| Tuning Lewis acidity using the reactivity of "frustrated Lewis pairs": facile formation of phosphine-boranes and cationic phosphonium-boranes. | |
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MedLine Citation:
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PMID: 17664977 Owner: NLM Status: PubMed-not-MEDLINE |
Abstract/OtherAbstract:
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The concept of "frustrated Lewis pairs" involves donor and acceptor sites in which steric congestion precludes Lewis acid-base adduct formation. In the case of sterically demanding phosphines and boranes, this lack of self-quenching prompts nucleophilic attack at a carbon para to B followed by fluoride transfer affording zwitterionic phosphonium borates [R(3)P(C(6)F(4))BF(C(6)F(5))(2)] and [R(2)PH(C(6)F(4))BF(C(6)F(5))(2)]. These can be easily transformed into the cationic phosphonium-boranes [R(3)P(C(6)F(4))B(C(6)F(5))(2)](+) and [R(2)PH(C(6)F(4))B(C(6)F(5))(2)](+) or into the neutral phosphino-boranes R(2)P(C(6)F(4))B(C(6)F(5))(2). This new reactivity provides a modular route to a family of boranes in which the steric features about the Lewis acidic center remains constant and yet the variation in substitution provides a facile avenue for the tuning of the Lewis acidity. Employing the Gutmann-Beckett and Childs methods for determining Lewis acid strength, it is demonstrated that the cationic boranes are much more Lewis acidic than B(C(6)F(5))(3), while the acidity of the phosphine-boranes is diminished. |
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Authors:
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Gregory C Welch; Lourdes Cabrera; Preston A Chase; Emily Hollink; Jason D Masuda; Pingrong Wei; Douglas W Stephan |
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Publication Detail:
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Type: Journal Article Date: 2007-05-17 |
Journal Detail:
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Title: Dalton transactions (Cambridge, England : 2003) Volume: - ISSN: 1477-9226 ISO Abbreviation: Dalton Trans Publication Date: 2007 Aug |
Date Detail:
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Created Date: 2007-07-31 Completed Date: 2007-09-12 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 101176026 Medline TA: Dalton Trans Country: England |
Other Details:
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Languages: eng Pagination: 3407-14 Citation Subset: - |
Affiliation:
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Department of Chemistry & Biochemistry, University of Windsor, Windsor, Ontario, Canada N9B3P4. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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