PRINCIPAL INVESTIGATORPROF. DR. HOLGER BRAUNSCHWEIGProfessor of Inorganic Chemistry, Universität Würzburg
https://www.braunschweiggroup.de/ Founding Director, Institute for Sustainable Chemistry & Catalysis with Boron https://www.chemie.uni-wuerzburg.de/en/icb/icb-home/ |
Project overview
The ERC Advanced Grant project “Boron-Boron Multiple Bonding” (MULTIBB, project timeframe 2016-2021) was based on the poorly-understood and little-studied ability of boron atoms to form multiple bonds among themselves. While other, more common elements of the first row of the periodic table’s “main block” (i.e. carbon, nitrogen, oxygen) all have well-understood multiple bonding abilities, boron’s have remained little understood until recently. While filling this knowledge gap is a fundamental goal of this project, the inherently electron-rich and highly reactive nature of compounds with boron-boron multiple bonds make them fascinating reagents for further chemistry, suggesting the possibility of novel reactions with inert molecules and bond-forming processes. Our 2012 discoveries of high-yielding, reliable routes to compounds with B-B double and triple bonds, in conjunction with funding as part of the ERC Advanced Grant, have allowed us to embark on a comprehensive exploration of the possibilities of B-B multiple bonding in main-group chemistry, organic chemistry, coordination chemistry, and materials applications. The project aimed to explore the synthesis, diversity, and useful reactivity of B-B multiple bond systems, as well as determining how B-B multiple bonds interact in an intramolecular sense with other functional components.
The ERC Advanced Grant project “Boron-Boron Multiple Bonding” (MULTIBB, project timeframe 2016-2021) was based on the poorly-understood and little-studied ability of boron atoms to form multiple bonds among themselves. While other, more common elements of the first row of the periodic table’s “main block” (i.e. carbon, nitrogen, oxygen) all have well-understood multiple bonding abilities, boron’s have remained little understood until recently. While filling this knowledge gap is a fundamental goal of this project, the inherently electron-rich and highly reactive nature of compounds with boron-boron multiple bonds make them fascinating reagents for further chemistry, suggesting the possibility of novel reactions with inert molecules and bond-forming processes. Our 2012 discoveries of high-yielding, reliable routes to compounds with B-B double and triple bonds, in conjunction with funding as part of the ERC Advanced Grant, have allowed us to embark on a comprehensive exploration of the possibilities of B-B multiple bonding in main-group chemistry, organic chemistry, coordination chemistry, and materials applications. The project aimed to explore the synthesis, diversity, and useful reactivity of B-B multiple bond systems, as well as determining how B-B multiple bonds interact in an intramolecular sense with other functional components.
Results of the project
The first part of the project involved a wide-scope expansion of the structural diversity of diborenes and diborynes, by altering the two available components of the compounds, the anionic substituent and the Lewis base unit. While some components were chosen for their conventional nature and stability-enhancing characteristics, others were chosen as they were the opposite, i.e. destabilising and reactivity enhancing. Other units were incorporated as “leaving groups”, i.e. to direct reactivity of the compound away from the B-B multiple bond and towards other bonds of the molecule. In other cases, functional components were incorporated that allowed us to study the interaction and/or communication between the B-B multiple bond and the functional unit, such as electronic-conducting, wire-like units, units with empty orbitals, strongly electron-accepting or -donating units, units with multiple redox states. The second part of the project was based on a comprehensive exploration of the reactivity of diborenes and diborynes, taking advantage of their highly electron-rich nature and high reactivity. Thereby, diborenes and diborynes were subjected to a wide range of reagents in a strategic fashion, ranging from highly reactive species such as strong oxidants to relatively inert molecules of societal and industrial importance, such as carbon dioxide, alkynes, amines, etc. The results of these reactions have radically broadened our understanding of the reactivity of B-B multiple bonds, leading to a long list of novel bond activation processes. Many of these reactions gave the expected product, e.g. simple additions of two groups across the B2 unit or reactions known with their organic counterparts. However, many others gave completely unexpected products, such as C-C bond cleavage products, diborabenzenes, additions across a single boron atom, etc.
Communication of the project results
To date, the results of the project have been published in 42 peer-reviewed articles, with three further papers currently submitted. 31 of the published articles have appeared in top general science or general chemistry journals with impact factors above nine (e.g. Journal of the American Chemical Society (5), Angewandte Chemie (20), Nature Communications (1), Chemical Science (4), Chemical Reviews (1)). The published papers have already attracted over 700 citations (Web of Science), with an average number of citations per paper of ca. 18, and two are designated Highly Cited Papers by the Web of Science (top 1% in citations for its field). The publication output includes three major reviews that have been published in premier chemistry journals (one in Chemical Reviews, two in Angewandte Chemie). Eight of the papers emerging from this project have been the subject of highlights by other scientific journals and magazines (Nature Communications, Chemistry World, Angewandte Chemie, Synfacts, Nachrichten aus der Chemie). Results of the project have been communicated in a range of other ways, such as conference participation (ca. 40 oral and poster presentations from the PI, students and postdocs working on the project), lecture tours and award lectures.
Other outcomes of the project
The project has been a massive benefit for the training and career prospects of its participants, who have moved into a range of different areas since completing their work on the project. The principal investigator, Prof. Holger Braunschweig, has received numerous awards, fellowships, lectureships and memberships of scientific academies based in part on the work performed in this project. Seven of the other employees on the project remain in the group (as staff scientists, technicians or Ph.D. students), five have taken up positions in industry, one currently works in a non-university research institute, and two have taken up Assistant Professorships at top institutions in their respective home countries (McGill University, Canada and the Indian Institute of Technology Indore, India).
Publications arising from the project
A list of publications from this project can be obtained from Google Scholar by following this link: full publication list
The first part of the project involved a wide-scope expansion of the structural diversity of diborenes and diborynes, by altering the two available components of the compounds, the anionic substituent and the Lewis base unit. While some components were chosen for their conventional nature and stability-enhancing characteristics, others were chosen as they were the opposite, i.e. destabilising and reactivity enhancing. Other units were incorporated as “leaving groups”, i.e. to direct reactivity of the compound away from the B-B multiple bond and towards other bonds of the molecule. In other cases, functional components were incorporated that allowed us to study the interaction and/or communication between the B-B multiple bond and the functional unit, such as electronic-conducting, wire-like units, units with empty orbitals, strongly electron-accepting or -donating units, units with multiple redox states. The second part of the project was based on a comprehensive exploration of the reactivity of diborenes and diborynes, taking advantage of their highly electron-rich nature and high reactivity. Thereby, diborenes and diborynes were subjected to a wide range of reagents in a strategic fashion, ranging from highly reactive species such as strong oxidants to relatively inert molecules of societal and industrial importance, such as carbon dioxide, alkynes, amines, etc. The results of these reactions have radically broadened our understanding of the reactivity of B-B multiple bonds, leading to a long list of novel bond activation processes. Many of these reactions gave the expected product, e.g. simple additions of two groups across the B2 unit or reactions known with their organic counterparts. However, many others gave completely unexpected products, such as C-C bond cleavage products, diborabenzenes, additions across a single boron atom, etc.
Communication of the project results
To date, the results of the project have been published in 42 peer-reviewed articles, with three further papers currently submitted. 31 of the published articles have appeared in top general science or general chemistry journals with impact factors above nine (e.g. Journal of the American Chemical Society (5), Angewandte Chemie (20), Nature Communications (1), Chemical Science (4), Chemical Reviews (1)). The published papers have already attracted over 700 citations (Web of Science), with an average number of citations per paper of ca. 18, and two are designated Highly Cited Papers by the Web of Science (top 1% in citations for its field). The publication output includes three major reviews that have been published in premier chemistry journals (one in Chemical Reviews, two in Angewandte Chemie). Eight of the papers emerging from this project have been the subject of highlights by other scientific journals and magazines (Nature Communications, Chemistry World, Angewandte Chemie, Synfacts, Nachrichten aus der Chemie). Results of the project have been communicated in a range of other ways, such as conference participation (ca. 40 oral and poster presentations from the PI, students and postdocs working on the project), lecture tours and award lectures.
Other outcomes of the project
The project has been a massive benefit for the training and career prospects of its participants, who have moved into a range of different areas since completing their work on the project. The principal investigator, Prof. Holger Braunschweig, has received numerous awards, fellowships, lectureships and memberships of scientific academies based in part on the work performed in this project. Seven of the other employees on the project remain in the group (as staff scientists, technicians or Ph.D. students), five have taken up positions in industry, one currently works in a non-university research institute, and two have taken up Assistant Professorships at top institutions in their respective home countries (McGill University, Canada and the Indian Institute of Technology Indore, India).
Publications arising from the project
A list of publications from this project can be obtained from Google Scholar by following this link: full publication list