Dinitrogen Functionalization Affording Chromium Hydrazido Complex

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Dinitrogen Functionalization Affording Chromium Hydrazido Complex Jianhao Yin, Jiapeng Li, Gao-Xiang Wang, Zhu-Bao Yin, Wen-Xiong Zhang, and Zhenfeng Xi J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.9b00822 • Publication Date (Web): 28 Feb 2019 Downloaded from http://pubs.acs.org on February 28, 2019

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Dinitrogen Functionalization Affording Chromium Hydrazido Complex Jianhao Yin,†,# Jiapeng Li,†,# Gao-Xiang Wang,†,# Zhu-Bao Yin,† Wen-Xiong Zhang,*,† and Zhenfeng Xi*,† †

Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China Supporting Information Placeholde ABSTRACT: A series of trinuclear and dinuclear Cr(I)-N2 complexes bearing cyclopentadienyl-phosphine ligands were synthesized and characterized. Further reduction of the Cr(I)-N2 complexes generated anionic Cr(0)-N2 complexes, which could react with Me3SiCl to afford the first chromium hydrazido complex from N2 functionalization. These complexes were found to be effective catalysts for the transformation of N2 into N(SiMe3)3.

Dinitrogen activation and functionalization with transition metals is one of the most challenging topics in chemistry.[1] Complexes based on Fe,[2] Mo[3] and others have been investigated for homogeneous catalytic N2 reduction into ammonia.[4] On the other hand, catalytic reduction of N2 into N(SiMe3)3 is a complementary route for ammonia production, as N(SiMe3)3 can be converted into ammonia upon hydrolysis quantitatively.[5-10] The first successful example of this type reduction was reported by Shiina using CrCl3 as catalyst, generating 5.4 equivalents of N(SiMe3)3.[5] Since then, several homogeneous catalyst systems based on different transition metals, such as Fe,[6] Co,[7] V,[8] Mo[9] and W[9f] have been reported to be effective for catalysing N2 silylation. However, in contrast to the fact that many metals, as mentioned above, have been found to form dinitrogen complexes and some of them can catalyse the transformation of N2 into ammonia or N(SiMe3)3, examples of Cr(N2) complexes are very rare.[11]. In fact, as far as we are aware, there is only one example of well-defined chromium(0) dinitrogen complex (I, Scheme 1) capable of catalysing N2 silylation,[10] in which the intermediates of the catalytic process is not yet clear.[12,13] Rational design of ligands is crucial for transition metalmediated or catalysed N2 activation and functionalization. We have developed a convenient synthetic method for multi-substituted cyclopentadienyl-phosphine compounds (L, Scheme 1),[14,15] in which two commonly used strong coordination moieties of different steric and electronic properties are linked together. With these unique ligands, constrained geometry complexes (CGCs) of transition metals such as Cr could be anticipated to form [LCr-N2] complexes capable of N2 functionalization. Herein we report the synthesis and structural characterization of novel examples of trinuclear and dinuclear Cr(I)-N2 complexes bearing the cyclopentadienyl-phosphine ligands. The first chromium hydrazido complex and anionic [Cr(0)-N2]- complexes were realized and structurally characterized. A plausible intermediate involved in the Cr-catalyzed N2 silylation cycle was experimentally observed. In addition, the electronic structures and bondings of these Cr-N2 complexes were theoretically investigated.

Scheme 1. Top: Selected chromium dinitrogen complexes. Bottom: The first Chromium hydrazido complex and anionic LCr(0)-N2 complexes in this work.

The multi-substituted cyclopentadienyl-phosphine ligands and their corresponding potassium salts 1 could be readily prepared by our reported methods (Scheme 2).[15] Reaction of the potassium salts 1 with CrCl2 in THF at room temperature for 12 h generated chromium chloride complexes 2 in good isolated yields. Complexes 2a-c were characterized by single-crystal X-ray structural analysis (For details see Figures S30-S32 in SI). Complexes 2a-c have solution magnetic moments of 2.7 ± 0.1μB, 2.9 ± 0.1μB and 2.6 ± 0.1μB (measured by Evans’ method in C6D6) at 296 K, respectively, which are consistent with the spin-only value for an S = 1 spin state (2.83 μB). Reduction of the chromium chlorides 2 with 1 equivalent of KHBEt3 in THF under N2 gave a dark green solution from which the Cr(I)-N2 complexes 3 (3a: R = Ph, 3b: R = Cy) were obtained in 71% and 64% isolated yields as green powder (Scheme 2). Generation of H2 was detected in this reaction process at 4.51 ppm by 1H NMR, although chromium hydride species could not be isolated neither in N2 or Ar atmosphere. Complexes 3a and 3b have solution magnetic moments of 4.1 ± 0.2μB and 2.9 ± 0.1μB at 296 K, respectively.

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Selected bond lengths [Å] and angles [°]: Cr1–N1 1.825(2), Cr1– N3 1.894(3), Cr2–N2 1.826(3), Cr2–N5 1.863(3), N1–N2 1.169(4), N3–N4 1.081(5), N5–N6 1.108(5), N3–Cr1–N1 92.61(11), N2– Cr2–N5 91.95(12).

Scheme 2. Synthesis of complexes 2 and 3.

The molecular structures of 3a and 3b were characterized by single-crystal X-ray structural analysis. The ORTEP drawings of 3a and 3b are shown in Figure 1 and 2. In 3a, it shows a trinuclear structure with three chromium centers, coordinating four molecular N2 ligands: two in terminal end-on mode and the other two in bridging end-on mode (Figure 1). The N–N bond lengths of the two bridging N2 are 1.175 and 1.178 Å, which are longer than the two terminal N2 ligands (1.087, 1.051 Å). Compared with dinitrogenbridged dinuclear complexes, trinuclear complexes with multiple dinitrogen ligands are very rare.[16] When changing the phenyl groups on the phosphorus center in 2a to cyclohexyl groups (2b), dinitrogen-bridged dinuclear complex 3b was generated, probably due to the increase of steric hindrance on the phosphorus center. The structure of 3b is shown in Figure 2. Each Cr center in 3b coordinates one bridging N2 and one terminal N2, showing identical coordination environment. The N-N bond lengths of bridging and terminal N2 ligands in 3b are comparable to those found in 3a. The IR spectra of 3a and 3b showed strong vibration peaks (1739 cm-1, 1981 cm-1 for 3a; 1751 cm-1, 1962 cm-1 for 3b) assignable to the bridging and terminal dinitrogen ligands (For details see Figures S10 and S11 in SI), respectively. The 15N2-labeled sample of 3b, which was prepared under 15N2 atmosphere at room temperature, showed 15N–15N stretching vibrations at 1696 cm-1 and 1896 cm-1, being consistent with the mass difference between 15N2 and 14N2 (Figure S3).

Scheme 3. Further reduction of 2b (or 3b) affording anionic chromium dinitrogen complexes 4.

Figure 1. Molecular structure of complex 3a with thermal ellipsoids at 30% probability. H atoms are omitted for clarity. Selected bond lengths [Å] and angles [°]: Cr1–N1 1.875(6), Cr1– N5 1.873(6), Cr2–N3 1.879(8), Cr2–N2 1.816(6), Cr3–N6 1.832(6), Cr3–N7 1.902(8), N1–N2 1.171(8), N3–N4 1.169(8), N5–N6 1.092(10), N7–N8 1.054(9), N3–Cr2–N2 94.40(3), N1–Cr1–N5 99.40(3), N6–Cr3–N7 95.50(3).

Figure 2. Molecular structure of complex 3b with thermal ellipsoids at 30% probability. H atoms are omitted for clarity.

Chemical reduction of 2b with excess K, Rb, or Cs in THF under N2 atmosphere resulted in a dark red solution (Scheme 3). Reduction of 3b with excess K gave the same result. With the aid of 2.2.2-cryptand, after further workup and recrystallization, the corresponding products 4 (4a: M = K; 4b: M = Rb; 4c: M = Cs) were isolated in 57%, 51% and 46% yields as red crystalline solids, respectively. Complexes 4a−c are diamagnetic. The molecular structure of 4a is depicted in Figure 3 (for X-ray structural information of 4b and 4c, please see Figures S36 and S37 in SI). In the solid states, complexes 4a-c showed similar structures with a little difference in the interaction between the alkali metal cations M+ and the N atoms in the anionic complexes.[2h,17] The anionic parts in 4a-c are almost identical, in which each chromium center coordinates with two terminal N2 ligands. In complex 4a, there is

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no coordination interaction between the K+ and the N2 ligands. Whereas in complexes 4b and 4c, the Rb+ and Cs+ coordinate with one and four N atoms, respectively, which is probably due to the increasing size of ionic radius. The Cr–N and N–N distances in these complexes are similar (1.820 to 1.834 Å) and (1.132 to 1.151 Å), respectively. Accordingly, the N–N stretching frequencies of 4a-c in solid states (1822 cm-1, 1906 cm-1 for 4a; 1823 cm-1, 1906 cm-1 for 4b; 1822 cm-1, 1907 cm-1 for 4c; 1765 cm-1, 1844 cm-1 for 15N -4a) (Figure S13-S15) showed stronger activation of N 2 2 ligands compared with those in 3. The key bond lengths and stretching frequencies of N2 ligands in 3 and 4 are summarized in Table 1. Figure 3. Molecular structure of 4a with thermal ellipsoids at 30% probability. H atoms are omitted for clarity. Selected bond lengths [Å] and angles [°]: Cr1–N1 1.834(10), Cr1–N3 1.823(11), N1–N2 1.144(15), N3–N4 1.141(15), N1–Cr1–N3 93.79(5).

Table 1. Cr-N, N-N bond lengths, and N-N bond stretching frequencies for Cr-N2 complexes

Complex

Formal oxidation state of Cr

Cr-N (Å)

N-N (Å)

uNN (cm-1)

ref

Cr(N2) 2(PPh4NBn4)

0

1.930, 1.884

1.112, 1.120

2072, 1918

10

(dmpe) 4Cr2(C 2SiiPr3) 2( -N2)

1

1.881

1.187

11g

[(Me 3SiCC)(dmpe)2Cr]2(-N 2)

1

1.870

1.177

1680 ___

3a

1

1.816-1.902

1.054-1.171

1981(terminal), 1739(bridging) 1962(terminal), 1751(bridging)

11h This work

3b

1

1.825-1.863

1.081-1.169

4a

0

1.823, 1.834

1.141, 1.144

4b

0

1.834, 1.836

1.142, 1.146

1906, 1823

This work

4c

0

1.820-1.830

1.132-1.151

1907, 1822

This work

In order to get deeper understanding of the electronic structures of complexes 3 and 4, density function theory (DFT) calculations on 3b and 4a were carried out using Gaussian 09 (For detailed calculations, please see SI).[18] Calculations showed strong Cr(3d)to-N2(π*) back-donation in the HOMO orbitals of 3b and 4a (Figure 4). In addition, the Mulliken atomic charge distributions on the two distal N atoms (-0.270 and -0.268) in 4a are higher than those (-0.172) in 3b, indicating a more polarized nature of the terminal N2 ligand (Figure S43 and S44). The Mayer bond orders of the N–N bonds (2.35 and 2.36) in 4a are smaller than the bond orders of terminal N2 ligands in 3b (2.48), showing a higher activation of N2 in 4a. Furthermore, from the space-filling models based on the crystal structures, the terminal N2 unit had a more open site in 4a than that in bridging complexes, which might be attacked more easily by electrophiles (Figure S39).

1906, 1822

This work This work

Scheme 4. Formation of chromium hydrazido complex 5.

4a

1.0 eq. Me 3SiCl -78 °C to RT, 1 h

Cy P Cy

Et

Et

Et

Et Cr

N N SiMe3 SiMe3 5: 45%

Et

Et

Et Et Cy P Cr Cl Cy 2b: 24%

The N2 functionalization reactions were explored preliminarily. Reactions of complexes 3 and 4 with acids (H(OEt2)2BArF4, [LutH]Cl, [LutH]OTf, etc.) gave detectable amounts (~5% based on N atoms) of ammonia or hydrazine. When 4a was reacted with 1 equivalent of Me3SiCl, hydrazido complex 5 was isolated in 45% yield, along with regeneration of 2b (Scheme 4). Formation of mono-silylation product was not observed. The structure of 5 is given in Figure 5. The Cr–N distance is 1.680 Å, indicating a double bond character. The N–N distance is 1.372 Å, similar with the N–N distances in known transition metal hydrazido complexes.[6a,9b,9c,12a] Geometry optimization on 5 is in good consistence with the crystal structure. The Mayer bond order of the Cr–N and N–N bonds are 1.649 and 1.130, respectively. Calculations showed that the unpaired spin was located mainly on the Cr center as an S = 3/2 spin state in the Mulliken atomic spin density distribution (Figure S45).

Figure 4. HOMO orbitals of 3b and 4a.

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Figure 5. Molecular structure of 5 with thermal ellipsoids at 30% probability. H atoms are omitted for clarity. Selected bond lengths [Å] and angles [°]: Cr1–N1 1.680(6), N1–N2 1.372(8), N2–Si1 1.756(6), N2–Si2 1.769(6), Cr1–N1–N2 175.4(5), Si1–N2–Si2 129.8(3). Hydrazido complexes are proposed as key intermediates in N2 catalytic reduction process.[6a,9b,9c,12,13] Inspired by the isolation of 5, we explored the catalytic silylation process with complexes 2-5 to form N(SiMe3)3. The best catalytic efficiency was found when using 2c as catalyst and the product/catalyst ratio was 26.0 based on Cr atom. Although the efficiency in our system is not as high as that in Mock’s system,[10] these seminal experimental results and the isolation of complex 5 provided complementary insights for the Cr-catalyzed silylation process (For the detailed screening table, please see Table S1). In summary, we have synthesized a series of novel Cr(I)-N2 complexes as trinuclear or binuclear structures, coordinated with multiple N2 molecules. Further reduction of the dinitrogen complexes gave the anionic dinitrogen complexes as the mononuclear structure, which could react with Me3SiCl to form chromium hydrazido complex. The isolation of the chromium hydrazido complex represented one of the key intermediates in the Cr-catalyzed N2 reduction cycle. This study should have a major scientific impact on the chemistry of transition-metal (Cr in particular) mediated or catalyzed dinitrogen fixation and transformation.

ASSOCIATED CONTENT Supporting Information Experimental details, calculation details, copies of NMR and IR spectra, X-ray data for 1-5. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author [email protected]; [email protected]

Notes The authors declare no competing financial interests.

Author Contributions #

These authors contributed equally to this work.

ACKNOWLEDGMENT This work was supported by the Natural Science Foundation of China (Nos. 21690061, 21725201). We thank Mr. Chao Yu for crystal structure refinement and Mr. Botao Wu for his help in computational calculations.

REFERENCES

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(1) Selected recent reviews: (a) Stucke, N.; Flöser, B. M.; Weyrich, T.; Tuczek, F. Nitrogen Fixation Catalyzed by Transition Metal Complexes: Recent Developments. Eur. J. Inorg. Chem. 2018, 1337-1355. (b) Li, J.; Yin, J.; Yu, C.; Zhang, W.-X.; Xi, Z. Direct Transformation of N2 to NContaining Organic Compounds. Acta Chim. Sinica 2017, 75, 733-743. (c) Sickerman, N. S.; Tanifuji, K.; Hu, Y.; Ribbe, M. W. Synthetic Analogues of Nitrogenase Metallocofactors: Challenges and Developments. Chem. Eur. J. 2017, 23, 12425-12432. d) Nitrogen Fixation; Topics in Organometallic Chemistry 60; Nishibayashi, Y., Ed.; Springer: Heidelberg, 2017. (e) Burford, R. J.; Yeo, A.; Fryzuk, M. D. Dinitrogen activation by group 4 and group 5 metal complexes supported by phosphine-amido containing ligand manifolds. Coord. Chem. Rev. 2017, 334, 84-99. (f) Burford, R. J.; Fryzuk, M. D. Examining the relationship between coordination mode and reactivity of dinitrogen. Nat. Rev. Chem. 2017, 1, 0026. (g) Bezdek, M. J.; Chirik, P. J. Expanding Boundaries: N2 Cleavage and Functionalization beyond Early Transition Metals. Angew. Chem., Int. Ed. 2016, 55, 7892-7896. (h) Čorić, I.; Holland, P. L. Insight into the Iron– Molybdenum Cofactor of Nitrogenase from Synthetic Iron Complexes with Sulfur, Carbon, and Hydride Ligands. J. Am. Chem. Soc. 2016, 138, 72007211. (i) Lehnert, N.; Peters, J. C. Preface for Small-Molecule Activation: From Biological Principles to Energy Applications. Part 2: Small Molecules Related to the Global Nitrogen Cycle. Inorg. Chem. 2015, 54, 9229-9233. (j) S. F. McWilliams, S. F.; Holland, P. L. Dinitrogen Binding and Cleavage by Multinuclear Iron Complexes. Acc. Chem. Res. 2015, 48, 2059-2065. (k) Köthe, C.; Limberg, C. Late Metal Scaffolds that Activate Both, Dinitrogen and Reduced Dinitrogen Species NxHy. Z. Anorg. Allg. Chem. 2015, 641, 18-30. (2) (a) Higuchi, J.; Kuriyama, S.; Eizawa, A.; Arashiba, K.; Nakajima, K.; Nishibayashi, Y. Preparation and Reactivity of Iron Complexes Bearing Anionic Carbazole-based PNP-type Pincer Ligands toward Catalytic Nitrogen Fixation. Dalton Trans. 2018, 47, 1117-1121. (b) Chalkley, M. J.; Del Castillo, T. J.; Matson, B. D.; Roddy, J. P.; Peters, J. C. Catalytic N2to-NH3 Conversion by Fe at Lower Driving Force: A Proposed Role for Metallocene-Mediated PCET. ACS Cent. Sci. 2017, 3, 217-223. (c) Buscagan, T. M.; Oyala, P. H.; Peters, J. C. N2-to-NH3 Conversion by a triphos-Iron Catalyst and Enhanced Turnover under Photolysis. Angew. Chem., Int. Ed. 2017, 56, 6921-6926. (d) Sekiguchi, Y.; Kuriyama, S.; Eizawa, A.; Arashiba, K.; Nakajima, K.; Nishibayashi, Y. Synthesis and Reactivity of Iron-dinitrogen Complexes Bearing Anionic Methyl- and Phenyl-substituted Pyrrole-based PNP-type Pincer Ligands toward Catalytic Nitrogen Fixation. Chem. Commun. 2017, 53, 12040-12043. (e) Hill, P. J.; Doyle, L. R.; Crawford, A. D.; Myers, W. K.; Ashley, A. E. Selective Catalytic Reduction of N2 to N2H4 by a Simple Fe Complex. J. Am. Chem. Soc. 2016, 138, 13521-13524. (f) Del Castillo, T. J.; Thompson, N. B.; Peters, J. C. A Synthetic Single-Site Fe Nitrogenase: High Turnover, Freeze-Quench 57Fe Mössbauer Data, and a Hydride Resting State. J. Am. Chem. Soc. 2016, 138, 5341-5350. (g) Kuriyama, S.; Arashiba, K.; Nakajima, K.; Matsuo, Y.; Tanaka, H.; Ishii, K.; Yoshizawa, K.; Nishibayashi, Y. Catalytic Transformation of Dinitrogen into Ammonia and Hydrazine by Iron-dinitrogen Complexes Bearing Pincer Ligand. Nat. Commun. 2016, 7, 12181-12189. (h) Ung, G.; Peters, J. C. LowTemperature N2 Binding to Two-Coordinate L2Fe0 Enables Reductive Trapping of L2FeN2- and NH3 Generation. Angew. Chem., Int. Ed. 2015, 54, 532-535. (i) Creutz, S. E.; Peters, J. C. Catalytic Reduction of N2 to NH3 by an Fe–N2 Complex Featuring a C-Atom Anchor. J. Am. Chem. Soc. 2014, 136, 1105-1115. (j) Anderson, J. S.; Rittle, J.; Peters, J. C. Catalytic Conversion of Nitrogen to Ammonia by an Iron Model Complex. Nature 2013, 501, 84-87. (3) (a) Eizawa, A.; Arashiba, K.; Tanaka, H.; Kuriyama, S.; Matsuo, Y.; Nakajima, K.; Yoshizawa, K.; Nishibayashi, Y. Remarkable Catalytic Activity of Dinitrogen-bridged Dimolybdenum Complexes Bearing NHCbased PCP-pincer Ligands toward Nitrogen Fixation. Nat. Commun. 2017, 8, 14874-14885. (b) Wickramasinghe, L. A.; Ogawa, T.; Schrock, R. R.; Müller, P. Reduction of Dinitrogen to Ammonia Catalyzed by Molybdenum Diamido Complexes. J. Am. Chem. Soc. 2017, 139, 9132-9135. (c) Arashiba, K.; Kinoshita, E.; Kuriyama, S.; Eizawa, A.; Nakajima, K.; Tanaka, H.; Yoshizawa, K.; Nishibayashi, Y. Catalytic Reduction of Dinitrogen to Ammonia by Use of Molybdenum-Nitride Complexes Bearing a Tridentate Triphosphine as Catalysts. J. Am. Chem. Soc. 2015, 137, 5666-5669. (d) Kuriyama, S.; Arashiba, K.; Nakajima, K.; Tanaka, H.; Kamaru, N.; Yoshizawa, K.; Nishibayashi, Y. Catalytic Formation of Ammonia from Molecular Dinitrogen by Use of Dinitrogen-Bridged Dimolybdenum-Dinitrogen Complexes Bearing PNP-Pincer Ligands: Remarkable Effect of Substituent at PNP-Pincer Ligand. J. Am. Chem. Soc. 2014, 136, 9719-9731. (e) Tanaka, H.; Arashiba, K.; Kuriyama, S.; Sasada, A.; Nakajima, K.; Yoshizawa, K.; Nishibayashi, Y. Unique Behaviour of

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Dinitrogen-bridged Dimolybdenum Complexes Bearing Pincer Ligand towards Catalytic Formation of Ammonia. Nat. Commun. 2014, 5, 37373747. (f) Kinoshita, E.; Arashiba, K.; Kuriyama, S.; Miyake, Y.; Shimazaki, R.; Nakanishi, H.; Nishibayashi, Y. Synthesis and Catalytic Activity of Molybdenum–Dinitrogen Complexes Bearing Unsymmetric PNP-Type Pincer Ligands. Organometallics 2012, 31, 8437-8443. (g) Arashiba, K.; Miyake, Y.; Nishibayashi, Y. A Molybdenum Complex Bearing PNP-type Pincer Ligands Leads to the Catalytic Reduction of Dinitrogen into Ammonia. Nat. Chem. 2011, 3, 120-125. (h) Schrock, R. R. Catalytic Reduction of Dinitrogen to Ammonia by Molybdenum: Theory versus Experiment. Angew. Chem., Int. Ed. 2008, 47, 5512-5522. (i) Weare, W. W.; Dai, X.; Byrnes, M. J.; Chin, J. M.; Schrock, R. R. Catalytic Reduction of Dinitrogen to Ammonia at a Single Molybdenum Center. Proc. Natl. Acad. Sci. 2006, 103, 17099-17106. (j) Schrock, R. R. Catalytic Reduction of Dinitrogen to Ammonia at a Single Molybdenum Center. Acc. Chem. Res. 2005, 38, 955-962. (k) Ritleng, V.; Yandulov, D. V.; Weare, W. W.; Schrock, R. R.; Hock, A. S.; Davis, W. M. Molybdenum Triamidoamine Complexes that Contain Hexa-tert-butylterphenyl, Hexamethylterphenyl, or p-Bromohexaisopropylterphenyl Substituents. An Examination of Some Catalyst Variations for the Catalytic Reduction of Dinitrogen. J. Am. Chem. Soc. 2004, 126, 6150-6163. (l) Yandulov, D. V.; Schrock, R. R. Catalytic Reduction of Dinitrogen to Ammonia at a Single Molybdenum Center. Science 2003, 301, 76-78. (4) (a) Sekiguchi, Y.; Arashiba, K.; Tanaka, H.; Eizawa, A.; Nakajima, K.; Yoshizawa, K.; Nishibayashi, Y. Catalytic Reduction of Molecular Dinitrogen to Ammonia and Hydrazine Using Vanadium Complexes. Angew. Chem., Int. Ed. 2018, 57, 9064-9068. (b) Doyle, L. R.; Wooles, A. J.; Jenkins, L. C.; Tuna, F.; McInnes, E. J. L.; Liddle, S. T. Catalytic Dinitrogen Reduction to Ammonia at a Triamidoamine-Titanium Complex. Angew. Chem., Int. Ed. 2018, 57, 6314-6318. (c) Fajardo Jr, J.; Peters, J. C. Catalytic Nitrogen-to-Ammonia Conversion by Osmium and Ruthenium Complexes. J. Am. Chem. Soc. 2017, 139, 16105-16108. (d) Kuriyama, S.; Arashiba, K.; Tanaka, H.; Matsuo, Y.; Nakajima, K.; Yoshizawa, K.; Nishibayashi, Y. Direct Transformation of Molecular Dinitrogen into Ammonia Catalyzed by Cobalt Dinitrogen Complexes Bearing Anionic PNP Pincer Ligands. Angew. Chem., Int. Ed. 2016, 55, 14291-14295. (e) Castillo, T. J. D.; Thompson, N. B.; Suess, D. L. M.; Ung, G.; Peters, J. C. Evaluating Molecular Cobalt Complexes for the Conversion of N2 to NH3. Inorg. Chem. 2015, 54, 9256-9262. (5) Shiina, K. Reductive Silylation of Molecular Nitrogen via Fixation to Tris(trialkylsilyl)amine. J. Am. Chem. Soc. 1972, 94, 9266-9267. (6) (a) Piascik, A. D.; Li, R.; Wilkinson, H. J.; Green, J. C.; Ashley, A. E. Fe-Catalyzed Conversion of N2 to N(SiMe3)3 via an Fe-Hydrazido Resting State. J. Am. Chem. Soc. 2018, 140, 10691-10694. (b) Bai, Y.; Zhang, J.; Cui, C. An Arene-Tethered Silylene Ligand Enabling Reversible Dinitrogen Binding to Iron and Catalytic Silylation. Chem. Commun. 2018, 54, 8124-8127. (c) Cavaillé, A.; Joyeux, B.; Saffon-Merceron, N.; Nebra, N.; Fustier-Boutignona, M.; Mézailles, N. Triphos-Fe Dinitrogen and Dinitrogen-Hydride Complexes: Relevance to Catalytic N2 Reductions. Chem. Commun. 2018, 54, 11953-11956. (d) Ferreira, R. B.; Cook, B. J.; Knight, B. J.; Catalano, V. J.; García-Serres, R.; Murray, L. J. Catalytic Silylation of Dinitrogen by a Family of Triiron Complexes. ACS Catal. 2018, 8, 7208-7212. (e) Fan, Y.; Chen, J.; Gao, Y.; Shi, M.; Deng, L. Iron Dinitrogen Complexes Supported by Tris(NHC)borate Ligand: Synthesis, Characterization, and Reactivity Study. Acta Chim. Sinica 2018, 76, 445452. (f) Araake, R.; Sakadani, K.; Tada, M.; Sakai, Y.; Ohki, Y. [Fe4] and [Fe6] Hydride Clusters Supported by Phosphines: Synthesis, Characterization, and Application in N2 Reduction. J. Am. Chem. Soc. 2017, 139, 5596-5606. (g) Prokopchuk, D. E.; Wiedner, E. S.; Walter, E. D.; Popescu, C. V.; Piro, N. A.; Kassel, W. S.; Bullock, R. M.; Mock, M. T. Catalytic N2 Reduction to Silylamines and Thermodynamics of N2 Binding at Square Planar Fe. J. Am. Chem. Soc. 2017, 139, 9291-9301. (h) Doyle, L. R.; Hill, P. J.; Wildgooseb, G. G.; Ashley, A. E. Teaching Old Compounds New Tricks: Efficient N2 Fixation by Simple Fe(N2)(diphosphine)2 Complexes. Dalton Trans. 2016, 45, 7550-7554. (i) Yuki, M.; Tanaka, H.; Sasaki, K.; Miyake, Y.; Yoshizawa, K.; Nishibayashi, Y. Iron-Catalysed Transformation of Molecular Dinitrogen into Silylamine under Ambient Conditions. Nat. Commun. 2012, 3, 1254-1259. (7) (a) Gao, Y.; Li, G.; Deng, L. Bis(dinitrogen)cobalt(−1) Complexes with NHC Ligation: Synthesis, Characterization, and Their Dinitrogen Functionalization Reactions Affording Side-on Bound Diazene Complexes. J. Am. Chem. Soc. 2018, 140, 2239-2250. (b) Suzuki, T.; Fujimoto, K.; Takemoto, Y.; Wasada-Tsutsui, Y.; Ozawa, T.; Inomata, T.; Fryzuk, M. D.; Masuda, H. Efficient Catalytic Conversion of Dinitrogen to N(SiMe3)3 Using a Homogeneous Mononuclear Cobalt Complex. ACS Catal. 2018, 8, 3011-3015. (c) Imayoshi, R.; Nakajima, K.; Takaya, J.; Iwasawa, N.;

Nishibayashi, Y. Synthesis and Reactivity of Iron– and Cobalt–Dinitrogen Complexes Bearing PSiP-Type Pincer Ligands toward Nitrogen Fixation. Eur. J. Inorg. Chem. 2017, 3769-3778. (d) Siedschlag, R. B.; Bernales, V.; Vogiatzis, K. D.; Planas, N.; Clouston, L. J.; Bill, E.; Gagliardi, L.; Lu, C. C. Catalytic Silylation of Dinitrogen with a Dicobalt Complex. J. Am. Chem. Soc. 2015, 137, 4638-4641. (e) Imayoshi, R.; Tanaka, H.; Matsuo, Y.; Yuki, M.; Nakajima, K.; Yoshizawa, K.; Nishibayashi, Y. Cobalt-Catalyzed Transformation of Molecular Dinitrogen into Silylamine under Ambient Reaction Conditions. Chem. Eur. J. 2015, 21, 8905-8909. (8) Imayoshi, R.; Nakajima, K.; Nishibayashi, Y. Vanadium-Catalyzed Reduction of Molecular Dinitrogen into Silylamine under Ambient Reaction Conditions. Chem. Lett. 2017, 46, 466-468. (9) (a) Ohki, Y.; Araki, Y.; Tada, M.; Sakai, Y. Synthesis and Characterization of Bioinspired [Mo2Fe2]-Hydride Cluster Complexes and Their Application in the Catalytic Silylation of N2. Chem. Eur. J. 2017, 23, 13240-13248. (b) Liao, Q.; Saffon-Merceron, N.; Mézailles, N. N2 Reduction into Silylamine at Tridentate Phosphine/Mo Center: Catalysis and Mechanistic Study. ACS Catal. 2015, 5, 6902-6906. (c) Liao, Q.; Saffon-Merceron, N.; Mézailles, N. Catalytic Dinitrogen Reduction at the Molybdenum Center Promoted by a Bulky Tetradentate Phosphine Ligand. Angew. Chem., Int. Ed. 2014, 53, 14206-14210. (d) Ogawa, T.; Kajita, Y.; Wasada-Tsutsui, Y.; Wasada, H.; Masuda, H. Preparation, Characterization, and Reactivity of Dinitrogen Molybdenum Complexes with Bis(diphenylphosphino)amine Derivative Ligands that Form a Unique 4-Membered P-N-P Chelate Ring. Inorg. Chem. 2013, 52, 182-195. (e) Tanaka, H.; Sasada, A.; Kouno, T.; Yuki, M.; Miyake, Y.; Nakanishi, H.; Nishibayashi, Y.; Yoshizawa, K. Molybdenum-Catalyzed Transformation of Molecular Dinitrogen into Silylamine: Experimental and DFT Study on the Remarkable Role of Ferrocenyldiphosphine Ligands. J. Am. Chem. Soc. 2011, 133, 3498-3506. (f) Komori, K.; Oshita, H.; Mizobe, Y.; Hidai, M. Preparation and Properties of Molybdenum and Tungsten Dinitrogen Complexes. Catalytic Conversion of Molecular Nitrogen into Silylamines Using Molybdenum and Tungsten Dinitrogen Complexes. J. Am. Chem. Soc. 1989, 111, 1939-1940. For a Mo-based Catalytic Functionalization of N2 to Borylamine, see: (g) Espada, M. F.; Bennaamane, S.; Liao, Q.; SaffonMerceron, N.; Massou, S.; Clot, E.; Nebra, N.; Fustier-Boutignon, M.; Mézailles, N. Room-Temperature Functionalization of N2 to Borylamine at a Molybdenum Complex. Angew. Chem., Int. Ed. 2018, 57, 12865-12868. (10) Kendall, A. J.; Johnson, S. I.; Bullock, R. M.; Mock, M. T. Catalytic Silylation of N2 and Synthesis of NH3 and N2H4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P4 Macrocycle. J. Am. Chem. Soc. 2018, 140, 2528-2536. (11) (a) Egbert, J. D.; O’Hagan, M.; Wiedner, E. S.; Bullock, R. M.; Piro, N. A.; Kasselb, W. S.; Mock, M. T. Putting Chromium on the Map for N2 Reduction: Production of Hydrazine and Ammonia. A study of cis-M(N2)2 (M = Cr, Mo, W) Bis(diphosphine) Complexes. Chem. Commun. 2016, 52, 9343-9346. (b) Akturk, E. S.; Yap, G. P. A.; Theopold, K. H. MechanismBased Design of Labile Precursors for Chromium(I) Chemistry. Chem. Commun. 2015, 51, 15402-15405. (c) Mock, M. T.; Chen, S.; O’Hagan, M.; Rousseau, R.; Dougherty, W. G.; Kassel, W. S.; Bullock, R. M. Dinitrogen Reduction by a Chromium(0) Complex Supported by a 16-Membered Phosphorus Macrocycle. J. Am. Chem. Soc. 2013, 135, 11493-11496. (d) Monillas, W. H.; Young, J. F.; Yap, G. P. A.; Theopold, K. H. A WellDefined Model System for the Chromium Catalyzed Selective Oligomerization of Ethylene. Dalton Trans. 2013, 42, 9198-9210. (e) Mock, M. T.; Chen, S.; Rousseau, R.; O’Hagan, M. J.; Dougherty, W. G.; Kassel, W. S.; DuBois, D. L.; Bullock, R. M. A Rare Terminal Dinitrogen Complex of Chromium. Chem. Commun. 2011, 47, 12212-12214. (f) Monillas, W. H.; Yap, G. P. A.; Theopold, K. H. Reactivity of a Low-valent Chromium Dinitrogen Complex. Inorg. Chim. Acta. 2011, 369, 103-119. (g) Hoffert, W. A.; Rappe, A. K.; Shores, M. P. Unusual Electronic Effects Imparted by Bridging Dinitrogen: an Experimental and Theoretical Investigation. Inorg. Chem. 2010, 49, 9497-9507. (h) Berben, L. A.; Kozimor, S. A. Dinitrogen and Acetylide Complexes of Low-Valent Chromium. Inorg. Chem. 2008, 47, 4639-4647. (i) Vidyaratne, I.; Scott, J.; Gambarotta, S.; Budzelaar, P. H. M. Dinitrogen Activation, Partial Reduction, and Formation of Coordinated Imide Promoted by a Chromium Diiminepyridine Complex. Inorg. Chem. 2007, 46, 7040-7049. (j) Monillas, W. H.; Yap, G. P. A.; MacAdams, L. A.; Theopold, K. H. Binding and Activation of Small Molecules by ThreeCoordinate Cr(I). J. Am. Chem. Soc. 2007, 129, 8090-8091. (k) Zhang, Q.F.; Chim, J. L. C.; Lai, W.; Wong, W.-T.; Leung, W.-H. Bridged Dinitrogen Complexes of Iron and Chromium Porphyrins. Inorg. Chem. 2001, 40, 2470-2471. (l) Denholm, S.; Hunter, G.; Weakley, T. J. R. Dinitrogen Complexes derived from Tricarbonyl(η6-hexaethylbenzene)-chromium(0): Crystal and Molecular Structure of p-Dinitrogenbis[dicarbonyl(η6hexaethyl benzene)chromium(0)]-Toluene. J. Chem. Soc., Dalton Trans.

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1987, 2789-2791. (m) Salt, J. E.; Girolami, G. S.; Wilkinson, G. Synthesis and Characterisation of 1.2-Bis(dimethylphosphino)ethane (dmpe) Complexes of Chromium-(0) and -(IV): X-Ray Crystal Structures of transCr(N2)2(dmpe)2, cis-Cr(CO)2(dmpe)2, Cr(C2Ph2)2(dmpe)2 and CrH4(dmpe)2. J. Chem. Soc., Dalton Trans. 1985, 685-692. (n) Girolami, G. S.; Salt, J. E.; Wilkinson, G. Alkyl, Hydride, and Dinitrogen l,2Bis(dimethylphosphino)ethane Complexes of Chromium. Crystal Structures of Cr(CH3)2(dmpe)2, CrH4(dmpe)2, and Cr(N2)2(dmpe)2. J. Am. Chem. Soc. 1983, 105, 5954-5956. (o) Karsch, H. H. cisBis(dinitrogen)tetrakis(trimethylphosphane)chromium. Angew. Chem., Int. Ed. 1977, 16, 56-57. (12) (a) McWilliams, S. F.; Bill, E.; Lukat-Rodgers, G.; Rodgers, K. R.; Mercado, B. Q.; Holland, P. L. Effects of N2 Binding Mode on Iron-Based Functionalization of Dinitrogen to Form an Iron(III) Hydrazido Complex. J. Am. Chem. Soc. 2018, 140, 8586-8598. (b) Piascik, A.; Hill, D. P. J.; Crawford, A. D.; Doyle, L. R.; Greenb, J. C.; Ashley, A. E. Cationic Silyldiazenido Complexes of the Fe(diphosphine)2(N2) Platform: Structural and Electronic Models for an Elusive First Intermediate in N2 Fixation. Chem. Commun. 2017, 53, 7657-7660. (c) Suess, D. L. M.; Peters, J. C. H−H and Si−H Bond Addition to Fe=NNR2 Intermediates Derived from N2. J. Am. Chem. Soc. 2013, 135, 4938-4941. (d) Rudd, P. A.; Planas, N.; Bill, E.; Gagliardi, L.; Lu, C. C. Dinitrogen Activation at Iron and Cobalt Metallalumatranes. Eur. J. Inorg. Chem. 2013, 2013, 3898-3906. (e) Moret, M.-E.; Peters, J. C. N2 Functionalization at Iron Metallaboratranes. J. Am. Chem. Soc. 2011, 133, 18118-18121. (f) Lee, Y.; Mankad, N. P.; Peters, J. C. Triggering N2 Uptake via Redox-induced Expulsion of Coordinated NH3 and N2 Silylation at Trigonal Bipyramidal Iron. Nat. Chem. 2010, 2, 558565. (g) Betley, T. A.; Peters, J. C. Dinitrogen Chemistry from Trigonally Coordinated Iron and Cobalt Platforms. J. Am. Chem. Soc. 2003, 125, 10782-10783. (13) (a) Duman, L. M.; Farrell, W. S.; Zavalij, P. Y.; Sita, L. R. Steric Switching from Photochemical to Thermal Reaction Pathways for Enhanced Efficiency in Metal-Mediated Nitrogen Fixation. J. Am. Chem. Soc. 2016, 138, 14856-14895. (b) Liao, Q.; Cavaill, A.; Saffon-Merceron, N.; Mézailles, N. Direct Synthesis of Silylamine from N2 and a Silane: Mediated by a Tridentate Phosphine Molybdenum Fragment. Angew. Chem., Int. Ed. 2016, 55, 11212-11216. (c) Curley, J. J.; Murahashi, T.; Cummins, C. C. Synthesis and Reversible Reductive Coupling of Cationic, Dinitrogen-Derived Diazoalkane Complexes. Inorg. Chem. 2009, 48, 71817193. (d) O’Donoghue, M. B.; Davis, W. M.; Schrock, R. R. Derivatization of Dinitrogen by Molybdenum in Triamidoamine Complexes. Inorg. Chem. 1998, 37, 5149-5158. (e) Komori, K.; Sugiura, S.; Mizobe, Y.; Yamada, M.; Hidai, M. Syntheses and Some Reactions of Trimethylsilylated Dinitrogen Complexes of Tungsten and Molybdenum. Bull. Chem. Soc. Jpn. 1989, 62, 2953-2959. (14) (a) Trost, B. M.; Vidal, B.; Thommen, M. Novel Chiral Bidentate η5Cyclopentadienylphosphine Ligands: Their Asymmetric Induction at the Ruthenium(II) Center and Application in Catalysis. Chem. Eur. J. 1999, 5, 1055-1069. (b) Foerstnerb, J.; Kettenbach, R.; Goddard, R.; Butenschön, H. Improved Access to {[w-(Phosphanyl)alkyl]cyclopentadienyl) cobalt(I) Complexes: Decomplexation of the Phosphane Arm; Alkyne Complexes; Synthesis of Mononuclear Vinylidenecobalt(I) Complexes. Chem. Ber. 1996, 129, 319-325. (c) Kettenbach, R. T.; Bonrath, W.; Butenschön, H. [w(Phosphanyl)alkyl]cyclopentadienyl Complexes. Chem. Ber. 1993, 126, 1657-1669. (d) Kauffmann, T.; Ennen, J.; Lhotak, H.; Rensing, A.; Steinseifer, F.; WoItermann, A. Coupling of Well-Established Organotransition Metal Chemistry Donor Groups to Multielectron Ligands. Angew. Chem., Int. Ed. 1980, 19, 328-329. See also: (e) Yin, J.; Ye, Q.; Hao, W.; Du, S.; Gu, Y.; Zhang, W.-X.; Xi, Z. Formation of Cyclopenta[c]pyridine Derivatives from 2,5-Disubstituted Pyrroles and 1,4Dibromo-1,3-butadienes via Pyrrole Ring One-Carbon Expansion. Org. Lett. 2017, 19, 138-141. (f) Hao, W.; Wang, H.; Ye, Q.; Zhang, W.-X.; Xi, Z. Cyclopentadiene-Phosphine/Palladium-Catalyzed Synthesis of Indolizines from Pyrrole and 1,4-Dibromo-1,3-butadienes. Org. Lett. 2015, 17, 5674-5677. (g) Geng, W.; Zhang, W.-X.; Hao, W.; Xi, Z. Cyclopentadiene-Phosphine/Palladium-Catalyzed Cleavage of C-N Bonds in Secondary Amines: Synthesis of Pyrrole and Indole Derivatives from Secondary Amines and Alkenyl or Aryl Dibromides. J. Am. Chem. Soc. 2012, 134, 20230-20233. (15) (a) Wang, G.-X.; Yin, J.; Li, J.; Yin, Z.-B.; Zhang, W.-X.; Xi, Z. Synthesis and Characterization of Manganese(II) Complexes Supported by Cyclopentadienyl-phosphine Ligands. Inorg. Chem. Front. 2019, 6, 428433. (b) Xi, Z.; Song, Q.; Chen, J.; Guan, H.; Li, P. Dialkenylation of Carbonyl Groups by Alkenyllithium Compounds: Formation of Cyclopentadiene Derivatives by the Reaction of 1,4-Dilithio-1,3-dienes with Ketones and Aldehydes. Angew. Chem., Int. Ed. 2001, 40, 1913-1916.

Page 6 of 7

(c) Xi, Z.; Li, P. Deoxygenative Cycloaddition of Aldehydes with Alkynes Mediated by AlCl3 and Zirconium: Formation of Cyclopentadiene Derivatives. Angew. Chem., Int. Ed. 2000, 39, 2950-2952. (16) (a) Grubel, K.; Brennessel, W. W.; Mercado, B. Q.; Holland, P. L. Alkali Metal Control over N−N Cleavage in Iron Complexes. J. Am. Chem. Soc. 2014, 136, 16807-16816. (b) Murray, L. J.; Weare, W. W.; Shearer, J.; Mitchell, A. D.; Abboud, K. A. Isolation of a (Dinitrogen)Tricopper(I) Complex. J. Am. Chem. Soc. 2014, 136, 13502-13505. (c) Semproni, S. P.; Milsmann, C.; Chirik, P. J. Side-on Dinitrogen Complexes of Titanocenes with Disubstituted Cyclopentadienyl Ligands: Synthesis, Structure, and Spectroscopic Characterization. Organometallics 2012, 31, 3672-3682. (d) O’Donoghue, M. B.; Davis, W. M.; Schrock, R. R.; Reiff, W. M. Heterobimetallic Dinitrogen Complexes That Contain the {[N3N]MoNdN}- Ligand. Inorg. Chem. 1999, 38, 243-252. (e) Pez, G. P.; Apgar, P.; Crissey, R. K. Reactivity of [μ-(η1: η5-C5H4)](η-C5H3)3Ti2 with Dinitrogen. Structure of a Titanium Complex with a Triply Coordinated Dinitrogen Ligand. J. Am. Chem. Soc. 1982, 104, 482-490. (f) Hung, Y.-T.; Yap, G. P. A.; Theopold, K. H. Unexpected Reactions of Chromium Hydrides with a Diazoalkane. Polyhedron 2019, 157, 381-388. (17) (a) McWilliams, S. F.; Rodgers, K. R.; Lukat-Rodgers, G.; Mercado, B. Q.; Grubel, K.; Holland, P. L. Alkali Metal Variation and Twisting of the FeNNFe Core in Bridging Diiron Dinitrogen Complexes. Inorg. Chem. 2016, 55, 2960-2968. (b) Ding, K.-Y.; Pierpont, A. W.; Brennessel, W. W.; Lukat-Rodgers, G.; Rodgers, K. R.; Cundari, T. R.; Bill, E.; Holland, P. L. Cobalt-Dinitrogen Complexes with Weakened N-N Bonds. J. Am. Chem. Soc. 2009, 131, 9471-9472. (c) Pfirrmann, S.; Limberg, C.; Herwig, C.; Stöβer, R.; Ziemer, B. A Dinuclear Nickel(I) Dinitrogen Complex and its Reduction in Single Electron Steps. Angew. Chem., Int. Ed. 2009, 48, 33573361. (d) Smith, J. M.; Sadique, A. R.; Cundari, T. R.; Rodgers, K. R.; Lukat-Rodgers, G.; Lachicotte, R. J.; Flaschenriem, C. J.; Vela, J.; Holland, P. L. Studies of Low-Coordinate Iron Dinitrogen Complexes. J. Am. Chem. Soc. 2006, 128, 756-769. (e) Hammer, R.; Friedrich, H.-F.; Friedrich, P.; Huttner, G. Hexameric KN2Co[P(CH3)3]3-A Novel Potassium Dinitrogen Cluster. Angew. Chem., Int. Ed. 1977, 16, 485-486. (18) Gaussian09 (Revision C.01), Frisch, M. J.; Trucks, G. W.; Schlegel, H. B. G.; Scuseria, E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, Jr., J. A.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Keith, T.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian, Inc., Wallingford CT, 2010.

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