Remote B-H activation in unconventional multidentate boranes. – ReBAB

Experimentaly, all manipulations are performed under an inert argon atmosphere using vacuum lines and glove box techniques. Analysis involve multinucleus NMR spectroscopy (31P, 13C, 11B, 1H, 2H...) and X-ray diffraction. Theoretical calculations performed at a high level enable molecular modelling to model and rationalize the behaviour of the obtained molecules.
The approach involved the building of a library of new multidented L~BH boranes, the study of their coordination affording new sigma-borane agostic complexes, the evaluation of the impact of the spacer on the coordination mode of the ligand for applications in catalysis, and the evaluation of the energetics that governs the behaviour of these species.

Good results have been obtained despite a chemistry diffu t to be implemented.
- the library of ligand with a variety of structure has been obtained.
- their coordination has been studied showing a major influence of the peripheral functional group on the activation level of the B-H bond.
- Applications in catalysis have been performed leading to very interesting results.
- Number of the results could have been rationalized via a theoretical apppoach involving computational studies.

Participate in the global knowledge. THis project is at a fundamental level andf aims at better understand, explain and take advantage of the best results for future applications.

- Synthesis of a ruthenium bis(diisopropylamino(isocyano)borane) complex from the activation of an amino(cyano)borane, M. Joost, G. Alcaraz, L. Vendier, A. Poblador-Bahamonde, E. Clot, S. Sabo-Etienne, Dalton Trans. 2013, 42, 776-781.
- B-H, C-H, and B-C bond activation: the role of two adjacent agostic interactions Cassen, A.; Gloaguen, Y.; Vendier, L.; Duhayon, C.; Poblador-Bahamonde, A.; Raynaud, C.; Clot, E.; Alcaraz, G.; Sabo-Etienne, S., Angew. Chem., Int. Ed. Engl. 2014, 53, 7569-73.
- B-C Bond Cleavage and Ru-C Bond Formation from a Phosphinoborane: Synthesis of a Bis-sigma Borane Aryl-Ruthenium Complex, Cassen, A.; Vendier, L.; Daran, J.-C.; Poblador-Bahamonde, A.; Clot, E.; Alcaraz, G.; Sabo-Etienne, S., Organometallics, submitted, ID: om-2014-00972f.

The project we wish to develop is at a fundamental level. It is entitled "Remote B-H activation in unconventional multidentate boranes" and deals with the design, the characterization and the use of organometallics complexes integrating L~BHR polyfunctional ligands in their coordination sphere.
Polyfunctional ligands are of major interest in organometallic chemistry and catalysis. They carry on functional groups and thus cannot be considered anymore as spectator ligands just providing stabilization through chelation. Polyfunctional borane ligands L~BHR are scarce and one example comes from a preliminary work performed recently in our group. They possess a well defined architecture integrating a chelating L group, a spacer and a remote borane function displaying a Bsp2-H bond.
We will first focus on the synthesis of a variety of L~BHR compounds. We will then study their coordinating ability to metallic fragments, paying a particular attention to the interaction between the B-H bond and the metal. The remote influence of the L part of the ligand on the level of the B-H activation upon coordination will be carefully examined. By using various strategies we will force the agostic sigma-borane coordination mode. The aim of our approach is to rationalize for a given metal the relation between the structure of the ligand and the reactivity of the B-H bond since it plays a crucial role in a number of transition metal catalyzed reactions such as borylation of arenes and alcanes or amine-borane dehydrogenation processes. We will evaluate the agostic sigma-borane coordination mode via the B-H bond hemilability and its direct impact on catalytic borylation and tandem amine-borane dehydrogenation/nitrile hydrogenation model reactions. The data-mining will be strongly assisted by theoretical calculations for a better understanding of the catalytic processes.