B Lewis Pairs with

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Reactions of Modified Intermolecular Frustrated P/B Lewis Pairs with Dihydrogen, Ethene, and Carbon Dioxide‡ Marcel Harhausen, Roland Fröhlich,† Gerald Kehr, and Gerhard Erker* Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, 48149 Münster, Germany S Supporting Information *

ABSTRACT: In this contribution, we discuss the reactivity of different phosphanes (XPhos (1a), tBuXPhos (1b), and Mes2PEt (1c)) and tris(pentafluorophenyl)borane (and in one case, EtB(C6F5)2) against small molecules. 1a/B(C6F5)3, 1b/B(C6F5)3, and 1c/B(C6F5)3 split dihydrogen heterolytically to yield the phosphonium borate salts 2a, 2b, and 2c, respectively. Control experiments with D2 gave the respective deuterated phosphonium borates 2a-D2, 2b-D2, and 2c-D2. The FLP systems 1b/ B(C6F5)3 and 1c/B(C6F5)3 underwent 1,2-addition reactions with ethene, resulting in the generation of the ethylene-bridged phosphonium borates 3b and 3c. As well, the Lewis pair EtB(C6F5)2 and Mes2PEt reacted with ethene to yield the corresponding 1,2-addition product 3d. At low temperature, the FLP systems 1a/B(C6F5)3 and 1c/B(C6F5)3 coordinated carbon dioxide (4a, 4c). The new compounds 2a, 2b, 3b, 3c, 3d, 4a, and 4c were characterized by X-ray crystal structure analyses.

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INTRODUCTION The synthesis of tris(pentafluorophenyl)borane was described by Professor F. G. A. Stone and his co-workers in 1963.1 This unique boron Lewis acid was used extensively as an activator component in homogeneous Ziegler−Natta olefin polymerization catalysis.2 It was also employed as a very potent Lewis acid catalyst in organic synthesis3 and it recently opened useful new variants of the 1,1-carboboration reaction.4 In recent years, B(C6F5)3 and some of its derivatives have seen extensive use as a Lewis acid component in frustrated Lewis pair chemistry.5 The strongly Lewis acidic −C6F5 substituted boranes are very well suited to generate pairs of Lewis acids and bases in solution that, due to their steric bulk, do not annihilate each other by the otherwise usually observed strong adduct formation. The coexistence of active Lewis acid and base components in solution allows for a unique array of cooperative reactions with a variety of added substrates to take place.6 Frustrated Lewis pairs (FLPs) thus undergo remarkable reactions with a variety of small molecules. Many FLP systems can cleave dihydrogen heterolytically;7 some examples have served as potent nonmetallic catalysts for the hydrogenation of a variety of olefinic or acetylenic substrates under rather mild reaction conditions.8 Many FLP examples were shown to react with unsaturated organic substrates, including various carbonyl compounds;9 they react with alkenes10 and alkynes4,11 (including conjugated variants). FLP addition reactions to N2O12 and even to NO13 have been reported, the latter leading to the new class of the persistent P/B FLP-NO nitroxide © 2012 American Chemical Society

radicals. Inter- as well as intramolecular FLPs were shown to take up carbon dioxide reversibly.14 Most of these remarkable reactions were carried out by phosphane/borane FLPs,6 although an increasing number of FLPs has become known that utilize amine Lewis bases15 and even carbon-based Lewis base components.16 The vast majority of the presently known FLPs uses boron Lewis acid components that bear strongly electron-withdrawing −C6F5 substituents. Probably the largest amount of reports on FLP reactions is on the P/B systems. Among them, variants of the system I are the most utilized intramolecular systems.7 The phosphane/borane combination II and some of its variants are probably the most frequently employed reactive intermolecular FLPs to date (see Chart 1).7 In this account, we will report on a Chart 1

trio of typical FLP reactions of a series of new P/B FLPs, namely, the heterolytic cleavage of dihydrogen and the addition reactions to ethene and to carbon dioxide. These make use of simple commercially available or easily synthesized phosphanes. Special Issue: F. Gordon A. Stone Commemorative Issue Received: November 3, 2011 Published: January 4, 2012 2801

dx.doi.org/10.1021/om201076f | Organometallics 2012, 31, 2801−2809

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isotopomer 2a-D2 was isolated in 68% yield. It features a PD doublet in the 2H NMR spectrum at δ 5.48 (1JPD ∼ 71 Hz) and a broad BD resonance at δ 3.63. The 31P NMR spectrum showed the phosphonium PD signal as a 1:1:1 triplet at δ 14.1 with a ca. 14% residual PH resonance at δ 15.1 (for further details see the Supporting Information). Single crystals of the phosphonium/hydridoborate salt 2a that were suited for the X-ray crystal structure analysis were obtained from a solution of 2a in dichloromethane covered with heptane at −30 °C. In the crystal, the product 2a features independent phosphonium cations and hydroborate anions. The boron atom is tetracoordinated (sum of the C−B−C angles at boron: 338.0°) and shows a hydride attached to it. The phosphorus atom is also tetracoordinated (sum of the C− P−C bond angles at phosphorus: 335.6°) and it has the proton attached to it. The bulky triisopropylphenyl substituent at the o-position of the P-bonded phenyl group is rotated normal to the phenyl plane and shields the P−H vector in this orientation (see Figure 1).

They were combined with the B(C6F5)3 Lewis acid or readily available derivatives thereof. Our study shows that the scope of the structural features and the chemical composition of frustrated Lewis pairs can easily be substantially expanded and utilized for carrying out a variety of typical frustrated Lewis pair reactions that readily take place under mild reaction conditions.

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RESULTS AND DISCUSSION For this study, we used three phosphanes, namely, the commercially available specifically substituted systems XPhos (1a)17 and tBuXPhos (1b)17 and ethyldimesitylphosphane (Mes 2 PEt) (1c) (see Chart 2). The former pair of Chart 2

aryldialkylphosphanes bear very bulky o-substituted aryl groups. They have previously found extensive use in Pd-catalyzed organic transformations where they had been introduced as especially useful ligand systems to control C−N bond-forming reactions.17 We prepared compound 1c from ethyldichlorophosphane by reaction with 2 mol equiv of mesityllithium. Phosphane 1c was obtained in 78% yield. It shows a 31P NMR resonance at δ −18.1 in (CD 2 Cl 2 ) (for details, see the Supporting Information). FLP Activation of Dihydrogen. The three phosphanes 1a−1c were each combined with B(C6F5)3 in an equimolar ratio to give the respective frustrated Lewis pairs. These were then subsequently reacted with dihydrogen. As a typical example, we dissolved the 1a/B(C6F5)3 Lewis pair in pentane and exposed the solution to a 2 bar hydrogen atmosphere at room temperature. After ca. 1 h, an oily precipitate began to appear. After 12 h stirring of the reaction mixture in pentane under hydrogen atmosphere, we collected the product 2a as a white precipitate in 77% yield (see Scheme 1).

Figure 1. Molecular structure of the [XPhosH+][HB(C6F5)3−] salt 2a.

The reaction of the tBuXPhos (1b)/B(C6F5)3 FLP with hydrogen was carried out analogously. It gave the [tBuXPhosH+][HB(C6F5)3−] salt in 65% yield. It was characterized by spectroscopy [NMR: δ31P 31.9 (1JPH ∼ 455 Hz); δ1H 5.58 (PH); δ11B −25.5 (d, 1JBH ∼ 93 Hz)]. The heterolytic splitting of dihydrogen was confirmed by carrying out the reaction of the 1b/B(C6F5)3 FLP with D2, which gave the isotopomer [tBuXPhosD+][DB(C6F5)3−] (2b-D2) (for its characterization, see the Supporting Information). Compound 2b was also characterized by an X-ray crystal structure analysis. It exhibits very similar structural features as the related [XPhosH+][HB(C6F5)3−] salt (2a). A view of the molecular structure of the salt [tBuXPhosH+][HB(C6F5)3−] (2b) is depicted in the Supporting Information, where also detailed structural parameters are listed. Ethyldimesitylphosphane (1c) gives a yellow solution when dissolved together with B(C6F5)3 in pentane. This solution reacts cleanly with H2 (2 bar) at room temperature. After 12 h of reaction time, a colorless oil of the salt [Mes2EtPH+][HB(C6F5)3−] (2c) was isolated in 80% yield (see Scheme 2). It shows the typical NMR features of the tris(pentafluorophenyl)hydridoborate anion (see above). The cation of 2c is characterized by typical 1H/31P NMR resonances at δ 7.53 (1H) and δ −7.5 (1JPH ∼ 473 Hz) (31P). It shows the 1H/13C

Scheme 1

The salt 2a shows the typical spectroscopic features of the hydroborate anion [NMR: δ 11B −25.4 (1JBH ∼ 93 Hz); δ1H 3.61 (broad 1:1:1:1 q, 1JBH ∼ 93 Hz, BH); δ19F −133.9 (o), −164.8 (p), −167.7 (m) (C6F5)] and of a phosphonium cation [NMR: δ31P 15.1 (1JPH ∼ 466 Hz); δ1H 5.52 (PH)]. The reaction was also carried out with D2. The corresponding 2802


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Scheme 2

NMR data of the P-bonded ethyl group [δ 2.87 (2H), 1.36 (3H)/δ 18.5 (1JPC = 45.6 Hz), 9.1 (2JPC = 4.1 Hz)] and the signals of the pair of mesityl substituents. FLP Addition Reaction to Ethene. The ethyldimesitylphosphane/tris(pentafluorophenyl)borane frustrated Lewis pair reacts readily with ethene. Stirring of a pentane solution of the FLP in an ethene atmosphere (2 bar) for a prolonged period of time (48 h) gave the 1,2-P/B-addition product 3c that was isolated in >50% yield after crystallization (see Scheme 3).

Figure 2. View of the molecular structure of the zwitterionic ethene P/ B addition product 3c.

Scheme 3

The zwitterion 3c was characterized by X-ray diffraction. The crystal structure analysis confirmed that 1,2-addition of the Mes2PEt and B(C6F5)3 components to ethene had occurred. The central B1−C4−C3−P1 unit (dihedral angle: −162.0(2)°) adopts a slightly distorted antiperiplanar alkane-like confirmation. On the boron side, the C41−C46 C6F5 ring stands in continuation of this “zig-zag”-shaped chain (C4−B1 1.662(4) Å, B1−C41 1.659(4) Å; angle C4−B1−C41 110.4(2)°; dihedral angle C41−B1−C4−C3 178.0(2)°) and so does the C21−C29 mesityl substituent at the distal phosphorus side (C3−C4 1.549(4) Å, C3−P1 1.822(3) Å, P1−C21 1.820(3) Å; angle C3−P1−C21 117.1(1)°; dihedral angle C4−C3−P1− C21 175.9(2)°). The ethyl substituent at phosphorus is oriented in a gauche arrangement relative to the central antiperiplanar chain (P1−C2 1.822(3) Å; dihedral angles C4− C3−P1−C2 −67.1(2)°, C3−P1−C2−C1 −68.9(2)°) (see Figure 2). The zwitterionic compound 3c shows typical borate type 11B (δ −13.1) and 19F [δ −133.1 (o), −162.8 (p), −166.3 (mC6F5); Δδ19Fp,m = 3.5] NMR signals and a phosphonium type 31 P NMR signal at δ 36.1. The newly introduced bridging ethylene unit shows NMR resonances at δ 2.51 (CH2P), 1.30 (CH2B) (1H), and δ 25.9 (1JPH = 38.0 Hz) and δ 15.5 (broad) (13C), respectively. The analogous reaction was also carried out with the frustrated Lewis pair derived from ethyldimesitylphosphane (1c) and the slightly modified EtB(C6F5)2 Lewis acid. The latter is readily available by ethene hydroboration with the HB(C6F5)2 reagent.18 The reaction of this modified FLP (in situ generation) with ethene was carried out under our typical reaction conditions (r.t., pentane) and gave the zwitterion 3d, isolated in ca. 40% yield (see Scheme 3). The X-ray crystal structure analysis of compound 3d shows an ethylene-bridged phosphonium/borate zwitterion (see Figure 3). The central unit shows a distorted antiperiplanar

Figure 3. Molecular structure of compound 3d.

arrangement of the bulky heteroatom-based substituents along the core −CH2−CH2− moiety (dihedral angle P1−C1−C2− B1 −155.8(2)°; bond lengths P1−C1 1.818(3) Å, C1−C2 1.533(4) Å, C2−B1 1.649(4) Å; bond angles P−C1−C2 110.8(2)°, C1−C2−B1 110.6(2)°), to which a boron-bonded C6F5 group and a phosphorus-bonded mesityl group are also antiperiplanarly connected (dihedral angles C41−B1−C2−C1 −176.6(2)°, C11−P1−C1−C2 −179.2(2)°). Both the ethyl groups at boron and phosphorus are arranged in gauche positions relative to the central unit (dihedral angles C1−C2− B1−C5 −58.1(3)°, C2−C1−P1−C3 −66.1(2)°), and they are oriented syn to each other at the framework. Compound 3d shows similar NMR features as 3c (see above) [δ −10.4 (11B), δ 35.5 (31P)] only that it exhibits the additional signals of the ethyl substituent at boron [1H NMR: δ 0.80 (CH2), 0.44 (CH3)]. We eventually also reacted the t BuXPhos/B(C 6 F 5 ) 3 frustrated Lewis pair with ethene. Under the usual reaction conditions (r.t., pentane), we obtained the 1,2-addition product 3b, which we isolated in 80% yield as a white solid (see Scheme 4). The X-ray crystal structure analysis showed an antiperiplanar orientation of the bulky phosphonium and borate groups at the central bridging ethylene unit (dihedral angle P1−C1− C2−B1 −168.6(2)°; P1−C1 1.841(3) Å, C2−B1 1.669(4) Å) (see Figure 4). The bulky o-triisopropylphenyl substituent at the phosphorus-bonded aryl substituent is found in a conformational orientation where it is π-facing the bridging ethylene unit. 2803


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Scheme 4

Scheme 5

NMR spectra were measured at 263 K to avoid decomposition. Compound 4a shows an IR carbonyl stretching band at ν̃(C O) = 1698 cm−1. The corresponding IR feature of the CO2 addition product 4c derived from the 1c/B(C6F5)3 FLP occurs at ν̃(CO) = 1644 cm−1. Compound 4c shows a characteristic 13C NMR carbonyl carbon signal at δ 162.5 (1JPC = 118.8 Hz) and heteroatom resonances at δ31P 16.3, δ11B −2.4, and δ19F −134.6 (o), −160.2 (p), and −165.7 (m), respectively. The 13C NMR signals of the single ethyl substituent at phosphorus occur at δ 22.6 (1JPC = 42.1 Hz) and δ 8.2 (2JPC = 5.1 Hz), respectively (all NMR spectra of compound 4c were measured at 253 K). Compound 4c was also characterized by an X-ray crystal structure analysis (single crystals were obtained from a solution of 4c in dichloromethane covered with heptane at −30 °C). The structure (see Figure 6) features the newly formed bond of phosphorus to the CO2 carbonyl carbon atom (P1−C1 1.894(3) Å, C1−O1 1.200(3) Å, C1−O2 1.304(3) Å; angle P1−C1−O1 121.5(2)°) and the newly formed boron−oxygen bond (B1−O2 1.554(3) Å; angle C1−O2−B1 120.5(2)°). The ethyl substituent at phosphorus is antioriented to the carbonyl oxygen in 4c (dihedral angle C2−P1−C1−O1 164.7(2)°).

Figure 4. View of the zwitterionic FLP addition product 3b.

In compound 3b, the [P]−CH2−CH2−[B] signals occur at δ 49.8 (31P), δ 21.0 (1JPC = 27.9 Hz), 18.4 (broad) (13C), and δ −14.1 (11B), respectively. FLP Reactions with Carbon Dioxide. We eventually reacted the FLPs XPhos(1a)/B(C6F5)3 and Mes2EtP(1c)/ B(C6F5)3, respectively, with carbon dioxide. The reaction of the 1a/B(C6F5)3 pair with CO2 was carried out in pentane solution that was covered with an atmosphere of carbon dioxide (2 bar, r.t.). The reaction was quick at room temperature, where a white precipitate started to appear after 20 min reaction time. The mixture was then cooled to −20 °C and stirred for another two hours. The solid CO2 addition product 4a was isolated in 80% yield (see Scheme 5). Single crystals of the CO2 adduct 4a suited for the X-ray crystal structure analysis were obtained from a solution of 4a in dichloromethane covered with heptane at −30 °C. The solidstate structure shows that the phosphorus atom of the FLP component 1a has added to the carbonyl carbon atom (P1−C1 1.866(3) Å; angles P1−C1−O1 116.3(2)°, P1−C1−O2 115.0(2)°, O1−C1−O2 128.6(3)°). The O1−C1 bond of the carbonyl groups is still short at 1.212(3) Å, whereas the adjacent C1−O2 linkage has become quite elongated by the addition reaction (C1−O2 1.296(3) Å). The oxygen atom O2 is found bonded to boron (O2−B1 1.554(4) Å; angle C1− O2−B1 118.5(2)°). The bulky o-triisopropylphenyl substituent in 4a is oriented facing a P-cyclohexyl group (see Figure 5). The 13C NMR spectrum of 4a shows the carbonyl resonance at δ 162.5 with a coupling constant to phosphorus of 1JPC = 116.0 Hz. The corresponding 31P NMR signal occurs at δ 26.8. Compound 4a shows a 11B NMR resonance at δ −2.7. The

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CONCLUSIONS

Our study indicates that the scope of the phosphorus Lewis base component of frustrated Lewis pairs can substantially be varied without losing the typical character of FLP chemistry with small molecules. The phosphanes employed here that are bearing combinations of bulky aryl and alkyl substituents all behaved as suitable Lewis base components in the combination with the Lewis acid B(C6F5)3 (and in one case, with EtB(C6F5)2). All the FLPs thus formed were able to activate dihydrogen by heterolytic cleavage of the strong H−H bond at ambient conditions. They reacted readily with ethene and also with carbon dioxide to give the corresponding zwitterionic 1,2addition products in high yield. This shows us that the scope of FLP components can probably be varied to quite some extent, including many commercially available bulky phosphanes, such as XPhos or tBuXPhos, that were actually developed for other (catalytic) purposes than their utilization in FLP chemistry. This indicates that FLP chemistry can probably be substantially expanded with regard to utilization of readily available components, especially Lewis base components. 2804


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Figure 5. Projection of the molecular structure of the FLP-CO2 adduct 4a. (BrukerAXS, 2000). Graphics show the thermal ellipsoids with 50% probability; R values are given for the observed reflections, wR2 values for all reflections. Materials. XPhos17 and tBuXPhos17 were ordered from SigmaAldrich and used without further purification. Ethyldichlorophosphane was ordered from Acros Organics and used without any purification. Bis(pentafluorophenyl)borane18 and tris(pentafluorophenyl)borane1 were prepared according to modified literature procedures. Preparation of Compound 1c. In a 250 mL Schlenk flask, bromomesitylene (11.94 g, 60 mmol, 9.2 mL, 2 equiv) was dissolved in tetrahydrofuran (100 mL). The solution was cooled to −78 °C, and within 30 min, n-butyl lithium (1.6 M, 41 mL, 65.0 mmol, 2.1 equiv) was added with a syringe. The solution was stirred for 1 h at −78 °C. Afterward, ethyldichlorophosphane (3.93 g, 30 mmol, 3.11 mL, 1 equiv) dissolved in tetrahydrofuran (20 mL) was added. The reaction mixture was allowed to warm to room temperature and was then stirred for 4 h. The solvent was removed in vacuo, and the residue was dissolved in dichloromethane (100 mL). After filtration, the solvent was removed in vacuo. The residue was washed with pentane. After filtration and evaporation of the solvent, the product was obtained in 78% (6.98 g, 23.4 mmol) yield. Anal. Calcd for C20H27P (298.40 g/ mol): C, 80.50; H, 9.12. Found: C, 80.38; H, 9.02. mp: 119.1 °C. 1H NMR (500 MHz, CD2Cl2, 298 K): δ = 6.78 (dm, 4JPH = 2.6 Hz, 4H, m-Mes), 2.48 (qd, 3JHH = 7.5 Hz, 2JPH = 2.4 Hz, 2H, PEtCH2), 2.27 (s, 12H, o-Me), 2.22 (s, 6H, p-Me), 0.95 (dt, 3JPH = 18.6 Hz, 3JHH = 7.5 Hz, 3H, PEtCH3). 13C{1H} NMR (126 MHz, CD2Cl2, 298 K): δ = 142.3 (d, 2JPC= 13.3 Hz, o-Mes), 137.7 (p-Mes), 133.7 (d, 1JPC = 22.8 Hz, i-Mes), 130.1 (d, 3JPC = 2.8 Hz, m-Mes), 23.2 (d, 3JPC = 13.5 Hz, oMe), 21.0 (d, 1JPC = 14.3 Hz, PEtCH2), 20.9 (p-Me), 11.5 (d, 2JPC = 21.0 Hz, PEtCH3). 31P{1H} NMR (202 MHz, CD2Cl2, 298 K): δ = −18.1 (ν1/2 ≈ 2 Hz). Preparation of Compound 2a. In a 10 mL Schlenk flask, XPhos (50.0 mg, 105 μmol, 1 equiv) and tris(pentafluorophenyl)borane (53.7 mg, 105 μmol, 1 equiv) were dissolved in pentane (3 mL). The solution was stirred for 10 min. The Schlenk flask was then evacuated, and dihydrogen gas (2 bar) was added. After 1 h, an oily residue was obtained. The solution was stirred for 12 h at room temperature, and a white solid precipitated. The solution was removed and the residue dried in vacuo. The product was obtained as a white solid in 77% (80.0 mg, 81.1 μmol) yield. Crystals suitable for X-ray crystal structure analysis were obtained from a solution of 2a in dichloromethane covered with heptane at −30 °C. Anal. Calcd for C51H51BF15P (M = 990.71 g/mol): C, 61.83; H, 5.19. Found: C, 61.22; H, 5.01. mp: 136.4 °C. 1H NMR (500 MHz, CD2Cl2, 298 K): δ = 7.87 (m, 1H, 4-H), 7.69 (m, 1H, 3-H), 7.68 (m, 1H, 2-H), 7.59 (m, 1H, 5-H), 7.18 (s, 2H, mtipp), 5.52 (dt, 1JPH = 465.1 Hz, 3JHH = 5.6 Hz, 1H, PH), 3.61 (1:1:1:1 q {partial relaxed}, 1JBH ∼ 93 Hz, 1H, BH), 2.98 (sept, 3JHH = 6.8 Hz,

Figure 6. Molecular structure of 4c.

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EXPERIMENTAL SECTION

General Information. All reactions were carried out under an argon atmosphere with Schlenk-type glassware or in a glovebox. Solvents (including deuterated solvents used for NMR spectroscopy) were dried and distilled under argon prior to use. The following instruments were used for physical characterization of the compounds. Elemental analyses: Foss-Heraeus CHNO-Rapid. NMR: Bruker AC 200 P (1H, 200 MHz), Varian 500 MHz INOVA (1H, 500 MHz; 13C, 126 MHz), Varian UNITY plus NMR spectrometer (1H, 600 MHz; 13 C, 151 MHz). Assignments of the resonances are supported by 2D experiments. Melting points/decomposition temperature: DSC 2010 (TA-Instruments) apparatus, determined by the baseline method. IR: Varian 3100 FT-IR (ExcaliburSeries) spectrometer. X-ray diffraction: data sets were collected with a Nonius KappaCCD diffractometer. Programs used: data collection, COLLECT (Nonius B.V., 1998); data reduction, Denzo-SMN (Otwinowski, Z.; Minor,W. Methods Enzymol. 1997, 276, 307−326); absorption correction, Denzo (Otwinowski, Z.; Borek, D.; Majewski, W.; Minor, W. Acta Crystallogr. 2003, A59, 228− 234); structure solution, SHELXS-97 (Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467−473); structure refinement, SHELXL-97 (Sheldrick, G. M. Universität Gö ttingen, 1997); graphics, XP 2805


Organometallics

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1H, p-iPrCH), 2.44, 1.98/1.40, 1.90/1.35, 1.86/1.28, 1.77/1.21, 1.75/ 1.32 (each br, each 2H, Cy), 2.19 (sept, 3JHH = 6.8 Hz, 2H, o-iPrCH), 1.30 (d, 3JHH = 6.8 Hz, 6H, p-iPrCH3), 1.26 (3JHH = 6.8 Hz), 1.01 (3JHH = 6.8 Hz) (each d, each 6H, o-iPrCH3). 13C{1H} NMR (126 MHz, CD2Cl2, 298 K): δ = 152.2 (p-tipp), 148.8 (dm, 1JFC ∼ 238 Hz, oC6F5), 146.9 (d, 2JPC = 7.0 Hz, C-6), 146.7 (o-tipp), 139.1 (dm, 1JFC ∼ 238 Hz, p-C6F5), 136.4 (dm, 1JFC ∼ 245 Hz, m-C6F5), 135.3 (d, 4JPC = 2.7 Hz, C-4), 134.2 (d, 3JPC = 9.0 Hz, C-5), 132.9 (d, 2JPC = 10.5 Hz, C-2), 131.1 (d, 3JPC = 5.4 Hz, i-tipp), 129.4 (d, 3JPC = 11.9 Hz, C-3), 122.3 (m-tipp), 113.5 (d, 1JPC = 80.5 Hz, C-1), 34.8 (p-iPrCH), 31.29 (o-iPrCH), 31.25 (d, 1JPC = 40.6 Hz), 28.6 (d, 2JPC = 3.8 Hz), 27.5 (d, 2 JPC = 3.1 Hz), 26.4 (d, 3JPC = 13.7 Hz), 26.2 (d, 3JPC = 13.8 Hz), 25.1 (d, 4JPC = 1.6 Hz) (Cy), 26.3, 22.5 (o-iPrCH3), 24.0 (p-iPrCH3). 31P{1H} NMR (202 MHz, CD2Cl2, 298 K): δ = 15.1 (ν1/2 ≈ 2 Hz). 31P NMR (202 MHz, CD2Cl2, 298 K): δ = 15.1 (br d, 1JPH ∼ 466 Hz). 19F NMR (470 MHz, CD2Cl2, 298 K): δ = −133.9 (m, 2F, o-C6F5), −164.8 (t, 3 JFF = 20.4 Hz, 1F, p-C6F5), −167.7 (m, 2F, m-C6F5), [Δδ19Fp,m = 2.9]. 11 1 B{ H} NMR (160 MHz, CD2Cl2, 298 K): δ = −25.4 (ν1/2 ∼ 40 Hz). 11 B NMR (160 MHz, CD2Cl2, 298 K): δ = −25.4 (d, 1JBH ∼ 93 Hz). X-ray Crystal Structure Analysis of 2a. Formula C51H51BF15P, M = 990.70; colorless crystal, 0.20 × 0.12 × 0.12 mm; a = 12.6283(5) Å, b = 13.1720(5) Å, c = 16.6906(8) Å, α = 71.304(2)°, β = 70.488(2) °, γ = 70.734(2)°; V = 2400.31(17) Å3; ρcalc = 1.371 g cm−3; μ = 1.334 mm−1; empirical absorption correction (0.776 ≤ T ≤ 0.856); Z = 2; triclinic, space group P1 bar (No. 2); λ = 1.54178 Å; T = 223 K; ω and φ scans, 30 346 reflections collected (±h, ± k, ± l), [(sinθ)/λ] = 0.60 Å−1, 8313 independent (Rint = 0.065) and 6216 observed reflections [I ≥ 2σ(I)]; 625 refined parameters, R = 0.054, wR2 = 0.137; max. residual electron density 0.20 (−0.27) e Å−3; hydrogen atoms at P and B from difference Fourier map, the others calculated and refined as riding atoms. Preparation of Compound 2a-D2. In a 10 mL Schlenk flask, XPhos (50.0 mg, 105 μmol, 1 equiv) and tris(pentafluorophenyl)borane (53.7 mg, 105 μmol, 1 equiv) were dissolved in pentane (3 mL). The solution was stirred for 10 min. The Schlenk flask was then evacuated, and deuterium gas (2 bar) was added. After 1 h, an oily residue was obtained. The solution was stirred for 12 h at room temperature, and a white solid precipitated. The solution was removed and the residue dried in vacuo. The product was obtained as a white solid in 68% (70.8 mg, 71.4 μmol) yield. 1H NMR (500 MHz, CD2Cl2, 298 K): δ = 7.87 (m, 1H, 4-H), 7.69 (m, 1H, 3-H), 7.68 (m, 1H, 2-H), 7.59 (m, 1H, 5-H), 7.18 (s, 2H, m-tipp), 2.97 (sept, 3JHH = 7.1 Hz, 1H, p-iPrCH), 2.43, 1.98/1.40, 1.90/1.35, 1.86/1.28, 1.77/1.21, 1.75/1.32 (each m, each 2H, Cy), 2.19 (sept, 3JHH = 6.8 Hz, 2H, o-iPrCH), 1.30 (d, 3JHH = 6.8 Hz, 6H, p-iPrCH3), 1.26 (3JHH = 6.8 Hz), 1.01 (3JHH = 6.8 Hz) (each d, each 6H, o-iPrCH3), [ca. 17% PH: δ = 5.52 (dt, 1JPH = 465.1 Hz, 3JHH = 5.6 Hz, PH)]. 2H NMR (77 MHz, CH2Cl2, 298 K): δ = 5.48 (d, 1JPD = 71.3 Hz, 1D, PD), 3.63 (br, 1D, BD). 31P{1H} NMR (202 MHz, CD2Cl2, 298 K): δ = 15.1 (PH), 14.4 (1:1:1 t, 1JPD ∼ 71 Hz, PD). 31P NMR (202 MHz, CD2Cl2, 298 K): δ = 15.1 (ca. 14%, br d, 1JPH ∼ 470 Hz, PH), 14.4 (ca. 86%, 1:1:1 t, 1JPD ∼ 71 Hz, PD). 11 1 B{ H} NMR (160 MHz, CD2Cl2, 298 K): δ = −25.6 (ν1/2 ∼ 70 Hz). 11 B NMR (160 MHz, CD2Cl2, 298 K): δ = −25.6 (ν1/2 ∼ 70 Hz). Preparation of Compound 2b. In a 10 mL Schlenk flask, t BuXPhos (50.0 mg, 118 μmol, 1 equiv) and tris(pentafluorophenyl)borane (60.3 mg, 118 μmol, 1 equiv) were dissolved in pentane (3 mL). The solution was stirred for 10 min. The Schlenk flask was then evacuated, and dihydrogen gas (2 bar) was added. After 1 h, an oily residue was obtained. The solution was stirred for 12 h at room temperature, and a white solid precipitated. The solution was removed, and the residue was dried in vacuo. The product was obtained as a white solid in 65% (72.0 mg, 76.7 μmol) yield. Crystals suitable for Xray crystal structure analysis were obtained from a solution of 2b in dichloromethane covered with heptane at −30 °C. Anal. Calcd for C47H47BF15P (M = 938.64 g/mol): C, 60.14; H, 5.05. Found: C, 59.81; H, 4.77. mp: 127.1 °C. 1H NMR (500 MHz, CD2Cl2, 298 K): δ = 7.88 (m, 1H, 4-H), 7.78 (m, 1H, 2-H), 7.72 (m, 1H, 3-H), 7.64 (m, 1H, 5-H), 7.17 (s, 2H, m-tipp), 5.58 (d, 1JPH = 453.4 Hz, 1H, PH), 3.59 (1:1:1:1 q {partial relaxed}, 1JBH ∼ 90 Hz, 1H, BH), 2.96 (sept,

JHH = 6.9 Hz, 1H, p-iPrCH), 2.26 (sept, 3JHH = 6.8 Hz, 2H, o-iPrCH), 1.44 (d, 3JPH = 17.4 Hz, 18H, tBu), 1.30 (d, 3JHH = 6.9 Hz, 6H, p-iPrCH3), 1.23, 1.00 (each d, each 3JHH = 6.8 Hz, each 6H, o-iPrCH3). 13 C{1H} NMR (126 MHz, CD2Cl2, 298 K): δ = 152.0 (p-tipp), 148.6 (dm, 1JFC ∼ 235 Hz, o-C6F5), 147.5 (d, 2JPC = 5.1 Hz, C-6), 147.0 (otipp), 138.0 (dm, 1JFC ∼ 242 Hz, p-C6F5), 136.9 (dm, 1JFC ∼ 245 Hz, m-C6F5), 135.3 (d, 3JPC = 9.1 Hz, C-5), 135.1 (d, 4JPC = 3.0 Hz, C-4), 133.4 (d, 2JPC = 9.9 Hz, C-2), 131.1 (d, 3JPC = 4.2 Hz, i-tipp), 129.0 (d, 3 JPC = 11.8 Hz, C-3), 125.7 (i-C6F5), 122.3 (m-tipp), 114.8 (d, 1JPC = 71.2 Hz, C-1), 35.8 (d, 1JPC = 33.1 Hz, tBu), 34.7 (p-iPrCH), 31.5 (o-iPrCH), 28.6 (d, 2JPC = 1.2 Hz, tBu), 26.8, 22.3 (o-iPrCH3), 24.0 (p-iPrCH3). 31P{1H} NMR (202 MHz, CD2Cl2, 298 K): δ = 31.9 (ν1/2 ≈ 2 Hz). 31P NMR (202 MHz, CD2Cl2, 298 K): δ = 31.9 (dm, 1JPH ∼ 455 Hz). 19F NMR (470 MHz, CD2Cl2, 298 K): δ = −133.9 (m, 2F, oC6F5), −164.8 (t, 3JFF = 20.1 Hz, 1F, p-C6F5), −167.7 (m, 2F, mC6F5), [Δδ19Fp,m = 2.9]. 11B{1H} NMR (160 MHz, CD2Cl2, 298 K): δ = −25.5 (ν1/2 ∼ 40 Hz). 11B NMR (160 MHz, CD2Cl2, 298 K): δ = −25.5 (d, 1JBH ∼ 93 Hz). X-ray Crystal Structure Analysis of 2b. Formula, C47H47BF15P * C4H8O, M = 1010.73; colorless crystal, 0.30 × 0.23 × 0.17 mm; a = 11.2833(3) Å, b = 12.7521(4) Å, c = 18.8957(14) Å, α = 97.043(2)°, β = 101.311(4)°, γ = 111.568(2)°; V = 2422.2(2) Å3; ρcalc = 1.386 g cm−3; μ = 1.347 mm−1; empirical absorption correction (0.688 ≤ T ≤ 0.803); Z = 2; triclinic, space group P1 bar (No. 2); λ = 1.54178 Å; T = 223 K; ω and φ scans, 35 859 reflections collected (±h, ± k, ± l), [(sinθ)/λ] = 0.60 Å−1, 8362 independent (Rint = 0.049) and 6877 observed reflections [I ≥ 2σ(I)]; 640 refined parameters, R = 0.059, wR2 = 0.168; max. residual electron density 0.48 (−0.51) e Å−3; hydrogen atoms at P and B from difference Fourier map, the others calculated and refined as riding atoms. Preparation of Compound 2b-D2. In a 10 mL Schlenk flask, t BuXPhos (50.0 mg, 118 μmol, 1 equiv) and tris(pentafluorophenyl)borane (60.3 mg, 118 μmol, 1 equiv) were dissolved in pentane (3 mL). The solution was stirred for 10 min. Then Schlenk flask was then evacuated, and deuterium gas (2 bar) was added. After 1 h, an oily residue was obtained. The solution was stirred for 12 h at room temperature, and a white solid precipitated. The solution was removed, and the residue was dried in vacuo. The product was obtained as a white solid in 45% (49.9 mg, 53.1 μmol) yield. 1H NMR (500 MHz, CD2Cl2, 298 K): δ = 7.88 (m, 1H, 4-H), 7.78 (m, 1H, 2-H), 7.72 (m, 1H, 3-H), 7.64 (m, 1H, 5-H), 7.17 (s, 2H, m-tipp), 5.58 (d, 1JPH = 453.4 Hz, 1H, PH), 2.96 (sept, 3JHH = 6.8 Hz, 1H, p-iPrCH), 2.26 (sept, 3 JHH = 6.7 Hz, 2H, o-iPrCH), 1.44 (d, 3JPH = 17.4 Hz, 18H, tBu), 1.30 (d, 3JHH = 6.8 Hz, 6H, p-iPrCH3), 1.24, 1.00 (each d, each 3JHH = 6.7 Hz, each 6H, o-iPrCH3), [ca. 45% PH: δ = 5.58 (d, 1JPH = 453.4 Hz, PH)]. 2 H NMR (77 MHz, CH2Cl2, 298 K): δ = 5.58 (d, 1JPD = 69.7 Hz, 1D, PD), 3.56 (br, 1.5D, BD). 31P{1H} NMR (202 MHz, CD2Cl2, 298 K): δ = 31.9 (ca. 50%, PH), 31.1 (ca. 50%, 1:1:1 t, 1JPD ∼ 69 Hz, PD). 31P NMR (202 MHz, CD2Cl2, 298 K): δ = 31.9 (br d, 1JPH ∼ 450 Hz, PH), 31.1 (br, PD). 11B{1H} NMR (160 MHz, CD2Cl2, 298 K): δ = −25.6 (ν1/2 ∼ 60 Hz). 11B NMR (160 MHz, CD2Cl2, 298 K): δ = −25.6 (ν1/2 ∼ 60 Hz). Preparation of Compound 2c. In a 10 mL Schlenk flask, ethyldimesitylphosphane (48.1 mg, 162 μmol, 1 equiv) and tris(pentafluorophenyl)borane (83.0 mg, 162 μmol, 1 equiv) were dissolved in pentane (3 mL). The yellow solution was stirred for 10 min. The Schlenk flask was then evacuated, and dihydrogen gas (2 bar) was added. After 1 h, an oily residue was obtained. The solution was stirred for 12 h at room temperature. After evaporation of the solvent in vacuo, the product was obtained as a colorless oil in 80% (105.3 mg, 129.6 μmol) yield. Anal. Calcd for C38H29BF15P (M = 812.40 g/mol): C, 56.18; H, 3.60. Found: C, 56.00; H, 3.78. 1H NMR (500 MHz, CD2Cl2, 233 K): δ = 7.53 (dt, 1JPH = 473.1 Hz, 3JHH = 7.1 Hz, 1H, PH), 7.05 (m, 4H, m-Mes), 3.54 (br q {partial relaxed}, 1H, BH), 2.87 (m, 2H, PEtCH2), 2.38 (s, 12H, o-Me), 2.31 (s, 6H, p-Me), 1.36 (dt, 3JPH = 23.6 Hz, 3JHH = 7.2 Hz, 3H, PEtCH3). 13C{1H} NMR (126 MHz, CD2Cl2, 233 K): δ = 147.9 (dm, 1JFC = 236 Hz, o-C6F5), 146.6 (p-Mes), 143.1 (d, 4JPC = 10.4 Hz, o-Mes), 137.5 (dm, 1JFC ∼ 245 Hz, p-C6F5), 136.3 (dm, 1JFC ∼ 247 Hz, m-C6F5), 132.0 (d, 3JPC = 3

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Organometallics

Article

11.1 Hz, m-Mes), 124.5 (i-C6F5), 109.9 (d, 1JPC = 81.4 Hz, i-Mes), 22.0 (d, 3JPC = 7.8 Hz, o-Me), 21.1 (p-Me), 18.5 (d, 1JPC = 45.6 Hz, P CH2 Et ), 9.1 (d, 2JPC = 4.1 Hz, PEtCH3). 31P{1H} NMR (202 MHz, CD2Cl2, 233 K): δ = −7.5 (ν1/2 ≈ 5 Hz), [−19.3, tentatively assigned as 1c]. 31P NMR (202 MHz, CD2Cl2, 233 K): δ = −7.5 (ca. 83%, dm, 1 JPH ∼ 473 Hz), [−19.3 (ca. 17%, tentatively assigned as 1c]. 19F NMR (470 MHz, CD2Cl2, 233 K): δ = −134.0 (m, 2F, o-C6F5), −163.7 (m, 1F, p-C6F5), −166.8 (m, 2F, m-C6F5), [Δδ19Fp,m = 3.1]. 11B{1H} NMR (160 MHz, CD2Cl2, 233 K): δ = −25.5 (ν1/2 ∼ 95 Hz). 11B NMR (160 MHz, CD2Cl2, 233 K): δ = −25.5 (d, 1JBH ∼ 82 Hz). Preparation of Compound 2c-D2. In a 10 mL Schlenk flask, ethyldimesitylphosphane (48.1 mg, 162 μmol, 1 equiv) and tris(pentafluorophenyl)borane (83.0 mg, 162 μmol, 1 equiv) were dissolved in pentane (3 mL). The yellow solution was stirred for 10 min. The Schlenk flask was then evacuated, and deuterium gas (2 bar) was added. After 1 h, an oily residue was obtained. The solution was stirred for 12 h at room temperature. After evaporation of the solution in vacuo, the product was obtained as a colorless oil in 90% (118.7 mg, 145.8 μmol) yield. 1H NMR (500 MHz, CD2Cl2, 298 K): δ = 7.10 (m, 4H, m-Mes), 2.89 (m, 2H, PEtCH2), 2.41 (s, 12H, o-Me), 2.35 (s, 6H, pMe), 1.41 (dt, 3JPH = 23.6 Hz, 3JHH = 7.3 Hz, 3H, PEtCH3), [ca. 10% PH: δ = 5.57 (d, 1JPH ∼ 472 Hz, PH)]. 2H NMR (77 MHz, CH2Cl2, 298 K): δ = 7.60 (d, 1JPD = 72.2 Hz, 1D, PD), 3.61 (br, 1D, BD). 31 1 P{ H} NMR (202 MHz, CD2Cl2, 298 K): δ = −7.3 (11%, PH), −7.8 (89%, 1:1:1 t, 1JPD = 72.3 Hz, PD). 31P NMR (202 MHz, CD2Cl2, 298 K): δ = −7.3 (br d, PH), −7.8 (br 1:1:1 t, PD). 11B{1H} NMR (160 MHz, CD2Cl2, 298 K): δ = −25.6 (ν1/2 ∼ 60 Hz). 11B NMR (160 MHz, CD2Cl2, 298 K): δ = −25.6 (ν1/2 ∼ 60 Hz). Preparation of Compound 3b. In a 10 mL Schlenk flask, t BuXPhos (50.0 mg, 118 μmol, 1 equiv) and tris(pentafluorophenyl)borane (60.3 mg, 118 μmol, 1 equiv) were dissolved in pentane (3 mL). The solution was stirred for 10 min. The Schlenk flask was then evacuated, and ethene gas (2 bar) was added to the solution. The solution was stirred for 48 h at room temperature. The obtained white precipitated was collected and dried in vacuo. After fractional crystallization with dichloromethane and pentane, the product was obtained as a white solid in 80% (91.1 mg, 94.4 μmol) yield. Crystals suitable for X-ray crystal structure analysis were obtained from a solution of 3b in dichloromethane covered with heptane at −30 °C. Anal. Calcd for C49H49BF15P (M = 964.67 g/mol): C, 61.01; H, 5.12. Found: C, 60.07; H, 5.43. mp: 253.8 °C. 1H NMR (600 MHz, CD2Cl2, 298 K): δ = 7.93 (m, 1H, 2-H), 7.63 (m, 1H, 4-H), 7.54 (m, 1H, 3-H), 7.25 (m, 1H, 5-H), 7.00 (s, 2H, m-tipp), 2.58 (sept, 3JHH = 7.0 Hz, 1H, p-iPrCH), 2.25 (sept, 3JHH = 6.9 Hz, 2H, o-iPrCH), 1.81 (m, 4H, PCH2, BCH2), 1.51 (d, 3JPH = 14.8 Hz, 18H, tBu), 1.10, 0.87 (each d, each 3 JHH = 6.7 Hz, each 6H, o-iPrCH3), 1.03 (d, 3JHH = 6.9 Hz, 6H, p-iPrCH3), [ca. 15% tBuXPhosH: δ = 5.59 (d, 1JPH = 454.2 Hz, PH), 2.97 (sept, 3JHH = 7.0 Hz, 1H, p-iPrCH)]. 13C{1H} NMR (151 MHz, CD2Cl2, 298 K): δ = 150.4 (p-tipp), 148.5 (dm, 1JFC ∼ 239 Hz, oC6F5), 147.8 (d, 2JPC = 4.8 Hz, C-6), 145.6 (o-tipp), 138.5 (dm, 1JFC ∼ 245 Hz, p-C6F5), 136.8 (dm, 1JFC ∼ 238 Hz, m-C6F5), 136.7 (d, 3JPC = 10.6 Hz, C-5), 135.9 (d, 2JPC = 7.8 Hz, C-2), 134.1 (i-tipp), 132.5 (C4), 126.4 (d, 3JPC = 10.3 Hz, C-3), 125.0 (i-C6F5), 122.0 (m-tipp), 120.4 (d, 1JPC = 58.3 Hz, C-1), 39.4 (d, 1JPC = 32.8 Hz, tBu), 33.8 (p-iPrCH), 31.3 (o-iPrCH), 29.5 (tBu), 26.6, 21.4 (o-iPrCH3), 23.2 (p-iPrCH3), 21.0 (d, 1JPC = 27.9 Hz, PCH2), 18.4 (br, BCH2). 31P{1H} NMR (243 MHz, CD2Cl2, 298 K): δ = 49.8 (ca. 82%, ν1/2 ∼ 60 Hz), [31.8 (ca. 18%, tentatively assigned as tBuXPhosH+]. 19F NMR (564 MHz, CD2Cl2, 298 K): δ = −131.2 (m, 2F, o-C6F5), −163.5 (t, 3JFF = 20.0 Hz, 1F, p-C6F5), −166.3 (m, 2F, m-C6F5), [Δδ19Fp,m = 2.8]. 11 1 B{ H} NMR (192 MHz, CD2Cl2, 298 K): δ = −14.1 (ν1/2 ∼ 70 Hz). X-ray Crystal Structure Analysis of 3b. Formula C49H49BF15P, M = 964.66; colorless crystal, 0.35 × 0.25 × 0.20 mm; a = 12.0517(3) Å, b = 16.2929(5) Å, c = 23.8126(7) Å; V = 4675.8(2) Å3; ρcalc = 1.370 g cm−3; μ = 1.354 mm−1; empirical absorption correction (0.649 ≤ T ≤ 0.773); Z = 4; orthorhombic, space group P212121 (No. 19); λ = 1.54178 Å; T = 223 K; ω and φ scans, 44 201 reflections collected (±h, ± k, ± l), [(sinθ)/λ] = 0.60 Å−1, 8188 independent (Rint = 0.057) and 7981 observed reflections [I ≥ 2σ(I)]; 607 refined parameters, R

= 0.049, wR2 = 0.141, Flack parameter 0.06(3); max. residual electron density 0.28 (−0.16) e Å−3; hydrogen atoms calculated and refined as riding atoms. Preparation of Compound 3c. In a 10 mL Schlenk flask, ethyldimesitylphosphane (50.0 mg, 168 μmol, 1 equiv) and tris(pentafluorophenyl)borane (85.6 mg, 168 μmol, 1 equiv) were dissolved in pentane (3 mL). The solution was stirred for 10 min. The Schlenk flask was then evacuated, and ethene gas (2 bar) was added. A white solid precipitated during the reaction time of 48 h at room temperature. The solution was removed, and the residue was dried in vacuo. After fractional crystallization with dichloromethane and pentane, the product was obtained as a white solid in 52% (73.2 mg, 87.4 μmol) yield. Crystals suitable for X-ray crystal structure analysis were obtained from a solution of 3c in dichloromethane covered with heptane at −30°. Anal. Calcd for C40H31BF15P (M = 838.43 g/mol): C, 57.30; H, 3.73. Found: C, 56.72; H, 3.75. mp: 257.6 °C. 1H NMR (500 MHz, CD2Cl2, 288 K): δ = 6.94 (m, 4H, m-Mes), 2.88 (m, 2H, PEtCH2), 2.51 (m, 2H, PCH2), 2.30 (s, 6H, p-Me), 2.12 (br s, 12H, o-Me), 1.30 (br m, 2H, BCH2), 1.10 (dt, 3JPH = 20.7 Hz, 3 JHH = 7.5 Hz, 3H, PEtCH3). 13C{1H} NMR (126 MHz, CD2Cl2, 288 K): δ = 148.4 (dm, 1JFC ∼ 240 Hz, o-C6F5), 144.6 (d, 4JPC = 2.9 Hz, pMes), 142.1 (d, 2JPC = 9.1 Hz, o-Mes), 138.2 (dm, 1JFC ∼ 245 Hz, pC6F5), 136.9 (dm, 1JFC ∼ 243 Hz, m-C6F5), 132.8 (d, 3JPC = 11.2 Hz, m-Mes), 125.3 (i-C6F5), 117.9 (d, 1JPC = 75.4 Hz, i-Mes), 25.9 (d, 1JPH = 38.0 Hz, PCH2), 23.5 (br, o-Me), 21.0 (d, 5JPC = 1.5 Hz, p-Me), 20.5 (d, 1JPC = 48.7 Hz, PEtCH2), 15.5 (br, BCH2), 7.2 (d, 2JPC = 3.6 Hz, P CH3 31 1 Et ). P{ H} NMR (202 MHz, CD2Cl2, 288 K): δ = 36.1 (ν1/2 ∼ 80 Hz). 19F NMR (470 MHz, CD2Cl2, 288 K): δ = −133.1 (m, 2F, oC6F5), −162.8 (t, 3JFF = 20.5 Hz, 1F, p-C6F5), −166.3 (m, 2F, mC6F5), [Δδ19Fp,m = 3.5]. 11B{1H} NMR (160 MHz, CD2Cl2, 288 K): δ = −13.1 (ν1/2 ∼ 50 Hz). X-ray Crystal Structure Analysis of 3c. Formula C40H31BF15P, M = 838.43; colorless crystal, 0.12 × 0.07 × 0.05 mm; a = 11.1241(6) Å, b = 12.3049(7) Å, c = 15.8458(9) Å, α = 104.190(5)°, β = 100.058(4)°, γ = 113.002(6)°; V = 1844.6(2) Å3; ρcalc = 1.510 g cm−3; μ = 1.627 mm−1; empirical absorption correction (0.829 ≤ T ≤ 0.923); Z = 2; triclinic, space group P1 bar (No. 2); λ = 1.54178 Å; T = 223 K; ω and φ scans, 21 460 reflections collected (±h, ± k, ± l), [(sinθ)/λ] = 0.60 Å−1, 6362 independent (Rint = 0.050) and 4973 observed reflections [I ≥ 2σ(I)]; 521 refined parameters, R = 0.049, wR2 = 0.128; max. residual electron density 0.28 (−0.32) e Å−3; hydrogen atoms calculated and refined as riding atoms. Preparation of Compound 3d. In a 10 mL Schlenk flask, ethyldimesitylphosphane (74.0 mg, 290 μmol, 1 equiv) and bis(pentafluorophenyl)borane (100.0 mg, 290 μmol, 1 equiv) were combined in pentane (3 mL). The suspension was stirred for 10 min. The Schlenk flask was then evacuated, and ethene gas (2 bar) was added. Within 3 min, the suspension turned into a clear solution; after an additional 35 min, a white solid precipitated. The reaction mixture was stirred for 48 h at room temperature. The solution was then removed and the residue dried in vacuo. After fractional crystallization with dichloromethane and pentane, the product was obtained as a white solid in 42% (89.4 mg, 127.6 μmol) yield. Crystals suitable for X-ray crystal structure analysis were obtained from a solution of 3d in dichloromethane covered with heptane at −30 °C. Anal. Calcd for C36H36BF10P (M = 700.43 g/mol): C, 61.73; H, 5.18. Found: C, 61.42; H, 5.37. mp: 193.9 °C. 1H NMR (600 MHz, CD2Cl2, 298 K): δ = 6.94 (d, 4JHH = 4.0 Hz, 4H, m-Mes), 2.86 (dq, 3JPH = 11.8 Hz, 3JHH = 7.4 Hz, 2H, PEtCH2), 2.49 (m, 2H, PCH2), 2.30 (s, 6H, p-Me), 2.20 (br s, 12H, o-Me), 1.03 (dt, 3JPH = 20.4 Hz, 3JHH = 7.4 Hz, 3H, PEtCH3), 1.01 (br, 2H, BCH2), 0.80 (q, 3JHH = 7.3 Hz, 2H, BEtCH2), 0.44 (t, 3JHH = 7.8 Hz, 3H, BEtCH3). 13C{1H} NMR (151 MHz, CD2Cl2, 298 K): δ = 148.3 (dm, 1JFC ∼ 234 Hz, o-C6F5), 144.4 (d, 4JPC = 2.9 Hz, p-Mes), 142.2 (d, 2JPC = 9.2 Hz, o-Mes), 137.5 (dm, 1JFC ∼ 245 Hz, p-C6F5), 136.7 (dm, 1JFC ∼ 245 Hz, m-C6F5), 132.7 (d, 3JPC = 11.2 Hz, m-Mes), 129.5 (i-C6F5), 118.6 (d, 1JPC = 74.6 Hz, i-Mes), 26.1 (d, 1JPH = 36.1 Hz, PCH2), 23.6 (br, o-Me), 21.1 (p-Me), 20.5 (d, 1JPC = 49.8 Hz, P CH2 Et ), 15.4 (br, BCH2)t, 14.3 (br, BEtCH2)t, 10.9 (BEtCH3), 7.3 (d, 2JPC = 3.2 Hz, PEtCH3), [ttentative assignment]. 31P{1H} NMR (243 MHz, CD2Cl2, 298 K): δ = 35.5 (ν1/2 ∼ 40 Hz). 19F NMR (564 MHz, 2807


Organometallics

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Found: C, 55.51; H, 3.88. Decomp.: 175.8 °C. 1H NMR (500 MHz, CD2Cl2, 253 K): δ = 6.98 (d, 4JHH = 4.5 Hz, 4H, m-Mes), 3.12 (m, 2H, P CH2 Et ), 2.31 (s, 6H, p-Me), 2.14 (s, 12H, o-Me), 1.17 (dt, 2JPH = 21.5 Hz, 3JHH = 7.4 Hz, 3H, PEtCH3). 13C{1H} NMR (126 MHz, CD2Cl2, 253 K): δ = 162.5 (d, 1JPC = 118.8 Hz, PCO2), 147.2 (dm, 1JFC ∼ 240 Hz, o-C6F5), 145.1 (d, 4JPC = 3.0 Hz, p-Mes), 142.7 (d, 2JPC = 9.5 Hz, o-Mes), 139.1 (dm, 1JFC ∼ 246 Hz, p-C6F5), 136.7 (dm, 1JFC ∼ 245 Hz, m-C6F5), 132.2 (d, 3JPC = 11.5 Hz, m-Mes), 118.7 (i-C6F5), 114.9 (d, 1 JPC = 71.1 Hz, i-Mes), 23.3 (d, 3JPC = 4.6 Hz, o-Me), 22.6 (d, 1JPC = 42.1 Hz, PEtCH2), 21.0 (d, 5JPC = 1.4 Hz, p-Me), 8.2 (d, 2JPC = 5.1 Hz, P CH3 31 1 Et ). P{ H} NMR (202 MHz, CD2Cl2, 253 K): δ = 16.3 (br m). 19 F NMR (470 MHz, CD2Cl2, 253 K): δ = −134.6 (m, 2F, o-C6F5), −160.2 (t, 3JFF = 20.7 Hz, 1F, p-C6F5), −165.7 (m, 2F, m-C6F5), [Δδ19Fp,m = 5.5]. 11B{1H} NMR (160 MHz, CD2Cl2, 253 K): δ = −2.4 (ν1/2 ∼ 600 Hz). X-ray Crystal Structure Analysis of 4c. Formula C39H27BF10O2P * CH2Cl2, M = 939.31; colorless crystal, 0.40 × 0.10 × 0.07 mm; a = 11.8807(4) Å, b = 13.8628(3) Å, c = 24.3570(7) Å, β = 98.872(2)°; V = 3963.6(2) Å3; ρcalc = 1.574 cm−3; μ = 2.835 mm−1; empirical absorption correction (0.397 ≤ T ≤ 0.826); Z = 4; monoclinic, space group P21/c (No. 14); λ = 1.54178 Å; T = 223 K; ω and φ scans, 31 946 reflections collected (±h, ± k, ± l), [(sinθ)/λ] = 0.60 Å−1, 6963 independent (Rint = 0.054) and 6009 observed reflections [I ≥ 2σ(I)]; 557 refined parameters, R = 0.053, wR2 = 0.145; max. residual electron density 0.59 (−0.80) e Å−3; hydrogen atoms calculated and refined as riding atoms.

CD2Cl2, 298 K): δ = −133.4 (m, 2F, o-C6F5), −164.7 (t, 3JFF = 20.5 Hz, 1F, p-C6F5), −166.9 (m, 2F, m-C6F5), [Δδ19Fp,m = 2.2]. 11B{1H} NMR (192 MHz, CD2Cl2, 298 K): δ = −10.4 (ν1/2 ∼ 70 Hz). X-ray Crystal Structure Analysis of 3d. Formula C36H36BF10P, M = 700.43; colorless crystal, 0.20 × 0.10 × 0.05 mm; a = 10.2366(2) Å, b = 23.1031(5) Å, c = 14.2896(3) Å, β = 90.937(1)°; V = 3379.00(12) Å3; ρcalc = 1.377 g cm−3; μ = 1.440 mm−1; empirical absorption correction (0.762 ≤ T ≤ 0.932); Z = 4; monoclinic, space group P21/c (No. 14); λ = 1.54178 Å; T = 223 K; ω and φ scans, 27 971 reflections collected (±h, ± k, ± l), [(sinθ)/λ] = 0.60 Å−1, 5915 independent (Rint = 0.082) and 4344 observed reflections [I ≥ 2σ(I)]; 441 refined parameters, R = 0.054, wR2 = 0.143; max. residual electron density 0.27 (−0.27) e Å−3; hydrogen atoms calculated and refined as riding atoms. Preparation of Compound 4a. In a 10 mL Schlenk flask, XPhos (50.0 mg, 105 μmol, 1 equiv) and tris(pentafluorophenyl)borane (53.7 mg, 105 μmol, 1 equiv) were dissolved in pentane (3 mL). The solution was stirred for 10 min. The Schlenk flask was then evacuated, and carbon dioxide gas (2 bar) was added. After 20 min, a white solid started to precipitate. The suspension was cooled to −20 °C and stirred for 2 h. The solution was then removed and the residue dried in vacuo. The product was obtained as a white solid in 80% (86.7 mg, 84.0 μmol) yield. Crystals suitable for X-ray crystal structure analysis could be obtained from a solution of 4a in dichloromethane covered with heptane at −30 °C. Anal. Calcd for C52H49BF15O2P (M = 1032.71 g/mol): C, 60.48; H, 4.78. Found: C, 60.36; H, 4.73. mp: 121.7 °C. 1H NMR (500 MHz, CD2Cl2, 263 K): δ = 7.70 (m, 1H, 4H), 7.65 (m, 1H, 2-H), 7.51 (m, 1H, 3-H), 7.26 (m, 1H, 5-H), 7.09 (s, 2H, m-tipp), 2.92 (sept, 3JHH = 6.8 Hz, 1H, p-iPrCH), 2.67 (CH), 2.14/ 1.48, 1.81/1.12, 1.63/1.14, 1.62/0.73, 1.53/1.43 (each br, each 2H, Cy), 2.24 (sept, 3JHH = 6.8 Hz, 2H, o-iPrCH), 1.25 (d, 3JHH = 6.8 Hz, 6H, p-iPrCH3), 1.07, 0.86 (each d, each 3JHH = 6.8 Hz, each 6H, o-iPrCH3). 13C{1H} NMR (126 MHz, CD2Cl2, 263 K): δ = 162.5 (d, 1 JPC = 116.0 Hz, PCO2), 150.9 (p-tipp), 147.9 (dm, 1JFC ∼ 238 Hz, oC6F5), 146.7 (o-tipp), 145.4 (d, 2JPC = 6.4 Hz, C-6), 139.4 (dm, 1JFC ∼ 251 Hz, p-C6F5), 136.8 (dm, 1JFC ∼ 245 Hz, m-C6F5), 135.7 (d, 3JPC = 11.3 Hz, C-5), 134.0 (d, 2JPC = 10.4 Hz, C-2), 133.8 (d, 3JPC = 1.9 Hz, i-tipp), 133.3 (d, 4JPC = 3.2 Hz, C-4), 128.4 (d, 3JPC = 11.7 Hz, C-3), 121.9 (m-tipp), 119.3 (i-C6F5), 115.5 (d, 1JPC = 64.5 Hz, C-1), 34.58 (CH), 27.6, 27.0, 26.9, 26.8 (d, 3JHH = 2.9 Hz), 25.3 (each br, Cy), 34.7 (p-iPrCH), 31.0 (o-iPrCH), 25.7, 21.8 (o-iPrCH3), 24.0 (p-iPrCH3). 31 1 P{ H} NMR (202 MHz, CD2Cl2, 263 K): δ = 26.8 (ν1/2 ∼ 4 Hz), [14.7 (ca. 8%, br d, 1JPH ∼ 468 Hz, PH: tentatively assigned as XPhosH+)]. 19F NMR (470 MHz, CD2Cl2, 263 K): δ = −133.9 (m, 2F, o-C6F5), −160.5 (t, 3JFF = 20.6 Hz, 1F, p-C6F5), −165.7 (m, 2F, mC6F5), [Δδ19Fp,m = 5.2]. 11B{1H} NMR (160 MHz, CD2Cl2, 263 K): δ = −2.7. X-ray Crystal Structure Analysis of 4a. Formula C52H49BF15O2P, M = 1032.69; colorless crystal, 0.15 × 0.10 × 0.03 mm; a = 9.2878(4) Å, b = 12.0852(5) Å, c = 22.1319(11) Å, α = 85.623(2)°, β = 82.110(2)°, γ = 81.036(2)°; V = 2426.79(19) Å3; ρcalc = 1.413 g cm−3; μ = 1.377 mm−1; empirical absorption correction (0.820 ≤ T ≤ 0.960); Z = 2; triclinic, space group P1 bar (No. 2); λ = 1.54178 Å; T = 223 K; ω and φ scans, 30 139 reflections collected (±h, ± k, ± l), [(sinθ)/λ] = 0.60 Å−1, 8393 independent (Rint = 0.081) and 5990 observed reflections [I ≥ 2σ(I)]; 646 refined parameters, R = 0.057, wR2 = 0.141; max. residual electron density 0.60 (−0.28) e Å−3; hydrogen atoms calculated and refined as riding atoms. Preparation of Compound 4c. In a 10 mL Schlenk flask, ethyldimesitylphosphane (43.0 mg, 145 μmol, 1 equiv) and tris(pentafluorophenyl)borane (74.2 mg, 145 μmol, 1 equiv) were dissolved in pentane (3 mL). The solution was stirred for 10 min. The Schlenk flask was then evacuated, and carbon dioxide gas (2 bar) was added. After 20 min, a white solid started to precipitate. The solution was cooled to −20 °C and stirred for 2 h. The solution was then removed and the residue dried in vacuo. The product was obtained as a white solid in 75% (92.9 mg, 108.8 μmol) yield. Crystals suitable for X-ray crystal structure analysis could be obtained from a solution of 4c in dichloromethane covered with heptane −30 °C. Anal. Calcd for C51H51BF15P (M = 854.39 g/mol): C, 54.82; H, 3.19.

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ASSOCIATED CONTENT

* Supporting Information S

Text and figures giving further experimental, spectroscopic details and crystallographic data. 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]. Author Contributions †

X-ray crystal structure analyses.

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ACKNOWLEDGMENTS Financial support from the Deutsche Forschungsgemeinschaft is gratefully acknowledged. DEDICATION Dedicated to the memory of Professor F. Gordon A. Stone.

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REFERENCES

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Organometallics

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(c) Piers, W. E.; Chivers, T. Chem. Soc. Rev. 1997, 26, 345. (d) See also: Erker, G. Dalton Trans. 2005, 1883 and references citedtherein. (4) (a) Chen, C.; Eweiner, F.; Wibbeling, B.; Fröhlich, R.; Senda, S.; Ohki, Y.; Tatsumi, K.; Grimme, S.; Kehr, G.; Erker, G. Chem.Asian J. 2010, 5, 2199. (b) Chen, C.; Fröhlich, R.; Kehr, G.; Erker, G. Org. Lett. 2011, 13, 62. (c) Jiang, C.; Blacque, O.; Berke, H. Organometallics 2010, 29, 125. (d) Chen, C.; Kehr, G.; Fröhlich, R.; Erker, G. J. Am. Chem. Soc. 2010, 132, 13594. (e) Fan, C.; Piers, W. E.; Parvez, M.; McDonald, R. Organometallics 2010, 29, 5132. (f) Chen, C.; Fröhlich, R.; Kehr, G.; Erker, G. Chem. Commun. 2010, 46, 3580. (g) Liedtke, R.; Fröhlich, R.; Kehr, G.; Erker, G. Organometallics 2011, 30, 5222. (5) For some representative examples, see: (a) Stute, A.; Kehr, G.; Fröhlich, R.; Erker, G. Chem. Commun. 2011, 47, 4288. (b) Voss, T.; Sortais, J.-B.; Fröhlich, R.; Kehr, G.; Erker, G. Organometallics 2011, 30, 548. (c) Zhao, X.; Stephan, D. W. Chem. Commun. 2011, 47, 1833. (d) Mömming, C. M.; Kehr, G.; Fröhlich, R.; Erker, G. Chem. Commun. 2011, 47, 2006. (e) Birkmann, B.; Voss, T.; Geier, S. J.; Ullrich, M.; Kehr, G.; Erker, G.; Stephan, D. W. Organometallics 2010, 29, 5310. (f) Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. Angew. Chem. 2010, 122, 1444;(g) Angew. Chem., Int. Ed. Engl. 2010, 49, 1402. (h) Dureen, M. A.; Brown, C. C.; Stephan, D. W. Organometallics 2010, 29, 6594. (i) Dureen, M. A.; Brown, C. C.; Stephan, D. W. Organometallics 2010, 29, 6422. (j) Menard, G.; Stephan, D. W. J. Am. Chem. Soc. 2010, 132, 1796. (6) Recent reviews: (a) Stephan, D. W. Org. Biomol. Chem. 2008, 6, 1535. (b) Stephan, D. W.; Erker, G. Angew. Chem. 2010, 122, 50;(c) Angew. Chem., Int. Ed. 2010, 49, 46. (d) Stephan, D. W. In Catalysis without Precious Metals; Bullock, R. M., Ed.; Wiley-VCH: Weinheim, Germany, 2010; p 261. (e) Erker, G. Organometallics 2011, 30, 358. (f) Erker, G. Dalton Trans. 2011, 40, 7475. (g) Stephan, D. W.; Greenberg, S.; Graham, T. W.; Chase, P.; Hastie, J. J.; Geier, S. J.; Farrell, J. M.; Brown, C. C.; Heiden, Z. M.; Welch, G. C.; Ullrich, M. Inorg. Chem. 2011, 50, 12338−12348. (h) Erker, G. C. R. Chim. 2011, 14, 831. (7) (a) Welch, G. C.; San Juan, R. R.; Masuda, J. D.; Stephan, D. W. Science 2006, 314, 1124. (b) Welch, G. C.; Stephan, D. W. J. Am. Chem. Soc. 2007, 129, 1880. (c) Welch, G. C.; Cabrera, L.; Chase, P. A.; Hollink, E.; Masuda, J. D.; Wei, P.; Stephan, D. W. Dalton Trans. 2007, 3407. (d) Wang, H.; Fröhlich, R.; Kehr, G.; Erker, G. Chem. Commun. 2008, 5966. (e) Spies, P.; Erker, G.; Kehr, G.; Bergander, K.; Fröhlich, R.; Grimme, S.; Stephan, D. W. Chem. Commun. 2007, 5072. (f) Geier, S. J; Gilbert, T. M.; Stephan, D. W. J. Am. Chem. Soc. 2008, 130, 12632. (g) Ullrich, M.; Lough, A. J.; Stephan, D. W. J. Am. Chem. Soc. 2009, 131, 52. (8) (a) Spies, P.; Schwendemann, S.; Lange, S.; Kehr, G.; Fröhlich, R.; Erker, G. Angew. Chem. 2008, 120, 7654;(b) Angew. Chem., Int. Ed. 2008, 47, 7543. (c) Schwendemann, S.; Tumay, A.; Axenov, K. V.; Peuser, I.; Kehr, G.; Fröhlich, R.; Erker, G. Organometallics 2010, 29, 1067. (d) Chase, P. A.; Jurca, T.; Stephan, D. W. Chem. Commun. 2008, 1701. (e) Chen, D.; Klankermayer, J. Chem. Commun. 2008, 2130. (f) Axenov, K.; Kehr, G.; Fröhlich, R.; Erker, G. J. Am. Chem. Soc. 2009, 131, 3454. (9) (a) Axenov, K.; Mömming, C. M.; Kehr, G.; Fröhlich, R.; Erker, G. Chem.Eur. J. 2010, 16, 14069. (b) Moebs-Sanchez, S.; Bouhadir, G.; Saffon, N.; Maron, L.; Bourissou, D. Chem. Commun. 2008, 3435. (c) Xu, B.-H.; Kehr, G.; Fröhlich, R.; Wibbeling, B.; Schirmer, B.; Grimme, S.; Erker, G. Angew. Chem. 2011, 123, 7321;(d) Angew. Chem., Int. Ed. 2011, 50, 7183. (10) (a) McCahill, J. S. J.; Welch, G. C.; Stephan, D. W. Angew. Chem. 2007, 119, 5056;(b) Angew. Chem., Int. Ed. 2007, 46, 4968. (c) Tarakeshwar, P.; Kim, K. S. J. Phys. Chem. A 1999, 103, 9116. (d) Tarakeshwar, P.; Lee, S. J.; Lee, J. Y.; Kim, K. S. J. Phys. Chem. A 1999, 103, 184. (e) Ullrich, M.; Seto, K.; Lough, A. J.; Stephan, D. W. Chem. Commun. 2008, 2335. (f) Stirling, A.; Hamza, A.; Rokob, T. A.; Papai, I. Chem. Commun. 2008, 3148. (g) Guo, Y.; Li, S. Eur. J. Inorg. Chem. 2008, 2501. (11) (a) Dureen, M. A.; Stephan, D. W. J. Am. Chem. Soc. 2009, 131, 8396. (b) Biagini, P.; Lugli, G.; Abis, L.; Andreussi, P. U.S. Patent 5,602,269, 1997.

(12) (a) Otten, E.; Neu, R. C.; Stephan, D. W. J. Am. Chem. Soc. 2009, 131, 9918. (b) Neu, R. C.; Otten, E.; Lough, A.; Stephan, D. W. Chem. Sci. 2011, 2, 170. (13) (a) Cardenas, A. J. P.; Culotta, B. J.; Warren, T. H.; Grimme, S.; Stute, A.; Fröhlich, R.; Kehr, G.; Erker, G. Angew. Chem. 2011, 123, 7709;(b) Angew. Chem., Int. Ed. 2011, 50, 7567. (14) (a) Mömming, C. M.; Otten, E.; Kehr, G.; Fröhlich, R.; Grimme, S.; Stephan, D. W.; Erker, G. Angew. Chem. 2009, 121, 6770; (b) Angew. Chem., Int. Ed. 2009, 48, 6643. (c) Peuser, I.; Neu, R. C.; Zhao, X.; Ulrich, M.; Schirmer, B.; Tannert, J. A.; Kehr, G.; Fröhlich, R.; Grimme, S.; Erker, G.; Stephan, D. W. Chem.Eur. J. 2011, 17, 964. (15) (a) Geier, S.; Stephan, D. W. J. Am. Chem. Soc. 2009, 131, 3476. (b) Sumerin, V.; Schulz, F.; Nieger, M.; Leskela, M.; Repo, T.; Rieger, B. Angew. Chem. 2008, 120, 6090;(c) Angew. Chem., Int. Ed. 2008, 47, 6001. (d) Sumerin, V.; Schulz, F.; Atsumi, M.; Wang, C.; Nieger, M.; Leskela, M.; Repo, T.; Pyykko, P.; Rieger, B. J. Am. Chem. Soc. 2008, 130, 14117. (e) Schwendemann, S.; Fröhlich, R.; Kehr, G.; Erker, G. Chem. Sci. 2011, 2, 1842. (f) Jiang, C.; Blacque, O.; Fox, T.; Berke, H. Dalton Trans. 2011, 40, 1091. (16) (a) Chase, P. A.; Stephan, D. W. Angew. Chem. 2008, 120, 7543; (b) Angew. Chem., Int. Ed. 2008, 47, 7433. (c) Holschumacher, D.; Bannenberg, T.; Hrib, C. G.; Jones, P. G.; Tamm, M. Angew. Chem. 2008, 120, 7538;(d) Angew. Chem., Int. Ed. 2008, 47, 7428. (17) Huang, X.; Anderson, K. W.; Zim, D.; Jiang, L.; Klapars, A.; Buchwald, S. L. J. Am. Chem. Soc. 2003, 125, 6653. (18) Parks, D. J.; Piers, W. E.; Yap, G. P. A Organometallics 1998, 17, 5492.

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