Tuning metal–metal interactions for cooperative small molecule activation

Wang, Qiuran; Brooks, Sam H.; Liu, Tianchang; Tomson, Neil C.

doi:10.1039/d0cc07721f

Cited by 70 publications

(65 citation statements)

References 150 publications

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“…Remarkable advances in homogeneous catalysis have been achieved with systems comprising late transition metals and PDI ligands. − To date, several multinuclear transition-metal complexes supported by macrocyclic ligands bearing two or more PDI moieties have been developed, and they exhibited interesting reactivity differences in catalytic ethylene polymerization compared to analogous mononuclear complexes. − However, current uses of bis-PDI-based dinuclear complexes in the catalytic methodology are still in their infancy and further research efforts are warranted. In 2017, Tomson and co-workers reported an attractive work describing the dicobalt(II) complexes bound by pyridyl diimine-containing macrocyclic ligands with flexible links. − Additionally, each cobalt atom was bonded by a PMe 3 ligand, which can further react with the dicobalt-bridging nitrides. Our approach to the development of the dinuclear cobalt molecular catalyst was inspired by the unique catalytic performance of Co 2 (CO) 8 and pioneering work from the Tomson group, and the phosphine ligand-free bis-PDI dicobalt complex was developed since appropriate empty coordination sites are required for catalysis.…”

Section: Resultsmentioning

confidence: 99%

“…Unfortunately, extensive efforts to isolate II and get its crystal structure failed. Computational results showed that a folded PDI ligand conformation of intermediate II ( S = 1, Scheme ) is 1.3 kcal/mol more stable than the parallel ligand conformation (Table S5 in the Supporting Information). − And the Co α –Co β distance located at 2.47 Å, implying a plausible metal–metal single bond character with 0.52 Mayer bond order (MBO). The Δ value is a single parameter combined by the values of C im –N im ,C im –C py and C py -N py distances, which is a powerful structural parameter for the determination of the oxidation level of the PDI ligand .…”

Section: Resultsmentioning

confidence: 99%

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Dinuclear Cobalt Complex-Catalyzed Stereodivergent Semireduction of Alkynes: Switchable Selectivities Controlled by H₂O

Chen

Zhu

et al. 2021

ACS Catal.

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Catalytic semireduction of internal alkynes to alkenes is very important for organic synthesis. Although great success has been achieved in this area, switchable Z/E stereoselectivity based on a single catalyst for the semireduction of internal alkynes is a longstanding challenge due to the multi-chemo- and stereoselectivity, especially based on less-expensive earth-abundant metals. Herein, we describe a switchable semireduction of alkynes to (Z)- or (E)-alkenes catalyzed by a dinuclear cobalt complex supported by a macrocyclic bis pyridyl diimine (PDI) ligand. It was found that cis-reduction of the alkyne occurs first and the Z–E alkene stereoisomerization process is formally controlled by the amount of H2O, since the concentration of H2O may influence the catalytic activity of the catalyst for isomerization. Therefore, this protocol provides a facile way to switch to either the (Z)- or (E)-olefin isomer in a single transformation by adjusting the amount of water.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Dinuclear Cobalt Complex-Catalyzed Stereodivergent Semireduction of Alkynes: Switchable Selectivities Controlled by H₂O

Chen

Zhu

et al. 2021

ACS Catal.

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“…However, many other redox-active motifs are currently known. Recently, Tomson described a series of macrocyclic complexes that feature two (PDI)M units connected by alkyl tethers . Given our observation that (NDI)Ni 2 -catalyzed processes can require the reversible formation and cleavage of Ni–Ni bonds, it is interesting to consider the implications of such ligands with added conformational flexibility.…”

Section: Discussionmentioning

confidence: 99%

Dinickel Active Sites Supported by Redox-Active Ligands

Uyeda

Farley

2021

Acc. Chem. Res.

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Conspectus Redox reactions that take place in enzymes and on the surfaces of heterogeneous catalysts often require active sites that contain multiple metals. By contrast, there are very few homogeneous catalysts with multinuclear active sites, and the field of organometallic chemistry continues to be dominated by the study of single metal systems. Multinuclear catalysts have the potential to display unique properties owing to their ability to cooperatively engage substrates. Furthermore, direct metal-to-metal covalent bonding can give rise to new electronic configurations that dramatically impact substrate binding and reactivity. In order to effectively capitalize on these features, it is necessary to consider strategies to avoid the dissociation of fragile metal–metal bonds in the course of a catalytic cycle. This Account describes one approach to accomplishing this goal using binucleating redox-active ligands. In 2006, Chirik showed that pyridine–diimines (PDI) have sufficiently low-lying π* levels that they can be redox-noninnocent in low-valent iron complexes. Extending this concept, we investigated a series of dinickel complexes supported by naphthyridine–diimine (NDI) ligands. These complexes can promote a broad range of two-electron redox processes in which the NDI ligand manages electron equivalents while the metals remain in a Ni(I)–Ni(I) state. Using (NDI)Ni2 catalysts, we have uncovered cases where having two metals in the active site addresses a problem in catalysis that had not been adequately solved using single-metal systems. For example, mononickel complexes are capable of stoichiometrically dimerizing aryl azides to form azoarenes but do not turn over due to strong product inhibition. By contrast, dinickel complexes are effective catalysts for this reaction and avoid this thermodynamic sink by binding to azoarenes in their higher-energy cis form. Dinickel complexes can also activate strong bonds through the cooperative action of both metals. Norbornadiene has a ring-strain energy that is similar to that of cyclopropane but is not prone to undergoing C–C oxidative addition with monometallic complexes. Using an (NDI)Ni2 complex, norbornadiene undergoes rapid ring opening by the oxidative addition of the vinyl and bridgehead carbons. An inspection of the resulting metallacycle reveals that it is stabilized through a network of secondary Ni−π interactions. This reactivity enabled the development of a catalytic carbonylative rearrangement to form fused bicyclic dienones. These vignettes and others described in this Account highlight some of the implications of metal–metal bonding in promoting a challenging step in a catalytic cycle or adjusting the thermodynamic landscape of key intermediates. Given that our studies have focused nearly exclusively on the (NDI)Ni2 system, we anticipate that many more such cases are left to be discovered as other transition-metal combinations and ligand classes are explored.

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“…There is no universal classification scheme. Sometimes systems are considered based on the degree of metal-metal interaction, 46,48 the ligand scaffold, 46,48 the polarity or Lewis acidity/basicity of the metals, 16 or the mode of substrate activation. 49 Instead, we have presented examples herein by reaction type and substrate.…”

Section: Metal-metal Cooperativitymentioning

confidence: 99%

Cooperative approaches in catalytic hydrogenation and dehydrogenation

Stevens

Colebatch

2022

Chem. Soc. Rev.

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Tuning metal–metal interactions for cooperative small molecule activation

Abstract: This Feature Article describes recent advances in the design of multinucleating ligands that support small molecule activation chemistry.

Cited by 70 publications

References 150 publications

Dinuclear Cobalt Complex-Catalyzed Stereodivergent Semireduction of Alkynes: Switchable Selectivities Controlled by H₂O

Dinuclear Cobalt Complex-Catalyzed Stereodivergent Semireduction of Alkynes: Switchable Selectivities Controlled by H₂O

Dinickel Active Sites Supported by Redox-Active Ligands

Cooperative approaches in catalytic hydrogenation and dehydrogenation

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Tuning metal–metal interactions for cooperative small molecule activation

Abstract: This Feature Article describes recent advances in the design of multinucleating ligands that support small molecule activation chemistry.

Cited by 70 publications

References 150 publications

Dinuclear Cobalt Complex-Catalyzed Stereodivergent Semireduction of Alkynes: Switchable Selectivities Controlled by H2O

Dinuclear Cobalt Complex-Catalyzed Stereodivergent Semireduction of Alkynes: Switchable Selectivities Controlled by H2O

Dinickel Active Sites Supported by Redox-Active Ligands

Cooperative approaches in catalytic hydrogenation and dehydrogenation

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Product

Resources

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Dinuclear Cobalt Complex-Catalyzed Stereodivergent Semireduction of Alkynes: Switchable Selectivities Controlled by H₂O

Dinuclear Cobalt Complex-Catalyzed Stereodivergent Semireduction of Alkynes: Switchable Selectivities Controlled by H₂O