“…Both principles have been separately reviewed. 26,27,30,32,39,46,51,[69][70][71][72][73][74]77,78,93,[142][143][144][145] However, the direct comparison offers additional insights for catalyst design. Scheme 2.…”
The use of 3d metals in de-/hydrogenation catalysis has emerged as a competitive field with respect to 'traditional' precious metal catalyzed transformations. The introduction of functional pincer ligands that can store protons and/or electrons as expressed by metal-ligand cooperativity and ligand redox-activity strongly stimulated this development as conceptual starting point for rational catalyst design. This reviews aims at providing a comprehensive picture of the utilization of functional pincer ligands in first-row transition metal hydrogenation and dehydrogenation catalysis and related synthetic concepts relying on these such as the hydrogen borrowing methodology. Particular emphasis is put on the implementation and relevance of cooperating and redox-active pincer ligands within the mechanistic scenarios.
“…Both principles have been separately reviewed. 26,27,30,32,39,46,51,[69][70][71][72][73][74]77,78,93,[142][143][144][145] However, the direct comparison offers additional insights for catalyst design. Scheme 2.…”
The use of 3d metals in de-/hydrogenation catalysis has emerged as a competitive field with respect to 'traditional' precious metal catalyzed transformations. The introduction of functional pincer ligands that can store protons and/or electrons as expressed by metal-ligand cooperativity and ligand redox-activity strongly stimulated this development as conceptual starting point for rational catalyst design. This reviews aims at providing a comprehensive picture of the utilization of functional pincer ligands in first-row transition metal hydrogenation and dehydrogenation catalysis and related synthetic concepts relying on these such as the hydrogen borrowing methodology. Particular emphasis is put on the implementation and relevance of cooperating and redox-active pincer ligands within the mechanistic scenarios.
“…In this perspective, the use of catalysts based on cheap and abundant base metals is especially beneficial for large-scale and industrial applications, where the paucity and cost of the noble metals like palladium, iridium, or ruthenium can be problematic. However, the base metals tend to react via a single electron transfer process and the corresponding two electron transfer processes are mostly enegetically uphill requiring high temperatures . In recent years, noteworthy progress has also been achieved with cheap copper , and nickel catalysts; however, these protocols almost always require high temperatures for the reaction to proceed.…”
Section: Introductionmentioning
confidence: 99%
“…The use of redox noninnocent ligands in combination with the base metals has emerged as an attractive alternative. , The ability of redox noninnocent ligands to store and release electrons when required allows multielectron transformations (mostly preferred for noble metals like palladium) with inexpensive 3d-base metals. In recent times, using the redox noninnocent properties of imine, diamine, and aminophenol based scaffolds, various new stoichiometric and catalytic reactions were developed where these organic scaffolds were found to participate actively during electron transfer processes involved during catalytic turnover .…”
A simple
and efficient approach of C–S cross-coupling of
a wide variety of (hetero)aryl thiols and (hetero)aryl halides under
mild conditions, mostly at room temperature, catalyzed by well-defined
singlet diradical Ni(II) catalysts bearing redox noninnocent ligands
is reported. Taking advantage of ligand centered redox events, the
high-energetic Ni(0)/Ni(II) or Ni(I)/Ni(III) redox steps were avoided
in the catalytic cycle. The cooperative participation of both nickel
and the coordinated ligands during oxidative addition/reductive elimination
steps allowed us to perform the catalytic reactions under mild conditions.
“…A key question regarding the [(phen)M] +• metal complexes is whether they are in the +1 oxidation or +2 oxidation state (i.e. where the phen ligand is a redox non-innocent ligand [66]). An examination of the DFT calculated spin density at the metal centers in the [(phen)M] +• metal complexes reveals (Table S1) that they range from 94.7% for M = Ni to 77.8% for M = Pt.…”
Section: Bond Homolysis Vs Carbene Formationmentioning
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