Document Detail


Tuning Lewis acidity using the reactivity of "frustrated Lewis pairs": facile formation of phosphine-boranes and cationic phosphonium-boranes.
MedLine Citation:
PMID:  17664977     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
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.
Authors:
Gregory C Welch; Lourdes Cabrera; Preston A Chase; Emily Hollink; Jason D Masuda; Pingrong Wei; Douglas W Stephan
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Publication Detail:
Type:  Journal Article     Date:  2007-05-17
Journal Detail:
Title:  Dalton transactions (Cambridge, England : 2003)     Volume:  -     ISSN:  1477-9226     ISO Abbreviation:  Dalton Trans     Publication Date:  2007 Aug 
Date Detail:
Created Date:  2007-07-31     Completed Date:  2007-09-12     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101176026     Medline TA:  Dalton Trans     Country:  England    
Other Details:
Languages:  eng     Pagination:  3407-14     Citation Subset:  -    
Affiliation:
Department of Chemistry & Biochemistry, University of Windsor, Windsor, Ontario, Canada N9B3P4.
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