Nickel Phosphanido Hydride Complex - American Chemical Society

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Nickel Phosphanido Hydride Complex: An Intermediate in the Hydrophosphination of Unactivated Alkenes by Primary Phosphine Yulia S. Ganushevich,† Vasily A. Miluykov,*,† Fedor M. Polyancev,† Shamil K. Latypov,*,† Peter Lönnecke,‡ Evamarie Hey-Hawkins,‡ Dmitry G. Yakhvarov,† and Oleg G. Sinyashin† †

A.E. Arbuzov Institute of Organic and Physical Chemistry of the Russian Academy of Sciences, Arbuzov Street 8, 420088, Kazan, Russia ‡ Institut für Anorganische Chemie, Universität Leipzig, Johannisallee 29, 04103, Leipzig, Germany S Supporting Information *

ABSTRACT: Heating of a mixture of [Ni(CH2CH2)(dtbpe)] (dtbpe = 1,2-bis(di-tert-butylphosphino)ethane) and 2,6-dimesitylphenylphosphine (DmpPH2) in toluene gives the secondary phosphine (Dmp)P(Et)(H) (1) as the main product. However, thermolysis of [Ni(CH3)2(dtbpe)] in the presence of DmpPH2 in toluene leads to the mononuclear nickel phosphanido hydride complex [NiH{P(Dmp)(H)}(dtbpe)] (2), the product of an oxidative addition of a primary phosphine to nickel(0). The structure of complex 2 was confirmed by single-crystal X-ray diffraction and DNMR studies. The mutual exchange of tautomers in which the Ni−H and P−H hydrogen atoms interchange as well as the position of the hydrido and the phosphanido ligand occurs in solution. The stoichiometric reaction of 2 with 1-hexene proceeds regiospecifically to form the secondary phosphine (Dmp)P(Hex)(H) (3).

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INTRODUCTION The addition of primary or secondary phosphines to unsaturated compounds is catalyzed by acids, strong bases, or radical initiators.1 However, the hydrophosphination reactions proceed with high regio- and stereoselectivity and “atomic efficiency”2 only when transition metal complexes are employed as catalysts,3 offering a promising way to novel phosphines for homogeneous asymmetric catalysis. A particularly well-developed area of catalytic hydrophosphination involves the reactions of activated olefins with secondary phosphines catalyzed by Pt4 and Pd5 complexes. According to the proposed and generally accepted mechanism of the hydrophosphination of alkenes, the catalytic cycle starts with an oxidative addition of a P−H bond to the metal(0) center (A) followed by insertion of the CC fragment into the M−H bond (B) and reductive elimination of the addition product6 (Scheme 1). Oxidative addition of a primary or secondary phosphine with formation of a metal phosphanido hydride complex (B) was previously detected in the case of platinum7 and tantalum8 complexes only. However, hydrophosphination reactions catalyzed by Ni-based complexes proceed more efficiently and allow nonactivated alkenes to be employed.9 Thus, synthesis and stabilization of nickel complexes that are potential intermediates in the catalytic cycle are of considerable fundamental and synthetic interest. Herein, we report the first example of the hydrophosphination of nonactivated olefins by a primary phosphine in the presence of nickel(0) complexes. The combination of bulky bisphosphine ligand dtbpe 10 (dtbpe = 1,2-bis(di-tertbutylphosphino)ethane) and sterically hindered primary phosphine DmpPH211 (Dmp = 2,6-dimesitylphenyl) stabilizes © XXXX American Chemical Society

Scheme 1. Mechanism of a Metal-Catalyzed Hydrophosphination of Alkenes

the nickel phosphanido hydride complex, a key intermediate in the nickel-catalyzed hydrophosphination.

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RESULTS AND DISCUSSION Synthesis. It is known that displacement of the weakly coordinating cod (cod = 1,5-cyclooctadiene) ligands in [Ni(cod)2] by MesPH2 (Mes = 2,4,6-trimethylphenyl) gives the homoleptic tetracoordinate complex [Ni{P(Mes)(H)2}4].12 While no displacement of cod or ethylene in [Ni(cod)(dtbpe)]13 and [Ni(CH2CH2)(dtbpe)] by DmpPH2 was observed at room temperature or at 70 °C, heating of a toluene solution containing [Ni(CH2CH2)(dtbpe)] and DmpPH2 at Received: May 8, 2013

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dx.doi.org/10.1021/om400408e | Organometallics XXXX, XXX, XXX−XXX

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110 °C results in direct formation of the secondary phosphine (Dmp)P(Et)(H) (1) in 89% yield (Scheme 2). Scheme 2. Synthesis of (Dmp)P(Et)(H) (1)

Phosphine 1 was fully characterized by 1H, 31P, and 13C NMR spectroscopy and a single-crystal X-ray diffraction study (see Supporting Information). It should be noted that heating of a toluene solution containing 2 equivalents of [Ni(CH2 CH2)(dtbpe)] and 1 equivalent of DmpPH2 at 110 °C does not give the tertiary phosphine DmpPEt2. The highly reactive “Ni0(dtbpe)”,14 formed in situ by thermolysis of [Ni(CH3)2(dtbpe)], reacts with DmpPH2 to give nickel complex 2 (Scheme 3), which was isolated in 70% yield from n-hexane. The structure of 2 was confirmed by NMR15 spectroscopy and single-crystal X-ray analysis (Figure 1). The reaction of complex 2 with 1-hexene further confirmed its role in the catalytic cycle of the hydrophosphination. Heating of a toluene solution of [NiH{P(Dmp)(H)}(dtbpe)] (2) with 2 equivalents of 1-hexene at 110 °C leads to formation of the secondary phosphine (Dmp)P(Hex)(H) (3) in 62% yield.16 The reaction proceeds regiospecifically to give the antiMarkovnikov product only. Structure. The solid-state structure of 2 revealed a “cap”like arrangement of the Mes and tBu groups, providing a protective environment for the Ni−P bond (Figure 1). The Ni atom of 2 has a slightly distorted square-planar environment17 (sum of bond angles around Ni is 362.15°). In addition a calculated least-squares plane through the atoms P1, P2, P3, H1Ni, and Ni1 reveals the strongest deviation of +0.21(2) Å for P3 and −0.24(2) Å for H1Ni. The Ni−P3 bond length of 2.175(2) Å is in the range of a Ni−P single bond, as was also observed for the few known nickel phosphanido complexes [Ni{P(SiMe3)2}(PMe3)2]2 (2.186(3) Å),18 [Ni(PtBu2)(dtbpe)] (2.208(1) Å),19 and [Ni{P(SiMe3)2}(Cy2PCH2CH2PCy2)] (2.225(2) Å)20). The estimated Ni−H bond length of 1.44(4) Å is also in good agreement with literature values of comparable compounds (e.g., 1.46(3) Å).21 Theoretical Calculations. Although the single-crystal Xray analysis provided exact information on the position of the heavy atoms in 2, hydrogen atoms are generally difficult to localize with sufficient accuracy and confidence. Thus an

Figure 1. Molecular structure of 2 (thermal ellipsoids are drawn at 50% probability). H atoms, except on P3 and Ni1, have been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ni1−P1, 2.156(2); Ni1−P3, 2.175(2); Ni1−P2, 2.220(2); P3−C19, 1.837(5); Ni1−H1Ni, 1.44(4); P3−H1P, 1.33(3); P1−Ni1−P3, 157.63(6); P1− Ni1−P2, 92.56(6); P3−Ni1−P2, 104.92(6); P1−Ni1−H1Ni, 88.9(13); P3−Ni1−H1Ni, 75.7(13); P2−Ni1−H1Ni, 172.0(13); C19−P3−Ni1, 119.6(2).

attempt to describe the structure of the nickel complex (2) as an isomer (NiPH2, 2b) (see below), with all hydrogen atoms on calculated positions, resulted in slightly, but significantly higher R-values. Especially for wR2(all) an increase of 1.5% could be observed. Therefore, a combination of quantum-chemical calculations and NMR spectroscopy was used to confirm the proposed structure of 2. In general, there are three possible isomeric forms of 2 with different locations of the phosphine hydrogen atoms: both hydrogen atoms are attached to nickel (NiH2P, 2a), both hydrogen atoms are located at the phosphorus atom (NiPH2, 2b), or one hydrogen atom is bonded to phosphorus and the other one to nickel (NiHPH, 2c,d). To get preliminary information about the isomers 2a−d, their energies were calculated using two approaches: PBEPBE1/6-31G(d) and B3LYP/{Ni(Lanl2dz); P,C,H(6-31G(d))} (denoted as B3LYP/DZ(d)) (Table 1). According to these calculations, the NiH2 isomer (2a) does not correspond to an energy minimum. There are two stable conformations (2c, 2d) for the NiHPH isomer (mutual trans or cis orientation of Ni−H and P−H hydrogen atoms), although 2d can also be dismissed from further consideration due to high energy. Thus, the NiPH2 (2b) (B3LYP/DZ(d)) or the trans isomer of NiHPH (2c) (PBEPBE1/6-31G(d)) are expected to be favored depending on the method of calculation and can

Scheme 3. Synthesis of [NiH{P(Dmp)(H)}(dtbpe)] (2) and (Dmp)P(Hex)(H) (3)

B


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Table 1. Isomers of 2 with Corresponding PBEPBE1/6-31G(d) and B3LYP/DZ(d) (in parentheses) Energies

Figure 2. NMR spectra of 2 in d8-toluene: 31P{1H} at 303 K (a), 253 K (c), 203 K (e), 31P at 203 K (g), 1H at 303 K (b), 253 K (d), 203 K(f), 1 H{31P} at 203 K (h), and 1D 1H−31P HSQC at 203 K (i) (■, tBu2P(O)CH2CH2PtBu2; *, [Ni(dtbpe)(μ-H)]2; ▲, [{Ni(dtbpe)}2(μ-η2:η2C6D5CD3)]).

phosphines and their complexes.22−24 Thus, the observed pattern cannot be ascribed to any isomer solely, and probably a fast exchange between different isomers takes place in solution. Indeed, at low temperature, dramatic changes in the NMR spectra were observed. In the 31P NMR spectra, the signals of P1 and P2 start to broaden extremely; then, at ca. 253 K, coalescence was achieved (Figure 2c), and at ca. 233 K, two signals appeared as a doublet (2JP−P = 84 Hz) for P1 and a singlet for P2 (Figure S10c). For the phosphorus atom P3, a doublet (2JP−P = 84 Hz) was observed only at 203 K (Figure 2e). P−P COSY experiments (Figure S15) unambiguously proved a large SSC between P1 and P3. In addition, the protoncoupled 31P NMR spectra (Figure 2g) allowed large spin−spin couplings with hydrogen to be observed. Spectacular changes at lower temperature were also observed in the 1H NMR spectra of 2 (Figure 2b). A featureless signal at

exist in solution. It is also noteworthy that according to calculations, P3 should have a large spin−spin coupling (SSC) of ca. 225 Hz with the geminal protons in the NiPH2 isomer 2b. NMR Study of 2. The structure of complex 2 in solution was analyzed by NMR (1H−13P/13C HSQC/HMBC, 31P−31P COSY, Figures S4−S8, Supporting Information) at different temperatures. The phosphorus atoms of the dtbpe ligand are equivalent, with a doublet at 90.7 ppm (2JP−P = 39 Hz), and the resonance of the P(Dmp)-based ligand at −60.8 ppm splits into a triplet of triplets (1JP−H = 75 Hz) in the 31P NMR spectrum at room temperature. At first sight these experimental data support the formation of the predicted isomer NiPH2 (2b). However, no clear indication of phosphine protons was seen in the 1H NMR spectrum (Figure 2b), and the value of 1JP−H is significantly smaller than normally observed for primary C


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δH −3 at room temperature appeared as two signals at ca. δH 4.5 (Hb) and δH −10.8 (Ha) at 233 K only (Figure S9c). At 203 K Hb appeared as a doublet (1JP−H = 204 Hz), while the signals for Ha remained broad (Figure 2f). On decoupling to P3, the doublet at δH 4.5 is observed as a singlet (Figure 2h), which unambiguously proves the Hb strong coupling with P3, while the broad signal at δH −10.8 appeared as a slightly resolved doublet presumably due to coupling with another phosphorus nucleus. Finally, 2D 1H−31P HSQC and HMBC experiments (Figures S13, S14) allowed for specific H−P correlations to be made. Thus, according to low-temperature NMR data (chemical shift (CSs) and net of SSCs), the structure of compound 2 in solution can be unambiguously assigned to the phosphanido hydride isomer NiHPH (2c) (Table 1), where the high-field resonance δH −10.8 is due to the hydride, NiHa, and the doublet at δH 4.5 (1JP−H = 204 Hz) is due to P3Hb. Taking into account that according to calculations a twobond phosphorus−phosphorus SSC should be notably larger for a trans than a cis orientation (39 versus −8 Hz), the doublet at δP 96.9 and the singlet at δP 84.3 should be assigned to P1 and P2, respectively. P3 should have large SSCs with the hydrogen atoms Ha and Hb but of opposite sign (−48 versus 146 Hz). To check the relative signs of these couplings, 1D 1 H−31P HSQC experiments in sensitive mode phase were carried out. Indeed, in 1D 1H−31P HSQC spectra with selective excitation of P3 there are responses of different phase for Hb and Ha (Figure 2i). This result unequivocally proves that SSCs between P3 and these two protons are of different sign (−63 and 204 Hz), in agreement with calculations. The observed line shape evolution with temperature can be attributed to mutual exchange between two NiHPH isomers that are related by a Cs symmetry operation (Figure 3). These

interchange as well as the position of the hydrido and the phosphanido ligand.

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EXPERIMENTAL SECTION

NMR Spectroscopy. All NMR experiments were performed with a Bruker AVANCE-600 spectrometer (14.1 T) equipped with a 5 mm diameter gradient inverse broad band probehead and a pulsed gradient unit capable of producing magnetic field pulse gradients in the zdirection of 53.5 G·cm−1. Frequencies are 600.13 MHz in 1H NMR, 242.94 MHz in 31P NMR, and 150.90 MHz in 13C NMR experiments. NMR experiments were carried out using standard Bruker pulse programs. The pulse widths were 7 μs (90°), 12 μs (90°), and 11.3 μs (90°) for 1H, 13C, and 13P, respectively. Typically, 16K and 64K data points were collected for one-dimensional proton and carbon/ phosphorus spectra, respectively. 2D experiment parameters were as follows. For 1H−1H correlations (COSY): relaxation delay 1.5 s, data matrix 1K × 2K (256 experiments to 0.5K, zero filling in F1, 1K in F2), two transients in each experiment. For 1H−13C correlations (HSQC): optimized for J = 145 Hz, relaxation delay 2.5 s, data matrix 0.5K × 2K (256 experiments to 0.5K, zero filling in F1, 2K in F2), 16 transients in each experiment. For 1H−13C long-range correlations (HMBC): optimized for J = 8 Hz, relaxation delay 2.5 s, data matrix 0.5K × 2K (256 experiments to 0.5K, zero filling in F1, 2K in F2), 48 transients in each experiment. For 1H−31P correlations (HSQC): optimized for J = 200 Hz, relaxation delay 2.5 s. For 1H−31P correlations (1D HSQC): optimized for J = 110 Hz, relaxation delay 1.5 s. For 1H−31P long-range correlations (HMBC): optimized for J = 10 Hz, relaxation delay 2.5 s. All 2D spectra were weighted with sinebell squared and shifted (π/2 in both dimensions) window functions and processed with the Bruker software package. The sample of complex 2 for DNMR studies was prepared directly in an NMR tube because of its extreme sensitivity to oxygen and moisture. The DmpPH2 (7.2 × 10−2 g, 0.21 mmol) and [Ni(CH3)2(dtbpe)] (10.0 × 10−2 g, 0.24 mmol) were dissolved in d8toluene (0.6 mL). After heating for 6 h at 50−60 °C the NMR tube was sealed. The excess of the complex [Ni(CH3)2(dtbpe)] was used to full conversion of DmpPH2 that resulted further in the additional signals of [Ni(dtbpe)(μ-H)] 2 14 and [{Ni(dtbpe)} 2 (μ-η 2 :η 2 C6D5CD3)]16b complexes. Calculations. The quantum chemical calculations were performed using Gaussian 03.25 Full geometry optimizations have been carried out using two approaches: within the framework of the PBEPBE1 functional employing the 6-31G(d) basis and using the B3LYP functional employing an ECP basis such as LANL2DZ (Los Alamos National Laboratory 2 double-ζ) for metals, while using 6-31G(d) basis sets for all other nonmetal atoms. Chemical shifts and spin−spin couplings were determined by the GIAO26 method within the DFT framework using the PBE1PBE functional at the 6-31G(d) level with geometry optimization on the same level. X-ray Structure Determination. The data were collected on a Gemini diffractometer (Agilent Technologies) using Mo Kα radiation (λ = 0.71073 Å) and ω-scan rotation. Data reduction was performed with CrysAlis Pro27 including the program SCALE3 ABSPACK28 for empirical absorption correction. The structures were solved by direct methods (DmpPH2: SHELXS-97;29 1, 2: SIR-9230), and the refinement was performed with SHELXL-97.29 All non-hydrogen atoms were refined with anisotropic thermal parameters. Hydrogen atoms for DmpPH2 and for the nondisordered part of 1 and hydrogen atoms bonded to phosphorus and nickel in 2 were localized by difference-density Fourier maps calculated at the final stage of the structure refinement. All other hydrogen atoms were calculated on idealized positions using the riding model. For 1 the ethyl and hydrogen substituents on phosphorus are disordered over two positions with a ratio of 0.62(2):0.38(2). Structure figures were generated with DIAMOND-3.31 CCDC 934782 (DmpPH2), 934783 (1), and 934784 (2) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc. cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallo-

Figure 3. Tautomeric equilibrium of 2.

isomers are equivalent in terms of NMR, but the two phosphorus atoms and two protons have interchanged their magnetic environment. At room temperature, due to fast exchange on the NMR time scale, the following processes proceed: (1) phosphorus atoms P1 and P2 resonate at intermediate frequency; (2) Ha and Hb resonate at intermediate frequency, but the signal is very broad due to the very large nonequivalence of their inherent chemical shifts (CSs) (∼15 ppm); JP−H between P3 and Ha/Hb is relatively small due to averaging of individual SSCs ((204 − 63)/2 = 70.5 Hz).

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CONCLUSIONS In summary, we have prepared and characterized the first example of a terminal phosphanido hydride nickel complex, [NiH{P(Dmp)(H)}(dtbpe)] (2), the product of an oxidative addition of primary phosphine to a nickel(0) species. The role of complex 2 as a key intermediate in a hydrophosphination was confirmed by reaction with 1-hexene; only the secondary phosphine (Dmp)P(Hex)(H) was formed as an antiMarkovnikov product. In solution, 2 shows a dynamic equilibrium in which the Ni−H and P−H hydrogen atoms D


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Dmp), 145.8 (d, Dmp, JP−C = 11.7 Hz), 150.6 (d, P-aryl, JP−C = 23.3 Hz). Synthesis of (2,6-Dimesitylphenyl)(n-hexyl)phosphine ((Dmp)P(Hex)(H)) (3). A toluene solution (5 mL) of 1-hexene (0.09 g, 1.07 mmol, 10% excess) was added to a toluene solution (2 mL) of 2 (0.35 g, 0.49 mmol) and stirred for 12 h at 110 °C. After cooling to room temperature, the solution was filtered and the filtrate was concentrated under vacuum. The residue was purified by column chromatography using a petroleum ether/toluene mixture (2:1) to give 0.13 g (62%) of 3 as a white solid. Mp: 179 °C. Anal. Calcd for C30H39P (430.60): C 83.68, H 9.13. Found: C 83.5, H 8.99. 1H NMR (400.0 MHz, C6D6, 295 K): δ 0.54 (m, 3H, CH3), 1.24 (m, 8H, CH2), 1.80 (m, 2H, CH2), 2.04 (s, 6H, CH3 (Mes)), 2.11 (s, 6H, CH3 (Mes)), 2.42 (s, 6H, CH3 (Mes)), 3.55 (ddd, 1H, 1JH−P = 227.0 Hz, 3 JH−H = 9.1 Hz, 3JH−H = 7.0 Hz, PH), 6.96 (s, 2H, Mes), 6.98 (s, 2H, Mes), 7.03 (d, 2H, 3JH−H = 6.9 Hz, Dmp), 7.44 (t, 1H, 3JH−H = 6.9 Hz, Dmp). 31P NMR (161.9 MHz, CDCl3, 295 K): δ −72.0 (d, 1JP−H = 227 Hz). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ 9.4 (s, CH3), 12.2 (s, CH2), 12.5 (s, CH2), 12.9 (s, CH2), 14.2 (d, 2JP−C = 8 Hz, CH2), 19.05 (d, 1JP−C = 21 Hz, CH2), 20.2 (s, o-Me), 22.4 (s, p-Me), 128.0 (d, 3JC−P = 2.2 Hz,), 128.3 (s), 128.6 (d, 2JC−P = 3 Hz), 132.1 (s), 135.2 (d, 2JC−P = 42 Hz), 137.0 (d, 2JC−P = 39 Hz), 139.5 (d, 2JC−P = 2 Hz), 148.6 (d, 1JC−P = 13 Hz).

graphic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)1223-336-033; or [email protected]). General Data. All reactions and manipulations were carried out under dry pure N2 in standard Schlenk apparatus. All solvents except CDCl3 were distilled from sodium/benzophenone and stored under nitrogen before use. CDCl3 (99.96%) was purchased from Aldrich, degassed, dried over CaH2, and stored under activated 4 Ǻ molecular sieves in an inert atmosphere. dtbpe,32 [NiCl2(dtbpe)],33 and DmpPH234 were obtained according to literature procedures. 1,2Dibromoethane (98%) was purchased from Aldrich and used without additional purification. Synthesis of [Ni(C2H4)(dtbpe)]. 1,2-Dibromoethane (3.33 g, 1.53 mL, 17.70 mmol) was added to a suspension of [NiCl2(dtbpe)] (2.65 g, 5.91 mmol) and Mg turnings (0.85g, 35.47 mmol) in THF (60 mL) at room temperature. The reaction mixture was slightly heated until gas evolution was observed. After 30 min the solution had turned brown. After an additional 5 h of stirring at room temperature, the solvent was evaporated under vacuum and the residue was extracted with 100 mL of petroleum ether/toluene (10:1). The extract was dried under vacuum to afford pure [Ni(C2H4)(dtbpe)] as a yellow product (2.22 g, 5.48 mmol, 93%). Mp: 175 °C (dec). Anal. Calcd for C20H44NiP2 (405.20): C 59.23, H 10.86. Found: C 59.1, H 10.69. 1H NMR (400.0 MHz, C6D6, 295 K): δ 1.14 (s, 36H, tBu), 1.46 (s, 4H, CH2, dtbpe), 2.39 (s, 4H, CH2CH2). 31P NMR (161.9 MHz, C6D6, 295 K): δ 93.1 (s). Synthesis of (2,6-Dimesitylphenyl)(ethyl)phosphine ((Dmp)P(Et)(H)) (1). A solution of DmpPH2 (0.23 g, 0.66 mmol) in toluene (10 mL) was added to a solution of [Ni(C2H4)(dtbpe)] (0.27 g, 0.66 mmol) in toluene (10 mL) and stirred for 6 h at 110 °C. After cooling to room temperature, the mixture was filtered and the filtrate was concentrated under vacuum. The residue was purified by column chromatography using a petroleum ether/toluene mixture (2:1) to give 0.22 g (89%) 6 as a white solid. Recrystallization from ethanol afforded pure 1 as colorless crystals (0.14 g, 0.30 mmol, 48%). Mp: 137 °C. Anal. Calcd for C26H31P (374.50): C 83.39, H 8.34. Found: C 83.6, H 8.49. 1H NMR (400.0 MHz, C6D6, 295 K): δ 0.75 (dt, 3H, 3 JH−P = 14.7, 3JH−H = 7.7 Hz, CH3), 0.94 (m, 1H, CH2), 1.40 (m, 1H, CH2), 2.01 (s, 6H, CH3 (Mes)), 2.09 (s, 6H, CH3 (Mes)), 2.35 (s, 6H, CH3 (Mes)), 3.40 (ddd, 1H, 1JH−P = 223.0, 3JH‑Ha = 8.6, 3JH‑Hb = 7.0 Hz, PH), 6.94 (s, 2H, Mes), 6.95 (s, 2H, Mes), 7.05 (d, 2H, 3JH−H = 7.6 Hz, Dmp), 7.38 (t, 1H, 3JH−H = 7.6 Hz, Dmp). 31P NMR (161.9 MHz, C6D6, 295 K): δ −62.1 (d, 1JP−H = 223.0 Hz). 13C{1H} NMR (100.6 MHz, CDCl3, 295 K): δ 13.67 (d, 2JP−C = 8.4 Hz, PCH2CH3), 14.05 (d, 1JP−C = 11.3 Hz, PCH2CH3), 20.71 (s, o-Me), 21.11 (s, pMe), 128.02 (d, 3JC−P = 2.2 Hz), 128.20 (s), 128.52 (d, 2JC−P = 1.8 Hz), 130.28 (s), 135.61 (d, 2JC−P = 43.6 Hz), 136.52 (d, 2JC−P = 43.6 Hz), 139.29 (d, 2JC−P = 1.8 Hz), 145.36 (d, 1JC−P = 11.0 Hz). Synthesis of [NiH{P(Dmp)(H)}(dtbpe)] (2). A cold toluene solution (5 mL) of DmpPH2 (42 mg, 0.123 mmol) was added to a solution of [Ni(CH3)2(dtbpe)] (50 mg, 0.123 mmol) in toluene (5 mL) at −35 °C. After stirring for 6 h at 50−60 °C the solvent was evaporated under reduced pressure. The solid was extracted with nhexane (10 mL), filtered, concentrated, and cooled to −35 °C for 1 d. Large orange blocks formed, which were isolated by filtration, washed with cold n-pentane, and dried under vacuum to afford pure 2 (62 mg, 0.085 mmol, 70% yield). Mp: 132 °C (dec). Anal. Calcd for C42H67NiP3 (723.59): C 69.71, H 9.33. Found: C 69.01, H 9.45. 1H NMR (600.13 MHz, d8-toluene, 303 K): δ −3.10 (br, 2H, PH2), 0.97 (d, 36H, 3JH−P = 11.7 Hz, tBu), 2.08 (s, 4H, CH2), 2.32 (s, 6H, CH3), 2.48 (s, 12H, CH3), 6.88 (s, 1H, Dmp), 6.93 (s, 4H, Mes), 7.02 (d, 2H, 3JH−H = 7.0 Hz, Dmp). 1H NMR (600.13 MHz, d8-toluene, 203 K): δ −10.8 (br, 1H, NiH), 1.2−1.0 (36H, tBu), 1.4−0.8 (4H, CH2), 2.4−2.1 (18H, CH3), 4.5 (d, 1H, 1JP−H = 204 Hz, PH), 7.1−6.8 (3H, Dmp). 31P NMR (242.94 MHz, d8-toluene, 303 K): δ 90.7 (d, 2JP−P = 39.0 Hz), −60.8 (tt, 1JP−H = 75.0 Hz, 2JP−P = 39.0 Hz). 31P{1H} NMR (242.94 MHz, d8-toluene, 203 K): δ −59.8 (d, 2JP−P = 84 Hz, P3), 84.3 (s, P2), 96.9 (d, 2JP−P = 84 Hz, P1). 13C{1H} NMR (150.90 MHz, d8toluene, 303 K): δ 22.2 (s, CH3), 22.7 (s, CH3), 24.5 (m, PCH2CH2P), 31.3 (s, PC(CH3)3), 35.7 (m, PC(CH3)3), 125.2 (s, Dmp), 126.2 (s, Dmp), 129.4 (s, Dmp), 135.2 (s, Dmp), 136.8 (s, Dmp), 143.5 (s,

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ASSOCIATED CONTENT

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AUTHOR INFORMATION

S Supporting Information *

Text, figures, tables, and CIF files giving X-ray crystallographic data; NMR spectra. This material is available free of charge via the Internet at http://pubs.acs.org. Corresponding Author

*E-mail: [email protected], [email protected]. Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank the Russian Foundation for Basic Research (RFBR 09-03-00933-a and RFBR 13-03-00169-a) and the Ministry of Education and Science of the Russian Federation (contract 16.740.11.0745) for financial support of this work. Y.S.G. also thanks the Sächsisches Ministerium für Wissenschaft und Kunst (SMWK) (AZ: 4-7531.50-04-0361-09/3) for a research fellowship.

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REFERENCES

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Nickel Phosphanido Hydride Complex - American Chemical Society

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