Rearrangement of Metallabenzynes to Chlorocyclopentadienyl

Feb 27, 2015 - Treatment of the osmabenzyne complex Os{≡C-C(SiMe3)═C(CH3)-C(SiMe3)═CH−}Cl2(PPh3)2 with Mo(CO)6 in refluxing benzene produced t...
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Rearrangement of Metallabenzynes to Chlorocyclopentadienyl Complexes Jiangxi Chen,†,‡ Ka-Ho Lee,† Tingbin Wen,† Feng Gao,† Herman H. Y. Sung,† Ian D. Williams,*,† Zhenyang Lin,*,† and Guochen Jia*,† †

Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen, China, 361005

‡

S Supporting Information *

ABSTRACT: Treatment of the osmabenzyne complex Os{CC(SiMe3)C(CH3)-C(SiMe3)CH−}Cl2(PPh3)2 with Mo(CO)6 in refluxing benzene produced the η5-chlorocyclopentadienyl complex Os{η5-C5HCl(CH3)(SiMe3)2}Cl(CO)(PPh3) and Mo(CO)5(PPh3). A computational study suggests that the chlorocyclopentadienyl complex is most likely produced via the carbene intermediate Os{C(C(SiMe3)C(CH3)-C(SiMe3)CH−)}Cl2(CO)(PPh3) formed by a migratory insertion reaction of the osmabenzyne complex Os{C-C(SiMe3)C(CH3)-C(SiMe3)CH}Cl2(CO)(PPh3). DFT calculations show that the relative thermal stability of metallabenzynes Os(C-CHCHCHCH)Cl2(L)2 and the corresponding isomeric carbene complexes Os{C(−CHCHCHCH−)}Cl2(L)2 as well as the chlorocyclopentadienyl complexes Os(η5C5ClH4)Cl(L)2 (L = CO, phosphine, pyridine, amine) is strongly dependent on ligand L.

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INTRODUCTION There has been much interest in the chemistry of transitionmetal-containing metallaaromatic compounds. Transitionmetal-containing metallabenzenes,1,2 in particular, have attracted considerable recent attention. These complexes are interesting because they can display properties of both aromatic organic compounds and organometallic compounds. A class of metallaaromatics that are structurally closely related to metallabenzenes are metallabenzynes,3 organometallic compounds derived from formal replacement of a carbon atom in benzyne by an isolobal transition-metal fragment. Compared with that of metallabenzenes, the chemistry of metallabenzynes is less developed. One of the major issues in the development of metallabenzyne chemistry is to explore the chemical properties of this interesting class of metallaaromatics. Previous studies have shown that metallabenzynes can undergo electrophilic substitution reactions to give new metallabenzynes,4,5 nucleophilic addition reactions to give metallabenzenes6 or isometallabenzenes,7 and migratory insertion reactions to give carbene complexes.8,9 In this work, we report a new transformation of metallabenzynes, namely, the conversion of metallabenzynes into chlorocyclopentadienyl complexes.

reactions of metallabenzenes to give cyclopentadienyl complexes are well-documented.10 A theoretical study suggests that steric effects involving the substituents (t-butyl, 1-adamantyl) on the metallacycle play an important role in inducing the conversion of osmabenzyne complexes Os{C-CHC(R)CHCH}Cl2(PPh3)2 (R = t-butyl, 1-adamantyl) to the carbenes Os{C(−CHC(R)-CHCH−)}Cl2(PPh3)2. It is known that migratory insertion reactions of carbyne complexes Ln(R′)MCR to give carbene complexes LnM CRR′ are also affected by both metals and ligands.11−14 Thus, it would be of interest to study a similar effect for metallabenzyne systems. However, experimental work in this direction is still lacking, although, recently, Zhu and his co-workers have carried out a theoretical study of ligand effects on the conversion of metallanaphthalynes to indenylidene complexes.9b In our effort to study the ligand effect on the conversion of osmabenzyne complexes to carbene complexes, we have carried out ligand substitution reactions of the osmabenzyne complex Os{CC(SiMe3)C(CH3)-C(SiMe3)CH−}Cl2(PPh3)2 (1) with PCy3, a strong σ-donating ligand, and CO, a strong π-accepting ligand. The reaction of 1 with PCy3 was first examined. Heating of a mixture of osmabenzyne 115 and excess PCy3 in benzene at 80 °C for 12 h produced the osmabenzyne complex Os{CC(SiMe3)C(CH3)-C(SiMe3)CH−}Cl2(PCy3)2 (2), which was isolated as a blue solid in 61% yield (Scheme 1). The structure of 2 can be readily assigned based on its NMR spectroscopic data. The 31P{1H} NMR spectrum (in CD2Cl2) showed a singlet at −0.1 ppm. The 13C{1H} NMR spectrum

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RESULTS AND DISCUSSION Experimental Observations. We have recently shown that the osmabenzyne complexes Os{C-CHC(R)-CHCH}Cl2(PPh3)2 (R = t-butyl, 1-adamantyl) could undergo migratory insertion reactions to give the corresponding carbenes Os{ C(−CHC(R)-CHCH−)}Cl2(PPh3)2.8 These reactions are interesting as they represent the only experimentally observed examples of rearrangement of metallabenzynes to carbene complexes. In contrast, analogous migratory insertion © XXXX American Chemical Society

Received: December 7, 2014

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Treatment of the osmabenzyne complex Os{C-C(SiMe3)C(CH3)-C(SiMe3)CH}Cl2(PPh3)2 (1) with Mo(CO)6 in refluxing benzene produced a mixture of species, from which the unexpected η5-chlorocyclopentadienyl complex Os{η5-C5HCl(CH3)(SiMe3)2}Cl(CO)(PPh3) (3) and the known complex Mo(CO)5(PPh3) (4)17 were isolated in 50.2% and 32.5% yields, respectively, based on osmium (Scheme 1). The in situ 31P{1H} spectrum indicates that the reaction also produced minor phosphorus-containing species with chemical shifts of 25.4, 11.3, and 12.8 ppm. Unfortunately, we have failed to identify the minor species. Complex 3 has been characterized by multinuclear NMR and elemental analysis. In the 31P{1H} NMR spectrum, the complex showed a sharp singlet for the phosphine ligand at 5.5 ppm. The 1H NMR spectrum showed the characteristic 1H signal of the Cp ring at 4.23 ppm and that of the methyl at 2.08 ppm. The 13C{1H} NMR spectrum showed the characteristic CO signal at 184.3 ppm. The single-crystal X-ray structure of 3 confirmed it to be a chlorocyclopentadienyl complex (Figure 2).

Scheme 1

displayed the OsC signal at 301.2 ppm, the Os-CH signal at 224.8 ppm, the CCH3 signal at 180.0 ppm, and the C(SiMe3) signals at 134.0 and 113.7 ppm. In the 1H NMR spectrum (in CD2Cl2), the OsCH and the CH3 signals were observed at 14.80 and 2.79 ppm, respectively. The structure of 2 has also been confirmed by an X-ray diffraction analysis (Figure 1).

Figure 2. ORTEP drawing of 3 with thermal ellipsoids at 35% probability level. The hydrogen atoms on the PPh3 ligand and TMS groups are omitted for clarity. Selected bond lengths [Å] and angles [deg]: Os(1)−C(1) 2.176(4), Os(1)−C(2) 2.253(4), Os(1)−C(3) 2.320(4), Os(1)−C(4) 2.323(4), Os(1)−C(5) 2.184(4), Os(1)− C(10) 1.858(5); C(10)−Os(1)−C(1) 91.39(17), P(1)−Os(1)−C(5) 101.59(11), Cl(2)−Os(1)−C(3) 90.22(10).

Figure 1. ORTEP drawing of Os{C-C(SiMe3)C(CH3)-C(SiMe3)CH}Cl2(PCy3)2 (2) with thermal ellipsoids at 35% probability level. The hydrogen atoms on the PCy3 ligands and TMS groups are omitted for clarity. Selected bond lengths [Å] and angles [deg]: Os(1)−C(1) 1.767(6), C(1)−C(2) 1.376(8), C(2)− C(3) 1.412(8), C(3)−C(4) 1.430(8), C(4)−C(5) 1.387(8), Os(1)− C(5) 2.011(6); C(5)−Os(1)−C(1) 77.8(2), Os(1)−C(1)−C(2) 153.2(5), C(1)−C(2)−C(3) 111.7(5), C(2)−C(3)−C(4) 123.1(5), C(3)−C(4)−C(5) 120.3(5), C(4)−C(5)−Os(1) 134.0(4).

Proposed Reaction Mechanisms. Scheme 2 shows two plausible pathways for the formation of complex 3. As Mo(CO)6 can act as the source of carbon monoxide, we assume that the key intermediate of the reaction is the osmabenzyne 5, which can be formed by an initial ligand exchange reaction of 1 with Mo(CO)6. From osmabenzyne 5, complex 3 could be formed via a carbene intermediate (path A), or a metallabenzene intermediate (path B). In path A, the osmabenzyne 5 or its isomers undergo migratory insertion reactions involving the two metal-bonded carbons to give the carbene complex 6. Migratory insertion of the carbene into the Os−Cl bond in 6 with a change to η5 coordination would give complex 3. In path B, the osmabenzyne 5 or its isomers undergo migratory insertion involving one of the chloride ligands and the carbyne carbon of 5 to give the metallabenzene complex Os{CCl-C(SiMe3)C(CH3)-C(SiMe3)CH}Cl-

Overall, the structural features associated with the metallacycle are very similar to those of 1.15 Considering the reaction conditions, we can conclude that complex 2, like 1, is thermally stable, and does not rearrange to the corresponding carbene complex. We next attempted to prepare a CO-supported osmabenzyne complex. It is known that Mo(CO)6 can be used as a source of carbon monoxide.16 Therefore, the reaction of osmabenzyne 1 with Mo(CO)6 was carried out with the intention of obtaining a CO-containing osmabenzyne through a ligand exchange reaction of 1 with Mo(CO)6. B

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migratory insertion process is thermodynamically favored by 6.2 kcal/mol, but with a substantially high barrier of 33.9 kcal/ mol. The barrier for the carbene formation is significantly lowered if 8 first isomerizes to 8_iso1, which then undergoes migratory insertion. The isomer 8_iso1, in which a chloride ligand is trans to the carbyne carbon and PPh3 is trans to the vinyl carbon, can be generated from 8 via dissociation of PPh3 to give the five-coordinated intermediate 8_pro (with a barrier of 23.0 kcal), followed by association of PPh3 with 8_pro (with a barrier of 10.4 kcal/mol). Migratory insertion of 8_iso1 involving the two osmium-bonded carbon atoms gives the square pyramidal carbene complex 9_iso1, in which two chloride ligands are cis to each other, the carbene ligand is at the axial position with the carbocylic ring of the carbene ligand parallel to the Cl-Os-CO axis, and the SiH3 group at the carbon α to the carbene carbon is on the same side of the CO ligand. When compared with the direct reduction process, this process via 8_iso1 to 9_iso1 is thermodynamically favored by −9.8 kcal/mol with a moderate barrier of 23.6 kcal/mol.18 Migratory insertion of the carbene complex 9_iso1 to give the final η5-chlorocyclopentadienyl product 11 can proceed exothermically via a transition state lying 20.4 kcal/mol in energy above complex 8 (see the Supporting Information). The barrier for the formation of 11 is lowered if 9_iso1 first isomerizes, by rotation about the OsC bond via TS9_iso1‑9_iso2, to isomer 9_iso2 in which the SiH3 group at the carbon α to the carbene carbon is on the same side of the Cl ligand. The isomerization process has a barrier of 15.5 kcal/ mol. Migratory insertion of 9_iso2 produces the k2-C,Clchlorocyclopentadienyl complex 10, which rearranges to the final η5-chlorocyclopentadienyl product 11 exothermically via TS10‑11, which lies 17.0 kcal/mol in energy above complex 8. Formation of the chlorocyclopentadienyl complex 11 from 819 involving metallabenzene intermediates (path B) is less favored, as indicated by the energy profile shown in Figure 4. Migratory insertion of 8 involving one of the chloride ligands

Scheme 2

(CO)(PPh3) (7), which undergoes a further migratory insertion and rearrangement to give complex 3. Theoretical Studies. As described below, our computational study suggests that path A is the preferred pathway for the formation of the η5-chlorocyclopentadienyl complex. The reaction of Os{C-C(SiH 3 )C(CH 3 )C(SiH 3 )CH}Cl2(PPh3)2 (1A, a model complex for 1) with Mo(CO)6 to give Os{C-C(SiH3)C(CH3)-C(SiH3)CH}Cl2(CO)(PPh3) (8) (a model complex for 5) and Mo(CO)5(PPh3) was found to be feasible with a free energy change of −0.9 kcal/ mol. Figure 3 shows the energy profile calculated for the formation of the chlorocyclopentadienyl complex Os{η5C5HCl(CH3)(SiH3)2}Cl(CO)(PPh3) (11) (a model for complex 3) from Os{C-C(SiH3)C(CH3)-C(SiH3) CH}Cl2(CO)(PPh3) (8) (a model for complex 5) via path A. Direct migratory insertion reaction of 8 involving the two osmium-bonded carbon atoms gives the square pyramidal carbene complex 9 with the carbene ligand at the axial position and the two trans-chloride ligands at the base. This direct

Figure 3. Energy profiles for the rearrangement of 8 to the chlorocyclopentadienyl complex 11 involving carbene intermediates (Path A). The relative Gibbs free energies and electronic energies (in parentheses) at 298 K are given in kcal/mol. C

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Figure 4. Energy profiles for the rearrangement of 8 to the cyclopentadienyl complex 11 involving metallabenzene intermediates (Path B). The relative Gibbs free energies and electronic energies (in parentheses) at 298 K are given in kcal/mol.

rather than a chloride ligand is transferred to the carbene carbon.

and the carbyne carbon gives the pseudo trigonal bipyramidal metallabenzene complex 12 with CO and PPh3 ligands at the axial positions. The process is slightly unfavorable thermodynamically (by 0.9 kcal/mol) with a barrier of 20.2 kcal/mol. Further migratory insertion of 12 to give the final product chlorocyclopentadienyl complex 11 has a substantially higher barrier of 37.2 kcal/mol. The barrier for the formation of 11 is lowered if 12 first isomerizes to isomer 12_iso1, a square pyramidal metallabenzene complex which contains the CCl(vinyl) carbon at the apical position and PPh3 trans to the CH carbon. This isomer is 2.5 kcal/mol less stable than 12, and can be generated from 12 with a barrier of 14.5 kcal/mol. Rearrangement of isomer 12_iso1 to the final product chlorocyclopentadienyl complex 11 can proceed via TS12_iso1‑11, which lies 26.6 kcal/mol in energy above complex 8.20 Since the overall barrier for path B (26.6 kcal/mol, Figure 4) is higher than that for path A (23.1 kcal/mol, Figure 3) and the metal carbene complexes 9_iso1 and 9_iso2 (in path A) are thermodynamically more stable than the metallabenzenes 12 and 12_iso1 (in path B), formation of the metal carbene complexes 9_iso1 and 9_iso2 is likely to be preferred over the metallabenzenes 12 and 12_iso1, and the reaction pathway involving metallabenzene intermediate (path B) is, therefore, probably less important for the formation of the cyclopentadienyl complex 11. Formation of the η5-chlorocyclopentadienyl complexes from the dichloro osmium carbene complexes is interesting as several dichloro osmium carbene complexes Os(CRR′)Cl2Ln have been isolated, but migratory insertion reactions of these complexes involving chloride and carbene carbon appear to be unknown.21 As a closely related transformation, we noted that the cyclopentadienyl complex 15 was produced when the ruthenium indenylidene complex 13 was refluxed in EtOH in the presence of NEt3, which was proposed to proceed through intermediate 14 (Scheme 3).22 However, in this case, a hydride

Scheme 3

One may ask why the PPh3-containing osmabenzyne 1 and the PCy3-containing osmabenzyne 2 do not rearrange to the corresponding carbene or cyclopentadienyl complexes, and whether osmabenzynes supported by other ligands would undergo similar transformation. To answer these questions, we have calculated the relative energies of metallabenzynes of the type Os(C-CHCHCHCH)Cl2(L) 2 (16) and the corresponding isomeric carbene complexes Os{C(−CH CHCHCH−)}Cl2(L)2 (17) and chlorocyclopentadienyl complexes Os(η5-C5ClH4)Cl(L)2 (18). The results are presented in Figure 5. Consistent with experimental observations, complexes supported with PPh3 (a) and PMe3 (b) ligands have the following trend in their relative energies: osmabenzyne (16) < carbene complex (17) < chlorocyclopentadienyl complex (18). Complexes supported with the amine ligand NMe3 (g) have the same trend. The three isomers have very similar stability when L = PH3 (d). Complexes supported with π accepting ligands P(OMe)3 (c), PCl3 (e), and CO (f) have the opposite trend in their relative energies: osmabenzyne (16) > carbene complex (17) > chlorocyclopentadienyl complex (18). Interestingly, pyridine-supported complexes (h) have the following trend in their relative energies: carbene complex (17) < osmabenzyne (16) < chlorocyclopentadienyl complex (18). D

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AZ). 1H, 13C{1H}, and 31P{1H} spectra were collected on a Bruker ARX-400 spectrometer (400 MHz). 1H and 13C NMR shifts are relative to TMS, and 31P chemical shifts relative to 85% H3PO4. Reactions of 1 with PCy3. A benzene (10 mL) solution of Os{ C-C(SiMe3)C(CH3)-C(SiMe3)CH}Cl2(PPh3)2 (1) (0.30 g, 0.30 mmol) and PCy3 (1.26 g, 4.50 mmol) was heated at 80 °C for 12 h to give a blue solution. The solvent was pumped away under vacuum, and the residue was extracted with diethyl ether (3 mL). Hexane (20 mL) was added to the extract with stirring. The solution was concentrated to ca. 8 mL and cooled with an ice bath for 30 min to give a blue precipitate. The blue solid was collected by filtration, washed with cooled hexane (2 × 3 mL), and dried under vacuum, and was identified to be 2. Yield: 0.19 g, 61%. 31P {1H} NMR (161.98 MHz, CD2Cl2): δ −0.1 (s). 1H NMR (400.13 MHz, CD2Cl2): δ 0.35 (s, 9 H, Si(CH3)3), 0.42 (s, 9 H, Si(CH3)3), 1.05−2.46 (m, 66 H, PCy3), 2.79 (s, 3 H, CH3), 14.80 (s, 1 H, OsCH). 13C {1H} NMR (100.40 MHz, CD2Cl2): δ 301.2 (t, 2JP,C = 10.0 Hz, OsC), 224.8 (t, 2JP,C = 5.6 Hz, OsCH), 180.0 (s, CCH3), 134.0 (s, OsCHC(SiMe3)), 113.7 (s, OsCC(SiMe3)), 33.2 (t, JP,C = 11.7 Hz, PCy3), 29.3 (s, PCy3), 28.3 (s, PCy3), 27.1 (t, JP,C = 5.0 Hz, PCy3), 26.8 (t, JP,C = 5.6 Hz, PCy3), 25.9 (s, CH3), 25.8 (s, PCy3), 0.9 (s, SiMe3), 0.1 (s, SiMe3). Anal. Calcd for C48H88Cl2OsP2Si2: C 55.20, H 8.49; Found: C 55.12; H 8.25. Reactions of 1 with Mo(CO)6. A mixture of Os{C-C(SiMe3) C(CH3)-C(SiMe3)CH}Cl2(PPh3)2 (1) (327 mg, 0.32 mmol) and Mo(CO)6 (440 mg, 1.67 mmol) in benzene (8 mL) was stirred at 80 °C for 12 h to give a brown solution. The mixture was concentrated to ca. 1 mL and was loaded onto a silica gel column. The column was flashed with hexane to remove excess Mo(CO)6 and then eluted with hexane/dichloromethane (3/1) to give a yellow solution, which gives the known complex Mo(CO)5(PPh3) (4) after the solvent was removed under vacuum. Yield: 52 mg, 32.5% (based on Os) or 6.2% (based on Mo(CO)6). 31P{1H} NMR (161.98 MHz, C6D6): δ 37.9 (s). The column was then eluted with hexane/dichloromethane (1/1) to give a yellow solution. The solvent was removed under vacuum to give complex 3 as a yellow solid, which was dried under vacuum. Yield: 126 mg, 50.2%. 31P{1H} NMR (161.98 MHz, C6D6): δ 5.5 (s). 1H NMR (400.13 MHz, C6D6): δ 7.87−7.90 (m, 6H, PPh), 7.05−7.17 (m, 9H, PPh), 4.23 (d, JP,H = 1.94 Hz, 1H, η5-C5H), 2.09 (d, JP,H = 1.50 Hz, 3H, CH3), 0.64 (s, 9H, Si(CH3)3), 0.11 (s, 9H, Si(CH3)3). 13 C{1H} NMR (100.62 MHz, CD2Cl2): δ 184.3 (d, 2JP,C = 14.9 Hz, CO), 134.3 (d, 1JP,C = 55.2 Hz, PPh3), 133.4 (d, JP,C = 10.8 Hz, PPh3), 129.6 (d, JP,C = 2.3 Hz, PPh3), 127.3 (d, JP,C = 11.1 Hz, PPh3), 123.5 (d, JP,C = 3.1 Hz, η5-C5CH3), 95.6 (s, η5-C5Cl), 88.5 (s, η5-C5H), 83.6 (d, JP,C = 7.6 Hz, η5-C5SiMe3), 83.4 (s, η5-C5SiMe3), 13.5 (s, CH3)), 0.5 (s, Si(CH3)3), −0.5 (s, Si(CH3)3). Anal. Calcd for C31H37Cl2OOsPSi2: C, 48.11; H, 4.82. Found: C, 47.87; H, 5.02. Crystal Structure Analyses. Crystals of 2 and 3 suitable for X-ray diffraction were grown from CH2Cl2 solutions layered with hexane. The crystals were mounted on glass fibers with epoxy glue. The diffraction intensity data of 2 were collected with a Bruker APEX CCD diffractometer using Mo−Kα radiation (λ = 0.71073 Å) at 293 K. Lattice determination and data collection were carried out using SMART v.5.625 software. Data reduction and absorption correction were performed using SAINT v 6.26 and SADABS v 2.03, respectively. The diffraction intensity data of 3 were collected with an Oxford Diffraction Gemini S Ultra X-ray diffractometer with monochromatized Cu−Kα radiation (λ = 1.54178 Å). Lattice determination, data collection and reduction were carried out using CrysAlisPro 171.33.46. Empirical absorption correction using spherical harmonics, was implemented with the SCALE3 ABSPACK scaling algorithm in the CrysAlisPro program suite. Structure solution and refinement for all compounds were performed using the Olex2 software23 package (which embedded SHELXTL24). All the structures were solved by direct methods, expanded by difference Fourier syntheses, and refined by full-matrix least-squares on F2. All non-hydrogen atoms were refined anisotropically with a riding model for the hydrogen atoms, except noted separately. Further details on crystal data, data collection, and refinements are summarized in Table S1 (Supporting Information).

Figure 5. Relative energies of osmabenzynes Os(C-CHCHCH CH)Cl2(L)2 (16, 0.0 kcal/mol) and their corresponding isomeric carbene (17) and chlorocyclopentadienyl (18) complexes. The relative Gibbs free energies and electronic energies (in parentheses) at 298 K are given in kcal/mol.

We have also calculated the relative energies of the related CO-containing metallabenzynes of the type Os(C-CH CHCHCH)Cl2(CO)(PR3) (19) and the corresponding isomeric carbene (20) and chlorocyclopentadienyl (21) complexes where PR3 = PPh3 (a), PMe3 (b). For both cases, the three isomers are in the following trend in their relative energies: osmabenzyne > carbene complex > chlorocyclopentadienyl complex (see the Supporting Information for details).

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CONCLUSION Treatment of the osmabenzyne complex Os{C-C(SiMe3) C(CH3)-C(SiMe3)CH}Cl2(PPh3)2 with Mo(CO)6 in refluxing benzene produced the η5-chlorocyclopentadienyl complex Os{η5-C5HCl(CH3)(SiMe3)2}Cl(CO)(PPh3) and Mo(CO)5(PPh3). A computational study suggests that the chlorocyclopentadienyl complex is most likely formed via the carbene intermediate Os{C(C(SiMe 3 )C(CH 3 )-C(SiMe 3 ) CH−}Cl2(CO)(PPh3) formed by a migratory insertion reaction of the osmabenzyne complex Os{C-C(SiMe3) C(CH3)-C(SiMe3)CH}Cl2(CO)(PPh3). DFT calculations show that the relative thermal stability of metallabenzynes Os(C-CHCHCHCH)Cl2(L)2 and the corresponding isomeric carbene complexes Os{C(−CHCHCH CH−)}Cl2(L)2 as well as the chlorocyclopentadienyl complexes Os(η5-C5ClH4)Cl(L)2 (L = CO, phosphine, pyridine, amine) varies with ligand L.

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EXPERIMENTAL SECTION

All manipulations were carried out under a nitrogen atmosphere using standard Schlenk techniques unless otherwise stated. Solvents were distilled under nitrogen from sodium benzophenone (benzene, diethyl ether, hexane), or calcium hydride (CH2Cl2). The starting material Os{C-C(SiMe3)C(CH3)-C(SiMe3)CH}Cl2(PPh3)2 (1)15 was prepared following the procedure described in the literature. All other reagents were used as purchased from Aldrich Chemical Co. Microanalyses were performed by M-H-W Laboratories (Phoenix, E

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Organometallics Computational Details. The Becke3LYP (B3LYP) level25 of density functional theory was used to optimize (without any constraint) all the structures studied in this work. The SDD effective core potentials and basis sets were used to describe Os, Cl, P, and Si atoms.26 Polarization functions were added for Os(ζ(f) = 0.707), Cl(ζ(d) = 0.514), P(ζ(d) = 0.340) and Si(ζ(d) = 0.262).27 The 631G* basis set was used for carbons involved in the metallabenzyne ring, and 6-31G basis set for all other atoms.28 Frequency calculations were also performed to identify all the stationary points as minima (zero imaginary frequency) or transition states (one imaginary frequency), and to provide Gibbs free energies at 298.15 K. All of the calculations were performed with the Gaussian 03 package.29

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567. (q) Dalebrook, A. F.; Wright, L. J. Organometallics 2009, 28, 5536. (3) (a) Roper, W. R. Angew. Chem., Int. Ed. 2001, 40, 2440. (b) Jia, G. Organometallics 2013, 32, 6852. (4) Wen, T. B.; Ng, S. M.; Hung, W. Y.; Zhou, Z. Y.; Lo, M. F.; Shek, L. Y.; Williams, I. D.; Lin, Z.; Jia, G. J. Am. Chem. Soc. 2003, 125, 884. (5) Hung, W. Y.; Liu, B.; Shou, W.; Wen, T. B.; Shi, C.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.; Jia, G. J. Am. Chem. Soc. 2011, 133, 18350. (6) Hung, W. Y.; Zhu, J.; Wen, T. B.; Yu, K. P.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.; Jia, G. J. Am. Chem. Soc. 2006, 128, 13742. (7) Zhao, Q.; Zhu, J.; Huang, Z. A.; Cao, X. Y.; Xia, H. Chem.Eur. J. 2012, 18, 11597. (8) Chen, J.; Shi, C.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.; Jia, G. Angew. Chem., Int. Ed. 2011, 50, 7295. (9) For theoretical studies, see: (a) Anusha, C.; De, S.; Parameswaran, P. Dalton Trans. 2013, 42, 14733. (b) Fan, J.; An, K.; Wang, X.; Zhu, J. Organometallics 2013, 32, 6271. (10) See, for example: (a) Johns, P. M.; Roper, W. R.; Woodgate, S. D.; Wright, L. J. Organometallics 2010, 29, 5358. (b) Wu, H. P.; Lanza, S.; Weakley, T. J. R.; Haley, M. M. Organometallics 2002, 21, 2824. (c) Wu, H. P.; Weakley, T. J. R.; Haley, M. M. Chem.Eur. J. 2005, 11, 1191. (d) Wu, H. P.; Ess, D. H.; Lanza, S.; Weakley, T. J. R.; Houk, K. N.; Baldridge, K. K.; Haley, M. M. Organometallics 2007, 26, 3957. (e) Yang, J.; Jones, W. M.; Dixon, J. K.; Allison, N. T. J. Am. Chem. Soc. 1995, 117, 9776. (11) (a) Spivak, G. J.; Coalter, J. N.; Oliván, M.; Eisenstein, O.; Caulton, K. G. Organometallics 1998, 17, 999. (b) Spivak, G. J.; Caulton, K. G. Organometallics 1998, 17, 5260. (c) Caulton, K. G. J. Organomet. Chem. 2001, 617−618, 56. (d) Jacobsen, J. J. Organomet. Chem. 2003, 674, 50. (e) Bolano, T.; Castarlenas, R.; Esteruelas, M. A.; Modrego, F. J.; Oñate, E. J. Am. Chem. Soc. 2005, 127, 11184. (f) Bolaño, T.; Esteruelas, M. A.; Oñate, E. J. Organomet. Chem. 2011, 696, 3911. (12) For additional examples of conversion of Os(R′)CR complexes to OsCRR′ complexes, see: (a) Esteruelas, M. A.; García-Yebra, C.; Oliván, M.; Oñate, E.; Tajada, M. A. Organometallics 2000, 19, 5098. (b) Barrio, P.; Esteruelas, M. A.; Oñate, E. J. Am. Chem. Soc. 2004, 126, 1946. (c) Lee, J. H.; Pink, M.; Caulton, K. G. Organometallics 2006, 25, 802. (d) Bolano, T.; Castarlenas, R.; Esteruelas, M. A.; Oñate, E. J. Am. Chem. Soc. 2007, 129, 8850. (e) Bolano, T.; Castarlenas, R.; Esteruelas, M. A.; Oñate, E. Organometallics 2007, 26, 2037. (f) Castro-Rodrigo, R.; Esteruelas, M. A.; López, A. M.; Oñate, E. Organometallics 2008, 27, 3547. (g) Bolano, T.; Castarlenas, R.; Esteruelas, M. A.; Oñ ate, E. Organometallics 2008, 27, 6367. (h) Buil, M.; Esteruelas, M. A.; Garces, K.; Oñate, E. Organometallics 2009, 28, 5691. (i) Liu, B.; Xie, H.; Wang, H.; Wu, L.; Zhao, Q.; Chen, J.; Wen, T. B.; Cao, Z.; Xia, H. Angew. Chem., Int. Ed. 2009, 48, 5461. (13) For examples of conversion of OsCHR complexes to Os(H)CR complexes, see: (a) Esteruelas, M. A.; Oliván, M.; Oñate, E.; Ruiz, N.; Tajada, M. A. Organometallics 1999, 18, 2953. (b) Buil, M. L.; Eisenstein, O.; Esteruelas, M. A.; García-Yebra, G.; GutierrezPuebla, E.; Oliván, M.; Oñ ate, E.; Ruiz, N.; Tajada, M. A. Organometallics 1999, 18, 4949. (c) Buil, M. L.; Esteruelas, M. A.; García-Yebra, C.; Gutiérrez-Puebla, E.; Oliván, M. Organometallics 2000, 19, 2184. (d) Baya, M.; Esteruelas, M. A.; Oñ ate, E. Organometallics 2001, 20, 4875. (e) Barrio, P.; Esteruelas, M. A.; Oñate, E. Organometallics 2002, 21, 2491. (f) Esteruelas, M. A.; González, A. I.; López, A. M.; Oñate, E. Organometallics 2003, 22, 414. (g) Esteruelas, M. A.; González, A. I.; López, A. M.; Oñate, E. Organometallics 2004, 23, 4858. (h) Castarlenas, R.; Esteruelas, M. A.; Oñate, E. Organometallics 2007, 26, 2129. (i) Castarlenas, R.; Esteruelas, M. A.; Lalrempuia, R.; Oliván, M.; Oñate, E. Organometallics 2008, 27, 795. (14) For additional examples of conversion of M(R′)CR complexes to MCRR′ complexes with metals other than osmium, see: (a) M = W: Bannwart, E.; Jacobsen, H.; Furno, F.; Berke, H. Organometallics 2000, 19, 3605. (b) M = Ru: Boone, M. P.; Brown, C. C.; Ancelet, T. A.; Stephan, D. W. Organometallics 2010, 29, 4369.

ASSOCIATED CONTENT

S Supporting Information *

Detailed computational results; tables giving Cartesian coordinates and electronic energies for all the calculated structures; and X-ray crystallographic files (CIF) for complexes 2 and 3. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (I.D.W.). *E-mail: [email protected] (Z.L.). *E-mail: [email protected] (G.J.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the Hong Kong Research Grants Council (Project Nos.: 602611, 601812, CUHK7/CRF/12G2).

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REFERENCES

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Article

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