Coupling of terminal iridium nitrido complexes

Abbenseth, Josh; Finger, Markus; Würtele, Christian; Kasanmascheff, Müge; Schneider, Sven

doi:10.1039/c5qi00267b

Cited by 52 publications

(31 citation statements)

References 42 publications

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“…As in the previous computational model, 19 the transition state (TS) for splitting of 3 into nitrides exhibits a Re–N–N–Re in-plane zigzag structure 39 with an N–N distance (1.59 Å) that is considerable longer than the N–N single bond in hydrazine (1.45 Å). Upon approaching the TS, MO242 ( Figure 9 ), which is essentially Re–N–N–Re nonbonding, gains considerable σ Re–N and σ* N–N character and is gradually stabilized with respect to the π-MO manifold ( Figure S59 ).…”

Section: Resultsmentioning

confidence: 60%

Mechanism of Chemical and Electrochemical N₂ Splitting by a Rhenium Pincer Complex

et al. 2018

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A comprehensive mechanistic study of N2 activation and splitting into terminal nitride ligands upon reduction of the rhenium dichloride complex [ReCl2(PNP)] is presented (PNP– = N(CH2CH2PtBu2)2–). Low-temperature studies using chemical reductants enabled full characterization of the N2-bridged intermediate [{(PNP)ClRe}2(N2)] and kinetic analysis of the N–N bond scission process. Controlled potential electrolysis at room temperature also resulted in formation of the nitride product [Re(N)Cl(PNP)]. This first example of molecular electrochemical N2 splitting into nitride complexes enabled the use of cyclic voltammetry (CV) methods to establish the mechanism of reductive N2 activation to form the N2-bridged intermediate. CV data was acquired under Ar and N2, and with varying chloride concentration, rhenium concentration, and N2 pressure. A series of kinetic models was vetted against the CV data using digital simulations, leading to the assignment of an ECCEC mechanism (where “E” is an electrochemical step and “C” is a chemical step) for N2 activation that proceeds via initial reduction to ReII, N2 binding, chloride dissociation, and further reduction to ReI before formation of the N2-bridged, dinuclear intermediate by comproportionation with the ReIII precursor. Experimental kinetic data for all individual steps could be obtained. The mechanism is supported by density functional theory computations, which provide further insight into the electronic structure requirements for N2 splitting in the tetragonal frameworks enforced by rigid pincer ligands.

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Section: Resultsmentioning

confidence: 60%

Mechanism of Chemical and Electrochemical N₂ Splitting by a Rhenium Pincer Complex

et al. 2018

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“…The effect of charge on N 2 coupling was previously explored in Ir nitride complexes, but the charge differences were due to oxidation of the complex so that cationic effects could not be isolated from changes in electronic structure . In this ligand framework, we can modify the charge without changing the oxidation state of the metal or primary coordination sphere.…”

Section: Methodsmentioning

confidence: 99%

Cationic Charges Leading to an Inverse Free‐Energy Relationship for N−N Bond Formation by Mn^VI Nitrides

2018

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Mn N Schiff-base complexes incorporating a Na (1Na), K (1K), Ba (1Ba), or Sr (1Sr) ion in the ligand framework are reported. The Mn reduction potentials for 1Na, 1K, 1Ba, and 1Sr are 0.591, 0.616, 0.805, and 0.880 V vs. Fe(C H ) , respectively, exhibiting significant positive shifts compared to a MnN Schiff-base complex in the same primary coordination environment but with no associated alkali or alkaline earth metal ion (A, E =0.427 V vs. Fe(C H ) ). One-electron oxidation of the Mn N complexes results in bimolecular coupling to form N with rates (k ) at 20 °C of 2166, 684, 857, and 99.7, an 87 m s for A, 1Na, 1K, 1Ba, and 1Sr respectively, following an inverse linear free energy relationship. Thus, increasing charge through proximal cations results in Mn N complexes that are both more oxidizing and more stable to bimolecular coupling, a trend diametrically opposed to when complexes were modified by ligand substituents through inductive effects.

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“…[1] Iridium complexes are among the most active water oxidation and C À Ha ctivation catalysts,w here Ir V is ap roposed catalytic intermediate. [2] However,t here are few examples of wellcharacterized Ir V coordination complexes.Previous examples include moisture-sensitive homoleptic fluorides, [3] as well as organometallic compounds [4] with potentially non-innocent alkyl or hydride ligands.W erecently reported an Ir IV,V monom-oxo dimer coordinated by the pyalk ligand (pyalk = 2-(2pyridinyl)-isopropanolate) as the first example of an Ir IV,V complex. [5] We attributed the surprising stability of this species to the donor strength [6] and oxidation resistance of the ligand as well as delocalization of the Ir IV,V oxidation state.…”

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Synthesis and Characterization of Iridium(V) Coordination Complexes With an N,O‐Donor Organic Ligand

et al. 2017

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We have prepared and fully characterized two isomers of [Ir IV (dpyp) 2 ]( dpyp = meso-2,4-di(2-pyridinyl)-2,4pentanediolate). These complexes can cleanly oxidizet o [Ir V (dpyp) 2 ] + ,w hicht oo ur knowledge represent the first mononuclear coordination complexes of Ir V in an N,O-donor environment. One isomer has been fully characterized in the Ir V state,i ncluding by X-rayc rystallography,X PS,a nd DFT calculations,a ll of which confirm metal-centered oxidation. The unprecedented stability of these Ir V complexes is ascribed to the exceptional donor strength of the ligands,their resistance to oxidative degradation, and the presence of four highly donor alkoxide groups in aplane,which breaks the degeneracy of the d-orbitals and favors oxidation.

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Coupling of terminal iridium nitrido complexes

Abstract: The homo- and heterocoupling of molecular terminal iridium(iv) and iridium(v) nitrides is examined. The experimental coupling rates are discussed based on a computational analysis of the transition states.

Cited by 52 publications

References 42 publications

Mechanism of Chemical and Electrochemical N₂ Splitting by a Rhenium Pincer Complex

Mechanism of Chemical and Electrochemical N₂ Splitting by a Rhenium Pincer Complex

Cationic Charges Leading to an Inverse Free‐Energy Relationship for N−N Bond Formation by Mn^VI Nitrides

Synthesis and Characterization of Iridium(V) Coordination Complexes With an N,O‐Donor Organic Ligand

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Coupling of terminal iridium nitrido complexes

Abstract: The homo- and heterocoupling of molecular terminal iridium(iv) and iridium(v) nitrides is examined. The experimental coupling rates are discussed based on a computational analysis of the transition states.

Cited by 52 publications

References 42 publications

Mechanism of Chemical and Electrochemical N2 Splitting by a Rhenium Pincer Complex

Mechanism of Chemical and Electrochemical N2 Splitting by a Rhenium Pincer Complex

Cationic Charges Leading to an Inverse Free‐Energy Relationship for N−N Bond Formation by MnVI Nitrides

Synthesis and Characterization of Iridium(V) Coordination Complexes With an N,O‐Donor Organic Ligand

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Product

Resources

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Mechanism of Chemical and Electrochemical N₂ Splitting by a Rhenium Pincer Complex

Mechanism of Chemical and Electrochemical N₂ Splitting by a Rhenium Pincer Complex

Cationic Charges Leading to an Inverse Free‐Energy Relationship for N−N Bond Formation by Mn^VI Nitrides