Synthesis, Structure, and Ammonia Oxidation Catalytic Activity of Ru-NH<sub>3</sub> Complexes Containing Multidentate Polypyridyl Ligands

Holub, Jan; Vereshchuk, Nataliia; Sánchez-Baygual, Francisco-Javier; Gil‐Sepulcre, Marcos; Benet‐Buchholz, Jordi; Llobet, Antoni

doi:10.1021/acs.inorgchem.1c01528

Cited by 31 publications

(32 citation statements)

References 61 publications

(129 reference statements)

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“…Not only can homogenous electrocatalysts circumvent these issues but earth-abundant metals also have obvious cost advantages. Numerous molecular electrocatalysts for AO have emerged recently. − Most of these catalysts perform a three-electron AO to N 2 but are also potentially competent for water oxidation (WO), pointing to possible selectivity problems with aqueous ammonia as a substrate.…”

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confidence: 99%

Electrocatalytic, Homogeneous Ammonia Oxidation in Water to Nitrate and Nitrite with a Copper Complex

et al. 2022

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Electrocatalytic ammonia oxidation at room temperature and pressure allows energy-economical and environmentally friendly production of nitrites and nitrates. Few molecular catalysts, however, have been developed for this six- or eight-electron oxidation process. We now report [Cu(bipyalk)]+, a homogeneous electrocatalyst that realizes the title reaction in water at 94% Faradaic efficiency. The catalyst exhibits high selectivity against water oxidation in aqueous media, as [Cu(bipyalk)]+ is not competent for water oxidation.

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confidence: 99%

Electrocatalytic, Homogeneous Ammonia Oxidation in Water to Nitrate and Nitrite with a Copper Complex

et al. 2022

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“…Interest in molecular catalysts for oxidation of ammonia has burgeoned recently . The development of the first molecular catalyst (Figure A) for electrocatalytic oxidation of NH 3 reported in 2019 was followed by discovery of several new catalysts for chemical or electrochemical oxidation of NH 3 . − …”

Section: Introductionmentioning

confidence: 99%

“…For the key step forming the NN bond (Figure ), mechanisms involving nucleophilic attack of NH 3 on a bound M-NH x ( x = 0, 1, or 2) ligand ,− and homocoupling of two M-NH x ( x = 0, 1, or 2) species , have both been proposed. Bimetallic homocoupling has been proposed to proceed through metal nitrides or amido intermediates. , Complexes with two NH 3 ligands , in a cis-geometry offer the possibility of intramolecular formation of the NN bond.…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen Atom Abstraction from an Os^II(NH₃)₂ Complex Generates an Os^IV(NH₂)₂ Complex: Experimental and Computational Analysis of the N–H Bond Dissociation Free Energies and Reactivity

et al. 2022

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Double hydrogen atom abstraction from (TMP)Os II (NH 3 ) 2 (TMP = tetramesitylporphyrin) with phenoxyl or nitroxyl radicals leads to (TMP)-Os IV (NH 2 ) 2 . This unusual bis(amide) complex is diamagnetic and displays an N−H resonance at 12.0 ppm in its 1 H NMR spectrum. 1 H− 15 N correlation experiments identified a 15 N NMR spectroscopic resonance signal at −267 ppm. Experimental reactivity studies and density functional theory calculations support relatively weak N−H bonds of 73.3 kcal/mol for (TMP)Os II (NH 3 ) 2 and 74.2 kcal/mol for (TMP)Os III (NH 3 )(NH 2 ). Cyclic voltammetry experiments provide an estimate of the pK a of [(TMP)Os III (NH 3 ) 2 ] + . In the presence of Barton's base, a current enhancement is observed at the Os(III/II) couple, consistent with an ECE event. Spectroscopic experiments confirmed (TMP)Os IV (NH 2 ) 2 as the product of bulk electrolysis. Double hydrogen atom abstraction is influenced by π donation from the amides of (TMP)Os IV (NH 2 ) 2 into the d orbitals of the Os center, favoring the formation of (TMP)Os IV (NH 2 ) 2 over N−N coupling. This π donation leads to a Jahn−Teller distortion that splits the energy levels of the d xz and d yz orbitals of Os, results in a low-spin electron configuration, and leads to minimal aminyl character on the N atoms, rendering (TMP)Os IV (NH 2 ) 2 unreactive toward amide−amide coupling.

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“…13 Llobet and co-workers described the catalytic ammonia oxidation reaction activity using [Ru(tda-κ-N 3 O)(py)2], (tda 2− is 2,2:6,2-terpyridine-6,6-dicarboxylate; py is pyridine) as a catalyst precursor. 23 Recently, Berry and co-workers reported the metal-metal bonded mixed-valent Ru2(chp)4OTf (chp − = 6-chloro-2-hydroxypyridinate) that spontaneously forms nitrogen from ammonia without any applied potential. This dinuclear ruthenium species mediates electrocatalytic oxidation of ammonia with an onset potential at −255 mV, generating N2 and H2 via controlled potential electrolysis (CPE) at 0.0 V vs Fc 0/+ .…”

Section: Introductionmentioning

confidence: 99%

Electrocatalytic Ammonia Oxidation by a Low Coordinate Copper Complex

Ahmed

Boroujeni

Ghosh

et al. 2022

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Molecular catalysts for ammonia oxidation to dinitrogen represent enabling components to utilize ammonia as a fuel and/or source of hydrogen. Ammonia oxidation requires not only the breaking of multiple strong N-H bonds, but also controlled N-N bond formation. We report a novel β-diketiminato copper complex [iPr2NNF6]Cu-NH3 ([Cu(I)]-NH3 (2)) as a robust electrocatalyst for NH3 oxidation in acetonitrile under homogeneous conditions. Complex 2 operates at a moderate overpotential (700 mV) with a TOFmax = 940 h-1 as determined from CV data in 1.3 M NH3 MeCN solvent. Prolonged (>5 h) controlled potential electrolysis (CPE) reveals the stability and robustness of the catalyst under electrocatalytic conditions. Detailed mechanistic investigations indicate that electrochemical oxidation of [Cu(I)]-NH3 forms {[Cu(II)]-NH3}+ (4) which undergoes deprotonation by excess NH3 to form reactive copper(II)-amide [Cu(II)]-NH2 (6) unstable towards N-N bond formation to give the dinuclear hydrazine complex [Cu(I)]2(mu-N2H4). Electrochemical studies reveal that the bisammine complex [Cu(I)](NH3)2 (7) forms at high ammonia concentration as part of the {[Cu(II)](NH3)2}+/[Cu(I)](NH3)2 redox couple that is electrocatalytically inactive. DFT analysis reveals a much higher thermodynamic barrier for deprotonation of {[Cu(II)](NH3)2}+ (8) by NH3 to give the four-coordinate copper(II) amide [Cu(II)](NH2)(NH3) (9) (dG = 31.7 kcal/mol) as compared to deprotonation of the three coordinate {[Cu(II)]-NH3}+ by NH3 to provide the reactive three coordinate parent amide [Cu(II)]-NH2 (dG = 18.1 kcal/mol) susceptible to N-N coupling to form [Cu(I)]2(mu-N2H4) (dG = -11.8 kcal/mol).

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Synthesis, Structure, and Ammonia Oxidation Catalytic Activity of Ru-NH₃ Complexes Containing Multidentate Polypyridyl Ligands

Cited by 31 publications

References 61 publications

Electrocatalytic, Homogeneous Ammonia Oxidation in Water to Nitrate and Nitrite with a Copper Complex

Electrocatalytic, Homogeneous Ammonia Oxidation in Water to Nitrate and Nitrite with a Copper Complex

Hydrogen Atom Abstraction from an Os^II(NH₃)₂ Complex Generates an Os^IV(NH₂)₂ Complex: Experimental and Computational Analysis of the N–H Bond Dissociation Free Energies and Reactivity

Electrocatalytic Ammonia Oxidation by a Low Coordinate Copper Complex

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Synthesis, Structure, and Ammonia Oxidation Catalytic Activity of Ru-NH3 Complexes Containing Multidentate Polypyridyl Ligands

Cited by 31 publications

References 61 publications

Electrocatalytic, Homogeneous Ammonia Oxidation in Water to Nitrate and Nitrite with a Copper Complex

Electrocatalytic, Homogeneous Ammonia Oxidation in Water to Nitrate and Nitrite with a Copper Complex

Hydrogen Atom Abstraction from an OsII(NH3)2 Complex Generates an OsIV(NH2)2 Complex: Experimental and Computational Analysis of the N–H Bond Dissociation Free Energies and Reactivity

Electrocatalytic Ammonia Oxidation by a Low Coordinate Copper Complex

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Synthesis, Structure, and Ammonia Oxidation Catalytic Activity of Ru-NH₃ Complexes Containing Multidentate Polypyridyl Ligands

Hydrogen Atom Abstraction from an Os^II(NH₃)₂ Complex Generates an Os^IV(NH₂)₂ Complex: Experimental and Computational Analysis of the N–H Bond Dissociation Free Energies and Reactivity