Skip to main content
NCBI home page
JACS Au logoLink to JACS Au
. 2021 Sep 4;1(10):1631–1638. doi: 10.1021/jacsau.1c00265

Quadruple C–H Bond Activations of Methane by Dinuclear Rhodium Carbide Cation [Rh2C3]+

Hechen Wu 1, Xiao-Nan Wu 1,*, Xiaoyang Jin 1, Yangyu Zhou 1, Wei Li 1, Chonglei Ji 1, Mingfei Zhou 1,*
PMCID: PMC8549038  PMID: 34723266

Abstract

graphic file with name au1c00265_0006.jpg

The structure of the [Rh2C3]+ ion and its reaction with CH4 in the gas phase have been studied by infrared photodissociation spectroscopy and mass spectrometry in conjunction with quantum chemical calculations. The [Rh2C3]+ ion is characterized to have an unsymmetrical linear [Rh–C–C–C–Rh]+ structure existing in two nearly isoenergetic spin states. The [Rh2C3]+ ion reacts with CH4 at room temperature to form [Rh2C]+ + C3H4 and [Rh2C2H2]+ + C2H2 as the major products. In addition to the [Rh2C]+ ion, the [Rh213C]+ ion is formed at about one-half of the [Rh2C]+ intensity when the isotopic-labeled 13CH4 sample is used. The production of [Rh213C]+ indicates that the linear C3 moiety of [Rh2C3]+ can be replaced by the bare carbon atom of methane with all four C–H bonds being activated. The calculations suggest that the overall reactions are thermodynamically exothermic, and that the two Rh centers are the reactive sites for C–H bond activation and hydrogen atom transfer reactions.

Keywords: methane activation, rhodium carbide, mass spectrometry, infrared photodissociation spectroscopy, quantum chemical calculation.

Introduction

Methane is a naturally abundant molecule and is one of the most potent greenhouse gases contributing to global warming. It is extremely stable with very high C–H bond strengths (439, 463, 443, and 339 kJ/mol for the four C–H bonds), negligible electron affinity, and low polarizability.1 Consequently, the activation and conversion of methane into value-added chemicals is very important but is quite challenging.2−6 For some chemical transformation processes, such as the conversion of methane to syngas, it needs the activation of all the four C–H bonds of methane. These reaction processes always demand high temperature and pressure.7 Systems that can activate methane at mild conditions are in high demand. Many examples of methane activation at transition-metal centers have been reported.8−13 To develop practical methane conversion processes, much remains to be learned about the processes and factors controlling the activity and selectivity of catalytic reactions. Gas-phase reactions of transition-metal atoms, ions, and clusters with methane serve as simple models in understanding the intrinsic mechanism of the catalytic methane conversion processes.14−24

Transition-metal carbides and carbide-based surfaces were found to be able to activate methane at mild conditions.25−29 In view of this, the reactivity of transition metal carbide ions with methane has been intensively investigated in the gas phase by mass spectrometry and quantum chemical calculations.30−41 Mechanistic aspects of the C–H bond activation of methane by diatomic transition metal carbide cations were elucidated by quantum-chemical calculations and verified experimentally using mass spectrometry.30−35 The activation of methane by metal-carbide cations was found and proposed to proceed via different mechanisms including hydrogen atom transfer (HAT) and proton-coupled electron transfer (PCET), as well as hydride transfer (HT).33 Simultaneous activation of two C–H bonds of methane was identified in the reaction of the copper carbide cation.32,33 The bond dissociation energies, spin states, number of d-electrons, and charge distributions of the metal carbide cations are factors that jointly affect both the reactivity and the mechanism of C–H bond activation.33 Transition-metal carbide anions are usually not very reactive with methane. However, it was found that the FeC6– anion can activate CH4 via a dissociative adsorption manner.36 The large dipole moment of FeC6– can induce a polarization of CH4, which facilitates cleavage of the C–H bond. The FeC3– anion reacts with methane under high-temperature conditions to form the C–C coupling product acetylene.37 The reactions of other metal carbide cluster ions with methane have also been reported.38−41 Most clusters show high reactivity toward CH4 dehydrogenation at thermal conditions. The cooperation of the metal centers in the dinuclear carbide cluster reaction has been proposed.39 The C–H bond activation takes place predominantly around one Ta center in the initial stage of the reaction, and the second Ta center accepts the delivered H atom from the C–H bond cleavage.39

In this paper, we report a combined experimental and theoretical study on the reaction of a dinuclear rhodium carbide cation [Rh2C3]+ with methane in the gas phase. We will show that the reactions involving the activation of all four C–H bonds of the methane and carbon atom exchange processes proceed at thermal conditions.

Experimental and Computational Methods

The infrared photodissociation spectrum of the [Rh2C3·Ar]+ ions was measured using a collinear tandem time-of-flight mass spectrometer as described in detail previously.42 The rhodium carbide cations were generated in the gas phase using a pulsed laser vaporization-supersonic expansion ion source. The fundamental of a Nd:YAG laser with 10–20 mJ/pulse was employed to ablate a rhodium + graphite (1:4) target. The cation complexes were produced during the laser ablation process in supersonic expansions of helium or Ar gas mixtures at about 1.0 MPa backing pressure. After free expansion and cooling, the ions were extracted and analyzed using a time of-flight mass spectrometer. The [Rh2C3·Ar]+ ions were mass-selected, decelerated, and subjected to IR photodissociation by a tunable IR laser. The fragment and undissociated parent ions were reaccelerated and mass analyzed by a second collinear time-of-flight mass spectrometer. Infrared photodissociation spectrum was obtained by monitoring the fragment ion yield (the intensity of fragment ions divided by the sum of intensities of the fragment ions and the undissociated parent ions) as a function of the dissociation IR laser wavelength. The tunable infrared source is generated by an KTP/KTA/AgGaSe2 optical parametric oscillator/amplifier system (OPO/OPA, Laser Vision) pumped by a Continuum Surelite Nd:YAG laser, which is tunable in the range of 800–5000 cm–1 with an approximate line width of 2 cm–1. Typical spectra were recorded by scanning the dissociation laser in steps of 2 cm–1 and averaging over 250 laser shots at each wavelength. The laser pulse energy ranges from 0.2 to 1.5 mJ/pulse.

The reaction of [Rh2C3]+ ions with methane was studied using an ion trap mass spectrometer.43 The ions generated by a pulsed laser vaporization-supersonic expansion ion source were mass-selected by a quadrupole and then were sent into a quadrupole linear ion trap, where the ions were accumulated and thermalized to room temperature by helium gas for 20 ms with an estimated number of collisions of 2800.44 The [Rh2C3]+ ions reacted with methane introduced by a pulsed valve. After a 10 ms reaction, the trapped ions were successively ejected through the slit of the ion trap according to the mass-to-charge ratio by scanning the radio frequency (rf) from 150 to 500 V over 80 ms. The ejected ions were detected by electron multipliers with dynodes (DeTech 397).

Theoretical calculations were performed using the Gaussian 09 package at the dispersion corrected B3LYP-D3/def2TZVP level of theory.45−49 The Molclus program was used to search for the possible stable structures of the reactants and products.50 The low-lying stable isomers were then reoptimized at the B3LYP-D3/def2TZVP level to confirm the relative energy sequence. The stability of the wave functions for each optimized structure is checked. Calculations at this level of theory can provide reliable predictions on the C–H bond dissociation energies of methane, propyne, and allene with deviations less than 20 kJ/mol with respect to the experimental values (Table S1).51,52 The prediction of the Rh+–H bonds of RhH+ and RhCH3+ is slightly less accurate with deviations of 26 and 43 kJ/mol from the experimental values.53,54 The excitation energies 1D → 3F and 5F → 3F of Rh+ are predicted to be deviated by 57 and 13 kJ/mol from the experimental values (Table S2).55 The transition state optimizations were performed with the synchronous transit-guided quasi-Newton (STQN) method and were verified through intrinsic reaction coordinate (IRC) calculations.56−58 Vibrational frequency calculations were performed to identify the nature of reaction intermediates, transition states (TSs), and products. The harmonic vibrational frequencies are scaled by a factor of 0.964 according to the Computational Chemistry Comparison and Benchmark Database.59

Results and Discussion

To determine the geometric and electronic structures of the [Rh2C3]+ cation, infrared photodissociation spectroscopy is employed to obtain the vibrational spectrum of [Rh2C3]+. The dissociation energies of the [Rh2C3]+ cation are calculated to be 504, 690, 578, and 393 kJ/mol, respectively, with respect to the [RhCCC]+ + Rh, [RhCC]+ + RhC, [RhC]+ + RhCC, and [Rh]+ + RhCCC dissociation channels at the B3LYP-D3/def2TZVP level. Because the dissociation energies of the [Rh2C3]+ cation are predicted to be significantly greater than the infrared photon energies in the C–C and Rh–C stretching frequency region, the method of rare-gas atom predissociation is employed.60−63 The Ar-tagged complex [Rh2C3·Ar]+ is generated and mass-selected for infrared photodissociation. When the infrared laser is in resonance with one of the vibrational fundamentals of the [Rh2C3·Ar]+ complex, it photodissociates by eliminating an argon atom. The resulting infrared spectrum is shown in Figure 1a. Two close-lying bands centered at 1984 and 2011 cm–1 together with a weak broad band centered at 1384 cm–1 are observed. The two bands around 2000 cm–1 are very close to the antisymmetric stretching mode of linear C3 molecule at 2040 cm–1,64,65 suggesting that the [Rh2C3]+ cation involves a C3 subunit. The 1384 cm–1 band can be attributed to the symmetric stretching vibration of the C3 unit. The observation of the symmetric stretching mode suggests that the C3 subunit is either bent or asymmetric.

Figure 1.

Figure 1

Open in a new tab

Experimental and simulated infrared spectra of [Rh2C3·Ar]+. (a) Experimental infrared photodissociation spectrum, (b) simulated spectrum of the doublet state, and (c) simulated spectrum of the quartet state. The simulated spectra are obtained by applying Lorentzian functions with the theoretical harmonic vibrational frequencies scaled by a factor of 0.964 and a 5 cm–1 full width at half-maximum (fwhm).

As shown in Figure 2, the most stable structure of the [Rh2C3]+ cation is predicted to have a linear asymmetric structure [Rh–C–C–C–Rh]+ with two different Rh–C bonds of 1.90 and 1.72 Å, respectively. The two C–C bonds are also not the same with a shorter bond distance of 1.24 Å and a longer bond distance of 1.32 Å. The doublet 2Δ state and the quartet 4Δ state are nearly isoenergetic and have essentially the same geometric parameters and valence electron configuration of π4δ4δ3σ1σ1. The unpaired electrons occupy the rhodium-based molecular orbitals as shown in Figure 3. The quartet state, in which the unpaired electrons at the terminal rhodium atoms are ferromagnetically coupled is predicted to be 1 kJ/mol higher in energy than the doublet state with antiferromagnetic coupling of the unpaired electrons at the terminal rhodium atoms at the B3LYP level (Table 1). The quartet state is predicted to be 2 kJ/mol more stable than the doublet state at the CCSD(T)//B3LYP-D3/def2TZVP level.66 The other nonlinear structures are predicted to lie more than 98 kJ/mol higher in energy than the most stable linear structure as shown in Figure S1. The argon-tagged complexes of the linear [Rh2C3]+ ions are also calculated at the B3LYP-D3/def2TZVP level. The results show that the argon atom prefers to coordinate to the terminal rhodium atom with two unpaired electrons (with longer Rh–C bond) for both the quartet and doublet spin states (see Figure S1 and Table S3). The calculations also show that the energetic ordering of the doublet and quartet spin states is not affected by weak argon coordination. The Rh–Ar distances are quite large (2.64 and 2.67 Å) and the [Rh2C3]+ moiety in [Rh2C3·Ar]+ has essentially the same structure as the free cation as shown in Figure 2. The antisymmetric and symmetric C3 stretching modes of the doublet state [Rh2C3·Ar]+ ion are calculated at 2042 and 1388 cm–1, whereas these two modes of the quartet spin state are predicted at 2054 and 1393 cm–1 (Table 1). On the basis of the comparison between the simulated and experimental infrared spectra (Figure 1), the experimentally observed [Rh2C3]+ ion can be attributed to have the unsymmetrical linear [Rh–C–C–C–Rh]+ structure coexisting in the two nearly isoenergetic doublet and quartet spin states. The observed 1984 and 2011 cm–1 bands separated by 27 cm–1 are assigned to the antisymmetric C3 stretching modes of the ions in the doublet and quartet spin states, respectively. The symmetric stretching modes of the two spin states are predicted to be separated by only 5 cm–1, and thus cannot be resolved experimentally. The coexistence of two spin states has been reported for other ions previously.34,39

Figure 2.

Figure 2

Open in a new tab

Optimized structures (bond lengths in Å) of the linear [Rh2C3]+ ion and its Ar-tagged [Rh2C3·Ar]+ complex at the B3LYP-D3/def2TZVP level of theory. The relative energies are given in kJ/mol. Purple, Rh; gray, C; light blue, Ar.

Figure 3.

Figure 3

Open in a new tab

Frontier molecular orbitals of [Rh2C3]+ in the doublet and quartet spin states. (SOMO − 1, HOMO, and HOMO − 1 are doubly degenerate, and only one orbital is shown).

Table 1. Experimental and Calculated Vibrational Frequencies of the [Rh2C3·Ar]+ and [Rh2C3]+ Ions and Calculated Relative Energy (ΔE, in kJ/mol), Argon Binding Energy (BDE, in kJ/mol) and IR Intensities (in km/mol)a.

  ΔE (kJ/mol) BDE (kJ/mol) mode obsd (cm–1) calcd (cm–1) IR intensities (km mol–1)
2[Rh2C3·Ar]+ 0 35 a 1984 2042 1688
s 1384 1388 135
4[Rh2C3·Ar]+ +1 35 a 2011 2054 1793
s 1384 1393 140
2[Rh2C3]+ 0   a   2043 1449
s   1385 141
4[Rh2C3]+ +1   a   2054 1544
s   1390 149
Open in a new tab
a

The symbols “a” and “s” denote anti-symmetric and symmetric stretching modes of the C3 subunit in the ions.

The mass spectra from the reactions of mass-selected [Rh2C3]+ ions (m/z = 242) with He, CH4, 13CH4, and CD4 in the ion trap at room temperature are shown in Figure 4. No product ion is observed in the mass spectrum using pure He as reactant gas (Figure 4a), while two mass peaks at m/z = 218 and 232, which can be attributed to the product ions with chemical formulas of [Rh2C]+ and [Rh2C2H2]+, are observed to be the major reaction products (Figure 4b). A very weak mass peak at m/z = 256 is also observed, which is assigned to the ion with chemical formula of [Rh2C4H2]+ (Figure 4b). The mass spectrum suggests that three reaction channels are observed for the [Rh2C3]+ and CH4 reactions. The first channel is the formation of the [Rh2C]+ cation with the release of a neutral C3H4 molecule (reaction 1). According to the thermochemical data, the heat of formation of propyne CH3CCH (185.71 ± 0.24 kJ/mol) is only slightly lower than that of allene CH2CCH2 (189.93 ± 0.25 kJ/mol),51 which suggests that both propyne and allene are formed in the reactions. The second channel is the generation of the [Rh2C2H2]+ ion with concomitant elimination of a neutral acetylene molecule C2H2 (reaction 2). The third channel is the generation of the [Rh2C4H2]+ ion with the release of a dihydrogen molecule as shown in reaction 3:

graphic file with name au1c00265_m001.jpg 1
graphic file with name au1c00265_m002.jpg 2
graphic file with name au1c00265_m003.jpg 3

The collision induced dissociation experiments (Figure S11) and the experiments using argon as the buffer gas (Figure S12) indicate that the contribution from collision-induced dissociation can clearly be ruled out. The reaction channel assignment is supported by the experiments with isotopic-labeled methane samples. Interesting results are observed when the 13CH4 sample is employed (Figure 4c). Both the [Rh2C2H2]+ and [Rh213CCH2]+ product ions are observed to have approximately the same intensity, indicating that one or both carbon atoms of the eliminated C2H2 neutral molecule come from the [Rh2C3]+ ion. This suggests that there are C/C exchange processes for the generation of [Rh213CCH2]+. Besides the [Rh2C]+ ion, the [Rh213C]+ ion is also formed to have about one-half of the [Rh2C]+ intensity. This is different with purely statistical expectations. The observation of [Rh213C]+ indicates that the carbon atom can originate from the CH4 reactant, implying that all the four C–H bonds are activated and transferred to the C3 moiety of the [Rh2C3]+ ion during the reaction (see reaction 4). The [Rh2C]+, [Rh2C2D2]+ and [Rh2C4D2]+ product ions are observed when the CD4 sample is employed (Figure 4d), which also support the proposed reactions 1–3.

graphic file with name au1c00265_m004.jpg 4

The variation in ion intensities of the reactant ([Rh2C3]+) and products ([Rh2C]+, [Rh2C2H2]+, and [Rh2C4H2]+) with respect to the CH4 pressure is given in Figure S2. The relative intensity of the reactant ion decreases and those of the product ions increase gradually as the pressure of reactant molecule CH4 increases. The number of CH4 is much larger than that of the [Rh2C3]+ ion in the ion trap, and the plots fit the pseudo-first-order kinetics. The rate constant k([Rh2C3]+ + CH4) is determined to be 2.5 × 10–11 cm3 s–1 molecule–1. The collision rate is calculated to be 9.7 × 10–10 cm3 s–1 using the Langevin–Gioumousis–Stevenson model,67,68 indicating that the reaction being observed occurs with an efficiency of only 2.6%. The uncertainty on this rate constants are estimated to be accurate within a factor of 3.

Figure 4.

Figure 4

Open in a new tab

Mass spectra from the reactions of the [Rh2C3]+ ion with (a) He, (b) CH4, (c) 13CH4, and (d) CD4.

To gain insight into the reaction mechanism, the potential energy profiles are calculated. All of the three reactions 1–3 leading to the most stable structures of the products are exothermic by 27, 21, and 46 kJ/mol, respectively at the B3LYP level. The most favorable pathway for the [Rh2C3]+ + CH4 reaction leading to the [Rh2C]+ + C3H4 products on the doublet spin state is shown in Figure 5, and the other possible pathways are given in Figures S3–S5. The most stable structure of [Rh2C]+ is linear with a doublet ground state ([Rh–C–Rh]+, Figure S6). Both the doublet state and quartet state [Rh2C3]+ ions can involve in the reaction with methane. All of the intermediates and transition states along the reaction pathways on the quartet state surface are about the same or higher in energy than those in the doublet state surface (Table S4). On the doublet state surface, the reaction proceeds with the initial formation of the adsorption complex (21), which is 39 kJ/mol lower in energy than the doublet ground-state reactants. The complex has a Cs symmetric structure with the CH4 molecule coordinated to the [Rh2C3]+ ion via two hydrogen atoms with a Rh–H distance of 2.06 Å. The first C–H bond cleavage of CH4 on the Rh center results in the formation of intermediate 22 (−64 kJ/mol) via transition state 2TS1 (−9 kJ/mol). The H atom is then transferred from the Rh center to the nearby carbon atom to form 23 (−71 kJ/mol) via 2TS2. This H atom transfer process is the rate-determining step for the overall reactions with the transition state (2TS2) lying at about the same energy level as the initial reactants (+0 kJ/mol). The relatively high barrier of 2TS2 may be the reason why the overall reactions have low efficiency.

Figure 5.

Figure 5

Open in a new tab

Simulated potential energy profiles for the reaction of [Rh2C3]+ with CH4 generating the [Rh2C]+ + C3H4 (allene) products at the B3LYP-D3 level. The relative energies of the reaction intermediates, transition states, and products with respect to the ground-state reactants are given in kJ/mol. Purple, Rh; gray, C; green, 13C; white, H.

For the generation of the [Rh2C]+ ions with the carbon atom originating from CH4 (P1 with the carbon atom in green in Figure 5), all four H atoms of CH4 are transferred step by step to the C3 moiety of [Rh2C3]+. In each step, the hydrogen atom in the CHn moiety (n = 1–4) is transferred via 2TS1 (−9 kJ/mol), 2TS7 (−89 kJ/mol), 2TS14 (−69 kJ/mol), and 2TS16 (−72 kJ/mol) forming the rhodium hydride intermediates. For the generating of the [Rh2C]+ ions with the carbon atom originating from [Rh2C3]+ (P2 in Figure 5), only two C–H bonds of CH4 need to be activated. The most favorable pathway to form P2 (in red) is different from that of the P1 channel (in blue) starting from the common intermediate 211. We can find that the 13C from methane can exchange with the carbons from the C3 unit except for the central carbon in the P2 channel or exchange with the whole C3 unit in the P1 channel. This might be responsible for the experimental observation that the peak of [Rh2C]+ is about twice as large as that of [Rh213C]+ in the mass spectrum shown in Figure 4c. The pathways for generating [Rh2C]+ + CH3CCH (propyne) are also calculated (Figures S4 and S5), which are very similar to those for generating [Rh2C]+ + CH2CCH2 (allene).

The two most favorable pathways for generating the [Rh2C2H2]+ + C2H2 (acetylene) products (reaction 2) are shown in Figure S7. The most stable structure of [Rh2C2H2]+ has a doublet ground state with C2v symmetry, in which the C2H2 moiety is side-on bonded to the Rh2+ dimer with the C2H2 plane perpendicular to the Rh–Rh bond (Figure S6). As shown in Figure S7, the reaction pathways from the reactants to the 219 and 221 intermediates are the same as that shown in Figure 5. Starting from either the 219 or 221 intermediate, the reactions proceed via multiple steps including rearrangement, C–H bond activation, and hydrogen atom transfer. The intermediate 238 involves two equivalent C2H2 moieties; either one can be liberated to form the final product P3. This explains the experimental observation that the peaks of [Rh2C2H2]+ and [Rh213CCH2]+ have about the same intensity as shown in Figure 4.

The most favorable pathway for generating [Rh2C4H2]+ + H2 (reaction 3) and the optimized geometries of [Rh2C4H2]+ are shown in Figures S8 and S9, respectively. The most stable structure of [Rh2C4H2]+ has a Cs symmetry structure, in which the C4H2 moiety is side-on bonded to the Rh2+ dimer via two C atoms with the C4H2 plane perpendicular to the Rh–Rh bond (Figure S9). The reaction pathway from the reactants to the 28 intermediate is the same as that shown in Figure 5. From the 28 intermediate, the reaction further proceeds via three additional intermediates and three transition states in forming the final products [Rh2C4H2]+ + H2 with the highest transition state (2TS44) lying 8 kJ/mol below the initial reactants.

The above-mentioned calculation results indicate that all of the three reaction channels are exothermic and all of the intermediates and transition states are about the same or lower in energy than the ground state reactants. Therefore, reactions 1–3 are all thermodynamically exothermic but with low reaction efficiency. The rate-limiting transition state is 2TS2 for all three reactions. The transition state past 2TS2 that limits the loss of C3H4 is the same as that limits the loss of C2H2 (2TS6, −17 kJ/mol). In contrast, the transition state past 2TS2 that limits the loss of H2 is 2TS44, which lies only 8 kJ/mol lower in energy than the reactants. These results are consistent with the experimental observation that the [Rh2C]+ and [Rh2C2H2]+ product ions have comparable intensities, in contrast, the [Rh2C4H2]+ product ion is much weak than [Rh2C]+ and [Rh2C2H2]+ in the mass spectrum (Figure 4).

The reactions of transition metal carbide ions with methane have previously been studied using mass spectrometric methods in the gas phase under room-temperature or even high-temperature conditions.30−41 The generation of ethylene or acetylene via C–H bond activation and C–C coupling reactions has been reported for some metal carbide cation reactions.30−32,35 C–H bond activation and dehydrogenation of methane has also been observed for metal carbide anions.38−40 The [Rh2C3]+ cation exhibits reactivity toward methane. Besides the production of acetylene, the generation of allene or propyne is also observed as a major reaction channel. The isotopic-labeled experiments reveal two different formation mechanisms of the allene or propyne product, demonstrating that the linear C3 moiety of [Rh2C3]+ can be effectively replaced by the bare carbon atom of methane with all four C–H bonds being activated.

The calculations indicate that the rhodium centers in [Rh2C3]+ are the reactive sites for methane activation. Natural population analysis shows that both rhodium centers are positively charged in the linear [Rh2C3]+ cation (+0.80 e and +0.82 e in the doublet and quartet states for the rhodium center with longer Rh–C bond length; + 0.46 e and +0.48 e for the rhodium center with shorter Rh–C bond length, see Figure S10), which can interact with methane via ion-induced dipole interactions in forming weakly bound complex. The coordination elongates the C–H bonds of methane from 1.09 to 1.10 Å, which facilitates the C–H bond activation. Calculations indicate that the first C–H bond activation takes place on one rhodium center in forming the oxidative C–H bond insertion intermediate 22, from which the hydride H atom can further be transferred to the nearby carbon atom. The process from 22 to 23 is predicted to be the rate-determining step that requires overcoming the highest barrier. Thus, 22 serves as a key intermediate along the reaction paths. It has been shown that the ground-state neutral rhodium atom is reactive toward methane and undergoes oxidative C–H bond insertion to form the HRhCH3 species even at cryogenic temperatures.69 However, previous studies indicate that the Rh+ cation is unreactive toward methane at thermal energies.70 These studies imply that the charge of the metal center is not an important factor on the reactivity as the rate-determining step was predicted to be hydrogen/hydride transfer process. Previous investigations indicate that some dinuclear metal complexes and clusters exhibit much higher reactivity than mononuclear species toward small molecule activation such as methane and dinitrogen.71−76 The cooperation of two metal centers could facilitate the activation processes. The investigation on methane activation by rhodium clusters implies that although the atomic Rh+ is not able to dehydrogenate methane at room temperature, the dimer cation Rh2+ reacts with methane to form the dehydrogenated product Rh2CH2+.24,70

Conclusions

The dinuclear metal carbide ions [Rh2C3]+ are generated in the gas phase. It is characterized by infrared photodissociation spectroscopy as well as quantum chemical calculations to have an unsymmetrical linear [Rh–C–C–C-Rh]+ structure existing in two nearly isoenergetic doublet and quartet spin states. Mass spectrometric studies on the reactions of the [Rh2C3]+ ion with CH4 in the gas phase at room temperature show that three reaction channels are observed with a quite low reaction efficiency. The first channel is the formation of the [Rh2C]+ cation with the release of an allene or propyne neutral C3H4. The second channel is the generation of the [Rh2C2H2]+ ion with the concomitant elimination of an acetylene molecule. The third channel is the generation of the [Rh2C4H2]+ ion with the release of a dihydrogen molecule. The production of [Rh213C]+ + C3H4 using isotopic-labeled 13CH4 sample indicates that the linear C3 moiety of the [Rh2C3]+ reactant can be replaced by the bare carbon atom of methane with all the four C–H bonds being activated. The calculations suggest that the overall reactions are thermodynamically exothermic, and that the two Rh centers are the reactive sites for C–H bond activation and hydrogen atom transfer reactions. The results may provide useful information in understanding multifaceted mechanisms of methane activation at ambient conditions.

Acknowledgments

The authors appreciate an anonymous reviewer for the constructive suggestions, in particular, the explanation for the 2:1 ratio of [Rh2C]+ and [Rh213C]+ observed in the experiments. The authors gratefully acknowledge financial support from the National Natural Science Foundation of China (Grants 21603037, 21688102, 21973016, 21927805, and 21803013).

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacsau.1c00265.

  • Experimental mass spectra, calculated geometries and potential energy profiles (PDF)

The authors declare no competing financial interest.

Supplementary Material

au1c00265_si_001.pdf (1MB, pdf)

References

  1. Ruscic B. Active Thermochemical Tables: Sequential Bond Dissociation Enthalpies of Methane, Ethane, and Methanol and the Related Thermochemistry. J. Phys. Chem. A 2015, 119, 7810–7837. 10.1021/acs.jpca.5b01346. [DOI] [PubMed] [Google Scholar]
  2. Crabtree R. H. Aspects of Methane Chemistry. Chem. Rev. 1995, 95, 987–1007. 10.1021/cr00036a005. [DOI] [Google Scholar]
  3. Dyker G. Transition Metal Catalyzed Coupling Reactions Under C-H Activation. Angew. Chem., Int. Ed. 1999, 38, 1698–1712. . [DOI] [PubMed] [Google Scholar]
  4. Schwach P.; Pan X. L.; Bao X. H. Direct Conversion of Methane to Value-Added Chemicals over Heterogeneous Catalysts: Challenges and Prospects. Chem. Rev. 2017, 117, 8497–8520. 10.1021/acs.chemrev.6b00715. [DOI] [PubMed] [Google Scholar]
  5. Gunsalus N. J.; Koppaka A.; Park S. H.; Bischof S. M.; Hashiguchi B. G.; Periana R. A. Homogeneous Functionalization of Methane. Chem. Rev. 2017, 117, 8521–8573. 10.1021/acs.chemrev.6b00739. [DOI] [PubMed] [Google Scholar]
  6. Zhang Q.; Yu J. H.; Corma A. Applications of Zeolites to C1 Chemistry: Recent Advances, Challenges, and Opportunities. Adv. Mater. 2020, 32, 2002927. 10.1002/adma.202002927. [DOI] [PubMed] [Google Scholar]
  7. Hickman D. A.; Schmidt L. D. Production of Syngas by Direct Catalytic Oxidation of Methane. Science 1993, 259, 343–346. 10.1126/science.259.5093.343. [DOI] [PubMed] [Google Scholar]
  8. Guo X. G.; Fang G. Z.; Li G.; Ma H.; Fan H. J.; Yu L.; Ma C.; Wu X.; Deng D. H.; Wei M. M.; Tan D. L.; Si R.; Zhang S.; Li J. Q.; Sun L. T.; Tang Z. C.; Pan X. L.; Bao X. H. Direct, Nonoxidative Conversion of Methane to Ethylene, Aromatics, and Hydrogen. Science 2014, 344, 616–619. 10.1126/science.1253150. [DOI] [PubMed] [Google Scholar]
  9. Tomkins P.; Ranocchiari M.; van Bokhoven J. A. Direct Conversion of Methane to Methanol Under Mild Conditions Over Cu Zeolites and Beyond. Acc. Chem. Res. 2017, 50, 418–425. 10.1021/acs.accounts.6b00534. [DOI] [PubMed] [Google Scholar]
  10. Agarwal N.; Freakley S. J.; McVicker R. U.; Althahban S. M.; Dimitratos N.; He Q.; Morgan D. J.; Jenkins R. L.; Willock D. J.; Taylor S. H.; Kiely C. J.; Hutchings J. G. Aqueous Au-Pd Colloids Catalyze Selective CH4 Oxidation to CH3OH with O2 Under Mild Conditions. Science 2017, 358, 223–226. 10.1126/science.aan6515. [DOI] [PubMed] [Google Scholar]
  11. Liang Z.; Li T.; Kim M.; Asthagiri A.; Weaver J. F. Low-Temperature Activation of Methane on the IrO2(110) Surface. Science 2017, 356, 299–303. 10.1126/science.aam9147. [DOI] [PubMed] [Google Scholar]
  12. Diaz-Urrutia C.; Ott T. Activation of Methane to CH3+: A Selective Industrial Route to Methanesulfonic Acid. Science 2019, 363, 1326–1329. 10.1126/science.aav0177. [DOI] [PubMed] [Google Scholar]
  13. Song Y. D.; Ozdemir E.; Ramesh S.; Adishev A.; Subramanian S.; Harale A.; Albuali M.; Fadhel B. A.; Jamal A.; Moon D.; Choi S. H.; Yavuz C. T. Dry Reforming of Methane by Stable Ni-Mo Nanocatalysts on Single-Crystalline MgO. Science 2020, 367, 777–781. 10.1126/science.aav2412. [DOI] [PubMed] [Google Scholar]
  14. Wang G. J.; Zhou M. F. Probing the Intermediates in the MO + CH4 ↔ M + CH3OH Reactions by Matrix Isolation Infrared Spectroscopy. Int. Rev. Phys. Chem. 2008, 27, 1–25. 10.1080/01442350701685946. [DOI] [Google Scholar]
  15. Roithová J.; Schröder D. Selective Activation of Alkanes by Gas Phase Metal Ions. Chem. Rev. 2010, 110, 1170–1211. 10.1021/cr900183p. [DOI] [PubMed] [Google Scholar]
  16. Schwarz H. Chemistry with Methane: Concepts Rather than Recipes. Angew. Chem., Int. Ed. 2011, 50, 10096–10115. 10.1002/anie.201006424. [DOI] [PubMed] [Google Scholar]
  17. Schwarz H. Thermal Hydrogen-Atom Transfer from Methane: A Mechanistic Exercise. Chem. Phys. Lett. 2015, 629, 91–101. 10.1016/j.cplett.2015.04.022. [DOI] [Google Scholar]
  18. Zhao Y. X.; Li Z. Y.; Yang Y.; He S. G. Methane Activation by Gas Phase Atomic Clusters. Acc. Chem. Res. 2018, 51, 2603–2610. 10.1021/acs.accounts.8b00403. [DOI] [PubMed] [Google Scholar]
  19. Irikura K. K.; Beauchamp J. L. Electronic Structure Considerations for Methane Activation by Third-Row Transition-Metal Ions. J. Phys. Chem. 1991, 95, 8344–8351. 10.1021/j100174a057. [DOI] [Google Scholar]
  20. Ranasinghe Y. A.; MacMahon T. J.; Freiser B. S. Formation of Thermodynamically Stable Dications In the Gas Phase by Thermal Ion–Molecule Reactions: Ta2+ and Zr2+ with Small Alkanes. J. Phys. Chem. 1991, 95, 7721–7726. 10.1021/j100173a032. [DOI] [Google Scholar]
  21. Owen C. J.; Boles G. C.; Chernyy V.; Bakker J. M.; Armentrout P. B. Structures of the Dehydrogenation Products of Methane Activation by 5d Transition Metal Cations Revisited: Deuterium Labeling and Rotational Contours. J. Chem. Phys. 2018, 148, 044307. 10.1063/1.5016820. [DOI] [PubMed] [Google Scholar]
  22. Achatz U.; Berg C.; Joos S.; Fox B. S.; Beyer M. K.; Niedner-Schatteburg G.; Bondybey V. E. Methane Activation by Platinum Cluster Ions in the Gas Phase: Effects of Cluster Charge on the Pt Tetramer. Chem. Phys. Lett. 2000, 320, 53–58. 10.1016/S0009-2614(00)00179-2. [DOI] [Google Scholar]
  23. Shayesteh A.; Lavrov V. V.; Koyanagi G. K.; Bohme D. K. Reactions of Atomic Cations with Methane: Gas Phase Room-Temperature Kinetics and Periodicities in Reactivity. J. Phys. Chem. A 2009, 113, 5602–5611. 10.1021/jp900671c. [DOI] [PubMed] [Google Scholar]
  24. Albert G.; Berg C.; Beyer M.; Achatz U.; Joos S.; Niedner-Schatteburg G.; Bondybey V. E. Methane Activation by Rhodium Cluster Argon Complexes. Chem. Phys. Lett. 1997, 268, 235–241. 10.1016/S0009-2614(97)00202-9. [DOI] [Google Scholar]
  25. Brungs A. J.; York A. P. E.; Green M. L. H. Comparison of the Group V and VI Transition Metal Carbides for Methane Dry Reforming and Thermodynamic Prediction of Their Relative Stabilities. Catal. Lett. 1999, 57, 65–69. 10.1023/A:1019062608228. [DOI] [Google Scholar]
  26. Alexander A. M.; Hargreaves J. S. J. Alternative Catalytic Materials: Carbides, Nitrides, Phosphides and Amorphous Boron Alloys. Chem. Soc. Rev. 2010, 39, 4388–4401. 10.1039/b916787k. [DOI] [PubMed] [Google Scholar]
  27. Wan W. M.; Tackett B. M.; Chen J. G. G. Reactions of Water and C1Molecules on Carbide and Metal-Modified Carbide Surfaces. Chem. Soc. Rev. 2017, 46, 1807–1823. 10.1039/C6CS00862C. [DOI] [PubMed] [Google Scholar]
  28. Prats H.; Gutierrez R. A.; Pinero J. J.; Vines F.; Bromley S. T.; Ramirez P. J.; Rodriguez J. A.; Illas F. Room Temperature Methane Capture and Activation by Ni Clusters Supported on TiC(001): Effects of Metal-Carbide Interactions on the Cleavage of the C-H Bond. J. Am. Chem. Soc. 2019, 141, 5303–5313. 10.1021/jacs.8b13552. [DOI] [PubMed] [Google Scholar]
  29. Figueras M.; Gutierrez R. A.; Prats H.; Vines F.; Ramirez P. J.; Illas F.; Rodriguez J. A. Boosting the Activity of Transition Metal Carbides Towards Methane Activation by Nanostructuring. Phys. Chem. Chem. Phys. 2020, 22, 7110–7118. 10.1039/D0CP00228C. [DOI] [PubMed] [Google Scholar]
  30. Li J. L.; Zhou S. D.; Schlangen M.; Weiske T.; Schwarz H. Hidden Hydride Transfer as a Decisive Mechanistic Step in the Reactions of the Unligated Gold Carbide [AuC]+ with Methane under Ambient Conditions. Angew. Chem., Int. Ed. 2016, 55, 13072–13075. 10.1002/anie.201606707. [DOI] [PubMed] [Google Scholar]
  31. Schwarz H.; Shaik S.; Li J. L. Electronic Effects on Room-Temperature, Gas-Phase C-H Bond Activations by Cluster Oxides and Metal Carbides: The Methane Challenge. J. Am. Chem. Soc. 2017, 139, 17201–17212. 10.1021/jacs.7b10139. [DOI] [PubMed] [Google Scholar]
  32. Geng C. Y.; Li J. L.; Weiske T.; Schlangen M.; Shaik S.; Schwarz H. Electrostatic and Charge-Induced Methane Activation by a Concerted Double C-H Bond Insertion. J. Am. Chem. Soc. 2017, 139, 1684–1689. 10.1021/jacs.6b12514. [DOI] [PubMed] [Google Scholar]
  33. Geng C. Y.; Weiske T.; Li J. L.; Shaik S.; Schwarz H. Intrinsic Reactivity of Diatomic 3d Transition-Metal Carbides in the Thermal Activation of Methane: Striking Electronic Structure Effects. J. Am. Chem. Soc. 2019, 141, 599–610. 10.1021/jacs.8b11739. [DOI] [PubMed] [Google Scholar]
  34. Geng C. Y.; Li J. L.; Weiske T.; Schwarz H. A Reaction-Induced Localization of Spin Density Enables Thermal C-H Bond Activation of Methane by Pristine FeC4+. Chem. - Eur. J. 2019, 25, 12940–12945. 10.1002/chem.201902572. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Li Z. Y.; Yuan Z.; Zhao Y. X.; He S. G. Methane Activation by Diatomic Molybdenum Carbide Cations. Chem. - Eur. J. 2014, 20, 4163–4169. 10.1002/chem.201304042. [DOI] [PubMed] [Google Scholar]
  36. Li H. F.; Li Z. Y.; Liu Q. Y.; Li X. N.; Zhao Y. X.; He S. G. Methane Activation by Iron-Carbide Cluster Anions FeC6–. J. Phys. Chem. Lett. 2015, 6, 2287–2291. 10.1021/acs.jpclett.5b00937. [DOI] [PubMed] [Google Scholar]
  37. Li H. F.; Jiang L. X.; Zhao Y. X.; Liu Q. Y.; Zhang T.; He S. G. Formation of Acetylene in the Reaction of Methane with Iron Carbide Cluster Anions FeC3– under High-Temperature Conditions. Angew. Chem., Int. Ed. 2018, 57, 2662–2666. 10.1002/anie.201712463. [DOI] [PubMed] [Google Scholar]
  38. Liu Q.-Y.; Ma J.-B.; Li Z.-Y.; Zhao C.; Ning C.-G.; Chen H.; He S.-G. Activation of Methane Promoted by Adsorption of CO on Mo2C2– Cluster Anions. Angew. Chem., Int. Ed. 2016, 55, 5760–5764. 10.1002/anie.201600618. [DOI] [PubMed] [Google Scholar]
  39. Li H. F.; Zhao Y. X.; Yuan Z.; Liu Q. Y.; Li Z. Y.; Li X. N.; Ning C. G.; He S. G. Methane Activation by Tantalum Carbide Cluster Anions Ta2C4–. J. Phys. Chem. Lett. 2017, 8, 605–610. 10.1021/acs.jpclett.6b02568. [DOI] [PubMed] [Google Scholar]
  40. Cassady C. J.; Mcelvany S. W. Gas Phase Reactions of Tantalum Carbide Cluster Ions with Deuterium and Small Hydrocarbons. J. Am. Chem. Soc. 1990, 112, 4788–4797. 10.1021/ja00168a025. [DOI] [Google Scholar]
  41. Hirabayashi S.; Ichihashi M. Activation of Methane by Tungsten Carbide and Nitride Cluster Cations. J. Phys. Chem. A 2020, 124, 5274–5279. 10.1021/acs.jpca.0c00749. [DOI] [PubMed] [Google Scholar]
  42. Wang G. J.; Chi C. X.; Xing X. P.; Ding C. F.; Zhou M. F. A Collinear Tandem Time-of-Flight Mass Spectrometer for Infrared Photodissociation Spectroscopy of Mass-Selected Ions. Sci. China: Chem. 2014, 57, 172–177. 10.1007/s11426-013-4979-5. [DOI] [Google Scholar]
  43. Wu X. N.; Liu Z. Z.; Wu H. C.; Zhang D.; Li W.; Huang Z. J.; Wang G. J.; Xu F. X.; Ding C. F.; Zhou M. F. Reactions of Transition-Metal Carbyne Cations with Ethylene in the Gas Phase. J. Phys. Chem. A 2020, 124, 2628–2633. 10.1021/acs.jpca.0c00371. [DOI] [PubMed] [Google Scholar]
  44. Westergren J.; Grönbeck H.; Kim S. G.; Tománek D. Noble Gas Temperature Control of Metal Clusters: A Molecular Dynamics Study. J. Chem. Phys. 1997, 107, 3071–3079. 10.1063/1.474662. [DOI] [Google Scholar]
  45. Frisch M. J.; Trucks G.; Schlegel H. B.; Scuseria G. E.; Robb M. A.; Cheeseman J. R.; Scalmani G.; Barone V.; Mennucci B.; Petersson G. A.. et al. Gaussian 09, Revision A.01; Gaussian, Inc.: Wallingford CT, 2009.
  46. Lee C. T.; Yang W. T.; Parr R. G. Development of the Colle-Salvetti Correlation-Energy Formula into a Functional of the Electron-Density. Phys. Rev. B: Condens. Matter Mater. Phys. 1988, 37, 785–789. 10.1103/PhysRevB.37.785. [DOI] [PubMed] [Google Scholar]
  47. Becke A. D. Density-Functional Thermochemistry. 3. The Role of Exact Exchange. J. Chem. Phys. 1993, 98, 5648–5652. 10.1063/1.464913. [DOI] [Google Scholar]
  48. Weigend F.; Ahlrichs R. Balanced Basis Sets of Split Valence, Triple Zeta Valence and Quadruple Zeta Valence Quality for H to Rn: Design and Assessment of Accuracy. Phys. Chem. Chem. Phys. 2005, 7, 3297–3305. 10.1039/b508541a. [DOI] [PubMed] [Google Scholar]
  49. Grimme S.; Antony J.; Ehrlich S.; Krieg H. A Consistent and Accurate ab Initio Parametrization of Density Functional Dispersion Correction (DFT-D) for the 94 Elements H-Pu. J. Chem. Phys. 2010, 132, 154104. 10.1063/1.3382344. [DOI] [PubMed] [Google Scholar]
  50. Lu T.Molclus Program; Beijing Kein Research Center for Natural Science: Beijing, 2016; http://www.keinsci.com/research/molclus.html (accessed on 2021-07-04).
  51. Ruscic B.; Bross D. H.. Active Thermochemical Tables (ATcT) values based on ver. 1.122p of the Thermochemical Network. Argonne National Laboratory.https://atct.anl.gov/Thermochemical%20Data/version%201.122p/index.php.
  52. Robinson M. S.; Polak M. L.; Bierbaum V. M.; DePuy C. H.; Lineberger W. C. Experimental Studies of Allene, Methylacetylene, and the Propargyl Radical: Bond Dissociation Energies, Gas-Phase Acidities, and Ion—Molecule Chemistry. J. Am. Chem. Soc. 1995, 117, 6766–6778. 10.1021/ja00130a017. [DOI] [Google Scholar]
  53. Chen Y. M.; Elkind J. L.; Armentrout P. B. Reactions of Ru+, Rh+, Pd+, and Ag+ with H2, HD, and D2. J. Phys. Chem. 1995, 99, 10438–10445. 10.1021/j100026a004. [DOI] [Google Scholar]
  54. Chen Y. M.; Armentrout P. B. Activation of C2H6, C3H8, and c-C3H6 Gas-Phase Rh+ and the Thermochemistry of Rh-Ligand Complexes. J. Am. Chem. Soc. 1995, 117, 9291–9304. 10.1021/ja00141a022. [DOI] [Google Scholar]
  55. Kramida A.; Ralchenko Y.; Reader J.. NIST Atomic Spectra Database, ver. 5.8); National Institute of Standards and Technology: Gaithersburg, MD; https://physics.nist.gov/asd (accessed 2021-08-10)..
  56. Peng C. Y.; Ayala P. Y.; Schlegel H. B.; Frisch M. J. Using Re-dundant Internal Coordinates to Optimize Equilibrium Geometries and Transition States. J. Comput. Chem. 1996, 17, 49–56. . [DOI] [Google Scholar]
  57. Fukui K. The Path of Chemical-Reactions - the IRC Approach. Acc. Chem. Res. 1981, 14, 363–368. 10.1021/ar00072a001. [DOI] [Google Scholar]
  58. Gonzalez C.; Schlegel H. B. Reaction-Path Following in Mass-Weighted Internal Coordinates. J. Phys. Chem. 1990, 94, 5523–5527. 10.1021/j100377a021. [DOI] [Google Scholar]
  59. Computational Chemistry Comparison and Benchmark Database; National Institute of Standards and Technology, 2016; http://cccbdb.nist.gov/vibscalex.asp.
  60. Okumura M.; Yeh L. I.; Myers J. D.; Lee Y. T. Infrared Spectra of the Solvated Hydronium Ion: Vibrational Predissociation Spectroscopy of Mass-Selected H3O+(H2O)n(H2)m. J. Phys. Chem. 1990, 94, 3416–3427. 10.1021/j100372a014. [DOI] [Google Scholar]
  61. Bieske E. J.; Dopfer O. High-Resolution Spectroscopy of Cluster Ions. Chem. Rev. 2000, 100, 3963–3998. 10.1021/cr990064w. [DOI] [PubMed] [Google Scholar]
  62. Robertson W. H.; Johnson M. A. Molecular Aspects of Halide Ion Hydration: The Cluster Approach. Annu. Rev. Phys. Chem. 2003, 54, 173–213. 10.1146/annurev.physchem.54.011002.103801. [DOI] [PubMed] [Google Scholar]
  63. Duncan M. A. Infrared Spectroscopy to Probe Structure and Dynamics in Metal Ion Molecule Complexes. Int. Rev. Phys. Chem. 2003, 22, 407–435. 10.1080/0144235031000095201. [DOI] [Google Scholar]
  64. Weltner W. Jr.; Walsh P. N.; Angell C. L. Spectroscopy of Carbon Vapor Condensed in Rare-Gas Matrices at 4 and 20 K. J. Chem. Phys. 1964, 40, 1299–1305. 10.1063/1.1725312. [DOI] [Google Scholar]
  65. Hinkle K. W.; Keady J. J.; Bernath P. F. Detection of C3 in the Circumstellar Shell of IRC+10216. Science 1988, 241, 1319–1322. 10.1126/science.241.4871.1319. [DOI] [PubMed] [Google Scholar]
  66. Pople J. A.; Head-Gordon M.; Raghavachari K. Quadratic Configuration-interaction. A General Technique for Determining Electron Correlation Energies. J. Chem. Phys. 1987, 87, 5968–5975. 10.1063/1.453520. [DOI] [Google Scholar]
  67. Langevin P. A Fundamental Formula of Kinetic Theory. Ann. Chim. Phys. 1905, 5, 245. [Google Scholar]
  68. Gioumousis G.; Stevenson D. P. Reactions of Gaseous Molecule Ions with Gaseous Molecules. V. Theory. J. Chem. Phys. 1958, 29, 294–299. 10.1063/1.1744477. [DOI] [Google Scholar]
  69. Wang G. J.; Chen M. H.; Zhou M. F. Activation of Methane by Rh(0): Evidence for Direct Insertion of Rhodium into the C–H Bond at Cryogenic Temperatures. Chem. Phys. Lett. 2005, 412, 46–49. 10.1016/j.cplett.2005.05.115. [DOI] [Google Scholar]
  70. Chen Y. M.; Armentrout P. B. Activation of Methane by Gas-Phase Rh+. J. Phys. Chem. 1995, 99, 10775–10779. 10.1021/j100027a016. [DOI] [Google Scholar]
  71. Noor A.; Sobgwi Tamne E.; Qayyum S.; Bauer T.; Kempe R. Cycloaddition Reactions of a Chromium-Chromium Quintuple Bond. Chem. - Eur. J. 2011, 17, 6900–6903. 10.1002/chem.201100841. [DOI] [PubMed] [Google Scholar]
  72. Huang W. L.; Dulong F.; Khan S. I.; Cantat T.; Diaconescu P. L. Bimetallic Cleavage of Aromatic C-H Bonds by Rare-Earth-Metal Complexes. J. Am. Chem. Soc. 2014, 136, 17410–17413. 10.1021/ja510761j. [DOI] [PubMed] [Google Scholar]
  73. Adams R. D.; Rassolov V.; Wong Y. O. Binuclear Aromatic C-H Bond Activation at a Dirhenium Site. Angew. Chem., Int. Ed. 2016, 55, 1324–1327. 10.1002/anie.201508540. [DOI] [PubMed] [Google Scholar]
  74. Geng C. Y.; Li J. L.; Weiske T.; Schwarz H. Ta2+-mediated ammonia synthesis from N2 and H2 at ambient temperature. Proc. Natl. Acad. Sci. U. S. A. 2018, 115, 11680–11687. 10.1073/pnas.1814610115. [DOI] [PMC free article] [PubMed] [Google Scholar]
  75. Zhou M. F.; Jin X.; Gong Y.; Li J. Remarkable dinitrogen activation and cleavage by the Gd dimer: From dinitrogen complexes to ring and cage nitrides. Angew. Chem., Int. Ed. 2007, 46, 2911–2914. 10.1002/anie.200605218. [DOI] [PubMed] [Google Scholar]
  76. Zhao Y.; Cui J.-T.; Wang M.; Valdivielso D. Y.; Fielicke A.; Hu L.-R.; Cheng X.; Liu Q.-Y.; Li Z.-Y.; He S.-G.; Ma J.-B. Dinitrogen Fixation and Reduction by Ta3N3H0,1– Cluster Anions at Room Temperature: Hydrogen-Assisted Enhancement of Reactivity. J. Am. Chem. Soc. 2019, 141, 12592–12600. 10.1021/jacs.9b03168. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Citations

  1. Computational Chemistry Comparison and Benchmark Database; National Institute of Standards and Technology, 2016; http://cccbdb.nist.gov/vibscalex.asp.

Supplementary Materials

au1c00265_si_001.pdf (1MB, pdf)

Articles from JACS Au are provided here courtesy of American Chemical Society

RESOURCES