Isomers of Cyclometalated Macrocycles Constructed through Olefinic

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Isomers of Cyclometalated Macrocycles Constructed through Olefinic C−H Activation Long Zhang, Hao Li, Lin-Hong Weng, 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 S Supporting Information *

ABSTRACT: A new series of dinuclear complexes [(Cp*M)2{(2pyridyl)-CC-(2-pyridyl)}Cl2] (M = Rh (1a), Ir (1b)) and tetranuclear metallamacrocycles [{(Cp*M) 2 {(2-pyridyl)-CC-(2-pyridyl)}(pyrazine)}2](OTf)4 (M = Rh (2a), Ir (2b)), [{(Cp*M)2{(2-pyridyl)CC-(2-pyridyl)}(bpy)}2](OTf)4 (M = Rh (3a), Ir (3b); bpy = 4,4′bipyridine), and [{(Cp*M)2{(2-pyridyl)-CC-(2-pyridyl)}(bpe)}2](OTf)4 (M = Rh (4a), Ir (4b); 4,4′-bpe = trans-1,2-bis(4-pyridyl)ethylene) were constructed stepwise through double-site C−H activation on the olefinic CC bond of 1,2-bis(2-pyridyl)ethylene. Isomers were observed in both the dinuclear species and tetranuclear macrocyclic complexes and were confirmed by single-crystal X-ray diffraction. The molecular structures of 1a−c, (R,R)-(S,S)-3b, (R,R)-(S,S)-4a, (R,R)(R,R)-/(S,S)-(S,S)-4a, and (R,R)-(S,S)-4b were characterized by singlecrystal X-ray crystallography. All complexes were fully characterized by 1H NMR spectroscopy, ESI-MS, and elemental analysis.

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INTRODUCTION In the past decade, there has been growing interest in macrocycles due to their great structural diversities and various potential applications, including host−guest chemistry, catalysis, molecular recognition, luminescent and electrochemical sensors, etc.1 In particular, organometallic half-sandwich Cp*Ir and Cp*Rh fragments have been used as building blocks to construct discrete metallamacrocycles and metallacages because of their stable coordination geometry and interesting properties.2 A key step in forming such assemblies is to synthesize dinuclear chelating linkers (Scheme 1). A variety of chelating

cyclometalated complexes is a key step for the development of synthetic applications. Metalation of an ortho C−H bond of a substituted phenyl to form a five-membered metallacycle with a nitrogen-containing ligand is a reliable strategy (eq 1 in Scheme 2).8 In 2003, the Davies group developed sodium acetate promoted efficient C−H activation.9 It is worth noting that, in contrast to aromatic C−H bond activation, there are only a few examples of olefinic C−H bond activation. It was therefore deemed worthwhile to investigate the reactivity of olefin Scheme 2. Formation of Dinuclear Cyclometalated Complexes

Scheme 1. Dinuclear Complexes as Building Blocks

linkers with different coordinating sites, including O∧O− O∧O,2a,3−5 O∧N−O∧N,6 and N∧N−N∧N,7 were reported. It is our intention to extend the choice of chelating linkers and, moreover, to functionalize the resulting dinuclear complexes in order to achieve molecular architectures with interesting properties. C−H bond activation mediated by transition metals is one of the most active areas in modern chemistry.8 The formation of © 2014 American Chemical Society

Received: November 27, 2013 Published: January 10, 2014 587

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by the downfield shifts of the signals of 2,2′-bpe. The signals of the alkene group in 1H NMR spectra disappear, suggesting that the alkene C−H bonds are activated. Because of the asymmetrical nature of the metal centers, complexes 1a,b have two possible enantiomers (Figure 1). The

substrates, so that this methodology could be extended to broader applications. To the best of our knowledge, cyclometalated structures not only are interesting for organic synthetic chemistry but also affect the properties of molecular assemblies when they are introduced. In previous works, our group reported a new class of metallamacrocycles using the activated aromatic C−H bond compounds as building blocks (eq 2 in Scheme 2).10 In comparison with macrocycles with common chelating linkers, the cyclometalated species show an increase in structural stability.9c We also reported several cases of metallamacrocycles utilizing functionalization of C−H bonds of aromatic or olefinic carboxylic acids as building blocks without witnessing a similar rigid structure.11 It is important to further investigate the cyclometalated macrocycle chemistry, so that a deeper insight into the effects of cyclometalated structures on the stabilities of the metallamacrocycles could be obtained. Here, we report the double-site activation of olefinic C−H bonds with two directing pyridyl groups and use it to effectively prepare a series of cyclometalated macrocycles. Isomers of tetranuclear macrocycles were observed and, for the first time to our knowledge, unambiguously confirmed by single-crystal X-ray crystallography.

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Scheme 3. Preparation of Dinuclear Complexes 1a,b

Figure 1. (a) Molecular structures of enantiomers of 1a. Selected bond lengths (Å) and angles (deg): Rh(1)−C(7) 2.027(4), Rh(1)−N(1) 2.077(3), Rh(1)−Cl(1) 2.4001(11); C(7)−Rh(1)−N(1) 76.78(15), C(7)−Rh(1)−Cl(1) 91.77(12), N(1)−Rh(1)−Cl(1) 89.57(10). (b) Molecular structures of enantiomers of 1b. Selected bond lengths (Å) and angles (deg): Ir(1)−C(1) 2.035(6), Ir(1)−N(1) 2.076(5), Ir(1)− Cl(1) 2.409(8), H(1)−Cl(1) 2.38(7); C(1)−Ir(1)−N(1) 76.1(2), C(1)−Ir(1)−Cl(1) 92.12(17), N(1)−Ir(1)−Cl(1) 87.02(16), O(1)− H(1)−Cl(1) 165(8). (c) Molecular structures of enantiomers of 1c. Selected bond lengths (Å) and angles (deg): Ir(1)−C(7) 2.034(5), Ir(1)−N(1) 2.084(4), Ir(1)−Cl(1) 2.3939(15); C(7)−Ir(1)−N(1) 77.18(19), C(7)−Ir(1)−Cl(1) 88.55(14), N(1)−Ir(1)−Cl(1) 86.60(12). Color code: C, gray; N, blue; Rh, orange; Ir, pink; Cl, green; O, red; H, light blue. Hydrogen atoms are omitted for clarity, except for those involved in hydrogen bonds.

treated with [Cp*RhCl2]2 or [Cp*IrCl2]2 in a ratio of 1:1 in the presence of an excess of sodium acetate, a significant change of color was observed from orange to dark red, affording the dinuclear complexes 1a,b, respectively. The structures of 1a,b were confirmed by 1H NMR spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and single-crystal Xray crystallography (see below). It is interesting to note that the monocyclometalated product 1c (yield 43%) was obtained in the synthesis of complex 1b. This is the reason the yield of 1a (90%) is higher than that of 1b (52%). Complex 1c is soluble in ether and therefore can be easily isolated from the mixture of 1b and 1c. When [Cp*IrCl2]2 and 2,2′-bpe reacted in a ratio of 1.5:1, the major product was 1b (yield 90%). This means that the monocyclometalated product 1c can react with [Cp*IrCl2]2. The ESI-MS data confirm the structure of complexes 1a−c. The ESI mass spectra of 1a,b showed a molecular ion at m/z 691 [1a − Cl]+ and a molecular ion at m/z 871 [1b − Cl]+, respectively. The ESI mass spectrum of 1c showed an ion at m/ z 545 due to [1c]+ and a fragment ion at m/z 509 due to [1c − Cl]+. The 1H NMR spectra of 1a,b indicate that the two complexes have similar structures in solution. The similar Cp* group signals (δ 1.65 (1a) and 1.67 (1b) ppm) in the two complexes show identical environments of the Cp* groups. Coordination of the ligand to the metal centers are suggested

molecular structures of 1a,b have been determined by singlecrystal X-ray diffraction studies (Figure 1a,b). The M−N and M−C bond lengths and the C−M−N angle in the chelation ring are similar to those in related Cp*M (M = Rh, Ir) cyclometalated complexes.8−10 Interestingly, in 1a,b, only a cis conformation of the Cp* groups and Cl atoms is found, whereas most of the similar dinuclear complexes adopt a trans conformation. In complex 1b, the two Cl atoms had hydrogen bonds to the hydrogen atom of water, at a distance of 2.38(7) Å (Figure 1b). The 1H NMR spectrum of 1c showed two different sets of 2,2′-bpe signals, in a 1:1 ratio, indicating a monocyclometalated complex with two single proton signals at δ 7.40 and 1.50 due to the alkene group and Cp*, respectively. The molecular structure of 1c was confirmed by X-ray crystallographic analysis (Figure 1c). The Ir(1)−C(7) and Ir(1)−N(1) bond lengths and the N(1)−Ir(1)−C(7) angle are similar to those of 1a,b. Synthesis and Characterization of Tetranuclear Macrocycles. To construct macrocycles, we used the dinuclear cyclometalated species 1a,b as building blocks. After treatment with AgOTf, 1a,b can react with bridging ligands (pyrazine, 4,4′-bipyridine, or 4,4′-bpe) in a 1:1 molar ratio at room temperature, affording 2a−4a and 2b−4b, respectively (Scheme 4). 2a−4a and 2b−4b were obtained in high yields. The structures of complexes 2a−4a and 2b−4b were confirmed by 1H NMR, ESI-MS, and elemental analyses.

RESULTS AND DISCUSSION Dinuclear Cyclometalated Complexes 1a,b. As shown in Scheme 3, when 1,2-bis(2-pyridyl)ethylene (2,2′-bpe) was

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On the basis of our previous studies,10c,d we propose three possible isomers for 2b (Figure 3). The cis dinuclear precursor

Scheme 4. Preparation of Tetranuclear Complexes 2a−4a and 2b−4b

Figure 3. (top) Three proposed structures of isomers of 2b. (bottom) 1 H NMR spectrum of 2b in CDCl3, Circles (red) and diamonds (blue) correspond to different isomers.

The ESI-MS data indicated that complexes 2a−4a and 2b− 4b are configurationally stable in solution. The experimental peaks were in good agreement with their theoretical distributions: e.g., [2b − OTf]+ (m/z 2277, Figure 2).

molecules 1a,b are chiral with either R,R or S,S chirality at the two metal centers. Therefore, the tetranuclear compounds can then form as either meso R,R-S,S or racemic R,R-R,R/S,S-S,S isomers. Due to the robust nature of the cyclometalated dinuclear fragments, the configurations of the fragment cannot transform after the formation of the metallamacrocycles. The formation of these three isomers is confirmed by X-ray crystallographic analysis (see below). Molecular Structures. Although reliable methods to isolate pure isomers have yet to be developed, for the case of 4a, we managed to obtain suitable single crystals of both meso R,R-S,S and racemic R,R-R,R/S,S-S,S isomers, by manually picking out the crystals from mixtures of two kinds of crystals (yellow and orange) grown from the solutions of the raw products. For 3b and 4b, only suitable single crystals of meso R,R-S,S isomers were obtained. Attempts to obtain diffraction-grade single crystals of 2a,b and 3a were not successful. Crystal Structure of (R,R)-(S,S)-3b. (R,R)-(S,S)-3b crystallized in the triclinic space group P1̅. According to the crystal structure, the expected tetranuclear macrocycle is formed, with the dimensions of 11.31 and 4.89 Å (Ir...Ir nonbonding distances, Figure 4a). Each Ir atom is coordinated by two N atoms from the pyridyl group and one C atom from the ethylene group. The Ir(1)−C(7) and Ir(1)−N(1) bonds are longer than those of 1b, with distances of 2.074(9) and 2.111(8) Å, respectively. The N(1)−Ir(1)−N(3) and C(7)− Ir(1)−N(3) angles are 86.5(3) and 89.4(3)°, respectively. The structure also shows that the 4,4′-dipyridyl bridges are twisted, with a distortion angle (33.7°), which might be due to a steric hindrance effect. The cavity of the macrocycle of (R,R)-(S,S)-3b was extended through an axis, forming a rectangular channel (Figure 4b). Further examinations of the crystal structure provide insight into why the channel is formed. Four OTf anions were found between two neighboring layers of the macrocycles, linked with hydrogen bonds (Figure 4c). Among four OTf anions, two anions were inside the channel formed by macrocycles with one O atom bonding to the hydrogen atom of the Cp* group (bonding distance 2.49 Å) and one O atom bonding to one pyridine group of 2,2′-bpe (bond distance 2.35 Å). The other

Figure 2. Calculated (bottom) and experimental (top) ESI-MS spectra for [2b − OTf]+ of 2b.

Interesting splittings of the 1H NMR signals were found in the cyclometalated tetranuclear complexes. For example, the 1H NMR spectrum of 2b in CDCl3 shows the presence of two kinds of Cp*Ir species. Two sets of signals were observed in a 4:3 ratio at δ 8.90−8.74 (two doublets), 7.94−7.83 (two triplets), 7.80−7.75 (two singlets), 7.63−7.53 (two doublets), and 7.20−7.13 (two triplets) and were assigned to Ha, Hc, He, Hd, and Hb, respectively. The splittings of the NMR spectrum indicate the existence of two kinds of structures. Similar splittings in NMR were also found for other cyclometalated macrocycles in CD3OD or CDCl3. However, the 1H NMR spectrum of 4b in [D6]DMSO shows that the signal splittings disappear after heating for a few seconds, accompanied by a significant color change from red to yellow. Furthermore, the 1H NMR spectrum shows signals of free 4,4′bpe ligands. These facts suggest that the structure of the tetranuclear macrocycle is destroyed by heating in DMSO solution. 589

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Interestingly, one-dimentional molecular tunnels are formed by four neighboring 4a cations, which can extend in the crystal packing (Figure 6d). Four OTf anions are trapped in each layer

Figure 4. (R,R)-(S,S)-3b: (a) ORTEP view of the cationic part; (b) crystal stacking structure; (c) hydrogen bond between OTf anions and two neighboring macrocycles; (d) the anion channel-stacking architecture (space-filling model). H atoms are omitted for clarity except for those involving hydrogen bonds. Ellipsoids are shown at the 30% probability level. Color code: C, gray; N, blue; Ir, pink; O, red; F, green; S, yellow; H, light blue. Selected bond lengths (Å) and angles (deg): Ir(1)−C(7) 2.074(9), Ir(1)−N(1) 2.111(8), Ir(1)−N(3) 2.122(7); C(7)−Ir(1)−N(1) 77.6(3), C(7)−Ir(1)−N(3) 89.4(3), N(1)−Ir(1)−N(3) 86.5(3).

Figure 6. Molecular tunnel in the crystal stacking of (R,R)-(S,S)-4a: (a) front view; (b) side view; (c) hydrogen bonds between OTf anions and the neighboring cationic parts; (d) space-filling model. H atoms are omitted for clarity, except for those involving hydrogen bonds. Color code: C, gray; N, blue; Rh, orange; O, red; F, green; S, yellow.

of four 4a cations (Figure 6a,b). O atoms of the two outside OTf anions connect to the Cp*, 4,4′-bpe, and 2,2′-bpe groups of three neighboring macrocycles by five hydrogen bonds, with a distance ranging from 2.36 to 2.52 Å. As for the two inside OTf anions, only hydrogen bonds to the hydrogen atom of one pyridine group of 4,4′-bpe are found, at a distance of 2.53 Å (Figure 6c). The structure of (S,S)-(S,S)-4a is unsymmetrical (Figure 7). The size of the unsymmetrical tetranuclear macrocycle (4.88 ×

two OTf anions connect to the Cp* group of two neighboring macrocycles by one O atom and one F atom, with distances of 2.59 and 2.53 Å, respectively. Crystal Structure of 4a. Two sets of colored crystals suitable for X-ray single diffraction analysis were isolated as yellow and orange crystals, respectively. The resulting X-ray analyses revealed that the yellow crystals correspond to the meso R,RS,S isomer, whereas the orange crystals are the racemic R,RR,R/S,S-S,S isomer. (R,R)-(S,S)-4a has a symmetrical tetranuclear rectangular structure with dimensions of 4.86 × 13.64 Å as defined by the rhodium centers (Figure 5). The bond lengths and angles of the cyclometalated rings were similar to those of 3a. The two 4,4′-bpe ligands are parallel to each other at a distance of 5.22 Å, which is longer than the Rh...Rh separation of 4.86 Å.

Figure 7. Molecular structure of the complex (S,S)-(S,S)-4a. OTf anions, H atoms, and guest molecules are omitted for clarity. Selected bond lengths (Å) and angles (deg): Rh(1)−C(7) 2.047(7), Rh(1)− N(1) 2.097(6), Rh(1)−N(5) 2.148(5); C(7)−Rh(1)−N(1) 77.5(3), C(7)−Rh(1)−N(5) 89.7(2), N(1)−Rh(1)−N(5) 90.3(2).

13.64 Å) is similar to that of the meso R,R-S,S isomer. Because of the unsymmetrical structure, the two 4,4′-bpe ligands are almost in a vertical configuration. Hydrogen bonding between OTf anions and two neighboring macrocycles was observed (Figure 8a). Two OTf anions are trapped inside the cavity formed by the racemic R,R-R,R/S,S-S,S enantiomer pair. Two hydrogen bonds are formed between

Figure 5. Molecular structure of the complex (R,R)-(S,S)-4a. OTf anions; H, atoms, and guest molecules are omitted for clarity. Selected bond lengths (Å) and angles (deg): Rh(1)−C(7) 2.049(4), Rh(1)− N(1) 2.083(3), Rh(1)−N(3) 2.125(3); C(7)−Rh(1)−N(1) 77.68(14), C(7)−Rh(1)−N(3) 89.39(14), N(1)−Rh(1)−N(3) 86.21(13). 590

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complex has a rectangular structure with Ir...Ir lengths of 4.89 and 13.61 Å. Parts b−d of Figure 9 show the molecular tunnel of (R,R)-(S,S)-4b in crystal stacking; they are almost the same as that of (R,R)-(S,S)-4a.

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CONCLUSION In summary, we have used the ligand 1,2-bis(2-pyridyl)ethylene as the building block to construct organometallic macrocycles (2a−4a, 2b−4b) via double-site olefinic C−H activation under mild conditions. Double-site C−H activation on the olefinic CC bond was confirmed by single-crystal X-ray diffraction studies, 1H NMR spectroscopy, and ESI-MS. The dinuclear cyclometalated complexes 1a,b were obtained. The monocyclometalated complex 1c was obtained in the synthesis of complex 1b. Isomers were obtained in both dinuclear species and tetranuclear complexes. The results may help to better understand self-assembly reactions. Furthermore, hydrogen bonds between macrocycles and OTf anions were captured in detail, which were essential for the maintenance of tunnel structures of macrocycles in crystal packing. Functionalizing C−H bonds in organic chemistry is very important. Further studies on the application of C−H activation based on the iridium and rhodium fragment systems are currently under way in our laboratory.

Figure 8. (R,R)-(R,R)-/(S,S)-(S,S)-4a: (a) hydrogen bond between OTf anions and two neighboring cationic parts (C, gray; N, blue; Rh, orange; O, red; F, green; S, yellow; H, light blue); (b) molecular structures of the enantiomers (S,S)-(S,S)-4a (blue) and (R,R)-(R,R)4a (orange); (c) intermolecular π−π interactions between Cp* rings and 4,4′-bpe ligands; (d) crystal stacking structure (space-filling representation). H atoms are omitted for clarity, except for those involving hydrogen bonds.

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4,4′-bpe and two different O atoms, with distances of 2.57 and 2.60 Å. Each macrocycle also links another OTf anion by a hydrogen bond between the F atom and 4,4′-bpe at a distance of 2.56 Å. Moreover, the packing is further enforced by intermolecular π−π interactions between Cp* groups of one macrocycle and the 4,4′-bpe ligand of the neighboring molecule, at a distance of about 3.62 Å (Figure 8c,d). Crystal Structure of (R,R)-(S,S)-4b. The structure of (R,R)(S,S)-4b is similar to that of (R,R)-(S,S)-3b and (R,R)-(S,S)-4a. As shown in Figure 9a, the cation part of (R,R)-(S,S)-4b contains four hexacoordinated iridium centers, two bridging 1,2-bis(2-pyridyl)ethylene ligands, and two 4,4′-bpe units. The

EXPERIMENTAL SECTION

General Procedures. All reactions described below were carried out under nitrogen. However, once the reactions were completed, the further workups were done without precaution, as the compounds are air-stable. Solvents were purified by standard methods prior to use. The starting materials [Cp*MCl2]2 (M = Rh, Ir)12 were prepared by literature methods, while other chemicals were obtained commercially and used without further purification. Elemental analyses were performed on an Elementar III Vario EI analyzer. The 1H NMR spectra (400 MHz) were measured on a Bruker DMX-500 spectrometer in CDCl3 (δ 7.26) or CD3OD (δ 3.31) solution. ESIMS spectra were recorded on a Micro TOF II mass spectrometer using electrospray ionization. Preparation of 1a. A mixture of [Cp*RhCl2]2 (62.0 mg, 0.1 mmol), NaOAc (49.6 mg, 0.60 mmol), and 1,2-bis(2-pyridyl)ethylene (18.2 mg, 0.1 mmol) was stirred at 40 °C in 20 mL of dichloromethane for 24 h. The mixture was filtered through Celite and evaporated to dryness. The solid obtained was washed with ether. Dinuclear complex 1a was isolated as an orange solid. Data for 1a. Orange, yield 90%. Anal. Calcd for C32H38Rh2N2Cl2: C, 52.84, H 5.27; N, 3.85. Found: C, 52.93; H, 5.26, N, 3.84. 1H NMR (400 MHz, CDCl3, ppm): δ 8.59 (d, 2H, Py-H), 7.67 (d, 2H, Py-H), 7.57 (m, 2H, Py-H), 6.87 (m, 2H, Py-H), 1.65 (s, 30H, Cp*-H). MS (ESI): m/z 691 [M − Cl]+. Preparation of 1b,c. The reaction was carried out as for 1a, using [Cp*IrCl2]2 (80.0 mg, 0.1 mmol), NaOAc (49.6 mg, 0.60 mmol), and 1,2-bis(2-pyridyl)ethylene (18.2 mg, 0.1 mmol) in 20 mL of CH2Cl2 at 40 °C for 12 h. The mixture was filtered through Celite and evaporated to dryness. The solid obtained was washed with ether. Dinuclear complex 1b was isolated as a dark red solid. Monocyclometalated compound 1c was obtained in ether and was isolated as a red-orange solid. Data for 1b. Dark red, yield 52%. Anal. Calcd for C32H38Ir2N2Cl2: C, 42.42; H, 4.23; N, 3.09. Found: C, 42.53; H, 4.24; N, 3.08. 1H NMR (400 MHz, CDCl3, ppm): δ 8.52 (d, 2H, Py-H), 7.76 (d, 2H, Py-H), 7.48 (m, 2H, Py-H), 6.80 (m, 2H, Py-H), 1.69 (s, 30H, Cp*H). MS (ESI): m/z 871 [M − Cl]+. Data for 1c. Red, yield 43%. Anal. Calcd for C22H24IrN2Cl: C, 48.56; H, 4.45; N, 5.15. Found: C, 48.43; H, 4.44; N, 5.08. 1H NMR (400 MHz, CDCl3, ppm): δ 8.55 (m, 2H, Py-H), 7.82 (d, 1H, Py-H), 7.62 (t, 1H, Py-H), 7.49 (t, 1H, Py-H), 7.40 (s, 1H, CHC), 7.38 (d,

Figure 9. (R,R)-(S,S)-4b: (a) ORTEP view of the cationic part; (b−d) molecular tunnel in crystal stacking (b) side view, (c) front view, and (d) view of the stacking unit. Selected bond lengths (Å) and angles (deg): Ir(1)−C(7) 2.110(13), Ir(1)−N(1) 2.087(11), Ir(1)−N(3) 2.152(11); C(7)−Ir(1)−N(1) 77.0(5), C(7)−Ir(1)−N(3) 89.2(5), N(1)−Ir(1)−N(3) 84.0(4). H atoms are omitted for clarity. Color code: C, gray; N, blue; Ir, pink; O, red; F, green; S, yellow. 591

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(m, 12H, 4,4′-bpe-H), 1.70 (s, 60H, Cp*-H). MS (ESI): m/z 2481 [M − OTf]+. Crystal Structure Determinations.13 All single crystals were obtained from slow diffusion of diethyl ether into CH3OH or CH2Cl2 solutions of the corresponding compounds. Data were collected on a CCD-Bruker SMART APEX system. The data collection was carried out using Mo Kα radiation (λ = 0.71073 Å). The intensity data were corrected for absorption. The structures were solved by direct methods, using Fourier techniques, and refined on F2 by a full-matrix least-squares method. All of the calculations were carried out with the SHELXTL program.14 A summary of the crystallographic data and selected experimental information are given in the Supporting Information (Part III). In the asymmetric unit of 1b, one DFIX instruction was used to restrain the O−H bond length of the water molecule. Therefore, there was one restraint in the data. In the asymmetric unit of (R,R)-(S,S)-3b, there were disordered solvents (one methanol and one water molecules) which could not be restrained properly. Therefore, the SQUEEZE algorithm was used to omit them. Iridium atoms were slightly disordered, and they were divided into two parts (90:10). One of the two triflate anions was also disordered, and it was also divided into two parts (64:36). O6, O6′, and C45 were refined isotropically, and other non-hydrogen atoms were refined anisotropically. Twenty-six DFIX, 1 DELU, and 2 ISOR instructions were used to restrain the disordered anions so that there were 39 restraints in the data. The hydrogen of the methanol molecule could not be found, and other hydrogen atoms were placed in calculated positions. In the asymmetric unit of (R,R)-(S,S)-4a, there were disordered solvents (two diethyl ether and one water molecules) which could not be restrained properly. Therefore, the SQUEEZE algorithm was used to omit them. In the asymmetric unit of (R,R)-(R,R)-/(S,S)-(S,S)-4a, there were three disordered water molecules which could not be restrained properly. Therefore, the SQUEEZE algorithm was used to omit them. Atoms F10−F12, C89, C91, and C92 were refined isotropically, and other non-hydrogen atoms were refined anisotropically. Fifteen DFIX and 5 ISOR instructions were used to restrain the anions so that there were 45 restraints in the data. In the asymmetric unit of (R,R)-(S,S)-4b, there were disordered solvents (three water molecules) which could not be restrained properly. Therefore, the SQUEEZE algorithm was used to omit them. One of the four triflate anions was disordered, and it was divided into two parts (59:41). F11, O11, O12, O11′, F11′, F12′, and C93 were refined isotropically, and other non-hydrogen atoms were refined anisotropically. Twenty-nine ISOR, 16 DFIX, and 2 DELU instructions were used so that there were 192 restraints in the data. The hydrogen atoms of the methanol molecules could not be found, and other hydrogen atoms were placed in calculated positions.

1H, Py-H), 7.11 (t, 1H, Py-H), 6.90 (t, 1H, Py-H), 1.50 (s, 15H, Cp*H). MS (ESI): m/z 545 [M]+, 509 [M − Cl]+. Synthesis of Complexes 2a−4a and 2b−4b. Ag(CF3SO3) (28.2 mg, 0.11 mmol, 1.1 equiv) was added to a solution of the corresponding dinuclear complex 1a or 1b (0.05 mmol, 0.5 equiv, M = Rh (31.3 mg), M = Ir (45.3 mg)) in CH3OH (15 mL) at room temperature, and the mixture was stirred in the dark for 12 h, followed by filtration to remove insoluble materials. pyrazine (4.8 mg, 0.06 mmol, 0.6 equiv)/bpy (9.4 mg, 0.06 mmol, 0.6 equiv)/4,4′-bpe (11.0 mg, 0.06 mmol, 0.6 equiv) was added to the filtrate, and the mixture was stirred for 12 h. The solution was filtered through Celite and evaporated to dryness. The product was crystallized from CH3OH/ ether to give 2a−4a and 2b−4b. Data for 2 a. Yellow, yield 87%. Anal. Calcd for C76H84Rh4N8O12F12S4: C, 44.11; H, 4.09; N, 11.02. Found: C, 44.25; H, 4.07; N, 11.14. 1H NMR (400 MHz, CD3OD, ppm): δ 8.89−8.80 (d, 4H, Py-H), 8.00−7.94 (m, 4H, Py-H), 7.75 (s, 8H, pyrazine-H), 7.46−7.30 (m, 8H, Py-H), 1.66 (s, 60H, Cp*-H). 1H NMR (400 MHz, CDCl3, ppm): δ 8.87−8.81 (d, 4H, Py-H), 7.95− 7.80 (m, 16H, Py and bpy-H), 7.62−7.61 (d, 8H, bpy-H), 7.30−7.26 (t, 4H, Py-H), 1.67 (s, 60H, Cp*-H). 1H NMR (400 MHz, CDCl3, ppm): R,R-S,S δ 8.97 (d, 4H, Py-H), 7.90 (t, 4H, Py-H), 7.75 (s, 8H, pyrazine-H), 7.45 (d, 4H, py-H), 7.25 (t, 4H, Py-H), 1.62 (s, 60H, Cp*-H); R,R-R,R/S,S-S,S δ 8.81 (d, 4H, Py-H), 8.02 (t, 4H, Py-H), 7.73 (s, 8H, pyrazine-H), 7.51 (d, 4H, py-H), 7.19 (t, 4H, Py-H), 1.63 (s, 60H, Cp*-H). MS (ESI): m/z 1919 [M − OTf]+. Data for 2b. Dark red, yield: 66%. Anal. Calcd for C76H84Ir4N8O12F12S4: C, 37.62; H, 3.49; N, 4.62. Found: C, 37.45; H, 3.47; N, 4.64. 1H NMR (400 MHz, CD3OD, ppm): δ 8.83−8.73 (d, 4H, Py-H), 7.96−7.88 (m, 4H, Py-H), 7.74 (s, 8H, pyrazine-H), 7.57−7.48 (d, 4H, Py-H), 7.34−7.26 (m, 4H, Py-H), 1.67 (s, 60H, Cp*-H). 1H NMR (400 MHz, CDCl3, ppm): (R,R)-(S,S) δ 8.90 (d, 4H, Py-H), 7.83 (t, 4H, Py-H), 7.80 (s, 8H, pyrazine-H), 7.53 (d, 4H, py-H), 7.20 (t, 4H, Py-H), 1.64 (s, 60H, Cp*-H); R,R-R,R/(S,S)-(S,S) δ 8.74 (d, 4H, Py-H), 7.94 (t, 4H, Py-H), 7.75 (s, 8H, pyrazine-H), 7.63 (d, 4H, py-H), 7.13 (t, 4H, Py-H in), 1.65 (s, 60H, Cp*-H). MS (ESI): m/z 2277 [M − OTf]+. Data for 3 a. Yellow, yield 88%. Anal. Calcd for C88H92Rh4N8O12F12S4: C, 47.58; H, 4.17; N, 5.04. Found: C, 47.37; H, 4.15; N, 5.06. 1H NMR (400 MHz, CD3OD, ppm): δ 9.05−8.99 (d, 4H, Py-H), 8.04−8.00 (m, 4H, Py), 7.96−7.90 (d, 8H, bpy-H), 7.83−7.75 (d, 4H, Py-H), 7.38−7.33 (m, 4H, Py-H), 7.32−7.26 (d, 8H, bpy-H), 1.67 (s, 60H, Cp*-H). MS (ESI): m/z 2072 [M − OTf]+. Data for 3b. Yellow, yield 70%. Anal. Calcd for C88H92Ir4N8O12F12S4: C, 40.99; H, 3.60; N, 4.35. Found: C, 40.75; H, 3.67; N, 4.31. 1H NMR (400 MHz, CD3OD, ppm): δ 9.01−8.93 (d, 4H, Py-H), 8.04−7.89 (m, 16H, Py-H and bpy-H), 7.35−7.23 (m, 12H, Py-H and bpy-H), 1.70 (s, 60H, Cp*-H). 1H NMR (400 MHz, CDCl3, ppm): δ 8.87−8.81 (d, 4H, Py-H), 7.95−7.80 (m, 16H, Py and bpy-H), 7.62−7.61 (d, 8H, bpy-H), 7.30−7.26 (t, 4H, Py-H), 1.67 (s, 60H, Cp*-H). MS (ESI): m/z 2429 [M − OTf]+. Data for 4a. Orange, yield 70%. Anal. Calcd for C92H96Rh4N8O12F12S4: C, 48.60; H, 4.26; N, 4.93. Found: C, 48.45; H, 4.27; N, 5.04. 1H NMR (400 MHz, CD3OD, ppm): R,R-S,S δ 9.04 (d, 4H, Py-H), 8.06 (t, 4H, Py-H), 7.85 (d, 4H, Py-H), 7.75 (d, 8H, 4,4′-bpe-H), 7.39 (t, 4H, Py-H), 7.21 (d, 8H, 4,4′-bpe-H), 7.14 (s, 4H, ethylene), 1.70 (s, 60H, Cp*-H); R,R-R,R/S,S-S,S δ 9.00 (d, 4H, PyH), 8.06 (t, 4H, Py-H), 7.80 (d, 4H, Py-H), 7.75 (d, 8H, 4,4′-bpe-H), 7.38 (t, 4H, Py-H), 7.20 (d, 8H, 4,4′-bpe-H), 7.13 (s, 4H, ethylene), 1.70 (s, 60H, Cp*-H). 1H NMR (400 MHz, CDCl3, ppm): R,R-S,S δ 8.93 (d, 4H, Py-H), 7.95 (t, 4H, Py-H), 7.63 (m, 12H, Py-H and 4,4′bpe-H), 7.37 (t, 4H, Py-H), 7.29 (d, 8H, 4,4′-bpe-H), 7.13 (s, 4H, ethylene) 1.68 (s, 60H, Cp*-H); R,R-R,R/S,S-S,S δ 8.90 (d, 4H, PyH), 7.95 (t, 4H, Py-H), 7.64 (m, 12H, Py-H and 4,4′-bpe-H), 7.38 (t, 4H, Py-H), 7.32 (d, 8H, 4,4′-bpe-H), 7.17 (s, 4H, ethylene), 1.68 (s, 60H, Cp*-H). MS (ESI): m/z 2124 [M − OTf]+. Data for 4b: Orange, yield 70%. Anal. Calcd for C92H96Ir4N8O12F12S4: C, 42.00; H, 3.68; N, 4.26. Found: C, 42.25; H, 3.72; N, 4.24. 1H NMR (400 MHz, CD3OD, ppm): δ 9.02−8.95 (d, 4H, Py-H), 8.01−7.82 (m, 16H, Py-H and 4,4′-bpe-H), 7.21−7.15

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ASSOCIATED CONTENT

S Supporting Information *

Figures giving 1H NMR spectra and ESI-MS spectra for all compounds and CIF files and a table giving crystallographic data for 1a−c, (R,R)-(S,S)-3b, (R,R)-(S,S)-4a, (R,R)-(R,R)-/ (S,S)-(S,S)-4a, and (R,R)-(S,S)-4b. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Tel: +86-21-65643776. Fax: +86-21-65641740. E-mail: gxjin@ fudan.edu.cn. Notes

The authors declare no competing financial interest. 592

dx.doi.org/10.1021/om4011559 | Organometallics 2014, 33, 587−593

Organometallics

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Article

(9) (a) Davies, D. L.; Al-Duaij, O.; Fawcett, J.; Giardiello, M.; Hilton, S. T.; Russell, D. R. Dalton Trans. 2003, 4132. (b) Davies, D. L.; Donald, S. M. A.; Al-Duaij, O.; Fawcett, J.; Little, C.; Macgregor, S. A. Organometallics 2006, 25, 5976. (c) Davenport, A. J.; Davies, D. L.; Fawcett, J.; Russell, D. R. J. Organomet. Chem. 2006, 691, 2221. (d) Davies, D. L.; Donald, S. M. A.; Al-Duaij, O.; Macgregor, S. A.; Pölleth, M. J. Am. Chem. Soc. 2006, 128, 4210. (10) (a) Han, Y.-F.; Li, H.; Weng, L.-H.; Jin, G.-X. Chem. Commun. 2010, 46, 3556. (b) Han, Y.-F.; Jin, G.-X. Chem. Asian J. 2011, 6, 1348. (c) Li, H.; Han, Y.-F.; Jin, G.-X. Dalton Trans. 2011, 40, 4982. (d) Li, H.; Han, Y.-F.; Jin, G.-X. J. Organomet. Chem. 2011, 696, 2129. (e) Han, Y.-F.; Lin, Y.-J.; Hor, T. S. A.; Jin, G.-X. Organometallics 2012, 31, 995. (11) Yu, W.-B.; Han, Y.-F.; Lin, Y.-J.; Jin, G.-X. Chem. Eur. J. 2011, 17, 1863. (12) White, C.; Yates, A.; Maitlis, P. M. Inorg. Synth 1992, 29, 228. (13) Single crystals of (R,R)-(R,R)/(S,S)-(S,S)-4a were studied by Xray diffraction at room temperature. (14) (a) Sheldrick, G. M. SHELXL-97; University of Göttingen, Göttingen, Germany, 1997. (b) Sheldrick, G. M. SHELXL-2013; University of Göttingen, Göttingen, Germany, 2013.

ACKNOWLEDGMENTS This work was supported by the National Science Foundation of China (91122017, 21374019), the Shanghai Science and Technology Committee (13JC1400600, 13DZ2275200), and the Program for Changjiang Scholars and Innovative Research Team in University (IRT1117).

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dx.doi.org/10.1021/om4011559 | Organometallics 2014, 33, 587−593