Читать книгу Computational Methods in Organometallic Catalysis - Yu Lan - Страница 15

As an interdiscipline of organic and inorganic chemistry, organometallic chemistry has a history of almost 200 years since the first complex K[(C₂H₄)PtCl₃]·H₂O was reported by Zeise when he heated ethanol solution of PtCl₄/KCl [62]. The history of organometallic chemistry can be roughly divided into four stages. The chemists majorly focused on main group organometallic compounds in the nineteenth century. Later in the first half of the twentieth century, chemists paid more attention to understanding the structures of organometallic compounds involving transition metals. Then in the latter half of the twentieth century, various transition metal‐catalyzed reactions had been widely reported. Since this century, chemists have been keen on using transition metal catalysis to selectively construct more complex organic compounds. The outlined history of organometallic chemistry could be concluded in Scheme 1.3 [63].

Scheme 1.3 A brief history of organometallic chemistry.

Source: Based on Didier [63].

The nineteenth century could be considered as the enlightenment era of organometallic chemistry. Frankland first systemically investigated organometallic chemistry and prepared a series of alkyl metal compounds in 1850s. In the late nineteenth century, ZnMe₂ (in 1849 by E. Frankland), Sn(C₂H₅)₄ (in 1859 by E. Frankland), PbEt₄ (in 1853 by C. Löwig), Al₂Et₃I₃ (in 1859 by W. Hallwachs and A. Schafarik), and RMgX (in 1900 by V. Grignard) had been prepared, and the chemical property of those compounds also had been studied [64–68].

In 1890, Ni(CO)₄ was found as the first metal carbonyl complex by L. Mond et al. in the study of the corrosion of stainless steel valves by CO [69]. Next year, Fe(CO)₅ was also found by the same group [70]. It could be considered as the beginning of the structural study of organometallic complexes. Two years later, Werner proposed structural theory of organometallic complexes involving the tetrahedral, octahedral, square planar, etc. which won him the Nobel prize in chemistry in 1913 [71]. In 1919, Cr(C₆H₆)₂ was prepared by Hein using MgPhBr to react with CrCl₃ [72]. However, the sandwich‐like structure of this complex was proved by Fischer 36 years later. In 1951, Fe(C₅H₅)₂ had been synthesized by Kealy and Pauson individually [73]. The sandwich‐like structure of that complex was confirmed by G. Wilkinson the following year, which aroused chemists' enthusiasm for the study of transition metal organic compounds. In 1964, tungsten carbene complex was reported by Fischer, who shared 1973 Nobel prize in chemistry with G. Wilkinson [74]. By the 1950s, with the appearance of representational methods, involving X‐ray crystallography, infrared spectrum, and nuclear magnetic resonance spectrum, means of characterizing transition metal compounds were becoming more and more mature. Therefore, organometallic chemistry became an independent discipline.

From the middle of the twentieth century, organometallic compounds were gradually considered as a catalyst in organic reactions. In 1953, Ziegler and Natta found that TiCl₄/AlEt₃ could promote atmospheric polymerization of olefins, which helped them share 1963 Nobel prize in chemistry [75, 76]. In 1959, allylic palladium was prepared by Smidt and Hafner, which was the beginning of π‐allyl metal chemistry [77]. The same year, Shaw and Ruddick reported an elementary reaction of oxidative addition [78]. In 1974, Wilkinson reported another elementary reaction of β‐hydride elimination [79]. Those works led to a series of following mechanistic studies for organometallic reactions. In 1972, Heck and Nolley reported a palladium‐catalyzed coupling reaction between aryl halides and olefins, which was named Heck reaction [80]. Meanwhile, a series of palladium‐catalyzed cross‐coupling reaction, including Kumada coupling with Grignard reagent [81], Suzuki coupling with aryl borane [82], Negishi coupling with organo zinc [83], Stille coupling with aryl tin [84], and Sonogashira coupling with alkynyl copper [85], were reported. Those reactions made transition metal‐catalyzed cross‐coupling reactions one of the most important ways to construct new C—C covalent bonds in synthetic chemistry. Therefore, R. F. Heck, E. Negishi, and A. Suzuki won the 2010 Nobel prize in chemistry. Also in 1971, W. S. Knowles applied chiral bisphosphine ligands as ligand in rhodium‐catalyzed hydrogenation reactions, which had opened up a whole new field of asymmetric catalysis with transition metals [86]. W. S. Knowles shared 2001 Nobel prize in chemistry with K. B. Sharples and R. Noyori, who promoted the research upsurge of asymmetric catalysis. Moreover, Chauvin, Grubbs, and Schrock won the 2005 Nobel prize in recognition of their outstanding contributions in transition metal‐mediated metathesis of olefins.

Based on the advances of methodology study and ligand design, transition metal catalysis has become one of the important means for synthetic chemists to construct more complex new substances in this century. The current pursuit is to selectively construct multiple covalent bonds in one reaction synchronously by transition metal catalysis. To achieve this goal, transition metal catalyst has been employed to selectively activate some inert covalent bonds. The most famous example – transition metal‐mediated C—H bond activation – became the focus of chemists. This process could afford a carbon–metal bond directly, which could be used as a powerful nucleophile in further transformations. In modern organometallic chemistry, multistep elementary reactions in series have been extensively studied, which could afford a battery of new covalent bonds through one catalytic cycle. Synthetic efficiency in organometallic chemistry has become the focus of attention. Hereon, transition metal catalysis with higher turnover numbers was pursued to further improve the economy and environmental protection. Current research on transition metal catalysis is also devoted to improving the accuracy of synthesis, aiming at achieving specific functional group transformation in the exact location. To achieve these goals, the design of transition metal catalysis becomes more complex, and the requirements for suitable ligands are higher. It is necessary to design the corresponding ligands manually according to aspects of structure, electronic properties, steric effect, and coordination ability. These auxiliary designs also make the catalytic cycle with transition metal lengthier; meanwhile, the possibility of side reactions increases. Therefore, mechanistic studies for transition metal catalysis became more and more important, which were helpful for design of new catalysis, enhanced efficiency, increased selectivity, improved turnover number, and accurate synthesis.