Université de Lyon 1, Institut de Chimie de Lyon, CNRS, UMR 5265 C2P2 (CNRS/CPE/UCBL), LCOMS-CPE Lyon, Bâtiment 308F, 43 Blvd du 11 Novembre 1918, F-69616 Villeurbanne Cedex, France.
Acc Chem Res. 2010 Feb 16;43(2):323-34. doi: 10.1021/ar900203a.
The transformation of alkanes remains a difficult challenge because of the relative inertness of the C-H and C-C bonds. The rewards for asserting synthetic control over unfunctionalized, saturated hydrocarbons are considerable, however, because converting short alkanes into longer chain analogues is usually a value-adding process. Alkane metathesis is a novel catalytic and direct transformation of two molecules of a given alkane into its lower and higher homologues; moreover, the process proceeds at relatively low temperature (ambient conditions or higher). It was discovered through the use of a silica-supported tantalum hydride, ([triple bond]SiO)(2)TaH, a multifunctional catalyst with a single site of action. This reaction completes the story of the metathesis reactions discovered over the past 40 years: olefin metathesis, alkyne metathesis, and ene-yne cyclizations. In this Account, we examine the fundamental mechanistic aspects of alkane metathesis as well as the novel reactions that have been derived from its study. The silica-supported tantalum hydride catalyst was developed as the result of systematic and meticulous studies of the interaction between oxide supports and organometallic complexes, a field of study denoted surface organometallic chemistry (SOMC). A careful examination of this surface-supported tantalum hydride led to the later discovery of alumina-supported tungsten hydride, W(H)(3)/Al(2)O(3), which proved to be an even better catalyst for alkane metathesis. Supported tantalum and tungsten hydrides are highly unsaturated, electron-deficient species that are very reactive toward the C-H and C-C bonds of alkanes. They show a great versatility in various other reactions, such as cross-metathesis between methane and alkanes, cross-metathesis between toluene and ethane, or even methane nonoxidative coupling. Moreover, tungsten hydride exhibits a specific ability in the transformation of isobutane into 2,3-dimethylbutane as well as in the metathesis of olefins or the selective transformation of ethylene into propylene. Alkane metathesis represents a powerful tool for making progress in a variety of areas, perhaps most notably in the petroleum and petrochemical fields. Modern civilization is currently confronting a host of problems that relate to energy production and its effects on the environment, and judicious application of alkane metathesis to the processing of fuels such as crude oil and natural gas may well afford solutions to these difficulties.
烷烃的转化仍然是一个具有挑战性的难题，因为 C-H 和 C-C 键相对惰性。然而，对未官能化的饱和烃施加合成控制的回报是相当可观的，因为将短链烷烃转化为更长链的类似物通常是一个增值过程。烷烃复分解是一种新型的催化和直接转化给定烷烃的两种分子成其较低和较高同系物的方法；此外，该过程在相对较低的温度（环境条件或更高）下进行。它是通过使用负载在二氧化硅上的钽氢化物，([三键]SiO)(2)TaH，一种具有单一作用位点的多功能催化剂发现的。这一反应完成了过去 40 年发现的复分解反应的故事：烯烃复分解、炔烃复分解和烯炔环化。在本说明中，我们检查了烷烃复分解的基本机理方面以及从其研究中衍生出来的新反应。负载在二氧化硅上的钽氢化物催化剂是通过对氧化物载体和有机金属配合物之间相互作用的系统和细致研究开发的，这一研究领域被称为表面有机金属化学（SOMC）。对这种负载在二氧化硅上的钽氢化物的仔细研究导致了后来发现氧化铝负载的钨氢化物，W(H)(3)/Al(2)O(3)，它被证明是烷烃复分解的更好的催化剂。负载的钽和钨氢化物是高度不饱和的、缺电子的物种，对烷烃的 C-H 和 C-C 键非常反应。它们在各种其他反应中表现出极大的多功能性，例如甲烷和烷烃之间的交叉复分解、甲苯和乙烷之间的交叉复分解，甚至甲烷非氧化偶联。此外，钨氢化物在将异丁烷转化为 2,3-二甲基丁烷以及在烯烃复分解或选择性将乙烯转化为丙烯方面表现出特定的能力。烷烃复分解是在各种领域取得进展的有力工具，在石油和石化领域可能最为显著。现代文明目前正面临着一系列与能源生产及其对环境的影响有关的问题，明智地将烷烃复分解应用于处理原油和天然气等燃料可能为这些困难提供解决方案。
