Inorg. Chem. 2010, 49, 8247–8254 8247 DOI: 10.1021/ic100530h
Intercluster Compound between a Tetrakis{triphenylphosphinegold(I)}oxonium Cation and a Keggin Polyoxometalate (POM): Formation during the Course of Carboxylate Elimination of a Monomeric Triphenylphosphinegold(I) Carboxylate in the Presence of POMs Kenji Nomiya,* Takuya Yoshida, Yoshitaka Sakai, Arisa Nanba, and Shinichiro Tsuruta Department of Materials Science, Faculty of Science, Kanagawa University, Hiratsuka, Kanagawa 259-1293, Japan Received March 20, 2010
The preparation and structural characterization of a novel intercluster compound, [{Au(PPh 3 )}4 (μ4 -O)]3 [R-PW12O40]2 3 4EtOH (1), constructed between a tetrakis{triphenylphosphinegold(I)}oxonium cation and a saturated R-Keggin polyoxometalate (POM) are described. The tetragold(I) cluster oxonium cation was formed during the course of carboxylate elimination of a monomeric phosphinegold(I) carboxylate complex, i.e., [Au((R,S)-pyrrld)(PPh3)] [(R,S)-Hpyrrld = (R,S)-2-pyrrolidone-5-carboxylic acid], in the presence of the free acid form of a Keggin POM, H3[R-PW12O40] 3 7H2O. The liquid-liquid diffusion between the upper water/EtOH phase containing the Keggin POM and the lower CH2Cl2 phase containing the monomeric gold(I) complex gave a pure crystalline sample of 1 in good yield (42.1%, 0.242 g scale). Complex 1 was formed by ionic interaction between the tetragold(I) cluster cation and the Keggin POM anion. As a matter of fact, the POM anion in 1 can be exchanged with the BF4- anion using an anion-exchange resin (Amberlyst A-27) in BF4- form. By using other Keggin POMs, such as H4[R-SiW12O40] 3 10H2O and H 3 [R-PMo 12 O 40] 3 14H 2 O, the same tetragold(I) cluster cation was also formed, i.e., in the forms of [{Au(PPh3)}4(μ4-O)]2[R-SiW12O40] 3 2H2O (2) and [{Au(PPh3)}4(μ4-O)]3[R-PMo12O40]2 3 3EtOH (3). Compounds 1-3, as dimethyl sulfoxide-soluble, EtOH- and Et2O-insoluble dark-yellowish white solids, were characterized by complete elemental analysis, thermogravimetric and differential thermal analyses, Fourier transform IR, X-ray crystallography, and solid-state (CPMAS 31P and 29Si) and solution (31P{1H} and 1H) NMR spectroscopy. The molecular structures of 1 and 2 were successfully determined. The tetragold(I) cluster cation was composed of four PPh3AuI units bridged by a central μ4-oxygen atom in the geometry of a trigonal pyramid or distorted tetrahedron.
Introduction Polyoxometalates (POMs) are discrete metal oxide clusters that are of current interest as soluble metal oxides and for their application in catalysis, medicine, and materials science.1 The preparation of POM-based materials is therefore an active field of research. Some of the intriguing aspects are that a combination of POMs with cluster cations or macrocations has resulted in the formation of various interesting intercluster compounds, from the viewpoints of ionic crystals, crystal growth, crystal engineering, structure and sorption properties, and so on.2-5 In many compounds, the POMs have been combined with separately prepared Ag/Au cluster cations.2-4 For example, depending upon the types of solvents and concentrations, two types of crystals of [Au9(PPh3)8][PW12O40] have been obtained as orange needles of a first *To whom correspondence should be addressed. E-mail: nomiya@ kanagawa-u.ac.jp.
r 2010 American Chemical Society
compound and as greenish-black plates or prisms of a second compound. Both compounds contain [Au9(PPh3)8]3þ and [R-PW12O40]3- in a 1:1 ratio but exhibit different Au9 skeletal isomers and packing types, i.e., NaCl and CsCl types.2a The crystal structure of the supramolecular intercluster compound [Au9(PPh3)8]2[V10O28H3]2 is dominated by shortrange bonding interactions, i.e., hydrogen bonds, and C-H/π interactions, avoiding simple AB packing.2b Intercluster compounds,2c such as [Au9(dpph)4][Mo8O26] [dpph= 1,6-bis(diphenylphosphino)hexane], [Au9(dpph)4][PW12O40], and [Au11(PPh3)8Cl2]2[W6O19], have recently been reported. An Ag/1,2,4-triazole/POMs hybrid supramolecular family3 has also been reported by Chinese workers and contains [Ag4(dmtrz)4][Mo8O26] (dmtrz = 3,5-dimethyl-1,2,4-triazole), [Ag6(3atrz)6][PMo12O40]2 3 H2O (3atrz = 3-amino-1,2,4-trizaole), [Ag2(3atrz)2]2[HPMoVI10MoV2O40], [Ag2(dmtrz)2]2[HPMoVI10MoV2O40], [Ag2(trz)2]2[Mo8O26] (trz = 1,2,4-triazole), [Ag2(3atrz)2][Ag2(3atrz)2(Mo8O26)], [Ag4(4atrz)2Cl][Ag(Mo8O26)] Published on Web 08/24/2010
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8248 Inorganic Chemistry, Vol. 49, No. 18, 2010 (4atrz = 4-amino-1,2,4-triazole), and [Ag5(trz)4]2[Ag2(Mo8O26)] 3 4H2O. On the other hand, Cronin et al. have reported a silver connection with POMs, i.e., {[Ag3(dmso)6][Ag1(dmso)3][H2V10O28] 3 DMSO}n (a 1D zigzag chain) and {[Ag3(dmso)6][Ag1(dmso)2][H2V10O28] 3 2DMSO}n (a 2D network) (dmso, DMSO = dimethyl sulfoxide).4a Using silver-based linkers, POM-based 0-, 1-, 2-, and 3D frameworks have been generated, in which silver ions are ligated mainly in an oxo-based ligand environment. The same research group has reported molecular growth processes utilizing POM-based building blocks with silver connecting units, such as [Ag3(bhepH)8(W11.5Na0.5O40P)2] 3 8H2O [bhep = N,N0 -bis(2-hydroxyethyl)piperazine] (representing a 0D dimer), [Ag4(DMSO)8(Mo8O26)]n (forming 2D layered networks), and {Ag3[MnMo6O18{(OCH2)3CNH2}2(DMSO)5] 3 3DMSO}n and {Ag3[MnMo6O18{(OCH2)3CNH2}2(DMSO)6(CH3CN)2] 3 DMSO}n (forming 1D networks).4b Mizuno et al. have recently reported nanostructures and sorption properties based on a combination of macrocation [Cr3O(OOCH)6(H2O)3]þ and POMs such as [R-SiW12O40]4- and [R-CoW12O40]6- to form K3[Cr3O(OOCH)6(H2O)3][R-SiW12O40] 3 16H2O and Cs5[Cr3O(OOCH)6(H2O)3][R-CoW12O40] 3 7.5H2O.5 In this work, we unexpectedly found the formation of a novel intercluster compound, [{Au(PPh3)}4(μ4-O)]3[R-PW12O40]2 3 4EtOH (1), containing a phosphinegold(I) cluster cation, (1) (a) Pope, M. T.; M€uller, A. Angew. Chem., Int. Ed. Engl. 1991, 30, 34– 48. (b) Pope, M. T. Heteropoly- and Isopolyoxometalates; Springer-Verlag: New York, 1983. (c) Day, V. W.; Klemperer, W. G. Science 1985, 228, 533–541. (d) Hill, C. L. Chem. Rev. 1998, 98, 1–390. (e) Okuhara, T.; Mizuno, N.; Misono, M. Adv. Catal. 1996, 41, 113–252. (f) Hill, C. L.; Prosser-McCartha, C. M. Coord. Chem. Rev. 1995, 143, 407–455. (g) A series of 34 recent papers in a volume devoted to Polyoxoanions in Catalysis: Hill, C. L. J. Mol. Catal. A: Chem. 1996, 114, 1-359. (h) Neumann, R. Prog. Inorg. Chem. 1998, 47, 317– 370. (i) Polyoxometalate Chemistry from Topology via Self-Assembly to Applications; Pope, M. T., M€uller, A., Eds.; Kluwer Academic Publishers: Dordrecht, The Netherlands, 2001. (j) Polyoxometalate Chemistry for NanoComposite Design; Yamase, T., Pope, M. T., Eds.; Kluwer Academic Publishers: Dordrecht, The Netherlands, 2002. (k) Pope, M. T. Polyoxo anions: synthesis and structure. In Comprehensive Coordination Chemistry II; Wedd, A. G., Ed.; Elsevier Science: New York, 2004; Vol. 4, pp 635-678. (l) Hill, C. L. Polyoxometalates: Reactivity. In Comprehensive Coordination Chemistry II; Wedd, A. G., Ed.; Elsevier Science: New York, 2004; Vol. 4, pp 679-759. (m) A series of 32 recent papers in a volume devoted to Polyoxometalates in Catalysis: Hill, C. L. J. Mol. Catal. A: Chem. 2007, 262, 1-242. (n) Proust, A.; Thouvenot, R.; Gouzerh, P. Chem. Commun. 2008, 1837–1852. (o) Hasenknopf, B.; Micoine, K.; Lac^ote, E.; Thorimbert, S.; Malacria, M.; Thouvenot, R. Eur. J. Inorg. Chem. 2008, 5001–5013. (p) Laurencin, D.; Thouvenot, R.; Boubekeur, K.; Villain, F.; Villanneau, R.; Rohmer, M.-M.; Benard, M.; Proust, A. Organometallics 2009, 28, 3140–3151. (q) Long, D.-L.; Tsunashima, R.; Cronin, L. Angew. Chem., Int. Ed. 2010, 49, 1736–1758. (2) (a) Schulz-Dobrick, M.; Jansen, M. Eur. J. Inorg. Chem. 2006, 4498– 4502. (b) Schulz-Dobrick, M.; Jansen, M. Inorg. Chem. 2007, 46, 4380–4382. (c) Schulz-Dobrick, M.; Jansen, M. Z. Anorg. Allg. Chem. 2007, 633, 2326– 2331. (3) Zhai, Q. G.; Wu, X. Y.; Chen, S. M.; Zhao, Z. G.; Lu, C. Z. Inorg. Chem. 2007, 46, 5046–5058. (4) (a) Streb, C.; Tsunashima, R.; MacLaren, D. A.; McGlone, T.; Akutagawa, T.; Nakamura, T.; Scandurra, A.; Pignataro, B.; Gadegaard, N.; Cronin, L. Angew. Chem., Int. Ed. 2009, 48, 6490–6493. (b) Song, Y. F.; Abbas, H.; Ritchie, C.; McMillian, N.; Long, D. L.; Gadegaard, N.; Cronin, L. J. Mater. Chem. 2007, 17, 1903–1908. (5) Mizuno, N.; Uchida, S. Chem. Lett. 2006, 35, 688–693. (6) (a) Noguchi, R.; Hara, A.; Sugie, A.; Nomiya, K. Inorg. Chem. Commun. 2006, 9, 355–359. (b) Nomiya, K.; Takahashi, S.; Noguchi, R. J. Chem. Soc., Dalton Trans. 2000, 1343–1348. (c) Nomiya, K.; Takahashi, S.; Noguchi, R.; Nemoto, S.; Takayama, T.; Oda, M. Inorg. Chem. 2000, 39, 3301–3311. (d) Nomiya, K.; Takahashi, S.; Noguchi, R. J. Chem. Soc., Dalton Trans. 2000, 4369–4373. (e) The representation of H2pyrrld in refs 6a, 6c,6d is changed to Hpyrrld; thus, the formulation of [Au((R,S)-Hpyrrld)(PPh3)] used so far is also changed to [Au((R,S)-pyrrld)(PPh3)].
Nomiya et al. which was obtained by the reaction of monomeric phosphinegold(I) carboxylate, [Au((R,S)-pyrrld)(PPh3)] [(R,S)Hpyrrld = (R,S)-2-pyrrolidone-5-carboxylic acid],6a with the free acid form of a saturated Keggin POM, H3[R-PW12O40] 3 7H2O.7 The synthesis, structure, and antimicrobial activities of the monomeric phosphinegold(I) carboxylate precursor have been unequivocally investigated.6a In relation to the present compound, the field of element-centered gold clusters [E(AuL)n]mþ, for example, [E(AuPPh3)4]2þ (E = S, Se),8a-c the angular flexibility of the Au-E-Au angles,8d and the new structural findings, i.e., the tetrahedral bonding of [N(AuL)4]þ and the pyramidal bondings of [As(AuL)4]þ and [P(AuL)4]þ,8e,f has been extensively studied by the groups of Laguna8a-c and Schmidbaur.8d-f There are several crucial issues concerning 1: (1) the POM anion in 1 can be exchanged with BF4- (see the Experimental Section), suggesting that 1 is an ionic compound. (2) The BF4- salt of the {tetraphosphinegold(I)oxonium} cation [{Au(PPh3)}4(μ4-O)]2þ has usually been synthesized by a quite different method, i.e., the reaction of tris{triarylphosphinegold(I)}oxonium tetrafluoroborate [{Au(PR3)}3(μ3-O)]BF48g with 1 equiv of a freshly prepared solution of the monomeric species [Au(PR3)]BF4 (R = phenyl, o-tolyl) by Schmidbaur’s group.8h (3) On the other hand, the present reaction significantly depends upon the POMs. As a matter of fact, the [{Au(PPh3)}4(μ4-O)]2þ ion is also formed in the presence of other Keggin POMs, such as H3[R-PMo12O40] 3 14H2O and H4[R-SiW12O40] 3 10H2O7, the formulas of which have been determined as [{Au(PPh3)}4(μ4-O)]2[R-SiW12O40] 3 2H2O (2) and [{Au(PPh3)}4(μ4-O)]3[R-PMo12O40]2 3 3EtOH (3), respectively. (4) Formation of the intercluster compounds 1-3 suggests that the bulkiness and large anionic charge of the free-acid-type POMs contribute to the direct clusterization of [Au(PR3)]þ species to the tetraphosphinegold cluster oxonium cation but not via the triphosphinegold oxonium cation, after removal of the (R,S)-pyrrld- ligand. (5) Recently, several phosphinegold(I) complexes have become known as effective homogeneous catalysts for organic synthesis;9,10 for example, [{Au(PPh3)}3(μ3-O)]BF4,8g,11 has been used as an effective catalyst for a Claisen rearrangement of propargyl vinyl ethers,9,10 and such a complex has also (7) North, E. O.; Haney, W. Inorg. Synth. 1939, 1, 127. (8) (a) Canales, F.; Gimeno, M. C.; Jones, P. G.; Laguna, A. Angew. Chem., Int. Ed. 1994, 33, 769–770. (b) Canales, F.; Gimeno, C.; Laguna, A.; Villacampa, M. D. Inorg. Chim. Acta 1996, 244, 95–103. (c) Gimeno, M. C.; Laguna, A. Chem. Soc. Rev. 2008, 37, 1952–1966. (d) Schmidbaur, H.; Schier, A. Chem. Soc. Rev. 2008, 37, 1931–1951. (e) Zeller, E.; Beruda, H.; Kolb, A.; Bissinger, P.; Riede, J.; Schmidbaur, H. Nature 1991, 352, 141–143. (f) Schmidbaur, H. Z. Naturforsch., B: Chem. Sci. 2008, 63, 853–859. (g) Nesmeyanov, A. N.; Perevalova, E. G.; Struchkov, Y. T.; Antipin, M. Y.; Grandberg, K. I.; Dyadchenko, V. P. J. Organomet. Chem. 1980, 201, 343–349. (h) Schmidbaur, H.; Hofreiter, S.; Paul, M. Nature 1995, 377, 503–504. (9) (a) F€urstner, A.; Davies, P. W. Angew. Chem., Int. Ed. 2007, 46, 3410– 3449. (b) Hashmi, A. S. K. Chem. Rev. 2007, 107, 3180–3211. (c) Jimenez-Nunez, E.; Echavarren, A. M. Chem. Rev. 2008, 108, 3326–3350. (d) Gorin, D. J.; Sherry, B. D.; Toste, F. D. Chem. Rev. 2008, 108, 3351–3378. (10) (a) Mauleon, P.; Krinsky, J. L.; Toste, F. D. J. Am. Chem. Soc. 2009, 131, 4513–4520. (b) Sakaguchi, K.; Okada, T.; Shinada, T.; Ohfune, Y. Tetrahedron Lett. 2008, 49, 25–28. (11) (a) Yang, Y.; Ramamoorthy, V.; Sharp, P. R. Inorg. Chem. 1993, 32, 1946–1950. (b) Schmidbaur, H.; Kolb, A.; Zeller, E.; Schier, A.; Beruda, H. Z. Anorg. Allg. Chem. 1993, 619, 1575–1579. (c) Kuz'mina, L. G.; Churakov, A. V.; Sadikov, G. G.; Howard, J. A. K. Crystallogr. Rep. 2003, 48, 61–67. (d) Angermaier, K.; Schmidbaur, H. Inorg. Chem. 1994, 33, 2069–2071. (e) Mathieson, T.; Schier, A.; Schmidbaur, H. Z. Naturforsch., B: Chem. Sci. 2000, 55, 1000–1004.
Article
been utilized as a precursor for the synthesis of novel metal complexes.12 Herein, we report full details of the synthesis and characterization of intercluster compounds 1-3. As related compounds using similar methods, we also report the synthesis and characterization of P(o-tolyl)3 derivatives (Supporting Information), i.e., [{Au(P(o-tolyl)3)}4(μ4-O)]3[R-PW12O40]2 (4), [{Au(P(o-toyl)3)}4(μ4-O)]2[R-SiW12O40] (5), and [{Au(P(o-tolyl)3)}4(μ4-O)]3[R-PMo12O40]2 (6). Experimental Section Materials. The following reactants were used as received: H[AuCl4] 3 4H2O, EtOH, CH2Cl2, Et2O, (R,S)-5-oxo-2-tetrahydrofurancarboxylic acid [(R,S)-Hothf] (all from Wako); P(o-tolyl)3, CH2Cl2, CH3CN (all from Kanto); DMSO-d6, CDCl3, CD2Cl2 (all from Isotec); anion-exchange resin (Amberlyst A-27), PPh3 (all from Aldrich); (R,S)-2-pyrrolidone-5-carboxylic acid [(R,S)-Hpyrrld] (TCI). As for the Keggin POM precursors, H3[R-PW12O40] 3 7H2O was derived from a separately prepared sodium salt using an Hþ-form cation-exchange column, and H3[RPMo12O40] 3 14H2O and H4[R-SiW12O40] 3 10H2O were prepared according to the so-called ether-extraction method,7 all of them being identified by Fourier transform (FT) IR, thermogravimetric and differential thermal analyses (TG/DTA), and solution (31P or 29Si) NMR spectroscopy. The phosphinegold(I) carboxylate precursors, [Au((R,S)-pyrrld)(PR3)] (R = Ph, o-tolyl) and [Au((R,S)-othf)(PPh3)], have been synthesized according to the literature6 or its modification and identified by CHN elemental analysis, FTIR, TG/DTA, and solution (1H, 13C, and 31P) NMR spectroscopy. Instrumentation/Analytical Procedures. CHN elemental analyses were carried out with a Perkin-Elmer 2400 CHNS Elemental Analyzer II (Kanagawa University). Complete elemental analyses were carried out with Mikroanalytisches Labor Pascher (Remagen, Germany). The samples were dried at room temperature under 10-3-10-4 Torr overnight before analysis. IR spectra were recorded on a Jasco 4100 FTIR spectrometer in KBr disks at room temperature. TG/DTA were acquired using a Rigaku Thermo Plus 2 series TG/DTA TG 8120 instrument. 1 H NMR (500.00 MHz) and 31P{1H} NMR (202.00 MHz) spectra in a DMSO-d6 solution were recorded in 5-mm-outerdiameter tubes on a JEOL JNM-ECP 500 FT-NMR spectrometer with a JEOL ECP-500 NMR data processing system. 1 H NMR (399.65 MHz) and 31P NMR (161.70 MHz) spectra in a DMSO-d6 solution were also recorded in 5-mm-outerdiameter tubes on a JEOL JNM-EX 400 FT-NMR spectrometer with a JEOL EX-400 NMR data processing system. The 1 H NMR spectra were referenced to an internal standard of tetramethylsilane (SiMe4). The 31P NMR spectra were referenced to an external standard of 25% H3PO4 in H2O in a sealed capillary. The 31P NMR data with the usual 85% H3PO4 reference are shifted to þ0.544 ppm from our data. Solid-state cross-polarization magic-angle-spinning (CPMAS) 31 P (121.00 MHz) and 29Si (59.71 MHz) NMR spectra were recorded in 6-mm-outer-diameter rotors on a JEOL JNM-ECP 300 FT-NMR spectrometer with a JEOL ECP-300 NMR data processing system. These spectra were referenced to external standards (NH4)2HPO4 (δ 1.60) and poly(dimethylsilane) (δ -34.0), respectively. Preparations. [{Au(PPh3)}4(μ4-O)]3[r-PW12O40]2 3 4EtOH (1). [Au((R,S)-pyrrld)(PPh3)] (0.352 g, 0.599 mmol) was dissolved in 50 mL of CH2Cl2. A clear solution of H3[R-PW12O40] 3 7H2O (0.301 g, 0.100 mmol) dissolved in 30 mL of an EtOH/H2O (12) (a) Singh, A.; Anandhi, U.; Cinellu, M. A.; Sharp, P. R. Dalton Trans. 2008, 2314–2327. (b) Singh, A.; Sharp, P. R. Inorg. Chim. Acta 2008, 361, 3159–3164. (c) Blumenthal, A.; Beruda, H.; Schmidbaur, H. J. Chem. Soc., Chem. Commun. 1993, 1005–1006.
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(5:1, v/v) mixed solvent was slowly added along an interior wall of a round-bottomed flask containing a colorless clear solution of the gold(I) complex. The round-bottomed flask containing two layers, i.e., the gold(I) complex solution in the lower layer and the POM solution in the upper layer, was sealed and left in the dark at room temperature. After 5 days, pale-yellow, clear rod crystals formed around the interface of the two layers, which were collected on a membrane filter (JG 0.2 μm), washed with EtOH (5 mL 1) and Et2O (10 mL 2), and dried in vacuo for 2 h. Yield: 0.242 g (42.1%). The crystalline samples were soluble in DMSO but insoluble in water, acetonitrile, ethanol, and diethyl ether. Found (CHN analysis of an independent preparation): H, 1.67 (1.44); C, 23.18 (23.31); N,
