Mechanism of Carbon Monoxide Induced NâN Bond Cleavage of

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Mechanism of Carbon Monoxide Induced N−N Bond Cleavage of Nitrous Oxide Mediated by Molybdenum Complexes: A DFT Study Hujun Xie,*,† Liu Yang,† Xinchen Ye,† and Zexing Cao‡ †

Department of Applied Chemistry, Zhejiang Gongshang University, Hangzhou 310035, People’s Republic of China State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People’s Republic of China

‡

S Supporting Information *

ABSTRACT: The detailed mechanism of CO-induced N−N bond cleavage of N2O mediated by molybdenum complexes leading to the nitrosyl isocyanate complex has been investigated via density functional theory (DFT) calculations at the B3LYP level. On the basis of the calculations, we proposed a new reaction mechanism of CO-induced N−N bond cleavage of N2O with an overall free energy barrier of 23.6 kcal/mol, significantly lower than that of the reaction mechanism (42.2 kcal/mol) proposed by Sita et al. The calculations also indicated that CO-induced N−N bond cleavage of N2O is competitive with oxygen atom transfer (OAT) to carbon monoxide due to the comparable free energy barriers. The metal-bound carbonyl complex obtained from OAT can be recycled to give more nitrosyl isocyanate complexes. In addition, we demonstrated why the analogous tungsten complex cannot give the nitrosyl isocyanate complex via CO-induced N−N bond cleavage of N2O. The calculations are consistent with experimental observations.

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INTRODUCTION Nitrous oxide (N2O) is a harmful compound from an environmental point of view, because it contributes to the greenhouse effect and ozone layer depletion.1 Nitrous oxide has long been considered as a kinetically inert molecule.2 Over the past few decades, many efforts have been made to activate N2O, and great progress has been achieved between transition-metal complexes and nitrous oxide.3 The reactions of transition-metal complexes with N2O include four types to date: reactions to form the terminal/bridged metal oxide or oxo products,4 insertion of the oxygen atom of N2O into an M−C or M−H bond,5 oxidation of CO/PR3 ligands of the transition metal complexes,6 and nitrous oxide N−N or N−O bond cleavage reactions catalyzed by molybdenum, osmium, titanium, zirconium, and vanadium complexes.7 At present, the development of new methodologies for the N−N bond cleavage have attracted wide interest. In 1995, Cummins and co-workers8 investigated the selective N−N bond cleavage of N2O via the reaction of N2O with the Mo(III) tris-amido complex Mo[N(tBu)Ar]3 (Ar = 3,5-C6H3Me2), affording a 1:1 ratio of the terminal nitrido product Mo[N( t Bu)Ar] 3 (N) and nitrosyl product Mo[N( t Bu)Ar]3(ON). Further experiments9 favored a mechanism for the N−N bond cleavage involving the rate-determining N2O coordination along a pathway for the formation of a μ-NNO dinuclear species. Musaev and co-workers10 reported the mechanism of the reaction of nitrous oxide with the Mo(III) tris-amido complex Mo[N(tBu)Ar]3 (Ar = 3,5-C6H3Me2). The calculations favored the mononuclear mechanism for N2O © 2014 American Chemical Society

activation followed by N−N bond cleavage. Severin and coworkers11 have studied a reaction sequence involving an Nheterocyclic carbene and a vanadium complex leading to the cleavage of both N−N and N−O bonds. A highly oxophilic vanadium complex acts as a deoxygenation agent, while a highly Lewis basic N-heterocyclic carbene can weaken the N−N bond of N2O. Recently, Sita and co-workers12 have reported that carbon monoxide induced N−N bond cleavage of N2O is competitive with oxygen atom transfer to carbon monoxide mediated by a Mo(II)/Mo(IV) catalytic cycle. In the presence of CO, facile N−N bond cleavage of N2O occurs at the formal Mo(II) center within coordinatively unsaturated mononuclear species derived from Cp*Mo[N(iPr)C(Me)N(iPr)](CO)2 (Cp* = η5-C5Me5) and Cp*Mo[N(iPr)C(Me)N(iPr)]}2(μ−η1:η1-N2) under photolytic and dark conditions, respectively, to produce the nitrosyl isocyanate complex Cp*Mo[N(iPr)C(Me)N(iPr)](κN-NO)(κN-NCO). Competitive N−O bond cleavage of N2O proceeds under the same conditions to give the terminal Mo(IV) oxo complex Cp*Mo[N(iPr)C(Me)N(iPr)](O), which can be recycled efficiently via oxygen atom transfer oxidation of CO and gives greater yields of the N−N bond-cleaved product. Reversible degenerative oxygen atom transfer between CO2 and CO catalyzed by terminal molybdenum and tungsten oxo complexes has been reported in previous experiments by Sita and co-workers.13 In addition, it was found that when the Received: September 18, 2013 Published: April 1, 2014 1553

dx.doi.org/10.1021/om400935f | Organometallics 2014, 33, 1553−1562

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Scheme 1. Mechanism of CO-Induced N−N Bond Cleavage of N2O Proposed by Sita and Co-Workers

Figure 1. Free energy profiles calculated for CO-induced N−N bond cleavage of N2O mediated by molybdenum complexes proposed by Sita and co-workers shown in Scheme 1. The solvation- and entropy-corrected relative free energies are given in kcal/mol. 31+g(d,p) basis set was used for the C, O, N, and H atoms, while the Couty−Hall16 modified LANL2DZ basis sets17 with effective core potentials (ECP)18 were considered for the molybdenum and tungsten atoms. Frequency analyses have been performed to obtain the zeropoint energies (ZPE) and identify all of the stationary points as minima (zero imaginary frequency) or transition states (one imaginary frequency) on the potential energy surfaces (PES). Intrinsic reaction coordinate (IRC) calculations were also calculated for the transition states to confirm that such structures indeed connect two relevant minima.19 The calculations were carried out under 1 atm of pressure and a temperature of 298 K. The experimental observation12 showed that a mixture of the N−O bond-cleaved product (26%) and the N−N bond-cleaved product (44%) was obtained after 20 h in the dark; after 96 h, complete conversion of the oxo species occurred. The results showed that these reactions can take place in the dark; thus, the singlets are used for all complexes in the calculations. All calculations were performed with the Gaussian09 software package.20 To consider solvent effects, a continuum medium was employed to do single-point energy calculations for all of the optimized species, using UAHF radii on the conductor-like polarizable continuum model (CPCM).21 Benzene was used as the solvent, according to the experimental reaction conditions.

molybdenum complex is substituted by a tungsten complex, the reaction cannot give the nitrosyl isocyanate complex under the same reaction conditions. Despite important contributions from experimental results, a few interesting questions are still elusive. What is the detailed mechanism of CO-induced N−N bond cleavage of N2O mediated by molybdenum complexes? Is carbon monoxide induced N−N bond cleavage of nitrous oxide competitive with oxygen atom transfer to carbon monoxide? Why does the tungsten complex fail to give a similar reaction? To answer these questions, we carried out DFT calculations by investigating the mechanism of carbon monoxide induced N−N bond cleavage of N2O mediated by molybdenum complexes, and the fact that the tungsten complex cannot give the nitrosyl isocyanate complex has also been explored.

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COMPUTATIONAL DETAILS

All geometries of the reactants, intermediates, transition states, and products were fully optimized by means of DFT calculations using the hybrid Becke3LYP (B3LYP) method.14 The reliability of the chosen method has been confirmed by previous theoretical studies for the investigation of Mo-catalyzed reaction mechanism.10,15 The 61554


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Figure 2. Optimized structures for selected species involved in the CO-induced N−N bond cleavage of N2O mediated by the molybdenum complexes shown in Figure 1. Hydrogen atoms have been omitted for clarity.

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Mechanism of CO-Induced N−N Bond Cleavage of N2O. On the basis of preliminary experimental results, Sita and co-workers proposed a mechanism for CO-induced N−N bond cleavage of N2O mediated by molybdenum complexes (Scheme 1). Starting from the coordinatively unsaturated metal-bound CO complex Cp*Mo[N(iPr)C(Me)N(iPr)](CO), an intramolecular nucleophilic attack on a metal-bound CO carbon atom by a metal-bound nitrogen atom of N2O takes place, followed by Mo−N bond formation and N−N bond cleavage to give the nitrosyl isocyanate complex. Figure 1 shows the free energy profiles calculated for CO-induced N−N bond cleavage of N2O mediated by molybdenum complexes shown in Scheme 1. Key structures and transition states with selected structural parameters are displayed in Figure 2. From the Mo-bound CO complex 1, coordination of the nitrogen atom of N2O to the Mo center gives the linear N2Ocoordinated complex 2, and this step is exergonic by 5.7 kcal/ mol. Complex 2 then undergoes an intramolecular C−N bond coupling via nucleophilic attack on a metal-bound CO carbon atom by a metal-bound N2O nitrogen atom. The barrier (TS23)

RESULTS AND DISCUSSION 12

In the experiments carried out by Sita and co-workers, starting from the dinuclear end-on-bridged dinitrogen complex {Cp*Mo[N(iPr)C(Me)N(iPr)]}2(μ-η1:η1-N2), it could easily produce the electron-deficient, coordinatively unsaturated intermediate Cp*Mo[N(iPr)C(Me)N(iPr)](CO), Cp*Mo[N(iPr)C(Me)N(iPr)](O), and N2 in the presence of CO and N2O. The reaction is significantly exergonic by 84.2 kcal/mol. The complex Cp*Mo[N(iPr)C(Me)N(iPr)](CO) proceeded via CO-induced N−N bond cleavage of N2O to give the nitrosyl isocyanate complex. The complex Cp*Mo[N(iPr)C(Me)N(iPr)](O) was obtained from the N−O bond cleavage of N2O, followed by oxygen atom transfer to carbon monoxide to formthe metal-bound carbonyl complex, which could be recycled to yield more nitrosyl isocyanate complexes. It is important to note that CO-induced N−N bond cleavage of N2O is competitive with the oxygen atom transfer to carbon monoxide. Herein, we have performed DFT calculations to explore the reaction mechanism in detail. 1555


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Figure 3. Free energy profiles of the modified mechanism for the CO-induced N−N bond cleavage of N2O mediated by molybdenum complexes. The relative free energies from B3LYP and M06-2X functionals (in parentheses) are given in kcal/mol.

Figure 4. Optimized structures for selected species involved in the CO-induced N−N bond cleavage mediated by the molybdenum complexes shown in Figure 3. Hydrogen atoms have been omitted for clarity.

are in good agreement with the experimentally measured parameters in parentheses shown in Figure 2,12 suggesting that the theoretical method used in the present calculations is reasonable. In path b, starting from intermediate 3, the N−N bond breaks via TS36 to give complex 6 and NO radical. The barrier for the N−N bond dissociation is calculated to be 16.5 kcal/mol. Complex 6 then recombines one NO radical to produce the nitrosyl isocyanate complex 5. An overall free energy barrier of 42.2 kcal/mol was obtained for this path from complex 2 to TS36. A similar mechanism has also been proposed in previous calculations by Lu and Wang with a free energy barrier of 41.0 kcal/mol.22 Taking into account the results shown in Figure 1, we conclude that paths a and b are both kinetically unfavorable. In view of the energetically highly unfavorable pathway involving the proposed mechanism shown in Scheme 1, we therefore proposed a new mechanism for CO-induced N−N bond cleavage mediated by molybdenum complexes. Figure 3

for the C−N bond coupling is calculated to be 28.3 kcal/mol, and the C−N distance in TS23 is equal to 1.632 Å (Figure 2). The coupling product 3 is significantly higher in energy than that of complex 2, which is attributed to the structure of complex 3 being similar to TS23, indicating that TS23 features a late transition state. From complex 3, there are two possible reaction pathways leading to the nitrosyl isocyanate complex 5 (Figure 1). Path a considers the Mo−N bond formation followed by N−N bond cleavage to produce the final product. Path b is a radical reaction mechanism via direct N−N bond cleavage followed by the recombination of NO radical. As shown in Figure 1, in path a complex 4 is initially formed via the transition state TS34 with a barrier of 17.9 kcal/mol. From complex 4, the N−N bond cleavage occurs directly via the transition state TS45 to form complex 5. An overall barrier of 43.6 kcal/mol was calculated for this path from complex 2 to TS34. According to the calculations, the calculated structural parameters of product 5 1556


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Figure 5. Possible metal-bound N2O complexes. The solvation- and entropy-corrected relative free energies are given in kcal/mol.

N2O takes place with an overall barrier of only 16.5 kcal/mol from complex 2 to TS74. The relatively high barrier of the reaction mechanism proposed by Sita and co-workers is attributed to the instability of the 16-electron intermediate 3 (20.0 kcal/mol), while the intermediate 7 possesses an 18electron configuration (−3.7 kcal/mol), causing the transition state TS74 to have a much lower barrier. Mechanism for the Oxygen Atom Transfer to Carbon Monoxide. We then consider possible metal-bound N2O complexes. As shown in Figure 5, when we try to optimize the metal-bound N2O complexes A1−A3, it always turns to the formation of the terminal Mo(IV) oxo complex Cp*Mo[N(iPr)C(Me)N(iPr)](O) (8; Cp* = η5-C5Me5) with the release of an N2 molecule. In addition, for complexes A4 and A5, the calculations show that these two structures have energy much higher than that of complex 8 + N2, indicating that the N−O bond in complex A is easier to break. Thus, we consider that oxygen atom transfer to carbon monoxide starts from complex 8. Figure 6 shows the free energy profiles for oxygen atom

shows the free energy profiles calculated for the newly proposed pathway, and the key structures and transition states with selected structural parameters are depicted in Figure 4. Remarkably, the overall barrier of the new mechanism is predicted to be only 23.6 kcal/mol (Figure 3) from complex 2 to TS45, significantly lower than the barrier shown in Figure 1. The calculation results indicate that the new mechanism is kinetically more favorable. From complex 1, the reaction is initiated via coordination of N2O to the molybdenum center via the N end to form the linear structure 2 (Figure 3). The 1 + N2O → 2 transformation is exergonic by 5.7 kcal/mol. In the N2O-coordinated complex 2, the back-bonding interaction from the metal center to the originally coordinated CO is slightly weakened. The C−O bond of the coordinated CO is slightly shortened, while the Mo−C bond is obviously lengthened in complex 2 with respect to those in complex 1 (Figure 2). The N2O-coordinated complex 2 undergoes oxygen-bonded nitrogen atom coordination to the metal center to give the three-membered metallacycle intermediate 7 via the transition state TS27. The free energy barrier is calculated to be 19.9 kcal/mol (Figure 3). Complex 4, with two adjacent three-membered metallacycles, is then formed via an intramolecular nucleophilic attack on a metal-bound CO carbon atom by a metal-bound terminal N2O nitrogen atom. The barrier (TS74) for the C−N bond coupling is calculated to be 14.5 kcal/mol, and the C−N distance in TS74 amounts to 1.640 Å (Figure 4). Complex 4 is unstable due to the strong strain of two adjacent three-membered metallacycles, and the dihedral angle between the Mo−C−N and Mo−N−N planes in complex 4 is predicted to be 97°. Subsequently, the N−N bond dissociates to yield product 5 with a barrier (TS45) of 7.9 kcal/mol. The overall reaction from 1 + N2O to 5 is highly exergonic by 51.5 kcal/mol. On the basis of the calculations, an overall free energy barrier is predicted to be 23.6 kcal/mol (Figure 3) from complex 2 to TS45, indicating that the new mechanism is kinetically more favorable. To validate the rationality of the B3LYP functional, we have also used the M06-2X functional to reoptimize the geometries for the CO-induced N−N bond cleavage of N2O mediated by molybdenum complexes. The free energy profiles are described in Figure 3. The calculations show that the results from the M06-2X functional are consistent with those from the B3LYP functional. For the mechanism proposed by Sita and co-workers shown in Figure 1, starting from the metal-bound CO complex 1, an intramolecular nucleophilic attack on a metal-bound CO carbon atom by a metal-bound nitrogen atom of N2O takes place with a relatively high barrier of 28.3 kcal/mol from complex 2 to TS23. However, for the new proposed mechanism, intramolecular nucleophilic attack on a metal-bound CO carbon atom by a metal-bound terminal nitrogen atom of

Figure 6. Free energy profiles calculated for oxygen atom transfer to carbon monoxide mediated by molybdenum complexes. The solvation- and entropy-corrected relative free energies are given in kcal/mol.

transfer to carbon monoxide mediated by molybdenum complexes. The optimized structures with selected structural parameters are presented in Figure 7. From complex 8, coordination of first CO via the C atom to the metal center gives complex 9 and this step is endergonic by 13.6 kcal/mol. Then the C−O bond is formed via the threemembered-ring transition state TS9‑10 to give the metal-bound CO2 complex 10. An overall free energy barrier is calculated to be 24.4 kcal/mol from complex 8 to TS9‑10. The formation of complex 10 is slightly endergonic by 0.8 kcal/mol. Coordination of a second CO via the C atom to the metal center occurs 1557


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complex 5. On the basis of the calculations (Figure 6), oxygen atom transfer to carbon monoxide is reversible, which has been validated by previous experiments.13 Now the question arises as to why this molybdenum complex can engage in reversible oxygen atom transfer. According to the geometry analysis of the molybdenum complex, the supporting monocyclopentadienyl, monoamidinate (CpAm) ligand around the Mo center is key in modulating the nucleophilicity of the MoIV terminal oxo group, which can permit compatibility with products that are electrophilic in nature. The CpAm ligand moiety is able to establish the required fine thermodynamic balance for oxygen atom transfer. In addition, the small bite angle of the amidinate group may be a key structural element that affords steric access to the Mo center for coordination of the π-acceptor CO ligand, which contributes to the breaking of strong MoIV−oxo bonds. Comparison of Barriers of CO-Induced N−N Bond Cleavage of N2O and Oxygen Atom Transfer to Carbon Monoxide. For the mechanism of CO-induced N−N bond cleavage of N2O, an overall free energy barrier is predicted to be 23.6 kcal/mol (Figure 3) from complex 2 to TS45, which corresponds to the N−N bond cleavage to yield product 5. However, for the mechanism of oxygen atom transfer to carbon monoxide, an overall free energy barrier is predicted to be 24.4 kcal/mol (Figure 6) from complex 8 to TS9‑10, which involves the C−O bond formation to yield metal-bound CO2 complex 10. Thus, within the precision of this theoretical method, the barrier of CO-induced N−N bond cleavage of N2O is comparable to the barrier of oxygen atom transfer to carbon monoxide. The calculation results are consistent with experimental observations that carbon monoxide induced N−

Figure 7. Optimized structures for selected species involved in the oxygen atom transfer to carbon monoxide mediated by the molybdenum complexes shown in Figure 6. Hydrogen atoms have been omitted for clarity.

to produce complex 11, followed by release of the CO2 molecule to give the coordinatively unsaturated metal-bound carbonyl complex 1. Complex 1 can then take part in the metalmediated CO-induced N−N bond cleavage of N2O to give

Figure 8. Free energy profiles for CO-induced N−N bond cleavage of N2O mediated by tungsten complexes. The solvation- and entropy-corrected relative free energies are given in kcal/mol. 1558


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N bond cleavage of nitrous oxide is competitive with oxygen atom transfer to carbon monoxide mediated by molybdenum complexes.12 Comparison of Mo- and W-Containing Complexes for the Formation of the Nitrosyl Isocyanate Complex. As mentioned in the Introduction, when the molybdenum complex is substituted by a tungsten complex, the nitrosyl isocyanate complex was not observed in experiments.12 Thus, we consider the CO-induced N−N bond cleavage of N2O for the formation of nitrosyl isocyanate complex mediated by a tungsten complex. The free energy profiles are given in Figure 8, and the key structures are presented in Figure 9.

Figure 10. HOMO and LUMO orbitals of complexes 2 and TS27 for Mo.

Figure 9. Optimized structures for selected species involved in the CO-induced N−N bond cleavage of N2O mediated by the tungsten complexes shown in Figure 8. Hydrogen atoms have been omitted for clarity.

Comparing Figures 3 and 8, we can see that the Mocontaining complex gives a rate-determining free energy barrier of 23.6 kcal/mol (the energy of TS45 relative to 2 in Figure 3) involving the N−N bond cleavage, while the W-containing complex has a rate-determining free energy barrier of 30.5 kcal/ mol (the energy of TS27_W relative to 2_W in Figure 8) involving the oxygen-bonded nitrogen atom coordinated to the tungsten center. The barrier difference (6.9 kcal/mol) may explain the experimental observations that the tungsten complex cannot give the nitrosyl isocyanate complex.12 The next important question is why there is such a significant barrier difference. We first calculated the HOMO and LUMO orbitals of complexes 2 and TS27 for Mo (Figure 10) and complexes 2_W and TS27_W for W (Figure 11). As we can see from Figures 10 and 11, the HOMO and LUMO orbitals of Mo and W complexes are similar; thus, the orbitals may not explain the difference in the two reactions. We then examined the electron flow of the rate-determining transition state TS27_W (Scheme 2). It was found that the transition state is involved in the cleavage of the π bond between the tungsten center and terminal nitrogen atom concomitant with σ bond formation between the tungsten center and the oxygen-bonded nitrogen atom. We believe that the π bond strength between the

Figure 11. HOMO and LUMO orbitals of complexes 2_W and TS27_W for W.

Scheme 2. Electron Flow Mechanism of TS27_W

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adjacent three-membered metallacycles. Subsequently, the N− N bond dissociates to yield the nitrosyl isocyanate complex 5. An overall free energy barrier for carbon monoxide induced N− N bond cleavage of nitrous oxide is predicted to be 23.6 kcal/ mol. However, for the reaction mechanism of oxygen atom transfer to carbon monoxide, the reaction starts from the coordination of first CO to the terminal Mo(IV) oxo complex to give complex 9, followed by C−O bond coupling to generate the metal-bound CO2 complex 10. Coordination of a second CO to the metal center takes place to produce the complex 11 with the release of a CO2 molecule to form the coordinatively unsaturated metal-bound carbonyl complex 1. The overall free energy barrier is equal to 24.4 kcal/mol, corresponding to C−O bond formation. The reactions of N−N bond cleavage and oxygen atom transfer have comparable barriers, indicating that carbon monoxide induced N−N bond cleavage of nitrous oxide is competitive with oxygen atom transfer to carbon monoxide, which is in good agreement with the experimental observations. In addition, we also explain that the nitrosyl isocyanate complex was not observed in the experiments for the tungsten complex, which is attributed to the more diffuse d orbital and relativistic effects at the tungsten center compared to those at the molybdenum center, making W−N π bond cleavage even more difficult in the rate-determining transition state.

tungsten center and the terminal nitrogen atom is the key to such a significant difference. As shown in Figure 12, the

Figure 12. NPA charges of Mo complexes 2 and TS27 and W complexes 2_W and TS27_W.

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ASSOCIATED CONTENT

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AUTHOR INFORMATION

S Supporting Information *

calculation results from natural population atomic (NPA) charges23 indicate that the charges are obviously transferred from the W center to the terminal N atom of the N2O moiety, which is consistent with the electron flow mechanism. Thus, the W−N π bond in TS27_W is more difficult to break than the Mo−N π bond in TS27, which has been confirmed by the shorter distance of the W−N bond (2.422 Å in TS27_W) in comparison to the Mo−N bond (2.476 Å in TS27). A Mayer bond order (MBO) analysis24 demonstrated that the bond orders of Mo−N and W−N π bonds are calculated to be 0.33 and 1.38, respectively. The results also show that the Mo−N π bond in TS27 is easier to break than the W−N π bond in TS27_W. Therefore, it is expected that the relative free energy of the transition state TS27_W (30.5 kcal/mol) is significantly higher than that of the transition state TS27 (19.9 kcal/mol in Figure 3) due to the more diffuse d orbitals at the tungsten center. Previous calculations also showed that relativistic effects play an important role in the tungsten center, making the W−N π bond much stronger.25 In addition, the reactivity differences of similar tungsten and molybdenum complexes have also been reported in previous experimental and theoretical studies.26

A text file of all computed molecule Cartesian coordinates in .xyz format for convenient visualization and tables giving these Cartesian coordinates. This material is available free of charge via the Internet at http://pubs.acs.org. Corresponding Author

*H.X.: e-mail, [email protected]; fax, +86−571−28008900. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors acknowledge financial support from the National Science Foundation of China (21203166, 21133007, and 91127010), the Ministry of Science and Technology (2011CB808504 and 2012CB214900), the Natural Science Foundation of Zhejiang Province (Y4100620), and the State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University (No. 201112).

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CONCLUSIONS The mechanism of carbon monoxide induced N−N bond cleavage of nitrous oxide and oxygen atom transfer to carbon monoxide mediated by molybdenum complexes has been investigated with the aid of density functional theory calculations. On the basis of the calculations, we proposed a new reaction mechanism for carbon monoxide induced N−N bond cleavage of nitrous oxide. The reaction is initiated by coordination of N2O to the metal-bound carbonyl complex 1, from which an oxygen-bonded nitrogen atom coordinates to the metal center to give the three-membered metallacyclic intermediate 7, followed by an intramolecular nucleophilic attack on a metal-bound CO carbon atom by a metal-bound terminal nitrogen atom of N2O to form complex 4, with two

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Organometallics

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