Predominant 1,2-Insertion of Styrene in the Pd-Catalyzed Alternating Copolymerization with Carbon Monoxide
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- 作者：Kyoko Nozaki ; Hatsumi Komaki ; Yasutoyo Kawashima ; Tamejiro Hiyama ; and Toshiaki Matsubara
- 刊名：Journal of the American Chemical Society
- 出版年：2001
- 出版时间：January 31, 2001
- 年：2001
- 卷：123
- 期：4
- 页码：534 - 544
- 全文大小：219K
- 年卷期：v.123,no.4(January 31, 2001)
- ISSN：1520-5126
文摘
The regioselectivity of styrene insertion to an acyl-Pd bond was studied by NMR in (i) a stoichiomericreaction and (ii) a copolymerization with CO. In the stoichiometric reaction of styrene with [(CH3CO)Pd(CH3CN){(R,S)-BINAPHOS}]·[B{3,5-(CF3)2C6H3}4], both 1,2- and 2,1-products were given. To mimic thereal polymerization conditions, a polyketone-substituted complex [{CH3(CH2CHCH3CO)n}Pd{(R,S)-BINAPHOS}]·[B(3,5-(CF3)2C6H3)4] (n 
14) was prepared. When this polymer-attached Pd species was treatedwith styrene, the 1,2-insertion product was the only detectable species. Thus, exclusive 1,2-insertion isdemonstrated to be responsible for the styrene-CO copolymerization, in sharp contrast to the predominant2,1-insertion with conventional nitrogen ligands. Chain-end analysis revealed that 
-hydride elimination tookplace from the 2,1-complex but not from the 1,2-complex. Thus, once 2,1-insertion occurs, rapid -hydrideelimination proceeds to terminate the polymerization, as is common to the other phosphorus-ligand systems.The resulting Pd-H species re-initiates the copolymerization, as was proven by MALDI-TOF mass analysisof the product copolymers.
14) was prepared. When this polymer-attached Pd species was treatedwith styrene, the 1,2-insertion product was the only detectable species. Thus, exclusive 1,2-insertion isdemonstrated to be responsible for the styrene-CO copolymerization, in sharp contrast to the predominant2,1-insertion with conventional nitrogen ligands. Chain-end analysis revealed that -hydride elimination tookplace from the 2,1-complex but not from the 1,2-complex. Thus, once 2,1-insertion occurs, rapid -hydrideelimination proceeds to terminate the polymerization, as is common to the other phosphorus-ligand systems.The resulting Pd-H species re-initiates the copolymerization, as was proven by MALDI-TOF mass analysisof the product copolymers.