Syntheses and Reactions of Half-Sandwich Iridium, Rhodium, and

Dec 8, 2009 - Dedicated to Professor Kazuyuki Tatsumi on the occasion of his 60th birthday. , *Corresponding author. E-mail: [email protected]...
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Organometallics 2010, 29, 232–240 DOI: 10.1021/om900921g

Syntheses and Reactions of Half-Sandwich Iridium, Rhodium, and Ruthenium Metallacycles Containing 4-Pyridyl Dithioether Ligands† Ai-Quan Jia, Ying-Feng Han, Yue-Jian Lin, and Guo-Xin Jin* Shanghai Key Laboratory of Molecular Catalysis and Innovative Material, Department of Chemistry, Fudan University, Shanghai 200433, People’s Republic of China Received October 21, 2009

Metallacyclic complexes [Cp*4Ir4(μ-L0 )2(μ-L)2](OTf)4 (2a, L0 = 6,11-dioxy-5,12-naphthacenedione (dhnq2-); L = 4-pyridyl dithioether), [Cp*2Rh2(μ-L0 )(μ-L)](OTf)2 (3b), and [(p-cymene)2Ru2(μ- L0 )(μ-L)](OTf)2 (3c) were obtained by the reactions of Cp*2M2(μ-L0 )Cl2 (M = Ir (1a), Rh (1b)) or (p-cymene)2Ru2(μ-L0 )Cl2 (1c) with a flexible bipyridine-based ligand (L) in the presence of AgOTf (OTf = CF3SO3). Treatments of tetranuclear complex 2a and binuclear complexes 3b and 3c with [Cp*IrCl]2(OTf)2 or [Cp*RhCl]2(OTf)2 gave the homotrinuclear complexes [Cp*3Ir3(μ-L0 )(μ-L)Cl](OTf)3 (4a) and [Cp*3Rh3(μ-L0 )(μ-L)Cl](OTf)3 (4b) and heterotrinuclear complexes [Cp*3Ir2Rh(μ-L0 )(μ-L)Cl](OTf)3 (4c), [Cp*3Rh2Ir(μ-L0 )(μ-L)Cl](OTf)3 (4d), [Cp*(p-cymene)2Ru2Ir(μ-L0 )(μ-L)Cl](OTf)3 (4e), and [Cp*(p-cymene)2Ru2Rh(μ-L0 )(μ-L)Cl](OTf)3 (4f), respectively. The flexible tetranuclear complex 2a exhibited different conformations with different guest solvents. The complexes were characterized by IR, 1H NMR spectroscopy, and elemental analysis. In addition, X-ray structure analyses were performed on ligand L and complexes 2a, 3c, 4a, and 4e. Introduction In the past decade, the metal-directed self-assembly of supramolecular architectures, such as two-dimensional triangles, squares, rectangles, and polygons and three-dimensional cages, has attracted great attention, due to their potential applications as selective receptors, catalysts, and model compounds.1-4 4,40 -Bipyridine-based ligands, espe† Dedicated to Professor Kazuyuki Tatsumi on the occasion of his 60th birthday. *Corresponding author. E-mail: [email protected]. Fax: þ86-2165641740. Tel: þ86-21-65643776. (1) (a) Fujita, M.; Tominaga, M.; Hori, A.; Therrien, B. Acc. Chem. Res. 2005, 38, 369. (b) Boyer, J. L.; Kuhlman, M. L.; Rauchfuss, T. B. Acc. Chem. Res. 2007, 40, 233. (c) Therrien, B.; S€uss-Fink, G.; Govindaswamy, P.; Renfrew, A. K.; Dyson, P. J. Angew. Chem., Int. Ed. 2008, 47, 3773. (2) (a) Romero, F. M.; Ziessel, R.; Dupont-Gervais, A.; Dorsselaer, A. V. Chem. Commun. 1996, 551. (b) Schnebeck, R. D.; Freisinger, E.; Lippert, B. Chem. Commun. 1999, 675. (c) Espinet, P.; Soulantica, K.; Charmant, J. P. H.; Orpen, A. G. Chem. Commun. 2000, 915. (d) Swiegers, G. F.; Malefetse, T. J. Chem. Rev. 2000, 100, 3483. (e) Jiang, H.; Lin, W. J. Am. Chem. Soc. 2003, 125, 8084.(f) Rasika Dias, H. V.; Diyabalanage, H. V. K.; Eldabaja, M. G.; Elbjeirami, O.; Rawashdeh-Omary, M. A.; Omary, M. A. J. Am. Chem. Soc. 2005, 127, 7489. (g) Heo, J.; Jeon, Y. M.; Mirkin, C. A. J. Am. Chem. Soc. 2007, 129, 7712. (3) (a) Fujita, M.; Sasaki, O.; Mitsuhashi, T.; Fujita, T.; Yazaki, J.; Yamaguchi, K.; Ogura, K. Chem. Commun. 1996, 1535. (b) Sautter, A.; Schmid, D. G.; Jung, G.; W€urthner, F. J. Am. Chem. Soc. 2001, 123, 5424. (c) Schweiger, M.; Seidel, S. R.; Arif, A. M.; Stang, P. J. Angew. Chem., Int. Ed. 2001, 40, 3467. (d) Han, Y. F.; Jia, W. G.; Lin, Y. J.; Jin, G.-X. Angew. Chem., Int. Ed. 2009, 48, 6234. (e) Han, Y. F.; Jia, W. G.; Yu, W. B.; Lin, Y. J.; Jin, G.-X. Chem. Soc. Rev. 2009, 38, 3419. (4) (a) Sun, S.-S.; Lees, A. J. J. Am. Chem. Soc. 2000, 122, 8956. (b) Clegg, J. K.; Bray, D. J.; Gloe, K.; Jolliffe, K. A.; Lawrance, G. A.; Lindoy, L. F.; Meehan, G. V.; Wenzel, M. Dalton Trans. 2008, 1331. (5) (a) Kaes, C.; Katz, A.; Hosseini, M. W. Chem. Rev. 2000, 100, 3553. (b) Lee, C.-C.; Hsu, S.-C.; Lai, L.-L.; Lu, K.-L. Inorg. Chem. 2009, 48, 6329. (c) Rishikesh, P.; Keisaku, K.; Lallan, M. Inorg. Chim. Acta 2009, 362, 3219.

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cially the rigid bridging units, play a significant role as building blocks in the construction of supramolecules.5 Recently, increasing interest has been paid to the use of flexible bridging units in the construction of supramolecular architectures because they offer several potential advantages, such as adaptive recognition properties, breathing ability in the solid state, and the possibility for the construction of unprecedented frameworks.6,7 Meanwhile, supramolecular chemistry with organometallic half-sandwich complexes based on Ir, Rh, and Ru fragments has received considerable attention because they can be used to build metallamacrocyclic receptors as well as coordination cages. Many tri-, tetra-, and hexanuclear metallamacrocycles having a combination of halfsandwich complexes with trifunctional ligands were studied (6) (a) Xie, Y.-B.; Li, J.-R.; Zhang, C.; Bu, X.-H. Cryst. Growth Des. 2005, 5, 1743. (b) Maji, T. K.; Mostafa, G.; Matsuda, R.; Kitagawa, S. J. Am. Chem. Soc. 2005, 127, 17152. (c) Uemura, K.; Saito, K.; Kitagawa, S.; Kita, H. J. Am. Chem. Soc. 2006, 128, 16122. (d) Takata, D.; Kitagawa, S. Chem. Mater. 2008, 20, 922, and references therein. (e) Ghosh, S. K.; Kaneko, W.; Kiriya, D.; Ohba, M.; Kitagawa, S. Angew. Chem., Int. Ed. 2008, 47, 3403. (7) (a) Plater, M. J.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 2000, 3065. (b) Su, C.-Y.; Cai, Y.-P.; Chen, C.-L.; Smith, M. D.; Kaim, W.; Zurloye, H.-C. J. Am. Chem. Soc. 2003, 125, 8595. (c) Chatterjee, B.; Noveron, J. C.; Liu, M. J. E.; Resendiz, J.; Yamamoto, T.; Stang, P. J. J. Am. Chem. Soc. 2004, 126, 10645. (d) Dobrzanska, L.; Lloyd, G. O.; Raubenheimer, H. G.; Barbour, L. J. J. Am. Chem. Soc. 2005, 127, 13134. (e) Sathiyendiran, M.; Hang, C.-H.; Luo, C.-T.; Wen, Y.-S.; Lu, K.-L. Dalton Trans. 2007, 1872. (8) (a) Severin, K. Chem. Commun. 2006, 3859. (b) Severin, K. Coord. Chem. Rev. 2003, 245, 3. (c) Fish, R. H.; Jaouen, G. Organometallics 2003, 22, 2166. (d) Govindaswamy, P.; Linder, D.; Lacour, J.; S€uss-Fink, G.; Therrien, B. Chem. Commun. 2006, 4691. (e) Suzuki, H.; Tajima, N.; Tatsumi, K.; Yamamoto, Y. Chem. Commun. 2000, 1801. (f) Mimassi, L.; Cordier, C.; Guyard-Duhayon, C.; Mann, B. E.; Amouri, H. Organometallics 2007, 26, 860. (g) Han, W. S.; Lee, S. W. Dalton Trans. 2004, 1656. (h) Sekioka, Y.; Kaizaki, S.; Mayer, J. M.; Suzuki, T. Inorg. Chem. 2005, 23, 8173. r 2009 American Chemical Society

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Scheme 1. Syntheses of Tetra- and Binuclear Complexes

Scheme 2. Syntheses of Homotrinuclear Complexes 4a and 4b

extensively by some groups.8-10 In addition, Rauchfuss et al. have reported “organometallic boxes” with cyanide-linked cubes that contain octahedral building blocks of rhodium and cobalt derivatives.11 A variety of half-sandwich Ir, Rh, and Ru fragments containing systems such as tetranuclear rectangular molecules, hexanuclear prisms, and octanuclear organometallic boxes have been carefully designed and synthesized using a stepwise synthetic route.9,10 Recently, we successfully extended rectangular frameworks to the third dimension by introducing a 6,11-dihydroxy-5,12-naphthacenedione (H2dhnq) ligand. The large cavity of the metallacycles exhibited selective and reversible CH2Cl2 adsorption properties while retaining single crystallinity.3d Herein, we describe a series of metallacycles with the flexible bridging unit 4-pyridyl dithioether (L) to construct (9) Liu, S.; Han, Y.-F.; Jin, G.-X. Chem. Soc. Rev. 2007, 1543. (10) (a) Wang, J.-Q.; Zhang, Z.; Weng, L.-H.; Jin, G.-X. Chin. Sci. Bull. 2004, 49, 1122. (b) Wang, J.-Q.; Ren, C.-X.; Jin, G.-X. Organometallics 2006, 25, 74. (c) Han, Y.-F.; Jia, W.-G.; Lin, Y.-J.; Jin, G.-X. J. Organomet. Chem. 2008, 693, 546. (d) Han, Y.-F.; Lin, Y.-J.; Weng, L.-H.; Berke, H.; Jin, G.-X. Chem. Commun. 2008, 350. (11) Boyer, J. L.; Kuhlman, M. L.; Rauchfuss, T. B. Acc. Chem. Res. 2007, 40, 233.

bi- and tetranuclear metallacycles (Scheme 1). The flexible bridging unit of 4-pyridyl dithioether (L) also possesses two functionalized sites, i.e., two sulfur atoms, which can be further applied for the construction of homotrinuclear metallacycles (Scheme 2) and heterotrinuclear metallacycles (Scheme 4). A series of bi-, tri-, and tetranuclear halfsandwich iridium, rhodium, and ruthenium complexes with flexible bridging ligands were synthesized and characterized. Moreover, the conversions between tetranuclear or binuclear complexes and homo- or heterotrinuclear complexes were also investigated.

Results and Discussion Syntheses and Characterizations of Half-Sandwich Bi-, Tri, and Tetranuclear Metallacycles. 4-Pyridyl dithioether (L) was prepared by the adoption of a similar reported procedure.6a The structure of L was confirmed by 1H NMR and single-crystal X-ray diffraction analysis (Figure 1). The 1H NMR spectra showed three resonances, which are approximately at δ 3.43 (s), 7.35 (d), and 8.35 (d) ppm in CD3OD; the first resonance is assigned to CH2 protons, and the others are assigned to pyridyl protons.

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Scheme 3. Proposed Conversions of Tetranuclear Complex 2a and Binuclear Complex 3a in Solution

Scheme 4. Syntheses of Heterotrinuclear Complexes 4c, 4d, 4e, and 4f

Following our previous procedure for related compounds, complexes 1a-1c were typically prepared by the reactions of [Cp*IrCl(μ-Cl)]2, [Cp*RhCl(μ-Cl)]2, or [(p-cymene)RuCl(μCl)]2 with H2dhnq(6,11-dihydroxy-5,12-naphthacenedione) with the assistance of CH3ONa in a 1:1:2 ratio in CH3OH at room temperature.3d Treatment of binuclear complex Cp*2Ir2(μ-L0 )Cl2 (1a), Cp*2Rh2(μ-L0 )Cl2 (1b), or (p-cymene)2Ru2(μ-L0 )Cl2 (1c) with a flexible 4-pyridyl dithioether ligand in a 1:1 ratio in the presence of 2 equiv of AgOTf afforded tetranuclear metallacycle 2a and binuclear metallacycles 3b and 3c in high yields, respectively (Scheme 1). Fortunately, we obtained single crystals of 2a and 3c. Thus, their structures were confirmed. Crystals of tetranuclear complex 2a quickly effloresced in the absence of solvent, while binuclear complex 3c did not. Due to the special crystallization ability of 3b, only microcrystals of it were obtained by many efforts. The rhombic microcrystals of 3b were stable in air, unlike the fast efflorescence of tetranuclear complex 2a. As a result, we proposed 3b as a binuclear structure. The 1H NMR spectrum of 2a indicated that the chemical shifts of the pyridyl protons appeared at 7.21 and 8.10 ppm, and the dhnq2- protons appeared at 7.96 and 8.56 ppm. The Cp* moiety revealed one singlet signal (1.74 ppm). For complex 3b, the chemical shifts of the pyridyl protons appeared at 7.16 and 8.06 ppm, the dhnq2- protons appeared at 7.92 and 8.65 ppm, and the Cp* moiety revealed one singlet signal (1.78 ppm). The 1H NMR spectrum of binuclear complex 3c exhibited the existence

Figure 1. Structure of L with thermal ellipsoids drawn at the 30% level. Hydrogen atoms are omitted for clarity. Selected distances (A˚) and angles (deg): S(1)-C(4) 1.754(2), S(1)-C(1) 1.805(2), C(4)-S(1)-C(1) 104.08(9), C(1A)-C(1)-S(1) 112.38(18). Symmetry transformations used to generate equivalent atoms: -x, - yþ2, -zþ2.

of pyridyl (7.06, 8.06 ppm) and dhnq2- (7.91, 8.63 ppm) protons. It is reported that the two neutral sulfur atoms can coordinate to some transition metals, such as Pd, Pt, and Re.12 So we investigated the reactivity of complexes 2a, 3b, and 3c. When tetranuclear complex 2a was treated with equivalent [Cp*IrCl]2(OTf)2, which was obtained by extracting chloride anion from compound [Cp*IrCl2]2 with the help (12) Gibson, V. C.; Long, N. J.; White, A. J. P.; Williams, C. K.; Williams, D. J. Organometallics 2000, 19, 4425.

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Figure 2. (a) 1H NMR spectrum of the aryl part of 2a in CD3OD solution; (b) 1H spectrum of the aryl part of 2a in CD3OD solution two days later.

of AgOTf, homotrinuclear complex 4a was obtained (Scheme 2). It was proposed that the reaction process might start by the dissolution of tetranuclear complex 2a into binuclear complex 3a as the first step (shown in Scheme 3); then, the iridium cation of [Cp*IrCl]2(OTf)2 coordinated to the two sulfur atoms of 3a to form complex 4a. Luckily, we captured the proposed intermediate 3a when we measured the 1H NMR of crystals 2a(1) (vide infra). As shown in Figure 2a, there were eight groups of signals, instead of four groups, about the aryl part of 2a, indicating that there were two compounds in the solution. Two days later we characterized the 1H NMR of the above 2a(1) solution again; to our surprise, only one compound could be found (shown in Figure 2b). 1H NMR measurements were also performed on powder of 2a and crystals of 2a(2) (vide infra); only one compound was found in the two spectra, which were the same as Figure 2b. In addition, we got only single crystals of tetranuclear complex 2a under various conditions in high yields. According to the above results, we could conclude that the 1H spectrum of Figure 2b belonged to tetranuclear complex 2a, while the other groups of proton signals in Figure 2a attached to binuclear complex 3a. Homotrinuclear complex 4b was obtained in a similar way by the reaction of 3b with [Cp*RhCl]2(OTf)2. However, when binuclear complex 3c, [(p-cymene)2Ru2(μ-L0 )(μ-L)](OTf)2, reacted with [(pcymene)RuCl]2(OTf)2, a corresponding homotrinuclear ruthenium complex was not obtained, which showed that the ruthenium cation could not coordinate to the two sulfur atoms properly. In the 1H NMR spectrum of homotrinuclear metallacycles 4a, there were two kinds of Cp* signals: one appeared at 1.77 ppm, and the other appeared at 1.83 ppm. As for 4b, the Cp* signals appeared at 1.70 and 1.81 ppm. Considering the formation of homotrinuclear complexes 4a and 4b, we learned that both iridium and rhodium cations could coordinate to the sulfur atoms efficiently. The results made us wonder whether heterotrinuclear complexes could be synthesized in an analogous way. When [Cp*RhCl]2(OTf)2 was treated with 2a or 3c, heterotrinuclear complexes 4c ([Cp*3Ir2Rh(μ-L0 )(μ-L)Cl](OTf)3) and 4f ([Cp*(p-cymene)2Ru2Rh(μ-L0 )(μ-L)Cl](OTf)3) were synthesized, respectively. When [Cp*IrCl]2(OTf)2 was reacted with

binuclear rhodium complex 3b or ruthenium complex 3c, heterotrinuclear complexes 4d ([Cp*3Rh2Ir(μ-L0 )(μ-L)Cl](OTf)3) and 4e ([Cp*(p-cymene)2Ru2Ir(μ-L0 )(μ-L)Cl](OTf)3) were obtained, respectively. In the 1H NMR spectra of heterotrinuclear complexes 4c and 4d, there were two kinds of Cp* signals. For complexes 4e and 4f, only one kind of Cp* signal was found, their resonances appearing at 1.81 and 1.67 ppm, respectively. The structure of heterotrinuclear complex 4e was confirmed by single-crystal X-ray diffraction analysis. Tetranuclear Metallacycles. Crystals suitable for X-ray crystallography of 2a(1) were obtained by slow diffusion of hexane into a dichloromethane solution, while crystals of 2a(2) were obtained by slow diffusion of diethyl ether into a dichloromethane solution. The crystallographic data and processing parameters are given in Table 1. Single-crystal X-ray diffraction analyses revealed that 2a adopts a tetranuclear architecture (Figure 3). The four Ir(III) ions are bridged by two dhnq2- moieties through eight oxygen atoms and two 4-pyridyl dithioether units by four nitrogen atoms, thereby constituting a parallelogram metallacycle, with each iridium center possessing a distorted octahedral geometry, assuming that Cp* functions as a three-coordinate ligand. In each molecule of 2a(1), there are four dichloromethane molecules inside the channel (Figure 3c), while the counteranions and other four dichloromethane molecules are outside the channels. The four CH2Cl2 guest molecules interact with the “splint” with C-H 3 3 3 π (2.64, 2.94, 3.08 A˚) and p-π (3.47, 3.34 A˚) interactions. The Ir(1) 3 3 3 Ir(2) distance is 8.44 A˚, and the Ir(1) 3 3 3 Ir(2A) distance is 14.64 A˚. The length between S(2) and S(2A) is 3.94 A˚. The distances of the two face-to-face pyridyl rings are in the range 6.59-7.39 A˚. The angles of N(1)-Ir(1)-Ir(2) and N(2A)-Ir(2)-Ir(1) are 71.6° and 79.6°, respectively, leading to the formation of a parallelogram. While in 2a(2), there are two diethyl ether molecules partly inside the cavity (Figure 3d), the counteranions, four dichloromethane molecules, and two diethyl ether molecules are located outside the channels. The S(2) 3 3 3 S(2A) distance (8.56 A˚) is much longer than that in 2a(1). The angels of N(1)-Ir(1)-Ir(2) and N(2)-Ir(2)-Ir(1) are 80.9° and 88.0°, respectively, much larger than that in 2a(1).

)

C12H12N2S2

L

2a(1)

2a(2)

3c

4a(1)

Table 1. Summary of Crystallographic Data for L, 2a(1), 2a(2), 3c, 4a(1), 4a(2), and 4e 4a(2)

C112H116Cl16F12Ir4C124H148Cl8 F12Ir4C52H48F6N2O10Ru2S4 C63H65ClF9Ir3N2O13S5 C64H67Cl3F9Ir3N2N4O20S8 N4O24S8 O13S5 fw 248.36 3658.57 3615.34 1305.30 2001.52 2086.45 T, K 293(2) 293(2) 193(2) 293(2) 293(2) 293(2) cryst syst monoclinic triclinic monoclinic, monoclinic monoclinic orthorhombic P2(1)/c P2(1)/m P2(1)/c Pna2(1) space group P2(1)/c P1 a, A˚ 9.441(4) 11.719(5) 18.710(2) 10.542(3) 20.495(10) 15.803(6) b, A˚ 14.999(5) 14.770(6) 26.661(3) 30.577(8) 15.059(8) 42.770(17) c, A˚ 9.799(4) 21.002(8) 14.858(2) 16.928(5) 24.303(12) 10.751(4) R, deg 90 97.772(6) 90 90 90 90 β, deg 118.147(4) 94.503(6) 90.984(2) 99.017(4) 91.349(7) 90 γ, deg 90 103.604(6) 90 90 90 90 3 1223(8) 3478(2) 7410(1) 5389(2) 7498(7) 7267(5) volume, A˚ Z 4 1 2 4 4 4 1.348 1.747 1.620 1.609 1.773 1.907 Dcalc, Mg/m3 0.408 4.319 3.916 0.795 5.565 5.818 absorp coeff, mm-1 F(000) 520 1792 3584 2640 3880 4048 cryst size, mm 0.25  0.15  0.08 0.15  0.08  0.06 0.25  0.12  0.07 0.18  0.12  0.08 0.10  0.08  0.08 0.15  0.10  0.10 2θ range, deg 2.72-27.00 1.44-25.01 1.88-26.40 1.22-25.01 1.59-25.01 1.37-27.01 no. of reflns collected/unique 5805/2612 14 534/12 042 40 561/15 132 22 547/ 9673 30 315/13 205 34 110/15 209 [R(int) = 0.0351] [R(int) = 0.0526] [R(int) = 0.0704] [R(int) = 0.0781] [R(int) = 0.0894] [R(int) = 0.0725] no. of data/restraints/params 2612/0/145 12 042/137/780 15 132/0/838 9673/16/650 13 205/75/837 15 209/29/845 0.845 0.838 0.972 0.894 0.792 0.889 goodness of fit on F2 R1 = 0.0381 R1 = 0.0599 R1 = 0.0611 R1 = 0.0867 R1 = 0.0581 R1 = 0.0539 final R indices [I > 2σ(I)]a wR2 =0.0898 wR2 = 0.1499 wR2 = 0.1573 wR2 = 0.2619 wR2 = 0.1434 wR2 = 0.1050 0.232 and -0.197 1.439 and -0.959 2.576 and -1.898 1.446 and -0.652 1.268 and -0.747 1.085 and -0.885 lgst diff peak and hole, e/A˚3 P P P a R1 = Fo| - |Fc (based on reflections with Fo2 > 2σF2). wR2 = [ [w(Fo2 - Fc2)2]/ [w(Fo2)2]]1/2; w = 1/[σ2(Fo2) þ (0.095P)2]; P = [max(Fo2, 0) þ 2Fc2]/3 (also with Fo2 > 2σF2).

formula

)

C64H65Cl3F9IrN2O13Ru2S5 1901.16 293(2) monoclinic P2(1)/c 21.61(5) 13.90(3) 26.35(6) 90 112.29(3) 90 7324(26) 4 1.724 2.555 3772 0.12  0.12  0.10 1.59-25.01 29 593/12 910 [R(int) = 0.0981] 12 910/19/857 0.810 R1 = 0.0630 wR2 = 0.1581 1.480 and -1.072

4e

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Figure 3. (a) Cationic structure of 2a(1) with thermal ellipsoids drawn at the 30% level. Hydrogen atoms and solvent molecules are omitted for clarity. (b) Space-filling model of cationic molecular 2a based on its X-ray coordinates (Ir red; O turquiose; N blue; C gray; S yellow). (c) Ball-and-stick model of cationic molecular 2a based on its X-ray coordinates (Ir red; O turquiose; N blue; C gray; S yellow; Cl bright green). (d) Ball-and-stick model of cationic molecular 2a(2) based on its X-ray coordinates (Ir red; O turquiose; N blue; C gray; S yellow). Selected distances (A˚) and angles (deg) for 2a(1): Ir(1)-O(1) 2.045(7), Ir(1)-O(2) 2.085(7), Ir(1)-N(1) 2.150(10), Ir(2)-N(2) 2.106(10), S(1)-C(23) 1.755(14), S(1)-C(19) 1.794(15), S(2)-C(20) 1.823(13), S(2)-C(28) 1.750(13), O(1)-Ir(1)-O(2) 84.9(3), C(23)-S(1)-C(19) 105.9(8), C(28)-S(2)-C(20) 105.7(6), C(19)-C(20)-S(2) 113.2(10).

Other selected bond lengths and angles are given in Figure 3. The dimensions of the rectangular box are 14.6  8.4  9.8 A˚ for 2a(1) (Figure 3b) and 14.8  8.5  9.8 A˚ for 2a(2), which are larger than the reported bpe (bpe = 1,2-bis(4-pyridyl)ethylene)-bridged tetranuclear iridium complex [Cp*4Ir4(μ-bpe)2(μ-dhnq)2](OTf)4 (13.6  6.9  8.4 A˚).3d The larger cavity of 2a can host more dichloromethane molecules compared to the known compound. For example, there are four CH2Cl2 molecules in the cavity of complex 2a(1), while only two dichloromethane molecules were found in the reported complex [Cp*4Ir4(μ-pyrazine)2(μ-dhnq)2](OTf)4 (9.8  6.9  8.4 A˚).3d Binuclear Metallacycles. Complex 3c adopts a binuclear molecular structure (Figure 4). In addition to a bridging dhnq2- moiety, the two Ru(II) centers are also coordinated by a flexible 4-pyridyl dithioether unit, as the third apex of the triangle, in which the Ru 3 3 3 Ru distance (8.30 A˚) is a little shorter than the Ir(1) 3 3 3 Ir(2) distance (8.44 A˚) in 2a. The N(1)-Ru(1)-Ru(1A) and N(1A)-Ru(1A)-Ru(1) angles are both 66.6°, and thus an isosceles triangle is produced. The distances of the two face-to-face pyridyl rings are in the range 4.60-6.64 A˚, which are much shorter than those for 2a. Other selected bond lengths and angles are given in Figure 4. Trinuclear Metallacycles. Different shapes of single crystals were found in the same CH2Cl2/Et2O mixed-solvent solution when we tried to obtain 4a. As the unit cell

parameters of the two shapes of single crystals were apparently different from each other, we refined their structures separately. As expected, their framework was similar; the only difference was that one had a dichloromethane molecule outside the framework, while the other one did not. Perspective drawings of 4a(1) and 4a(2) with the atomic numbering scheme are given in Figures 5 and 6, and selected bond lengths and angles are also given in these figures. Taking 4a(2) for example, it adopts a homotrinuclear molecular structure. The Ir(1) 3 3 3 Ir(2) distance (8.45 A˚) is almost the same as that in 2a (8.44 A˚), but it is a little longer than the Ru 3 3 3 Ru distance (8.30 A˚) in binuclear complex 3c. The Ir(1) 3 3 3 Ir(3) distance is 7.56 A˚ and the Ir(2) 3 3 3 Ir(3) distance is 7.60 A˚, shorter than that of Ir(1) 3 3 3 Ir(2). The angle of Ir(1)-Ir(3)-Ir(2) is 67.7°, while the angles of Ir(1)-Ir(2)-Ir(3) and Ir(2)-Ir(1)-Ir(3) are 55.9° and 56.4°, respectively; thus a roughly isosceles triangle is produced. The distances of the two face-to-face pyridyl rings are in the range 4.87-7.09 A˚, which are longer than those for binuclear ruthenium complex 3c. A view of the space-filling model of trinuclear 4a(2) (Figure 6c) suggests that the cavity is not large enough to accommodate dichloromethane molecules. Other selected bond lengths and angles are given in Figure 6. Compared to homotrinuclear complex 4a, 4e adopts a heterotrinuclear molecular structure (Figure 7). The Ru 3 3 3 Ru distance (8.44 A˚) is a little longer than the Ru 3 3 3 Ru distance (8.30 A˚) in 3c. The Ir(1) 3 3 3 Ru(1) and

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and 57.2°, respectively, which are also comparable to Ir(1)-Ir(2)-Ir(3) (55.9°) and Ir(2)-Ir(1)-Ir(3) (56.4°) in 4a. The angles of N(1)-Ru(1)-Ru(2) and N(2)-Ru(2)-Ru(1) are 71.1° and 75.1°, which are much larger than those in binuclear 3c (66.6°). The distances of the two face-to-face pyridyl rings are in the range 4.89-7.20 A˚, which are longer than those in 3c (4.60-6.64 A˚). But they are almost the same as those in homotrinuclear complex 4a (4.87-7.09 A˚). Other selected bond lengths and angles are given in Figure 7.

Conclusion

Figure 4. Cationic structure of 3c with thermal ellipsoids drawn at the 30% level. Hydrogen atoms are omitted for clarity. Selected distances (A˚) and angles (deg): Ru(1)-O(1) 2.040(6), Ru(1)-O(2) 2.029(5), Ru(1)-N(1) 2.092(8), S(1)-C(13) 1.759(13), S(1)-C(10) 1.76(3), O(1)-Ru(1)-O(2) 85.4(2), C(13)-S(1)-C(10) 99.8(10). Symmetry transformations used to generate equivalent atoms: x, -yþ3/2, z.

Figure 5. Cationic structure of 4a(1) with thermal ellipsoids drawn at the 30% level. Hydrogen atoms are omitted for clarity. Selected distances (A˚) and angles (deg): Ir(1)-O(1) 2.074(8), Ir(1)-O(2) 2.061(8), Ir(1)-N(1) 2.116(11), Ir(2)-O(3) 2.089(8), Ir(2)-O(4) 2.034(9), Ir(2)-N(2) 2.121(11), Ir(3)-S(1) 2.372(4), Ir(3)-S(2) 2.347(5), Ir(3)-Cl(1) 2.367(4), S(1)-C(19) 1.729(17), S(1)-C(23) 1.815(15), S(2)-C(20) 1.786(15), S(2)-C(28) 1.798(14), O(1)-Ir(1)-O(2) 85.2(3), O(3)-Ir(2)-O(4) 83.7(3), S(1)-Ir(3)-S(2) 86.7(2), S(1)-Ir(3)-Cl(1) 93.3(2), S(2)-Ir(3)-Cl(1) 86.7(2).

Ir(1) 3 3 3 Ru(2) distances are 7.66 and 7.44 A˚, respectively. They are similar to the Ir(1) 3 3 3 Ir(3) distance (7.56 A˚) and Ir(2) 3 3 3 Ir(3) distance (7.60 A˚) in homotrinuclear complex 4a. The angle of Ru(1)-Ir(1)-Ru(2) is 67.9°, almost the same as the Ir(1)-Ir(3)-Ir(2) angle (67.7°) in 4a. The angles of Ir(1)-Ru(1)-Ru(2) and Ir(1)-Ru(2)-Ru(1) are 54.8°

In summary, we have synthesized a series of bi-, tetra-, homotri-, and heterotrinuclear half-sandwich iridium, rhodium, and ruthenium metallacycles containing both dhnq2and flexible 4-pyridyl dithioether mixed ligand systems. Different guest solvent molecules and flexible frameworks lead to different conformations of the tetranuclear iridium complex. The reactions between bi- or tetranuclear complexes and homotri- or heterotrinuclear complexes were studied. A combination of X-ray crystallographic and spectroscopic studies confirms the nature of these half-sandwich complexes and their transformations.

Experimental Section General Procedures. Except for the preparation of the ligand L, all reactions and manipulations were performed under an argon atmosphere, using standard Schlenk techniques. Solvents were purified by standard methods prior to use. [Cp*MCl2]2 (M = Rh, Ir),13 [p-cymene-RuCl2]2,14 Cp*2M2(μ-L0 )Cl2 (M = Ir (1a), Rh (1b); L0 = dhnq2-),3d and (p-cymene)2Ru2(μ-L0 )Cl2 (1c)3d were prepared according to the literature. The 1H NMR spectra were measured on a VAVCE-DMX 400 spectrometer in CD3OD. Elemental analysis was performed on an Elementar Vario EL III analyzer. IR (KBr) spectra were recorded on the Nicolet FT-IR spectrophotometer. Preparation of L. A mixture of pyridine-4-thiol (3.33 g, 30.0 mmol), potassium hydroxide (1.68 g, 30.0 mmol), and 20 mL of ethanol was stirred at room temperature for 2 h, and then a solution of 1,2-dibromoethane (2.82 g, 15.0 mmol) in 5 mL of ethanol was dropwise added. The reaction mixture was stirred for 8 h. The product was obtained by filtration and washed by ethanol to afford fine colorless needles in 60.0% (2.23 g) yield. 1H NMR (CD3OD, 400 MHz): δ 3.43 (s, 4H, CH2), 7.35 (d, 4H, pyridyl), 8.35 (d, 4H, pyridyl). Preparation of 2a. Ag(CF3SO3) (25.5 mg, 0.1 mmol) was added to a solution of 1a (50.7 mg, 0.05 mmol) in CH3OH (20 mL) at room temperature and stirred for 4 h, followed by filtration to remove insoluble AgCl. 4-Pyridyl dithioether (12.4 mg, 0.05 mmol) was added to the filtrate and stirred for 10 h. The solvent was removed, and the residue was extracted with CH2Cl2, followed by filtration to remove insoluble compounds. The filtrate was concentrated to about 3 mL, and diethyl ether was added to give 2a as a dark green solid. Yield: 67.0 mg (90.0%). IR (KBr): ν 1599(m), 1540(s), 1452(m), 1407(m), 1387(m), 1264(s), 1156(m), 1030(m), 638(m) cm-1. 1 H NMR (400 Hz, CD3OD): δ 1.74 (s, 60H, Cp*), 3.34 (s, 8H, CH2), 7.21 (d, 8H, pyridyl), 7.96 (q, 8H, dhnq), 8.10 (d, 8H, pyridyl), 8.56 (q, 8H, dhnq). Anal. Calcd (%) for C104H116F12Ir4N4O20S8: C 41.70, H 3.90, N 1.87. Found: C 41.36, H 3.84, N 1.90. Preparation of 3b. Ag(CF3SO3) (25.5 mg, 0.1 mmol) was added to a solution of 1b (41.8 mg, 0.05 mmol) in CH3OH (13) White, C.; Yates, A.; Maitlis, P. M. Inorg. Synth. 1992, 29, 228. (14) Bennett, M. A.; Smith, A. K. J. Chem. Soc., Dalton Trans. 1974, 233.

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Figure 6. (a) Cationic structure of 4a(2) with thermal ellipsoids drawn at the 30% level. Hydrogen atoms are omitted for clarity. (b) Ball-and-stick model of cationic molecular 4a(2) based on its X-ray coordinates (Ir red; O turquiose; N blue; C gray; S yellow; Cl bright green). (c) Space-filling model of cationic molecular 4a(2) based on its X-ray coordinates (Ir red; O turquiose; N blue; C gray; S yellow; Cl bright green). Selected distances (A˚) and angles (deg): Ir(1)-O(1) 2.082(9), Ir(1)-O(2) 2.098(8), Ir(1)-N(1) 2.132(10), Ir(2)-O(3) 2.081(9), Ir(2)-O(4) 2.051(8), Ir(2)-N(2) 2.106(10), Ir(3)-S(1) 2.351(4), Ir(3)-S(2) 2.358(4), Ir(3)-Cl(1) 2.365(3), S(1)-C(19) 1.861(14), S(1)-C(23) 1.799(12), S(2)-C(20) 1.876(15), S(2)-C(28) 1.800(15), O(1)-Ir(1)-O(2) 84.5(3), O(3)-Ir(2)-O(4) 84.5(3), S(1)-Ir(3)-S(2) 86.6(1), S(1)-Ir(3)-Cl(1) 90.7(2), S(2)-Ir(3)-Cl(1) 93.6(1). (20 mL) at room temperature and stirred for 4 h, followed by filtration to remove insoluble AgCl. 4-Pyridyl dithioether (12.4 mg, 0.05 mmol) was added to the filtrate and stirred for 10 h. The solvent was removed, and the residue was extracted with CH2Cl2, followed by filtration to remove insoluble compounds. The filtrate was concentrated to about 3 mL, and diethyl ether was added to give 3b as a dark green solid. Yield: 60.3 mg (92.0%). IR (KBr): ν 1596(m), 1541(s), 1451(m), 1399(m), 1387(m), 1263(s), 1154(m), 1031(m), 638(m) cm-1. 1H NMR (400 Hz, CD3OD): δ 1.78 (s, 60H, Cp*), 3.29 (s, 8H, CH2), 7.16 (d, 8H, pyridyl), 7.92 (q, 8H, dhnq), 8.06 (d, 8H, pyridyl), 8.65 (q, 8H, dhnq). Anal. Calcd (%) for C52H58F6Rh2N2O10S4: C 47.35, H 4.43, N 2.12. Found: C 47.26, H 4.38, N 2.07. Preparation of 3c. Ag(CF3SO3) (22.1 mg, 0.08 mmol) was added to a solution of 1c (36.0 mg, 0.04 mmol) in CH3OH (20 mL) at room temperature and stirred for 4 h, followed by filtration to remove insoluble AgCl. 4-Pyridyl dithioether (9.9 mg, 0.04 mmol) was added to the filtrate and stirred for 10 h. The solvent was removed, and the residue was extracted with CH2Cl2, followed by filtration to remove insoluble compounds. The filtrate was concentrated to about 3 mL, and diethyl ether was added to give 3c as dark green crystals. Yield: 46.0 mg (88.2%). IR (KBr): ν 1600(m), 1540(s), 1386(m), 1262(s),

1151(m), 1092(s), 1030(m), 475(m) cm-1. 1H NMR (400 Hz, CD3OD): δ 1.36 (d, 12H, CH(CH3)2), 2.22 (s, 6H, C6H4CH3), 2.95 (sept, 2H, CH), 3.22 (s, 4H, CH2), 5.72 (d, 4H, C6H4), 6.01 (d, 4H, C6H4), 7.06 (d, 4H, pyridyl), 7.91 (q, 4H, dhnq), 8.06 (d, 4H, pyridyl), 8.63 (q, 4H, dhnq). Anal. Calcd (%) for C52H48F6N2O10Ru2S4: C 47.85, H 3.71, N 2.15. Found: C 47.76, H 3.74, N 2.11. Preparation of 4a. Ag(CF3SO3) (5.1 mg, 0.02 mmol) was added to a solution of [Cp*IrCl2]2 (8.0 mg, 0.01 mmol) in CH3OH (20 mL) at room temperature and stirred for 4 h, followed by filtration to remove insoluble AgCl. 2a (30.0 mg, 0.01 mmol) was added to the filtrate and stirred for 10 h. The solvent was removed and the residue was extracted with CH2Cl2, followed by filtration to remove insoluble compounds. The filtrate was concentrated to about 3 mL and diethyl ether was added to give 4a as dark red crystals. Yield: 34.3 mg (85.7%). IR (KBr): ν 1598(m), 1541(s), 1452(m), 1383(m), 1262(s), 1156(m), 1032(m), 935(m) cm-1. 1H NMR (400 Hz, CD3OD): δ 1.77 (s, 30H, Cp*), 1.83 (s, 15H, Cp*IrCl), 3.20 (m, 2H, CH2), 3.48 (m, 2H, CH2), 7.15 (s, 4H, aryl) 7.86 (m, 2H, aryl), 7.98 (m, 2H, aryl), 8.47 (m, 6H, aryl), 8.68 (m, 2H, aryl). Anal. Calcd (%) for C63H65ClF9Ir3N2O13S5: C 37.80, H 3.27, N 1.40. Found: C 37.76, H 3.23, N 1.41.

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Figure 7. Cationic structure of 4e with thermal ellipsoids drawn at the 30% level. Hydrogen atoms are omitted for clarity. Selected distances (A˚) and angles (deg): Ru(1)-O(1) 2.051(7), Ru(1)-O(2) 2.048(7), Ru(2)-O(3) 2.051(7), Ru(2)-O(4) 2.046(7), Ru(1)-N(1) 2.136(8), Ru(2)-N(2) 2.133(10), Ir(2)-O(3) 2.089(8), Ir(2)-O(4) 2.034(9), Ir(2)-N(2) 2.121(11), Ir(1)-S(1) 2.372(4), Ir(1)-S(2) 2.389(5), Ir(1)-Cl(1) 2.377(5), S(1)-C(19) 1.858(12), S(1)-C(23), 1.801(10), S(2)-C(20) 1.794(12), S(2)-C(28) 1.769(12), O(1)-Ru(1)-O(2) 85.6(3), O(3)-Ru(2)-O(4) 85.2(3), S(1)-Ir(1)-S(2) 86.72(18), S(1)-Ir(1)-Cl(1) 90.28(17), S(2)-Ir(1)-Cl(1) 93.68(14). Preparation of 4b. Ag(CF3SO3) (5.1 mg, 0.02 mmol) was added to a solution of [Cp*RhCl2]2 (6.2 mg, 0.01 mmol) in CH3OH (20 mL) at room temperature and stirred for 4 h, followed by filtration to remove insoluble AgCl. 3b (26.2 mg, 0.02 mmol) was added to the filtrate and stirred for 12 h. The solvent was removed and the residue was extracted with CH2Cl2, followed by filtration to remove insoluble compounds. The filtrate was concentrated to about 3 mL, and diethyl ether was added to give 4b as dark red crystals. Yield: 27.7 mg (80.0%). IR (KBr): ν 1597(m), 1541(s), 1452(m), 1380(m), 1259(s), 1162(m), 1031(m), 922(m), 640(s) cm-1. 1H NMR (400 Hz, CD3OD): δ 1.70 (s, 30H, Cp*), 1.81 (s, 15H, Cp*IrCl), 3.70 (s, 4H, CH2), 7.30 (d, 4H, pyridyl), 7.93 (q, 4H, dhnq), 8.03 (d, 4H, pyridyl), 8.71 (q, 4H, dhnq). Anal. Calcd (%) for C63H65ClF9Rh3N2O13S5: C 43.65, H 3.78, N 1.62. Found: C 43.56, H 3.69, N 1.53. Preparation of 4c. Ag(CF3SO3) (5.1 mg, 0.02 mmol) was added to a solution of [Cp*RhCl2]2 (6.2 mg, 0.01 mmol) in CH3OH (20 mL) at room temperature and stirred for 4 h, followed by filtration to remove insoluble AgCl. 2a (30.0 mg, 0.01 mmol) was added to the filtrate and stirred for 12 h. The solvent was removed and the residue was extracted with CH2Cl2, followed by filtration to remove insoluble compounds. The filtrate was concentrated to about 3 mL, and diethyl ether was added to give 4c as dark red crystals. Yield: 28.7 mg (75.0%). IR (KBr): ν 1629(m), 1539(s), 1386(m), 1265(s), 1153(m), 1032(m), 639(s) cm-1. 1H NMR (400 Hz, CD3OD): δ 1.67 (s, 30H, Cp*), 1.83 (s, 15H, Cp*IrCl), 3.71 (s, 4H, CH2), 7.31 (d, 4H, pyridyl), 7.88 (q, 4H, dhnq), 8.05 (d, 4H, pyridyl), 8.73 (q, 4H, dhnq). Anal. Calcd (%) for C63H65ClF9Ir2RhN2O13S5: C 39.57, H 3.43, N 1.46. Found: C 39.46, H 3.29, N 1.41. Preparation of 4d. Ag(CF3SO3) (5.1 mg, 0.02 mmol) was added to a solution of [Cp*IrCl2]2 (8.0 mg, 0.01 mmol) in CH3OH (20 mL) at room temperature and stirred for 4 h, followed by filtration to remove insoluble AgCl. 3b (26.2 mg, 0.02 mmol) was added to the filtrate and stirred for 12 h.

Jia et al. The solvent was removed and the residue was extracted with CH2Cl2, followed by filtration to remove insoluble compounds. The filtrate was concentrated to about 3 mL, and diethyl ether was added to give 4d as dark red crystals. Yield: 23.7 mg (65.0%). IR (KBr): ν 1623(m), 1593(m), 1542(s), 1383(m), 1260(s), 1035(m), 641(s) cm-1. 1H NMR (400 Hz, CD3OD): δ 1.78 (s, 30H, Cp*), 1.83 (s, 15H, Cp*IrCl), 3.72 (s, 2H, CH2), 7.21 (d, 8H, pyridyl), 7.90 (q, 4H, dhnq), 8.12 (d, 4H, pyridyl), 8.58 (q, 4H, dhnq). Anal. Calcd (%) for C63H65ClF9IrRh2N2O13S5: C 41.49, H 3.60, N 1.54. Found: C 41.35, H 3.53, N 1.48. Preparation of 4e. Ag(CF3SO3) (5.1 mg, 0.02 mmol) was added to a solution of [Cp*IrCl2]2 (8.0 mg, 0.01 mmol) in CH3OH (20 mL) at room temperature and stirred for 4 h, followed by filtration to remove insoluble AgCl. 3c (26.1 mg, 0.02 mmol) was added to the filtrate and stirred for 10 h. The solvent was removed, and the residue was extracted with CH2Cl2, followed by filtration to remove insoluble compounds. The filtrate was concentrated to about 3 mL, and diethyl ether was added to give 4e as dark red crystals. Yield: 24.8 mg (65.2%). IR (KBr): ν 1597(s), 1541(m), 1408(s), 1387(s), 1276(m), 1157(m), 1030(s), 938(m), 638(m) cm-1. 1H NMR (400 Hz, CD3OD): δ 1.80 (s, 15H, Cp*IrCl), 1.40 (d, 12H, CH(CH3)2), 2.31 (s, 6H, C6H4CH3), 3.00 (sept, 2H, CH), 3.35 (s, 4H, CH2), 5.79 (d, 4H, C6H4), 6.06 (d, 4H, C6H4), 6.98 (d, 4H, pyridyl), 7.98 (q, 4H, dhnq), 8.50 (m, 4H, pyridyl), 8.73 (q, 4H, dhnq). Anal. Calcd (%) for C63H63ClF9IrN2O13Ru2S5: C 41.64, H 3.49, N 1.54. Found: C 41.52, H 3.41, N 1.49. Preparation of 4f. Ag(CF3SO3) (5.1 mg, 0.02 mmol) was added to a solution of [Cp*RhCl2]2 (6.2 mg, 0.01 mmol) in CH3OH (20 mL) at room temperature and stirred for 4 h, followed by filtration to remove insoluble AgCl. 3c (26.2 mg, 0.02 mmol) was added to the filtrate and stirred for 12 h. The solvent was removed, and the residue was extracted with CH2Cl2, followed by filtration to remove insoluble compounds. The filtrate was concentrated to about 3 mL, and diethyl ether was added to give 4f as dark red crystals. Yield: 25.2 mg (73.0%). IR (KBr): ν 1593(m), 1542(s), 1387(m), 1264(s), 1162(m), 1032(m), 640(s) cm-1. 1H NMR (400 Hz, CD3OD): δ 1.67 (s, 15H, Cp*RhCl), 1.49 (d, 12H, CH(CH3)2), 2.42 (s, 6H, C6H4CH3), 3.00 (sept, 2H, CH), 3.71 (s, 4H, CH2), 5.80 (d, 4H, C6H4), 6.05 (d, 4H, C6H4), 7.33 (d, 4H, pyridyl), 7.95 (q, 4H, dhnq), 8.07 (d, 4H, pyridyl), 8.74 (q, 4H, dhnq). Anal. Calcd (%) for C63H63ClF9RhN2O13Ru2S5: C 43.79, H 3.67, N 1.62. Found: C 43.72, H 3.61, N 1.57. X-ray Crystallography. Suitable crystals for X-ray analysis of L were obtained by crystallization in cool ethanol. Crystals of 2a(1) were obtained from a CH2Cl2/hexane mixed solution, while crystals of 2a(2), 3c, 4a, and 4e were obtained from a CH2Cl2/Et2O mixed solution of the corresponding complexes. A single crystal suitable for X-ray analysis was sealed into a glass capillary in case it effloresced, and analysis was carried out at room temperature. A crystal of 2a(2) for X-ray analysis was analyzed at low temperature. Details of the data collection and refinement are summarized in Table 1. The structures were solved by direct methods using SHELX-97 and refined by fullmatrix least-squares calculations, using the program system SHELXTL-97.

Acknowledgment. This work was supported by the National Science Foundation of China (20721063, 20771028), Shanghai Leading Academic Discipline Project (B108), Shanghai Science and Technology Committee (08DZ2270500, 08DJ1400103), and the National Basic Research Program of China (2009CB825300). Supporting Information Available: The crystallographic data for 2a(1), 2a(2), 3c, 4a(1), 4a(2), 4e, and L are available free of charge via the Internet at http://pubs.acs.org.