Catalytic C-F bond activation of hexafluoropropene by rhodium:: Formation of (3,3,3-trifluoropropyl)silanes
Catalytic C-F bond activation of hexafluoropropene by rhodium:: Formation of (3,3,3-trifluoropropyl)silanes
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DOI：
10.1002/anie.200700711
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发表时间：
2007-01-01
影响因子：
16.6
通讯作者：
Altenhoener, Kai
中科院分区：
文献类型：
--
作者：
Braun, Thomas;Wehmeier, Falk;Altenhoener, Kai
过渡金属中心对碳-氟键的活化是有机金属化学中的一个既定过程。[1]目前的兴趣包括开发从容易获得的前体生产高价值氟化化合物的新途径。该策略涉及在高度氟化的基底中选择性地裂解C2 H2 F键以获得氟化的结构单元，然后可以在金属的配位层中进一步官能化。[1，2]在使用CCl 3F活化反应合成氟化分子方面已经取得了惊人的进展，但催化反应仍然很少。转化包括非常有限数量的交叉偶联反应。[3，4]在另一个例外的实例中，通过使用[Rh（cod）2] BF 4作为催化剂（cod=环辛烷）用六甲基二硅烷催化转化官能化的氟苯如氟苯乙酮或（氟苯基）恶唑啉来形成碳-硅键。[5]已报道的大多数其他实例涉及简单的加氢脱氢步骤。[1，2]关于涉及氟化烯烃中的C13 F键的裂解的化学计量或甚至催化转化的报道非常少。[1，4，6-8]同样，几乎所有的反应都涉及加氢脱氟。唯一的例外涉及1，1-二氟-2-萘基丙烯与[（甲苯基）ZnCl]的钯催化的交叉偶联反应，得到单甲苯基和二甲苯基衍生物。[4]Holland及其同事表明，六氟丙烯可以催化转化为五氟丙烯的混合物，转化数（TON）为9.8。[7]这里，二酮亚胺铁（II）氟络合物用作催化剂。在最近的一个例子中，Peterson和麦克尼尔报道了在HSiEt 3存在下氟乙烯或氯氟乙烯的铑催化加氢脱卤，得到具有可比TON的乙烷。[8]We已经表明，通过使用二氢作为氢源，六氟丙烯可以转化为1，1，1-三氟丙烯，但是该转化不是催化的。[9，10]加氢脱氨反应基于六氟丙烯被[RhH（PEt 3）3]（1a）活化以产生铑衍生物[Rh {（Z）-CF= CF（CF 3）}（PEt 3）3]（2）。后者与二氢反应得到1，1，1-三氟丙烯和氟配合物[RhF（PEt 3）3]（3）。在这里，我们提出我们的结果与叔硅烷的反应性2。这些研究导致开发了一种催化方法，用于通过C2 H2 F键活化将六氟丙烯转化为（3，3，3-三氟丙基）硅烷。反应在室温下进行，具有良好的TON，并且是非常选择性的。它们的独特之处在于：1）它们涉及氟化烯烃的罕见的催化C3 F键活化，和2）催化循环，沿着加氢脱氢步骤，涉及C3 Si键的形成。用过量的Ph 3SiH处理2的溶液导致选择性地形成（3，3，3-三氟丙基）硅烷4a和二氢甲硅烷基络合物cis-fac-[Rh（H）2（SiPh 3）-（PEt 3）3]（5）[10]（方案1）。使用亚化学计量量的Ph 3SiH的实验也选择性地得到硅烷4a和络合物5，但起始化合物2仍然存在。
The activation of carbon–fluorine bonds by transition-metal centers is an established process in organometallic chemistry.[1] Current interests include the development of new routes to higher-value fluorinated compounds from easily accessible precursors. The strategy involves the selective cleavage of a CÀF bond in a highly fluorinated substrate to obtain fluorinated building blocks that then can be functionalized further in the coordination sphere of the metal.[1, 2] There have been striking advances in the synthesis of fluorinated molecules using CÀF activation reactions, but catalytic reactions are still rare. The transformations include a very limited number of cross-coupling reactions.[3, 4] In another exceptional example, carbon–silicon bonds are formed by catalytic conversions of functionalized fluorobenzenes, such as fluoroacetophenones or (fluorophenyl) oxazolines, with hexamethyldisilane using [Rh (cod) 2] BF4 as catalyst (cod= cyclooctadiene).[5] Most of the other examples that have been reported involve simple hydrodefluorination steps.[1, 2] Very little has been reported on stoichiometric or even catalytic transformations that involve the cleavage of a CÀF bond in a fluorinated olefin.[1, 4, 6–8] Again, almost all of the reactions involve hydrodefluorinations. The only exception involves a palladium-catalyzed cross-coupling reaction of 1, 1-difluoro-2-naphtylpropene with [(tolyl) ZnCl] to give monoand ditolyl derivatives.[4] Holland and co-workers showed that hexafluoropropene can be converted catalytically into a mixture of pentafluoropropenes with a turnover number (TON) of 9.8.[7] Here, a diketiminate iron (II) fluoro complex served as the catalyst. In a very recent example, Peterson and McNeill reported on the rhodium-catalyzed hydrodehalogenation of vinylfluoride or chlorofluoroethylenes in the presence of HSiEt3 to give ethane with comparable TONs.[8]We have already shown that hexafluoropropene can be converted into 1, 1, 1-trifluoropropene by using dihydrogen as hydrogen source, but the transformation was not catalytic.[9, 10] The hydrodefluorination reaction is based on the activation of hexafluoropropene by [RhH (PEt3) 3](1a) to yield the rhodium derivative [Rh {(Z)-CF= CF (CF3)}(PEt3) 3](2). The latter complex reacts with dihydrogen to give 1, 1, 1-trifluoropropene and the fluoro complex [RhF (PEt3) 3](3). Herein we present our results on the reactivity of 2 with tertiary silanes. The studies led to the development of a catalytic process for the conversion of hexafluoropropene into (3, 3, 3-trifluoropropyl) silanes by CÀF bond activation. The reactions proceed at room temperature with good TONs and are very selective. They are unique in that 1) they involve a rare catalytic CÀF bond activation of a fluorinated alkene, and 2) the catalytic cycle, along with the hydrodefluorination steps, involves the formation of a CÀSi bond. Treatment of a solution of 2 with an excess Ph3SiH led to the selective formation of the (3, 3, 3-trifluoropropyl) silane 4a and the dihydridosilyl complex cis-fac-[Rh (H) 2 (SiPh3)-(PEt3) 3](5)[10](Scheme 1). An experiment with substoichiometric amounts of Ph3SiH also gave selectively the silane 4a and complex 5, but the starting compound 2 was still present.