Phosphorus ligands with a large cavity: Synthesis of triethynylphosphines with bulky end caps and application to the rhodium-catalyzed hydrosilylation of ketones
Phosphorus ligands with a large cavity: Synthesis of triethynylphosphines with bulky end caps and application to the rhodium-catalyzed hydrosilylation of ketones
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DOI：
10.1002/asia.200700006
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发表时间：
2007-01-01
影响因子：
4.1
通讯作者：
Sawamura, Masaya
中科院分区：
文献类型：
--
作者：
Ochida, Atsuko;Sawamura, Masaya
合成了在炔端被大体积的三芳基硅基取代的三炔基膦。新的膦配体P（C = CSiAr 3，）3（Ar = 3，5-tBu（2）-4-MeOC 6 H2，3，5-（Me 3Si）（2）C6 H3）在磷原子附近是不拥挤的，但在远端区域是大体积的.因此，它们包含一个大的空腔，磷化氢孤对电子位于空腔的底部。该化合物对空气氧化和水解稳定。DFT计算表明，三乙炔基膦是良好的π受体配体，与P（OAr）（3）相当。三炔基膦与[{RhCl（cod）}（2）]（P/Rh = 1.1：1）反应，选择性地生成单膦铑配合物[RhCl（cod）P（C-CSiAr 3）（3）]。X射线晶体结构分析表明，{RhCl（COD）}片段完全容纳的膦配体的空腔。与具有较小端帽和PPh 3的类似物的效果相比，三炔基膦显著加速了铑催化的酮与三有机硅烷的硅氢加成反应。有人提出，观察到的多孔膦的较高的催化活性是一个单膦铑物种的优先形成的结果。
Trialkynylphosphines substituted with bulky triarylsilyl groups at the alkyne termini were synthesized. The new phosphines P(C equivalent to CSiAr3,)3 (Ar = 3,5-tBu(2)-4-MeOC6H2, 3,5-(Me3Si)(2)C6H3) are uncrowded near the phosphorus atom but bulky in the distal region. As a result, they contain a large cavity, at the bottom of which the phosphine lone-pair electrons are located. The compounds are stable to oxidation by air and hydrolysis. DFT calculations suggested that the triethynylphosphines are good pi-acceptor ligands, comparable with P(OAr)(3). ne trialkynylphosphines reacted with [{RhCl(cod)}(2)] (P/Rh = 1.1:1) to give selectively the monophosphine-rhodium complex [RhCl(cod)P(C CSiAr3)(3)]. X-ray crystal-structure analysis revealed that the {RhCl(cod)} fragment is fully accommodated by the cavity of the phosphine ligand. Compared to the effect of analogues with smaller end caps and PPh3, the trialkynylphosphines accelerated markedly the rhodium-catalyzed hydrosilylation of ketones with a trioganosilane. It is proposed that the higher catalytic activity observed with the holey phosphines is a result of the preferential formation of a monophosphine-rhodium species.