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Home > Research Groups > Organometallics for Optics

Topic 3: Organic / organometallic boron chemistry and BN bond engineering

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Dr Gilles Alcaraz

Borylation reactions and catalyzed C-B bond creation

This work represents the beginning of the aminoboranes chemistry developed so far in Rennes. It addresses the issues related to the monomeric nature of some aminoboranes vs an associated form or polymers, the B-H activation process mediated by a transition metal complex, the chemical hydrogen storage involving amine-boranes compounds as dihydrogen source and the synthetic interest of arylaminoboranes as valuable chemical intermediate for organic synthesis and materials such as octupolar boroxines.

Chem. Comm. (2003) 2280–2281; FR Patent 2833957 issued Jun 27, 2003 ; Chem. Comm. (2003) 2766-2767

B-H activation

The B-H activation process mediated by a transition metal complex has been studied in Toulouse by implementing a strategy based on the use of monobustituted boranes or boranes precursors as well as amine-boranes (R2NH-BH3) and also polyfunctional amino boranes (L BHNR2).

  • This approach depicted in my relocation project gave rise to the isolation of intermediates with the borane in the first coordination sphere of the metal: they are snapshots in the more or less advanced oxidative addition/reductive elimination pathway of the metal in the B-H bond that illustrate several activation levels of this bond from a monosubstituted borane to the corresponding borylene.

J. Am. Chem. Soc. (2007) 129, 8704; Inorg. Chem. (2011) 50, 11039; J. Am. Chem. Soc. (2008) 130, 12878; Organometallics (2013) 32, 4868

  • Agostic σ-B-H and bis agosticσ-B-H/σ-C-H complexes: the coordination mode is depending on the nature of the phosphino aminoborane ligand and particularly on the nature of the linker between the B and P atoms of the ligand.

(Angew. Chem., Int. Ed. (2009) 48, 2964; J. Am. Chem. Soc. (2011) 133, 17232; Angew. Chem. Int. Ed. (2014) 53, 7569; Organometallics (2014) 33, 7157).

Chemical hydrogen storage materials

With covalently bond hydrogen, amine-boranes belong to the chemical hydrogen storage materials likely to release dihydrogen. The dehydrogenation process can be accomplished in the presence of a transition metal complex and we showed the reaction can be performed under stoichiometric or catalytic conditions, depending on the amine-borane precursor. The mechanism of the reaction is closely connected to the B-H activation process presented in the previous section.

Angew. Chem., Int. Ed. (2010) 49, 918; Angew. Chem. Int. Ed. (2010) 49, 7170; Angew. Chem. Int. Ed. (2012) 51, 3646; Chem. Eur. J. (2015) 13080

Lines of investigation

The research is based upon organic and organometallic boron chemistry and thrives on acquired knowledge, in particular in the field of the B-N bond engineering for the synthesis of molecules and complexes for optics including photochromism, extended pi-conjugated hetero-aromatic systems and polyaminoboranes chemistry as model materials for hydrogen storage.

Collaborations

  • Chiara Dinoi and Iker Del Rosal (University of Toulouse): Theoretical calculations
  • Yannick Arlot and Alain Fautrel (University of Rennes): Raman labelling of biological material
  • Mary Grellier (Université de Toulouse): B-H activation (ANR Franco-Mexicaine N2CDFun- Project leader)

Selected recent publications

  • B-H, C-H, and B-C Bond Activation: the Role of Two Adjacent Agostic Interactions
    A. Cassen, Y. Gloaguen, L. Vendier, C. Duhayon, A. Poblador-Bahamonde, C. Raynaud, E. Clot, G. Alcaraz*, S. Sabo-Etienne*,
    Angew. Chem. Int. Ed. (2014) 53, 7569-7573
  • B-C Bond Cleavage and Ru-C Bond Formation from a Phosphinoborane: Synthesis of a Bis-σ Borane Aryl-Ruthenium Complex
    A. Cassen, L. Vendier, J.-C. Daran, A. I. Poblador-Bahamonde, E. Clot, G. Alcaraz,* S. Sabo-Etienne
    Organometallics (2014) 33, 7157-7163
  • A Highly Effective Ruthenium System for the Catalyzed Dehydrogenative Cyclization (CDC) of Amine-Boranes to Cyclic Boranes Under Mild Conditions
    C. W. Wallis, G. Alcaraz,*, A. S. Petit, A. I. Poblador-BVahamonde, E. Clot, C. Bijani, L. Vendier, S. Sabo-Etienne
    Chem. Eur. J. (2015) 13080-13090

Publications referenced in HAL