Acid-Promoted Selective CarbonâFluorine Bond ... - ACS Publications

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Acid-Promoted Selective Carbon−Fluorine Bond Activation and Functionalization of Hexafluoropropene by Nickel Complexes Supported with Phosphine Ligands Wengang Xu, Hongjian Sun, Zichang Xiong, and Xiaoyan Li* School of Chemistry and Chemical Engineering, Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, Shandong University, Shanda Nanlu 27, 250100 Jinan, People’s Republic of China S Supporting Information *

ABSTRACT: The electron-rich complex Ni(PMe3)4 was utilized to react with perfluoropropene to obtain Ni(CF2CFCF3)(PMe3)3 (1). The selective C−F bond activation process of the π-coordinated perfluoropropene in 1 was conducted with the promotion of Lewis acids (ZnCl2, LiBr, and LiI) under mild conditions to afford the products Ni(CF3CCF2)(PMe3)2X (X = Cl (2), Br (3), I (4)). The structures of complexes 2 and 3 determined by X-ray single-crystal diffraction confirmed that the C−F bond activation occurred at the geminal position of the trifluoromethyl group. Surprisingly, CF3COOH as a protonic acid could also carry out a similar activation reaction to give rise to Ni(CF3CCF2)(CF3COO)(PMe3)2 (7), while only the addition products Ni(CF2CFHCF3)(CH3COO)(PMe3) (5) and Ni(CF2CFHCF3)(CH3SO3)(PMe3) (6) were obtained with CH3COOH and CH3SO3H. The transmetalation products Ni(CF3CCF2)Ph(PMe3)2 (8), Ni(CF3CCF2)(p-MeOPh)(PMe3)2 (9), and Ni(CF3CCF2)(CCPh)(PMe3)2 (10) were obtained through the reactions of Ni(CF3CCF2)(PMe3)2Cl (2) with PhMgBr, (p-MeOPh)MgBr, and PhCCLi. In contrast, the reaction of complex 2 with PhCH2CH2MgBr delivered complex 11, Ni(CF3CHC−CH2CH2Ph)(PMe3)2, via double C−F bond activation. All of the C(sp2)−F bonds in complex 11 were activated and cleaved. The structures of complexes 5 and 7−11 were determined by X-ray single-crystal structure analysis. A reasonable mechanism was proposed and partially experimentally verified through operando IR and in situ 1H NMR spectroscopy.

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INTRODUCTION

to promote the C−F bond activation of TFE coordinated with Ni and Pd.3s Due to the difficulty in controlling the regioselectivity of the C−F bond activation process, in comparison with the case for TFE, hexafluoropropene as a synthetic monomer for poly(hexafluoropropene) has been rarely investigated for the selective cleavage of C−F bonds.3b,e,i,j,l,q,r In addition to the early report on Lewis acid promoted C−F bond cleavage of hexafluoropropene coordinated to Pt(0),3b selective C−F bond activation of hexafluoropropene at a rhodium center assisted by NEt3 under mild conditions was achieved by Braun’s group,3e and they also realized catalyzed silylation and borylation of hexafluoropropene by a rhodium hydride complex.3i,j Hydrodefluorination of perfluoropropene was completed with the assistance of low-coordinate iron,3f zirconocene hydride,3k and titanium complexes.3l,n In general, most of the reactions on efficient C−F bond functionalization of perfluoropropene are promoted by noble transition metals, under harsh reaction conditions or with poor selectivity. Herein, we synthesized a π-coordinated perfluor-

Selective C−F bond activation and functionalization with transition-metal complexes is an expressively challenged and crucial subject for chemists because of the great strength of the C−F bond and the high electronegativity of the fluorine atom.1 New methods to synthesize organic fluorides have also been developed via transition-metal-promoted C−F bond activation.1c,d Dramatic progress in C(sp2)−F bond activation has been made over the last few decades, especially in aromatic C− F bond activation.2 However, research on selective C−F bond activation of fluoroalkenes is limited.3 The C−F bond activation of fluoroalkenes by transition-metal complexes assisted by Lewis acids is a vital strategy.3a,b,m,q Hacker, Littlecott, and Kemmitt reported that lithium iodide promoted the C−F bond activation of tetrafluoroethylene (TFE) at a Pt(0) center.3a On the basis of this train of thought, Ogoshi developed the catalytic cross-coupling reaction of TFE with arylzinc reagents catalyzed by Pd(0) complexes.3m After that, they extended the methodology to the Suzuki−Miyaura C,Ccoupling reaction and found that a transition-metal fluoride intermediate could be synthesized at high temperature.3q Recently, they developed reactions with Lewis acids or heat © 2013 American Chemical Society

Received: August 22, 2013 Published: November 18, 2013 7122

dx.doi.org/10.1021/om400782v | Organometallics 2013, 32, 7122−7132

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single-crystal X-ray diffraction, the poor crystallographic data with a wR2 value of 23.6% prevent their publication. A ball and stick representation of this structure along with a list of Cartesian coordinates is provided in the Supporting Information. Lewis Acid Promoted Selective C−F Bond Activation of Perfluoropropene. Once perfluoropropene was coordinated with an electron-rich Ni(0) complex supported by PMe3, the resultant complex 1 showed Lewis basic properties. Therefore, a Lewis acid was utilized to promote the activation of a C−F bond. With the consideration of the large affinity of Li and F atoms, LiCl, LiBr, and LiI were reacted with complex 1 (Scheme 2). As expected, complexes 3 and 4 as the

opropene Ni(0) complex and obtained a selective C−F bond activation nickel(II) product with the promotion of Lewis acids. In this process, the C−F bond at the 2-position of perfluoropropene was selectively activated. This has rarely been achieved in previous studies. The selectivity is also different from the palladium-catalyzed coupling reaction of hexafluoropropene with naphthylboronate developed by Ogoshi.3q As reported, upon coordination to electron-rich low-valent transition metals, the fluoroolefin becomes Lewis basic. As a result, this is beneficial to addition reactions of protonic acids to the fluoroolefin moiety to give rise to fluoroalkyl complexes.4 In addition, the C−F bond activation product was also isolated upon reaction with trifluoroacetic acid. Additional functionalization reactions with organometallic reagents were also studied.

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Scheme 2. Lewis Acid Promoted C−F Bond Activation of the Perfluoropropene Ligand in 1

RESULTS AND DISCUSSION Synthesis of a π-Coordinated Perfluoropropene Ni(0) Complex. The reaction of perfluoropropene with Ni(PMe3)4 in toluene afforded the π-coordinated perfluoropropene Ni(0) complex (1) in high yield (Scheme 1). In comparison to the Scheme 1. π-Coordination of Perfluoropropene with Ni(0)

regioselective C−F bond activation products were obtained from the reactions of complex 1 with LiBr and LiI, respectively, in THF solution. However, no corresponding complex could be produced with LiCl in this process, due to the weaker Lewis acidity of LiCl in comparison with that of LiBr and LiI. During the reaction, the reaction mixture of Lewis acids and complex 1 quickly turned from orange-yellow to dark green. After the reaction was complete, the in situ 19F NMR spectra illustrated that the transformation was almost quantitative. When ZnCl2 was used as a stronger Lewis acid, instead of LiCl, the expected C−F bond activation product, complex 2, was obtained. All three of these nickel(II) derivative complexes 2−4 were crystallized from n-pentane. A strong CC band stretching vibration was found in the vicinity of 1695 cm−1 in the IR spectra of complexes 2−4. The proposed structures of complexes 2−4 were supported by 1H, 31P, and 19F NMR. The 19F NMR spectra of the C−F activation products were highly ordered, and the coupling constants were clearly analyzed. The chemical shifts and coupling situations of the 19F NMR of complexes 2−4 were similar. The slight differences in the spectra may be attributed to the different properties of the halogen ligand (X = Cl, Br, I) coordinated to the Ni(II) center. The C−F bond at the 2position of the perfluoropropene ligand was selectively cleaved for different Lewis acids. As an example, the 19F NMR spectrum of complex 2 was analyzed (Figure 1). The 19F NMR spectrum shows three resonances at −48.1, −57.9, and −77.6 ppm and has an integral intensity ratio of 3:1:1. This reveals the existence of the 2perfluoropropenyl ligand. Further analyses of the coupling constants in the 19F NMR spectrum could contribute to the confirmation of the structure. The coupling constants for the first-order multiplet of the Fa atom are doublets of 16.4 and 11.8 Hz and a triplet of 1.1 Hz, which resulted from the

perfluoropropene-coordinated Ni(0) complexes supported by PEt3 and PPh3 ligands,5 the yield of complex 1 is remarkably increased and the coordination number is 4, instead of 3, owing to the smaller steric hindrance effect of trimethylphosphine ligands. Complex 1 could also be obtained in the reaction of Ni(PMe3)2(COD) and hexafluoropropene, but the yield is very low. Complex 1 has greater solubility and thermal stability in comparison with TFE-coordinated Ni(0).3q No reaction occurred when a THF solution of complex 1 was refluxed for 1 h. This indicates that complex 1 is very stable. No CC bond stretching vibration in the IR spectrum of complex 1 was observed. This implies that the CC bond was strongly activated and lost the characteristic of a double bond. Complex 1 could also be regarded as a diorgano Ni(II) complex with a three-membered chelate ring. We consider that the strong donor properties and the smaller steric hindrance effect of the trimethylphosphine ligand led to the behavior of complex 1 being different from that of the early reported examples.5 A more conventional method to evaluate the coordination state of the perfluorinated CC bond is the change in F−F coupling constants after coordination. The geminal coupling constant of 19 F−19F in complex 1 (2JFF = 155.1 Hz) is much larger than that of free perfluoropropene and is comparable to that in fluorinated cyclopropane.6 Moreover, the trans-vicinal coupling constant (3JFF = 70.5 Hz) is much smaller upon coordination. All of these changes suggest that the olefin carbon atoms in complex 1 approach an sp3 hybridization state. In the molecular structure of complex 1, perfluoropropene is coordinated to the Ni center with three trimethylphosphines as supporting ligands. The nickel atom is at the center of a tetrahedron with the middle point of the olefin double bond as one vertex. Although the structure of complex 1 is supported by 7123


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Figure 1. 19F NMR (282 MHz, C6D6, 298 K) spectra of complex 2. Coupling constants are as follows: 4JFaFc = 16.4 Hz, 4JFaFb = 11.8 Hz, 4JPFa = 1.1 Hz, 2JFaFb = 56.4 Hz, 4JPFb = 6.0 Hz, 4JPFc = 5.9 Hz.

coupling of Fa to Fc, Fb, and P atoms, respectively. These couplings also occurred in the signals of Fc and Fb atoms. This C−F bond activation process by a nickel(0) complex occurred selectively at the 2-position of perfluoropropene, while the C− F bond was selectively activated by hydrido rhodium complexes at the 1-position of perfluoropropene.3e The coupling constants of the geminal olefinic fluorine atoms and the fluorine atoms of the trifluoromethyl group are consistent. This indicates the existence of both geminal fluorine atoms and the activation of the C−F bond at the 2-position. The configuration of complex 2 was confirmed by an X-ray crystal structure determination (Figure 2).

atom is 354.2°. This indicates that the four atoms F1, F2, C1, and C2 are almost in the same plane. For the same reason, the four atoms C1, C2, C3, and Ni1 are coplanar because the sum of the three bond angles around the C1 atom is 359.9°. These data imply that both C1 and C2 atoms remain in an sp2 hybridized state after C−F bond activation. The bond parameters related to the Ni1 atom indicate that the nickel atom is in the center of a square plane. The molecular structure of complex 3 (Figure 3) is comparable with that of complex 2 in all of the structural data and the configuration information, with the difference being brought about by the halogen ligands.

Figure 3. Molecular structure of complex 3. The thermal ellipsoids are displayed at 20% probability, and hydrogen atoms are omitted for clarity. Only one disordered position was presented. Selected information on bond lengths (Å) and angles (deg): Ni1−C1 1.886(8), Ni1−P2 2.201(2), Ni1−P1 2.213(2), Ni1−Br1 2.308(1), C1−C2 1.22(2), C1−C3 1.53(2); C1−Ni1−P2 91.1(3), C1−Ni1−P1 90.9(3), P2−Ni1−P1 178.0(1), C1−Ni1−Br1 180.0(3), P2−Ni1−Br1 88.94(9), P1−Ni1−Br1 89.07(7).

Figure 2. Molecular structure of complex 2. The thermal ellipsoids are displayed at 20% probability, and hydrogen atoms are omitted for clarity. Selected information on bond lengths (Å) and angle s(deg): Ni1−Cl1 2.182(2), Ni1−P2 2.211(2), Ni1−P1 2.220(2), Ni1−C1 1.888(9), C1−C2 1.24(2), C1−C3 1.56(2); C1−Ni1−Cl1 179.6(3), C1−Ni1−P2 91.7(3), Cl1−Ni1−P2 88.8(1), C1−Ni1−P1 91.4(3), Cl1−Ni1−P1 88.1(1), P2−Ni1−P1 176.9(1), F2−C2−C1 147(2), F2−C2−F1 90(1), C1−C2−F1 117(2).

Reactions between Ni(C3F6)(PMe3)3 (1) and Brønsted Acids. In general, perfluoropropene complexed with electronrich nickel compounds with Lewis basic properties is able to participate in addition reactions with protonic acids.4a Several organic Brønsted acids were utilized in the reaction with complex 1 (Scheme 3). Both acetic acid as a weak acid and methanesulfonic acid as a strong acid reacted with complex 1 to afford the addition products, nickel(II) complexes 5 and 6. The 19 F NMR spectra indicate that no elimination of a fluorine atom was found. The configurations of complexes 5 and 6 were

Because of the disorder of the perfluoropropenyl ligand and the asymmetry of the structure, we only present one possible position of this ligand for the sake of clarity. The molecular structure of complex 2 further confirms that the geminal C−F bond of the trifluoromethyl group was exclusively activated in this reaction. The C1−C2 bond length (1.24(2) Å) is much shorter than that of C1−C3 (1.56(2) Å). Both are in accord with the fact that C1−C2 is a double bond and C1−C3 is a single bond. The sum of the three angles centered at the C2 7124


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Scheme 3. Reactions of Complex 1 with Brønsted Acids

Figure 4. Molecular structure of complex 5. The thermal ellipsoids are displayed at 20% probability, and hydrogen atoms at the PMe3 ligands are omitted for clarity. Selected information on bond lengths (Å) and angles (deg): Ni1−C3 1.905(3), Ni1−O1 1.908(2), Ni1−P2 2.2393(7), Ni1−P1 2.2461(6), C3−C2 1.534(3), C1−C2 1.513(4); C3−Ni1−O1 176.59(8), C3−Ni1−P2 93.48(7), O1−Ni1−P2 89.26(5), C3−Ni1−P1 94.48(7), O1−Ni1−P1 82.79(5), P2−Ni1− P1 172.04(3).

characterized by 1H, 19F, and 31P NMR spectra. The strong reactivity of the perfluoropropene ligand in complex 1 toward protonic acids for addition reactions might be caused by the strong π back-bonding from nickel to the olefin double bond. This back-bond is additionally supported by the strong electron donors, trimethylphosphine ligands. Since perfluoropropene is an unsymmetrical fluorinated olefin ligand, another problem in this kind of reaction is determining the position where the proton is added. From the 19 F NMR spectrum of complex 5, the fluorine atoms of the trifluoromethyl group are coupled with the geminal fluorine atom to give a doublet and the coupling constants are consistent with the regular trifluoromethyl-substituted fluoroalkane.4b In contrast to the reported addition reactions of fluorinated olefin coordinated to a Pt center with protonic acid,4a in which the hydrogen addition occurs at the higher fluoro-substituted carbon atom, in this case, the hydrogen atom was added to the lower fluorinated carbon atom, the 2-position of perfluoropropene. This reaction has two steps. First, the oxidative addition of the protonic acid took place at the Ni center to afford a hydrido nickel(II) intermediate after dissociation of two trimethylphosphine ligands. A direct protonation at the coordinated olefin is also conceivable for this reaction. The second step is the insertion of the π-coordinated perfluoropropene into the Ni−H bond.4b In the latter step, the hydrido hydrogen atom attached to the nickel atom bearing a formal negative charge would be added to the more electron-poor carbon atom of the CC bond. The strongly electron withdrawing trifluoromethyl group makes the carbon atom of the olefin double bonded to it more electron poor than another carbon atom of the olefin double bond. This result was confirmed by X-ray single-crystal diffraction analysis of complex 5. In the molecular structure of complex 5 (Figure 4), the 2hydrohexafluoropropyl ligand was clearly presented. As expected from the results of the NMR data, the hydrogen atom of acetic acid was added to the carbon atom connected with the trifluoromethyl group. The C1−C2 (1.513(4) Å) and C3−C2 bond lengths (1.534(3) Å) are in accordance with the bond length of a carbon−carbon single bond. Complex 5 has a square coordination geometry. The sum of four angles (C3− Ni1−P2 = 93.48(7)°, O1−Ni1−P2 = 89.26(5)°, C3−Ni1−P1 = 94.48(7)°, and O1−Ni1−P1 82.79(5)°) of 360.01° indicates that the four coordinated atoms and the central nickel atom are in the same plane. Interestingly, all seven atoms of the chain

[C5C4O1NiC3C2C1] are also in one plane, though it is winding. Surprisingly, no analogue to complexes 5 and 6 could be obtained upon reaction of trifluoroacetic acid with complex 1 (Scheme 3). Complex 7 was isolated as the C−F bond activation product. In the IR spectrum of complex 7, the stretching vibrations of the CC bond of the fluorinated propenyl ligand and the CO bond of the trifluoro carboxylate anion are recorded at 1693 and 1682 cm−1, respectively. As for the 19F NMR spectrum of complex 7, except for the trifluoromethyl group of the trifluoroacetate, the other chemical shifts and coupling constants have patterns similar to those of complex 2. This illustrates that the activated C−F bond retains the same position as in complex 2. The X-ray crystal structure confirmed that the selectivity of the C−F bond activation is similar to that of the reactions with Lewis acids (Scheme 3). The molecular structure of complex 7 (Figure 5) has a typical square coordination configuration of a Ni(II) complex. The CC bond length (C5−C6 = 1.371(5) Å) in complex 7 is much longer than those in complexes 2 (C1−C2 = 1.24(2) Å) and 3 (C1−C2 = 1.22(2) Å). This difference is caused by the trans ligand replacement of halogen (Cl (2) and Br (3)) by trifluoroacetate. In addition, the bond angles between the adjacent coordination bonds are ca. 90°. Interestingly, the acetate (C2C1O2O1) moiety and the Ni atom are in the olefin plane. The olefin plane is perpendicular to the coordination square plane. The atom arrangement (P1Ni1P2) is also perpendicular to the olefin plane containing the perfluoropropenyl ligand. Transmetalation of Complex 2 with Organometallic Reagents. Because of the existence of a Ni−X bond (X = Cl, Br, I) in complexes 2−4, the replacement reaction of a halide ligand by an alkyl group (hydrocarbylation) is possible. Complex 2 was utilized as a template for this research. In classic catalytic cross-coupling reactions of organic halides with organometallic reagents, such as the Kumada reaction,7 the mechanism includes three basic steps: oxidative addition, transmetalation, and reductive elimination. In this context, complex 2 can be considered as the oxidative addition product. Therefore, we concentrated on transmetalation and the possibility of reductive elimination. 7125


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Figure 5. Molecular structure of complex 7. The thermal ellipsoids are displayed at 20% probability, and hydrogen atoms are omitted for clarity. Selected information on bond lengths (Å) and angles (deg): Ni1−C5 1.899(3), Ni1−O1 1.906(2), Ni1−P2 2.217(1), Ni1−P1 2.2173(9), C5−C6 1.371(5), C5−C7 1.398(5); C5−Ni1−O1 173.7(1), C5−Ni1−P2 90.1(1), O1−Ni1−P2 89.98(7), C5−Ni1−P1 91.4(1), O1−Ni1−P1 89.36(7), P2−Ni1−P1 172.31(4), C6−C5−C7 117.7(4), C6−C5−Ni1 122.9(3), C7−C5−Ni1 119.3(3), F4−C6−C5 123.2(7), F5−C6−C5 127.8(5), F4−C6−F5 108.3(7).

Figure 6. Molecular structure of complex 8. The thermal ellipsoids are displayed at 20% probability, and hydrogen atoms are omitted for clarity. Selected information on bond lengths (Å) and angles (deg): Ni1−C4 1.912(2), Ni1−C1 1.956(2), Ni1−P2 2.1853(7), Ni1−P1 2.1863(7), C1−C2 1.352(3), C1−C3 1.422(4); C4−Ni1−C1 179.9(1), C4−Ni1−P2 87.14(6), C1−Ni1−P2 92.87(6), C4−Ni1− P1 87.45(6), C1−Ni1−P1 92.53(6), P2−Ni1−P1 174.58(2), C2− C1−C3 115.9(2), C2−C1−Ni1 121.2(2), C3−C1−Ni1 122.9(2), F2A−C2−C1 127.3(4), F1A−C2−F2A 108.1(4), F1A−C2−C1 124.3(3).

When phenylmagnesium bromide in THF was added to a diethyl ether solution of complex 2, a large amount of sediment was produced, which is the magnesium salt MgBrCl (Scheme 4). The solution turned brown. Complex 8 was crystallized as

perpendicular to the coordination square plane and the atom arrangement P1−Ni1−P2 due to steric effects. The reaction of complex 2 with (4-methoxyphenyl)magnesium bromide in diethyl ether at room temperature afforded complex 9 as yellow crystals. The IR spectrum shows a strong CC stretching vibration absorption at 1685 cm−1. In comparison to that (1694 cm−1) of complex 2, this red shift was probably caused by the electron-donating properties of the pmethoxylphenyl ligand. The 19F NMR data are in accord with the expected complex 9. The single crystals of complex 9 recrystallized from n-pentane were used for X-ray crystal analysis. Complex 9 (Figure 7) has a configuration similar to that of complex 8. The small difference in some bond parameters was caused by the p-methoxy group in complex 9. For example, the double-bond length of C1−C2 in complex 9 (1.318(6) Å) is

Scheme 4. Transmetalation of Complex 2 with Organometallic Reagents

light yellow crystals from n-pentane at 0 °C. The configuration of complex 8 was confirmed with the 19F, 1H, and 31P NMR spectra. The IR spectrum of complex 8 showed C−H and C C bands at 3043 and 1682 cm−1. The molecular structure of 8 was confirmed by X-ray singlecrystal diffraction (Figure 6). The C1−C2 bond length (1.352(3) Å) is longer than that of C1−C2 in complex 2 (1.24(2) Å), but it is comparable with that of C5−C6 in complex 7 (1.371(5) Å). The sums of the bond angles centered at both C1 and C2 are around 360°. This explains the sp2 plane structure of the perfluoropropenyl group. The dihedral angle between the plane containing C1, C2, C3, F1A, and F2A and the phenyl plane is 4.6°. This implies that the perfluoropropenyl group frame (C2C1C3) and the central Ni atom (Ni1) are almost in the plane of the phenyl group. This plane is

Figure 7. Molecular structure of complex 9. The thermal ellipsoids are displayed at 20% probability, and hydrogen atoms are omitted for clarity. Selected information on bond lengths (Å) and angles (deg): Ni1−C10 1.934(4), Ni1−C1 1.962(4), Ni1−P1 2.188(1), Ni1−P2 2.191(1), C1−C2 1.318(6), C1−C3 1.444(6); C10−Ni1−C1 177.1(2), C10−Ni1−P1 87.1(1), C1−Ni1−P1 92.5(1), C10−Ni1− P2 87.3(1), C1−Ni1−P2 93.0(1), P1−Ni1−P2 174.21(5), C1−C2− F2 129.4(4), C1−C2−F1 122.7(4), F2−C2−F1 107.8(4). 7126


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phosphine ligands. The structure of complex 11 was determined by X-ray single-crystal analysis. As shown in Figure 9, the C8−C9 bond length (1.329(6) Å) as a CC bond is significantly shorter than those of C7−C8

shorter than that (1.352(3) Å) in complex 8. The dihedral angle between the alkenyl and the phenyl plane in complex 9 is 1.5°, which is less than that (4.6°) in complex 8. To expand this study, an organolithium reagent, phenylethynyllithium, was also utilized to perform this transmetalation reaction with complex 2 in Et2O at room temperature. As expected, complex 10 was obtained as light yellow crystals. In the IR spectrum, the vibrations for the CC bond of the phenylethynyl group and the CC bond of the perfluoropropenyl ligand were recorded at 2097 and 1692 cm−1, respectively. Similarly, a single peak in the 31P NMR spectrum of complex 10 signifies the trans-orientation of the two phosphine ligands. The highly ordered 19F NMR spectrum of complex 10 indicates the perfluoropropenyl ligand. In the molecular structure of complex 10 (Figure 8), the C10−C11−C12 bond angle (176.9(14)°) shows the existence

Figure 9. Molecular structure of complex 11. The thermal ellipsoids are displayed at 20% probability, and hydrogen atoms on the PMe3 ligands are omitted for clarity. Selected information on bond lengths (Å) and angles (deg): C7−C8 1.437(7), C8−C9 1.329(6), C9−C10 1.535(6), Ni1−P2 2.202(2), Ni1−P1 2.210(1), C9−Ni1 1.884(5), Br1−Ni1 2.3640(8); C9−Ni1−P2 89.5(2), C9−Ni1−P1 90.3(2), P2− Ni1−P1 176.66(6), C9−Ni1−Br1 174.9(1), P2−Ni1−Br1 89.92(4), P1−Ni1−Br1 90.52(4), C8−C9−C10 121.1(4), C8−C9−Ni1 127.2(4), C10−C9−Ni1 111.6(3).

(1.437(7) Å), C9−C10 (1.535(6) Å), and C10−C11 (1.491(6) Å), which belong to single bonds. The sum of the three bond angles with the C9 atom in the center is 360.2°. This illustrates that the four atoms (C8C9C10Ni1) are in the same plane. Although there is no conjugation between the olefin moiety and the phenylethyl group because of the −CH2CH2− chain, the phenylethyl carbon frame is almost in the olefin sp2 plane. This might be a result of packing effects in the crystallization process. The molecular structure information is consistent with the spectroscopic data. In order to understand the mechanism of this transformation, operando IR was utilized to monitor the reaction process. The reaction container was charged with complex 2 in THF. To this solution was added a THF solution of phenylethylmagnesium bromide. As shown in Scheme 6, as the reaction proceeds, the strong IR absorption (1698 cm−1) for the CC bond of complex 2 becomes weaker with the signal (1680 cm−1) enhancement. This indicates the existence of the intermediate 11a (Scheme 7), similar to the case for complexes 8−10. However, after about 0.5 h, this peak disappeared. At the same time, a new peak at 1601 cm−1 was formed and slowly grew. On the basis of the IR spectra of complex 11, there is an obvious absorption band at around 1600 cm−1, which is in accord with the new peak. Through further analysis of the operando IR data collected, the kinetic characters of the reaction were clearly revealed (Scheme 6b). The developments of the concentrations of different components versus time were clearly reflected. Three components (complex 2, intermediate 11a, and complex 11) existing during the reaction process were successfully caught. The concentration of complex 2 decreased immediately after addition of phenethylmagnesium bromide. With the consumption of complex 2, the formation of 11a accelerated and reached the highest concentration with the exhaustion of complex 2. Obviously, from the development of concentration,

Figure 8. Molecular structure of complex 10. The thermal ellipsoids are displayed at 20% probability, and hydrogen atoms are omitted for clarity. Selected information on bond lengths (Å) and angles (deg): Ni1−C10 1.852(3), Ni1−C2 1.922(3), Ni1−P1 2.177(3), Ni1−P2 2.188(3), C10−C11 1.193(4), C2−C3 1.35215, C2−C1 1.41(2); C11−C10−Ni1 178(1), C10−C11−C12 177(1), C10−Ni1−C2 178.7(6), C10−Ni1−P1 86.5(3), C2−Ni1−P1 93.3(4), C10−Ni1− P2 86.0(3), C2−Ni1−P2 94.3(4), P1−Ni1−P2 172.42(4).

of an ethynyl group with bond length C10−C11 (1.193(4) Å). Interestingly, due to the linear structure of the ethynyl group (less repulsion), the two PMe3 groups are almost in an eclipsed conformation in complex 10 while the two PMe3 ligands are in a skew conformation in complexes 8 and 9. Successive C−F Bond Activation Reactions. Unexpectedly, the reaction of complex 2 with phenylethylmagnesium bromide gave rise to complex 11 via double C−F bond activation (Scheme 5). The reaction proceeded in diethyl ether Scheme 5. Successive C−F Bond Activation of Complex 2 with Phenylethynyl Bromide

at room temperature and was complete within about 3 h. Only one signal at −57.3 ppm for the −CF3 group was observed in the 19F NMR spectrum of complex 11. This indicates that both sp2 C−F bonds were activated and functionalized. The 31P and 1 H NMR spectra show the existence of two trans-oriented 7127


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Scheme 6. Operando IR Results for the Functionalization Reaction: (a) Three-Dimensional Fourier Transform IR (3DFT-IR) Profiles; (b) Kinetic Profiles

phenylethyl group, styrene as a byproduct of the reaction was caught with GC-MS. This also indirectly proves the transmetalation process and the formation of 11a. The process of formation of 11b from complex 2 is similar to the mechanism of rhodium-catalyzed silylation of hexafluoropropene.3i However, in this work, no elimination reaction occurred because of the strong electron-donating ability of PMe3. As the end product, complex 11 should be formed from intermediate 11e with the promotion of Lewis acid MgBrX (X = Cl, F). There might be two possible paths for the formation of 11e from 11b. In path 1, intermediate 11c, a π-coordinated olefin nickel(0) complex, can be formed through reductive elimination of Ni−H and Ni−Colefin bonds. The first C−F bond activation of the olefin ligand in 11c delivers 11e through nucleophilic substitution by a phenylethyl group. However, 11c is more electron rich than complex 2. No nucleophilic substituation was observed in the reactions of complex 2 with phenylmagnesium

11a could be considered as an intermediate for this reaction. The new peak at 1601 cm−1 could be assigned to complex 11. In short, 11a is a labile intermediate in this reaction and the formation of 11a might be the rate-determining step in the mechanism. In the in situ 1H NMR spectrum of the reaction in Scheme 5, a triplet signal at −12.55 ppm was observed. This implies that one intermediate could be a nickel hydride with a NiII−H functional group.8 According to the information of operando IR, the in situ 1H NMR spectra, and the results of formation of complexes 8−10, we proposed a mechanism for this reaction (Scheme 7). First, phenylethylmagnesium bromide conducted a transmetalation reaction with complex 2 to afford the intermediate 11a, which was identified through operando IR. Second, 11a transformed to the hydrido intermediate 11b via β-H elimination with the escape of styrene. As evidence for β-H elimination of the 7128


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Scheme 7. Proposed Reaction Mechanism of the Formation of Complex 11

the C−F bond activation processes were structurally characterized by X-ray single-crystal diffraction.

bromide or even with phenylethynyllithium. In other words, it is hardly possible for 11c to conduct a nucleo-substitution reaction with phenylethylmagnesium bromide to afford 11e. Another possibility in path 2 is that the nucleophilic substitution occurs before reductive coordination. The hydrido nickel(II) complex 11b is comparably electron poor. The nucleophilic reaction of 11b with phenylethylmagnesium bromide might proceed smoothly. After nucleophilic attack 11d can be produced by the first C−F bond activation, followed by reductive elimination and π-coordination of the olefin ligand to give rise to 11e. Finally, the formation of complex 11 can be realized via the second C−F bond activation of the olefin ligand in 11e in the presence of the Lewis acid MgBrCl. In the last step, the nickel(0) center in 11e is oxidized to a nickel(II) species in complex 11.

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EXPERIMENTAL SECTION

General Methods. All operations were conducted utilizing standard Schlenk techniques under a nitrogen atmosphere. Toluene, diethyl ether, pentane, and THF were dried by distillation from Na− benzophenone. C6D6 for NMR was degassed and processed with zeolite. Ni(PMe3)4 was prepared according to a previous report.9 All other reagents were utilized without further purification. 1H, 31P, and 19 F NMR spectra were recorded on a Bruker NMR Avance spectrometer at 300 MHz. IR spectra were recorded on a Bruker ALPHA FT-IR instrument from Nujol mulls between KBr disks. GCMS were measured on a TRACE-DSQ instrument. The operando IR spectra were recorded with IC 10 and IC 15 instruments from MettlerToledo Auto Chem. iC version 4.2 IR software was utilized to carry out the data treatment. X-ray crystallography was performed with a Bruker Smart 1000 diffractometer. Melting points were measured in capillaries sealed under N2 and were uncorrected. Elemental analyses were carried out on an Elementar Vario ELIII instrument. Ni(C3F6)(PMe3)3 (1). Excess hexafluoropropene was condensed (−196 °C) into a solution of Ni(PMe3)4 (0.50 g, 1.37 mmol) in toluene. The mixture became purple. When the reaction mixture was warmed to room temperature, it turned light yellow and then dark red. After 12 h, the volatiles were removed under vacuum. n-Pentane was used to extract the residue. Orange crystals of complex 1 (0.51 g, 80% yield) were obtained from pentane at −20 °C. Mp: 100−101 °C. IR (Nujol, cm−1): 941.6 ν(PMe3). 1H NMR (300 MHz, C6D6, 298 K, δ/ ppm): 1.02 (d, JPF = 6.0 Hz, PCH3). 31P{1H} NMR (121 MHz, C6D6, 298 K, δ/ppm): −19.25 (s, PMe3). 19F NMR (282 MHz, C6D6, 298 K, δ/ppm): −63.8 (dm, JPF = 7.1 Hz, 3F, −CF3), −98.5 (dd, 2JFF = 155.1 Hz, 3JFF = 28.2 Hz, 1F, −C(CF3)CFF), −102.4 (dd, 2JFF = 155.1 Hz, 3JFF = 87.4 Hz, −C(CF3)CFF), −191.2 (d, 3JFF = 70.5 Hz, −CFCF2). Anal. Calcd for C12H27F6NiP3 (436.96): C, 32.98; H, 6.23. Found: C, 32.51; H, 6.32. NiX(F3CCCF2)(PMe3)2 (X = Cl (2), Br (3), I (4)). A suspension of Lewis acid (1.1 equiv of ZnCl2 for 2, LiBr for 3, and LiI for 4) in THF was added to a THF solution of complex 1 (0.3 g, 0.66 mmol). The mixture was vigorously stirred for 4 h at room temperature. The

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CONCLUSION To sum up, we demonstrated the C(sp2)−F bond activation of perfluoropropene with Ni(PMe3)4 with the promotion of a Lewis acid (ZnCl2, LiBr, and LiI) and a protonic acid (CF3COOH) with special selectivity. Through transmetalation reactions between the C−F bond activation product and Grignard reagents or organolithium reagents, a series of organonickel complexes with a 2-perfluoropropenyl ligand were obtained. A double C−F bond activation reaction with phenylethylmagnesium bromide as the functional reagent was studied. This is the first example of hydrodefluorination and carbon−carbon cross-coupling reactions occurring within the same fluoroalkenyl group, more importantly without violation of the CC bond. A reasonable mechanism was proposed and partially experimentally verified through operando IR and in situ 1H NMR spectroscopy. This reaction may open up an extraordinary concept for construction of particular organic frames containing fluorine atoms from cheap perfluorinated chemical substances. The main nickel complexes involved in 7129


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=12.4 Hz, 4JPF =6.2 Hz, −CCFF). Anal. Calcd for C11H18F8NiO2P2 (454.90): C, 29.04; H, 3.99. Found: C, 28.67; H, 3.78. Ni(C6H5)(F3CCCF2)(PMe3)2 (8). PhMgBr (0.53 mL, 1.0 mol/L) as a THF solution was combined with a diethyl ether solution of complex 2 (0.2 g, 0.53 mmol) under −78 °C. After the mixture was stirred for 8 h at room temperature, a white powder of the magnesium salt precipitated from the solution. The solution appeared light yellow. After all the volatiles were removed, the residue was extracted with npentane. Complex 8 (0.17 g, 75% yield) was obtained as yellow crystals at 0 °C. Mp: 127−128 °C. IR (Nujol, cm−1): 1682 ν(CC), 950 ν(PMe3). 1H NMR (300 MHz, C6D6, 298 K, δ/ppm): 0.81 (t′, JPH = 4.2 Hz, 18H, PCH3), 6.96 (m, 1H, Ar-H), 7.05−7.11 (m, 2H, ArH), 7.29−7.42 (m, 2H, Ar-H). 31P{1H} NMR (121 MHz, C6D6, 298 K, δ/ppm): −12.7 (s, PMe3). 19F NMR (282 MHz, C6D6, 298 K, δ/ ppm): −46.81 (t′, 4JFF = 13.0 Hz, 3F, −CF3), −57.6 (dqt, 2JFF = 57.8 Hz, 4JFF = 13.0 Hz, JPF = 6.5 Hz, 1F, CCFF), −79.1 (dqt, 2JFF = 57.8 Hz, 4JFF =12.7 Hz, 4JPF =4.2 Hz, −CCFF). Anal. Calcd for C15H23F5NiP2 (418.98): C, 43.00; H, 5.53. Found: C, 42.77; H, 5.72. Ni(p-MeO−C6H5)(F3CCCF2)(PMe3)2 (9). To a sample of complex 2 (0.2 g, 0.53 mmol) in diethyl ether was added (4methoxyphenyl)magnesium bromide (0.53 mL, 1.0 mol/L THF solution) under −78 °C. The reaction solution was stirred for 6 h at room temperature. A white powder appeared in the solution. After removal of the solvent under vacuum, the residue was extracted three or four times with n-pentane. Complex 9 (0.19 g, 78% yield) as yellow crystals was isolated from the combined n-pentane solution at 0 °C. Mp: 129−131 °C. IR (Nujol, cm−1): 1685 ν(CC), 948 ν(PMe3). 1H NMR (300 MHz, C6D6, 298 K, δ/ppm): 0.82 (s, 18H, PCH3). 3.52 (s, 3H, −OCH3), 6.95 - 6.83 (m, 2H, Ar-H), 7.16 (d, 3JHH = 7.1 Hz, 1H), the signal of the fourth Ar-H atom was overlapped with the signals of C6D6. 31P{1H} NMR (121 MHz, C6D6, 298 K, δ/ppm): −13.0 (s, PMe3). 19F NMR (282 MHz, C6D6, 298 K, δ/ppm): −46.8 (t′, 4JFF = 13.2 Hz, 3F, −CF3), −57.8 (dqt, 2JFF = 58.1 Hz, 4JFF = 13.2 Hz, JPF = 5.9 Hz, 1F, −CCFF), −79.2 (dqt, 2JFF = 58.1 Hz, 4JFF =12.7 Hz, JPF = 4.2 Hz, 1F, −CCFF). Anal. Calcd for C16H25F5NiOP2 (449.01): C, 42.80; H, 5.61. Found: C, 42.37; H, 5.46. Ni(C6H5CC)(F3CCCF2)(PMe3)2 (10). To a solution of complex 2 (0.2 g, 0.53 mmol) in diethyl ether was added (phenylethynyl) lithium (1.06 mL, 0.5 mol/L) in THF with stirring at 0 °C. The reaction mixture turned from yellow to dark brown with the precipitation of a white powder. After the mixture was stirred at room temperature for 24 h, the volatiles were removed from the solution under lowered pressure. The residue was extracted three times with n-pentane to give a brown solution. Complex 10 (0.17 g, 73% yield) as light yellow crystals was obtained from the pentane solution at 0 °C. Mp: 136−137 °C. IR (Nujol, cm−1): 1682 ν(CC), 2097 ν(CC), 948 ν(PMe3). 1H NMR (300 MHz, C6D6, 298 K, δ/ ppm): 1.19 (s, 18H, PCH3). 7.11 (tm, 3JHH = 7.5 Hz, 1H, Ar-H), 7.23 (tm, 3JHH = 7.2 Hz, 2H, Ar-H), 7.55 (dm, 3JHH = 5.1 Hz, 2H, Ar-H). 31 1 P{ H} NMR (121 MHz, C6D6, 298 K, δ/ppm): −8.6 (s, PMe3). 19F NMR (282 MHz, C6D6, 298 K, δ/ppm): −46.8 (t′, 4JFF = 12.7 Hz, 3F, −CF3), −57.8 (dqt, 2JFF = 53.6 Hz, 1F, −CCFF), −78.3 (dm, 2JFF = 53.6 Hz, 1F, −CCFF). Anal. Calcd for C17H23F5NiP2 (443.00): C, 46.09; H, 5.23. Found: C, 45.77; H, 5.06. (CF3CHC(CH2CH2C6H5))NiBr(PMe3)2 (11). Complex 2 (0.2 g, 0.53 mmol) in 10 mL of diethyl ether was combined with (phenylethyl)magnesium bromide (1.06 mL, 1.0 mol/L THF solution) under 0 °C. After the mixture was stirred for 12 h at room temperature, a large amount of white powder precipitated from the solution. The reaction solution turned from yellow to yellowgreen. After removal of the volatiles, the residue was extracted with npentane. Complex 11 (0.21 g, 81% yield) was isolated from the pentane solution at 0 °C. Mp: 117−119 °C. IR (Nujol, cm−1): 1599 ν(CC), 947 ν(PMe3). 1H NMR (300 MHz, C6D6, 298 K, δ/ppm): 7.36−7.28 (m, 2H, Ar-H), 7.22 (m, 3H, Ar-H), 5.87−5.56 (m, 1H, CCH), 2.93 (m, 2H, Ph−CH2), 2.79 - 2.59 (m, 2H, −CH2), 1.14 (t, JPH = 3.8 Hz, 18H, PCH3). 31P{1H} NMR (121 MHz, C6D6, 298 K, δ/ ppm): −13.6 (q, JPF = 7.3 Hz, PMe3). 19F NMR (282 MHz, C6D6, 298 K, δ/ppm): −57.3 (t, 4JPF = 7.3 Hz, −CF3). 13C NMR (75 MHz, C6D6, 298 K, δ/ppm): 142.1 (s), 128.7 (s), 128.2 (s), 126.2 (s), 114.7 (qm,

solvent was removed under reduced pressure, and the residue was extracted with n-pentane. The reaction products were crystallized from the solution at −20 °C. Complex 2: 92% yield; Mp 140−142 °C; IR (Nujol, cm−1) 1694 ν(CC), 947.7 ν(PMe3); 1H NMR (300 MHz, C6D6, 298 K, δ/ppm) 1.02 (t′, JPH = 9 Hz, PCH3). 31P{1H} NMR (121 MHz, C6D6, 298 K, δ/ppm): −15.4 (s, PMe3); 19F NMR (282 MHz, C6D6, 298 K, δ/ ppm): −48.1 (ddt, 4JFF = 16.1 Hz, 4JFF = 11.8 Hz, JPF = 1.1 Hz, 3F, −CF3), −57.9 (dqt, 2JFF = 56.4 Hz, 4JFF = 16.4 Hz, JPF = 5.6 Hz, 1F, −C(CF3)CFF), −77.6 (dqt, 2JFF = 56.4 Hz, 4JFF = 16.9 Hz, −C(CF3)CFF). Anal. Calcd for C9H18ClF5NiP2 (377.33): C, 28.65; H, 4.81. Found: 29.11; H, 5.02. Complex 3: 95% yield; Mp 144−145 °C. IR (Nujol, cm−1): 1694 ν(CC), 947.7 ν(PMe3); 1H NMR (300 MHz, C6D6, 298 K, δ/ppm) 1.04 (t′, JPH = 9 Hz, PCH3); 31P{1H} NMR (121 MHz, C6D6, 298 K, δ/ppm) −15.5 (s, PMe3); 19F NMR (282 MHz, C6D6, 298 K, δ/ppm) −48.1 (ddt, 4JFF = 16.4 Hz, 4JFF = 11.8 Hz, 3F, −CF3), −57.7 (dqt, 2JFF = 53.9 Hz, 4JFF = 16.4 Hz, JPF = 5.6 Hz, 1F, −C(CF3)CFF), −77.5 (dqt, 2JFF = 47.9 Hz, 4JFF =12.1 Hz, −C(CF3)CFF). Anal. Calcd for C9H18BrF5NiP2 (421.79): C, 25.63; H, 4.30. Found: C, 25.21; H, 4.42. Complex 4: 90% yield; Mp 152−153 °C; IR (Nujol, cm−1) 1695 ν(CC), 948.2 ν(PMe3); 1H NMR (300 MHz, C6D6, 298 K, δ/ppm) 1.17 (t′, JPH = 3.9 Hz, PCH3); 31P{1H} NMR (121 MHz, C6D6, 298 K, δ/ppm) −15.5 (s, PMe3); 19F NMR (282 MHz, C6D6, 298 K, δ/ppm) −48.1 (dd, 4JFF = 16.4 Hz, 4JFF = 11.8 Hz, 3F, −CF3), −57.9 (dqt, 2JFF = 53.4 Hz, 4JFF = 16.4 Hz, JPF = 5.9 Hz, 1F, −C(CF3)CFF), −77.6 (dqt, 2JFF = 53.4 Hz, 4JFF = 18.0 Hz, −C(CF3)CFF). Anal. Calcd for C9H18F5INiP2 (468.78): C, 23.06; H, 3.87. Found: C, 22.81; H, 4.11. Ni(CF2CFHCF3)(CH3COO)(PMe3)2 (5). CH3COOH (0.05 g, 0.83 mmol) was added to an Et2O solution of complex 1 (0.2 g, 0.44 mmol). The reaction was conducted at room temperature for around 3 h. The volatiles were removed under low pressure. n-Pentane was used to extract the residues. The product was obtained as yellow crystals from a pentane solution at −10 °C (0.15 g, 80% yield). Mp: 102−103 °C. IR (Nujol, cm−1): 1612 ν(CO), 949.8 ν(PMe3). 1H NMR (300 MHz, C6D6, 298 K, δ/ppm): 0.99 (d, JPH = 6 Hz, 18H, PCH3), 1.96 (s, 3H, −CH3), 4.87 (m, 1H, −CH). 31P{1H} NMR (121 MHz, C6D6, 298 K, δ/ppm): −12.6 (m, PMe3). 19F NMR (282 MHz, C6D6, 298 K, δ/ppm): −72.3 (d, 3JFF = 8.5 Hz, 3F, −CF3), −79.6 to −82.9 (m, 2F, −CF2), −194.5 (m, −CHF). Anal. Calcd for C11H22F6NiO2P2 (420.94): C, 31.39; H, 5.27. Found: C, 31.01; H, 5.41. Ni(CF2CFHCF3)(CH3SO3)(PMe3)2 (6). Complex 1 (0.25 g, 0.55 mmol) was dissolved in THF. CH3SO3H (0.06 g, 0.61 mmol) was added dropwise to this solution at 0 °C. The mixture became lighter. After the temperature was raised to room temperature for around 3 h, the volatiles were removed under low pressure. The residue was washed three times with 15 mL of n-pentane and extracted with 30 mL of Et2O. Complex 6 (0.21g, 83% yield) was crystallized from the Et2O solution at −20 °C. Mp: 105−106 °C. IR (Nujol, cm−1): 953 ν(PMe3). 1H NMR (300 MHz, C6D6, 298 K, δ/ppm): 0.50 (d, JPH = 11.8 Hz, 9H, PCH3), 2.24 (s, 3H, −CH3), 5.1 (dm, JFH = 45.0 Hz, 1H, −CH). 31P{1H} NMR (121 MHz, C6D6, 298 K, δ/ppm): −13.0 (m, PMe3). 19F NMR (282 MHz, C6D6, 298 K, δ/ppm): −72.6 (dd, 3JHF = 20.7 Hz, 3JFF = 8.6 Hz, 3F, −CF3), −91.1 to −95.2 (m, 2F, −CF2), −206.5 (m, 1F, −CHF). Anal. Calcd for C7H13F6NiO3PS (380.90): C, 22.07; H, 3.44. Found: C, 21.71; H, 3.60. Ni(OCOCF3)(F3CCCF2)(PMe3)2 (7). To an Et2O (20 mL) solution of complex 1 (0.25 g, 0.55 mmol) was added CF3COOH (0.07 g, 0.61 mmol) at −20 °C. The mixture was allowed to react at room temperature for 2 h with a color change from yellow to light yellow. The volatiles were removed under vacuum. The residue was extracted with n-pentane. Crystals of complex 7 (0.22 g, 87% yield) were obtained under 0 °C. Mp: 135−136 °C. IR (Nujol, cm−1): 1682 ν(CO), 1693 ν(CC), 948 ν(PMe3). 1H NMR (300 MHz, C6D6, 298 K, δ/ppm): 0.81 (t′, JPH = 4.2 Hz, 18H, PCH3). 31P{1H} NMR (121 MHz, C6D6, 298 K, δ/ppm): −16.9 (s, P, PMe3). 19F NMR (282 MHz, C6D6, 298 K, δ/ppm): −47.5 (t′, 4JFF = 12.6 Hz, 3F, −CF3), −54.9 (dqt, 2JFF = 49.1 Hz, 4JFF = 12.7 Hz, JPF = 2.5 Hz, 1F, −C CFF), −74.1 (s, 3F, −C(O)CF3), −77.7 (dqt, 2JFF = 49.1 Hz, 4JFF 7130


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2

JCF = 30 Hz), 43.6 (s), 35.5 (s), 40.0 (s), 13.7 (t′, 1JPF = 14.1 Hz), the signal for the carbon atom of CF3 group was not observed. Anal. Calcd for C17H28BrF3NiP2 (489.95): C, 41.67; H, 5.76. Found: C, 42.15; H, 5.59. Experiment To Confirm the Mechanism of the Formation of Complex 11. According to the preparation procedure of complex 11, after the reaction was complete, the original solution was quenched with water and extracted with diethyl ether. Styrene was confirmed from the resulting solution by a GC-MS test (m/z 103.9). General Procedure of the in Situ 1H NMR Experiment. In a sample of complex 2 (10.0 mg, 0.026 mmol) in C6D6 (0.4 mL), a THF (0.1 mL, 0.5 mol/L) solution of (phenylethyl)magnesium bromide was injected at −78 °C. The 1H NMR test was performed at room temperature. A signal for the hydrido hydrogen atom was found at −12.55 ppm (t, 2JPH = 6.0 Hz, Ni−H). General Procedure of the IR Kinetic Experiment. Complex 2 (0.22 g) in 5 mL of THF was charged into a two-necked Schlenk tube which had been connected with the Schlenk line. Through an adapter, the test probe was emerged into the solution. After the operando IR spectrometer was started to record the reaction signal, the (phenylethyl)magnesium bromide in THF solution was added dropwise at −78 °C. After 50 min at this temperature, the solution was warmed to room temperature. The operando IR spectra were continually recorded until the reaction was completed. X-ray Crystal Structure Determinations. Single crystals of all of the complexes for X-ray single-crystal diffraction were obtained from their n-pentane solutions at low temperature. Diffraction data were collected on a Bruker SMART Apex II CCD diffractometer equipped with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å). During collection of the intensity data, no significant decay was observed. The intensities were corrected for Lorentz−polarization effects and empirical absorption with the SADABS program.10 The structures were resolved by direct or Patterson methods with the SHELXS-97 program and were refined on F2 with SHELXTL.11 All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were included in calculated positions and were refined using a riding model. A summary of crystal data, data collection parameters, and structure refinement details is given in the Supporting Information. CCDC 927890−927896 and 931719 for complexes 2, 3, 7−11, and 5 contain supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Center via www.ccdc.cam.ac.uk/data_ request/cif.

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AUTHOR INFORMATION

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S Supporting Information *

CIF files and a table giving crystallographic data for 1−3, 7−11, and 5 and figures giving the original IR, 31P NMR, 1H NMR, 19 F NMR, and GC-MS spectra of the complexes and intermediates. This material is available free of charge via the Internet at http://pubs.acs.org. Corresponding Author

*E-mail for X. L.: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We gratefully acknowledge support by the NSF of China (No. 21172132). We also acknowledge the kind assistance of Prof. Dieter Fenske and Dr. Olaf Fuhr (Karlsruhe Nano-Micro Facility (KNMF), KIT) in the X-ray diffraction analysis.

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REFERENCES

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