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Bis(phosphine)boronium salts. Synthesis, structures and coordination chemistry
Timothy A Shuttleworth1, Miguel A Huertos, Indrek Pernik
1Department of Chemistry, University of Oxford, Oxford, United Kingdom, OX1 3TA. andrew.weller@chem.ox.ac.uk.
Dalton Transactions (Cambridge, England : 2003)
|May 30, 2013
Summary
Researchers synthesized bis(phosphine)boronium salts and explored their hydrogen bonding. These salts react with rhodium complexes, forming novel ligands and offering insights into catalytic dehydrocoupling reactions.
Area of Science:
- Organometallic Chemistry
- Coordination Chemistry
- Catalysis
Background:
- Bis(phosphine)boronium salts represent a class of compounds with potential applications in catalysis.
- Understanding the interactions within these salts, particularly hydrogen bonding, is crucial for their reactivity.
- Rhodium complexes are widely used catalysts, and their interaction with phosphine-based ligands is of significant interest.
Purpose of the Study:
- To synthesize and characterize a range of bis(phosphine)boronium salts with varying phosphine substituents and counter anions.
- To investigate the hydrogen bonding interactions present in these salts in both solid-state and solution.
- To explore the reactivity of these boronium salts with rhodium complexes and to characterize the resulting organometallic compounds.
Main Methods:
- Synthesis of bis(phosphine)boronium salts [(R2HP)2BH2][X] with R = Ph, (t)Bu, Cy and X = Br, [OTf], [BAr(F)4].
- Solid-state characterization using X-ray diffraction.
- Solution characterization using NMR spectroscopy.
- Reactions with rhodium complexes (RhH(PPh3)3 and [Rh(P(i)Bu3)2(PPh3)][BAr(F)4]) followed by characterization (X-ray crystallography).
Main Results:
- Successful synthesis of diverse bis(phosphine)boronium salts.
- Evidence of weak hydrogen bonding between the boronium cation and various anions, with strength varying based on the anion.
- Formation of novel rhodium-phosphine-borane complexes through reactions with the synthesized salts, showcasing β-B-agostic interactions.
- Direct assembly of phosphino-borane ligands on rhodium centers.
Conclusions:
- Bis(phosphine)boronium salts can engage in significant hydrogen bonding interactions, influencing their properties.
- These salts serve as precursors to unique ligands that can coordinate to rhodium centers.
- The observed reactivity provides mechanistic insights into rhodium-catalyzed dehydrocoupling reactions of phosphine boranes.
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