Abstract
It is vital to design effective nitrogen fixation systems that operate under mild conditions, and to this end we recently reported an example of the catalytic formation of ammonia using a dinitrogen-bridged dimolybdenum complex bearing a pincer ligand, where up to twenty three equivalents of ammonia were produced based on the catalyst. Here we study the origin of the catalytic behaviour of the dinitrogen-bridged dimolybdenum complex bearing the pincer ligand with density functional theory calculations, based on stoichiometric and catalytic formation of ammonia from molecular dinitrogen under ambient conditions. Comparison of di- and mono-molybdenum systems shows that the dinitrogen-bridged dimolybdenum core structure plays a critical role in the protonation of the coordinated molecular dinitrogen in the catalytic cycle.
Highlights
It is vital to design effective nitrogen fixation systems that operate under mild conditions, and to this end we recently reported an example of the catalytic formation of ammonia using a dinitrogen-bridged dimolybdenum complex bearing a pincer ligand, where up to twenty three equivalents of ammonia were produced based on the catalyst
Among a variety of transition metal–dinitrogen complexes known to date, molybdenum–dinitrogen complexes have intriguing reactivities because the coordinated dinitrogen on the molybdenum atom is converted into ammonia by the protonation with inorganic acids such as sulphuric acid, where only a stoichiometric amount of ammonia is produced based on the molybdenum atom[10,11,12]
In 2003, Schrock and co-worker found the first example of the catalytic conversion of molecular dinitrogen into ammonia by using molybdenum–dinitrogen complex bearing a triamidoamine as the supporting ligand under ambient conditions, where less than 8 equiv of ammonia were produced based on the molybdenum atom[22,23,24,25,26]
Summary
It is vital to design effective nitrogen fixation systems that operate under mild conditions, and to this end we recently reported an example of the catalytic formation of ammonia using a dinitrogen-bridged dimolybdenum complex bearing a pincer ligand, where up to twenty three equivalents of ammonia were produced based on the catalyst. As an extensive study on the development of novel nitrogen fixation systems under ambient reaction conditions[28,29,30,31,32,33,34,35,36], we have recently found another successful example of the catalytic conversion of molecular dinitrogen into ammonia by using dinitrogen-bridged dimolybdenum complex bearing a PNP-type pincer ligand [Mo(N2)2(PNP)]2(m-N2) (1: PNP 1⁄4 2,6-bis (di-tert-butylphosphinomethyl)pyridine), where up to 23 equiv of ammonia were produced based on the catalyst (12 equiv of ammonia based on the molybdenum atom)[37,38,39,40,41]. The combined experimental and theoretical studies reveal that the dinitrogen-bridged dimolybdenum core structure plays a crucial role to promote the catalytic reaction in the protonation of the coordinated molecular dinitrogen in the catalytic cycle This result is in sharp contrast to our previous proposals, where only mononuclear molybdenum complexes were proposed to work as key reactive intermediates[37,38,39,40,41]. We propose a new catalytic reaction pathway with the aid of DFT calculations and experimental results
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
