Recent advances in catalytic nitrogen fixation using transition metal–dinitrogen complexes under mild reaction conditions

Levi, 2018, Mapping global flows of chemicals: from fossil fuel feedstocks to chemical products, Environ. Sci. Technol., 52, 1725, 10.1021/acs.est.7b04573 Boerner, 2019, Taking the CO2 out of NH3: scientists are working to reduce how much greenhouse gas the ammonia-making process emits, Chem. Eng. News, 97, 18 Zhang, 2020, Global nitrogen cycle: critical enzymes, organisms, and processes for nitrogen budgets and dynamics, Chem. Rev., 120, 5308, 10.1021/acs.chemrev.9b00613 Mittasch, 1951 M. Appl, Ammonia, 1. introduction, in: B. Elvers (chief Ed.), Ullmann’s Encyclopedia of Industrial Chemistry, 7th ed., Wiley-VCH, Weinheim, v3, 2011, pp. 107–137, https://doi.org/10.1002/14356007.a02_143.pub3. M. Appl, Ammonia, 2. production processes, in: B. Elvers (chief Ed.), Ullmann’s Encyclopedia of Industrial Chemistry, 7th ed., Wiley-VCH, Weinheim, v3, 2011, pp. 139–225, https://doi.org/10.1002/14356007.o02_o11. M. Appl, Ammonia, 3. production plants, in: B. Elvers (chief Ed.), Ullmann’s Encyclopedia of Industrial Chemistry, 7th ed., Wiley-VCH, Weinheim, v3, 2011, pp. 227–261, https://doi.org/10.1002/14356007.o02_o12. F.J. de Bruijn (Ed.), Biological Nitrogen Fixation, John Wiley & Sons, Hoboken, v1 and v2, 2015, https://doi.org/10.1002/9781119053095. Einsle, 2020, Structural enzymology of nitrogenase enzymes, Chem. Rev., 120, 4969, 10.1021/acs.chemrev.0c00067 Van Stappen, 2020, The spectroscopy of nitrogenases, Chem. Rev., 120, 5005, 10.1021/acs.chemrev.9b00650 Seefeldt, 2020, Reduction of substrates by nitrogenases, Chem. Rev., 120, 5082, 10.1021/acs.chemrev.9b00556 Jasniewski, 2020, Reactivity, mechanism, and assembly of the alternative nitrogenases, Chem. Rev., 120, 5107, 10.1021/acs.chemrev.9b00704 Rutledge, 2020, Electron transfer in nitrogenase, Chem. Rev., 120, 5158, 10.1021/acs.chemrev.9b00663 Tanifuji, 2020, Metal–sulfur compounds in N2 reduction and nitrogenase-related chemistry, Chem. Rev., 120, 5194, 10.1021/acs.chemrev.9b00544 2017 2019 Allen, 1973, Dinitrogen complexes of the transition metals, Chem. Rev., 73, 11, 10.1021/cr60281a002 Chatt, 1978, Recent advances in the chemistry of nitrogen fixation, Chem. Rev., 78, 589, 10.1021/cr60316a001 Hidai, 1995, Recent advances in the chemistry of dinitrogen complexes, Chem. Rev., 95, 1115, 10.1021/cr00036a008 Tanabe, 2019, Recent advances in catalytic silylation of dinitrogen using transition metal complexes, Coord. Chem. Rev., 389, 73, 10.1016/j.ccr.2019.03.004 Kim, 2020, Beyond ammonia: nitrogen–element bond forming reactions with coordinated dinitrogen, Chem. Rev., 120, 5637, 10.1021/acs.chemrev.9b00705 Masero, 2021, Dinitrogen fixation: rationalizing strategies utilizing molecular complexes, Chem. – Eur. J., 27, 3892, 10.1002/chem.202003134 A.E. Shilov, Catalytic reduction of molecular nitrogen in solutions, Russ. Chem. Bull 52 (2003) 2555–2562, Izv. Akad. Nauk. Ser. Khim. 52 (2013) 2417–2424, https://doi.org/10.1002/978111905309510.1023/b:rucb.0000019873.81002.60. Yandulov, 2003, Catalytic reduction of dinitrogen to ammonia at a single molybdenum center, Science, 301, 76, 10.1126/science.1085326 Arashiba, 2011, A molybdenum complex bearing PNP-type pincer ligands lead to the catalytic reduction of dinitrogen into ammonia, Nat. Chem., 3, 120, 10.1038/nchem.906 Arashiba, 2015, Catalytic reduction of dinitrogen to ammonia by use of molybdenum−nitride complexes bearing a tridentate triphosphine as catalysts, J. Am. Chem. Soc., 137, 5666, 10.1021/jacs.5b02579 Eizawa, 2017, Remarkable catalytic activity of dinitrogen-bridged dimolybdenum complexes bearing NHC-based PCP-pincer ligands toward nitrogen fixation, Nat. Commun., 8, 14874, 10.1038/ncomms14874 Tanabe, 2021, Comprehensive insights into synthetic nitrogen fixation assisted by molecular catalysts under ambient or mild conditions, Chem. Soc. Rev., 50, 5201, 10.1039/D0CS01341B Ashida, 2019, Molybdenum-catalysed ammonia production with samarium diiodide and alcohols or water, Nature, 568, 536, 10.1038/s41586-019-1134-2 Ashida, 2019, A practical synthesis of ammonia from nitrogen gas, samarium diiodide and water catalyzed by a molybdenum–PCP pincer complex, Synthesis, 51, 3792, 10.1055/s-0039-1690151 Ritleng, 2004, 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., 126, 6150, 10.1021/ja0306415 Weare, 2006, Catalytic reduction of dinitrogen to ammonia at a single molybdenum center, Proc. Natl. Acad. Sci. U. S. A., 103, 17099, 10.1073/pnas.0602778103 Weare, 2006, Synthesis of molybdenum complexes that contain “hybrid” triamidoamine ligands, [(hexaisopropylterphenyl-NCH2CH2)2NCH2CH2N-aryl]3–, and studies relevant to catalytic reduction of dinitrogen, Inorg. Chem., 45, 9185, 10.1021/ic0613457 Reithofer, 2010, Synthesis of [(DPPNCH2CH2)3N]3– molybdenum complexes (DPP = 3,5-(2,5-diisopropylpyrrolyl)2C6H3) and studies relevant to catalytic reduction of dinitrogen, J. Am. Chem. Soc., 132, 8349, 10.1021/ja1008213 Kinoshita, 2012, Synthesis and catalytic activity of molybdenum−dinitrogen complexes bearing unsymmetric PNP-type pincer ligands, Organometallics, 31, 8437, 10.1021/om301046t Tanaka, 2014, Unique behaviour of dinitrogen-bridged dimolybdenum complexes bearing pincer ligand towards catalytic formation of ammonia, Nat. Commun., 5, 3737, 10.1038/ncomms4737 Kuriyama, 2014, 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., 136, 9719, 10.1021/ja5044243 Kinoshita, 2015, Synthesis and catalytic activity of molybdenum–nitride complexes bearing pincer ligands, Eur. J. Inorg. Chem., 2015, 1789, 10.1002/ejic.201500017 Kuriyama, 2015, Nitrogen fixation catalyzed by ferrocene-substituted dinitrogen-bridged dimolybdenum–dinitrogen complexes: unique behavior of ferrocene moiety as redox active site, Chem. Sci., 6, 3940, 10.1039/C5SC00545K Wickramasinghe, 2017, Reduction of dinitrogen to ammonia catalyzed by molybdenum diamido complexes, J. Am. Chem. Soc., 139, 9132, 10.1021/jacs.7b04800 Arashiba, 2017, Catalytic nitrogen fixation via direct cleavage of nitrogen–nitrogen triple bond of molecular dinitrogen under ambient reaction conditions, Bull. Chem. Soc. Jpn., 90, 1111, 10.1246/bcsj.20170197 Tanabe, 2017, Catalytic conversion of dinitrogen into ammonia under ambient reaction conditions by using proton source from water, Chem. – Asian J., 12, 2544, 10.1002/asia.201701067 Itabashi, 2019, Effect of substituents on molybdenum triiodide complexes bearing PNP-type pincer ligands toward catalytic nitrogen fixation, Dalton Trans., 48, 3182, 10.1039/C8DT04975K Eizawa, 2019, Catalytic reactivity of molybdenum–trihalide complexes bearing PCP-type pincer ligands, Chem. – Asian J., 14, 2091, 10.1002/asia.201900496 Arashiba, 2019, Synthesis and catalytic reactivity of polystyrene-supported molybdenum pincer complexes toward ammonia formation, Chem. Lett., 48, 693, 10.1246/cl.190193 Itabashi, 2019, Synthesis and catalytic reactivity of bis(molybdenum-trihalide) complexes bridged by ferrocene skeleton toward catalytic nitrogen fixation, Organometallics, 38, 2863, 10.1021/acs.organomet.9b00263 Ashida, 2019, Molybdenum-catalyzed ammonia formation using simple monodentate and bidentate phosphines as auxiliary ligands, Inorg. Chem., 58, 8927, 10.1021/acs.inorgchem.9b01340 Tanabe, 2020, Preparation and reactivity of molybdenum complexes bearing pyrrole-based PNP-type pincer ligand, Chem. Commun., 56, 6933, 10.1039/D0CC02852E Arashiba, 2020, Cycling between molybdenum-dinitrogen and -nitride complexes to support the reaction pathway for catalytic formation of ammonia from dinitrogen, Chem. – Eur. J., 26, 13383, 10.1002/chem.202002200 Engesser, 2020, A Chatt-type catalyst with one coordination site for dinitrogen reduction to ammonia, Chem. – Eur. J., 26, 14807, 10.1002/chem.202003549 Arashiba, 2021, Catalytic ammonia formation with electrochemically reduced samarium diiodide from samarium triiodide and water from dinitrogen, Chem. Lett., 50, 1356, 10.1246/cl.210152 Garrido-Barros, 2021, Tandem electrocatalytic N2 fixation via concerted proton-electron transfer, ChemRxiv Ashida, 2021, Catalytic conversion of nitrogen molecule into ammonia using molybdenum complexes under ambient reaction conditions, Chem. Commun., 57, 1176, 10.1039/D0CC07146C Chalkley, 2020, Catalytic N2-to-NH3 (or -N2H4) conversion by well-defined molecular coordination complexes, Chem. Rev., 120, 5582, 10.1021/acs.chemrev.9b00638 Anderson, 2013, Catalytic conversion of nitrogen to ammonia by an iron model complex, Nature, 501, 84, 10.1038/nature12435 Kuriyama, 2016, Catalytic transformation of dinitrogen into ammonia and hydrazine by iron-dinitrogen complexes bearing pincer ligand, Nat. Commun., 7, 12181, 10.1038/ncomms12181 L.R. Doyle, A.J. Wooles, L.C. Jenkins, F. Tuna, E.J.L. McInnes, S.T. Liddle, Catalytic dinitrogen reduction to ammonia at a triamidoamine–titanium complex, Angew. Chem., Int. Ed., 57 (2018) 6314–6318, Angew. Chem. 130 (2018) 6422–6426, https://doi.org/10.1002/anie.201802576. Bae, 2021, Fixation of dinitrogen at an asymmetric binuclear titanium complex, Inorg. Chem., 60, 12813, 10.1021/acs.inorgchem.1c01050 Y. Sekiguchi, K. Arashiba, H. Tanaka, A. Eizawa, K. Nakajima, K. Yoshizawa, Y. Nishibayashi, Catalytic reduction of molecular dinitrogen to ammonia and hydrazine using vanadium complexes, Angew. Chem., Int. Ed. 57 (2018) 9064–9068, Angew. Chem. 130 (2018) 9202–9206, https://doi.org/10.1002/anie.201802310. Kokubo, 2018, Dinitrogen fixation by vanadium complexes with a triamidoamine ligand, Inorg. Chem., 57, 11884, 10.1021/acs.inorgchem.8b00982 Kokubo, 2020, Syntheses, characterizations, and crystal structures of dinitrogen-divanadium complexes bearing triamidoamine ligands, Eur. J. Inorg. Chem., 2020, 1456, 10.1002/ejic.201901123 Ashida, 2022, Catalytic reduction of dinitrogen into ammonia and hydrazine using chromium complexes bearing PCP-type pincer ligand, Chem. – Eur. J., 28, e202200557, 10.1002/chem.202200557 F. Meng, S. Kuriyama, H. Tanaka, A. Egi, K. Yoshizawa, Y. Nishibayashi, Ammonia formation catalyzed by a dinitrogen-bridged dirhenium complex bearing PNP-pincer ligands under mild reaction conditions, Angew. Chem., Int. Ed. 60 (2021) 13906–13912, Angew. Chem. 133 (2021) 14025–14031, https://doi.org/10.1002/anie.202102175. Creutz, 2014, Catalytic reduction of N2 to NH3 by an Fe−N2 complex featuring a C-atom anchor, J. Am. Chem. Soc., 136, 1105, 10.1021/ja4114962 G. Ung, J.C. Peters, Low-temperature N2 binding to two-coordinate L2Fe0 enables reductive trapping of L2FeN2– and NH3 generation, Angew. Chem., Int. Ed., 54 (2015) 532–535, Angew. Chem. 127 (2015) 542–545, https://doi.org/10.1002/anie.201409454. Del Castillo, 2016, A synthetic single-site Fe nitrogenase: high turnover, freeze-quench 57Fe Mössbauer data, and a hydride resting state, J. Am. Chem. Soc., 138, 5341, 10.1021/jacs.6b01706 Hill, 2016, Selective catalytic reduction of N2 to N2H4 by a simple Fe complex, J. Am. Chem. Soc., 138, 13521, 10.1021/jacs.6b08802 Chalkley, 2017, Catalytic N2-to-NH3 conversion by Fe at lower driving force: a proposed role for metallocene-mediated PCET, ACS Cent. Sci., 3, 217, 10.1021/acscentsci.7b00014 T.M. Buscagan, P.H. Oyala, J.C. Peters, N2-to-NH3 conversion by a triphos–iron catalyst and enhanced turnover under photolysis, Angew. Chem., Int. Ed. 56 (2017) 6921–6926, Angew. Chem. 129 (2017) 7025–7030, https://doi.org/10.1002/anie.201703244. Sekiguchi, 2017, 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., 53, 12040, 10.1039/C7CC06987A Higuchi, 2018, Preparation and reactivity of iron complexes bearing anionic carbazole-based PNP-type pincer ligands toward catalytic nitrogen fixation, Dalton Trans., 47, 1117, 10.1039/C7DT04327A Chalkley, 2018, Fe-mediated nitrogen fixation with a metallocene mediator: exploring pKa effects and demonstrating electrocatalysis, J. Am. Chem. Soc., 140, 6122, 10.1021/jacs.8b02335 Schild, 2019, Light enhanced Fe-mediated nitrogen fixation: mechanistic insights regarding H2 elimination, HER, and NH3 generation, ACS Catal., 9, 4286, 10.1021/acscatal.9b00523 Dorantes, 2020, Bimetallic iron–tin catalyst for N2 to NH3 and a silyldiazenido model intermediate, Chem. Commun., 56, 11030, 10.1039/D0CC04563B Fajardo, 2021, Tripodal P3XFe–N2 complexes (X = B, Al, Ga): effect of the apical atom on bonding, electronic structure, and catalytic N2-to-NH3 conversion, Inorg. Chem., 60, 1220, 10.1021/acs.inorgchem.0c03354 Kuriyama, 2022, Catalytic reduction of dinitrogen to ammonia and hydrazine using ironｰdinitrogen complexes bearing anionic benzene-based PCP-type pincer ligands, Bull. Chem. Soc. Jpn., 95, 683, 10.1246/bcsj.20220048 Fajardo, 2017, Catalytic nitrogen-to-ammonia conversion by osmium and ruthenium complexes, J. Am. Chem. Soc., 139, 16105, 10.1021/jacs.7b10204 Del Castillo, 2015, Evaluating molecular cobalt complexes for the conversion of N2 to NH3, Inorg. Chem., 54, 9256, 10.1021/acs.inorgchem.5b00645 S. Kuriyama, K. Arashiba, H. Tanaka, Y. Matsuo, K. Nakajima, K. Yoshizawa, Y. Nishibayashi, Direct transformation of molecular dinitrogen into ammonia catalyzed by cobalt dinitrogen complexes bearing anionic PNP pincer ligands, Angew. Chem., Int. Ed. 55 (2016) 14291–14295, Angew. Chem. 128 (2016) 14503–14507, https://doi.org/10.1002/anie.201606090. Nishibayashi, 2012, Molybdenum-catalyzed reduction of molecular dinitrogen under mild reaction conditions, Dalton Trans., 41, 7447, 10.1039/c2dt30105a Tanabe, 2013, Developing more sustainable processes for ammonia synthesis, Coord. Chem. Rev., 257, 2551, 10.1016/j.ccr.2013.02.010 Nishibayashi, 2015, Molybdenum-catalyzed reduction of molecular dinitrogen into ammonia under ambient reaction conditions, C. R. Chim., 18, 776, 10.1016/j.crci.2015.01.014 Nishibayashi, 2015, Recent progress in transition-metal-catalyzed reduction of molecular dinitrogen under ambient reaction conditions, Inorg. Chem., 54, 9234, 10.1021/acs.inorgchem.5b00881 Tanabe, 2016, Catalytic dinitrogen fixation to form ammonia at ambient reaction conditions using transition metal-dinitrogen complexes, Chem. Rec., 16, 1549, 10.1002/tcr.201600025 Nishibayashi, 2018, Development of catalytic nitrogen fixation using transition metal–dinitrogen complexes under mild reaction conditions, Dalton Trans., 47, 11290, 10.1039/C8DT02572J Kuriyama, 2021, Development of catalytic nitrogen fixation using transition metal complex not relevant to nitrogenases, Tetrahedron, 83, 13986, 10.1016/j.tet.2021.131986 Walter, 2016, Recent advances in transition metal-catalyzed dinitrogen activation, Adv. Organomet. Chem., 65, 261, 10.1016/bs.adomc.2016.03.001 Burford, 2017, Examining the relationship between coordination mode and reactivity of dinitrogen, Nat. Rev. Chem., 1, 0026, 10.1038/s41570-017-0026 Stucke, 2018, Nitrogen fixation catalyzed by transition metal complexes: recent developments, Eur. J. Inorg. Chem., 2018, 1337, 10.1002/ejic.201701326 Singh, 2020, Activation of dinitrogen by polynuclear metal complexes, Chem. Rev., 120, 5517, 10.1021/acs.chemrev.0c00042 Forrest, 2021, Nitrogen fixation via splitting into nitrido complexes, Chem. Rev., 121, 6522, 10.1021/acs.chemrev.0c00958 Ertl, 2008, Reactions at surfaces: from atoms to complexity (Nobel lecture), Angew. Chem., Int. Ed., 47, 3524, 10.1002/anie.200800480 Schrock, 2008, Catalytic reduction of dinitrogen to ammonia by molybdenum: theory versus experiment, Angew. Chem., Int. Ed., 47, 5512, 10.1002/anie.200705246 Munisamy, 2012, An electrochemical investigation of intermediates and processes involved in the catalytic reduction of dinitrogen by [HIPTN3N]Mo (HIPTN3N = (3,5-(2,4,6–i-Pr3C6H2)2C6H3NCH2CH2)3N), Dalton Trans., 41, 130, 10.1039/C1DT11287B Agarwal, 2022, Free energies of proton-coupled electron transfer reagents and their applications, Chem. Rev., 122, 1, 10.1021/acs.chemrev.1c00521 Bezdek, 2017, Determining and understanding N-H bond strengths in synthetic nitrogen fixation cycles, Top. Organomet. Chem., 60, 1 Tanaka, 2016, Interplay between theory and experiment for ammonia synthesis catalyzed by transition metal complexes, Acc. Chem. Res., 49, 987, 10.1021/acs.accounts.6b00033 Egi, 2020, Nitrogen fixation catalyzed by dinitrogen-bridged dimolybdenum complexes bearing PCP- and PNP-type pincer ligands: a shortcut pathway deduced from free energy profiles, Eur. J. Inorg. Chem., 2020, 1490, 10.1002/ejic.201901160 Hebden, 2012, Cleavage of dinitrogen to yield a (t-BuPOCOP)molybdenum(IV) nitride, Chem. Commun., 48, 1851, 10.1039/c2cc17634c Liao, 2015, N2 reduction into silylamine at tridentate phosphine/Mo center: catalysis and mechanistic study, ACS Catal., 5, 6902, 10.1021/acscatal.5b01626 Liao, 2016, Direct synthesis of silylamine from N2 and a silane: mediated by a tridentate phosphine molybdenum fragment, Angew. Chem., Int. Ed., 55, 11212, 10.1002/anie.201604812 Klopsch, 2017, Functionalization of N2 by mid to late transition metals via NｰN bond cleavage, Top. Organomet. Chem., 60, 71 Lindley, 2018, Mechanism of chemical and electrochemical N2 splitting by a rhenium pincer complex, J. Am. Chem. Soc., 140, 7922, 10.1021/jacs.8b03755 F. Schendzielorz, M. Finger, J. Abbenseth, C. Würtele, V. Krewald, S. Schneider, Metal-ligand cooperative synthesis of benzonitrile by electrochemical reduction and photolytic splitting of dinitrogen, Angew. Chem., Int. Ed. 58 (2019) 830–834, Angew. Chem. 131 (2019) 840–844, https://doi.org/10.1002/anie.201812125c. Yamamoto, 2020, Structural characterization of molybdenum-dinitrogen complex as key species toward ammonia formation by dispersive XAFS spectroscopy, Phys. Chem. Chem. Phys., 22, 12368, 10.1039/C9CP06761B K. Fagnou, M. Lautens, Halide effects in transition metal catalysis, Angew. Chem., Int, Ed. 41 (2002) 26–47, Angew. Chem. 114 (2002) 26–49, https://doi.org/10.1002/1521-3773(20020104)41:1<26::aid-anie26>3.0.co;2-9. Chciuk, 2015, Proton-coupled electron transfer in the reduction of arenes by SmI2–water complexes, J. Am. Chem. Soc., 137, 11526, 10.1021/jacs.5b07518 Kolmar, 2017, SmI2(H2O)n reduction of electron rich enamines by proton-coupled electron transfer, J. Am. Chem. Soc., 139, 10687, 10.1021/jacs.7b03667 Minimum and maximum turnover frequencies for the NH3 formation at 60 and 155 min–1 per FeMo-co are based on the reported NH3 production rates at 119 min–1 per MoFe protein taken from ref. [110] and 1,270 nmol min–1 per mg of MoFe protein (as a α2β2 tetramer with 61 kDa per subunit) taken from ref. [111], respectively. See refs. [12,14,28] for other evaluated values. Brown, 2016, Light-driven dinitrogen reduction catalyzed by a CdS:nitrogenase MoFe protein biohybrid, Science, 352, 448, 10.1126/science.aaf2091 Chisnell, 1988, Purification of a second alternative nitrogenase from a nifHDK deletion strain of Azotobacter vinelandii, J. Bacteriol., 170, 27, 10.1128/jb.170.1.27-33.1988 Anderson, 2013, Conversion of Fe–NH2 to Fe–N2 with release of NH3, J. Am. Chem. Soc., 135, 534, 10.1021/ja307714m Anderson, 2015, Characterization of an Fe≡N–NH2 intermediate relevant to catalytic N2 reduction to NH3, J. Am. Chem. Soc., 137, 7803, 10.1021/jacs.5b03432 Thompson, 2017, Nitrogen fixation via a terminal Fe(IV) Nitride, J. Am. Chem. Soc., 139, 15312, 10.1021/jacs.7b09364 Nesbit, 2019, Characterization of the earliest intermediate of Fe-N2 protonation: CW and pulse EPR detection of an Fe-NNH species and its evolution to Fe-NNH2+, J. Am. Chem. Soc., 141, 8116, 10.1021/jacs.8b12082 Leigh, 1991, Exchange of dinitrogen between iron and molybdenum centers and the reduction of dinitrogen bound to iron: implications for the chemistry of nitrogenases, J. Am. Chem. Soc., 113, 5862, 10.1021/ja00015a050 Fox, 2004, Synthesis of an iron parent amido complex and a comparison of its reactivity with the ruthenium analog, Organometallics, 23, 1656, 10.1021/om0499660 Field, 2009, Base-mediated conversion of hydrazine to diazene and dinitrogen at an iron center, Inorg. Chem., 48, 5, 10.1021/ic801856q Yelle, 2009, Theoretical studies of N2 reduction to ammonia in Fe(dmpe)2N2, Inorg. Chem., 48, 861, 10.1021/ic800930t Crossland, 2010, Iron–dinitrogen coordination chemistry: dinitrogen activation and reactivity, Coord. Chem. Rev., 254, 1883, 10.1016/j.ccr.2010.01.005 Hazari, 2010, Homogeneous iron complexes for the conversion of dinitrogen into ammonia and hydrazine, Chem. Soc. Rev., 39, 4044, 10.1039/b919680n Tyler, 2015, Mechanisms for the formation of NH3, N2H4, and N2H2 in the protonation reaction of Fe(DMeOPrPE)2N2 {DMeOPrPE = 1,2-bis[bis(methoxypropyl)phosphino]ethane}, Z. Anorg. Allg. Chem., 641, 31, 10.1002/zaac.201400126 Pappas, 2016, Catalytic proton coupled electron transfer from metal hydrides to titanocene amides, hydrazines and imides: determination of thermodynamic parameters relevant to nitrogen fixation, J. Am. Chem. Soc., 138, 13379, 10.1021/jacs.6b08009 Bezdek, 2016, Coordination-induced weakening of ammonia, water, and hydrazine X–H bonds in a molybdenum complex, Science, 354, 730, 10.1126/science.aag0246 M.J. Bezdek, P.J. Chirik, Interconversion of molybdenum imido and amido complexes by proton-coupled electron transfer, Angew. Chem., Int. Ed. 57 (2018) 2224–2228, Angew. Chem. 130 (2018) 2246–2250, https://doi.org/10.1002/anie.201708406. Parker, 1992, Homolytic bond (H–A) dissociation free energies in solution. Applications of the standard potential of the (H+/H•) couple, J. Am. Chem. Soc., 114, 7458, 10.1021/ja00045a018 Bordwell, 1993, From equilibrium acidities to radical stabilization energies, Acc. Chem. Res., 26, 510, 10.1021/ar00033a009 Chalkley, 2020, Relating N–H bond strengths to the overpotential for catalytic nitrogen fixation, Eur. J. Inorg. Chem., 2020, 1353, 10.1002/ejic.202000232 Formal redox potentials for CoCp2/CrCp*2 and CoCp*2 in MeCN are taken from refs. [130] and [131], respectively. Redox potential due to CoII/III as well as pKa value for [CpCo(η5-C5H4C6H4NMe2)]OTf in MeCN is taken from ref. [132]. Formal redox potential for Sm2+ vs SHE in H2O is taken from ref. [133]. Formal redox potentials for KC8 vs FeCp2+/0 in MeCN is calculated based on the redox potential of K+/K (–2.86 V vs SHE in MeCN) taken from ref. [134], the intercalation voltage of graphite vs K+/K (0.24 V) taken from ref. [135], and the SHE/FeCp2+/0 (–0.624 V) conversion taken from ref [136], respectively. Formal redox potential for SO2•– (in equilibrium with Na2S2O4 in aqueous solution) (–0.66 V vs NHE in H2O) is taken from ref. [137] with the NHE/SHE conversion (+0.0057 V) taken from ref. [138]. pKa values in MeCN for [LutH]+/[ColH]+/[PhNH3]+/[Ph2NH2]+, HOTs, [Cy3PH]+, and [(Et2O)2H]+ are taken from refs. [139], [140], [141], and [142], respectively. pKa value (1st dissociation constant) for [Sm(H2O)n]3+ in H2O is taken from [143], whereas pKa value (1st dissociation constant) for [Sm{(CH2OH)}n]3+ in H2O is interpolated using from the value for [Sm(H2O)n]3+ taken from [143] by using the difference between the two (–0.16) taken from [144]. BDFEeff and ΔΔGf(NH3) values at 25 °C (298.15 K) are calculated based on equations (1) and (2) with ΔG°f(H•) and CG values in MeCN or H2O are taken from ref. [95]. Robbins, 1982, Syntheses and electronic structures of decamethylmetallocenes, J. Am. Chem. Soc., 104, 1882, 10.1021/ja00371a017 Aranzaes, 2006, Metallocenes as references for the determination of redox potentials by cyclic voltammetry – permethylated iron and cobalt sandwich complexes, inhibition by polyamine dendrimers, and the role of hydroxy-containing ferrocenes, Can. J. Chem., 64, 288, 10.1139/v05-262 Chalkley, 2020, A molecular mediator for reductive concerted proton-electron transfers via electrocatalysis, Science, 369, 850, 10.1126/science.abc1607 Bratsch, 1989, Standard electrode potentials and temperature coefficients in water at 298.15 K, J. Phys. Chem. Ref. Data, 18, 1, 10.1063/1.555839 Gritzner, 2010, Standard electrode potentials of M+|M couples in non-aqueous solvents (molecular liquids), J. Mol. Liq., 156, 103, 10.1016/j.molliq.2010.03.010 Jian, 2015, Carbon electrodes for K-ion batteries, J. Am. Chem. Soc., 137, 11566, 10.1021/jacs.5b06809 Pavlishchuk, 2000, Conversion constants for redox potentials measured versus different electrodes in acetonitrile solutions at 25 °C, Inorg. Chim. Acta, 298, 97, 10.1016/S0020-1693(99)00407-7 Mayhew, 1978, The redox potential of dithionite and SO–2 from equilibrium reactions with flavodoxins, methyl viologen and hydrogen plus hydrogenase, Eur. J. Biochem., 85, 535, 10.1111/j.1432-1033.1978.tb12269.x Ramette, 1987, Outmoded terminology: the normal hydrogen electrode, J. Chem. Educ., 64, 885, 10.1021/ed064p885 Tshepelevitsh, 2019, On the basicity of organic based in different media, Eur. J. Org. Chem., 2019, 6735, 10.1002/ejoc.201900956 Kütt, 2006, A comprehensive self-consistent spectrophotometric acidity scale of neutral Brønsted acids in acetonitrile, J. Org. Chem., 71, 2829, 10.1021/jo060031y Li, 2006, First-principle predictions of basicity of organic amines and phosphines in acetonitrile, Tetrahedron, 62, 11801, 10.1016/j.tet.2006.09.018 Kolthoff, 1968, Protonation in acetonitrile of water, alcohols, and diethyl ether, J. Am. Chem. Soc., 90, 3320, 10.1021/ja01015a004 İçhedef, 2018, Hydrolytic behavior of La3+ and Sm3+ at various temperatures, J. Solution Chem., 47, 220, 10.1007/s10953-018-0727-y Manku, 1972, Lanthanon(III) complexes with ethanediol, propane-1,2-diol and glycerol in aqueous medium, J. Inorg. Nucl. Chem., 34, 357, 10.1016/0022-1902(72)80400-7 Standard transformed Gibbs free energies of the formation at 298.15 K, 1 bar, and at pH =7.0 and ionic strength 0.25 M for NH3 (as a mixture of NH4+ and NH3 in a ratio of 0.9944:0.0056 in aqueous solution) and H2 (g) are given at ΔG'f°(NH3) = 19.82 kcal/mol (82.93 kJ/mol) and ΔG'f°(H2) = 19.49 kcal/mol (99.13 kJ/mol), respectively, according to ref. [146], whereas the standard transformed Gibbs free energy change for the hydrolysis of ATP at pMg = 2 is given as –7.36 kcal/mol (–30.80 kJ/mol) according to ref. [147]. In case that reduction is carried out by SO2•– (in equilibrium with Na2S2O4 in H2O) with the redox potential at –0.654 V vs SHE [137,138], corresponding to the standard transformed Gibbs free energy change at –15.1 kcal/mol (–63.1 kJ/mol, obtained by multiplying the Faraday constant) for the 1 electron redox, standard transformed Gibbs free energy change for the total reaction of 1/2 N2 (g) + 4 SO2•– + 4 H+ + 8 ATP/H2O → NH3 (aq) + 1/2 H2 (g) + 4 SO2 (aq) + 8 ADP/Pi can be calculated at ΔG'r°(NH3) = –90 (= 19.82 + 0.5 × 19.49 + 4 × –15.1 + 8 × –7.36) kcal/mol with the ΔΔG'f°(NH3) (= ΔG'f°(NH3) – ΔG'r°(NH3)) value at 110 (= 19.82 – (–90)) kcal/mol. In cases that reduction is carried out by ferredoxin of Clostridium pasteurianum (–0.397 V vs SHE, corresponding to the standard transformed Gibbs free energy change at –9.16 kcal/mol) [138,148] or Azotobacter vinelandii (–0.634 V vs SHE, corresponding to the standard transformed Gibbs free energy change at –14.6 kcal/mol) [149], ΔG'r°(NH3) value is calculated at –66 or –88 kcal/mol, respectively, with the ΔΔG'f°(NH3) value at 86 or 108 kcal/mol, respectively. Alberty, 2003 Iotti, 2017, Chemical and biochemical thermodynamics: is it time for a reunification?, Biophys. Chem., 221, 49, 10.1016/j.bpc.2016.10.004 Stombaugh, 1976, Oxidation–reduction properties of several low potential iron–sulfur proteins and of methylviologen, Biochemistry, 15, 2633, 10.1021/bi00657a024 Iismaa, 1991, Site-directed mutagenesis of Azotobacter vinelandii ferredoxin I: change in [4Fe-4S] cluster reduction potential and reactivity, J. Biol. Chem., 32, 21563, 10.1016/S0021-9258(18)54675-5 Warren, 2010, Thermochemistry of proton-coupled electron transfer reagents and its implications, Chem. Rev., 110, 6961, 10.1021/cr100085k M.W. Chase Jr., NIST-JANAF thermochemical tables, fourth edition, J. Phys. Chem. Ref. Data, Monogr. (9) (1998) 1–1951, https://doi.org/10.18434/t42s31. Dunn, 2020, Oxidation of ammonia with molecular complexes, J. Am. Chem. Soc., 142, 17845, 10.1021/jacs.0c08269 Qing, 2020, Recent advances and challenges of electrocatalytic N2 reduction to ammonia, Chem. Rev., 120, 5437, 10.1021/acs.chemrev.9b00659 Pickett, 1985, Electrosynthesis of ammonia, Nature, 317, 652, 10.1038/317652a0 Pickett, 1986, Electron-transfer reactions in nitrogen fixation. Part 2. The electrosynthesis of ammonia: identification and estimation of products, J. Chem. Soc., Dalton Trans., 15, 1435 Arashiba, 2020, Electrochemical reduction of samarium triiodide into samarium diiodide, Chem. Lett., 49, 1171, 10.1246/cl.200429 J. Junge, S. Froitzheim, T.A. Engesser, J. Krahmer, C. Näther, N. Le Poul, F. Tuczek, Tungsten and molybdenum dinitrogen complexes supported by a pentadentate tetrapodal phosphine ligand: comparative spectroscopic, electrochemical and reactivity studies, Dalton Trans. 51 (2022) 6166–6176, https://doi.org/10.1039/d1dt04212b. E. del Horno, J. Jover, M. Mena, A. Pérez-Redondo, C. Yélamos, Dinitrogen binding at a trititanium chloride complex and its conversion to ammonia under ambient conditions. Angew. Chem., Int. Ed. 61, e202204544, Angew. Chem. 134, e202204544, https://doi.org/10.1002/anie.202204544. Ashida, 2022, Catalytic production of ammonia from dinitrogen employing molybdenum complexes bearing N-heterocyclic carbene-based PCP-type pincer ligands, ChemRxiv Ashida, 2022, Catalytic nitrogen fixation using visible light energy, ChemRxiv F. Meng, S. Kuriyama, A. Egi, H. Tanaka, K. Yoshizawa, Y. Nishibayashi, Preparation and reactivity of rhenium–nitride complexes bearing PNP-type pincer ligands toward nitrogen fixation, Organometallics in press, https://doi.org/10.1021/acs.organomet.2c00312. Dong, 2020, The effect of substituents on the formation of silyl [PSiP] pincer cobalt(I) complexes and catalytic application in both nitrogen silylation and alkene hydrosilylation, Inorg. Chem., 59, 16489, 10.1021/acs.inorgchem.0c02332 M. Li, S.K. Gupta, S. Dechert, S. Demeshko, F. Meyer, Merging pincer motifs and potential metal–metal cooperativity in cobalt dinitrogen chemistry: efficient catalytic silylation of N2 to N(SiMe3)3, Angew. Chem., Int. Ed. 60 (2021) 14480–14487, Angew. Chem. 133 (2021) 14601–14608, https://doi.org/10.1002/anie.202101387. Chang, 2021, Synthesis of silyl iron dinitrogen complexes for activation of dihydrogen and catalytic silylation of dinitrogen, Dalton Trans., 50, 17594, 10.1039/D1DT02832D Liang, 2021, [2Fe–2S] cluster supported by redox-active o-phenylenediamide ligands and its application toward dinitrogen reduction, Inorg. Chem., 60, 13811, 10.1021/acs.inorgchem.1c00683 Kuriyama, 2022, Synthesis and reactivity of cobalt–dinitrogen complexes bearing anionic PCP-type pincer ligand toward catalytic silylamine formation from dinitrogen, Inorg. Chem., 61, 5190, 10.1021/acs.inorgchem.2c00234 Kuriyama, 2022, Synthesis and reactivity of manganese complexes bearing anionic PNP- and PCP-type pincer ligands toward nitrogen fixation, Molecules, 27, 2373, 10.3390/molecules27072373 Ohki, 2022, Nitrogen reduction by the Fe sites of synthetic [Mo3S4Fe] cubes, Nature, 607, 86, 10.1038/s41586-022-04848-1 S. Bennaamane, M.F. Espada, A. Mulas, T. Personeni, N. Saffon-Merceron, M. Fustier-Boutignon, C. Bucher, N. Mézailles, Catalytic reduction of N2 to borylamine at a molybdenum complex, Angew. Chem., Int. Ed. 60 (2021) 20210–20214, Angew. Chem. 133 (2021) 20372–20376, https://doi.org/10.1002/anie.202106025. McWilliams, 2020, Coupling dinitrogen and hydrocarbons through aryl migration, Nature, 584, 221, 10.1038/s41586-020-2565-5 Schluschaß, 2021, Cyanate formation via photolytic splitting of dinitrogen, JACS Au, 1, 879, 10.1021/jacsau.1c00117 J. Song, Q. Liao, X. Hong, L. Jin, N. Mézailles, Conversion of dinitrogen into nitrile: cross-metathesis of N2-derived molybdenum nitride with alkynes, Angew. Chem., Int. Ed. 60 (2021) 12242–12247, Angew. Chem. 133 (2021) 12350–12355, http://dx.doi.org/10.1002/anie.202015183. H.K. Wagner, H. Wadepohl, J. Ballmann, Molybdenum-mediated N2-splitting and functionalization in the presence of a coordinated alkyne, Angew. Chem., Int. Ed. 60 (2021) 25804–25808, Angew. Chem. 133 (2021) 26008–26012, http://dx.doi.org/10.1002/anie.202111325. Itabashi, 2022, Hydroboration and hydrosilylation of a molybdenum−nitride complex bearing a PNP-type pincer ligand, Organometallics, 41, 366, 10.1021/acs.organomet.1c00597 Itabashi, 2022, Reactivity of molybdenum–nitride complex bearing pyridine-based PNP-type pincer ligand toward carbon-centered electrophiles, Dalton Trans., 51, 1946, 10.1039/D1DT03952K Zhang, 2022, N2 Cleavage on d4/d4 molybdenum centers and its further conversion into iminophosphorane under mild conditions, J. Am. Chem. Soc., 144, 2444, 10.1021/jacs.1c11134 Zhuo, 2022, Dinitrogen cleavage and functionalization with carbon dioxide in a dititanium dihydride framework, J. Am. Chem. Soc., 144, 6972, 10.1021/jacs.2c01851 Itabashi, 2022, Direct synthesis of cyanate anion from dinitrogen catalysed by molybdenum complexes bearing pincer-type ligand, ChemRxiv Guo, 2017, Catalyst: NH3 as an energy carrier, Chem, 3, 709, 10.1016/j.chempr.2017.10.004 Service, 2018, Liquid sunshine: ammonia made from sun, air, and water could turn Australia into a renewable energy superpower, Science, 361, 120, 10.1126/science.361.6398.120 Liu, 2019, Homogeneous catalysis for the nitrogen fuel cycle, Proc. Natl. Acad. Sci. U. S. A., 116, 2794, 10.1073/pnas.1822090116 Nakajima, 2019, Ruthenium-catalysed oxidative conversion of ammonia into dinitrogen, Nat. Chem., 11, 702, 10.1038/s41557-019-0293-y Toda, 2021, Manganese-catalyzed ammonia oxidation into dinitrogen under chemical or electrochemical conditions, ChemPlusChem, 86, 1511, 10.1002/cplu.202100349 Habibzadeh, 2019, Homogeneous electrocatalytic oxidation of ammonia to N2 under mild conditions, Proc. Natl. Acad. Sci. USA, 116, 2849, 10.1073/pnas.1813368116 P, Bhattacharya, Z.M. Heiden, G.M. Chambers, S.I. Johnson, R.M. Bullock, M.T. Mock, Catalytic ammonia oxidation to dinitrogen by hydrogen atom abstraction, Angew. Chem., Int. Ed. 58 (2019) 11618–11624, Angew. Chem. 131 (2019) 11744–11750, http://dx.doi.org/10.1002/anie.201903221. Zott, 2019, Electrocatalytic ammonia oxidation mediated by a polypyridyl iron catalyst, J. Am. Chem. Soc., 9, 10101 Boroujeni, 2019, Chemical and electrocatalytic ammonia oxidation by ferrocene, ChemRxiv Dunn, 2020, Diversion of catalytic C–N bond formation to catalytic oxidation of NH3 through modification of the hydrogen atom abstractor, J. Am. Chem. Soc., 142, 3361, 10.1021/jacs.9b13706 Zott, 2021, Enhanced ammonia oxidation catalysis by a low-spin iron complex featuring cis coordination sites, J. Am. Chem. Soc., 143, 7612, 10.1021/jacs.1c02232 Holub, 2021, Synthesis, structure, and ammonia oxidation catalytic activity of Ru-NH3 complexes containing multidentate polypyridyl ligands, Inorg. Chem., 60, 13929, 10.1021/acs.inorgchem.1c01528 Trenerry, 2021, Spontaneous N2 formation by a diruthenium complex enables electrocatalytic and aerobic oxidation of ammonia, Nat. Chem., 13, 1221, 10.1038/s41557-021-00797-w Li, 2022, A parent iron amido complex in catalysis of ammonia oxidation, J. Am. Chem. Soc., 144, 4375 Liu, 2022, Electrocatalytic, homogeneous ammonia oxidation in water to nitrate and nitrite with a copper complex, J. Am. Chem. Soc., 144, 8449, 10.1021/jacs.2c01788