Localized Mixed‐Valence and Redox Activity within a Triazole‐Bridged Dinucleating Ligand upon Coordination to Palladium

Broere, Daniël L. J.; Plessius, Raoul; Tory, Joanne; Demeshko, Serhiy; Bruin, Bas de; Siegler, Maxime A.; Hartl, František; Vlugt, Jarl Ivar van der

doi:10.1002/chem.201601900

Cited by 27 publications

(12 citation statements)

References 103 publications

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“…Similar to the structures of related nickel complexes, the phosphine group is coordinated trans relative to the anionic carboxamidate moiety. The β-nitrogen atom of the triazole ring is sterically unhindered and should be capable of binding external metal ions. − We did not observe the formation of any 1,3- N , O -carboxamidate or 1,4- N , O -triazolecarboxamidate coordination isomers (Chart S1).…”

Section: Resultsmentioning

confidence: 89%

Triazolecarboxamidate Donors as Supporting Ligands for Nickel Olefin Polymerization Catalysts

Xiao

2018

Organometallics

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To increase the structural diversity of dinucleating platforms that are used in the construction of olefin polymerization catalysts, we are exploring new ligand designs that feature non-alkoxide/phenoxide bridging groups. In the current study, we demonstrate that 1,2,3-triazole-4-carboxamidate donors are excellent N,N-chelators for nickel and can readily bind secondary metal ions. We found that sterically bulky nickel triazolecarboxamidate complexes are active as ethylene homopolymerization catalysts and can afford low molecular weight polyethylene with about 80−130 branches per 1000 carbon atoms. The addition of zinc salts to our nickel complexes led to catalyst inhibition in some cases, which we have attributed to the formation of catalytically inactive mixed-metal species. To circumvent this problem, we anticipate that further elaboration of the triazolecarboxamidate ligand could provide discrete heterobimetallic complexes that will be useful as single-site catalysts with unique reactivity patterns.

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Section: Resultsmentioning

confidence: 89%

Triazolecarboxamidate Donors as Supporting Ligands for Nickel Olefin Polymerization Catalysts

Xiao

2018

Organometallics

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“…Diradical metal complexes featuring two ligand-based unpaired spins coordinated to diamagnetic metal centers (e.g., d 8 or d 10 ions) present a singlet or triplet ground state depending on the nature and relative orientation of the ligands. − Reports on diradicals in bridged binuclear complexes featuring one redox-active ligand per metal center are rather scarce, , but they point at an additional pathway for tuning spin exchange interactions between redox-active centers through modification of the bridging ligand(s). In this context, we sought to investigate the ability of the dipyrrindione framework to host unpaired spins in a bridged binuclear system.…”

Section: Introductionmentioning

confidence: 99%

Ligand-Centered Triplet Diradical Supported by a Binuclear Palladium(II) Dipyrrindione

et al. 2021

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Oligopyrroles form a versatile class of redox-active ligands and electron reservoirs. Although the stabilization of radicals within oligopyrrolic π systems is more common for macrocyclic ligands, bidentate dipyrrindiones are emerging as compact platforms for one-electron redox chemistry in transition-metal complexes. We report the synthesis of a bis(aqua) palladium(II) dipyrrindione complex and its deprotonation-driven dimerization to form a hydroxo-bridged binuclear complex in the presence of water or triethylamine. Electrochemical, spectroelectrochemical, and computational analyses of the binuclear complex indicate the accessibility of two quasi-reversible ligand-centered reduction processes. The product of a two-electron chemical reduction by cobaltocene was isolated and characterized. In the solid state, this cobaltocenium salt features a folded dianionic complex that maintains the hydroxo bridges between the divalent palladium centers. X-band and Q-band EPR spectroscopic experiments and DFT computational analysis allow assignment of the dianionic species as a diradical with spin density almost entirely located on the two dipyrrindione ligands. As established from the EPR temperature dependence, the associated exchange coupling is weak and antiferromagnetic ( J ≈ −2.5 K), which results in a predominantly triplet state at the temperatures at which the measurements have been performed.

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“…Reports documenting diradicals in bridged dinuclear complexes featuring one redox-active ligand per metal center are rather scarce, but they point at an additional pathway for tuning spin exchange interac-tions between redox-active centers through modification of the bridged ligand. 67,68 In this context, we sought to investigate the ability of the dipyrrindione framework to host unpaired spins in a bridged dinuclear system. In our previous investigations of the palladium(II) dipyrrindione complexes featuring primary amine ligands (e.g., [Pd(en)(pdp)] + , Chart 2d), 52 we found that the intramolecular hydrogen bonds are important for complex stability.…”

Section: Chart 2 Tetraethyl Propentdyopent-methanol Adduct (A) and Reported Complexes (B-d)mentioning

confidence: 99%

Stabilization of a Triplet Diradical on a Binuclear palladium(II) Dipyrrindione

Cj¹,

Av²,

Conradie³

et al. 2021

Preprint

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Porphyrins and other macrocyclic oligopyrroles form a versatile class of redox-active ligands and electron reservoirs. The stabilization of unpaired electrons within oligopyrrolic π systems adds to the available reactivity pathways and spin states of metal complexes for applications in catalysis and functional materials. In this context, bidentate dipyrrindiones are emerging as compact platforms for one-electron redox chemistry in transition metal complexes. We report the synthesis of a bis(aqua) palladium(II) dipyrrindione complex and its deprotonation-driven dimerization to form a hydroxo-bridged dinuclear complex. Electrochemical, spectroelectrochemical, and computational analyses indicate the accessibility of two reduction processes on the dipyrrindione frameworks of the dinuclear complex. The product of a two-electron reduction by cobaltocene was isolated and characterized. In the solid state, this cobaltoceni- um salt features a folded dianionic complex maintaining the hydroxo bridges between the divalent palladium centers. X- band and Q-band EPR spectroscopic experiments and DFT computational analysis allow assignment of the dianionic species as a triplet diradical supported by the dipyrrindione ligands. These dipyrroles, which are also known as propentdyopents and were initially isolated as urinary pigments and heme metabolites, extend the rich chemistry of bidentate dipyrrin ligands to include the stabilization of ligand-centered radicals.

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Localized Mixed‐Valence and Redox Activity within a Triazole‐Bridged Dinucleating Ligand upon Coordination to Palladium

Cited by 27 publications

References 103 publications

Triazolecarboxamidate Donors as Supporting Ligands for Nickel Olefin Polymerization Catalysts

Triazolecarboxamidate Donors as Supporting Ligands for Nickel Olefin Polymerization Catalysts

Ligand-Centered Triplet Diradical Supported by a Binuclear Palladium(II) Dipyrrindione

Stabilization of a Triplet Diradical on a Binuclear palladium(II) Dipyrrindione

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