Selective Hydrogenation of Ruthenium Acylphosphine Complexes

Article pubs.acs.org/Organometallics

Selective Hydrogenation of Ruthenium Acylphosphine Complexes Saravanan Gowrisankar,† Helfried Neumann, Anke Spannenberg, and Matthias Beller* Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Strasse 29a, 18059 Rostock, Germany S Supporting Information *

ABSTRACT: Hydrogenation of a benzene ruthenium chloride dimer in the presence of novel acylphosphine (phosphomide) ligands resulted in the formation of corresponding ruthenium(II)−benzyl phosphine complexes. Here, selective reduction of the carbonyl group to a methylene unit takes place with molecular hydrogen under mild conditions in good yield. This approach provides an alternative synthesis of ruthenium phosphine complexes of benzyl and heterobenzyl phosphine ligands.

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INTRODUCTION Phosphorus-based ligands have been proven to be essential in homogeneous catalysis and organometallic chemistry. In contrast to the usually applied aryl and alkyl phosphines, acylphosphines (phosphomides) are an under-represented class of compounds, which are rarely used in catalysis.1 In general, acylphosphines are believed to be unstable and difficult to handle. Nevertheless, in 1952, the first synthesis of an acetyl phosphine was described starting from acetyl bromide and diethyl phosphine.2 Still today, most of the known acylphosphines are synthesized by condensation of acid chlorides with the respective secondary phosphine in the presence of a base such as NEt3 or K2CO3 in an inert solvent.3 Alternatively, highly reactive silyl phosphines can be used for the synthesis of cyclic carboxylic monophosphines or difunctional acylphosphines based on dicarboxylic acids.4 In agreement with the rare catalytic investigations, the preparation and basic organometallic chemistry of acylphosphine transition-metal complexes has also been largely neglected. In fact, only four examples of such complexes have been explored in more detail. The synthesis of acylphosphine molybdenum5 and iron6 complexes relies on a controllable migration of acyl groups from metal to phosphine ligands. A more straightforward synthesis was developed by Clarke et al., who showed that aroyl phosphines form stable complexes by combination with [Cp*RhCl2]2. The resulting rhodium phosphomide complexes were applied in the hydroformylation of 1-hexene.7 Recently, Stambuli et al. synthesized acylphosphine-ligated iridium complexes using [Cp*IrCl2]2 as precursor.8 Interestingly, the latter group demonstrated that an alkyl group of the acylphosphine ligand coordinated to the iridium center is dehydrogenated in the β−γ position to an olefin (Scheme 1). For some time, we were attracted to the development of improved catalysts for hydrogenation of carbon dioxide to formic acid derivatives, which is of interest for novel hydrogen storage systems.9 In this respect, very recently, we succeeded generating active catalysts for the hydrogenation of sodium bicarbonate by a combination of phosphomides with commercially available ruthenium precursors.1 On the basis of © 2013 American Chemical Society

Scheme 1. Reactivity of Ir− and Ru−Acylphosphine Complexes

this work, we decided to prepare ruthenium complexes with acylphosphine ligands and examined their behavior in the presence of hydrogen. In this paper, we show for the first time unexpected hydrogenations of well-defined ruthenium(II)arene−acylphosphine complexes, which were synthesized straightforward from acylphosphine ligands and the [RuCl2(η6-C6H6)]2 dimer.

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RESULTS AND DISCUSSION At the start of this work, 1-naphthoylchloride was reacted with dicyclohexyl phosphine in the presence of triethylamine, which led immediately to a bright orange solution of dicyclohexyl 1naphthoyl phosphine L1.10 Likewise, other acylphosphine ligands such as (dicyclohexyl phosphino)(furan-2-yl)Received: August 12, 2013 Published: December 9, 2013 94

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Organometallics

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Table 1. Different Hydrogenation Experiments of Ruthenium Dimer with Phosphomide Ligand (L1)

yield (%)a,b entry

temp (°C)

1 2c 3d 4 5e 6e 7 8

50 50 RT RT 40 40 50 80

H2 (bar)

time (h)

1a

2a

60 10 60 60 60

5 5 24 3 1.5 1.5 5 12

86 85 58 66 90 10 0 0

0 0 0 0 10 90 80f 0

a

Reaction conditions: 0.05 mmol [RuCl2(η6-C6H6)]2, 0.1 mmol ligand (L1), 2 mL of MeOH. bIsolated yield. cCHCl3 was used as solvent. dLigand L1 (0.2 mmol). eRatio of 1a and 2a was determined by 31P NMR. fPrecipitation (55%) as a red solid and from the reaction mixture 25% are obtained.

Under the optimized reaction conditions (MeOH at 60 bar of H2 at 50 °C using 0.5 equiv of [RuCl2(η6-C6H6)]2 and 1.0 equiv of the ligand), we examined the reaction of related ligands (dicyclohexyl phosphino)(furan-2-yl)methanone (L2) and (dicyclohexyl phosphino)(thiophen-2-yl)methanone (L3) and ruthenium benzene dimer. Again, the conversion of both ligands L2 and L3 proceeded with complete reduction (99%) of the acyl group giving 54 and 60% yield of corresponding complexes 2b and 2c, as shown in Scheme 2.

methanone (L2), (dicyclohexyl phosphino)(thiophen-2-yl)methanone (L3), and dicyclohexyl benzoyl phosphine (L4) were successfully prepared starting from 2-furoyl chloride, 2thiophenecarbonyl chloride, and benzoyl chloride, respectively. Notably, all of these acylphosphine ligands are stable to air and moisture. Surprisingly, ligand L1 was even stable in water (D2O) for several days (see Supporting Information). Next, the acylphosphine ligands L1−L3 were allowed to react in methanol at ambient temperature with the ruthenium complexes Ru(Me-allyl)2(COD) and [RuCl2(COD)]n. We expected that the COD (cis,cis-cycloocta-1,5-diene) group would be rapidly displaced by the dicyclohexyl 1-naphthoyl phosphine ligand under this condition. However, both Ru(Meallyl)2(COD) and [RuCl2(COD)]n precursors gave only a mixture of products, which was difficult to purify. In contrast, the reaction of the ruthenium dimer [RuCl2(η6-C6H6)]2 with L1 gave the well-defined complex 1a [RuCl2(η6-C6H6)(Cy2P(1-naphthoyl))] in methanol as well in chloroform at 50 °C (Table 1, entries 1 and 2). Carrying out the reaction with 4 equiv of the ligand (L1) gave the same product (Table 1, entry 3). Then, we started carrying out a set of hydrogenation experiments to study the behavior of complex 1a and acylphosphine ligand L1 under this condition. Obviously, a ruthenium hydride complex was expected to be formed by hydrogenolysis since a large number of ruthenium complexes are known to activate molecular hydrogen. Instead, to our surprise, we obtained a mixture of 1a and the reduced complex 2a [RuCl2(η6-C6H6)(Cy2P(1-methylnaphthyl))] under 10 bar H2 at 40 °C after 5 h (Table 1, entry 5). Apparently, the carbonyl group of the ligand L1 in complex 1a is partially reduced to a methylene unit. To improve the yield of 2a, we increased the pressure to 60 bar of hydrogen, and the ratio of 1a/2a was increased to 10:90. Full conversion toward 2a was observed at 50 °C and 60 bar of hydrogen, yielding 80% of 2a. Increasing the reaction temperature further from 50 to 80 °C and increasing the time to 12 h gave only decomposition products (Table 1, entries 6−8). To the best of our knowledge, such hydrogenation of acylphosphine ligands is not known yet.

Scheme 2. Synthesis of Ruthenium Benzyl-Type Phosphine Complexesa

a

Reaction conditions: [RuCl2(η6-C6H6)]2 (0.5 equiv), ligand (L1−L3) (1.0 equiv), 2 mL of MeOH, 60 bar H2, 50 °C, 5 h. Isolated yield.

It should be noted that this hydrogenation constitutes a convenient way to synthesize benzyl-type phosphine ruthenium complexes starting from easily accessible aroyl phosphine complexes since the synthesis of free benzyl-type ligands is often tedious. For example, in the case of 1-methylnaphthyl dicyclohexyl phosphine, which is not described in the literature, we were able to obtain the borane adduct, but the release of the free ligand with morpholine failed.11 Notably, the binding of the phosphine ligand in complex 2a should be stronger compared to the binding of the acylphosphine in 1a. Indeed, a 31 P NMR experiment with equimolar amounts of 2a and ligand L1 in CDCl3 showed no formation of 1a, indicating that no ligand exchange occurred. 95

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time nor increasing the temperature from 50 to 80 °C gave rise to the formation of complex 6. Also, other experiments starting from 3 and 4 failed to give complex 6. The unusual complex 4 was characterized by 1H, 13C, and 31P NMR, and high-resolution mass spectroscopy (HRMS) as well as X-ray crystal structure analysis (Figure 2). Again, we

The structure of complex 2a was confirmed by X-ray analysis and was additionally characterized by 1H, 13C, 31P NMR, and high-resolution mass spectroscopy. More specifically, the 1H NMR spectra show a doublet at 3.98 (d, J = 10.7 Hz, 2H), which can be assigned to the CH2 protons of the alkyl moiety. The 31P NMR shifts of 2a and 1a at 39.01 and 48.07 ppm, respectively, show the expected downfield shift, while 28.79 ppm was observed in the case of the free ligand L1. The molecular structure of 2a shows the piano-stool geometry at the ruthenium center, which is coordinated by a benzene molecule, two chlorine atoms, and the benzyl phosphine ligand (Figure 1).

Figure 2. Molecular structure of complex 4. The thermal ellipsoids correspond to 30% probability. Hydrogen atoms (except H2 and H26) are omitted for clarity.

observed piano-stool geometry at the ruthenium center. In the solid state, the phosphine ligand in 4 coordinates only via the phosphorus atom to the ruthenium center, and no additional coordination via oxygen is observed. The NMR spectrum of complex 4 mixed with D2O confirmed the existence of the free OH group by diminishing the signal at 4.5 ppm. To the best of our knowledge, no example of such ruthenium complex has been reported.12 In conclusion, we describe the synthesis of ruthenium complexes 2a−c, 3, and 4 with benzyl-type phosphine ligands from air-stable acylphosphine ligands L1−L4. These ligands can be easily obtained from the reaction of acid chlorides and dialkyl phosphine in good yields. The formation of the novel

Figure 1. Molecular structure of complex 2a. The thermal ellipsoids correspond to 30% probability. Hydrogen atoms are omitted for clarity.

Using dicyclohexyl benzoyl phosphine (L4) in this hydrogenation reaction, an interesting difference of reactivity was observed giving insight into the detailed pathway of the reaction. Unpredictably, the addition of dicyclohexyl benzoyl phosphine (L4) to the ruthenium dimer followed by hydrogenation resulted in the formation of the dicyclohexylphosphino-1-hydroxybenzyl ruthenium complex 4 and not the expected complex 6 (Scheme 3). Neither a longer reaction Scheme 3. Reactions of Ligand L4 and Complex 3

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1H, CH), 7.35−7.30 (m, 1H, CH), 6.50−6.44 (m, 1H, CH), 2.09−1.92 (m, 2H, Cy), 1.82−1.52 (m, 10H, Cy), 1.34−0.97 (m, 10H, Cy). 13C NMR (75 MHz, CDCl3): δ 202.3, 201.8, 156.4, 155.8, 146.7, 119.5, 119.4, 111.9, 32.1, 31.9, 30.3, 30.1, 29.7, 29.5, 27.2, 27.0, 26.9, 26..8, 26.1. 31P NMR (121 MHz, CDCl3): δ 18.9. IR (neat, cm−1): 2920, 2848, 1615, 1446, 1253, 1025, 787. MS (EI): 292 (56) [M]+, 95 (100), 128 (44), 197 (33), 209 (47). HRMS calcd for C17H26O2P (M + H)+ 293.16649; found 293.16662. Anal. Calcd for C17H25O2P: C, 69.84; H, 8.62; P, 10.59. Found: C, 70.04; H, 8.78; P, 10.66. (Dicyclohexylphosphino)(thiophen-2-yl)methanone (L3). Following the procedure for the preparation of L1, the reaction of thiophene-2-carbonyl chloride (1g, 6.8 mmol), dicyclohexyl phosphine (1.21 g, 6.08 mmol), and triethylamine (0.81 g, 8.0 mmol) in THF (10 mL) gave 1.78 g (85%) of a yellow solid. Purification of the crude product is analogous to L1. 1H NMR (300 MHz, CDCl3): δ 7.97− 7.91 (m, 1H, thiophenyl), 7.65−7.59 (m, 1H, thiophenyl), 7.13−7.10 (m, 1H, thiophenyl), 2.09−1.94 (m, 2H, Cy), 1.85−1.53 (m, 10H, Cy), 1.32−0.98 (m, 10H, Cy). 13C NMR (75 MHz, CDCl3): δ 206.8, 206.2, 149.6, 149.1, 133.9, 133.9, 127.9, 32.4, 32.2, 30.3, 30.2, 29.7, 29.6, 27.2, 27.1, 27.0, 26.9, 26.1. 31P NMR (121 MHz, CDCl3): δ 19.7. IR (neat, cm−1): 2924, 2847, 1607, 1404, 800, 742. MS (EI): 308 (47) [M]+, 111 (100), 197 (25), 225 (27). HRMS calcd for C17H26OPS (M + H)+ 309.14365; found 309.14381. Anal. Calcd for C17H25OPS: C, 66.20; H, 8.17; P, 10.04; S, 10.40. Found: C, 66.24; H, 8.23; P, 10.01; S, 10.45. Dicyclohexyl Benzoyl Phosphine (L4). Following the procedure for the preparation of L1, the reaction of benzoyl chloride (1g, 7.14 mmol), dicyclohexyl phosphine (1.47 g, 7.14 mmol), and triethylamine (0.87 g, 8.57 mmol) in THF (10 mL) gave 1.55 g (72%) of a yellow solid. Purification of the crude product is analogous to L1. 1H NMR (300 MHz, CDCl3): δ 8.04−7.96 (m, 2H, Ph), 7.59−7.50 (m, 1H, Ph), 7.49−7.39 (m, 2H, Ph), 2.09−1.93 (m, 2H, Cy), 1.85−1.55 (m, 10H, Cy), 1.36−0.98 (m, 10H, Cy). 13C NMR (75 MHz, CDCl3): δ 218.0, 217.4, 142.2, 141.7, 133.1, 128.4, 128.1, 128.0, 32.3, 32.1, 30.8, 30.6, 29.7, 29.5, 27.4, 27.2, 27.1, 27.0, 26.2. 31P NMR (121 MHz, CDCl3): δ 19.3. IR (neat, cm−1): 2917, 2849, 1633, 1445, 1209, 1167, 777, 692. MS (EI): 302 (100) [M]+, 197 (35), 219 (23). HRMS calcd for C19H28OP (M + H)+ 303.18723; found 303.18770. Anal. Calcd for C19H27OP: C, 75.47; H, 9.00; P, 10.24. Found: C, 75.35; H, 9.02; P, 10.22. Synthesis of [RuCl2(η6-C6H6)(Cy2P(1-naphthoyl))] 1a. To a Schlenk tube containing [RuCl2(η6-C6H6)]2 (50 mg, 0.10 mmol) and Cy2P(1-naphthoyl) (77 mg, 0.22 mol) was added MeOH (3 mL). The resulting solution was stirred for 5−6 h at 50 °C under argon, and then the solvent was removed. After washing the crude material three times with heptane and drying in vacuum, the desired product was obtained as an orange powder (108 mg, 89%). 1H NMR (300 MHz, CDCl3): δ 8.54 (d, J = 7.7 Hz, 1H, naphthyl), 8.63 (d, J = 8.1 Hz, 1H, naphthyl), 8.05 (d, J = 8.1 Hz, 1H, naphthyl), 7.93 (d, J = 7.7 Hz, 1H, naphthyl), 7.74−7.50 (m, 3H, naphthyl), 5.55 (s, 6H, benzene), 2.74 (br s, 2H, Cy), 2.39 (br s, 2H, Cy), 1.86−0.89 (m, 18H, Cy). 13C NMR (75 MHz, CDCl3): δ 215.5, 215.4, 134.4, 134.2, 130.0, 129.0, 128.8, 126.9, 124.8, 124.5, 88.8, 88.7, 35.4, 35.2, 31.1, 31.0, 29.7, 28.2, 28.1, 27.2, 27.0, 26.0. 31P NMR (121 MHz, CDCl3): δ 48.0. IR (neat, cm−1) ν(CO): 2923 cm−1. HRMS calcd for C29H35Cl2OPRuNa (M + Na)+ 625.07403; found 625.07453. Anal. Calcd for C29H35Cl2OPRu: C, 57.81; H, 5.85; P, 5.14. Found: C, 57.61; H, 5.79; P, 5.22. Synthesis of [RuCl2(η6-C6H6)(Cy2P(1-methylnaphthyl))] 2a. A mixture of [RuCl2(η6-C6H6)]2 (25 mg, 0.05 mmol, 1.0 equiv) and dicyclohexyl 1-naphthoyl phosphine (L1) (35.2 mg, 0.1 mmol, 2.0 equiv) was given in a 12 mL vial equipped with a stirring bar, septum, and needle. After flashing with argon, 2 mL of MeOH was added, and the vial was placed in an alloy plate, which was transferred to a 300 mL autoclave of the 4560 series from Parr Instruments under argon atmosphere. The autoclave was then filled with 60 bar H2 at room temperature. The reaction mixture was stirred (400 rpm) for 5 h at 50 °C. Next, the autoclave was cooled with ice water, and the pressure was slowly released. The cold reaction solution was dark and contained a red brown residue. The solution over the solid was carefully decanted, and the solid was washed three times with 1−2 mL of

complexes proceeds via regioselective CO hydrogenation of the acylphosphine ligand.

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EXPERIMENTAL SECTION

General Considerations. All reactions were performed under argon by using standard Schlenk techniques. All solids were weighed in air. Dicyclohexyl phosphine and Et3N were purchased from SigmaAldrich and used as received. Acid chlorides were purchased from Strem and Sigma-Aldrich. [RuCl2(η6-C6H6)]2 complex was commercially available from Sigma-Aldrich. All other reagents were purchased from common suppliers and used without further purification. Heptane and methanol were distilled in an argon atmosphere over lithium hydride and magnesium turnings, respectively. Chloroform was distilled over P2O5. Analytical Methods. NMR data were recorded on Bruker ARX 300 and Bruker ARX 400 spectrometers. 13C and 1H NMR spectra were referenced to signals of deutero solvents and residual protonated solvents, respectively. 31P NMR chemical shifts are reported relative to 85% H3PO4. Gas chromatography analysis was performed on an Agilent HP-5890 instrument with a FID detector and HP-5 capillary column (polydimethylsiloxane with 5% phenyl groups, 30 m, 0.32 mm i.d., 0.25 μm film thickness) using argon as carrier gas. Gas chromatography−mass analysis was carried out on a Agilent HP5890 instrument with an Agilent HP-5973 mass selective detector (EI) and HP-5 capillary column (polydimethylsiloxane with 5% phenyl groups, 30 m, 0.25 mm i.d., 0.25 μm film thickness) using helium carrier gas. ESI HR-MS measurements were performed on an Agilent 1969A TOF mass spectrometer. The combustion analysis data for P were collected using the UV/vis spectrometer Lamda 2 (PerkinElmer), while the combustion data for C/H/S were obtained from a C/H/N/S Mikroanalysator−TruSpec CHNS Micro (Leco). Suitable samples for correct elementary analysis of all ruthenium complexes were obtained by washing the crude product several times with methanol and subsequently drying the material in high vacuum. Diffraction data were collected on a Bruker Kappa APEX II Duo diffractometer using graphite monochromated Mo Kα radiation. The structures were solved by direct methods and refined by full-matrix least-squares procedures on F2 with the SHELXTL software package.13 XP (Bruker AXS) was used for graphical representations. Dicyclohexyl 1-Naphthoyl Phosphine (L1). At room temperature, 1-naphthoyl chloride (1g, 5.26 mmol) was added dropwise over a period of 20 min to a solution of dicyclohexyl phosphine (1.04 g, 5.26 mmol) and triethylamine (0.64 g, 6.31 mmol) in THF (10 mL), and the resulting mixture was stirred for 5 h. Next, the mixture was quenched with H2O (10 mL), and the product was extracted with CH2Cl2 (2 × 50 mL). The combined CH2Cl2 extracts were washed with water (20 mL), dried over Na2SO4, and evaporated to give L1 as a yellow solid (1.45 g, 78%). For purification, the crude product was dissolved in a mixture of 1 mL of chloroform and 8 mL of methanol and was kept overnight in the refrigerator (+8 °C). After being washed with heptane, the title compound was obtained as an analytically pure yellow solid. 1H NMR (300 MHz, CDCl3): δ 8.57 (d, J = 7.9 Hz, 1H, arom), 8.37−8.30 (m, 1H, arom), 7.98 (d, J = 8.6 Hz, 1H, arom), 7.88 (d, J = 8.0 Hz, 1H, arom), 7.63−7.46 (m, 3H, arom), 2.13−1.98 (m, 2H, Cy), 1.96−1.53 (m, 10H, Cy), 1.36−0.93 (m, 10H, Cy). 13C NMR (75 MHz, CDCl3): δ 222.1, 221.6, 139.8, 139.4, 134.0, 134.0, 132.8, 130.5, 130.2, 128.9, 128.9, 128.3, 127.9, 126.4, 125.4, 124.2, 33.0, 32.8, 31.1, 31.0, 29.7, 29.6, 27.4, 27.3, 27.2, 27.1, 26.2. 31P NMR (121 MHz, CDCl3): δ 28.8. IR (neat, cm−1): 2924, 2850, 1627, 1447, 1234, 1133, 779, 495. MS (EI): 352 (14) [M]+, 155 (100), 156 (13). HRMS calcd for C23H30OP (M + H)+ 353.20288; found 353.20213. Anal. Calcd for C23H29OP: C, 78.38; H, 8.29; P, 8.79. Found: C, 78.62; H, 8.10; P, 8.80. (Dicyclohexylphosphino)(furan-2-yl)methanone (L2). Following the procedure for the preparation of L1, the reaction of furan-2carbonyl chloride (1g, 7.66 mmol), dicyclohexyl phosphine (1.37 g, 6.92 mmol), and triethylamine (1.28 g, 9.0 mmol) in THF (10 mL) gave 1.789 g (84%) of a yellow solid. Purification of the crude product is analogous to L1. 1H NMR (300 MHz, CDCl3): δ 7.59−7.55 (m, 97

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Organometallics

Article

Calcd for C25H33Cl2OPRu: C, 54.35; H, 6.02; P, 5.61. Found: C, 54.48; H, 6.12; P, 5.68. Synthesis of [RuCl2(η6-C6H6)(Cy2P(phenyl)methanol)] 4. Following the procedure for the preparation of 2a, the reaction of [RuCl2(η6-C6H6)]2 (25 mg, 0.05 mmol, 1 equiv) and dicyclohexyl benzoyl phosphine (L4) (30.3 mg, 0.1 mmol, 2.0 equiv) gave 23 mg (42%) of a ocher solid. Recrystallization from CHCl3/heptane gave red crystals suitable for X-ray analysis. 1H NMR (400 MHz, CDCl3): δ 7.39−7.31 (m, 2H, Ph), 7.31−7.21 (m, 3H, Ph), 5.95−5.88 (s, 1H, CH), 5.65 (s, 6H, benzene), 4.40 (s, 1H, OH), 2.41−2.22 (m, 2H, Cy), 1.96−1.43 (m, 12H, Cy), 1.42−0.87 (m, 8H, Cy). 13C NMR (100 MHz, CDCl3): δ 128.2, 128.2, 128.1, 128.0, 128.0, 127.9, 87.2, 87.1, 73.1, 72.8, 38.3, 38.1, 37.4, 37.3, 31.9, 30.4, 30.3, 29.7, 28.8, 27.8, 27.7, 27.7, 27.6, 27.2, 27.1, 26.5, 26.3. 31P NMR (121 MHz, CDCl3): δ 37.6. HRMS (ESI) m/z+ calcd for C25H35ClOPRu (M − Cl)+ 521.11528; found 521.11566. Anal. Calcd for C25H35Cl2OPRu: C, 54.15; H, 6.36; P, 5.59. Found: C, 54.04; H, 6.45; P, 5.52. Crystal Data for 4: C26.5H36.5Cl6.5OPRu, M = 733.52, triclinic, space group P1̅, a = 14.6405(5) Å, b = 15.2404(5) Å, c = 16.8663(6) Å, α = 94.309(2)°, β = 97.282(2)°, γ = 115.195(2)°, V = 3342.7(2) Å3, T = 150(2) K, Z = 4, 75 677 reflections measured, 15 344 independent reflections (Rint = 0.0461), final R values (I > 2σ(I)): R1 = 0.0533, wR2 = 0.1381, final R values (all data): R1 = 0.0679, wR2 = 0.1474, 606 parameters. The asymmetric unit of compound 4 contains two complex molecules (only one of them is depicted in Figure 2) and three solvent molecules (CHCl3). Contributions of further disordered solvents were removed from the diffraction data with PLATON/ SQUEEZE [Spek, A. L. Acta Crystallogr. 2009, D65, 148−155]. Synthesis of 5. The D2O experiment was carried out in an NMR tube by adding 0.2 mL of D2O to 4 dissolved in CDCl3. The crude product was analyzed by 1H NMR (300 MHz, CDCl3): δ 7.41−7.22 (m, 5H), 5.97 (d, J = 6.3 Hz, 1H), 5.72 (s, 6H), 2.43−2.23 (m, 2H), 2.05−1.43 (m, 15H), 1.43−1.13 (m, 5H).

MeOH. Then, the complex was dried under vacuum, and the desired complex was obtained in 55% (32 mg) yield as a stable orange powder. Crystallization from CHCl3/heptane gave at −28 °C red crystals suitable for X-ray analysis. Further product can be achieved from the reaction solution. After removing MeOH, the dark residue was solved in a mixture of CHCl3 and heptane. From the solution, 15 mg (25%) of red crystals was obtained at −28 °C. 1H NMR (300 MHz, CDCl3): δ 8.38 (d, J = 8.9 Hz, 1H, naphthyl), 7.80 (d, J = 8.0 Hz, 1H, naphthyl), 7.72 (d, J = 8.3 Hz, 1H, naphthyl), 7.58−7.33 (m, 3H, naphthyl), 7.21 (d, J = 7.0 Hz, 1H, naphthyl), 5.72 (s, 6H, benzene), 3.98 (d, J = 10.7 Hz, 2H, CH2), 2.37 (m, 2H, Cy), 2.11 (m, 2H, Cy), 1.78 (m, 2H, Cy), 1.69−0.68 (m, 16H, Cy). 13C NMR (75 MHz, CDCl3): δ 133.9, 133.1, 133.0, 128.4, 127.4, 127.3, 127.2, 127.2, 126.0, 125.8, 125.1, 125.0, 87.0, 86.9, 35.9, 29.8, 29.0, 27.4, 27.3, 27.1, 27.0, 26.2. 31P NMR (121 MHz, CDCl3): δ 39.1. HRMS (ESI) m/z+ calcd for C29H37Cl2PRuNa (M + Na)+ 611.09477; found 611.09616. Anal. Calcd for C29H37Cl2PRu: C, 59.18; H, 6.34; P, 5.26. Found: C, 59.19; H, 6.44; P, 5.25. Crystal Data for 2a: C30H41Cl2OPRu, M = 620.57, triclinic, space group P, a = 9.4204(1) Å, b = 10.1326(2) Å, c = 16.0790(3) Å, α = 92.781(1)°, β = 106.513(1)°, γ = 96.699(1)°, V = 1456.06(4) Å3, T = 150(2) K, Z = 2, 27 297 reflections measured, 6670 independent reflections (Rint = 0.0245), final R values (I > 2σ(I)): R1 = 0.0255, wR2 = 0.0707, final R values (all data): R1 = 0.0320, wR2 = 0.0753, 347 parameters; presence of CH3OH in the crystal lattice. Synthesis of [RuCl2(η6-C6H6)(Cy2P(furan-2-ylmethyl))] 2b. Following the procedure for the preparation of 2a, the reaction of [RuCl2(η6-C6H6)]2 (25 mg, 0.05 mmol, 1 equiv) and (dicyclohexyl phosphino)(furan-2-yl)methanone (L2) (29.2 mg, 0.1 mmol, 2 equiv) gave 29 mg (54%) of an orange solid. 1H NMR (300 MHz, CDCl3): δ 7.34−7.21 (m, 1H, furanyl), 6.32−6.28 (m, 1H, furanyl), 6.04−5.99 (m, 1H, furanyl), 5.69 (s, 6H, benzene), 3.57 (d, J = 9.1 Hz, 2H, CH2), 2.36−2.19 (m, 2H, Cy), 2.19−1.03 (m, 2H, Cy), 2.00−1.64 (m, 8H, Cy), 1.56−1.37 (m, 2H, Cy), 1.37−1.09 (m, 8H, Cy). 13C NMR (75 MHz, CDCl3): δ 149.6, 141.0, 141.0, 111.0, 108.7, 108.7, 86.9, 86.8, 38.4, 38.1, 28.7, 28.6, 28.5, 27.6, 27.4, 27.3, 26.3, 18.1. 31P NMR (121 MHz, CDCl3): δ 33.9. HRMS (ESI) m/z+ calcd for C23H33ClOPRu (M − Cl) + 495.09958; found 495.09917. Anal. Calcd for C23H33Cl2OPRu: C, 52.27; H, 6.29; P, 5.86. Found: C, 52.26; H, 6.33; P, 5.89. Synthesis of [RuCl2(η6-C6H6)(Cy2P(thiophen-2-ylmethyl))] 2c. Following the procedure for the preparation of 2a, the reaction of [RuCl2(η6-C6H6)]2 (25 mg, 0.05 mmol, 1 equiv) and (dicyclohexyl phosphino)(thiophen-2-yl)methanone (L3) (30.8 mg, 0.1 mmol, 2 equiv) gave 33 mg (60%) of an orange solid. 1H NMR (300 MHz, CDCl3): δ 7.18−7.13 (m, 1H, thiophenyl), 6.95−6.99 (m, 1H, thiophenyl), 6.85−6.80 (m, 1H, thiophenyl), 5.66 (s, 6H, benzene), 3.78 (d, J = 9.1 Hz, 2H, CH2), 2.46−2.30 (m, 2H, Cy), 2.18−2.05 (m, 2H, Cy), 2.00−1.70 (m, 8H, Cy), 1.57−1.40 (m, 2H, Cy), 1.40−1.18 (m, 2H, Cy). 13C NMR (75 MHz, CDCl3): δ 128.3, 127.8, 127.0, 124.4, 86.9, 86.9, 38.0, 37.8, 29.0, 28.9, 27.6, 27.4, 27.3, 27.2, 26.3. 31P NMR (121 MHz, CDCl3): δ 32.9. HRMS (ESI) m/z+ calcd for C23H33ClPRuS (M − Cl)+ 511.07695; found 511.07765. Anal. Calcd for C23H33Cl2PRuS: C, 50.73; H, 6.11; P, 5.69; S, 5.89. Found: C, 50.98; H, 6.21; P, 5.71; S, 5.85. Synthesis of [RuCl2(η6-C6H6)(Cy2P(benzoyl))] 3. A mixture of [RuCl2(η6-C6H6)]2 (125 mg, 0.25 mmol, 1.0 equiv) and dicyclohexyl benzoyl phosphine (L4) (165 mg, 0.55 mmol, 2.2 equiv) was dissolved in MeOH. The reaction mixture was stirred for 5 h at 50 °C. The solution was fully evaporated in a vacuum and washed three times with heptane. Then, the complex was dried under vacuum to give 221 mg (80%) of 3. 1H NMR (300 MHz, CDCl3): δ 8.19 (d, J = 8.1 Hz, 2H, Ph), 7.65−7.57 (m, 1H, Ph), 7.54−7.46 (m, 2H, Ph), 5.42 (s, 6H, benzene), 2.91−2.72 (m, 2H, Cy), 2.34−2.21 (m, 2H, Cy), 1.83−1.53 (m, 10H, Cy), 1.51−0.97 (m, 10 H, Cy). 13C NMR (75 MHz, CDCl3): δ 210.3, 210.2, 138.3, 137.8, 134.3, 129.1, 128.2, 88.4, 34.4, 34.2, 30.3, 30.3, 28.2, 28.1, 28.0, 27.9, 27.0, 26.9, 25.8. 31P NMR (121 MHz, CDCl 3 ): δ 46.8. HRMS (ESI) m/z + calcd for C25H33Cl2OPRuNa (M + Na)+ 575.05827; found 575.05828. Anal.

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ASSOCIATED CONTENT

S Supporting Information *

NMR spectra of products. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Present Address †

Division of Organic Chemistry, Institute of Chemical and Engineering Sciences, 8 Biomedical grove, Neuros, #07-01, Singapore 138665. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work has been funded by the State of Mecklenburg− Western Pomerania, the BMBF, and the DFG (Leibniz Prize). We thank S. Leiminger for excellent technical assistance. For analytical support, we are grateful to Dipl. Ing.-A Koch and Drs. W. Baumann and C. Fischer. We also thank A. Lehmann for determining the combustion analysis data (all LIKAT).

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REFERENCES

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