DOI: 10.1002/chem.201500177
Communication
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Cavitands |Hot Paper|
Cracking Cavitands: Metal-Directed Scission of Phosphinyl-
Substituted Resorcinarenes
Thierry Chavagnan,[a] David Sꢀmeril,*[a] Dominique Matt,*[a] Jack Harrowfield,[b] and
Lo¨ıc Toupet[c]
oxygen atoms which could enable the formation of highly
Abstract: Resorcinarene-derived tetramethylene cavitands
crowded P,O-chelate complexes, we considered that this might
bearing a diphenylphosphino group grafted to their wider
influence the strain within the cavity core and possibly modify
rim undergo facile, directed CꢀO bond breaking upon re-
the cavitand structure. In the present report we show that,
action with transition-metal ions in the presence of nucle-
under conditions that lead to the formation of P,O-chelate
ophiles. One possible reaction mechanism involves forma-
complexes, cavitand 1 readily undergoes selective breaking of
tion of a P,O-chelate complex, which weakens the adjacent
a specific CꢀO bond of the resorcinarene skeleton.
OꢀCH2 bond, leading to the formation of an oxacarbeni-
Reaction at room temperature of 1 with [Ru(p-cymene)Cl2]2
um intermediate.
in wet CH2Cl2 resulted after cleavage of a CꢀO bond and loss
of a methylene group nearly quantitatively in chelate complex
2 (Scheme 1, top). Consistent with a “cracked cavitand” struc-
Resorcinarenes that have been made conformationally rigid by
placing methylene linkers between all pairs of neighbouring
hydroxy oxygen atoms constitute an important class of bowl-
shaped molecules (cavitands) widely used as building blocks
for applications in host-guest chemistry, coordination chemis-
try, homogeneous catalysis and materials science.[1] The scaf-
fold of such cavitands is regarded as extremely robust, with
a wide variety of reactions aimed at the introduction of func-
tional groups at the periphery leaving the container structure
unaffected.[2] Thus, whereas partially bridged cavitands have
been prepared in one-step procedures from generic resorcinar-
ene skeletons, core modification/breaking of a tetramethylene
cavitand scaffold has not been reported.[3]
We have recently reported the synthesis of cavitand 1,
having a diphenylphosphino group grafted to its wider rim.[4]
Figure 1. Molecular structure of complexes 2 (left) and 3 (right). Cavitand 2
contains an entrapped CH2Cl2 molecule, which has been omitted for clarity.
The capacity of 1 to behave as a bulky, P-monodentate ligand
was demonstrated in the synthesis of several PdII complexes.
As the phosphino-aryl moiety of 1 is flanked by two ether
The unit cells also contain the mirror images of the molecules shown.
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ture, the corresponding H NMR spectrum showed only three
distinct AB patterns arising from OCH2 groups as well as a sin-
glet at 9.34 ppm typical of a phenolic OH proton. The structure
of 2 was confirmed by an X-ray diffraction study (Figure 1),
which also revealed that the Ru-(p-cymene) bond is turned
away from the cavity wall, thus minimising the steric interac-
tions of the “Ru(arene)Cl” unit with the cavitand core. Consis-
tent with the expected strain release induced by the crack, the
separation between the O(Ru) and O(H) atoms is 0.25 ꢁ longer
than that between methylene-bridged O atoms (mean 2.36 ꢁ).
The related palladium complex 3 was obtained by chloride ab-
straction from [Pd(o-C6H4CH2NMe2)Cl·1][4] with NH4PF6/H2O
(Scheme 1, bottom and Figure 1). Repeating the reaction lead-
ing to 2 under rigorously dry conditions produced 4, which
unlike 2, contains four (distinct) OCH2 groups and no hydroxyl
group (Scheme 2). The presence of a pendent OCH2Cl group
was inferred from the 13C NMR spectrum of 4, which showed
[a] T. Chavagnan, Dr. D. Sꢀmeril, Dr. D. Matt
Laboratoire de Chimie Inorganique Molꢀculaire et Catalyse
Institut de Chimie UMR 7177 CNRS-Universitꢀ de Strasbourg
4 rue Blaise Pascal
67070 Strasbourg cedex (France)
[b] Dr. J. Harrowfield
Institut de Science et Ingꢀnierie Supramolꢀculaires (ISIS)
UMR 7606 CNRS-Universitꢀ de Strasbourg
8 rue Gaspard Monge
67083 Strasbourg cedex (France)
[c] Dr. L. Toupet
Institut de Physique de Rennes
UMR 6251 CNRS-Universitꢀ de Rennes
Campus de Beaulieu - Bꢁtiment 11A
35042 Rennes cedex (France)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201500177.
Chem. Eur. J. 2015, 21, 1 – 5
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ꢂ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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