Syntheses and Characterization of Ruthenium Complexes Containing

Aug 13, 2010 - (CO)12 afforded cis-{(η5-C5H3)2(CMe2)2}Ru2(CO)4, (2) in 68% yield. ... (1) For singly linked diCp ligands: (a) (CH2) Schore, N. E.; Il...
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Organometallics 2010, 29, 3868–3875 DOI: 10.1021/om100566w

Syntheses and Characterization of Ruthenium Complexes Containing a Doubly Linked Dicyclopentadienyl Ligand and Acetonitrile Ligands Robert M Chin,* Andrew Simonson, Joshua Mauldin, and Jared Criswell Department of Chemistry and Biochemistry, University of Northern Iowa, Cedar Falls, Iowa 50614-0423

William Brennessel Department of Chemistry, University of Rochester, Rochester, New York 14627 Received June 8, 2010

The reaction of a mixture of isomers of 4,4,8,8-tetramethyl-tetrahydro-s-indacene (1) with Ru3(CO)12 afforded cis-{(η5-C5H3)2(CMe2)2}Ru2(CO)4, (2) in 68% yield. Reaction of 2 with Br2 gave cis-{(η5-C5H3)2(CMe2)2}Ru2(CO)4Br2 (3) in 88% yield. Reaction of 3 with AgOTf yields cis-[{(η5C5H3)2(CMe2)2}Ru2(CO)4(μ-Br)][OTf] (4), while reaction of 3 with Me3NO and AgOTf yields cis-[{(η5-C5H3)2(CMe2)2}Ru2(CO)2(MeCN)2(μ-Br)][OTf] (5). Reaction of 3 under more forcing conditions with AgOTf in MeCN gave cis-[{(η5-C5H3)2(CMe2)2}Ru2(CO)2(MeCN)4][OTf]2 (6), while a MeCN/C6H6 solvent combination afforded cis-[{(η5-C5H3)2(CMe2)2}Ru2(η6-C6H6)2][OTf]2 (7) in a 64% yield. Removal of the benzene ligands in 7 can be accomplished by first adding H- to the coordinated benzene ligands to afford cis-{(η5-C5H3)2(CMe2)2}Ru2(η5-C6H7)2 (10). Subsequent protonation of 10 in MeCN afforded [cis-{(η5-C5H3)2(CMe2)2}Ru2(MeCN)6][OTf]2 (8) in 88% yield. Structural data for 4, 5, 7, and 10 are reported.

Linked cyclopentadienyl ligands have been previously synthesized to study the interaction of two metal centers next to each other with the dicyclopentadienyl ligands typically have one or two linking units.1 The advantage of the doubly linked system over the singly linked system is that there is no free rotation in the doubly linked system to rotate the metal centers away from each other. This ensures that the two metal centers stay in close proximity to one another.

However, while a doubly linked dicyclopentadienyl ligand eliminates the problem of rotation about the linking *To whom correspondence should be addressed. E-mail: martin. [email protected]. (1) For singly linked diCp ligands: (a) (CH2) Schore, N. E.; Ilenda, C. S.; White, M. A.; Bryndza, H. E.; Matturro, M. G.; Bergman, R. G. J. Am. Chem. Soc. 1984, 106, 7451–7461. (b) (SiMe2) Wegner, P. A.; Uski, V. A.; Kiester, R. P.; Dabestani, S.; Day, V. W. J. Am. Chem. Soc. 1977, 99, 4846–4848. (c) (CMe2) Nifant'ev, I. E.; Yarnykh, V. L.; Borzov, M. V.; Mazurchik, B. A.; Mstyslavsky, V. I.; Roznyatovsky, V. A.; Ustynyuk, Y. A. Organometallics 1991, 10, 3739–3745. For doubly linked diCp ligands: (d) (diCH2) Roussel, P.; Drewitt, M. J.; Cary, D. R.; Webster, C. G.; O'Hare, D. Chem. Commun. 1998, 2205–2206. (e) (diSiMe2) Jones, P. R.; Rozell, J. M.; Campbell, B. M. Organometallics 1985, 4, 1321–1324. (f) (CMe2/SiMe2) Wang, B.; Zhu, B.; Zhang, J.; Xu, S.; Zhou, X.; Weng, L. Organometallics 2003, 22, 5543–5555. pubs.acs.org/Organometallics

Published on Web 08/13/2010

unit, it introduces the problem of having cis and trans isomers.

One way to help favor the formation of the cis isomer is to use a ligand with a low steric profile such as carbon monoxide, CO. Angelici and co-workers have reported that the reaction of Ru3(CO)12 with (C5H4)2(SiMe2)2 yields the cis-{(η5C5H3)2(SiMe2)2}Ru2(CO)4 isomer in 72% yield.2 However the use of CO as a ligand can be problematic when trying to generate open coordination sites due to the strong binding of the CO ligand. Herein, we report several cis dinuclear ruthenium complexes that contain the labile acetonitrile, MeCN, ligand.

Results and Discussion We chose to use the more robust CMe2 linkers in our doubly linked Cp system rather than the SiMe2 group due to (2) Ovchinnikov, M. V.; Angelici, R. J. J. Am. Chem. Soc. 2000, 122, 6130–6131. r 2010 American Chemical Society

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the C-Si bond being cleaved in some of the previously reported reactions.3 Reaction of Ru3(CO)12 with a mixture of 4,4,8,8-tetramethyl-1,4,7,8-tetrahydro-s-indacene, 1a, and 4,4,8,8-tetramethyl-1,4,5,8-tetrahydro-s-indacene, 1b, gave the tetracarbonyl complex cis-{(η5-C5H3)2(CMe2)2}Ru2(CO)4 (2) in a 68% yield (eq 1).

The reaction gave similar yields when 1-octene was used as the hydrogen acceptor instead of 1-heptene. The 1H NMR spectrum of 2 is consistent with a cis geometry about the diCp ligand with two different resonances for the gem-CMe2 groups. The symmetrical cyclopentadienyl ring hydrogens appear as a doublet and a triplet in a 2:1 ratio in the 1H NMR spectrum. The IR spectrum (ν(CO) = 1996, 1935, 1922 cm-1) and the 13C NMR spectral shift of the CO resonance (205 ppm) suggest that the CO ligands are terminally bound and that there no bridging CO ligands.4 Angelici and co-workers have also observed only the terminal CO arrangement in the (C5H3)2(SiMe2)2 system.5 Reaction of 2 with 1 equiv of Br2 in CH2Cl2 gave cis{(η5-C5H3)2(CMe2)2}Ru2(CO)4Br2 (3), with an 88% yield (eq 2).

The spectroscopic evidence for 3 is very straightforward and is similar to that reported by Angelici and co-workers for the analogous complex with SiMe2 linkers. The 1H NMR spectrum has the characteristic doublet and a triplet in the 5.2-5.7 ppm range for the symmetrical dicyclopentadienyl ring protons. The IR spectrum showed only terminal CO ligands with ν(CO) = 2041, 1986 cm-1. Special care was taken to add exactly 1 equiv of Br2 to the reaction since an excess of Br2 gave an unidentified product with two broad resonances at 5.97 and 4.91 ppm in CDCl3. Should this product form in the reaction, it can be removed by filtering the CH2Cl2 solution of 3 using a Celite padded frit. We are currently working on trying to isolate and fully characterize this unknown product. The reaction of 3 with either 1 equiv or an excess of AgOTf at room temperature gave the cationic μ-Br complex (3) Amor, F.; de Jesus, E.; Perez, A. I.; Royo, P.; Vazquez de Miguel, A. Organometallics 1996, 15, 365–369. (4) Cotton, F. A.; Yagupsky, G. Inorg. Chem. 1967, 6, 15–20. (5) Ovchinnikov, M. V.; Klein, D. P.; Guzei, I. A.; Choi, M.; Angelici, R. J. Organometallics 2002, 21, 617–627.

Figure 1. ORTEP diagram of asymmetric cis-4 (50% probability). Hydrogens and OTf- are omitted for clarity. Selected bond distances (A˚) and angles (deg): Ru(1) 3 3 3 Ru(2), 4.061(1); Ru(1)-Cp(centroid), 1.87; Ru(1)-Br(1), 2.539(1); Ru(2)-Br(1), 2.540(1); C(1)-Ru(1)-Br(1), 89.7(3); C(2)-Ru(2)-Br(1), 91.5(3); C(1)-Ru(1)-C(2), 89.9(4); C(3)-Ru(2)-Br(1), 90.7(3); C(4)-Ru(2)-Br(1), 92.0(3); C(3)-Ru(2)-C(4), 89.4(4); Cp(centroid)-Ru(1)-Ru(2)-Cp(centroid) torsion angle, 0.1; CpCp fold angle, 164.8(4).

cis-[{(η5-C5H3)2(CMe2)2}Ru2(CO)4(μ-Br)][OTf] (4) in a 92% yield (eq 3).

The solid-state study revealed two independent molecules in the unit cell that are different conformational isomers of 4. Each ruthenium metal center has a piano stool configuration, and the main structural difference between the two independent molecules is the orientation of the piano stool legs relative to each metal center. The first isomer (asymmetric isomer) has Cs symmetry with the legs of the piano stool twisted so that the Ru-Br-Ru plane is not perpendicular to the plane of the middle ring of the dicyclopentadienyl ligand. The Ru 3 3 3 Ru nonbonding distance is 4.061(1) A˚ (Figure 1). The second isomer is more symmetrical, with the legs of the piano stool rotated so that the Ru-Br-Ru plane is almost perpendicular to the middle ring of the dicyclopentadienyl ligand. This conformation is closer to having C2v symmetry. The two ruthenium centers are further apart (4.240(1) A˚) in this more symmetrical conformation (Figure 2). This greater distance is also reflected in a bigger Cp-Cp fold angle for the symmetric conformer, 172.0°, versus a fold angle of 164.7° for the asymmetric conformer.6 The angles between the legs of the stools are all approximately 90° in both conformers, with only a slight rotation about the Ru-Cp bond needed to go from one conformer to the other. Angelici and co-workers have also reported a similar situation where the unit cell of (6) The Cp-Cp fold angle is defined as the angle between the two Cp ring planes and does not use the bridging carbons when calculating the angles.

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Figure 2. ORTEP diagram of symmetric cis-4 (50% probability). Hydrogens and OTf- are omitted for clarity. Selected bond distances (A˚) and angles (deg): Ru(3) 3 3 3 Ru(4), 4.240(1); Ru(3)-Cp(centroid), 1.86; Ru(3)-Br(2), 2.540(1); Ru(4)Br(2), 2.532(1); C(5)-Ru(3)-Br(2), 91.0(4); C(6)-Ru(3)Br(2), 90.2(4); C(5)-Ru(3)-C(6), 91.5(5); C(7)-Ru(4)Br(2), 91.2(3); C(8)-Ru(4)-Br(2), 89.3(3); C(7)-Ru(4)-C(8), 90.3(6); Cp(centroid)-Ru(3)-Ru(4)-Cp(centroid) torsion angle, 0.0; Cp-Cp fold angle, 172.1(5).

cis-{(η5-C5H3)2(SiMe2)2}Ru2(μ-SnCl2)(CO)4 contained three different independent molecules. Two of the independent molecules are in the more symmetric configuration, while the third molecule is in the less symmetric configuration.5 Since only a single set of resonances for one compound is observed in the 1H NMR spectrum, the interconversion between the conformers must be rapid on the NMR time scale, or only one conformer is present in solution. The dicyclopentadienyl ring hydrogens are the usual double and triplet in the 1H NMR spectrum, indicating a symmetrical environment for the dicyclopentadienyl ligand. The bridging bromo ligand has a remarkable inert quality to it since even an excess of AgOTf in refluxing acetonitrile at ambient pressure fails to remove it. This inert reactivity is similar to what Angelici has observed for other ruthenium complexes with a doubly linked Cp ligand. The inertness of the bridging ligand, whether is it is a halo or hydrido ligand, seems to be a common characteristic among these types of complexes.5,7 A mixture of 3, AgOTf, and Me3NO, refluxed in MeCN at ambient pressure for 18 h, yields cis-[{(η5-C5H3)2(CMe2)2}Ru2(CO)2(MeCN)2(μ-Br)][OTf] (5), a complex where the bridging bromide is still present but two of the CO ligands have now been replaced with acetonitrile ligands to yield syn5 and anti-5 in a 1:1 ratio (CD3CN solvent) and an overall 71% yield (eq 4).

The 1H NMR spectrum for syn-5 (Cs symmetry) has four separate resonances for the gem-CMe2 linkers since the methyl groups are now all inequivalent, while the anti isomer (7) Ovchinnikov, M. V.; LeBlanc, E.; Guzei, I. A.; Angelici, R. J. J. Am. Chem. Soc. 2001, 123, 11494–11495.

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Figure 3. ORTEP diagram of syn-5 (50% probability). Hydrogens and OTf- are omitted for clarity. Selected bond distances (A˚) and angles (deg): Ru(1) 3 3 3 Ru(2), 4.2243(6); Ru(1)-Cp(centroid), 1.83; Ru(1)-Br(1), 2.5459(7); Ru(2)-Br(1), 2.5604(7); Ru(1)-N(1), 2.056(3); Ru(1)-C(1), 1.879(6); N(1)-Ru(1)-Br(1), 82.3(1); C(1)-Ru(1)-Br(1), 90.7(2); N(1)-Ru(1)-C(1), 93.5(2); Ru(1)-N(1)-C(3), 173.7(4); Ru(1)-C(1)-O(1), 173.8(4); Cp(centroid)-Ru(1)-Ru(2)-Cp(centroid) torsion angle, 1.3; CpCp fold angle, 171.8(3).

(C2 symmetry) has only two resonances for the gem-CMe2 units. Also, due to the greater asymmetry of 5, each isomer displays three resonances for the ring hydrogens instead of the standard doublet and triplet for the more symmetrical complexes. The solid-state structure of syn-5 confirmed the presence of the bridging Br- ligand and the overall proposed structure based on the NMR spectral data (Figure 3). The bridging Br ligand is bound symmetrically between the two ruthenium metal centers similar to that of the symmetric conformer of 4. The ruthenium centers each have a piano stool configuration with the Ru 3 3 3 Ru distance of 4.2243(6) A˚ and a Cp-Cp fold angle of 171.8°. These values are similar to the observed values in the symmetrical conformer of 4. Both the CO and acetonitrile ligands are linearly bound with a Ru(1)-N(1)-C(3) angle of 176.1(4)° and a Ru(1)-C(1)-O(1) angle of 174.5(4)°. The interconversion between the syn and anti isomers is an interesting one. A variable-temperature NMR spectral study of a mixture of the syn and anti isomers (25-50 °C) in CDCl3 shows no broadening of the resonances or a change in the ratio of the isomers. This leads us to believe that an interconversion of the two isomers, via the breaking of the bridging Br bond and rotation about a Ru-Cp bond followed by reconnection of the Br bridge, is not occurring at 50 °C or lower. However, we do observe that the syn:anti isomeric ratio changes with the amount of free acetonitrile present in the NMR sample. A 1H NMR spectrum in CDCl3 with no free acetonitrile present shows a 2:1 ratio of syn:anti isomers. Addition of ∼20 mg of MeCN to the sample changes the ratio of syn:anti to 1:1 within 5 min. This would suggest that free acetonitrile plays a role in the interconversion of the two isomers. Two possible mechanisms that would explain how MeCN facilitates the interconversion are as follows: either the rapid dissociation and reassociation of the MeCN ligands from the ruthenium centers or a MeCN-promoted Ru-Br bond cleavage followed by rotation about the Cp-Ru bond and re-formation of the Ru-Br.

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In order to remove the bridging Br- ligand, a higher reaction temperature and pressure were used. Reaction of 2 with 2 equiv of AgOTf under microwave conditions (125 psi, ∼160 °C, MeCN, 60 min) gave a tetraacetonitrile complex, cis-[{(η5-C5H3)2(CMe2)2}Ru2(CO)2(MeCN)4][OTf]2 (6), in a 61% yield (eq 5).

The presence of a total of four acetonitrile ligands was determined by the 1H NMR spectrum of 6 in CDCl3, where the integration of the bound acetonitrile resonances matches that of four acetonitrile ligands. The complete loss of the Br- ligands was confirmed by the reaction of 5 with 1 equiv of AgOTf under microwave conditions (30 min, 125 psi, ∼160 °C, MeCN). The presence of AgBr in the reaction tube along with the formation of 6 suggests that there are no Br- ligands present in 6 (eq 6).

The presence of the terminal CO ligands in 6 is supported by the IR spectrum (ν(CO) = 1993 cm-1) and the 13C NMR spectrum with a resonance of 200.3 ppm for the bound CO. Longer reaction times (∼1.5 h) did not yield any of the hexakisacetonitrile complex, where the final two CO ligands were substituted for acetonitrile ligands. All of the CO ligands can be removed when benzene is used as a 6-electron donor ligand. Reaction of 2 with 2 equiv of AgOTf and a 1:1 mixture of benzene and acetonitrile under microwave conditions gave the corresponding bisbenzene complex cis-[{(η5-C5H3)2(CMe2)2}Ru2(η6-C6H6)2][OTf]2 (7) in a 64% yield (eq 7). Using conventional heating methods by running the reaction at ambient pressure in refluxing acetonitrile gave 7 in a 29% yield after 21 days.

The NMR spectroscopic data for 7 are consistent with a benzene being bound (upfield shift of the benzene resonances, in both the 1H and 13C NMR spectra). Integration of the resonances in the 1H NMR spectrum gave a 12 (C6H6):2:4 (diCp ring Hs):6:6 (gem-CMe2) ratio, consistent with one benzene being bound to one ruthenium center. Complex 7 is air stable both in the solid state and in solution, but it does decompose when it is passed through a silica gel

Figure 4. ORTEP diagram of 7 (50% probability). Hydrogens and OTf- are omitted for clarity. Only one of the two similar cations is shown. Selected bond distances (A˚) and angles (deg): Ru(1) 3 3 3 Ru(2), 5.2025(9); Ru(1)-Cp(centroid), 1.82; Ru(1)benzene(centroid), 1.70; Cp(centroid)-Ru(1)-benzene(centroid), 174.6; Cp(centroid)-Ru(1)-Ru(2)-Cp(centroid) torsion angle, 0.7; Cp-Cp fold angle, 201.5(3).

Figure 5. ORTEP diagram of 10 (50% probability). Hydrogens are omitted for clarity. Selected bond distances (A˚) and angles (deg): Ru(1) 3 3 3 Ru(2), 5.0602(3); Ru(1)-Cp(centroid), 1.85; Ru(1)-dienyl(centroid), 1.70; Cp(centroid)-Ru(1)-dienyl(centroid), 176.7; Cp(centroid)-Ru(1)-Ru(2)-Cp(centroid) torsion angle, 2.6; Cp-Cp fold angle, 196.6(1).

column. Complex 7 is best purified by recrystallization using a MeCN/CH2Cl2 mixture. The crystal structure of 7 shows the ruthenium metal centers at a much greater distance than in 3 and 5 (5.2025(9) A˚) and the Cp-Cp fold angle (201.5°) being greater than 180° (Figure 4). The ruthenium metal centers now occupy the convex face of the dicyclopentadienyl ligand due to the Cp-Cp fold angle being greater than 180°. The Cp(centroid)-Ru(1)-benzene(centroid) angle of 174.61° deviates slightly from 180°. All of these observations are attributed to the greater steric crowding by the two benzene ligands. With complex 7 in hand, we were excited by the possibility of being able to make [cis-{(η5-C5H3)2(CMe2)2}Ru2(MeCN)6][OTf]2 (8), a compound where the benzene ligands have been replaced by three acetonitrile ligands on each ruthenium center. Mann and others have reported that photolysis of [CpRu(η6-C6H6)]þ in acetonitrile yields the synthetically versatile trisacetonitrile complex [CpRu(MeCN)3)]þ.8

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Photolysis of 7 in MeCN over a 48 h period gave complex 8 but only in ∼30% yield. The major product after 48 h of photolysis was [cis-{(η5-C5H3)2(CMe2)2}Ru2(MeCN)3(η6C6H6) ][OTf]2 (9) (eq 8). The 1H NMR spectrum of 9 has four resonances for the ring hydrogens in a 2:1:1:2 ratio along with two resonances for the gem-CMe2 linkers. The Cp resonances of the ruthenium with the three acetonitrile ligands are shifted upfield to the 4-5 ppm range similar to the observed Cp resonance of 4.31 ppm in the [CpRu(MeCN)3]þ complex.8a

Complete removal of the free benzene along with the reaction solvent and recharging the reaction with fresh acetonitrile did not succeed in converting all of 9 over to 8. The best ratio that was achieved was a 1:2 ratio of 9:8 after 4 days of photolysis. We then decided to seek a nonphotolytic way to displace the benzene ligands from the ruthenium metal centers. Our approach to removing the benzene ligands was to disrupt the aromaticity of the benzene ligands by first performing a nucleophilic addition (H-) followed by an electrophilic addition (Hþ) to the benzene ligands, with the hope that the resulting 1,3-cyclohexadiene ligands would be labile in an acetonitrile solution. Reaction of 7 with LiAlH4 in THF at 22 °C followed by a MeOH quench gave the neutral air-stable cis-{(η5-C5H3)2(CMe2)2}Ru2(η5-C6H7)2 (10) in 57% yield (eq 9).

The 1H NMR spectrum shows two resonances for the methylene hydrogens of the cyclohexadienyl ligands at 2.92 and 2.63 ppm and three resonances for the pentadienyl protons at 5.97, 4.55, and 2.63 ppm, which is the expected number of resonances based on the proposed structure. The chemical shifts also closely match the reported resonances of CpRu(η5-C6H7).9 The cyclopentadienyl ring hydrogens in the 1H NMR spectrum are a doublet and a triplet, consistent with the proposed symmetrical structure. The crystal structure of 10 shows the two ruthenium metal centers being fairly (8) (a) Gill, T. P.; Mann, K. R. Organometallics 1982, 485–488. (b) Trost, B. M.; Older, C. M. Organometallics 2002, 21, 2544–2546. (9) (a) Gusev, O. V.; Ievlev, M. A.; Peterleitner, M. G.; Peregudova, S. M.; Denisovich, L. I.; Petrovskii, P. V.; Ustynyuk, N. A. J. Organomet. Chem. 1997, 534, 57–66. (b) Vol'kenau, N. A.; Bolesova, I. N.; Shul'pina, L. S.; Kitaigorodskii, A. N. J. Organomet. Chem. 1984, 267, 313–321.

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far apart at a distance of 5.0602(3) A˚ and a Cp-Cp fold angle being greater than 180°, with an angle of 196.6° (Figure 5). Reaction of 10 with 2 equiv of HOTf in an acetonitrile/ Et2O solvent mixture afforded 8 in an 88% yield along with free 1,3-cyclohexadiene (eq 10).

The 1H NMR spectrum of 8 has the characteristic doublet and triplet for the dicyclopentadienyl ring protons of a symmetric diruthenium complex, and the Cp ring hydrogens are shifted upfield to the 4-5 ppm region. The chemical shifts of the Cp ring hydrogens are similar to what is observed for [CpRu(MeCN)3]þ. The coordinated acetonitrile ligands are not observed in CD3CN probably due to fast exchange with the deuterated solvent, but the bound acetonitriles are observed in 1,2-dichloroethane-d4 and the integration matches the presence of six acetonitrile ligands. Complex 8 decomposes in solvents other than acetonitrile, forming unidentifiable products in acetone-d6, CDCl3, CD3NO2, and CD2Cl2. We are currently investigating the substitution chemistry of 8. There is a competitive oxidative side reaction that occurs during the synthesis of 8. Complex 10 is easily reoxidized back to either 9 or 7 depending on the amount of triflic acid and the solvent combination used. In order to reduce the acid strength of the triflic acid, we used an Et2O/HOTf combination and have found that this combination minimized the formation of 9 and 7 but did not completely eliminate the formation of the side products. There was still ∼5% (based on the 1H NMR spectrum of the crude reaction mixture) of 9 that was formed during the synthesis of 8.

Conclusions There is synthetic utility to using the small CO ligand to favor the formation of the cis isomer over the trans isomer in diruthenium complexes containing a doubly linked Cp ligand. Partial or complete removal of the CO ligands can be achieved using moderately high temperatures and pressures (∼160 °C, 100-125 psi) with acetonitrile or acetonitrile/benzene solvent mixtures. The coordinated benzene ligands can be transformed to labile 1,3-cyclohexadiene ligands via a sequential H-/Hþ addition, and the resulting metal complex, 8, has six labile acetonitrile ligands. We hope that this complex will be as synthetically useful as the mononuclear analogue, [CpRu(MeCN)3]þ.

Experimental Section General Procedures. Reactions that required inert conditions were performed using modified Schlenk techniques or in an MBraun Unilab glovebox under a nitrogen atmosphere. 1H and 13 C NMR spectra were recorded on Varian Unity Inova 400 MHz or GE-QE 300 MHz spectrometers. 1H and 13C NMR chemical shifts are given relative to the residual proton or 13C solvent resonances. X-ray data were collected on a Bruker SMART Apex II CCD Platform diffractometer. IR spectra were recorded with a ThermoScientific Nicolet IR200 FT-IR spectrometer using either the attenuated total reflectance (ATR-IR)

Article attachment on a ZnSe crystal or a PTFE card from International Crystal Laboratories. The microwave apparatus was constructed as described in the literature.10 Special care was taken to incorporate all of the described safety features when building the microwave apparatus, including the use of a pressure relief valve and a pressure sensor to control the microwave output. Also, to reduce the chances of a catastrophic rupture of the glass tube, we ran our reactions between 100 and 125 psi, about 25 psi below the 150 psi rating for the Ace pressure tube (8648-26). The microwave apparatus was used in a fume hood that was free of solvents and behind a protective shield to minimize any damage should a rupture occur. Photolysis reactions were conducted using a Rayonet photochemical reactor, model RPR-100, equipped with 350 nm bulbs. UV-vis spectra were recorded on a Shimadzu UV2401PN spectrometer. Solvents and Reagents. Unless otherwise indicated, all chemicals were used as received (reagents from Aldrich, Acros, Alfa Aesar, or Strem Chemical Company). Deuterated solvents were obtained from Cambridge Isotope Laboratories. Tetrahydrofuran (THF), benzene, diethyl ether, pentane, and C6D6 were distilled from dark purple solutions of sodium benzophenone ketyl. MeCN, CD3CN, CH2Cl2, CDCl3, and CD2Cl2 were distilled from a suspension of CaH2. Elemental analyses were performed by Atlantic Microlab (Norcross GA). 4,4,8,8-Tetramethyl1,4,5,8-tetrahydro-s-indacene, 1a, and 4,4,8,8-tetramethyl-1,4,7,8tetrahydro-s-indacene, 1b were prepared as described.11 Ru3(CO)12 was prepared as described.12 Me3NO 3 H2O was heated to 100 °C under vacuum for 18 h before use. Preparation of cis-{(η5-C5H3)2(CMe2)2}Ru2(CO)4 (2). A mixture of 1a and 1b (498.7 mg, 2.349 mmol), Ru3(CO)12 (1.001 g, 1.566 mmol), and 1-heptene (4.0 g, 40.8 mmol) was refluxed in heptane (130 mL) for 3 days. The resulting dark brown mixture was cooled to room temperature, and the solvent and volatile organic products were removed by rotary evaporation. CH2Cl2 (50 mL) was added to the brown solid to dissolve 2, and the mixture was filtered to remove an insoluble brown material. The CH2Cl2 solution was collected and the CH2Cl2 removed by rotary evaporation. The solid was washed with hexanes (125 mL) and filtered using a SiO2-padded frit. The product was then collected by washing the SiO2 padded frit with CH2Cl2, collecting the CH2Cl2 solution, and removing the CH2Cl2 to give a brown solid (832.2 mg, 68% yield). 1 H NMR (400 MHz, CDCl3, 21 °C): δ 5.34 (t, J = 2.7 Hz, 2H), 5.06 (d, J = 2.7 Hz, 4H), 1.73 (s, 6H), 1.29 (s, 6H). 13C{1H} NMR (75 MHz, CDCl3 20 °C): δ 205.5 (CO), 110.7 (quat C), 81.6 (CH), 78.1 (CH), 34.6 (CMe2), 32.9 (CH3), 32.2 (CH3). IR (ZnSe): ν(CO) (cm-1) 1935 (vs), 1922 (vs). Anal. Calcd for C20H18O4Ru2: C, 45.80; H, 3.46. Found: C, 45.57; H, 3.41 Preparation of cis-{(η5-C5H3)2(CMe2)2}Ru2(CO)4Br2 (3). Complex 2 (1.041 g, 1.99 mmol) was dissolved in CH2Cl2 and treated with 2.18 mL of a Br2 solution (1.457 g Br2 in 10 mL of CH2Cl2); a total of 1.99 mmol of Br2 was added to the reaction. Upon stirring at 22 °C for 10 min, the initial orange solution turned brown. The reaction was monitored using 1H NMR spectroscopy. Removal of solvent by rotary evaporation yielded a yellow-green solid. The crude product was washed twice with (10 mL) benzene. The resulting solid was extracted with CH2Cl2 to give a brown solution and green solid on the frit. The solvent was removed by rotary evaporation to give a yellow-orange solid determined to be clean product by the 1H NMR spectrum (1.198 g, 88.0% yield). 1H NMR (400 MHz, CDCl3, 21 °C): δ 5.65 (t, J = 2.9 Hz, 2H), 5.28 (d, J = 2.9 Hz, 4H), 1.66 (s, 6H), 1.58 (s, 6H). 13C{1H} NMR (75 MHz, CDCl3 20 °C): δ 195.9 (10) Mingos, D.; Michael, P.; Baghurst, D. R. Dalton Trans. 1992, 1151–1155. (11) Chin, R. M.; Maurer, D.; Parr, M.; Allworth, N.; Schwenker, R.; Sullivan, D.; Enabnit, S.; Brennessel, W. Inorg. Chim. Acta 2009, 362, 389–394. (12) Faure, M.; Saccavini, C.; Lavigne, G. Chem. Commun. 2003, 1578–1579.

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(CO), 112.7 (quat C), 98.3 (CH), 77.6 (CH), 36.1 (CH3), 32.6 (CH3), 31.9 (CMe2). IR (ZnSe): ν(CO) (cm-1) 2041 (s), 1984 (vs). Anal. Calcd for C20H18Br2O4Ru2: C, 35.10; H, 2.65. Found: C, 34.87; H, 2.83. Preparation of [cis-{(η5-C5H3)2(CMe2)2}Ru2(CO)4(μ-Br)]OTf (4). A suspension of 3 (118.7 mg, 0.1736 mmol) and AgOTf (45.8 mg, 0.1783 mmol) was prepared in CH2Cl2 (10 mL) and wrapped in Al foil. After stirring overnight the solvent was removed by rotary evaporation, and the resulting light orange solids were washed with CHCl3 (3  8 mL) on a Celite-padded frit. The product was then extracted with CH2Cl2 (25 mL) and the solvent removed to give bright orange solids (120.1 mg, 92%). 1H NMR (300 MHz, CD3NO2, 21 °C): δ 5.99 (d, J = 2.6 Hz, 4H), 4.94 (t, J = 2.6 Hz, 2H), 1.84 (s, 6H), 1.65 (s, 6H). 13 C{1H} NMR (75 MHz, CD3NO2, 20 °C): δ 195.6 (CO), 119.9 (quat C), 86.2 (CH), 72.3 (CH), 33.5 (CH3), 31.8 (CMe2), 29.38 (CH3). IR (ZnSe): ν(CO) (cm-1) 2053 (s), 2013 (vs), 1997 (s). Anal. Calcd for C21H18BrF3O7Ru2S: C, 33.48; H, 2.40. Found: C, 33.55; H, 2.31. Preparation of [cis-{(η5-C5H3)2(CMe2)2}Ru2(CO)2(MeCN)2(μ-Br)]OTf (5). In the glovebox, 3 (62.0 mg, 0.091 mmol) was dissolved/suspended in dry acetonitrile to give a yellow solution. AgOTf (25.3 mg, 0.098 mmol) and Me3NO (19.5 mg, 0.26 mmol) were added, resulting in a dark orange-red solution. The reaction mixture was refluxed in the dark and under nitrogen for 18 h, at which time the solution became a dark red-brown color. The solvent was removed under reduced pressure and the residue redissolved in dry acetonitrile. The mixture was filtered through a Celite-padded frit to remove the AgBr. The orange filtrate was collected, and the solvent was removed to give a red solid. The product was recrystallized using CH2Cl2/pentane at -20 °C. Two crops of crystals were collected to afford pure 5 (50.0 mg, 71%). syn-5: 1H NMR (400 MHz, CDCl3, 21 °C): δ 5.62 (m, 2H), 4.60 (m, 2H), 4.49 (t, J = 2.5 Hz, 2H), 2.51 (s, 6H), 1.86 (s, 3H), 1.69 (s, 3H), 1.49 (s, 3H), 1.13 (s, 3H). anti-5: 1H NMR (400 MHz, CDCl3, 21 °C): δ 5.56 (m, 2H), 4.65 (m, 2H), 4.51 (t, J = 2.5 Hz, 2H), 2.49 (s, 6H), 1.60 (s, 6H), 1.47 (s, 6H). 13C{1H} NMR (100 MHz, CD3CN, 20 °C): δ 200.9, 200.8 (CO); 100.7, 96.7, 90.74, 89.9, 76.1, 74.6, 65.5, 64.7 (all Cp carbons, mix of quat and CH); 35.0, 33.9, 32.7, 32.4, 30.4, 30.0, 28.6, 28.4, 26.9 (mix of CH3 and C(CH3)2). Anal. Calcd for C23H24BrF3N2O5Ru2S: C, 35.44; H, 3.10. Found: C, 34.79; H, 2.92. Microwave Synthesis of [cis-{(η5-C5H3)2(CMe2)2}Ru2(CO)2(MeCN)4][OTf]2 (6). In an inert atmosphere, 3 (200 mg, 0.265 mmol), AgOTf (68.3 mg, 0.267 mmol), and dry MeCN (12 mL) were loaded into a pressure tube. The solution was then heated in a pressure-controlled microwave apparatus for 60 min at 125 psi. The reaction was cooled to room temperature, and the contents of the pressure tube were quickly transferred to a round-bottom flask in the air. The solvent was then removed in vacuo. The solids were extracted with MeCN and filtered through a Celite-padded frit. The solvent was again removed in vacuo to give the product as a brown-yellow solid (149.7 mg, 61%). We were unable to obtain a satisfactory elemental analysis due to the impurities precipitating with the product during the attempted recrystallizations. 1H NMR (400 MHz CDCl3, 21 °C): δ 5.40 (t, J = 2.7 Hz, 2H), 5.00 (d, J = 2.7 Hz, 4H), 2.58 (s, 12 H), 1.52 (s, 6H), 1.50 (s, 6H). 1H NMR (400 MHz CD3CN, 21 °C): δ 5.33 (t, J = 2.7 Hz, 2H), 5.07 (d, J = 2.7 Hz, 4H), 1.48 (s, 12H). 13C{1H} NMR (100 MHz, CD3CN, 20 °C): δ 200.3 (CO), 110.1, 87.7, 73.3, 36.1, 33.4, 29.7. IR (PTFE): (cm-1) ν(CO) = 1993 (s). Microwave Synthesis of [cis-{(η5-C5H3)2(CMe2)2}Ru2(η6C6H6)2][OTf]2 (7). A mixture of 3 (249.4 mg, 0.365 mmol), AgOTf (196 mg, 0.763 mmol), MeCN (14 mL), and C6H6 (6 mL) was placed into a pressure tube and heated in a pressurecontrolled microwave apparatus for 40 min at a pressure of 120 psi. Reaction completeness was signaled by formation of a pale yellow solution and confirmed by 1H NMR spectroscopy. The solution

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was filtered using a Celite-padded frit and the solid residue washed with MeCN (15 mL). The solvent was removed by rotary evaporation and the solids washed with CH2Cl2 (3  10 mL). The resulting off-white solids were dissolved in MeCN and crystallized by vapor diffusion of CH2Cl2 into the MeCN solution to give beige rod-like crystals (202 mg, 64%). Single crystals, formulated as 7 3 C6H5N 3 1/2H2O, were grown from the slow evaporation of a pyridine solution. Conventional Synthesis of [cis-{(η5-C5H3)2(CMe2)2}Ru2(η6C6H6)2][OTf]2 (7). Complex 3 (152.5 mg, 0.223 mmol), AgOTf (122.5 mg, 0.478 mmol), Me3NO (67.5 mg, 0.9 mmol), MeCN (10 mL), and C6H6 (3 mL) were added together and refluxed under nitrogen for 21 days. The reaction mixture was cooled and filtered through a Celite-padded frit to remove the AgBr. The solvent was removed to afford a dark red oil. Addition of CH2Cl2 to the oil gave an off-white solid, which was collected by filtration. The resulting solid was recrystallized from a CH3CN/CH2Cl2 mixture. Two crops of crystals were collected (combined 56.5 mg, 29% yield). 1H NMR (400 MHz, CD3COCD3, 21 °C): δ 6.58 (s, 12H) 5.72 (t, J = 2.3 Hz, 2H), 5.34 (d, J = 2.3 Hz, 4H), 1.75 (s, 6H), 1.54 (s, 6H). 13C{1H} NMR (75 MHz, CD3COCD3, 20 °C): δ 112.32 (quat C), 88.11 (CH), 78.91 (CH), 75.59 (CH), 39.51 (CH3) 35.45 (CH3), 31.88 (quat C). UV-vis (CH3CN): λmax = 338 (ε = 533 M-1 cm-1). Anal. Calcd for C30H30F6O6Ru2S2: C, 41.57; H, 3.49. Found: C, 40.95; H, 3.52. Synthesis of cis-{(η5-C5H3)2(CMe2)2}Ru2(η5-C6H7)2 (10). Solid LiAlH4 (56.0 mg, 1.48 mmol) was slowly added to a stirred suspension of 7 (157.6 mg, 0.182 mmol) in THF (6 mL) at 22 °C. After stirring for 18 h at 22 °C, the reaction mixture was cooled to 0 °C, and degassed methanol (6 mL) was carefully added dropwise to the mixture. The mixture was stirred for 5 min and then allowed to warm to room temperature. The solvent was removed under vacuum to give a gray solid. The product was extracted with benzene (25 mL) and filtered through a Celitepadded frit to give a pale yellow solution. The solvent was removed, and the resulting solid was recrystallized from Et2O to afford pale yellow crystals (first crop of crystals, 32.7 mg; second crop of crystals, 26.7 mg; combined yield of 59.4 mg, 57%). 1H NMR (400 MHz, C6D6, 21 °C): δ 5.97 (m, 2H), 5.11 (t, J = 2.3 Hz, 2H), 4.55 (m, 4H), 4.46 (d, J = 2.3 Hz, 4H), 2.92 (m, 2H), 2.63 (m, 6H), 1.32 (s, 6H), 1.08 (s, 6H). 13C{1H} NMR (75 MHz, C6D6 20 °C): δ 106.2 (quat C, Cp), 81.8 (CH, dienyl), 80.1 (CH, dienyl), 74.0 (CH, Cp), 70.3 (CH, Cp), 37.4 (CH3), 37.3 (CH3), 31.8 (quat C, CCH3), 31.0 (CH2), 22.9 (CH, dienyl). Anal. Calcd for C28H32Ru2: C, 58.93; H, 5.65. Found: C, 58.94; H, 5.63. Preparation of [cis-{(η5-C5H3)2(CMe2)2}Ru2(MeCN)6][OTf]2 (8). Complex 10 (52.8 mg, 0.092 mmol) was suspended in MeCN (898.2 mg). In a separate vial HOTf (35.2 mg, 0.235 mmol) and Et2O (206.3 mg) were combined, and the acidic Et2O solution was added dropwise to the stirred dienyl suspension. The mixture quickly became a clear orange solution within 30 s of the addition of the acid. The orange solution was then added dropwise to a stirred Et2O solution to give a yellow precipitate. The Et2O mixture was then cooled for 15 min in a -20 °C freezer to complete the precipitation process. The suspension was filtered and the resulting pale yellow solid washed with 2  10 mL of Et2O to afford 78.0 mg of product (88%). 1H NMR (400 MHz CD3CN, 20 °C); δ 4.30 (t, J = 2.3 Hz, 2H), 4.13 (d, J=2.3 Hz, 4H), 1.57 (s, 6H), 1.29 (s, 6H); (400 MHz, 1,2dichloroethane-d4, 20 °C): 4.19 (br s, 2H), 4.07 (br s, 4H), 2.39 (br s, 18H), 1.56 (s, 6H), 1.30 (s, 6H). 13C{1H} NMR (75 MHz, CD3CN, 20 °C): δ 96.3 (quat C), 73.0 (CH), 61.1 (CH), 37.0 (CH3), 33.0 (quat C), 29.1 (CH3). Anal. Calcd for C30H36F6N6O6Ru2S2: C, 37.66; H, 3.79. Found: C, 37.10; H, 3.62. Photolysis of [cis-{(η5-C5H3)2(CMe2)2}Ru2(η6-C6H6)2][OTf]2 (7). A solution of 7 (10 mg) in dry CD3CN (1 mL) was photolyzed at 350 nm in a J. Young NMR tube. The reaction was monitored by 1H NMR spectroscopy at 48 h, 4 days, and 6 days. After 48 h, the photolysis produced [cis-{(η5-C5H3)2(CMe2)2}Ru2-

Chin et al. (η6-C6H6)(MeCN)3][OTf]2 (9) and [cis-{(η5-C5H3)2(CMe2)2}Ru2(MeCN)6][OTf]2 (8) in a 1:0.4 ratio. At this point the solvent and free benzene were removed under reduced pressure and fresh CD3CN was added to the reaction. Further photolysis changed the ratio of 9:8 to 1:2 after 4 days. Once again all of the solvent and free benzene were removed under reduced pressure and the tube was recharged with fresh CD3CN. The ratio of 9:8 after 6 days was 1.0:1.4, which would indicate a decrease in the amount of 8. Spectral data for 9: 1H NMR (400 MHz, CD3CN, 21 °C): 6.24 (s, 6H), 5.32 (d, J = 2.5 Hz, 2H), 5.25 (t, J = 2.5 Hz, 1H), 4.70 (t, J = 2.3 Hz, 1H), 4.05 (d, J = 2.3 Hz, 2H), 1.56 (s, 6H), 1.33 (s, 6H). Spectral data for 8: 1H NMR (400 MHz, CD3CN, 21 °C): 4.30 (t, J = 2.3 Hz, 2H), 4.13 (d, J = 2.3 Hz, 4H), 1.57 (s, 6H), 1.29 (s, 6H) X-ray Crystallography. Each crystal was placed onto the tip of a glass fiber and mounted on a Bruker SMART Platform diffractometer equipped with an APEX II CCD area detector. All data were collected at 100.0(1) K using Mo KR radiation (0.71073 A˚, graphite monochromator).13 For each sample a preliminary set of cell constants and an orientation matrix were determined from reflections harvested from three orthogonal wedges of reciprocal space. Full data collections were carried out with frame exposure times of 25-90 s at detector distances of 4 cm. Randomly oriented regions of reciprocal space were surveyed for each sample: four major sections of frames were collected with 0.50° steps in ω at four different j settings and a detector position of -38° in 2θ. The intensity data were corrected for absorption,14 and final cell constants were calculated from the xyz centroids of approximately 4000 strong reflections from the actual data collection after integration.15 Structures were solved using SIR9716 and refined using SHELXL-97.17 Space groups were initially assigned from intensity statistics (4), systematic absences (7, 10), or both (5).18 Direct-methods solutions were calculated, which provided most non-hydrogen atoms from the difference Fourier map. Full-matrix least-squares (on F2)/difference Fourier cycles were performed, which located the remaining non-hydrogen atoms. Non-hydrogen atoms were refined with anisotropic displacement parameters, and hydrogen atoms were placed in ideal positions and refined as riding atoms with relative isotropic displacement parameters. All refinements were run to mathematical convergence. The asymmetric unit of the structure of 4 contains two independent (and conformationally different) cations, two independent anions, and highly disordered unidentified solvent, with all atoms in general positions. The reflection contributions from the solvent were removed using the program PLATON, with the function SQUEEZE,19 which determined there to be 158 electrons in 243 A˚3 removed per unit cell. Since the identity and amount of solvent were unknown, it was not included in the molecular formula; thus, all calculated quantities that derive from the molecular formula (F(000), density, molecular weight, etc.) are known to be incorrect. The carbonyl ligands of one of the independent diruthenium species appeared to be slightly disordered; however, no successful disorder model was achieved. The carbon atoms and oxygen atoms were restrained to have similar anisotropic displacement parameters, respectively. Also, one triflate anion was modeled as disordered over two positions (71:29). To achieve the model, the S-O, C-F, and S-C bonding distances and the through-space O 3 3 3 O, F 3 3 3 F, and (13) APEX2, version 2009.3-0; Bruker AXS: Madison, WI, 2009. (14) Sheldrick, G. M. SADABS, version 2008/1; University of G€ottingen: G€ottingen, Germany, 2008. (15) SAINT, version 7.60A; Bruker AXS: Madison, WI, 2008. (16) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. SIR97: A new program for solving and refining crystal structures; Istituto di Cristallografia, CNR: Bari, Italy, 1999. (17) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122. (18) Allen, F. Acta Crystallogr. 2002, B58, 380–388. (19) Spek, A. L. PLATON: A multipurpose crystallographic tool, version 300106; Utrecht University: Utrecht, The Netherlands, 2003.

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Table 1 4 empirical formula fw cryst syst space group unit cell dimens

volume Z density (calcd) absorp coeff F(000) cryst color, morphology cryst size θ range index ranges reflns collected indep reflns obsd reflns max. and min. transmn data/restraint/params goodness-of-fit on F2 final R indices [I>2σ(I )] final R indices (all data) largest diff peak and hole

5

7

10

C21H18BrF3O7Ru2S 753.46 triclinic P1 a = 13.4275(19 ) A˚ b = 13.843(2) A˚ c = 15.539(2) A˚ R = 72.481(3)° β = 74.723(2)° γ = 75.042(3)° 2606.4(6) A˚3 4 1.920 Mg/m3 2.831 mm-1 1464 yellow-orange, plate

C23H24BrF3N2O5Ru2S 779.55 monoclinic Cc a = 8.4019(9) A˚ b = 15.8995(18) A˚ c = 19.762(2) A˚ R = 90° β = 90.060(2)° γ = 90° 2640.0(5) A˚3 4 1.961 Mg/m3 2.795 mm-1 1528 yellow-orange, plate

C35H36F6NO6.5Ru2S2 954.91 monoclinic P21/c a = 23.863(4) A˚ b = 16.599(3) A˚ c = 18.119(3) A˚ R = 90° β = 97.919(4)° γ = 90° 7108(2) A˚3 8 1.785 Mg/m3 1.048 mm-1 3832 colorless, plate

C28H32Ru2 570.68 orthorhombic Pbca a = 13.2933(9) A˚ b = 12.4533(8) A˚ c = 26.2599(17) A˚ R = 90° β = 90° γ = 90° 4347.2(5) A˚3 8 1.744 Mg/m3 1.403 mm-1 2304 pale yellow, block

0.24  0.14  0.03 mm3 1.57 to 26.37° -16 e h e 16, -17 e k e 17, -19 e l e 19 31 493 10 660 [R(int) = 0.0888] 6392 0.9199 and 0.5498

0.20  0.16  0.04 mm3 1.03 to 37.78° -14 e h e 14, -27 e k e 27, -34 e l e 33 29 785 13 706 [R(int) = 0.0390] 12 177 0.8964 and 0.6048

0.34  0.16  0.06 mm3 1.67 to 29.57° -33 e h e 33, -23 e k e 23, -25 e l e 25 108 501 19 916 [R(int) = 0.1059] 12 673 0.9398 and 0.7171

0.26  0.22  0.20 mm3 1.55 to 37.78° -22 e h e 22, -21 e k e 21, -45 e l e 44 101 784 11 650 [R(int) = 0.0464] 9712 0.7667 and 0.7118

10 660/151/682 0.954 R1 = 0.0569, wR2 = 0.1254 R1 = 0.1019, wR2 = 0.1402 1.706 and -0.770 e A˚-3

13 706/2/341 1.014 R1 = 0.0408, wR2 = 0.0761 R1 = 0.0501, wR2 = 0.0797 1.489 and -1.153 e A˚-3

19 916/0/946 1.049 R1 = 0.0553, wR2 = 0.1132 R1 = 0.1035, wR2 = 0.1321 1.499 and -1.045 e A˚-3

11 650/0/331 1.067 R1 = 0.0268, wR2 = 0.0585 R1 = 0.0364, wR2 = 0.0623 0.950 and -0.591 e A˚-3

O 3 3 3 F distances were restrained to be similar, respectively. Additionally, the anisotropic displacement parameters of corresponding atoms from both orientations of the anion disorder were restrained to be similar or constrained to be equivalent. Structure 5 consists of one cation and one anion in the asymmetric unit, with all atoms in general positions, and was modeled as a pseudomerohedral twin. The application of twin law, [ 1 0 0/ 0 -1 0/0 0 -1], a 180 degree rotation about direct lattice [1 0 0], improved the R1 residual from 13% to 4%. The structure of 7 contains two independent cations, two independent anions, two independent cocrystallized pyridine solvent molecules, and one cocrystallized water molecule that is linked via hydrogen bonding to a pyridine N atom and a triflate O atom. All atoms in 7 lie in general positions. Likewise all atoms in structure 10 lie in

general positions. To confirm the nature of the η5-C6H7 ligands, all hydrogen atoms on those ligands were found from the difference Fourier map and refined independently from the respective bonded carbon atoms.

Acknowledgment. We thank the National Science Foundation (CHE-0715423) for supporting this work. We also thank Mr. Bruce Early for his help in building the microwave reactor and Drs. Whittaker and Mingos for helpful discussions while building the microwave reactor. Supporting Information Available: Crystallographic data for complexes 4, 5, 7, 10 (CIF files). This material is available free of charge via the Internet at http://pubs.acs.org.