Self-Assembly of Coordination Polymers from Tetraphosphinitoresorcinarene Complexes of Silver(I) Dana J. Eisler and Richard J. Puddephatt* Department of Chemistry, University of Western Ontario, London, Canada, N6A 5B7
CRYSTAL GROWTH & DESIGN 2005 VOL. 5, NO. 1 57-59
Received October 30, 2003
ABSTRACT: The first hybrid organic-inorganic polymers based on the resorcinarene skeleton are prepared and structurally characterized. Two tetrasilver(I) complexes of a tetraphosphinitoresorcinarene are shown to undergo selfassembly to form a side-by-side or face-to-face polymer depending on the nature of the anion. There have been major advances recently in the synthesis of complex structures, including polymers, two-dimensional sheet structures, helices, and cage complexes, through the use of dynamic coordination chemistry.1-3 Polymeric networks of calixarenes and resorcinarenes, which contain a natural cavity, are particularly interesting because they can act as size and shape selective hosts leading to potential applications as functional materials. Although several beautiful coordination polymers of calixarenes have been reported, no similar well-defined derivatives of resorcinarenes are known.2 We report the first such coordination polymers, formed by using tetraphosphinitoresorcinarene complexes of silver(I) as building blocks.4 Silver(I) is particularly useful in the self-assembly of complex structures since it is a labile metal center with versatile coordination properties. Thus, it commonly adopts coordination numbers of 2-4 in covalent complexes and with the potential for higher coordination numbers in more ionic compounds.5,6 The tetraphosphinitoresorcinarene ligand 1 (Chart 1) forms cluster complexes with silver halides such as 2 and 3 (X ) halide).4 In the cluster complexes, the resorcinarene skeleton adopts a boat conformation in which the arene groups bearing the diphenylphosphinite substituents are upright, as needed to allow transannular bridging.4 The reactions of 1 with silver(I) trifluoroacetate or triflate were significantly different from the reactions of 1 with silver(I) halides, and led to formation of the first resorcinarene coordination polymers. As monitored by 31P NMR, these reactions gave well-defined complexes of stoichiometry 1(AgX)n with n ) 1, 2, or 4. For example, when X ) CF3SO3, these complexes were characterized by the parameters δ(P) ) 113.1, 1J(109AgP) ) 309 Hz, n ) 1; δ(P) ) 105.3, 1J(109AgP) ) 604 Hz, n ) 2; δ(P) ) 116.4, 1J(109AgP) ) 914 Hz, n ) 4, consistent with effective AgP4, AgP2, and AgP coordination, respectively. The complexes all exist in solution with the resorcinarene skeleton in the boat conformation, as determined by analysis of the 1H, 13C, and 31P NMR spectra.4 The phosphinite-derivatized arene groups are upright when n ) 1 or 2, as in the known complexes 2 and 3 (Chart 1). However, when n ) 4 these arene groups are in the flattened position, which is more suited to polymer formation. The NMR spectra are consistent with the molecular structure 4 (Chart 1), with X ) CF3CO2 or CF3SO3, but the spectra are not definitive since the oxygendonor ligands are particularly labile and can bridge in more than one way. Thus, the detailed structures of the complexes with n ) 4 were determined crystallographically.7 The trifluoroacetate derivative was characterized as [1{Ag2(µ-O2CCF3)2}2], 5 (Chart 2), as a chloroform solvate, * To whom correspondence should be addressed. E-mail:
[email protected]. Fax: (519) 661-3022.
Figure 1. Views of the structure of complex 5. Left, the molecular structure and, right, the side-by-side association between molecules via the bridging trifluoroacetate ions that leads to formation of the polymer by forming Ag(2)2O(4)2 rings. Phenyl groups, and substituents R ) C(O)CH2Ph and R′ ) CH2CH2Ph (Charts 1 and 2) are omitted for clarity.
and the structure is shown in Figure 1. The molecular structure is based on a resorcinarene skeleton with the opposite arene groups containing the ester groups upright (fold angle between these rings ) 5°) and those with the diphenylphosphinite substituents flattened (fold angle 152°), as predicted by the NMR studies. Each silver(I) center binds to a diphenylphosphinite group and to two O,O′-bridging trifluoroacetate ligands. The two disilver units are equivalent since a C2-axis passes through the center of the boat structure. The Ag‚‚‚Ag separation within each disilver unit of 3.214(1) Å could indicate a weak secondary bonding interaction.8 The molecules of complex 5 self-assemble to give polymers by formation of pairwise intermolecular bonds involving the silver atom Ag(2) and an oxygen atom O(4) of a trifluoroacetate group as shown in Figure 1. The fourmembered Ag2O2 ring that results is therefore connected by the bonds Ag(2)-O(4A) ) Ag(2A)-O(4) ) 2.568(4) Å, and since each molecule contains two Ag(2) centers replication naturally gives a polymeric structure. There is a center of symmetry at the center of each Ag2O2 ring, so that the upright arene rings with ester substituents are oriented in opposite directions in neighboring molecules. The µ3-η2 bridging mode of the trifluoroacetate group in complex 5 has been observed previously in the complex [Ag2(µ-O2CCF3)2(µ-cis-Ph2PCHdCHPPh2)], but since there is only one pair of silver atoms in this complex the association leads only to dimer formation.5b The side-by-side associa-
10.1021/cg034203l CCC: $30.25 © 2005 American Chemical Society Published on Web 08/11/2004
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Communications Chart 1.a
a
P ) PPh2, R ) C(O)OCH2Ph, R′ ) CH2CH2Ph.
Chart 2.a
a
P ) PPh2, R ) C(O)OCH2Ph, R′ ) CH2CH2Ph.
tion of the molecules in complex 5 is a striking structural feature and leaves the resorcinarene cavity open (Figure 1). The triflate complex was characterized as the aqua complex [1{Ag2(µ-O3SCF3)2}{Ag2(OH2)2(µ-OH2)}(µ-O3SCF3)]CF3SO3, 6 (Chart 2), as a chloroform solvate, and the structure is shown in Figure 2a. Two of the silver centers, Ag(3) and Ag(4), are coordinated to a single phosphorus atom, and are bridged by two triflate anions, giving a local structure similar to that in complex 5. However, the silver centers Ag(1) and Ag(2) are each coordinated to a phosphorus atom, and to oxygen atoms of a terminal and a bridging water molecule. In addition, there is a triflate anion that forms an intermolecular bridge by binding to both Ag(4) [Ag(4)-O(17) ) 2.319(5) Å] and, more weakly, to Ag(1A) [Ag(1A)-O(18) ) 2.600(5) Å]. The Ag‚‚‚Ag distances Ag(1)Ag(2) ) 3.46 Å and Ag(3)Ag(4) ) 4.18 Å are longer than in complex 5. The intermolecular triflate bridging leads to formation of a polymer as illustrated in Figure 2. However, instead of the side-by-side association found for complex 5, the association occurs in a face-to-face manner (Figure 2). The association is strongly reinforced by hydrogen bonding between aqua and triflate ligands that is not shown in Figure 2. In particular, the bridging aqua ligand hydrogen bonds to both of the triflate ligands that bridge the Ag(3)Ag(4) units of the neighboring molecule [O(34)‚‚‚O(26A) )
Figure 2. Views of the structure of complex 6. Left, the molecular structure showing the triflate that bridges intermolecularly twice and, right, the association between molecules via the bridging triflate that leads to formation of the face-to-face polymer. Phenyl groups, and substituents R ) C(O)CH2Ph and R′ ) CH2CH2Ph (Charts 1 and 2) are omitted for clarity.
2.754(7) Å, O(34)‚‚‚O31(A) ) 2.812 (6) Å], and the triflate that bridges intermolecularly between Ag(1) and Ag(4A) also hydrogen bonds to a terminal aqua ligand [O(33)‚‚‚ O(19A) ) 2.710(7) Å]. The ionic triflate ion hydrogen bonds to both terminal aqua ligands [O(32)‚‚‚O(21) ) 2.81(1) Å, O(33)‚‚‚O(22) ) 2.75(1) Å]. In conclusion, reaction of the tetraphosphinitoresorcinarene ligand 1 with silver trifluoroacetate or triflate forms the tetrasilver(I) complexes 5 and 6, which undergo
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self-assembly in the solid state to form the first supramolecular polymers based on the bowl-shaped resorcinarene architecture. Furthermore, two very distinct forms of selfassembly are established and identified as side-by-side in 5 and face-to-face in 6. The difference appears to arise from the weaker binding of triflate in 6 compared to trifluoroacetate in 5. Displacement of some triflate ions by aqua ligands leads to a different form of self-assembly in 6, involving extensive hydrogen bonding as well as the secondary Ag‚‚‚O bonds, which are present in both 5 and 6.
(3)
(4)
(5)
Acknowledgment. We thank the NSERC (Canada) for funding. R.J.P. thanks the Government of Canada for a Canada Research Chair. Supporting Information Available: X-ray data in CIF format are available free of charge via the Internet at http:// pubs.acs.org.
References (1) (a) Batten, S. R.; Robson, R. Angew. Chem., Int. Ed. Engl. 1998, 37, 1460. (b) Pan, L.; Woodlock, E. B.; Wang, X.; Lam, K.-C.; Rheingold, A. Chem. Commun. 2001, 1762. (c) Brooks, N. R.; Blake, A. J.; Champness, N. R.; Cunningham, J. W.; Hubberstey, P.; Schro¨der, M. Cryst. Growth Des. 2001, 1, 395. (d) Ino, I.; Zhong, J. C.; Munakata, M.; Kuroda-Sowa, T.; Maekawa, M.; Suenaga, Y.; Kitamori, Y. Inorg. Chem. 2000, 39, 4273. (e) Sun, D.; Cao, R.; Sun, Y.; Bi, W.; Li, X.; Wang, Y.; Shi, O.; Li, X. Inorg. Chem. 2003, 42; 7512-7518. (2) (a) Mislin, G.; Graf, E.; Hosseini, M. W.; De Cian, A.; Kyritsakas, N.; Fischer, J. Chem. Commun. 1998, 2545. (b) Webb, H. R.; Hardie, M. J.; Raston, C. L.; Chem. Eur. J. 2001, 7, 3616. (c) Pirondini, L.; Bonifazi, D.; Menozzi, E.;
(6)
(7)
(8)
Wegelius, E.; Rissanen, K.; Massera, C.; Dalcanale, E. Eur. J. Org. Chem. 2001, 2311. (a) Bibal, B.; Tinant, B.; Declercq, J.-P.; Dutasta, J.-P. Chem. Commun. 2002, 432. (b) Harrison, R. G.; Fox, O. D.; Meng, M. O.; Dalley, N. K.; Barbour, L. J. Inorg. Chem. 2002, 41, 838. (c) Park, S. J.; Hong, J.-I. Chem. Commun. 2001, 1554. (d) Fox, O. D.; Drew, M. G. B.; Wilkinson, E. J. S.; Beer, P. D. Chem. Commun. 2000, 391. (a) Eisler, D. J.; Puddephatt, R. J. Can. J. Chem., 2004, 82, 185. (b) Eisler, D. J.; Kirby, C. W.; Puddephatt, R. J. Inorg. Chem. 2003, 42, 7626-7634. (c) Eisler, D. J.; Puddephatt, R. J. Inorg Chem. 2003, 42, 8192-8202. (a) Che, C.-M.; Tse, M.-C.; Chan, M. C. W.; Cheung, K.-K.; Phillips, D. L.; Leung, K.-H. J. Am. Chem. Soc. 2000, 122, 2464. (b) Brandys, M.-C.; Puddephatt, R. J. J. Am. Chem. Soc. 2002, 124, 3946. (c) Powell, J.; Horvath, M. J.; Lough, A.; Phillips, A.; Brunter, J. J. Chem. Soc., Dalton Trans. 1998, 637. (a) Lozano, E.; Nieuwenhuyzen, M.; James, S. L. Chem. Eur. J. 2001, 7, 2644. (b) Wang, Q.-M.; Mak, T. C. W. J. Am. Chem. Soc. 2000, 122, 7608. (c) Kuang, S.-M.; Zhang, Z.-Z.; Wang, Q.-G.; Mak, T. C. W. Inorg. Chem. 1998, 37, 6090. Xray data: 5.2.2CHCl3, C150.2H118.2Ag4Cl6.6F12O24P4, fw ) 3324.38, space group C2/c, a ) 34.9491(3), b ) 17.4843(2), c ) 24.7004(3) Å, β ) 98.497(1) °, V ) 14927.8(3) Å3, Z ) 4, dcalc ) 1.479 mg/m3, µ(Mo KR) ) 0.760 mm-1, R1, wR2 [I > 2σ(I)] ) 0.0791, 0.2213. 6‚2CH2Cl2‚n-C6H14, C152H140Ag4Cl4F12O31P4S4, fw ) 3516.04, space group P21/n, a ) 24.2596(1), b ) 23.8932(1), c ) 26.6121(2) Å, β ) 92.363(1)°, V ) 15412.3(2) Å3, Z ) 4, dcalc ) 1.515 mg/m3, µ(Mo KR) ) 0.734 mm-1, R1, wR2 [I > 2σ(I)] ) 0.0690, 0.1873. (a) Brandys, M.-C.; Puddephatt, R. J. Chem. Commun. 2001, 1508. (b) Deivaraj, T. C.; Vittal, J. J. J. Chem. Soc., Dalton Trans. 2001, 329.
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