect.6. On the addition of diphosphines in the solutions of pi-allylplatinum complexes, stable sigma-allyl complexes were isolated, but theimolysis of their complexes revealed that no coupling reaction occurs on it; only propene and methane evolved.