Hydrosilylation of alkenes and ketones catalyzed by nickel(II) indenyl complexes
Hydrosilylation of alkenes and ketones catalyzed by nickel(II) indenyl complexes
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DOI：
10.1139/v03-133
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发表时间：
2003-11-01
影响因子：
1.1
通讯作者：
Zargarian, D
中科院分区：
文献类型：
--
作者：
Fontaine, FG;Nguyen, RV;Zargarian, D
从配合物 (茚基)Ni(PPh3)Cl 中提取 Cl- 会产生阳离子物质，这些阳离子物质是某些烯烃和酮氢化硅烷化的有效预催化剂。例如，(1-Me-茚基)Ni(PPh3)Cl和NaBPh4（或甲基铝氧烷）的混合物在室温下与约反应。 100当量PhSiH3 和苯乙烯分别生成[1-苯基-1-乙基](苯基)硅烷PhCH(CH3)(SiPhH2)，产率50%-80%。同一系统还可以催化 1-己烯和降冰片烯的氢化硅烷化，但这些底物产生的产物由区域异构体和立体异构体的混合物组成。另一方面，酮氢化硅烷化是区域专一性的，能够以高产率产生相应的甲硅烷基醚。大量实验观察表明，最初产生的镍基阳离子不是催化活性物质。事实上，阳离子引发剂可以被LiAlH4或AlMe3取代，它们分别生成相应的Ni-H或Ni-Me衍生物。此外，观察到的将 PhSiH3 添加到苯乙烯上的区域选择性（即，主要将甲硅烷基片段添加到 α-C 上）与反应机制涉及碳阳离子中间体时所预期的相反。提出了一种新机制，其中活性物质是 Ni-H 物质，源自 H- 从 PhSiH3 转移到最初生成的 Ni 阳离子。
Abstraction of Cl- from the complexes (indenyl)Ni(PPh3)Cl generates cationic species that are effective precatalysts for the hydrosilylation of some olefins and ketones. For instance, the mixture of (1-Me-indenyl)Ni(PPh3)Cl and NaBPh4 (or methylaluminoxane) reacts at room temperature with ca. 100 equiv. each of PhSiH3 and styrene to produce [1-phenyl-1-ethyl](phenyl)silane, PhCH(CH3)(SiPhH2), in 50%-80% yield. The same system can also catalyze the hydrosilylation of 1-hexene and norbornene, but the products arising from these substrates consist of mixtures of regio- and stereoisomers. On the other hand, ketone hydrosilylation is regiospecific, giving the corresponding silyl ethers in high yields. A number of experimental observations have indicated that the initially generated Ni-based cation is not the catalytically active species. Indeed, the cationic initiators may be replaced by LiAlH4 or AlMe3, which generate the corresponding Ni-H or Ni-Me derivatives, respectively. Moreover, the observed regioselectivity for the addition of PhSiH3 to styrene (i.e., predominant addition of the silyl fragment to the alpha-C) is opposite of what would be expected if the reaction mechanism involved carbocationic intermediates. A new mechanism is proposed in which the active species is a Ni-H species originating from the transfer of H- from PhSiH3 to the initially generated Ni cation.