Ancillary Metal Centers in Frustrated Lewis Pair Chemistry: Ruthenium

Dec 30, 2013 - The discovery of frustrated Lewis pair (FLP) chemistry revealed that ... from Ru acetylides and Lewis acids resulting in the formation ...
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Ancillary Metal Centers in Frustrated Lewis Pair Chemistry: Ruthenium Acetylide as a Lewis Base in the Activation of CO2, Aldehyde, and Alkyne Michael P. Boone and Douglas W. Stephan* Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6 S Supporting Information *

ABSTRACT: The combination of (indenyl)Ru(PPh3)2(CCPh) (1) with B(C6F4H)3 or Al(C6F5)3 generates FLPs that are shown to react with CO2, aldehyde, and alkyne to generated new C−C bonds. While in these reactions the metal center is ancillary, subsequent reaction of the alkyne addition product with additional alkyne prompts Ru vinylidene chemistry that releases the new organic fragment from Ru.

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RuCl][B(C6F5)4].14 This species exhibits Lewis acidity at carbon on the η6-Ph ring. While this cation behaves as a carbonbased Lewis acid effecting the catalytic hydrogenation of aldimines via an FLP mechanism, this is an unusual situation where the role of the metal is ancillary. The ability of the metal to impart nucleophilic character to the β carbons of the acetylide had been previously established by Bruce and co-workers16 (Scheme 1). In exploring this notion further, we have recently described the reaction of CpRu(PPh3)2(CCPh) with B(C6F5)3 which results in the formation of the species [CpRu(PPh3)2(CC(Ph)(C6F4)(BF(C6F5)2))].15 This reaction is reminiscent of the formation of [(R2PH)(C6F4)(BF(C6F5)2)], the precursors to the first

INTRODUCTION The discovery of frustrated Lewis pair (FLP) chemistry revealed that combinations of sterically encumbered Lewis acids and bases can act in concert to effect the activation of small molecules.1 While reactivity with H2 is perhaps the most surprising demonstration of this concept,2 the activation of other small molecules by FLPs has been extended to olefins, alkynes, CO2,3 SO2,3d,4 N2O,5 NO,6 and even C−H bonds.7 Although a variety of FLP systems have been examined, the vast majority of studies to date have utilized a combination of highly electrophilic main-group Lewis acids and main-group Lewis bases such as phosphines, amines, and carbenes. While the groups of Alcarazo8 and Arduengo9 have reported other carbon-based donors and acceptors in FLP chemistry, a clever extension of this concept has been recently described by Krempner10 demonstrating the ability of a sterically encumbered carbanion to act as a C base in combination with simple boranes to activate H2. In further diversifying the applications of FLP chemistry, Wass and co-workers11 have explored the use of Zr and Ti cationic centers as Lewis acids in combination with pendant phosphine donors. These systems were shown to behave as FLPs activating a variety of substrates including H2, alkynes and CO2, among others, in a fashion similar to that for the maingroup analogues. In a recent work, we have reported the similar ability of neutral Hf amido phosphine systems to capture CO2.12 Extending this to Ru systems, we have recently reported a tris-aminophosphine ruthenium complex which captures CO2 in an FLP-like fashion.13 In all of these cases where transitionmetal species are utilized in FLP chemistry, the role of the metal center has been as a Lewis acid. In a recent report, we described the π-arene complex [((Ph2PC6H4)2B(η6-Ph))© XXXX American Chemical Society

Scheme 1. Reactions of Ru Acetylides

Received: November 18, 2013

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dx.doi.org/10.1021/om401118n | Organometallics XXXX, XXX, XXX−XXX

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spectrum of 3 displayed a signal at 1638 cm−1 attributable to a CO stretch, suggesting the formulation of 3 as [(indenyl)Ru(PPh3)2(CC(Ph)(C(O)OB(C6F4H)3))] (Scheme 2).

FLPs. However, the reaction with B(C6F5)3 suggests that Ru acetylides might also act as sterically encumbered carbon-based donors in FLP chemistry. In this paper, we exploit this observation and report reactions of FLPs derived from Ru acetylides and Lewis acids resulting in the formation of new C− C bonds between the acetylide and CO2, aldehyde, and alkyne.

Scheme 2. Synthesis of 3−7

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RESULTS AND DISCUSSION The compound [(indenyl)Ru(PPh3)2(CCPh)] (1) was heated with B(C6F5)3 at 110 °C for 16 h. Workup resulted in the red crystalline product 2 in 63% yield. The single resonances in 31P and 11B NMR spectra at 35.6 and 0.1 ppm, respectively, together with the 19F NMR signals at −192.0, −132.5, and −140.7 ppm as well as peaks corresponding to two equivalent C6F5 rings were consistent with the formulation of 2 as [(indenyl)Ru(PPh 3 ) 2 (CC(Ph)(C 6 F 4 )BF(C 6 F 5 ) 2 )] (Scheme 1). In this case, the β-alkyne carbon of 1 behaves in a fashion analogous to that for bulky phosphines,2c attacking the borane at a para position of one of the fluoroarene rings, prompting fluoride transfer to boron. This formulation was confirmed via X-ray crystallographic studies (Figure 1) and is analogous to the previously reported species [CpRu(PPh3)2( CC(Ph)(C6F4)BF(C6F5)2)].15

This was confirmed by an X-ray crystallographic study (Figure 2). The Ru−vinylidene fragment gives rise to RuC and C C bond lengths of 1.814(5) and 1.302(6) Å, with a Ru−C−C angle of 172.2(4)°. The C−C bond length between the newly formed vinylidene carbon and the CO2 carbon is 1.494(6) Å. The C−O bond lengths for this fragment were 1.215(5) and 1.299(5) Å, the latter being bound to boron. These bond lengths are reminiscent of those reported for tBu3PC(O)OB(C6F5)3 (1.208(2) and 1.299(2) Å).3j Similarly, 1 was treated with Al(C6F5)3 and 13CO2 for 12 h at 75 °C to give the orange product 4 in 73% yield. The 13C NMR spectrum of 4 displayed one major peak at 166.85 ppm and a 31 1 P{ H} NMR upfield shift at 36.9 ppm. While efforts to observe an 27Al NMR signal were unsuccessful, the 19F NMR spectrum clearly displays signals attributable to ortho, meta and para fluorines from C6F5 rings of Al(C6F5)3, similar to other Albased FLP chemistry.18 Compound 4 was thus formulated and crystallographically confirmed to be the Al(C6F5)3 analogue of 3 (Figure 2). This molecule crystallizes with two molecules in the asymmetric unit,; however, the metric parameters are similar. The RuC and CC bond lengths of 1.802(4) and 1.311(5) Å and Ru−C−C angle of 170.2(4)° differ only slightly from those in 3. The terminal CO bond length was found to be 1.212(5) Å, and the Al-bound O gives rise to a C−O distance of 1.321(5) Å. Compound 4 was found to react further with Al(C6F5)3, affording the new product 5, which displayed a 13C NMR peak at 177.54 ppm, a 31P{1H} NMR signal at 34.4 ppm, and slightly broadened 19F NMR resonances. These, together with the Xray crystallographic data, confirmed the formulation of 5 as (indenyl)Ru(PPh3)2(CC(Ph)(C(OAl(C6F5)3)2)) (Figure 2, Scheme 2). In this case, both oxygen atoms of the captured CO2 molecule are bound to Al(C6F5)3. The geometry about the Ru vinylidene fragment is very similar to that seen in 3 and 4. The C−O bond lengths in the CO2 fragment were found to be 1.274(5) and 1.281(5) Å, as each are bound to Al. The FLPs 1/B(C6F4H)3 and 1/Al(C6F5)3 also reacted with benzaldehyde, affording the new compounds 6 and 7 in 63% and 62% yields, respectively (Scheme 2). In these cases, the 31 1 P{ H} NMR spectra displayed two new resonances shifted upfield, resulting in a 2JPP coupling constant of 25 Hz, consistent with diastereotopic phosphorus centers. In the case

Figure 1. POV-ray depiction of 2. Color scheme: C, black; P, orange; Ru, hunter green; B, yellow-green; F, pink. H atoms are omitted for clarity.

The above observations suggest that the Ru acetylide complex and borane are behaving as a FLP. To circumvent analogous para-attack reactions in main-group FLP chemistry, the Lewis acids B(p-C6F4H)317 and Al(C6F5)318 have been employed. Thus, combination of 1 with B(p-C6F4H)3 showed no observed reaction as evidenced by NMR spectra, suggesting that 1/B(p-C6F4H)3 is an FLP. Exposure of a solution of this FLP to CO2 over 12 h afforded the orange solid 3 in 74% yield. The 31P NMR and 11B NMR spectra both displayed new upfield-shifted resonances at 37.4 and −19.8 ppm, respectively, inferring the presence of a cationic ruthenium vinylidene and a four-coordinate borate. When 13CO2 was used instead of 12 CO2, a distinct singlet at 165.08 ppm in the 13C{1H} NMR spectrum was observed, indicative of CO2 capture. An IR B

dx.doi.org/10.1021/om401118n | Organometallics XXXX, XXX, XXX−XXX

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and 74% yields, respectively. Although not unambiguous, the P{1H}, 11B, and 19F NMR spectra supported the notion of FLP-type addition reactions. This was confirmed, as crystallographic studies of 8 and 9 showed them to be (indenyl)Ru(PPh3)2(CC(Ph)C(Ph)CH(X)) (X = B(C6F4H)3 (8), Al(C6F5)3 (9)) (Figure 3, Scheme 3). In these cases, the FLPs 31

Figure 3. POV-ray depictions of 8 (top) and 9 (bottom). Color scheme: C, black; P, orange; Ru, hunter green; B, yellow-green; Al, light blue; F, pink; H, white. Most H atoms are omitted for clarity. Figure 2. POV-ray depictions of 3 (top), 4 (middle), and 5 (bottom). Color scheme: C, black; P, orange; Ru, hunter green; Al, light blue; B, yellow-green; F, pink; O, red. H atoms are omitted for clarity.

have added across phenylacetylene (Figure 2). For 8 the new C−C bond length between the Ru vinylidene carbon and the alkynyl carbon is 1.481(3) Å, while the former alkyne bond has lengthened to 1.392(3) Å, affording the conjugated vinyl vinylidene. This addition is regioselective, yielding the transaddition product. It is noteworthy that previously observed FLP additions to acetylene were observed to also give exclusive trans-addition products.19 Compound 8 reacts with another 1 equiv of phenylacetylene, giving the new orange product 10 in 92% yield (Scheme 3). The resulting 31P{1H} resonance at 38.6 ppm, the slightly shifted 11B and 19F signals, and the appearance of the 1H resonance at 5.16 ppm suggested the generation of a Ru vinylidene cation. The formulation of 10 was unambiguously determined by X-ray methods to be [(indenyl)Ru(PPh3)2(

of 6 the 11B signal was seen upfield at −2.9 ppm, indicative of a four-coordinate boron, while the 19F resonances for both 6 and 7 were consistent with the presence of borate and aluminate fragments. In addition to the expected 1H resonances derived from 1, resonances at 4.45 and 4.82 ppm were attributed to the incorporated benzaldehyde fragment in 6 and 7, respectively. Similarly, 13C{1H} signals at 74.5 and 79.6 ppm arose from the carbonyl carbon of benzaldehyde. These data support the formulation of 6 and 7 as (indenyl)Ru(PPh3)2(CC(Ph)(CH(Ph)O(X))) (X = B(C6F4H)3 (6), Al(C6F5)3 (7)). Similarly, the FLPs 1/B(C6F4H)3 and 1/Al(C6F5)3 also react with phenylacetylene, giving the red products 8 and 9 in 89% C

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capture CO2, aldehyde, and alkyne, yielding the new C−C bonds in 3−9. That being said, the presence of the metal center does have an impact on the conversion of 8 to 10. Cationic Ru vinylidenes are known to exist in equilibrium with cationic alkyne isomers.2116g,22 In the present case, such isomerism is disfavored as a result of the steric demands in the corresponding alkyne complex. This notion is consistent with NMR studies of 8. However, in the presence of the smaller alkyne phenylacetylene, a further equilibrium exchange process liberates the bulky alkyne, and isomerization of the new Ru alkyne complex to the alkylidiene affords the salt 10 (Scheme 3). This mechanism is reminiscent of that proposed for the dimerization of alkynes by Ru acetylide species;23 however, in the present case the steric demands resulting from the initial FLP chemistry result in the formation of a single regioisomer.

Scheme 3. Mechanism for the Conversion of 8 to 10

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CONCLUSIONS In summary, the utilization of electron-rich Ru acetylide species produces a Lewis basic β-carbon center which in combination with a Lewis acid acts as an FLP. These combinations are capable of effecting the FLP activation of CO2, aldehyde, and alkyne, resulting in the formation of new C−C bonds in 3−10. While the role of the metal in these FLP activations is ancillary, its presence in the case of the alkyne reaction allows subsequent reaction, liberating the ene-yne-borate anion in 10. While Erker and co-workers24 have exploited FLP reductions for organometallic derivatives, the current finding provides an unique example of the use of organometallic bases in FLP chemistry and expands the realm of C-based Lewis bases. It is the subsequent development of organometallic-FLP chemistry toward cooperative reactivity and catalysis that is the subject of current studies.

CC(H)(Ph))][(PhCC)(Ph)CC(H)(B (C6F4H)3)] (Figure 4). Compound 10 was also obtained directly from 1 and B(C6F4H)3 by the addition of 2 equiv of phenylacetylene (Scheme 3).

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EXPERIMENTAL SECTION

General Considerations. All manipulations were carried out under an atmosphere of dry, O2-free N2 employing an MBraun glovebox and a Schlenk vacuum line. Solvents were purified with a Grubbs-type column system manufactured by Innovative Technology and dispensed into thick-walled Schlenk glass flasks equipped with Teflon-valve stopcocks (hexane and CH2Cl2) or were dried over the appropriate agents and distilled into the same kind of storage flasks (C6H5Br and C6H12). All solvents were thoroughly degassed after purification (repeated freeze−pump−thaw cycles). Deuterated solvents were dried over the appropriate agents, vacuum-transferred into storage flasks with Teflon stopcocks, and degassed accordingly (CD2Cl2 and C6D5Br). 1H, 11B, 13C, 19F, and 31P NMR spectra were recorded at 25 °C with Bruker 400 MHz spectrometers. Chemical shifts are given relative to SiMe4 and referenced to the residual solvent signal (1H, 13C) or relative to an external standard. 11B, 19F, and 31P resonances were referenced externally to BF3·Et2O, CFCl3, and 85% H3PO4, respectively. In some instances, signal and/or coupling assignment was derived from two-dimensional NMR experiments. In these cases additional coupling constants were not resolved. Chemical shifts are reported in ppm and coupling constants as scalar values in Hz. Combustion analyses were performed in house, employing a PerkinElmer 2400 Series II CHNS Analyzer. 1,25 HB(C6F5)2,26 Al(C6F5)3 tol,27 and B(p-C6F4H)317 were prepared as previously reported. 13CO2 (Aldrich), phenylacetylene (Aldrich), benzaldehyde (Aldrich), [Ph3C][B(C6F5)4] (Aldrich), and B(C6F5)3 (Boulder Scientific) were purchased and used as received. CO2 (grade 4.0) was purchased from Linde and passed through a Drierite column prior to use. Synthesis of (indenyl)Ru(PPh3)2(CC(Ph)C6F4B(F)(C6F5)2) (2). B(C6F5)3 (0.102 g, 0.200 mmol) in C6H5Br (1 mL) was added to (indenyl)Ru(PPh3)2CCPh (0.168 g, 0.200 mmol) in C6H5Br (1 mL),

Figure 4. POV-ray depiction of 10. Color scheme: C, black; P, orange; Ru, hunter green; B, yellow-green; F, pink; H, white. All H atoms except those of the vinyl and vinylidene groups are omitted for clarity.

The above reactions demonstrate that the Ru acetylide and suitable Lewis acids behave as FLPs. This can be attributed to the resonance form of the acetylide, which imparts basicity at the β-carbon center (Scheme 1). In addition, the (indenyl)Ru(PPh3)2 fragment acts as a bulky substituent to frustrate interaction with the electrophilic borane B(C6F4H)3 or alane Al(C6F5)3. Moreover, for the borane B(C6F4H)3 the proton in the para position precludes nucleophilic aromatic substitution.17b Similarly, Al(C6F5)3 in combination with 1 behaves as an FLP, as para attack by nucleophiles is not observed.3h,20 Thus, in the case of these FLPs, the chemistry does not occur at the metal center but rather the metal fragment acts as an ancillary or bystanding group. Nonetheless, these FLPs react to D

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and the reaction mixture was heated to 110 °C for 16 h. The mixture was then layered with cyclohexane (5 mL) to yield X-ray-quality dark red crystals (0.170 g, 63%). Data for 2 are as follows. 1H NMR (CD2Cl2): 7.46−7.37 (m, 7H, Ph), 7.25−7.14 (m, 18H, Ph), 6.95 (m, 2H, Ph/Ind), 6.69−6.57 (m, 10H, Ph), 6.40 (s, 1H, Ind), 5.82−5.75 (m, 2H, Ind), 5.51−5.42 (m, 2H, Ind). 31P{1H} NMR (CD2Cl2): 35.6 (s, PPh3). 11B NMR (CD2Cl2): 0.1 (br s). 19F NMR (CD2Cl2): −132.55 (m, 2F, C6F4), −133.67 (m, 4F, o-C6F5), −140.58 (m, 2F, C6F4), −161.15 (t, 2F, 3JFF = 21 Hz, p-C6F5), −165.76 (m, 4F, m-C6F5), −192.04 (br s, 1F, BF). 13 C{1H} NMR (partial, CD2Cl2): 133.75 (t, JPC = 5 Hz, Ph), 133.32 (s, Ph), 132.83 (s, Ph), 131.53 (s, Ph), 131.21 (s, Ph), 130.47 (s, Ph), 130.18 (s, Ph), 130.17 (s, Ph), 129.21 (s, Ind), 128.82 (s, Ph), 128.43 (t, JPC = 5 Hz, Ph), 128.25 (s, Ph), 123.64 (s, Ind), 117.40 (s, Ph), 100.31 (s, Ind), 82.39 (s, Ind). Anal. Calcd for C71H42BF15P2Ru· C6H12·1/2CH2Cl2 (1480.04): C, 62.87; H, 3.74. Found: C, 62.30; H, 4.13. Synthesis of (indenyl)Ru(PPh 3 ) 2 (CC(Ph)(C(O)OB(C6F4H)3)) (3). B(p-C6F4H)3 (0.014 g, 0.030 mmol) in CD2Cl2 (0.3 mL) was added to 1 (0.025 g, 0.030 mmol) in CD2Cl2 (0.3 mL). The reaction mixture was then added to a J. Young tube, pressurized with CO2, and allowed to react for 16 h. To the orange solution was added cyclohexane (5 mL) by slow diffusion, yielding orange X-ray-quality crystals of the final product (0.030 g, 74%). Data for 3 are as follows. 1H NMR (CD2Cl2): 7.48−7.38 (m, 7H, Ph), 7.21−7.00 (m, 17H, Ph), 6.79−6.65 (m, 14H, Ph), 6.56 (d, 2H, JHH = 7 Hz, Ind), 6.22 (m, 1H, Ind), 5.62 (m, 2H, Ind), 5.45 (m, 2H, Ind). 31P{1H} NMR (CD2Cl2): 37.4 (s, PPh3). 11B NMR (CD2Cl2): −19.8 (s). 19F NMR (CD2Cl2): −133.16 (m, 6F, o-C6F4H), −142.97 (m, 6F, m-C6F4H). 13C{1H} NMR (partial, CD2Cl2): 165.08 (s, CO2), 134.08 (t, JPC = 5 Hz, Ph), 133.49 (t, JPC = 5 Hz, Ph), 133.44 (s, Ph), 133.11 (s, Ph), 132.85 (s, Ph), 132.63 (s, Ph), 131.29 (s, Ind), 130.85 (s, Ph), 130.47 (s, Ph), 129.99 (s, Ph), 128.62 (t, JPC = 6 Hz, Ph), 128.25 (s, Ph), 127.94 (s, Ph), 127.58 (s, Ph), 127.17 (s, Ph), 126.99 (s, Ph), 124.93 (s, Ph), 123.37 (s, Ind), 117.00 (s, Ph), 101.87 (s, Ph), 101.64 (s, Ph), 101.41 (s, Ph), 101.05 (s, Ph), 100.08 (s, Ind), 81.50 (s, Ind). IR (from KBr plate): ν 1638 cm−1 (CO). Anal. Calcd for C72H45BF12P2Ru·1/2C6H12 (1386.03): C, 64.99; H, 3.71. Found: C, 64.88; H, 4.32. Synthesis of (indenyl)Ru(PPh3)2(CC(Ph)(C(O)OAl(C6F5)3)) (4). Al(C6F5)3tol (0.013 g, 0.021 mmol) in C6D5Br (0.3 mL) was added to 1 (0.017 g, 0.020 mmol) in C6D5Br (0.3 mL). The reaction mixture was then transferred to a J. Young tube, pressurized with CO2 ,and allowed to react for 16 h at 75 °C. The orange solution was then layered with cyclohexane (5 mL) and upon slow diffusion yielded orange X-ray-quality crystals of the final product (0.021 g, 73%). Data for 4 are as follows. 1H NMR (C6D5Br): 7.10 (s, 3H, Ph), 7.05−6.94 (m, 6H, Ph), 6.86−6.76 (m, 13H, Ph), 6.74 (s, 3H, Ph), 6.72−6.66 (m, 2H, Ind), 6.54−6.38 (m, 10H, Ph), 5.83 (br s, 1H, Ind), 5.26−5.18 (m, 2H, Ind), 4.98 (br s, 2H, Ind). 31P{1H} NMR (C6D5Br): 36.9 (s, PPh3). 27Al NMR (C6D5Br): no signal observed. 19 F NMR (C6D5Br): −121.79 (m, 6F, o-C6F5), −157.21 (t, 3F, 3JFF = 20 Hz, p-C6F5), −163.36 (m, 6F, m-C6F5).13C{1H} NMR (partial, C6D5Br): 166.85 (s, CO2), 134.02 (t, JPC = 6 Hz, Ph), 132.90 (s, Ph), 132.39 (s, Ph), 131.35 (s, Ph), 130.56 (s, Ph), 130.47 (s, Ph), 128.89 (s, Ph), 128.12 (t, JPC = 5 Hz, Ph), 127.93 (s, Ind), 127.47 (s, Ph), 127.19 (s, Ph), 124.56 (s, Ph), 123.21 (s, Ph), 122.63 (s, Ind), 122.00 (s, Ph), 116.84 (s, Ph), 100.34 (s, Ind), 81.24 (s, Ind). Anal. Calcd for C72H42AlF15O2P2Ru (1414.08): C, 61.15; H, 2.99. Found: C, 60.78; H, 3.16. Synthesis of (indenyl)Ru(PPh3)2(CC(Ph)(C(OAl(C6F5)3)OAl(C6F5)3)) (5). Al(C6F5)3tol (0.026 g, 0.042 mmol) in C6D5Br (0.3 mL) was added to 1 (0.017 g, 0.020 mmol) in C6D5Br (0.3 mL). The reaction mixture was then added to a J. Young tube, pressurized with CO2, and allowed to react for 16 h. The dark red solution was then layered with cyclohexane (5 mL) and upon slow diffusion yielded red X-ray-quality crystals of the final product (0.028 g, 75%). Data for 5 are as follows. 1H NMR (C6D5Br): 7.13−6.64 (m, 23H, Ph), 6.61−6.26 (m, 12H, Ph), 6.21 (t, 1H, JHH = 8 Hz, Ph), 5.96 (t, 2H, JHH = 8 Hz, Ind), 5.80 (d, 2H, JHH = 8 Hz, Ind), 5.13−5.02 (m,

3H, Ind). 31P{1H} NMR (C6D5Br): 34.4 (s, PPh3). 27Al NMR (C6D5Br): no signal observed. 19F NMR (C6D5Br): −121.15 (br m, 12F, o-C6F5), −154.00 (br m, 6F, p-C6F5), −162.31 (br m, 12F, mC6F5). 13C{1H} NMR (partial, C6D5Br): 177.54 (s, CO2),151.32 (m, Ph), 148.76 (m, Ph), 142.29 (m, Ph), 139.89 (m, Ph), 138.04 (m, Ph), 135.50 (m, Ph), 134.01 (m, Ph), 133.67 (m, Ph), 133.19 (m, Ph), 132.56 (HSQC, Ind), 131.96 (s, Ph), 131.77 (s, Ph), 131.55 (s, Ph), 128.93 (m, Ph), 128.45 (m, Ph), 128.04 (HSQC, Ind), 127.97 (HSQC, Ind), 127.06 (s, Ph), 123.39 (s, Ph), 123.16 (HSQC, Ind), 121.57 (s, Ph), 119.12 (s, Ph), 99.99 (s, Ph), 97.57 (s, Ph), 80.77 (HSQC, Ind). Anal. Calcd for C90H42Al2F30O2P2Ru·C6H12 (2026.41): C, 56.90; H, 2.69. Found: C, 57.14; H, 3.07. Synthesis of (indenyl)Ru(PPh 3 ) 2(CC(Ph)(CH(Ph)OB(C6F4H)3)) (6) and (indenyl)Ru(PPh3)2(CC(Ph)(CH(Ph)OAl(C6F5)3)) (7). These compounds were prepared in a similar fashion, and thus only one preparation is detailed. B(C6F4H)3 (0.010 g, 0.021 mmol) in CH2Cl2 (0.3 mL) was added to 1 (0.017 g, 0.020 mmol) in CH2Cl2 (0.3 mL). The reaction mixture was then added to PhCHO (0.003 g, 0.028 mmol) and allowed to react for 2 h. The resulting red solution was pumped dry and washed with pentane to yield a red solid (0.019 g, 63%). Data for 6 are as follows. 1H NMR (CD2Cl2): 7.58−7.38 (m, 8H, Ph), 7.33−7.23 (m, 4H, Ph), 7.23−6.61 (m, 19H, Ph), 6.58−6.43 (m, 4H, Ph), 6.27−6.18 (m, 3H, Ph), 6.11−5.95 (m, 5H, Ph), 5.53−5.46 (m, 3H, Ind), 5.32−5.23 (m, 2H, Ind), 5.03 (m, 2H, Ind), 4.45 (s, 1H, −CHO−). 31P{1H} NMR (CD2Cl2): 38.8 (d, 2JPP = 25 Hz, PPh3), 33.7 (d, 2JPP = 25 Hz, PPh3). 11B NMR (CD2Cl2): −2.9 (s).19F NMR (CD2Cl2): −131.05 (m, 6F, o-C6F5), −143.97 (m, 6F, m-C6F5). 13 C{1H} NMR (partial, CD2Cl2) 135.02 (s, Ph), 134.49 (s, Ph), 133.87 (s, Ph), 133.05 (s, Ph), 131.60 (s, Ph), 131.13 (s, Ph), 130.77 (s, Ph), 129.81 (s, Ph), 128.97 (s, Ph), 128.70 (s, Ph), 128.35 (s, Ph), 128.29 (s, Ph), 127.87 (s, Ph), 127.50 (s, Ph), 127.11 (s, Ph), 126.16 (s, Ph), 125.97 (s, Ph), 125.57 (s, Ph), 125.27 (s, Ph), 124.84 (s, Ph), 123.67 (s, Ph), 123.27 (s, Ph), 122.80 (s, Ind), 116.09 (s, Ph), 109.17 (s, Ph), 98.91 (s, Ph), 94.96 (s, Ph), 83.39 (s, Ind), 79.10 (s, Ind), 79.38 (s, Ind), 74.47 (HSQC, CH−O). Anal. Calcd for C78H51BF15OP2Ru (1406.05): C, 66.63; H, 3.66. Found: C, 67.07; H, 3.81. Data for 7 are as follows. Yield: 0.021 g, 63%. 1H NMR (C6D5Br): 7.37−6.69 (m, 34H, Ph), 6.48−6.34 (m, 6H, Ph/Ind), 5.49 (s, 2H, Ind), 5.35 (m, 1H, Ind), 5.07 (m, 1H, −CHO−),. 31P{1H} NMR (C6D5Br): 38.7 (d, 2JPP = 25 Hz, PPh3), 36.6 (d, 2JPP = 25 Hz, PPh3). 27 Al NMR (C6D5Br): blank. 19F NMR (C6D5Br): −120.87 (m, 6F, oC6F5), −157.06 (t, 3F, 3JFF = 20 Hz, p-C6F5), −162.81 (m, 6F, mC6F5). 13C{1H} NMR (partial, C6D5Br): 145.60 (s, Ph), 137.50 (s, Ph), 136.45 (s, Ph), 134.60 (m, Ph), 134.03 (m, Ph), 133.71 (m, Ph), 133.37 (m, Ph), 132.55 (s, Ph), 131.60 (s, Ph), 130.51−127.85 (m, Ph), 127.37 (s, Ph), 127.28 (s, Ph), 126.97 (s, Ph), 126.69 (s, Ph), 125.38 (s, Ph), 124.96 (s, Ph), 123.61 (m, Ph), 123.21 (m, Ph), 121.10 (s, Ph), 117.01 (s, Ph), 116.08 (s, Ph), 100.85 (s, Ind), 133.90 (s, Ind), 126.01 (s, Ind), 81.24 (s, Ind), 79.58 (HSQC, CH−O). Anal. Calcd for C78H48AlF15OP2Ru (1476.19): C, 63.46; H, 3.28. Found: C, 63.04; H, 2.97. Synthesis of (indenyl)Ru(PPh 3) 2 (CC(Ph)C(Ph)CH(B(C6F4H)3)) (8) and (indenyl)Ru(PPh3)2(CC(Ph)C(Ph)CH(Al(C6F5)3)) (9). These compounds were prepared in a similar fashion, and thus only one preparation is detailed. B(C6F4H)3 (0.019 g, 0.042 mmol) in CH2Cl2 (0.5 mL) was added to 1 (0.034 g, 0.040 mmol) in CH2Cl2 (0.5 mL). Phenylacetylene (0.004 g, 0.040 mmol) was then added to this reaction mixture, resulting in a deep red solution. This solution was then layered with cyclohexane (5 mL) and upon slow diffusion yielded red X-ray-quality crystals of the final product (0.050 g, 89%). Data for 8 are as follows. 1H NMR (CD2Cl2): 7.49 (br s, 1H,  CH), 7.43−7.36 (m, 6H, Ph), 7.27−7.11 (m, 13H, Ph), 7.09−7.01 (m, 2H, Ph/Ind), 6.91−6.78 (m, 4H, Ph), 6.76−6.54 (m, 18H, Ph), 6.40 (d, 2H, JHH = 7 Hz, Ph/Ind), 6.29 (s, 1H, Ph/Ind), 5.47−5.39 (m, 4H, Ph/Ind). 31P{1H} NMR (CD2Cl2): 38.6 (s, PPh3). 11B NMR (CD2Cl2): −15.1 (s). 19F NMR (CD2Cl2): −131.02 (m, 6F, oC6F4H), −144.64 (m, 6F, m-C6F4H). 13C{1H} NMR (partial, E

dx.doi.org/10.1021/om401118n | Organometallics XXXX, XXX, XXX−XXX

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CD2Cl2): 142.39 (s, Ar), 134.17 (t, JPC = 5 Hz, Ar), 133.49 (s, Ar), 131.26 (s, Ar), 131.07 (s, Ar), 130.70 (s, Ar), 129.96 (s, Ar), 129.60 (s, Ar), 129.04 (s, Ar), 128.25 (t, JPC = 5 Hz, Ar), 127.53 (s, Ar), 126.51 (s, Ar), 126.33 (s, Ar), 125.09 (s, Ar), 123.54 (s, Ar), 116.92 (s, Ar), 101.16 (s, Ar), 100.94 (s, Ar), 100.71 (s, Ar), 100.09 (s, Ar), 79.02 (s, Ar). Anal. Calcd for C72H45BF12P2Ru·1.5CH2Cl2 (1529.46): C, 63.36; H, 3.54. Found: C, 63.58; H, 3.72. Data for 9 are as follows. 1H NMR (C6D5Br): 7.50 (m, 1H, CH), 7.24−7.10 (m, 7H, Ph), 7.07−6.90 (m, 17H, Ph), 6.89−6.84 (m, 1H, Ph), 6.82−6.59 (m, 15H, Ph), 5.94−5.85 (m, 2H, Ind), 5.47 (s, 1H, Ind), 5.29 (m, 2H, Ind), 5.21 (m, 1H, Ind), 5.13 (m, 1H, Ind). 31 1 P{ H} NMR (C6D5Br): 39.0 (s, PPh3). 27Al NMR (C6D5Br): blank. 19 F NMR (C6D5Br): −120.13 (m, 6F, o-C6F5), −157.59 (t, 3F, 3JFF = 20 Hz, p-C6F5), −163.05 (m, 6F, m-C6F5). 13C{1H} NMR (partial, C6D5Br): 134.03 (m, Ph), 133.23 (m, Ph), 132.59 (s, Ph), 132.18 (HSQC, CH−), 132.01 (s, Ph), 130.27 (s, Ph), 128.92 (s, Ph), 128.45 (m, Ph), 128.15, 127.87 (s, Ph), 127.31 (s, Ph), 127.13 (s, Ph), 127.07 (m, Ph), 126.42 (s, Ph), 123.07 (HSQC, Ind), 122.82 (HSQC, Ind), 118.65 (HSQC, Ind), 98.14 (HSQC, Ind), 83.22 (HSQC, Ind), 79.33 (HSQC, Ind). Anal. Calcd for C79H48AlF15P2Ru (1472.20): C, 64.45; H, 3.29. Found: C, 63.93; H, 3.07. Synthesis of [(indenyl)Ru(PPh3)2(CC(H)(Ph)][(B(C6F4H)3)C(H)C(Ph)(CCPh)] (10). B(C6F4H)3 (0.019 g, 0.042 mmol) in CH2Cl2 (0.5 mL) was transferred to 1 (0.034 g, 0.040 mmol) in CH2Cl2 (0.5 mL). Excess phenylacetylene was then added to this reaction, resulting in a deep red solution. This solution was then layered with cyclohexane (5 mL) and upon slow diffusion yielded orange X-ray-quality crystals of the final product (0.055 g, 92%). Data for 10 are as follows. 1H NMR (CD2Cl2): 7.52 (br s, 1H,  C−H), 7.39−7.26 (m, 8H, Ph), 7.20−7.00 (m, 22H, Ph/Ind), 6.87− 6.72 (m, 17H, Ph), 6.47 (m, 3H, Ph/Ind), 6.03 (m, 2H, Ph/Ind), 5.65 (m, 1H, Ph/Ind), 5.51 (m, 2H, Ph/Ind), 5.16 (br s, 1H, vinylidene). 31 1 P{ H} NMR (CD2Cl2): 38.6 (s, PPh3). 11B NMR (CD2Cl2): −15.8 (s, B(C6F4H)3. 19F NMR (CD2Cl2): −132.11 (m, 6F, o-C6F4H), −144.89 (m, 6F, m-C6F4H). 13C{1H} NMR (partial, CD2Cl2): 141.83 (s, Ar), 133.79 (t, JPC = 5 Hz, Ar), 133.64 (s, Ar), 133.49 (s, Ar), 133.14 (s, Ar), 133.06 (s, Ar), 131.63 (s, Ar), 131.56 (s, Ar), 130.78 (s, Ar), 129.25 (s, Ar), 128.92 (t, JPC = 5 Hz, Ar), 128.61 (s, Ar), 128.35 (s, Ar), 127.77 (s, Ar), 127.51 (s, Ar), 127.32 (s, Ar), 127.08 (s, Ar), 127.03 (s, Ar), 125.65 (s, Ar), 125.52 (s, Ar), 123.61 (s, Ar), 118.72 (s, Ar), 116.02 (s, Ar), 101.09 (s, Ar), 98.83 (s, Ar), 83.97 (t, JPC = 3 Hz, Ar), 83.65 (s, Ar). Anal. Calcd for C72H45BF12P2Ru·CH2Cl2·C6H12 (1630.33): C, 67.47; H, 4.28. Found: C, 67.74; H, 4.36. X-ray Data Collection, Reduction, Solution, and Refinement. Crystals were coated in Paratone-N oil in the glovebox, mounted on a MiTegen Micromount, and placed under an N2 stream, thus maintaining a dry, O2-free environment for each crystal. The data were collected on a Kappa Bruker Apex II diffractometer. Data collection strategies were determined using Bruker Apex 2 software and optimized to provide >99.5% complete data to a 2θ value of at least 55°. The data were collected at 150(±2) K for all compounds. The data integration and absorption correction were performed with the Bruker Apex 2 software package.28 Non-hydrogen atomic scattering factors were taken from the literature tabulations.29 The heavy-atom positions were determined using direct methods employing the SHELX-2013 direct methods routine. The remaining nonhydrogen atoms were located from successive difference Fourier map calculations. The refinements were carried out by using full-matrix least-squares techniques on F, minimizing the function w(Fo − Fc)2, where the weight w is defined as 4Fo2/2σ(Fo2) and Fo and Fc are the observed and calculated structure factor amplitudes, respectively. In the final cycles of each refinement, all non-hydrogen atoms were assigned anisotropic temperature factors in the absence of disorder or insufficient data. In the latter cases atoms were treated isotropically. C−H atom positions were calculated and allowed to ride on the carbon to which they are bonded, assuming a C−H bond length of 0.95 Å. H atom temperature factors were fixed at 1.20 times the isotropic temperature factor of the C atom to which they are bonded. The H atom contributions were calculated but not refined. The locations of the largest peaks in the final difference Fourier map

calculation as well as the magnitude of the residual electron densities in each case were of no chemical significance.

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ASSOCIATED CONTENT

S Supporting Information *

CIF files giving crystallographic data for 2−5 and 8−10. This material is available free of charge via the Internet at http:// pubs.acs.org. These data are also available from the CCDC as file nos. 968230−968236.

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AUTHOR INFORMATION

Corresponding Author

*E-mail for D.W.S.: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS D.W.S. gratefully acknowledges the financial support of the NSERC of Canada and the award of a Canada Research Chair. Dedicated to Professor Irina Petrovna Beletskaya for her contributions to metal-catalysed reactions.

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REFERENCES

(1) (a) Stephan, D. W.; Erker, G. Angew. Chem., Int. Ed. 2010, 49, 46−76. (b) Stephan, D. W. Dalton Trans. 2009, 3129−3136. (c) Stephan, D. W. Org. Biomol. Chem. 2008, 6, 1535−1539. (2) (a) Stephan, D. W.; Erker, G. Top. Curr. Chem. 2013, 332, 85− 110. (b) Stephan, D. W. Org. Biomol. Chem. 2012, 10, 5740−5746. (c) Welch, G. C.; Juan, R. R. S.; Masuda, J. D.; Stephan, D. W. Science 2006, 314, 1124−1126. (3) (a) Dobrovetsky, R.; Stephan, D. W. Angew. Chem., Int. Ed. 2013, 52, 2516−2519. (b) Sgro, M. J.; Domer, J.; Stephan, D. W. Chem. Commun. 2012, 48, 7253−7255. (c) Neu, R. C.; Menard, G.; Stephan, D. W. Dalton Trans. 2012, 41, 9016−9018. (d) Lavigne, F.; Maerten, E.; Alcaraz, G.; Branchadell, V.; Saffon-Merceron, N.; Baceiredo, A. Angew. Chem., Int. Ed. 2012, 51, 2489−2491. (e) Zhao, X. X.; Stephan, D. W. Chem. Commun. 2011, 47, 1833−1835. (f) Peuser, I.; Neu, R. C.; Zhao, X. X.; Ulrich, M.; Schirmer, B.; Tannert, J. A.; Kehr, G.; Frohlich, R.; Grimme, S.; Erker, G.; Stephan, D. W. Chem. Eur. J. 2011, 17, 9640−9650. (g) Menard, G.; Stephan, D. W. Angew. Chem., Int. Ed. 2011, 50, 8396−8399. (h) Ménard, G.; Stephan, D. W. J. Am. Chem. Soc. 2010, 132, 1796−1797. (i) Dureen, M. A.; Stephan, D. W. J. Am. Chem. Soc. 2010, 132, 13559−13568. (j) Mömming, C. M.; Otten, E.; Kehr, G.; Fröhlich, R.; Grimme, S.; Stephan, D. W.; Erker, G. Angew. Chem., Int. Ed. 2009, 48, 6643−6646. (k) Ashley, A. E.; Thompson, A. L.; O’Hare, D. Angew. Chem., Int. Ed. 2009, 48, 9839−43. (4) Sajid, M.; Klose, A.; Birkmann, B.; Liang, L. Y.; Schirmer, B.; Wiegand, T.; Eckert, H.; Lough, A. J.; Frohlich, R.; Daniliuc, C. G.; Grimme, S.; Stephan, D. W.; Kehr, G.; Erker, G. Chem. Sci. 2013, 4, 213−219. (5) (a) Stephan, D. W. Top. Curr. Chem. 2013, 332, 1−44. (b) Menard, G.; Hatnean, J. A.; Cowley, H. J.; Lough, A. J.; Rawson, J. M.; Stephan, D. W. J. Am. Chem. Soc. 2013, 135, 6446−6449. (c) Tolman, W. B. Angew. Chem., Int. Ed. 2010, 49, 1018−1024. (d) Otten, E.; Neu, R. C.; Stephan, D. W. J. Am. Chem. Soc. 2009, 131, 9918−9919. (e) Neu, R. C.; Otten, E.; Stephan, D. W. Angew. Chem., Int. Ed. 2009, 48, 9709−9712. (6) (a) Sajid, M.; Stute, A.; Cardenas, A. J. P.; Culotta, B. J.; Hepperle, J. A. M.; Warren, T. H.; Schirmer, B.; Grimme, S.; Studer, A.; Daniliuc, C. G.; Frohlich, R.; Petersen, J. L.; Kehr, G.; Erker, G. J. Am. Chem. Soc. 2012, 134, 10156−10168. (b) Cardenas, A.; Culotta, B.; Warren, T.; Grimme, S.; Stute, A.; Frohlich, R.; Kehr, G.; Erker, G. Angew. Chem., Int. Ed. 2011, 50, 7567−7571. (c) Unverhau, K.; Lubbe, G.; Wibbeling, B.; Frohlich, R.; Kehr, G.; Erker, G. Organometallics 2010, 29, 5320−5329. F

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Organometallics

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dx.doi.org/10.1021/om401118n | Organometallics XXXX, XXX, XXX−XXX