4762 Organometallics 2010, 29, 4762–4765
DOI: 10.1021/om1005337
Anion Recognition by Highly Sterically Encumbered
1,2-Diborylferrocenes§
Ian R. Morgan,†,‡ Alexander E. J. Broomsgrove,† Philip Fitzpatrick,† Dragoslav Vidovic,†
Amber L. Thompson,† Ian A. Fallis,‡ and Simon Aldridge*,†
†Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford,
South Parks Road, Oxford, U.K., OX1 3QR, and School of Chemistry, Cardiff University,
‡
Main Building, Park Place, Cardiff, U.K., CF10 3AT
Received May 30, 2010
Summary: The syntheses and structural characterization of
sterically encumbered 1,2-diborylferrocenes are reported, together
with an investigation of their anion recognition capabilities with
respect to fluoride and cyanide. Surprisingly, 1,2-fc(BMes2)2 is
found to be highly selective for CN-, with the uptake of F-
being shown to be not only thermodynamically less favorable
but also kinetically much slower.
cyanide for three-coordinate boranes has been known for
more than 45 years;4 recent studies have demonstrated the
use of Lewis acid receptors containing the -BMes2 (Mes =
2,4,6-Me3C6H2) function to detect cyanide,5 in one case
offering selective binding in aqueous media.5d In this respect,
a major challenge in sensor design stems from the potential
for competitive binding of fluoride at BMes2-derived recep-
tors.6 Recent reports, for example, emphasize the importance
not only of electronic factors (i.e., borane Lewis acidity) but
also of steric factors in determining the relative binding
affinities for cyanide and fluoride.5d In this respect, the use
of the proton affinities (or even the pKas) of F-/CN- in a
predictive capacity is fraught with difficulty, as reflected by
The selective detection of CN- and F- constitute signifi-
cant chemical challenges both from a supramolecular view-
point and from the perspective of potential applications in
environmental and medical monitoring.1-3 The affinity of
§ Part of the Dietmar Seyferth Festschrift.
*Contact details for corresponding author. Tel: 44 (0)1865 285201.
Fax: þ44 (0)1865 272690. E-mail: simon.aldridge@chem.ox.ac.uk.
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Published on Web 08/12/2010
2010 American Chemical Society