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    Home > Xi Zhenfeng Zhang Wenxiong group of Peking University: scandium "nitrogen" to the end: the construction of hydrazine carbon nitrogen bond

    Xi Zhenfeng Zhang Wenxiong group of Peking University: scandium "nitrogen" to the end: the construction of hydrazine carbon nitrogen bond

    • Last Update: 2019-06-12
    • Source: Internet
    • Author: User
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    Introduction: nitrogen is the most important component in the air and the most stable diatomic molecule in nature Nitrogen is the only nitrogen source of most nitrogen-containing compounds Therefore, the activation and transformation of nitrogen is not only of great scientific significance, but also of great challenge At present, through the Haber Bosch process, nitrogen and hydrogen are transformed into ammonia, and then ammonia is transformed into nitrogen compounds needed by human beings, so as to realize the activation and transformation of nitrogen However, due to the harsh reaction conditions and huge energy consumption of Haber Bosch process, the synthesis of nitrogen-containing organic compounds directly from nitrogen without ammonia under mild conditions is the "Holy Grail" that is naturally preset for scientists Recently, Xi Zhenfeng Zhang Wenxiong group of Peking University has realized the direct and efficient synthesis of hydrazine derivatives from nitrogen by using scandium complex as accelerator The results were published online in J am Chem SOC (J am Chem SOC 2019, 141, 8773) Xi Zhenfeng Zhang Wenxiong Research Office was founded in April 1998 Since its establishment, the core research content of the laboratory has been to use organometallic compounds to study new reagents, new reactions and new methods for highly selective organic synthesis During this period, the research room formed and adhered to the research room culture and scientific research methods of "synergy effect" and "deep new letter" At present, our research has focused on two challenging areas: rare earth organochemistry and nitrogen activation and transformation Prof Xi Zhenfeng, born in Yucheng County, Shangqiu City, Henan Province, is now a professor of Boya of Peking University and a member of the Chinese Academy of Sciences In 1983, he graduated from the Department of chemistry of Xiamen University; in 1989, he graduated from the Institute of coordination chemistry of Nanjing University, Zhengzhou University and Henan Institute of Chemistry (Supervisor: researcher Jin Douman); in 1996, he graduated from the Institute of molecular science of Japan (Supervisor: Professor Tamotsu Takahashi, Takahashi); in 1998, he was an associate professor of the school of chemistry of Peking University; 1999 Professor, School of chemistry, Peking University At present, he is the director of the National Research Center of Molecular Science in Beijing Prof Zhang Wenxiong, born in Ningxiang, Hunan Province, is a distinguished professor and doctoral supervisor of Beijing University In 1996, he received a bachelor's degree from Hunan Normal University; in 1999, he received a master's degree from Guangxi Normal University; in 2003, he received a doctor's degree from Nankai University (Tutor: academician song Licheng); he successively did postdoctoral research in the school of chemistry of Peking University (2002-2004, Tutor: academician Xi Zhenfeng) and the Institute of science and chemistry of Japan (2004-2007, tutor: Professor Hou Zhaomin); 2007 He has worked in the school of chemistry of Peking University since October, 2007, and has successively served as associate professor (2007), Professor (2016), special professor of Boya (2018), doctoral supervisor (2008) He won the ThiemeChemistry Journals Award in 2015 and the National Science Fund for Distinguished Young Scholars in 2017 Cutting edge scientific research achievements: scandium "nitrogen" to the end: the construction of hydrazine carbon nitrogen bond at present, human beings use the Haber Bosch process with high energy consumption and harsh reaction conditions to convert nitrogen and hydrogen into ammonia, and the vast majority of nitrogen-containing organic compounds are synthesized through ammonia Therefore, the synthesis of nitrogen-containing organic compounds from nitrogen without ammonia has been the focus and difficulty in the whole chemical field Although the formation of C-N bond promoted by transition metal and actinide metal has been reported, the research in this field is still in the initial stage As an important intermediate of organic synthesis, hydrazine derivative is one of the important targets of nitrogen direct conversion However, there are few reports on the direct synthesis of hydrazine derivatives from nitrogen, and the reaction efficiency and strategy are very limited Compared with transition metals, rare earth metal promoted synthesis of nitrogen-containing organic compounds from nitrogen has not been reported In this paper, scandium promoted synthesis of hydrazine derivatives directly from nitrogen is reported The intermediates of (N2) 2 − -, (N2) 3 − - and (N2 me 2) 2 − SC are separated and characterized It is found that CO can be effectively inserted into the SC − n bond of (N2 me 2) 2 − SC In this paper, the synthesis of nitrogen-containing organic compounds from nitrogen promoted by rare earth organic compounds is realized for the first time, and a new method is provided for the preparation of tetrasubstituted and 15 N-labeled hydrazine derivatives (Fig 1) Fig 1 Metal promoted synthesis of hydrazine derivatives directly from nitrogen (source: j.am Chem SOC.) the author first prepared scandium complexes 1 (Fig 2a) bridged by dichloro using the high yield of SCCL 3 and Cp * Li (Cp * = c5me 5) and Li [n BUC (NIPR) 2] In the presence of nitrogen, the complex 1 is reduced by metal potassium to obtain the binuclear (N2) 2 − SC complex 2 (Fig 2b) The structure of the complex 2 is further confirmed by Raman spectrum and 15 N NMR spectrum In the presence of [2.2.2] - cryptand, 2 can be reduced to (N2) 3 − SC complex 3 by excess metal potassium The n − n bond length is 1.3963 (16) ޹, which is between the n − n single bond and the double bond, and the n − n bond length of the complex 2 increases obviously EPR, Raman spectra and DFT calculations show that the single electron in 3 mainly concentrates on (N2) 3 − ligand The reaction of the complex 3 with the equivalent meotf gives the (N2 me2) 2 − SC complex 4, which is methylated by nitrogen atom, and generates the complex 2 at the same time (Fig 2e) Through the multiple reactions of 2 with metal potassium and meotf, the complex 4 can be obtained in a better yield (Fig 2f) In the single crystal structure of 4 (Fig 2), the n − n bond length is 1.5044 (16) ޹, which is significantly longer than the n − n bond length in complexes 2 and 3, indicating that the n − n bond in 4 exists in the form of a single bond For the first time, C − n bond was constructed from (N2) 3 − complex, which provided a new idea for nitrogen activation and transformation promoted by rare earth and transition metal Fig 2 Synthesis of complexes 1-4 and single crystal structure of 3 and 4 (source: j.am Chem SOC.) further transformation of 4 has very important research value because the nitrogen atom of (N2 me2) 2 − group in complexes 4 is directly from nitrogen When 4 reacts with anhydrous HCl and I 2, its (n 2me 2) 2 − group is converted into corresponding nitrogenous organic compounds 1,2-dimethylhydrazine 5 and azomethane 6 (Fig 3a and 3b) 4 can be further functionalized by reaction with carbon containing electrophilic reagents to form a new C − n bond For example, when 4 reacts with acyl chloride and benzyl bromide, a tetrasubstituted hydrazine derivative 8 − 10 (Fig 3 C − E) is obtained in a higher yield; in this reaction, a portion of scandium is converted into complexes 1 and 11 Complexes 7 and 11 can be reduced by metal potassium in nitrogen atmosphere to obtain complexes 2 Therefore, the author has realized scandium promoted synthesis cycle of hydrazine derivatives directly synthesized from nitrogen (Fig 4) The synthesis cycle mainly includes three steps: 1) in the presence of nitrogen, scandium halides are reduced by metal potassium to obtain (N2) 3 − SC complex 3; 2) 3 reacts with meotf to form complex 4; 3) 4 reacts with carbon containing electrophilic reagent to obtain hydrazine derivative 8 − 10, and regenerates precursor halides Fig 3 Reaction of complex 4 with HCl, I2 and carbon containing electrophilic reagent (source: j.am Chem SOC.) Fig 4 Synthesis cycle of hydrazine derivatives directly synthesized from nitrogen (source: j.am Chem SOC.) Co and N2 as two common molecules, it is of great scientific significance to directly construct C-N bond The complex 4 reacts with CO to obtain co inserted product 12 (Fig 5) In the single crystal structure of complex 12 (Fig 5), the bond lengths of C 3 − n 3 and C 3 − o 1 are 1.303 (3) and 1.367 (3) ޹, respectively, which are inconsistent with the C − n single bond and C = O double bond lengths of amide compounds reported in literature DFT calculation shows that the Wiberg bond index (WBI) of C3 − N3 and C3 − O1 is 1.41 and 1.11, respectively, in the complex 12, which shows that C3 − N3 has more double bond properties, while C3 − O1 is closer to single bond Therefore, there may be two resonance structures (Fig 6a and Fig 6b) in complex 12, and the contribution of B is greater than that of A Fig 5 Synthesis and single crystal structure of complex 12 (source: j.am Chem SOC.) in conclusion, this paper reports the process of scandium promoted direct and efficient synthesis of hydrazine derivatives from nitrogen, and the separation and characterization of (N2) 2 − -, (N2) 3 − - and (N2 me 2) 2 − - SC intermediates By the reaction of (n 2me 2) 2 − SC intermediate with CO, the C − n bond was constructed from CO and N 2 This work was published online in J am Chem SOC (J am Chem SOC 2019, 141, 8773) under the title of "scandium promoted direct conversion of dinitrogen into hydrazine derivatives via n − C bondformation" The first author of this paper is Lu Zejie, Ph.D student, School of chemistry, Peking University, and the corresponding authors are professor Xi Zhenfeng and Professor Zhang Wenxiong, Peking University The research was supported by the National Natural Science Foundation of China (NSFC and major programs), Peking University and Beijing Molecular Science Research Center 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 mechanism CBG information, chembeangoapp, chembeango official microblog, CBG wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the domestic representative research group, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.
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