Research team of Professor Guan Wei and Professor Su Zhongmin, Northeast Normal University

Because of the synergistic effect between two different catalysts, the double catalysis has become an ideal choice However, little is known about its synergistic mechanism and its intrinsic nature of high reactivity and selectivity Recently, the research team of Professor Guan Wei and Professor Su Zhongmin of Northeast Normal University took the Ullmann cross coupling reaction of bromobenzene and 4-methoxyphenyl trifluoromethane sulfonate catalyzed by nickel (II) / palladium (II) bimetallic as the research object, used quantum chemical calculation method to study the reaction mechanism, and revealed nickel (I) / palladium (0) The orthogonal selectivity with substrate is the premise and basis of the reaction Moreover, nickel (I) is the main catalyst and palladium (0) plays a decisive role in the cross selectivity of the reaction The research results were recently published in chemical communications (chemical communications, 2018, 54, 7959 – 7962) Introduction to Associate Professor Guan Wei (right) and first author Zhu Bo (left) Guan Wei, associate professor and doctoral supervisor of Northeast Normal University In 2003, he graduated from the school of chemistry of Northeast Normal University, and in 2008, he graduated from the Institute of functional materials chemistry of Northeast Normal University with a doctor's degree From 2009 to 2014, he successively carried out the theoretical research work of multi acid functional material chemistry and metal organic catalysis in the National Key Laboratory of rare earth resource utilization, Changchun Institute of chemical engineering, Chinese Academy of Sciences and the memorial Research Institute of Fukui, Kyoto University, Japan In recent years, he has published nearly 20 papers in J am Chem SOC., ACS catalyst., chem Commun., inorg Chem., organizationals, J Phys Chem., Dalton trans And other academic journals as the first author and corresponding author He participated in the book application of quantum chemical calculation method in polyacid chemistry He has presided over and completed 9 projects, including the youth fund of the National Natural Science Foundation, general program, Doctoral Program Fund of the Ministry of education and Jilin Science and technology development plan Introduction to Professor Su Zhongmin, professor and doctoral supervisor of the school of chemistry, Northeast Normal University It is devoted to the design and synthesis of metal oxygen cluster materials, the synthesis and application of photoelectric functional materials, the theoretical research of nonlinear optical properties and electronic transmission properties of functional organic molecules / complexes, and the structural properties of new functional nano materials Professor Su Zhongmin presided over and completed 10 projects including "863 Plan" and "973 Plan" of the Ministry of science and technology of the people's Republic of China, key and general projects of the National Natural Science Foundation of the people's Republic of China, Yangtze River Scholar Award plan and innovation team project of the Ministry of education of the people's Republic of China, and application foundation project of the science and Technology Department of Jilin Province Apply for 15 national invention patents Since 2000, more than 340 SCI academic papers have been published in nature commun., J am Chem SOC., angew Chem Int ed, adv mater And other journals Frontier research achievements: theoretical research on the mechanism of synergistic Ullmann cross coupling reaction catalyzed by nickel / palladium bimetallic In the previous research, Professor Guan Wei and Professor Su Zhongmin's research team explored the mechanism of C − o cross coupling reaction catalyzed by iridium (III) / nickel (II) bimetallic, clarified the nature of the synergistic effect of iridium (III) / nickel (II) bimetallic, and revealed The origin of high selectivity of C − o cross coupling (chem Commun., 2018, 54, 5968-5971) In recent years, using bimetallic catalysis to realize the coupling reaction which is difficult or impossible for single metal catalysis has become a very powerful synthesis strategy in the organic field For example, the weix group of the University of Rochester in the United States realized the Ullmann cross coupling reaction of bromobenzene and 4-methoxyphenyl trifluoromethane sulfonate in the presence of zinc powder using nickel (II) / palladium (II) double Catalysis (Figure 1) The results show that the cross coupling products can be obtained with high selectivity by using nickel and palladium at the same time, while when using nickel catalyst alone, the products are mainly biphenyls Obviously, the orthogonal selectivity between Ni / PD double catalyst and substrate is the necessary condition to realize the cross coupling reaction However, due to the variable oxidation state of Ni / PD double catalysts, the mechanism of the double catalysis is still unclear This greatly limits its further development Therefore, the research team of Professor Guan Wei and Professor Su Zhongmin of Northeast Normal University took the reaction as the research object and used the quantum chemical calculation method to study the reaction mechanism in depth, so as to reveal the inherent nature of "orthogonal selectivity" and "cross selectivity" of nickel / palladium double catalysis Fig 1 Ullmann cross coupling reaction (source: Chemical Communications) of bromobenzene and 4-methoxyphenyl trifluoromethane sulfonate catalyzed by nickel / palladium In this reaction, zinc can be used as reducing agent to reduce nickel (II) and palladium (II) to nickel (I), nickel (0) and palladium (0) Therefore, in this work, the oxidation addition processes of nickel (I), nickel (0) and palladium (0) with two substrates were studied, respectively, so as to clarify the nature of orthogonal selectivity of nickel and palladium catalysts As shown in Figure 2, the coordination of nickel (0) and palladium (0) with the substrate is an irreversible process, so the stability of the coordination compounds formed by nickel (0) and palladium (0) with the substrate determines their selectivity to the substrate Therefore, both nickel (0) and palladium (0) tend to activate the c-otf bond On the contrary, for nickel (I), the choice of substrate depends on the activation energy of the oxidation addition step Therefore, nickel (I) tends to activate the C-Br bond In conclusion, the orthogonal selectivity between nickel (I) and palladium (0) rather than between nickel (0) and palladium (0) is a necessary prerequisite for the realization of this reaction In addition, the single electron reduction of nickel (II) and palladium (II) by zinc has been studied for two consecutive times The results show that nickel (I) and palladium (0) are indeed easier to form, which indicates that the active catalysts in this reaction are nickel (I) and palladium (0) Fig 2 the change of Gibbs free energy in the coordination process of bromobenzene and 4-methoxyphenyl trifluoromethane sulfonate with nickel (I), nickel (0) and palladium (0) respectively (△ g º) and the Gibbs activation energy in the oxidation addition step (△ g ≠) (source: Chemical Communications) In the process of aryl migration after oxidative addition, the aryl group can migrate to the center of nickel or palladium By comparing the two possible migration paths, the results show that the migration of aryl group to nickel center is more advantageous Therefore, as shown in Fig 3, the most feasible reaction path for this reaction is: (1) nickel (I) selectively activated C-Br bond to generate nickel (III) intermediate; (2) palladium (0) selectively activated c-otf bond to generate palladium (II) intermediate; (3) transfer metallized aryl between nickel (III) and palladium (II) intermediate to nickel (III) center; (4) reduction elimination The rate determining step is selective activation of C-Br bond by nickel (I), and the activation energy is 20.3kcal/mol, which can be overcome under the experimental conditions (40 ° C) Based on this, nickel (I) is the main catalyst in the current double catalysis Fig 3 the reaction path (source: Chemical Communications) of ulmann cross coupling of bromobenzene and 4-methoxyphenyl trifluoromethane sulfonate catalyzed by nickel / palladium In addition, in order to reveal the inherent nature of cross selectivity of nickel (I) and palladium (0), the authors studied the self coupling reaction of bromobenzene catalyzed by nickel (I) alone The results show that compared with Ni (I) / Pd (0) cross coupling, the self coupling reaction needs more activation energy This shows that the palladium (0) catalyst determines the cross selectivity of this reaction All in all, this work gives full play to the reliability and foresight of theoretical calculation, reveals the origin of orthogonal selectivity of Ni / Pd bimetallic catalyst, and clarifies its inherent nature of cross selectivity These knowledge can provide theoretical guidance for the development of novel and cheap bimetallic synergistic catalytic system and new cross coupling reaction in the future The research was supported by the National Natural Science Foundation of China, and the results were recently published on chemical communications The first author of the paper was Zhu Bo, a doctoral candidate of Northeast Normal University Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting 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