Dinickel Active Sites Supported by Redox-Active Ligands.
26 Sep 2021-Accounts of Chemical Research (American Chemical Society (ACS))-Vol. 54, Iss: 19, pp 3710-3719
TL;DR: In this article, a series of dinickel complexes supported by naphthyridine-diimine (NDI) ligands are investigated, and it is shown that 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.
Abstract: 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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TL;DR: A brief summary of research advances in this field is given, highlighting the development of bifunctional ligand-ligated Ni-Al bimetallic catalysis and their applications.
6 citations
TL;DR: In this article , a review of transition metal catalyzed nitrene coupling is presented, focusing on various Nitrene coupling mechanisms, and the substrate scope for each system, and particular attention is devoted to the iron-alkoxide catalytic systems investigated in the PI's laboratory.
Abstract: Various valuable properties of azoarenes ("azo dyes"), including their vivid colors and their facile cis-trans photoisomerization, lead to their wide use in the chemical industry. As a result, ∼700 000 metric tons of azo dyes are produced each year. Most currently utilized synthetic methods towards azoarenes involve harsh reaction conditions and/or toxic reagents in stoichiometric amounts, which may affect selectivity and produce significant amounts of waste. An efficient alternative method towards this functional group includes transition metal catalyzed nitrene coupling. This method is generally more sustainable compared with most stoichiometric methods as it uses only catalytic amounts of co-reactants (metal catalysts), requires easily synthesizable organoazide precursors, and forms only dinitrogen as a by-product of catalysis. During the last decade, several catalytic systems were reported, and their reactivity was investigated. This perspective article will review these systems, focusing on various nitrene coupling mechanisms, and the substrate scope for each system. Particular attention will be devoted to the iron-alkoxide catalytic systems investigated in the PI's laboratory. The design and structural features of several generations of iron bis(alkoxide) complexes will be discussed, followed by the structure-activity studies of these catalysts in nitrene homo- and heterocoupling.
6 citations
TL;DR: In this paper , a review summarizes and analyses information from the literature, published mainly from 2000 to the present, on the methods of preparation, the molecular and electronic structure of mixed-ligand coordination compounds based on redoxactive ligands of the o-benzoquinone type and ferrocenes, ferrocene-containing ligands, the features of their redox properties, and some chemical behaviour.
Abstract: A combination of different types of redox-active systems in one molecule makes it possible to create coordination compounds with extended redox abilities, combining molecular and electronic structures determined by the features of intra- and intermolecular interactions between such redox-active centres. This review summarizes and analyses information from the literature, published mainly from 2000 to the present, on the methods of preparation, the molecular and electronic structure of mixed-ligand coordination compounds based on redox-active ligands of the o-benzoquinone type and ferrocenes, ferrocene-containing ligands, the features of their redox properties, and some chemical behaviour.
3 citations
TL;DR: In this paper , a dinickel catalyst can induce cis/trans isomerization in azoarenes through a N═N bond rotation mechanism, and the scope of the catalytic isomerisation includes high-performance acyclic, cyclic, and polymeric annealing switches.
Abstract: Azoarenes function as molecular switches that can be triggered by external stimuli, such as heat, light, and electrochemical potential. Here, we show that a dinickel catalyst can induce cis/trans isomerization in azoarenes through a N═N bond rotation mechanism. Catalytic intermediates containing azoarenes bound in both the cis and trans forms are characterized. Solid-state structures reveal the importance of π-back-bonding interactions from the dinickel active site in lowering the N═N bond order and accelerating bond rotation. The scope of the catalytic isomerization includes high-performance acyclic, cyclic, and polymeric azoarene switches.
1 citations
References
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TL;DR: The phytochemical remains of the seven-membered ring formation are still under investigation, but it is clear that the polymethine content of the ring is lower than previously thought, suggesting that it is more likely to be a mixture of 22π and 32σ.
Abstract: 5.7. [32π + 32σ] Cycloadditions 74 5.8. [44π + 22π] Cycloadditions 75 6. Seven-Membered Ring Formation 78 6.1. [44π + 32σ] Cycloadditions 78 6.2. [52π+2σ + 22π] Cycloadditions 79 7. Eight-Membered Ring Formation 79 7.1. [22π + 22π + 22π + 22π] Cycloadditions 80 7.2. [44π + 22π + 22π] Cycloadditions 80 7.3. [44π + 44π] Cycloadditions 81 7.4. [66π + 22π] Cycloadditions 83 8. Ten-Membered Ring Formation 85 9. Conclusion and Remarks 87
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TL;DR: This critical review summarizes key properties of azobenzene that enable its use as a photoswitch in biological systems and describes strategies for using azobensene photoswitches to drive functional changes in peptides, proteins, nucleic acids, lipids, and carbohydrates.
Abstract: The photoisomerization of azobenzene has been known for almost 75 years but only recently has this process been widely applied to biological systems. The central challenge of how to productively couple the isomerization process to a large functional change in a biomolecule has been met in a number of instances and it appears that effective photocontrol of a large variety of biomolecules may be possible. This critical review summarizes key properties of azobenzene that enable its use as a photoswitch in biological systems and describes strategies for using azobenzene photoswitches to drive functional changes in peptides, proteins, nucleic acids, lipids, and carbohydrates (192 references).
1,371 citations
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TL;DR: Drawing inspiration from natural catalysts, chemists have developed a variety of synthetic small-molecule catalysts that can achieve levels of selectivity approaching, and in some cases matching, those observed in enzymatic reactions.
Abstract: One of the most active current areas of chemical research is centered on how to synthesize handed (chiral) compounds in a selective manner, rather than as mixtures of mirror-image forms (enantiomers) with different three-dimensional structures (stereochemistries). Nature points the way in this endeavor: different enantiomers of a given biomolecule can exhibit dramatically different biological activities, and enzymes have therefore evolved to catalyze reactions with exquisite selectivity for the formation of one enantiomeric form over the other. Drawing inspiration from these natural catalysts, chemists have developed a variety of synthetic small-molecule catalysts that can achieve levels of selectivity approaching, and in some cases matching, those observed in enzymatic reactions.
1,130 citations
TL;DR: Schore as mentioned in this paper was a member of the faculty at the University of California, Los Angeles and was named recipient of the Magnar Ronning Award for Excellence in Teaching in 1979, and Camille and Henry Dreyfus Teacher-Scholar fw 1981-1986.
Abstract: 0009-2685/88/078&1081$06.50/0 Neil E. Schore was born in Newark. NJ. in 1948. He attended schools In Bronx, NY. and Ridgefield. NJ. and received his B.A. degree in chemistry from the University of Pennsylvania in 1969. He returned to New York to do graduate work at Columbia UnivwsRy under the direction of Nicholas J. TWO. completing the Ph.0. in 1973. Cai Tech was the next stop, fw 2'1, years as a National InsfRutes of Health Postdoctoral Fellow in the labwatwks of Robert G. Bergman, where he discovered the existence of wganometailic chemistry. Since 1976 he has been a member of the faculty at the University of California. Davis. He was named recipient of the Magnar Ronning Award for Excellence in Teaching in 1979, and Camille and Henry Dreyfus Teacher-Scholar fw 1981-1986. HIS research interests involve mechanistic and synthetic lransitionmetal chemistry. including study 01 early transaion-metal systems with remote ligand sites. construction and chemistry of biand polymetallic complexes. and applications 01 ths chemisby of these systems to natural pcducts synthesis. A special area of emphasis has been the study of the Pauson-Khand cyciopentenone synthesis
815 citations