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. 2024 Mar 14;43(6):706–712. doi: 10.1021/acs.organomet.4c00029

Nickel Perfluoroalkyl Complexes Supported by Simple Acetate Coligands

Cherry Mae T Ravidas †, Scott T Shreiber †, Lukas Kletsch ‡, Axel Klein ‡,*, David A Vicic †,*
PMCID: PMC10966735  PMID: 38550879

Abstract

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The interaction of tetramethylammonium acetate with [(MeCN)2Ni(CF3)2], [(MeCN)2Ni(C2F5)2], and [NMe4][(MeCN)Ni(CF3)3] was explored by 19F NMR spectroscopy. We show that depending on the nature of the nickel complex, one or two acetate ligands can add to the metal center and replace the nickel-bound MeCN ligands, depending on the acetate concentration. The number of acetates that could bind to nickel, and whether the resulting complex exists as a monomer or dimer, was determined to be dependent on the nature of the fluoroalkyl ligand. Moreover, we observe that oxidation of the nickel center of [(MeCN)2Ni(CF3)2] in the presence of two equivalents of acetate leads cleanly to the octahedral, paramagnetic (EPR spectroscopy), and anionic Ni(III) complex [NMe4][Ni(CF3)2(OAc)2].

Introduction

Nickel is a promising metal for the development of new fluoroalkylation reactions.1−3 The relatively weak nickel–carbon(fluoroalkyl) bond, coupled with the accessibility of an array of oxidation states, leaves much room for exploring ways to manipulate fluoroalkyl groups with nickel. Oftentimes, such exploratory studies involve understanding the dependence of the coordinating ligand (sterics and electronics) on reactivity. Polydentate phosphines, imines, and amines have historically provided robust platforms for isolating and studying well-defined nickel fluoroalkyl complexes. More recently, efforts have focused on using simple and less expensive solvents or coordinating counterions as ligands for stabilizing complexes of nickel in hopes of making fluoroalkylation reactions more universal. Chart 1 provides select examples of recently prepared trifluoromethylnickel complexes, in varying oxidation states, bearing simple ligands such as acetonitrile (MeCN), pyridine (Py), fluoride, and sulfate. Complexes 4 and 7 are interesting examples of how anionic species that typically behave as counterions can support trifluoromethyl nickel while imparting a formal charge to the overall complex. We were curious whether acetates may also support such structures as acetates are readily available, tunable, and structurally unique relative to the supporting ligands in Chart 1. Acetates are also simple ligands compared with CO, phosphines, or carbenes in that they are not known to stabilize, to a relatively large extent, lower oxidation state metals by π-backbonding or higher oxidation state counterparts by σ-donation. Acetates may also display noninnocent behavior that could be useful for C–H activation studies involving hydrogen atom transfers.6

Chart 1. Select Examples of Ni(II),3−5 Ni(III),4 and Ni(IV)2−4 Trifluoromethyl Complexes Supported by Simple Solvent or Counterion Coligands.

Chart 1

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In prior reports, we disclosed that aryl iodonium salts react with 2 to afford trifluoromethylated arenes.2,3 An unpublished expansion of those studies, and careful analysis of the trace byproducts using (diacetoxyiodo)benzene as the oxidant, indeed revealed that simple acetates may also serve as supporting ligands for trifluoromethyl nickel compounds. Here, we describe in detail the interactions of acetates with trifluoromethylnickel derivatives and investigate the effects of oxidation state and fluoroalkyl ligand identity on the molecular structure of the resulting compounds.

Results and Discussion

Reaction of the acetonitrile-solvated nickel trifluoromethyl complex 1 with tetramethylammonium acetate led to the precipitation of the formally Ni(II) diacetato complex 9 (Scheme 1). This reaction demonstrates that simple acetates can participate in displacement reactions with nickel-bound MeCN ligands to afford discrete anionic complexes. Single-crystal X-ray analysis of 9 (Figure 1) reveals its dimeric structure supported by two acetates that bridge the nickel centers. The dimer possesses a short nickel–nickel separation of 2.851(2) Å, not uncommon in other nickel complexes bearing bridging acetates.7 The two trifluoromethyl ligands on nickel in 9 are trans to the acetate oxygen atoms, affording an overall square-planar geometry at the nickel atoms. Formally, the addition of one anionic acetate ligand per nickel affords a dimer with an overall minus two charge, balanced by the two tetramethylammonium counterions. Interestingly, addition of excess equivalents of tetramethylammonium acetate to either 1 or 9 leads to the growth of a new signal in the 19F NMR spectrum at δ = −27.6 (Figure 2). We tentatively attribute this new species to the nickel(II) diacetato complex 10 (Scheme 1), in either its monomeric or dimeric form. An analysis of the infrared spectra reveals the appearance of two bands in the C=O stretching region after the addition of 1.5 equiv of tetramethylammonium acetate to 1 (see Supporting Information), consistent with the assignments outlined in Scheme 1. We observed 77% conversion of 1 to 10 using ten equivalents of acetate ion (Figure 2) at 3.6 mM in MeCN solution, which hindered the isolation of pure material and X-ray characterization of 10.

Scheme 1. Reactivity of 1 with Varying Amounts of Acetate and Oxidant.

Scheme 1

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Figure 1.

Figure 1

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ORTEP diagram of 9. Selected bond lengths (Å): Ni1–C2 1.88(2); Ni1–C1 1.88(1); Ni1–O1 1.908(8); Ni1–O3 1.919(9); Ni1–Ni2 2.851(2); Ni2–C3 1.87(1); Ni2–C4 1.89(1); Ni2–O4 1.909(8); Ni2–O2 1.921(8). Selected bond angles (deg): C2–Ni1–C1 91.4(6); C2–Ni1–O1 172.5(5); C1–Ni1–O1 88.3(5); C2–Ni1–O3 91.2(5); C1–Ni1–O3 174.7(4); O1–Ni1–O3 88.6(4); C2–Ni1–Ni2 106.6(5); C1–Ni1–Ni2 103.2(4); O1–Ni1–Ni2 80.7(2); O3–Ni1–Ni2 80.5(2); C3–Ni2–C4 91.4(5); C3–Ni2–O4 170.2(5); C4–Ni2–O4 89.0(5); C3–Ni2–O2 91.0(5); C4–Ni2–O2 173.8(5); O4–Ni2–O2 87.7(4); C3–Ni2–Ni1 109.2(4); C4–Ni2–Ni1 104.3(4); O4–Ni2–Ni1 80.2(2); O2–Ni2–Ni1 80.3(2); C5–O1–Ni1 126.4(8); C5–O2–Ni2 126.5(8); C7–O3–Ni1 124.9(8); C7–O4–Ni2 126.9(8).

Figure 2.

Figure 2

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19F NMR spectra in MeCN solvent of the reaction of [(MeCN)2Ni(CF3)2] (1) with various equivalents of added [NMe4][OAc]. (a) 0.5; (b) 0.9; (c) 2.0; (d) 5; and (e) 10 equiv. Final NMR sample concentrations = 3.6 mM. The [(MeCN)2Ni(CF3)2] (1) signal is at δ = −27.8; the [NMe4]2[Ni(CF3)2(OAc)]2 (9) signal is at δ = −29.6; and the [NMe4]2[Ni(CF3)2(OAc)2] (10) signal is at δ = −27.6.

We reasoned that the requirement of high concentrations of tetramethylammonium acetate to afford 10 may be due to the tendency of Ni(II) trifluoromethyl complexes to prefer square-planar geometries, which limits the binding of acetate to its weaker κ1-binding mode. Our resulting hypothesis was that the oxidation of Ni(II) to Ni(III) may present an opportunity to better isolate a κ2-diacetato derivative of nickel bearing two trifluoromethyl ligands, as higher coordinate forms are more common at Ni(III). Indeed, the reaction of 1 with (diacetoxyiodo)benzene in the presence of tetramethylammonium acetate led to the precipitation of the formally Ni(III) diacetato complex 11 in good yields (Scheme 1). Complex 11 is a purple (λmax = 562 nm; see the Supporting Information for the UV–Vis absorption spectrum) paramagnetic solid that can be easily purified from the iodobenzene byproduct of the reaction to yield analytically pure material. X-ray diffraction provided support for its structure, and an ORTEP diagram of 11 is shown in Figure 3. Complex 11 possesses an octahedral coordination sphere with the two acetate ligands each binding in a κ2-fashion to nickel. The two trifluoromethyl ligands are cis to each other, with Ni–C bond lengths similar to those found in other Ni(III) trifluoromethyl complexes.4,8

Figure 3.

Figure 3

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ORTEP diagram of 11. Selected bond lengths (Å): Ni1–C2 1.91(1); Ni1–C1 1.93(1); Ni1–O1 2.126(9); Ni1–O2 1.960(7); O1–C3 1.25(2); O2–C3 1.27(2); Ni–O3 1.962(9); Ni1–O4 2.146(7); O4–C5 1.26(2); C4–C3 1.47(2). Selected bond angles (deg): C2–Ni1–C1 87.4(6); C2–Ni1–O2 92.1(5); C1–Ni1–O2 166.2(5); C2–Ni1–O3 167.2(4); C1–Ni1–O3 93.0(6); O2–Ni1–O3 90.6(3); C2–Ni1–O1 98.3(5); C1–Ni1–O1 102.6(5); O2–Ni1–O1 63.8(3); O3–Ni1–O1 94.0(4); C2–Ni1–O4 103.7(5); C1–Ni1–O4 100.1(5).

The X-band electron paramagnetic resonance (EPR) spectra of 11 in MeCN solution at 298 K showed an isotropic broad spectrum at a giso value of 2.167 (Figure 4). A powder sample showed a rhombic spectral pattern with g⊥ (g perpendicular) = 2.198 larger than g∥ (g parallel) = 2.078. The spectrum can be considered “pseudo-axial” in nature with g1 and g2 being very similar and larger than g3.9 The averaged g value from this spectrum gav (2g⊥+g∥)/3 of 2.167 is identical to the giso strongly supporting that the material is the same in both samples (no decomposition in solution). The g anisotropy Δg = g∥–g⊥ is calculated to be 0.12. The isotropic giso and averaged gav value above 2.1 is fully in line with a mononuclear Ni(III) complex representing a d7 system with an electron spin S = 1/2.5,8b,9−15 While the giso or gav values do not allow conclusions on the coordination number and geometry, other parameters, such as the shape (geometry) of the signal and the g anisotropy Δg, roughly correlate with the coordination number and geometry around Ni(III). Hexacoordinated Ni(III) complexes usually show rhombic spectra, which include “pseudo-axial” spectra in which g1 and g2 are very close and larger than g3 which give them the look of axial spectra with g⊥ > g∥.4,8−10,12,14 Unequivocally axial spectra with g⊥ > g∥ have been reported for five-coordinate Ni(III) complexes,5,8 among them [(Tp)Ni(neoPh)] (Tp– = tripyrazolyl-boranate; neoPh2– = 2-methylpropan-2-yl)phenyl),8b [(Tp)Ni(CF3)(Ph)],8b and [tBu2terpy)Ni(CF3)2],5 and for Ni(III) species produced from four-coordinate Ni(II) precursors.11,13 Axial spectra are also found for the ultimately square-planar Ni(III) complexes [NBu4][Ni(C6X5)4] (X = Cl or F).15 Interestingly, in terms of Δg, our complex lies in the typical range from 0.100 to 0.200, in line with a marked contribution of the ligand(s) to the distribution of the unpaired electron.4,5,8a,11,14 Far higher values indicate almost complete localization on the nickel as in [NBu4][Ni(C6X5)4] with Δg = 1.030 (F) and 0.939 (Cl), respectively.15 A remarkably low Δg was reported for [(Tp)Ni(CF3)2(MeCN)] (0.030).8b Consequently, appreciable hyperfine interaction with a coupling constant A of around 20 G with the axial N atom (AN) of this octahedral complex and square-pyramidal derivatives (without the MeCN ligand) was found although DFT-calculations suggest a ground-state electronic structure with the radical primarily localized on nickel.8b In the octahedral complexes of the type [Ni(RN3C)(F)2], [Ni(RN3C)(F)(MeCN)]+, and [Ni(RN3C)(MeCN)2]2+, containing cyclic tetradentate RN3C– ligands (RN3HC = [−R′-phenide–R-amine–pyridyl–R-amine]), slightly smaller AN values of around 10 to 15 G are dependent on the R substituents influencing the axial amine ligand moieties.10 Here, the Δg values of around 0.200 are in keeping with the assumption of a ligand contribution.10 The same is true for the pyridine-containing Ni(III) radicals [(Py)3Ni(CF3)2(F)] and [(Py)Ni(F)(CF3)2(μ-F)2Ni(CF3)2(Py)2], with AN values of 22 and 20 G, respectively.4 Neither in the isotropic spectrum of 11 in solution nor in the powder spectrum did we find any evidence for hyperfine splitting. Together with the observation of EPR spectra at ambient T, while, for related Ni(III) complexes, low T ranging from 77 to 110 K was required to record their EPR spectra, this makes 11 unique in the frame of mononuclear Ni(III) complexes as so far all of them contain noninnocent16 ligands such as polypyridine or polyamine, heterocycles, carbenes, or phosphines.4,5,9−15

Figure 4.

Figure 4

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X-band EPR spectra of 11; (A) experimental spectrum in MeCN solution at 298 K, frequency = 9.875563 GHz (in black) with simulated spectrum with g = 2.167 and 75 G (Lorentzian) line width (in red). (B) Experimental spectrum of a solid powder sample at 298 K, frequency = 9.876721 GHz (in black) with simulated spectrum with g⊥ = 2.198 and g∥ of 2.078 and 90, 120, and 100 G Lorentzian line widths (in red).

The electrochemical properties of 11 in a MeCN solution were investigated by cyclic voltammetry, and the plots are shown in Figure 5. The oxidation of 11 appears as a partially reversible wave at a peak potential of +0.70 V vs the ferrocene/ferrocenium (Fc/Fc+) couple and likely represents a Ni(III)/Ni(IV) couple. The Ni(III)/Ni(II) couple appears at a peak potential of −1.33 V, which is significantly more negative than the peak potential seen for the related anionic nickel trifluoromethyl complex [NMe4][(Tp)Ni(CF3)2] (ca. –0.25 mV).8b The more negative redox couple for octahedral 11 may be due, in part, to the donation of the extra heteroatom lone pair relative to the pentacoordinate [NMe4][(Tp)Ni(CF3)2].8b To our knowledge, no comparable cyclic voltammograms containing information about a Ni(III)/Ni(IV) couple have been recorded for a complex bearing two trifluoromethyls and oxygen coligands. The peak potential for the Ni(IV)/Ni(III) reduction for the octahedral [(Tp)Ni(CF3)3] is reported at ca. –0.1 V vs Fc/Fc+.1g We were perplexed to find that the reduction of a related [(Py2CFPh)Ni(F)(CF3)2] complex was reported to occur with a peak potential of −2.1 V.17 As shown in Figure 5, the Ni(IV)/Ni(III) couple for 11 appears at ca. +0.5 V. Thus, the redox potentials of nickel trifluoromethyl complexes are highly dependent on the supporting ligand framework, which in turn affects overall charge. As an example, the oxidative Ni(II/III) couple for the charge neutral cis-[(MeCN)2Ni(CF3)2]3 occurs at +0.76 V.18 The related four-coordinate anionic complex [(MeCN)Ni(CF3)3]− exhibits a markedly reduced potential of +0.38 V, in line with an additional covalent X-type ligand that affords a formal negative charge.18 Nevertheless, the oxidation of [(MeCN)Ni(CF3)3]− occurs at more positive potentials than the anionic and pentacoordinate [(Tp)Ni(CF3)2]−. Interestingly, the square-planar [Ni(C6X5)4]2– complexes, also not containing any L-type coligands, exhibit potentials of +0.36 (X = Cl) and 0.54 V (X = F).15

Figure 5.

Figure 5

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Cyclic voltammogram of 11 and added ferrocene in the MeCN solvent. Metal complex: 10 mM; [NBu4][PF6]: 100 mM; working and counter electrodes: Pt with a Ag pseudo reference; scan rate: 100 mV/s.

Interestingly, we observed that nickel perfluoroethyl derivatives behaved differently than the trifluoromethyl counterparts with acetate ions. Reaction of known5 complex 12 with an equivalent of tetramethylammonium acetate led cleanly to the monoacetate derivative 13 in high yields (eq 1). An X-ray analysis shows that, in the solid state, 13 exists as a monomer with the nickel coordinating to both oxygens of a single acetate ligand (Figure 6). Evidently, the sterics of the perfluoroethyl group are better than that of trifluoromethyl at stabilizing the monomeric form of the resulting monoacetate adduct. 19F NMR spectroscopy revealed that addition of a large excess (ten equivalents) of tetramethylammonium acetate to 12 in MeCN solvent led to 13 and only 2% of the tentative diacetate complex [NMe4]2[Ni(C2F5)(OAc)2] (14, eq 1). Complex 14 displays signals for the perfluoroethyl resonances in the 19F NMR spectrum at δ = −82.1 and −108.5 in MeCN solvent.

graphic file with name om4c00029_0002.jpg 1

Figure 6.

Figure 6

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ORTEP diagram of 13. Selected bond lengths (Å): Ni1–C1 1.870(5); Ni1–C3 1.881(5); Ni1–O2 1.967(3); Ni1–O1 1.967(3); Ni1–C5 2.300(5). Selected bond angles (deg): C1–Ni1–C3 96.7(2); C1–Ni1–O2 164.7(2); C3–Ni1–O2 98.6(2); C1–Ni1–O1 97.9(2); C3–Ni1–O1 165.4(2); O2–Ni1–O1 66.8(2); C1–Ni1–C5 131.4(2); C3–Ni1–C5 131.9(2); O2–Ni1–C5 33.4(2); O1–Ni1–C5 33.4(2); C5–O1–Ni1 87.8(3); C5–O2–Ni1 87.9(3); C9–N1–C8 109.2(5); C9–N1–C7 109.5(4); C8–N1–C7 109.1(5); C9–N1–C10 109.5(4); C8–N1–C10 109.9(5); C7–N1–C10 109.5(4); F1–C1–F2 102.9(4); F1–C1–C2 104.4(4); F2–C1–C2 104.0(4); F1–C1–Ni1 120.3(3); F2–C1–Ni1 109.5(3); C2–C1–Ni1 114.1(4).

To further understand the scope of acetate coordination to trifluoromethylnickel, we reacted the known3 nickelate [NMe4][(MeCN)Ni(CF3)3] (which bears three trifluoromethyl groups) with excess (10 equiv) tetramethylammonium acetate (eq 2). 19F NMR experiments reveal that a new species with chemical shifts of δ = −21.2 (septet, J = 4.0 Hz) and −32.2 (quartet, J = 4.0 Hz) is formed without complete conversion of the starting nickel complex 2 (see the Supporting Information). Based on the reactivity described herein for all other nickel complexes, we assign this new species as monoadduct 15 (eq 2). Interestingly, the large excess of acetate ions did not lead to any further coordination of acetate beyond the monoadduct, unlike that observed for compounds 1 and 12.

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The replacement of MeCN ligands in nickel complexes 1, 12, and 2 with acetate was measured at a standard 8 mM concentration in MeCN solution, and the results are summarized in Table 1 (see Supporting Information for spectra). The sterically less encumbered 1 is most prone to adding additional acetate ligands to form bis-adducts. The perfluoroethyl derivative 12 readily and cleanly adds one equivalent of acetate ion, but the addition of another acetate is sterically unfavored. Complex 2 is perhaps the most sterically hindered starting material, and even upon the addition of ten equiv of acetate ion the monoadduct is not fully formed. Alternative explanations include the differing lability of the acetonitrile ligand in 2 due to electronics and/or the lower tendency of an already negatively charged complex to add another negatively charged coligand.

Table 1. Speciation of Nickel Complexes upon the Addition of 10 Equiv Tetramethylammonium Acetatea.

starting Ni complex (plus 10 equiv acetate) % starting Ni complex % monoacetate % diacetate
[(MeCN)2Ni(CF3)2] (1) 0 76 24
[(MeCN)2Ni(C2F5)2] (12) 0 98 2
[NMe4][(MeCN)Ni(CF3)3] (2) 19 81 0
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a

As determined by 19F NMR spectroscopy, concentrations of the complexes: 8 mM in MeCN.

Conclusions

A diverse range of reactivities were observed in the reaction of fluoroalkylnickel complexes containing MeCN ligands with the simple acetate ion. Mono- and bis-adducts are observed, whose structures depend on the nature of the fluoroalkyl group or the oxidation state of the metal. Understanding how simple counteranions coordinate to nickel fluoroalkyl complexes is an important step in developing new reactions and methodologies that avoid the use of expensive phosphine- or imine-based ligands. The development of metal-catalyzed reactivities involving bound acetate ligands is especially intriguing, as metal-acetates are known to participate in metalation-deprotonation of aromatic C–H bonds leading to organometallic intermediates.19−21 Reactivity studies of the acetate complexes, based on the findings reported herein, are currently being explored in our lab.

Experimental Procedures

General Considerations

All manipulations were performed using standard Schlenk and high vacuum techniques22 or in a dinitrogen-filled glovebox, unless otherwise stated. Solvents were purified by passing through activated alumina or copper in a solvent purification system supplied by Pure Process Technology. 1H NMR spectra were recorded at ambient temperature on a Bruker 400 MHz spectrometer and referenced to residual proton solvent signals. 19F NMR spectra were recorded on a Bruker NMR spectrometer operating at 376 MHz and referenced to α,α,α-trifluorotoluene as an internal standard (δ = −63.7). EPR spectra were recorded in the X-band on a Bruker System ELEXSYS 500E equipped with a Bruker Variable Temperature Unit ER 4131VT (500 to 100 K) (Bruker, Rheinhausen, Germany). The g values were calibrated by using a dpph sample. Spectral simulation was carried out using Bruker WinEPR and Simfonia.

Preparation of [NMe4]2[Ni(CF3)2(OAc)]2(9)

In the glovebox, [(MeCN)2Ni(CF3)2] (279.0 mg, 0.1 mmol) and tetramethylammonium acetate (13.3 mg, 0.1 mmol) were dissolved in 3.0 mL of dry MeCN. The mixture was stirred for 30 min. Removing the solvent using the high vacuum line, followed by transferring the yellow solid to a tared vial, provided 31.1 mg (94.3%) of product. 1H NMR (CD3CN, 400 MHz): δ 3.07 (s, 12H), 1.65 (s, 3H). 19F NMR (CD3CN, 376 MHz): δ −29.6 (s). Anal. Calcd for C16H30 F12N2Ni2O4: C, 29.13 (28.91); H, 4.58 (4.61).

Preparation of [NMe4][Ni(CF3)2(OAc)2] (11)

In the glovebox, [(MeCN)2Ni(CF3)2] (83.7 mg, 0.3 mmol), tetramethylammonium acetate (40.1 mg, 0.3 mmol), and phenyliodine(III) diacetate (48.6 mg, 0.15 mmol) were dissolved in 3.0 mL of dry MeCN. The mixture was stirred for 30 min. Enough ether was then added to precipitate out the product. Filtration and washing with ether provided a purple powder (83.8 mg, 71.8%). The compound is paramagnetic. Anal. Calcd for C10H18F6NNiO4: C, 30.88 (30.95); H, 4.67 (4.70).

Preparation of [NMe4][Ni(C2F5)2(OAc)] (13)

In the glovebox, [(MeCN)2Ni(C2F5)2] (38.0 mg, 0.1 mmol) and tetramethylammonium acetate (13.4 mg, 0.1 mmol) were dissolved in 3.0 mL of dry MeCN. The mixture was stirred for 30 min. Removing the solvent using the high vacuum line, followed by transferring the yellow solid to a tared vial, provided 40.9 mg (95.1%) of product. 1H NMR (CD3CN, 400 MHz): δ 3.08 (s, 12H), 1.65 (s, 3H). 19F NMR (CD3CN, 376 MHz): δ −83.8 (s, 6F), −110.1 (s, 4F). Anal. Calcd for C10H15NNiO2: C, 27.94 (28.07); H, 3.52 (3.71).

Acknowledgments

D.A.V. thanks the U.S. National Science Foundation (CHE-2153730) for support of this work. We thank Sascha A. Schäfer for assistance with the EPR measurements.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.organomet.4c00029.

  • Crystallographic information files (CIF) and selected NMR spectral data (PDF)

Author Present Address

# Institute of Chemistry, College of Arts and Sciences, University of the Philippines Los Baños, College, Laguna, 4031, Philippines

The authors declare no competing financial interest.

Supplementary Material

om4c00029_si_001.pdf (1.1MB, pdf)

References

  1. a Feng Z.; Xiao Y.-L.; Zhang X. Transition-Metal (Cu, Pd, Ni)-Catalyzed Difluoroalkylation via Cross-Coupling with Difluoroalkyl Halides. Acc. Chem. Res. 2018, 51, 2264–2278. 10.1021/acs.accounts.8b00230. [DOI] [PubMed] [Google Scholar]; b An L.; Xu C.; Zhang X. Highly selective nickel-catalyzed gem-difluoropropargylation of unactivated alkylzinc reagents. Nature Commun. 2017, 8, 1460. 10.1038/s41467-017-01540-1. [DOI] [PMC free article] [PubMed] [Google Scholar]; c Xiao Y.-L.; Guo W.-H.; He G.-Z.; Pan Q.; Zhang X. Nickel-Catalyzed Cross-Coupling of Functionalized Difluoromethyl Bromides and Chlorides with Aryl Boronic Acids: A General Method for Difluoroalkylated Arenes. Angew. Chem., Int. Ed. 2014, 53, 9909–9913. 10.1002/anie.201405653. [DOI] [PubMed] [Google Scholar]; d Hu W.-Q.; Pan S.; Xu X.-H.; Vicic D. A.; Qing F.-L. Nickel-Mediated Trifluoromethylation of Phenol Derivatives by Aryl C–O Bond Activation. Angew. Chem., Int. Ed. 2020, 59, 16076–16082. 10.1002/anie.202004116. [DOI] [PubMed] [Google Scholar]; e Xu L.; Vicic D. A. Direct Difluoromethylation of Aryl Halides via Base Metal Catalysis at Room Temperature. J. Am. Chem. Soc. 2016, 138, 2536–2539. 10.1021/jacs.6b00053. [DOI] [PubMed] [Google Scholar]; f Bour J. R.; Roy P.; Canty A. J.; Kampf J. W.; Sanford M. S. Oxidatively Induced Aryl–CF3 Coupling at Diphosphine Nickel Complexes. Organometallics 2020, 39, 3–7. 10.1021/acs.organomet.9b00678. [DOI] [Google Scholar]; g Meucci E. A.; Nguyen S. N.; Camasso N. M.; Chong E.; Ariafard A.; Canty A. J.; Sanford M. S. Nickel(IV)-Catalyzed C–H Trifluoromethylation of (Hetero)arenes. J. Am. Chem. Soc. 2019, 141, 12872–12879. 10.1021/jacs.9b06383. [DOI] [PMC free article] [PubMed] [Google Scholar]; h Bour J. R.; Ferguson D. M.; Mcclain E. J.; Kampf J. W.; Sanford M. S. Connecting Organometallic Ni(III) and Ni(IV): Reactions of Carbon-Centered Radicals with High-Valent Organonickel Complexes. J. Am. Chem. Soc. 2019, 141, 8914–8920. 10.1021/jacs.9b02411. [DOI] [PubMed] [Google Scholar]
  2. Shreiber S. T.; Vicic D. A. Solvated Nickel Complexes as Stoichiometric and Catalytic Perfluoroalkylation Agents. Angew. Chem., Int. Ed. 2021, 60, 18162–18167. 10.1002/anie.202104559. [DOI] [PubMed] [Google Scholar]
  3. Shreiber S. T.; Dimucci I. M.; Khrizanforov M. N.; Titus C. J.; Nordlund D.; Dudkina Y.; Cramer R. E.; Budnikova Y.; Lancaster K. M.; Vicic D. A. [(MeCN)Ni(CF3)3]− and [Ni(CF3)4]2–: Foundations toward the Development of Trifluoromethylations at Unsupported Nickel. Inorg. Chem. 2020, 59, 9143–9151. 10.1021/acs.inorgchem.0c01020. [DOI] [PubMed] [Google Scholar]
  4. D’Accriscio F.; Borja P.; Saffon-Merceron N.; Fustier-Boutignon M.; Mézailles N.; Nebra N. C–H Bond Trifluoromethylation of Arenes Enabled by a Robust, High-Valent Nickel(IV) Complex. Angew. Chem., Int. Ed. 2017, 56, 12898–12902. 10.1002/anie.201706237. [DOI] [PubMed] [Google Scholar]
  5. Zhang C.-P.; Wang H.; Klein A.; Biewer C.; Stirnat K.; Yamaguchi Y.; Xu L.; Gomez-Benitez V.; Vicic D. A. A Five-Coordinate Nickel(II) Fluoroalkyl Complex as a Precursor to a Spectroscopically Detectable Ni(III) Species. J. Am. Chem. Soc. 2013, 135, 8141–8144. 10.1021/ja4030462. [DOI] [PubMed] [Google Scholar]
  6. Kuhn L.; Vil’ V. A.; Barsegyan Y. A.; Terent’ev A. O.; Alabugin I. V. Carboxylate as a Non-innocent L-Ligand: Computational and Experimental Search for Metal-Bound Carboxylate Radicals. Org. Lett. 2022, 24 (21), 3817–3822. 10.1021/acs.orglett.2c01356. [DOI] [PubMed] [Google Scholar]
  7. a Kozitsyna N. Y.; Nefedov S. E.; Dolgushin F. M.; Cherkashina N. V.; Vargaftik M. N.; Moiseev I. I. Heterodimetallic PdII-based carboxylate-bridged complexes: Synthesis and structure of single-crystalline PdII–M (M = MnII, CoII, NiII, CuII, ZnII, NdIII, EuIII, CeIV) acetates. Inorg. Chim. Acta 2006, 359, 2072–2086. 10.1016/j.ica.2006.01.027. [DOI] [Google Scholar]; b Wang S.; Hu M.-L.; Ng S. W. catena-Poly[[tetra-μ-acetatodinickel(II)]μ-N,N′-hexamethylenetetramine]. Acta Cryst. 2002, E58, m242–m244. 10.1107/S1600536802007316. [DOI] [Google Scholar]; c Diccianni J. B.; Hu C.; Diao T. Binuclear, High-Valent Nickel Complexes: Ni–Ni Bonds in Aryl–Halogen Bond Formation. Angew. Chem., Int. Ed. 2017, 56, 3635–3639. 10.1002/anie.201611572. [DOI] [PubMed] [Google Scholar]; d Eremin A. V.; Belyaev A. N. Binuclear nickel(II) acetate. Russ. J. Gen. Chem. 2011, 81, 428–428. 10.1134/S1070363211020265. [DOI] [Google Scholar]
  8. a Deolka S.; Govindarajan R.; Khaskin E.; Fayzullin R. R.; Roy M. C.; Khusnutdinova J. Photoinduced Trifluoromethylation of Arenes and Heteroarenes Catalyzed by High-Valent Nickel Complexes. Angew. Chem., Int. Ed. 2021, 60, 24620–24629. 10.1002/anie.202109953. [DOI] [PubMed] [Google Scholar]; b Bour J. R.; Camasso N. M.; Meucci E. A.; Kampf J. W.; Canty A. J.; Sanford M. S. Carbon–Carbon Bond-Forming Reductive Elimination from Isolated Nickel(III) Complexes. J. Am. Chem. Soc. 2016, 138, 16105–16111. 10.1021/jacs.6b10350. [DOI] [PubMed] [Google Scholar]
  9. Schultz J. W.; Fuchigami K.; Zheng B.; Rath N. P.; Mirica L. M. Isolated Organometallic Nickel(III) and Nickel(IV) Complexes Relevant to Carbon–Carbon Bond Formation Reactions. J. Am. Chem. Soc. 2016, 138, 12928–12934. 10.1021/jacs.6b06862. [DOI] [PubMed] [Google Scholar]
  10. Zhou W.; Watson M. B.; Zheng S.; Rath N. P.; Mirica L. M. Ligand effects on the properties of Ni(III) complexes: aerobically-induced aromatic cyanation at room temperature. Dalton Trans. 2016, 45, 15886–15893. 10.1039/C6DT02185A. [DOI] [PubMed] [Google Scholar]
  11. Kosobokov M. D.; Sandleben A.; Vogt N.; Klein A.; Vicic D. A. Nitrogen–Nitrogen Bond Formation via a Substrate-Bound Anion at a Mononuclear Nickel Platform. Organometallics 2018, 37, 521–525. 10.1021/acs.organomet.7b00887. [DOI] [Google Scholar]
  12. Bhowmick I.; Roehl A. J.; Neilson J. R.; Rappé A. K.; Shores M. P. Slow magnetic relaxation in octahedral low-spin Ni(III) complexes. Chem. Sci. 2018, 9, 6564–6571. 10.1039/C7SC04482H. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Pirovano P.; Farquhar E. R.; Swart M.; Mcdonald A. R. Tuning the Reactivity of Terminal Nickel(III)–Oxygen Adducts for C–H Bond Activation. J. Am. Chem. Soc. 2016, 138, 14362–14370. 10.1021/jacs.6b08406. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Yu S.; Dudkina Y.; Wang H.; Kholin K. V.; Kadirov M. K.; Budnikova Y. H.; Vicic D. A. Accessing perfluoroalkyl nickel(II), (III), and (IV) complexes bearing a readily attached [C4F8] ligand. Dalton Trans. 2015, 44, 19443–19446. 10.1039/C5DT01771H. [DOI] [PubMed] [Google Scholar]
  15. Alonso P. J.; Arauzo A. B.; Garcia-Monforte M. A.; Martín A.; Menjón B.; Rillo C.; Tomás M. Homoleptic Organoderivatives of High-Valent Nickel(III). Chem.–Eur. J. 2009, 15, 11020–11030. 10.1002/chem.200901259. [DOI] [PubMed] [Google Scholar]
  16. Kaim W. The Shrinking World of Innocent Ligands: Conventional and Non-Conventional Redox-Active Ligands. Eur. J. Inorg. Chem. 2012, 2012, 343–348. 10.1002/ejic.201101359. [DOI] [Google Scholar]
  17. Chong E.; Kampf J. W.; Ariafard A.; Canty A. J.; Sanford M. S. Oxidatively Induced C–H Activation at High Valent Nickel. J. Am. Chem. Soc. 2017, 139, 6058–6061. 10.1021/jacs.7b02387. [DOI] [PubMed] [Google Scholar]
  18. Shreiber S. T.; Amin F.; Schäfer S. A.; Cramer R. E.; Klein A.; Vicic D. A. Synthesis, structure, and electrochemical properties of [LNi(Rf)(C4F8)]− and [LNi(Rf)3]− complexes. Dalton Trans. 2022, 51, 5515–5523. 10.1039/D2DT00511E. [DOI] [PubMed] [Google Scholar]
  19. Gorelsky S. I.; Lapointe D.; Fagnou K. Analysis of the Palladium-Catalyzed (Aromatic)C–H Bond Metalation–Deprotonation Mechanism Spanning the Entire Spectrum of Arenes. J. Org. Chem. 2012, 77, 658–668. 10.1021/jo202342q. [DOI] [PubMed] [Google Scholar]
  20. Alharis R. A.; Mcmullin C. L.; Davies D. L.; Singh K.; Macgregor S. A. The Importance of Kinetic and Thermodynamic Control when Assessing Mechanisms of Carboxylate-Assisted C–H Activation. J. Am. Chem. Soc. 2019, 141, 8896–8906. 10.1021/jacs.9b02073. [DOI] [PubMed] [Google Scholar]
  21. Ackermann L. Carboxylate-Assisted Transition-Metal-Catalyzed C–H Bond Functionalizations: Mechanism and Scope. Chem. Rev. 2011, 111, 1315–1345. 10.1021/cr100412j. [DOI] [PubMed] [Google Scholar]
  22. Vicic D. A.; Jones G. D.. Experimental methods and techniques: basic techniques; In Comprehensive Organometallic Chemistry III, Vol. 1; Elsevier Ltd., 2007, pp. 197–218. DOI: 10.1016/B0-08-045047-4/00008-X. [DOI] [Google Scholar]

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