Preparation and Properties of Cyclopentadienyl Ruthenocenium

Dec 31, 2012 - Tiago F. C. Cruz , Karina Shimizu , José M. S. S. Esperança , Luís Paulo N. Rebelo , Pedro T. Gomes , José N. Canongia Lopes. Faraday ...
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Preparation and Properties of Cyclopentadienyl Ruthenocenium Complexes with 1,2-Disubstituted Benzene Ligands: Competition between Chelate Coordination and Sandwich Coordination Shotaro Mori and Tomoyuki Mochida* Department of Chemistry, Graduate School of Science, Kobe University, Rokkodai, Nada, Hyogo 657-8501, Japan S Supporting Information *

ABSTRACT: The reactions of [CpRu(NCMe)3]+ and 1,2-disubstituted benzene ligands (L) bearing donor substituents were examined to investigate the consequence of competing coordination modes. 1,2C6H4(OMe)2 and 1,2-C6H4(SMe)(OMe) produce [CpRu(η6-L)]+type sandwich complexes with a η6 coordination mode, whereas 1,2C6H4(SMe)2 forms the chelate complex [CpRu(κ2-L)(NCMe)]+, due to the coordination ability of the donor atoms. 1,2-C6H4(NMe2)2 and 1,2-C6H4(SMe)(NMe2) produce the sandwich complexes or the chelate complexes ([CpRu(κ2-L)(NCMe)n]+; n = 0 or 1) depending on the reaction conditions. The chelate complexes are the kinetic products and are thermally transformed into the sandwich complexes in solution. The hexafluorophosphate (PF 6 ) and bis(trifluoromethylsulfonyl)amide (Tf2N) salts were isolated, and their thermal properties were investigated. The Tf2N salts of the sandwich complexes are room-temperature ionic liquids. The molecular structures were determined crystallographically.

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INTRODUCTION The chemistry of cyclopentadienyl ruthenium (CpRu) complexes has been investigated extensively in terms of chemical reactivities and catalytic activities.1 One of the most versatile methods to prepare CpRu derivatives is via the cationic triacetonitrile complex [CpRu(NCMe)3]+,2 which is synthesized by UV irradiation of [CpRu(η6-C6H6)]+ in acetonitrile.3 Addition of arene-type ligands to this complex generally produces η6 coordinate sandwich complexes [CpRu(η6-arene)]+,4 which exhibit aromatic nucleophilic substitution reactions on the arene ring.5 On the other hand, the reactions of [CpRu(NCMe)3]+ and chelate ligands (L−L) with donor atoms produce chelate complexes [CpRu(L-L)(NCMe)]+.6 It has been also reported that the use of ligands such as 2aminopyridine7 and dppe8 leads to some variation in the products. Related Cp*Ru complexes (Cp* = pentamethylcyclopentadienyl) are also prepared from the corresponding triacetonitrile complex.9 CpRu complexes are of interest due to the transformation from monodentate to η6 coordination in complexes with tethered amino ligands10 and the formation of a variety of coordination modes in dinuclear complexes.11 Our idea was to investigate the coordination modes and coordination transformation of ligands having competitive coordination sites through the triacetonitrile complex. For this purpose, we have investigated the reactions of [CpRu(NCMe)3]+ and the 1,2-disubstituted ligands shown in Figure 1. These simple benzene ligands, having ortho-substituted donor atoms of O, N, and S, can adopt either the chelate or η6 coordination. We report herein the coordination modes, © XXXX American Chemical Society

Figure 1. 1,2-Disubstituted benzene ligands used in this study. Abbreviations are also shown.

structural transformations, thermal properties, and crystal structures of the cationic complexes obtained by these reactions. Hexafluorophosphate (PF6) and bis(trifluoromethylsulfonyl)amide (Tf2N) were used as the counteranions. We have recently reported that various metallocenium salts including [CpFe(η6-arene)]Tf2N become ionic liquids,12 whose melting points are below 100 °C.13 The η6-coordinated complexes with Tf2N prepared in this study were also ionic liquids. Among these salts, the preparation of [CpRu(η6-1,2-dimethoxybenzene)]PF6 has been reported in the literature.14 Received: November 8, 2012

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were observed in the range δ = 5.9−6.5 and 5.3−5.5, respectively, and the N-methyl protons in [1NN]+ and [1SN]+ were observed as a singlet at 2.80 and 2.74 ppm, respectively. The reaction of the SS, SN, and NN ligands with a suspension of [CpRu(NCMe)3]PF6 in diethyl ether or acetonitrile at room temperature afforded the chelate complexes [2L]PF6 and/or [3L]PF6, although the latter two ligands mainly afforded [1L]PF6 at the high temperature described above. The ratios of the 18-electron and 16-electron complexes depended on the Lewis basicity of the donor atoms. The SS ligand produced [2SS]PF6 in 90% yield as a yellow solid. The SN ligand gave a yellow-green solid of [2SN]PF6, containing a small amount of [3SN]PF6. The NN ligand produced [3NN]PF6 as a green solid, which was relatively unstable and readily decomposed in any solutions other than acetonitrile. In acetonitrile, the solvent molecule coordinated to [3NN][PF6] to produce [2NN][PF6]. These results show that the ratio of the 16-electron complex in the product increased in the order of the ligand SS < SN < NN, suggesting that donor atoms with higher Lewis basicity better stabilize the electrondeficient 16-electron species. In the UV−vis spectra of the acetonitrile solutions, the d−d transitions of the yellow 18-electron complexes [2SS]PF6, [2SN]PF6, and [2NN]PF6 were observed at λmax = 370, 376, and 385 nm, respectively. This order is consistent with the spectrochemical series of the donor atoms, suggesting that the ligand field stabilization is most effective for the SS ligand. Transformations between the Chelate and Sandwich Coordination. As shown in the previous section, the NN and SN ligands produced sandwich complexes at high temperatures, whereas they produced the chelate complexes at room temperature. This result indicates that the sandwich complexes are the thermodynamic products and the chelate complexes are the kinetic products. The chelate complexes with the NN and SN ligands also exhibited thermal transformation to the sandwich complexes, of which the former complex reacted faster. [2NN] underwent complete transformation to [1NN]PF6 in acetonitrile-d3 when heated at 60 °C for 12 h. During this reaction, the formation of [CpRu(NCCD3)3]PF6 and free NN ligand was observed initially, followed by an increase in [1NN]PF6, as monitored by 1H NMR. This observation indicates that the transformation occurs via the triacetonitrile complex, which is supported by the absence of this transformation in solvents other than acetonitrile. Similarly, heating the solution of [2SN]PF6 in acetonitrile-d3 produced [1SN]PF6, via the equilibrium of [2SN]PF6 and [CpRu(NCCD3)3]PF6 in a ratio of 4:1. Completion of the reaction required more severe conditions (90 °C, 48 h) than for [2NN]PF6. On the other hand, [2SS]PF6 remained unchanged when heated in acetonitrile at 90 °C for 24 h. These observations show that the efficiency of the thermal transformation to the sandwich complexes decreases in the order [2NN]+ > [2SN]+ ≫ [2SS]+. This tendency is reasonably explained by the effect of the substituents; the softer donor atom (S > N) better stabilizes the 18-electron chelate complexes, whereas the more strongly electron donating substituent (NMe2 > SMe) stabilizes the sandwich complexes. On the basis of the results of these formation and transformation reactions, the relative stability of the complexes was estimated. The stability of the chelate complexes increased in the order [2NN]+ < [2SN]+ < [2SS]+, and the stability of the sandwich complexes has the reverse order, [1NN]+ > [1SN]+ > [1SS]+. The former order is consistent with the tendency of the

RESULTS AND DISCUSSION Ligand Dependence of the Reaction. The reactions of the 1,2-disubstituted benzene ligands (Figure 1) and [CpRu(NCMe)3]+ produced the sandwich complexes or the chelate complexes, depending on the ligands and reaction conditions. The results are summarized in Scheme 1. The OO and SO Scheme 1. Reactions between [CpRu(NCMe)3]X and the 1,2-Disubstituted Benzene Ligandsa

a

X = PF6, Tf2N.

ligands afforded the η6-coordinated sandwich complexes [1L]+. The NN and SN ligands (L) afforded either the sandwich complex ([1L]+) or the chelate complex ([2L]+ and [3L]+) depending on the reaction temperatures. Dissociation of the acetonitrile ligand from [2L]+ produced the 16-electron complex [3L]+. The SS ligand produced only the chelate complex [2SS]+. These reactivities indicate that the coordination ability of the donor atoms increases in the order O < N < S in accordance with the HSAB theory, with the softer donor atoms having a stronger tendency to produce the chelate complexes. The details of each reaction are described below. The reaction of [CpRu(NCMe)3]X (X = PF6, Tf2N) with the OO, SO, NN, and SN ligands in acetonitrile at 90 °C afforded the sandwich complexes [1L]X in 40−90% isolated yield (Scheme 1). The reaction times for the OO, SO, and NN ligands were 6−10 h, but the SN ligand required a much longer time (48 h). The slower reaction for the SN ligand is ascribed to the initial formation of the rather stable chelate complex [2SN]+ (vide inf ra). The products were colorless and stable under air. The PF6 salts were solids, whereas the Tf2N salts were ionic liquids, which were either liquids at room temperature or solids with melting points of about 60 °C. In their 1H NMR spectra, the protons in the arene and Cp rings B

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under reduced pressure produced a dark green solid, which is most likely the 16-electron complex [3SN]PF6. An absorption peak was observed at λmax = 614 nm for this solid, similar to [3NN]PF6 (dark green solid, λmax = 613 nm). In contrast, thermal desorption of acetonitrile from [2SS]PF6 produced an orange solid. The color is different from that of the 16-electron complex, which suggests that the arene ring of an adjacent molecule has coordinated to the vacant coordination site to form an 18-electron-like complex in the solid state, as seen in the dimerization of a 16-electron complex with an acac ligand.17 This seems to be consistent with the observation that only [2SS]+ was obtained from the SS ligand by the reaction with [CpRu(NCMe3)]+, as described above, which in turn indicates that the 16-electron complex [3SS]+ is energetically unfavorable. Thermal Properties. The thermal properties of the sandwich complexes were investigated in detail by means of difference scanning calorimetry (DSC) (Table 1). The PF6 salts

d−d transition energies observed in the UV−vis spectra and also the relative stabilities of [2L]+ and [3L]+ as discussed in the previous section. The latter tendency is further supported by thermogravimetric analysis (vide inf ra). In the case of [1SN]PF6, it was also possible to transform the sandwich complex back to the chelate complex photochemically. Irradiation of a solution of [1SN]PF6 in acetonitrile with UV light generated [2SN]PF6 together with [CpRu(NCMe3)3]PF6 in a ratio of 4:1. In contrast, irradiation of [1NN]PF6 afforded only the triacetonitrile complex, which is probably due to the weaker coordination ability of the ligand. Thermal Stabilities. The thermal stabilities of the PF6 salts were investigated by means of thermogravimetric (TG) analysis. The TG traces for the sandwich complexes [1OO]PF6, [1SO]PF6, [1NN]PF6, and [1SN]PF6 are shown in Figure 2a,

Table 1. Melting Points (Tm), Melting Enthalpies (ΔHm), Melting Entropies (ΔSm), and Glass Transition Temperatures of the Sandwich Complexes ΔHm (kJ mol−1)

ΔSm (J K−1 mol−1)

200 235a 190a 153.1

23.8

55.6

60.8 54.1

18.6 18.8

55.3 57.1

Tm (°C) [1OO]PF6 [1SO]PF6 [1NN]PF6 [1SN]PF6 [1OO]Tf2N [1SO]Tf2N [1NN]Tf2N [1SN]Tf2N a

Tg (°C)

a

−45 −38 −62 −44

Visually observed under a microscope.

exhibited high melting points, which were in the range 153− 235 °C. [1SN]PF6 exhibited the lowest melting point, which may be ascribed to the lower symmetry of the ligand.18 In contrast, the melting points of the Tf2N salts were all below 100 °C, and they are thus regarded as ionic liquids. [1OO]Tf2N and [1SN]Tf2N were liquids at room temperature, which exhibited glass transitions at −45 and −44 °C on cooling, respectively. [1NN]Tf2N and [1SO]Tf2N were solids at room temperature, and their melting points were 54.1 and 60.8 °C, respectively. The melting points are comparable to those of ferrocenium ionic liquids (e.g., [Fe(Cp)(η6-ethylbenzene)]Tf2N: Tm = 40 °C12a). Upon cooling from the melt, [1NN]Tf2N and [1SO]Tf2N exhibited glass transitions at −62 and −38 °C, respectively. The ratios of the glass transition temperature to the melting point (Tg/Tm) for these salts were 0.65 and 0.70, respectively, in agreement with the empirical relationship (Tg/Tm ≈ 2/3).19 In the heating process, the liquid of [1NN]Tf2N exhibited crystallization at −22 °C. [1NN]Tf2N exhibited a phase transition at −58.3 °C (ΔH = 0.90 kJ mol−1, ΔS = 4.2 J mol−1 K−1) in the solid state. The melting points of the chelate complexes could not be evaluated, because [2SS]PF6 and [2NN]PF6 exhibited thermal desorption of acetonitrile before melting, and [3SN]PF6 and [3NN]PF6 were not isolated in pure form. The Tf2N salts with these chelate cations were not prepared. The 16-electron complexes are anticipated to have higher melting points than the sandwich complexes owing to their nonspherical molecular shape. Crystal Structures. The molecular structures of [1NN]PF6, [1SN]PF6, and [2SS]PF6 were determined by X-ray crystallog-

Figure 2. TG traces of (a) [1OO]PF6, [1SO]PF6, [1NN]PF6, and [1SN]PF6 and (b) [2SS]PF6 and [2SN]PF6.

whose decomposition temperatures (−3 wt %) were 232, 220, 232, and 221 °C, respectively. These temperatures reflect the stability of cations, since the anions are much more stable. The decomposition temperature of [1SO]Tf2N (222 °C) was almost the same as that of the PF6 salt. It is known that the electronrich arene ligands stabilize the [CpRu(η6-arene)]+ complexes.15 Consistently, [1NN]PF6 and [1OO]PF6 were more stable than the other salts, which is consistent with the more highly electron donating effect of the substituents (SMe < OMe ≤ NMe2). The TG traces for the acetonitrile-coordinated chelate complexes [2SN]PF6 and [2SS]PF6 are shown in Figure 2b. The weight losses in these salts occurred in two steps. The first step corresponds to the desorption of acetonitrile, which occurred at 130 °C for [2SN]PF6 and 123 °C for [2SS]PF6 (−3 wt %), with almost the same onset temperatures. It has been reported that thermal desorption of acetonitrile occurs in [CpRu(tmeda)(NCMe)]PF6 (tmeda = N,N,N′,N′-tetramethylethylenediamine) to give the 16-electron complex [CpRu(tmeda)]PF6 in the solid state.16 Similarly, desorption of acetonitrile from [2SN]PF6 by heating the compound at 120 °C C

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C6H4(SMe)2 produce chelate complexes ([CpRu(κ2-L)(NCMe)n]+) with different ratios of the 18-electron (n = 1) and 16-electron (n = 0) complexes, depending on the Lewis basicity of the donor atoms. The relative stabilities of each complex were deduced from the reaction conditions and product distributions, which are consistent with the spectroscopic data and thermally determined stabilities. It was also shown that the sandwich complexes with the Tf2N anion are ionic liquids, which are a new series of metallocenium ionic liquids. Based on these results, investigations are under way in our laboratory toward the development of metallocenium ionic liquids that undergo structure transformation by external stimuli.

raphy. They crystallized in the centrosymmetric space groups P21/c, P1̅, and P21/n, respectively. Molecular structures of the cations are shown in Figure 3. The Ru−CCp bond lengths in

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EXPERIMENTAL SECTION

Materials and Physical Measurements. [CpRu(η 6 -1,2dimethoxybenzene)]PF6 ([1OO]PF6),14 [CpRu(η6-benzene)]PF6,3a 1,2-bis(methylthio)benzene,24 1,2-bis(dimethylamino)benzene,25 and 1-dimethylamino-2-(methylthio)benzene25 were prepared according to literature methods. [CpRu(η6-benzene)]Tf2N was synthesized by the metathesis of [CpRu(η6-benzene)]PF6 with LiTf2N in water. Other chemicals were commercially available. 1H NMR spectra were recorded on a JEOL JNM-ECL-400 spectrometer. UV−vis spectra were recorded in acetonitrile or as KBr pellets on a JASCO V-570 UV/ vis/NIR spectrophotometer. Mass spectra were obtained by positive ion electrospray (ES+) using a LTQ Orbitrap Discovery. Elemental analyses were carried out on a Yanaco MT5. DSC measurements were performed using a TA Q100 differential scanning calorimeter from 90 to 430 K at a scan rate of 10 K min−1. TG analyses were performed under a nitrogen atmosphere at a heating rate of 10 K min−1 on a Rigaku TG8120. All reactions were performed under a nitrogen atmosphere. Light irradiation was carried out with a deep UV lamp (250 W) using USHIO SP-9 Spot Cure. [CpRu{η6-1-methoxy-2-(methylthio)benzene}]PF6 ([1SO]PF6). 1-Methoxy-2-(methylthio)benzene (69 mg, 0.45 mmol) was added to an acetonitrile solution (15 mL) of [CpRu(NCMe)3]PF6 (43.4 mg, 0.1 mmol), and the resulting solution was refluxed at 90 °C for 6 h. The resulting pale brown solution was evaporated under reduced pressure. The residue was washed several times with diethyl ether (5 mL) to remove any excess ligand. The resulting solid was dissolved in a small amount of acetonitrile, and addition of diethyl ether (10 mL) to this solution precipitated a white crystalline solid, which was collected and dried in vacuo. Yield: 28.2 mg, 60%. 1H NMR (400 MHz, DMSO-d6, TMS): δ 2.52 (s, 3H, −SCH3), 3.89 (s, 3H, −OCH3), 6.04 (m, 2H, ArH), 6.41, 6.51 (each s, 1H, ArH). Anal. Calcd for C13H15F6OPRuS: C, 33.55; H, 3.25; N, 0.00. Found: C, 33.61; H, 3.22; N, 0.27. [CpRu{η6-1,2-bis(dimethylamino)benzene}]PF6 ([1NN]PF6). This salt was synthesized by the same procedure as [1SO]PF6, using 1,2-bis(dimethylamino)benzene (65.6 mg, 0.4 mmol). White powder: yield 43.3 mg, 91%. 1H NMR (400 MHz, CD3CN, TMS): δ 2.69 (s, 12H, −N(CH3)2), 5.24 (s, 5H, Cp), 5.68 (m, 2H, ArH), 5.87 (m, 2H, ArH). Anal. Calcd for C15H21F6N2PRu: C, 37.90; H, 4.45; N, 5.89. Found: C, 37.90; H, 4.53; N, 6.04. [CpRu{η 6 -1-dimethylamino-2-(methylthio)benzene}]PF 6 ([1SN]PF6). This salt was synthesized by the same procedure as [1SO]PF6, using 1-dimethylamino-2-(methylthio)benzene (74 mg, 0.45 mmol). The product was purified by column chromatography (activated alumina, 2% ethanol in dichloromethane). The product was dissolved in a small amount of dichloromethane, and addition of diethyl ether (10 mL) to this solution precipitated a white crystalline powder, which was collected by filtration and dried under vacuum. Yield: 20.0 mg, 42%. 1H NMR (400 MHz, CD3CN, TMS): δ 2.47 (s, 3H, −SCH3), 2.77 (s, 6H, −N(CH3)2), 5.27 (s, 5H, Cp), 5.86 (m, 2H, ArH), 6.13, 6.16 (each m, 1H, ArH). Anal. Calcd for C14H18F6NPRuS: C, 35.15; H, 3.79; N, 2.93. Found: C, 35.51; H, 3.94; N, 3.01. [CpRu(NCMe)3]Tf2N. A solution of [CpRu(C6H6)]Tf2N (52.4 mg, 0.1 mmol) in acetonitrile (20 mL) was irradiated with UV light for 8 h

Figure 3. Molecular structures of the cations in (a) [1NN]PF6, (b) [1SN]PF6, and (c) [2SS]PF6. Hydrogen atoms have been omitted for clarity.

these salts were about 2.18 Å, which are usual values for CpRu complexes.20 As for the Ru−Carene bonds in [1NN]PF6 and [1SN]PF6, those involving the ipso-carbons (about 2.28 Å) are longer than the others (about 2.19 Å) probably owing to the substituent effect. This distortion causes canting between the Cp ring and the arene ring; the dihedral angle between the rings is 2.2° for [1NN]PF6 and 4.2° for [1SN]PF6. A similar structural feature has been observed in other sandwich complexes.8,21 The average Ru−S distance (2.33 Å) and the Ru−NMeCN distance (2.05 Å) in [2SS]PF6 are comparable to those in other half-sandwich complexes having Ru−S bonds22 and CpRu complexes with an acetonitrile ligand,23 respectively. The two methyl groups in the chelate ligand are oriented away from the CpRu moiety.

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CONCLUSION The reactions of [CpRu(NCMe)3]+ and 1,2-disubstituted benzene ligands (1-X1-2-X2-C6H4, where X1, X2 = SMe, OMe, NMe2) were investigated, and the following tendencies were observed. First, the ligands with hard donor atoms give the sandwich complexes [CpRu(η6-L)]+, and the ligands with softer donor atoms give the chelate complexes ([CpRu(κ2-L)(NCMe)n]+; n = 0 or 1). Second, 1,2-C6H4(NMe2)2 and 1,2C6H4(NMe2)(SMe) afford both the chelate complexes and sandwich complexes. The former complexes are the kinetic products and thermally transform into the latter thermodynamic products. The softer donor atoms stabilize the 18electron chelate complexes, whereas the better electron donating substituents stabilize the sandwich complexes. Third, 1,2-C 6 H 4 (NMe 2 ) 2 , 1,2-C 6 H 4 (NMe 2 )(SMe), and 1,2D

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that 1,2-bis(dimethylamino)benzene (65.6 mg, 0.4 mmol) was used and the mixture was stirred for 2 days. A green powder was obtained, which was a 3:1 mixture of [1NN]PF6 and [3NN]PF6, which could not be separated. In the 1H NMR spectrum of this product in CD3CN, only [2NN]PF6 was observed due to the coordination of the solvent. 1 H NMR (400 MHz, CD3CN, TMS) [2NN]PF6: δ 3.37 (bs, 5.5H, −N(CH3)2), 3.40 (s, 1H, −N(CH3)2), 3.46 (bs, 5.5H, −N(CH3)2), 4.07 (s, 5H, Cp), 7.30 (m, 2H, ArH); 7.43 (m, 2H, ArH). Anal. Calcd for C15H21N2F6PRu: C, 37.90; H, 4.45; N, 5.89. Found: C, 37.45; H, 4.36; N, 7.02. UV−vis (CH3CN) λmax nm (ε/M−1 cm−1): 385 (1182). [3NN]PF6 was relatively unstable and decomposed to give a black powder in solutions other than acetonitrile such as dichloromethane or acetone. Coordination Transformation in Solutions. The thermal and photochemical conversions of the complexes were investigated in solution and monitored by measuring the 1H NMR spectra. A solution of [2SN]PF6 (4 mg) in CD3CN (0.7 mL) was heated at 90 °C in an NMR tube. The color of the solution changed from yellow to colorless in 48 h, by which time the complex had completely transformed to [1SN]PF6. Similarly, heating the yellow solution of [2NN]PF6, which was generated by dissolving a green powder of [3NN]PF6 (4 mg) in CD3CN, at 60 °C for 12 h led to complete conversion to a colorless solution of [1NN]PF6. No such transformation occurred in solvents other than acetonitrile; the reactions in 1,2-dichloroethane and THF gave only unidentifiable products. Photochemical conversion of [1SN]PF6 (4 mg) was carried out by UV irradiation for 4 h of a solution in CD3CN (0.7 mL). The color of the solution changed from colorless to yellow, when the [1SN]PF6 had disappeared and a 4:1 mixture of [2SN]+ and [CpRu(NCMe)3]+ was produced. X-ray Crystallography. Single crystals of [1NN]PF6 and [1SN]PF6 suitable for X-ray crystal structure analysis were grown by slow diffusion of diethyl ether into concentrated dichloromethane solutions. Single crystals of [2SS][PF6] were obtained by slow evaporation of an acetonitrile solution. X-ray diffraction data were collected on a Bruker APEX II ultra CCD diffractometer using Mo Kα radiation (λ = 0.71073 Å). Crystallographic parameters for these compounds are listed in Table S1 (Supporting Information). The data were corrected for absorption with SADABS.26 All calculations were performed using SHELXL.27 The structure was solved by direct methods (SHELXS 97) and expanded using Fourier techniques. All non-hydrogen atoms were refined anisotropically. Empirical absorption corrections were applied. The hydrogen atoms were inserted at calculated positions and allowed to ride on their respective parent atoms. ORTEP-328 was used to produce molecular graphics. CCDC nos. 900337 ([1NN]PF6), 900338 ([1SN]PF6), and 900339 ([2SS]PF6) contain the supplementary crystallographic data for this paper. Structure analysis of [1SO]PF6 was also performed, but the result was unsatisfactory due to the presence of superlattice reflections, which likely originated from an incommensurate arrangement of the anions. In a tentative analysis ignoring the superlattice reflections, the cation was found by the direct methods but no further refinement was possible.

under stirring, during which the solution changed from colorless to yellow. The solution was used for the next step without isolation. [CpRu{η6-1,2-bis(methoxy)benzene}]Tf2N ([1OO]Tf2N). 1,2-Bis(methoxy)benzene (62 mg, 0.45 mmol) was added to a solution of [CpRu(NCMe)3]Tf2N (56.9 mg 0.1 mmol) in acetonitrile (15 mL), and the solution was heated to reflux at 90 °C for 6 h. The resulting pale brown solution was evaporated under reduced pressure, and the residue was washed with diethyl ether before purification by column chromatography (activated alumina, 2% ethanol in dichloromethane). The product was dried under vacuum at 75 °C for 12 h. Colorless liquid: yield 42.3 mg, 72%. 1H NMR (400 MHz, CDCl3, TMS): δ 3.89 (s, 6H, −OCH3), 5.33 (s, 5H, Cp), 5.88 (m, 2H, ArH), 6.29 (m, 2H, ArH). Anal. Calcd for C15H15F6NO6RuS2: C, 30.82; H, 2.59; N, 2.40. Found: C, 31.12; H, 2.46; N, 2.58. [CpRu{η6-1-methoxy-2-(methylthio)benzene}]Tf2N ([1SO] Tf2N). This salt was synthesized by the same procedure as [1OO]Tf2N, using 1-methoxy-2-(methylthio)benzene (69 mg, 0.45 mmol). The product was purified by column chromatography (activated alumina, 2% EtOH in dichloromethane) and dried at 75 °C in vacuo. White solid, yield 31.3 mg, 52%. Mp: 60.8 °C. 1H NMR (400 MHz, acetoned6, TMS): δ 2.60 (s, 3H, −SCH3), 4.02 (s, 3H, −OCH3), 5.48 (s, 5H, Cp), 6.11 (t, J = 5.6 Hz, 1H, ArH), 6.17 (t, J = 5.6 Hz, 1H, ArH), 6.52 (d, J = 4.8 Hz, 1H, ArH), 6.58 (d, J = 5.6 Hz, 1H, ArH). Anal. Calcd for C15H15F6NO5RuS3: C, 30.00; H, 2.52; N, 2.33. Found: C, 30.42; H, 2.47; N, 2.51. [CpRu{η6-1,2-bis(dimethylamino)benzene}]Tf2N ([1NN]Tf2N). This salt was synthesized by the same procedure as [1OO]Tf2N, using 1,2-bis(dimethylamino)benzene (65.6 mg, 0.4 mmol). The product was purified by column chromatography (activated alumina, 2% EtOH in dichloromethane). A colorless liquid was obtained, which crystallized when stored at 0 °C. Yield: 41.8 mg, 68%. Mp: 53.7 °C. 1H NMR (400 MHz, acetone-d6, TMS): δ 2.80 (s, 12H, −N(CH3)2), 5.44 (s, 5H, Cp), 5.93 (m, 2H, ArH), 6.13 (m, 2H, ArH). Anal. Calcd for C17H21F6N3O4RuS2: C, 33.44; H, 3.47; N, 6.88. Found: C, 33.89; H, 3.62; N, 6.87. [CpRu{η 6 -1-dimethylamino-2-(methylthio)benzene}]Tf 2 N ([1SN]Tf2N). This salt was synthesized by the same procedure as [1OO]Tf2N, using 1-dimethylamino-2-(methylthio)benzene (74 mg, 0.45 mmol). The product was purified by column chromatography (activated alumina, 2% ethanol in dichloromethane). Colorless liquid: yield 25.1 mg, 41%. 1H NMR (400 MHz, CD3CN, TMS): δ 2.44 (s, 3H, −SCH3), 2.74 (s, 6H, −N(CH3)2), 5.24 (s, 5H, Cp), 5.86 (s, 2H, ArH), 6.12 (m, 2H, ArH). Anal. Calcd for C16H18F6N2O4RuS3: C, 31.32; H, 2.96; N, 4.57. Found: C, 31.73; H, 2.92; N, 4.68. [CpRu{κ2-1,2-bis(methylthio)benzene}(NCMe)]PF6 ([2SS]PF6). 1,2-Bis(methylthio)benzene (20 mg, 0.12 mmol) was added to a suspension of [CpRu(NCMe)3]PF6 (43.4 mg, 0.1 mmol) in diethyl ether (15 mL), and the mixture was stirred for 4 h. The resulting yellow powder was filtered off, washed several times with diethyl ether (5 mL), and dried in vacuo. Yield: 46.2 mg, 89%. 1H NMR (400 MHz, acetone-d6, TMS): δ 2.48 (s, 3H, NCCH3), 2.82 (s, 6H, −SCH3), 4.87 (s, 5H, Cp), 7.59 (m, 2H, ArH), 8.08 (m, 2H, ArH). Anal. Calcd for C15H18NF6PRuS2: C, 34.48; H, 3.47; N, 2.68. Found: C, 34.49; H, 3.58; N, 2.74. UV−vis (CH3CN) λmax nm (ε/M−1 cm−1): 370 (1345). [CpRu{κ2-1-dimethylamino-2-(methylthio)benzene}(NCMe)]PF6 ([2SN]PF6). This salt was synthesized by the same procedure as [2SS]PF6, using 1-dimethylamino-2-(methylthio)benzene (20 mg, 0.12 mmol). A yellow-green powder of [2SN]PF6 containing a small amount of [3SN]PF6 was obtained. In the UV−vis spectrum of the solid, a strong absorption peak of [2SN]PF6 was observed at λmax = 387 nm together with a very weak absorption peak of [3SN]PF6 at 614 nm. Yield: 42.1 mg, 83%. In the 1H NMR spectrum in CD3CN, only the peaks of [2SN]PF6 were observed owing to the coordination of the solvent to [3SN]PF6. 1H NMR (400 MHz, CD3CN, TMS): δ 2.75 (bs, 3H, −N(CH3)2), 3.18 (bs, 3H, −N(CH3)2), 3.45 (s, 3H −SCH3), 4.39 (s, 5H, Cp), 7.31, 7.42, 7.51, 7.62 (each m, 1H, ArH). Anal. Calcd for C16H21N2F6PRuS: C, 37.00; H, 4.07; N, 5.39. Found: C, 36.20; H, 4.02; N, 5.22. UV−vis (CH3CN) λmax nm (ε/M−1 cm−1): 376 (1004). [CpRu{κ2-1,2-bis(dimethylamino)benzene}]PF6 ([3NN]PF6). This salt was synthesized by the same procedure as [2SS]PF6, except

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ASSOCIATED CONTENT

S Supporting Information *

Crystallographic parameters for [1NN]PF6, [1SN]PF6, and [2SS]PF6 (Table S1). CIF files for [1NN]PF6, [1SN]PF6, and [2SS]PF6. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Fax: +81-78-803-5679. E-mail: [email protected]. jp. Notes

The authors declare no competing financial interest. E

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ACKNOWLEDGMENTS We thank Y. Funasako (Kobe University) for help with the Xray crystallography, Dr. Y. Furuie (Kobe University) for elemental analysis, and M. Nakama (Crayonsoft Inc.) for providing a Web-DB system. This work was financially supported by Kakenhi (No. 24350073) from JSPS.

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dx.doi.org/10.1021/om301073z | Organometallics XXXX, XXX, XXX−XXX