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Catalytic applications of rhodium complexes containing trialkylphosphines

机译：含三烷基膦的铑配合物的催化应用

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The uses of trialkyl complexes of rhodium as homogeneous catalysts are reviewed. Although they have been much less studied than their triarylphosphine counterparts, rhodium trialkyl-phosphine complexes do have certain properties which make them suitable for a wide range of catalytic reactions, for some of which, they are the only systems available, or are the catalysts of choice. The major difference between complexes containing trialkylphosphines and those with triarylphosphines is that the electron donating trialkylphosphines lead to a much higher electron density on the metal and hence make oxidative addition reactions, even of difficult substrates, more facile. Examples of where this is particularly beneficial include the photocatalysed activation of alkanes, either to produce alkenes and H_2 or, in the presence of CO, to produce homologous aldehydes; the activation of amines in the hydroamination of alkenes; their ability to dehydrogenate alcohols, directly, via transfer of hydrogen to acceptors such as alkenes, or in hydrocarbonylation reactions where the alcohol is the hydrogen source; the water-gas shift reaction; their ability to catalyse the carbonylation of allylchlorides and CH_2I_2. Another example of the effect of the high electron density on the metal is the production of alcohols, rather than aldehydes as the primary products from alkenes under hydroformyla-tion reaction conditions, which is believed to proceed via an hydroxycarbene complex formed by protonation of an acyl intermediate. The hydrogenation of CO catalysed by trialklyphos-phine complexes of rhodium may also be possible because the high electron density on the rhodium makes a hydrido ligand sufficiently hydridic for it to be transferred to CO coordinated to another rhodium centre to form the crucial formyl intermediate. In addition to these rather unusual reactions, trialkylphosphine complexes of rhodium also show activity for a variety of other more classical reactions, such as hydrogenation (especially of aldehydes and ketones), hydrosilylation, hydroboration and condensation reactions of alkenes and alkynes. For most of these reactions, apart from the hydrogenation of aldehydes, these catalysts tend to be inferior to their triarlyphosphine counterparts.
机译：综述了铑的三烷基络合物作为均相催化剂的用途。尽管与三芳基膦对应物相比，它们的研究少得多，但是三烷基铑膦配合物确实具有某些特性，使其适合于广泛的催化反应，对于某些催化反应，它们是唯一可用的体系，或者是它们的催化剂。选择。含有三烷基膦的配合物与具有三芳基膦的配合物之间的主要区别在于，给电子的三烷基膦导致金属上的电子密度更高，因此，即使是难处理的底物，其氧化加成反应也更加容易。其中特别有益的例子包括光催化活化烷烃以产生烯烃和H_2，或在CO存在下产生同源醛；烯烃加氢胺化中胺的活化；通过将氢转移到受体（例如烯烃）或在醇为氢源的烃基化反应中直接将醇脱氢的能力；水煤气变换反应；它们催化烯丙基氯和CH_2I_2羰基化的能力。高电子密度对金属的影响的另一个示例是在加氢甲酰化反应条件下从烯烃生产醇而不是醛作为主要产物的醛，据信这是通过酰基质子化形成的羟基卡宾络合物进行的中间。由于铑的三烯丙基磷化膦配合物催化的CO的氢化也是可能的，因为在铑上的高电子密度使氢化配体具有足够的亲水性，使其可以转移到与另一个铑中心配位的CO上，从而形成关键的甲酰基中间体。除了这些相当不寻常的反应之外，铑的三烷基膦配合物还对多种其他更经典的反应具有活性，例如氢化（尤其是醛和酮的氢化），烯烃和炔烃的氢化硅烷化，氢化硼化和缩合反应。对于大多数这些反应，除了醛的氢化作用外，这些催化剂往往不如它们的三芳基膦对应物。

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