Fluoride Ion Chelation By a Bidentate Phosphonium/Borane Lewis Acid

The phosphonium borane [1-Mes2B-2-MePh2P-(C6H4)]+ ([2]+) has been synthesized as an iodide salt by alkylation of 1-Mes2B-2-Ph2P-(C6H4) with MeI. This novel cationic borane complexes fluoride to afford the corresponding zwitterionic fluoroborate complex 1-FMes2B-2-MePh2P-(C6H4) (2-F) with a binding c...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2008-08, Vol.130 (33), p.10890-10891
Main Authors: Hudnall, Todd W, Kim, Young-Min, Bebbington, Magnus W. P, Bourissou, Didier, Gabbaï, François P
Format: Article
Language:English
Subjects:
Acids - chemistry
Boranes - chemistry
Chelating Agents - chemistry
Chemical Sciences
Crystallography, X-Ray
Fluorides - chemistry
Ions - chemistry
Models, Chemical
Models, Molecular
Molecular Structure
Organic chemistry
Organophosphorus Compounds - chemistry
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Summary:The phosphonium borane [1-Mes2B-2-MePh2P-(C6H4)]+ ([2]+) has been synthesized as an iodide salt by alkylation of 1-Mes2B-2-Ph2P-(C6H4) with MeI. This novel cationic borane complexes fluoride to afford the corresponding zwitterionic fluoroborate complex 1-FMes2B-2-MePh2P-(C6H4) (2-F) with a binding constant in MeOH exceeding that of 1-Mes2B-4-MePh2P-(C6H4) ([1]+) by at least 4 orders of magnitude. Structural and computational results indicate that the high fluorophilicity of [2]+ arises from both Coulombic and cooperative effects which lead to formation of a B−F→P interaction with a F→P distance of 2.666(2) Å. These results, which are supported by NBO and AIM analyses, show that the latent phosphorus-centered Lewis acidity of the phosphonium moiety in [2]+ can be exploited to enhance fluoride binding via chelation.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja804492y