Synthesis of Fused Metallaaromatics via Intramolecular C–H

Article pubs.acs.org/Organometallics

Synthesis of Fused Metallaaromatics via Intramolecular C−H Activation of Thiophenes Qingde Zhuo, Xiaoxi Zhou, Huijun Kang, Zhiyong Chen, Yuhui Yang, Feifei Han, Hong Zhang,* and Haiping Xia* State Key Laboratory of Physical Chemistry of Solid Surfaces and Collaborative Innovation Center of Chemistry for Energy Materials (iChEM) and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People’s Republic of China S Supporting Information *

ABSTRACT: A convenient method to synthesize novel fused ruthena-/osmacycles via intramolecular C−H activation of thiophenes has been developed. Treatment of HCCCH(OH)R (R = 2-thienyl) with RuCl2(PPh3)3 or OsCl2(PPh3)3 afforded hydroxyl-coordinated metal vinyl compounds 1 and 4. Reaction of 1/4 with acid produced metal alkenylcarbene complexes 3/5, which can further convert to the corresponding fused metallaaromatics 2/7 via the C(sp2)−H activation of the thienyl groups. 7 is the first example of a metallabenzyne with a fused five-membered ring (thiophene ring). These fused metallaaromatics are thermally stable both in solution and in the solid state in air. The X-ray crystallographic analysis, NMR spectra, and DFT calculations all suggest that these fused metallaaromatics (2 and 7) show aromatic character.

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INTRODUCTION As a distinct class of aromatics, metallaaromatics have fascinated chemists since they were predicted theoretically by Thorn and Hoffmann in 1979.1 In the past few decades, a wide variety of metallaaromatics have been successfully isolated and chracterized.2−4 Most well-characterized metallaaromatics are monocyclic metallaaromatics, especially metallabenzenes2 and metallabenzynes.3 A number of fused metallabenzenes, such as metallabenzene, with fused five-membered rings or sixmembered rings have also been reported in recent years.4 In contrast, fused metallabenzynes are limited to only one series, i.e. osmanaphthalynes,5 which have been less well-developed. Although a number of routes allowed the isolation of fused metallaaromatic structures with various transition metals,5−8 there is only one available synthetic route to the formation of fused metallaaromatics, i.e. metallabenzofurans,9 with different metal centers that has been reported. In 2009, we reported a facile method to synthesize osmanaphthalene and osmanaphthalyne by the reaction of OsCl2(PPh3)3 and propargyl alcohol, i.e. HCCHC(OH)Ph. The intramolecular C−H activation of the phenyl group was suggested as the key step for this transformation.5b Inspired by these experimental results, we investigated the intramolecular C−H activation of propargyl alcohol with other aryl groups in the hope of obtaining the corresponding fused metallaaromatics. In this work, we report a new synthetic route for the formation of fused metallaaromatics via intramolecular C−H activation of thiophenes. The investigation provides the isolation of novel fused ruthenacycles and fused osmacycles with aromatic character, including the first example of metallabenzyne with a fused five-membered ring (thiophene ring). A preliminary report of the ruthenabenzothiophene has been published previously.10 © XXXX American Chemical Society

RESULTS AND DISCUSSION Synthesis of Bis(ruthenabenzothiophene) 2. As shown in Scheme 1, a mixture of RuCl2(PPh3)3, 1-(thiophen-2Scheme 1. Synthesis of Bis(ruthenabenzothiophene) 2 via Intramolecular C−H Activation of Thiophene

yl)prop-2-yn-1-ol, and excess PPh3 was stirred at room temperature in tetrahydrofuran (THF) for 24 h to give the hydroxyl-coordinated ruthenium vinyl compound 1. Treatment of compound 1 with excess HCl for 2 h led to bis(ruthenabenzothiophene) 2. It is a rare example of fused metallaaromatics with second-row transition-metal centerSpecial Issue: Organometallics in Asia Received: January 31, 2016

A

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form several unidentified species on heating at 60 °C. However, when a solution of complex 6 was heated in an air atmosphere at 60 °C for 6 h, fused osmabenzyne 7 was produced by intramolecular C−H activation of thiophene. Notably, 7 is the first example of a metallabenzyne with a fused five-membered ring (thiophene ring), providing an addition to the rare examples of fused metallabenzynes.5 Thus, the route to obtain fused metallaaromatics by intramolecular C−H activation of thiophene was successfully applied to the synthesis of a fused metallaaromatic with an osmium center. It is the first available route which could synthesize fused metal nonbridged aromatics with different metal centers. Moreover, the isolation and characterization of the key intermediates, i.e. cyclic osmium carbene complexes 5 and 6, provided new insight into the synthetic route. Proposed Mechanism for the Formation of Complexes 2 and 7. On the basis of the well-characterized intermediates, the final products, and the reported analogous mechanism for the formation of osmanaphthalene and osmanaphthalyne,5b a plausible mechanism for the formation of 2 and 7 is shown in Scheme 3. Initially, the dissociation of

s.6c,8d,9a When the reaction temperature of compound 1 and HCl was decreased to 0 °C, the thienyl-coordinated ruthenium alkenylcarbene complex 3 was detected by in situ NMR. Complex 3 was sensitive to air and readily decomposed in an air atmosphere. In addition, 3 could easily transform to complex 2 via intramolecular C−H activation of thiophene, which strongly suggested that 3 is a key intermediate for the transformation of 1 to 2. Synthesis of Fused Osmabenzyne 7. In our previous studies, osmium complexes were often more stable in comparison with their ruthenium counterparts,11 which are suitable models to get more information on the analogous reactive ruthenium intermediates in transformations.12 In addition, synthetic routes for preparing fused metallaaromatics with different metal centers are rare.9 Thus, we investigated the reaction of 1-(thiophen-2-yl)prop-2-yn-1-ol with OsCl2(PPh3)3, to further illuminate the reaction mechanism and attempt to obtain fused metallaaromatics with metal centers other than ruthenium. As shown in Scheme 2, treatment of OsCl2(PPh3)3 Scheme 2. Synthesis of Fused Osmabenzyne 7 via Intramolecular C−H Activation of Thiophene

Scheme 3. Proposed Mechanism for the Formation of 2 and 7

with 1-(thiophen-2-yl)prop-2-yn-1-ol in THF led to the formation of hydroxyl-coordinated osmium vinyl compound 4. In the presence of HBF4 and excess NH4Cl, compound 4 could cleanly convert to the cyclic osmacarbene complex 5 within 5 min at room temperature, which adopted a cis configuration of the two phosphine ligands. Herein, excess NH4Cl is necessary for the transformation and complex 5 could not be cleanly obtained when compound 4 was treated with HBF4 alone. It is possible that the addition of HBF4 may facilitate the dissociation of the chloride ligands,13 leading to the decomposition of 5. Alternatively, the addition of HCl to compound 4 could produce the exact same complex as 5 except for the different counteranion. A dichloromethane solution of 5 could gradually convert to 6 under a N2 atmosphere at room temperature in several days. Complex 6 is an isomer of complex 5 with a mutually trans disposition of the two phosphine ligands. When excess PPh3 was added to a dichloromethane solution of 5, the conversion could be completed in 1 h and complex 6 was obtained in 91% yield. In this reaction, PPh3 may promote the substitution reaction of the chloride ligand at the axial direction and thus accelerate the cis to trans isomerization. As expected, complex 6 was more stable than its ruthenium counterpart 3. It could persist in dichloroethane at room temperature under a N2 atmosphere for several days, yet it gradually decomposed to

PPh3 ligand and the coordination of HCCCH(OH)R (R = 2-thienyl) to the metal center could led to the formation of the π-alkyne intermediate A. A nucleophilic addition reaction of the dissociated PPh3 to the coordinated alkyne could generate the hydroxyl-coordinated metal vinyl compounds 1 and 4. The hydroxyl group could be easily removed by acid, and then the metal alkenylcarbene complexes 5 and C were obtained. The following isomerization gave rise to the formation of complexes 3 and 6, which may further transform to the agostic form intermediate D by dissociation of the coordinated thienyl group. The following C−H activation of thiophene may B

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Å, falling in the Os−O bond length range of the reported hydroxyl-coordinated osmium complexes (2.060−2.402 Å).14 The remaining bond lengths of the osmacycle, C1−C2 (1.362(13) Å), C2−C3 (1.532(13) Å), and C3−O1 (1.471(11) Å), are comparable with those of the reported hydroxyl-coordinated osmium vinyl compound with a phenyl substituent.15 Consistent with its X-ray structure, the 31P NMR spectrum of 4 showed one CPPh3 signal and two OsPPh3 signals at 0.64, 7.07, and −4.05 ppm, respectively. In the 1H NMR spectrum, the resonance of H1 (12.36 ppm) appeared slightly downfield in comparison with that of the complex 1. The signals at 5.75 and 3.67 ppm were attributed to H3 and OH, respectively. Similar to the case for the ruthenium vinyl compound 1, attempts to characterize compound 4 by the 13C{1H} NMR spectrum failed due to its poor solubility in common organic solvents. Selected NMR spectroscopic data for compounds 1 and 4 are given in Table 2.

generate the hydrido metallabenzothiophene intermediate E. For the ruthenium metal center, the bis(ruthenabenzothiophene) 2 could be obtained through the loss of PPh3 and HCl under a N2 atmosphere. For the osmium metal center, E could be oxidized in the presence of O2 to produce 7 and H2O. The involvement of oxygen could facilitate the removal of the hydride ligand and the α-proton of E by transforming them to H2O, which has been demonstrated by DFT calculations in the analogous osmanaphthalyne system.5b Characterization of Ruthenacycle 1 and Osmacycle 4. The structures of metal vinyl compounds 1 and 4 were confirmed by X-ray diffraction (Figure 1, Table 1, and Figure

Table 2. Selected NMR Spectroscopic Data for 1 and 4 δ(1H) (ppm) 1 4

Table 1. Selected Bond Lengths (Å) and Angles (deg) for 1 and 4

M1−C1 M1−O1 C1−C2 C2−C3 C3−O1 O1−M1−C1 M1−C1−C2 C1−C2−C3 C2−C3−O1 C3−O1−M1

Bond Lengths 1.959(6) 2.214(4) 1.359(9) 1.514(10) 1.457(8) Bond Angles 77.8(2) 120.2(5) 118.9(5) 107.1(5) 114.0(4)

H1

H3

OH

MPPh3

CPPh3

11.06 12.36

6.46 5.75

2.02 3.67

60.25/55.84 7.07/−4.05

−3.69 0.64

Characterization of Ruthenacycle 3 and Osmacycles 5 and 6. The cyclic metal carbene complexes 3, 5, and 6 were characterized by NMR spectroscopy and high-resolution mass spectrometry or elemental analysis. Due to its relatively good stability, a crystal suitable for X-ray diffraction of complex 5 was obtained. Figure 2 clearly shows a view of complex 5. The X-ray diffraction study confirms that complex 5 contains an alkenylcarbene ligand. The sulfur atom of thienyl is coordinated to the metal center. The two phosphine ligands and two chloride ligands adopt the cis configuration mutually. As shown in Figure 2, the Os1−C1 bond length (1.941(5) Å) is in the

Figure 1. ORTEP representation of compound 4. Ellipsoids are given at the 50% probability level, and the hydrogen atoms in PPh3 have been omitted for clarity.

1 (M = Ru)

δ(31P) (ppm)

4 (M = Os) 1.983(8) 2.226(6) 1.362(13) 1.532(13) 1.471(11) 77.3(3) 120.9(7) 118.0(8) 106.7(7) 114.1(5)

a The X-ray structure of compound 1 is shown in the Supporting Information.

S1 in the Supporting Information). They have similar overall structural features in addition to the metal centers. With 4 as an example, the coordination geometry around the osmium center can be regarded as a distorted octahedron with a planar fivemembered ring arranged in the equatorial plane. The two phosphine ligands and the two chloride ligands are disposed mutually cis, respectively. The bond distance of Os1−C1 (1.983(8) Å) is within the range of Os−C single bond lengths (1.897−2.250 Å),14 and it is slightly longer than the metal− carbon bond distance of compound 1 (1.959(6) Å) due to the different metal centers. The Os1−O1 bond length is 2.226(6)

Figure 2. ORTEP representation of complex 5. Ellipsoids are given at the 50% probability level, and the counteranion and hydrogen atoms in PPh3 have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Os1−C1 1.941(5), Os1−S1 2.3618(12), C1−C2 1.459(6), C2−C3 1.383(6), C3−C4 1.425(7), C4−S1 1.720(5); S1−Os1−C1 86.13(14), Os1−C1−C2 130.9(3), C1−C2−C3 127.2(4), C2−C3−C4 126.5(4), C3−C4−S1 119.7(3), C4−S1−Os1 110.13(17). C

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Organometallics Table 3. Selected NMR Spectroscopic Data for 3, 5, and 6 δ(1H) (ppm) 3 5 6

δ(31P) (ppm)

H1

H3

H5

H6

H7

MPPh3

CPPh3

17.87 23.79 21.31

9.19 8.55 8.17

8.59 8.66 8.07

7.91 7.50 7.39

6.71 7.25 5.80

24.18 −23.64/−27.99 −19.45

11.79 23.88 26.17

range of Os−C double-bond lengths (1.775−2.144 Å).14 The Os1−S1 bond length is 2.3618(12) Å, which is comparable with that of the reported thienyl coordinated osmium complex (2.3543(11) Å).16 In agreement with the solid-state structure of 5, the 31P NMR spectrum showed two doublets of OsPPh3 at −23.64 and −27.99 ppm with a P−P coupling constant of 21.80 Hz. The singlet at 23.88 ppm was attributed to CPPh3. The characteristic downfield signal of the carbene proton (H1) was assigned at 23.79 ppm in the 1H NMR spectrum. The signal of H3 was observed at 8.55 ppm. The 13C{1H} NMR showed a characteristic downfield signal of the carbene carbon atom (C1) at 232.74 ppm. The remaining carbon atoms of the metallacycle were observed at 119.24 (C2), 140.42 (C3), 140.73 (C4), 148.41 (C5), 136.82 (C6), and 132.36 ppm (C7), respectively. In agreement with the trans configuration of the two phosphine ligands (OsPPh3), a singlet at −19.45 ppm in the 31P NMR spectrum of complex 6 was attributed to them. The signal of CPPh3 appeared at 26.17 ppm. In the 1H NMR spectrum of 6, the signal of the carbene proton (H1) was observed at 21.31 ppm. Similarly, the chemical shift of the αproton is more downfield in osmium complex 6 (21.31 ppm) than in its ruthenium counterpart 3 (17.87 ppm) (Table 3). The signals of H3, H5, H6, and H7 were observed at 8.17, 8.07, 7.39, and 5.80 ppm, respectively. In the 13C{1H} NMR spectrum, the signal of the carbene carbon atom (C1) was observed at 243.38 ppm. The 13C signals of the remaining carbon atoms of the metallacycle (C2, C3, C4, C5, C6, and C7) were observed at 113.14, 149.47, 115.21, 147.43, 126.76, and 137.86 ppm, respectively. Characterization of Bis(ruthenabenzothiophene) 2 and Fused Osmabenzyne 7. The thiophene fused metallaaromatics 2 and 7 were characterized by multinuclear NMR spectroscopy and elemental analysis. As shown in Table 4, the

Figure 3. ORTEP representation of complex 7. Ellipsoids are given at the 50% probability level, and the counteranion and hydrogen atoms in PPh3 have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Os1−C1 1.769(5), Os1−C5 2.075(5), C1−C2 1.385(7), C2−C3 1.416(7), C3−C4 1.385(7), C4−C5 1.426(7); C5−Os1−C1 82.4(2), Os1−C1−C2 150.7(4), C1−C2−C3 112.4(4), C2−C3−C4 122.2(5), C3−C4−C5 128.9(4), C4−C5−Os1 123.2(3).

the internal angles, which are close to the ideal values of 720 and 540°, respectively. The Os1−C1 bond length (1.769(5) Å) is slightly longer than those of the reported osmanaphthalynes5 but is still within the range of Os−C triple-bond lengths (1.671−1.845 Å).3b The bond lengths of the C−C bonds within the osmabenzyne unit (1.385(7)−1.426(7) Å) are within the range of aromatic C−C bond lengths and lack of significant alternation. The structural feature of 7 suggests its aromatic nature, which was further confirmed by the DFT calculations (vide infra). The structure of 7 was also characterized by multinuclear NMR spectroscopy. With the aid of 1H−13C HSQC and 1 H−13C HMBC, the protons H3, H6, and H7 could be assigned at 7.66, 7.06, and 7.17 ppm, respectively. In the 13 C{1H} NMR spectrum, the signal of the carbyne carbon atom (C1) was observed at 275.07 ppm, which is in accordance with that of the reported osmanaphthalynes.5b The signal corresponding to C5 appeared at 195.63 ppm. The 13C signals of the remaining carbons of the metallacycle were observed at 97.47 (C2), 154.46 (C3), 131.95 (C4), 144.09 (C6), and 149.91 (C7) ppm, respectively. The 31P{1H} NMR spectrum of 7 displayed the signals of CPPh3 and OsPPh3 at 15.30 and −9.47 ppm, respectively. Thermal Stabilities of Complexes 2 and 7. Our previously reported phosphonium-substituted metallaromatics exhibit remarkable stability toward air, water, and heat,

Table 4. Selected NMR Spectroscopic Data for 2 and 7 δ(1H) (ppm) 2 7

δ(31P) (ppm)

H1

H3

H6

H7

MPPh3

CPPh3

16.26

7.73 7.66

7.97 7.06

6.89 7.17

47.05 −9.47

18.69 15.30

ruthenabenzene fragments of complex 2 had NMR spectroscopic data similar to those of the reported monocyclic ruthenabenzenes.11b,17 In addition, consistent with the electrochemistry behavior of other bimetallic complexes containing trichloro bridges,5b,18 electronic communication between the ruthenium centers in 2 can be observed in its cyclic voltammogram (Figure S2 in the Supporting Information). Complex 7 was further defined by single-crystal X-ray diffraction analysis (Figure 3). The fused osmacycle moiety of 7 is planar, with the mean deviation from the least-squares plane being 0.0216 Å. Both the six-membered metallacycle and the fused thiophene ring are planar with 719.8 and 540° sums of D

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7′ were calculated to be −19.7 and −23.1 kcal mol−1, which are comparable to the ISE value of benzene (−33.2 kcal mol−1).6e The negative NICS and ISE values confirm the aromaticity of 2 and 7.

including osmabenzenes,7a,11a,19 osmapyridines,15,20 ruthenabenzenes,11b,17 osmanaphthalene,5b osmanaphthalyne,5b osmapentalynes,6e,21 and osmapentalenes.6g,22 Similarly, the metallaaromatic complexes 2 and 7 are not labile to air and water. Their solid and solution states could be stored at room temperature in air for several weeks without any decomposition. The solid-state thermal stability tests have been performed in air by heating for 5 h. As shown in Table 5, complexes 2 and 7 are persistent at 120 °C in air for 5 h but partially decomposed on treatment at 150 °C under the same conditions.

100 °C

120 °C

150 °C

170 °C

●b ●

● ●

△c △

■d ■

CONCLUSION

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EXPERIMENTAL SECTION

In summary, we developed a convenient and efficient synthetic method to construct fused metallaaromatics by the intramolecular C−H activation of thiophenes. This method demonstrates the feasible formation of fused aromatics not only with a second-row transition-metal center (ruthenabenzothiophene) but also a third-row transition-metal center (thiophene-fused osmabenzyne). The osmabenzyne can be viewed as the first example of a metallabenzyne with a fused five-membered ring, contributing a valuable addition to the fused metallaaromatic family. Both experimental and theoretical studies suggest that the fused ruthenacycle and osmacycle exhibit aromatic character. The investigation paves the way for new fused metallaaromatics through intramolecular C−H activation of aryl groups.

Table 5. Thermal Decomposition Experiments of 2 and 7 in the Solid Statea 2 7

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All reactions were performed in air for 5 h. b● = stable. c△ = partially decomposed. d■ = completely decomposed, major product is Ph3PO.

a

DFT Calculations of Complexes 2 and 7. As discussed above, the downfield chemical shifts, the delocalized planar structures, and the high stability all indicate that 2 and 7 have aromatic character. To gain more insight, density functional theory (DFT) calculations were performed to evaluate the aromaticity of 2 and 7. The nucleus-independent chemical shift (NICS)23 values were computed. As shown in Figure 4a, the

General Procedures. Unless otherwise stated, all manipulations were performed at room temperature under an atmosphere of N2 using standard Schlenk techniques. Hexane, tetrahydrofuran, and diethyl ether were distilled over sodium/benzophenone, while 1,2dichloroethane and dichloromethane were distilled over calcium hydride under a N2 atmosphere prior to use. Nuclear magnetic resonance (NMR) experiments were performed on a Bruker Advance III 400 spectrometer for compound 1 at 239 K and complexes 6 and 7 at room temperature, on a Bruker Advance III 500 spectrometer for compound 2 and complexes 4 and 5 at room temperature, and on a Bruker Ascend III 600 spectrometer for complex 3 at 278 K. The chemical shifts in the 13C NMR and 1H NMR spectra were relative to tetramethylsilane, while 31P NMR spectra were relative to 85% H3PO4. Coupling constants are given in hertz (Hz). Multiplicities are abbreviated as s, d, t, m, and br for singlet, doublet, triplet, multiplet, and broad, respectively. Elemental analysis data were obtained on a Vario EL III elemental analyzer. The theoretical molecular ion peak was calculated by Compass Isotope Pattern software supplied by Bruker Co. High-resolution mass spectrometry was performed using a Bruker Daltonics Apex ultra 7.0T FT-MS instrument. Synthesis of Ruthenium Vinyl Compound 1.

Figure 4. Evaluation of aromaticity for complexes 2 and 7 by DFT calculations: (a) NICS(1)zz values in ppm for complexes 2 and 7 (program, Gaussian 09; method, B3LYP; basis set, 6-311++g** with Lan2DZ); (b) isomerization stabilization energy (ISE) evaluations of the model complexes 2′ and 7′.

1-(2-Thienyl)-2-propyn-1-ol (0.36 mL, 3.23 mmol) was added to a THF (20 mL) solution of RuCl2(PPh3)3 (2.06 g, 2.15 mmol) and PPh3 (2.82 g, 10.75 mmol). The reaction mixture was stirred at room temperature for 24 h to give a yellow suspension. Compound 1 was obtained as a yellow solid by filtration and washing with Et2O (3 × 40 mL). Yield: 1.53 g, 65%. 1H NMR (400.0 MHz, CD2Cl2, 239 K): δ 11.06 (d, J(P,H) = 22.91 Hz, 1H, C1H), 6.72−7.57 (45H, Ph), 6.46 (br, 1H, C3H), 5.93−6.28 (3H, Th), 2.02 (br, 1H, OH). 31P{1H} NMR (161.9 MHz, CD2Cl2, 239 K): δ 60.25 (d, J(P,P) = 40.43 Hz, RuPPh3), 55.84 (d, J(P,P) = 40.43 Hz, RuPPh3), − 3.69 (s, CPPh3). Unfortunately, 13C{1H} NMR characterization failed because of the poor solubility of 1. Anal. Calcd for C61H51Cl2OP3RuS: C, 66.79; H, 4.69. Found: C, 66.42; H, 5.03.

NICS(1)zz values for the six-membered metallacycle segments and the fused thienyl rings in 2 and 7 are all negative. These values for the six-membered metallacycle segments are comparable to those reported for other metallaaromatics.2k,6e,7c,22a−c,24 Furthermore, the isomerization stabilization energy (ISE)25 was also investigated by the simplified model complexes 2′ and 7′, where the PPh3 ligands were replaced by PH3 ligands. The ISE reactions chosen in Figure 4b have the same total number of anti-diene units both in the reactants and in their products. The absolute ISE value scalculated for 2′ and E

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C1H), 6.32−7.67 (48H, other aromatic protons), 5.75 ppm (br, 1H, C3H), 3.67 (br, 1H, OH). 31P{1H} NMR (202.5 MHz, CD2Cl2): δ 7.07 (br, OsPPh3), 0.64 (s, CPPh3), − 4.05 ppm (br, OsPPh3). Unfortunately, 13C{1H} NMR characterization failed because of the poor solubility of 4. Anal. Calcd for C61H51OOsCl2P3S: C, 61.77; H, 4.33. Found: C, 61.73; H, 4.61. Synthesis of Osmium Carbene Complex 5.

Synthesis of Bis(ruthenabenzothiophene) 2.

Method 1. A mixture of compound 1 (450 mg, 0.41 mmol) and HCl/ Et2O (0.20 mL, 0.49 mmol) in DCM (15 mL) was stirred at room temperature for 2 h to give a red solution. The solution was evaporated under vacuum to about 3 mL and washed with Et2O (3 × 30 mL), from which a red solid was obtained. Yield: 247 mg, 74%. Method 2. A solution of compound 3 (200 mg, 0.18 mmol) was stirred at room temperature in DCM (10 mL) for 2 h to give a red solution. The solvent was evaporated under vacuum to about 2 mL and washed with Et2O (3 × 15 mL), from which a red solid was obtained. Yield: 114 mg, 78%. 1H NMR (500.2 MHz, CD2Cl2): δ 16.26 (dd, J(P,H) = 15.18 Hz, J(P,H) = 7.10 Hz, 2H, C1H), 7.97 (d, J(H,H) = 3.60 Hz, 2H, C6H), 7.73 (d, J(P,H) = 14.25 Hz, 2H, C3H), 6.89 (d, J(H,H) = 3.60 Hz, 2H, C7H), 6.68−7.55 ppm (60H of Ph and aforementioned C7H). 31P{1H} NMR (202.5 MHz, CD2Cl2): δ 47.05 (s, RuPPh3), 18.69 ppm (s, CPPh3). 13C{1H} NMR (125.8 MHz, CD2Cl2, plus 13C-dept 135, 1H−13C HSQC and 1H−13C HMBC): δ 282.10 (dd, J(P,C) = 35.90 Hz, J(P,C) = 15.91 Hz, C1), 244.79 (d, J(P,C) = 13.86 Hz, C5), 143.20 (s, C7), 137.96 (s, C6), 135.20 (d, J(P,C) = 22.08 Hz, C3), 133.14−133.53 (Ph), 132.47 (d, J(P,C) = 47.58 Hz, C4), 126.49−129.12 (Ph), 120.04 (d, J(P,C) = 86.94 Hz, Ph), 113.53 ppm (d, J(P,C) = 75.87 Hz, C2). Anal. Calcd for C86H68Cl4P4Ru2S2: C, 63.24; H, 4.20. Found: C, 63.21; H, 4.44. HRMS (ESI): m/z calcd for [C86H68Cl3P4Ru2S2]+ 1599.0874 [M − Cl]+, found 1599.0867. Synthesis of Ruthenium Carbene Complex 3.

HBF4·Et2O (0.23 mL, 1.68 mmol) was added to a suspension of compound 4 (1.00 g, 0.84 mmol) and NH4Cl (0.13 g, 2.52 mmol) at room temperature in CH2Cl2 (15 mL). The mixture soon turned red and was stirred for a further 5 min. The solvent was evaporated under vacuum to about 5 mL and the residue washed with Et2O (3 × 30 mL), from which a red solid was obtained. Yield: 0.99 g, 94%. 1H NMR (500.2 MHz, CD2Cl2): δ 23.79 (ddd, J(P,H) = 17.58 Hz, J(P,H) = 12.31 Hz, J(P,H) = 5.75 Hz, 1H, C1H), 8.66 (s, 1H, C5H), 8.55 (d, J(P,H) = 18.18 Hz, 1H, C3H), 7.50 (s, 1H, C6H), 7.25 (s, 1H, C7H), 6.75−7.82 ppm (45H of Ph and C6H, C7H mentioned above). 31 1 P{ H} NMR (202.5 MHz, CD2Cl2): δ 23.88 (s, CPPh3), −23.64 (d, J(P,P) = 21.80 Hz, OsPPh3), −27.99 ppm (d, J(P,P) = 21.80 Hz, OsPPh3). 13C{1H} NMR (125.8 MHz, CD2Cl2, plus 13C-dept 135, 1 H−13C HSQC and 1H−13C HMBC): δ 232.74 (br, C1), 148.41 (s, C5), 140.73 (d, J(P,C) = 17.21 Hz, C4), 140.42 (d, J(P,C) = 21.04 Hz, C3), 136.82 (s, C6), 132.36 (s, C7), 136.81−123.41 (Ph and C6), 119.24 ppm (d, J(P,C) = 86.31 Hz, C 2). Anal. Calcd for C61H50BF4OsCl2P3S: C, 58.33; H, 4.01. Found: C, 58.11; H, 4.40. Synthesis of Osmium Carbene Complex 6.

A mixture of 5 (420 mg, 0.33 mmol) and PPh3 (438 mg, 1.65 mmol) was stirred at room temperature in DCM (20 mL) for 1 h. The solvent was evaporated under vacuum to about 3 mL and washed with Et2O (3 × 30 mL), from which a red solid was obtained. Yield: 382 mg, 91%. 1 H NMR (400.1 MHz, CD2Cl2): δ 21.31 (d, J(P,H) = 20.09 Hz, 1H, C1H), 8.17 (d, J(P,H) = 17.36 Hz, 1H, C3H), 8.07 (d, J(H,H) = 5.11 Hz, 1H, C5H), 7.39 (dd, J(H,H) = 5.11 Hz, J(H,H) = 4.13 Hz, 1H, C6H, determined by HSQC), 5.80 (d, J(H,H) = 4.13 Hz, 1H, C7H), 6.80−7.85 ppm (45H of Ph and C6H mentioned above). 31P{1H} NMR (161.9 MHz, CD2Cl2): δ 26.17 (s, CPPh3), −19.45 ppm (s, OsPPh3). 13C{1H} NMR (100.6 MHz, CD2Cl2, plus 13C-dept 135, 1 H−13C HSQC, and 1H−13C HMBC): δ 243.38 (br, C1), 149.47 (d, J(P,C) = 20.31 Hz, C3), 147.43 (s, C5), 137.86 (s, C7), 128.28−135.69 (Ph), 126.76 (s, C6), 119.36 (d, J(P,C) = 87.04 Hz, Ph), 115.21 (d, J(P,C) = 16.86 Hz, C4), 113.14 ppm (d, J(P,C) = 76.18 Hz, C2). Anal. Calcd for C61H50BF4OsCl2P3S: C, 58.33; H, 4.01. Found: C, 58.20; H, 4.41. Synthesis of Fused Osmabenzyne 7.

A mixture of compound 1 (606 mg, 0.55 mmol) and HCl/Et2O (1.10 mL, 2.75 mmol) was stirred at 0 °C in DCM (20 mL) for 1 h to give a red solution. The solvent was evaporated under vacuum to about 5 mL and washed with Et2O (3 × 15 mL), from which a red solid was obtained. Yield: 505 mg, 82%. 1H NMR (600.1 MHz, CD2Cl2, 278 K): δ 17.87 (d, J(P,H) = 20.95 Hz, 1H, C1H), 9.19 (d, J(P,H) = 16.81 Hz, 1H, C3H), 8.59 (s, 1H, C5H), 7.91 (dd, J(H,H) = 10.58 Hz, J(H,H) = 4.60 Hz, 1H, C6H), 6.85−7.80 (Ph, 45H), 6.71 (d, J(H,H) = 4.60 Hz, 1H, C7H). 31P{1H} NMR (242.9 MHz, CD2Cl2, 278 K): δ 24.18 (s, RuPPh3), 11.79 (s, CPPh3). Anal. Calcd for C61H50Cl3P3RuS: C, 65.68; H, 4.52. Found: C, 65.69; H, 4.91. HRMS (ESI): m/z calcd for [C61H50Cl2P3RuS]+ 1079.1261 [M − Cl]+, found 1079.1293. Synthesis of Osmium Vinyl Compound 4.

1-(2-Thienyl)-2-propyn-1-ol (0.17 mL, 1.54 mmol) was added to a THF (20 mL) solution of OsCl2(PPh3)3 (1.61 g, 1.54 mmol). The reaction mixture was stirred at room temperature for 1 h to give a yellow suspension. Compound 4 was obtained as a light yellow solid by filtration and washing with Et2O (3 × 40 mL). Yield: 1.28 g, 70%. 1 H NMR (500.2 MHz, CD2Cl2): δ 12.36 (d, J(P,H) = 22.11 Hz, 1H, F

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Organometallics Table 6. Crystal Data and Structure Refinement Details for 1, 4, 5, and 7 formula Mr T (K) λ(Mo Kα radiation) (Å) cryst syst space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) V (Å3) Z ρcalcd (g cm−3) μ (mm−1) F(000) cryst size (mm3) θ range (deg) no. of rflns collected no. of indep rflns no. of obsd rflns (I ≥ 2σ(I)) no. of data/restraints/params GOF on F2 R1/wR2 (I ≥ 2σ(I)) R1/wR2 (all data) largest peak/hole (e Å−3)

1·2CH2Cl2

4·1.5CH2Cl2

5·2CH2Cl2

7·2CH2Cl2

C63H55Cl6ORuP3S 1266.81 123(2) 0.71073 monoclinic Cc 13.1210(3) 21.3650(4) 20.9552(4) 90 101.630(2) 90 5753.8(2) 4 1.462 0.713 2592 0.30 × 0.20 × 0.10 2.75−29.32 17746 10022 8390 10022/17/688 1.034 0.0387/0.0879 0.0510/0.1153 0.78/-0.59

C62.50H54Cl5OOsP3S 1313.48 173(2) 0.71073 monoclinic Cc 13.1780(3) 21.3377(3) 21.0918(4) 90 102.265(2) 90 5795.40(19) 4 1.505 2.591 2636.0 0.60 × 0.20 × 0.20 2.94−25.00 12271 7663 7036 7663/17/653 1.036 0.0311/0.0862 0.0350/0.0880 1.16/ −0.72

C63H54Cl6OsP3SBF4 1425.74 173.00(14) 0.71073 triclinic P1̅ 12.8967(4) 13.0323(4) 19.7300(5) 93.119(2) 103.706(2) 110.115(3) 2991.40(15) 2 1.583 2.567 1424.0 0.30 × 0.20 × 0.20 3.05−25.00 21622 10543 9518 10543/0/712 1.052 0.0382/0.0842 0.0442/0.0869 1.95/ −1.49

C63H52Cl6OsP3SBF4 1423.73 173.0 1.54178 monoclinic P21/n 10.11140(10) 46.8609(3) 12.70430(10) 90 92.8000(10) 90 6012.48(9) 4 1.573 7.969 2840.0 0.20 × 0.10 × 0.10 3.61−59.52 40502 8784 8493 8784/6/712 1.280 0.0362/0.0807 0.0373/0.0811 1.04/ −1.25

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A dichloroethane (10 mL) solution of 6 (200 mg, 0.16 mmol) was heated at 60 °C in air for 6 h to give a green solution. The solvent was evaporated under vacuum to about 2 mL and washed with Et2O (3 × 20 mL), from which a green solid was obtained. Yield: 178 mg, 89%. 1 H NMR (400.1 MHz, CD2Cl2): δ 7.66 (d, J(P,H) = 11.56 Hz, 1H, C3H), 7.17 (d, J(H,H) = 5.18 Hz, 1H, C7H), 7.06 (d, J(H,H) = 5.18 Hz, 1H, C6H determined by HSQC), 6.87−7.84 ppm (45H of Ph and C3H, C7H, C6H mentioned above). 31P{1H} NMR (161.9 MHz, CD2Cl2): δ 15.30 (s, CPPh3), −9.47 ppm (s, OsPPh3). 13C{1H} NMR (100.6 MHz, CD2Cl2, plus 13C-dept 135, 1H−13C HSQC, and 1H−13C HMBC): δ 275.07 (br, C1), 195.63 (br, C5), 154.46 (d, J(P,C) = 10.34 Hz, C3), 149.91 (s, C7), 144.09 (s, C6), 133.96−136.19 (Ph), 131.95 (d, J(P,C) = 7.44, C4), 118.78−131.66 (Ph), 97.47 ppm (d, J(P,C) = 111.30, C2); Anal. Calcd for C61H48BF4OsCl2P3S: C, 58.43; H 3.86. Found: C, 58.64; H 4.21. Crystallographic Details. Single-crystal X-ray diffraction data were collected on an Oxford Gemini S Ultra CCD Area Detector with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) or Cu Kα radiation (λ = 1.54178 Å). Multiscan or empirical absorption corrections (SADABS) were applied. The structures were solved by Patterson methods, expanded by difference Fourier syntheses, and refined by full matrix least squares on F2 using the SHELXL-2013 program package. Non-H atoms were refined anisotropically unless otherwise stated. Hydrogen atoms were introduced at their geometric positions and refined as riding atoms unless otherwise stated. Crystals suitable for X-ray diffraction were grown from a CH2Cl2 (1, 4, 5, and 7) solution layered with ether or n-hexane. The CH2Cl2 solvent molecules in 1 and 4 are disordered and were refined with suitable restraints. CCDC-1048066 (1), CCDC-1048064 (4), CCDC-1048065 (5), and CCDC-1048062 (7) contain supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac. uk/data_request/cif. Crystal data and structure refinement details for 1, 4, 5, and 7 are given in Table 6.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.6b00083. NMR spectra of complexes 1−7, HRMS of complexes 2 and 3, X-ray structure of compound 1, electrochemistry experiments of complex 2, and theoretical calculations (PDF) Crystallographic data for 1, 4, 5, and 7 (CIF) Cartesian coordinates of the calculated structures (XYZ)

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AUTHOR INFORMATION

Corresponding Authors

*E-mail for H.Z.: [email protected]. *E-mail for H.X.: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This research was supported by the National Natural Science Foundation of China (21272193, 21332002, 21561162001), the program for Changjiang Scholars and Innovative Research Team in University, and the Fundamental Research Funds for the Central Universities (No. 20720150046).

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REFERENCES

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