New Chemistry with Anionic NNN Pincer Ligands

Melen, Rebecca L.; Gade, Lutz H.

doi:10.1007/3418_2015_114

Cited by 15 publications

(4 citation statements)

References 124 publications

(135 reference statements)

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“…Furthermore, various other reactions can also be catalyzed with the in situ formed bis(oxazolinyl)carbazolide chromium complex, including among others the selective functionalization of halide-substituted olefins with aldehydes or ketones, respectively, yielding the corresponding secondary − or tertiary alcohols, with high enantioselectivities. Access to targeted compounds with excellent selectivity renders this chromium-catalyzed protocol with high relevance, justifying the segments in various reviews regarding the use of the bis(oxazolinyl)carbazole ligand in the Nozaki-Hiyama reaction. ,,,,,, Hence, the topic will only be highlighted in this communication with the inclusion of selected examples illustrating the synthetic potential of the catalytic reaction when catalyzed with the in situ formed bis(oxazolinyl)carbazolide chromium complex.…”

Section: Wingtip Effectsmentioning

confidence: 99%

“…Access to targeted compounds with excellent selectivity renders this chromium-catalyzed protocol with high relevance, justifying the segments in various reviews regarding the use of the bis(oxazolinyl)carbazole ligand in the Nozaki-Hiyama reaction. 99,100,305,307,308,319,320 Hence, the topic will only be highlighted in this communication with the inclusion of selected examples illustrating the synthetic potential of the catalytic reaction when catalyzed with the in situ formed bis(oxazolinyl)carbazolide chromium complex. In a continuation of the work by Furstner et al, 321,322 Nakada and co-workers sought to decrease the stoichiometric use of chromium in the Nozaki-Hiyama C−C bond-forming reaction to catalytic amounts.…”

Section: Introducing Chiral Peripheries At the Wingtip Positionsmentioning

confidence: 99%

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LNL-Carbazole Pincer Ligand: More than the Sum of Its Parts

Kleinhans,

Karhu,

Boddaert

et al. 2023

Chem. Rev.

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The utility of carbazole in photo-, electro-, and medicinal applications has ensured its widespread use also as the backbone in tridentate pincer ligands. In this review, the aim is to identify and illustrate the key features of the LNL-carbazolide binding to transition metal centers (with L = flanking donor moieties, e.g., C, N, P, and O-groups) in a systematic bottom-up progression to illustrate the marked benefits attainable from (i) the rigid aromatic carbazole scaffold (modulable in both the 1,8-and 3,6-positions), (ii) the significant electronic effect of central carbazole-amido binding to a metal, and the tunable sterics and electronics of both the (iii) flanking donor L-moieties and (iv) the wingtip R-groups on the L-donors, with their corresponding influence on metal coordination geometry, d-electron configuration, and resultant reactivity. Systematic implementation of the ligand design strategies not in isolation, but in a combinatorial approach, is showcased to demonstrate the potential for functional molecules that are not only modulable but also adaptable for wide-ranging applications (e.g., stereoselective (photo)catalysis, challenging small molecule activation, SET and redox applications, and even applications in chemotherapeutics) as an indication of future research efforts anticipated to stem from this versatile pincer assembly, not only for the transition metals but also for s-, p-, and f-block elements.

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Section: Wingtip Effectsmentioning

confidence: 99%

Section: Introducing Chiral Peripheries At the Wingtip Positionsmentioning

confidence: 99%

LNL-Carbazole Pincer Ligand: More than the Sum of Its Parts

Kleinhans,

Karhu,

Boddaert

et al. 2023

Chem. Rev.

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“…■ T-SHAPED NICKEL COMPLEXES STABILIZED BY NNN PINCER LIGANDS Apart from the PNP ligands discussed above, pincer ligands with three nitrogen-based donors (i.e., NNN pincer ligands) have been widely used in coordination chemistry and catalysis. 50 The use of chiral oxazoline units at the "wingtip" position of a pincer ligand has proven especially successful in asymmetric catalysis. 51 We have recently shown that the nickel(II) chlorido complex 15 bearing a pmbox ligand can isomerize to the iso-pmbox complex 16, which is then reacted with lithium triethylborohydride to give the corresponding nickel(II) hydride 17.…”

Section: ■ Monovalent T-shaped Complexes Stabilized By Amidophosphine...mentioning

confidence: 99%

“…Apart from the PNP ligands discussed above, pincer ligands with three nitrogen-based donors (i.e., NNN pincer ligands) have been widely used in coordination chemistry and catalysis . The use of chiral oxazoline units at the “wingtip” position of a pincer ligand has proven especially successful in asymmetric catalysis …”

Section: T-shaped Nickel Complexes Stabilized By Nnn Pincer Ligandsmentioning

confidence: 99%

3d Metal Complexes in T-shaped Geometry as a Gateway to Metalloradical Reactivity

et al. 2022

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Metrics & MoreArticle Recommendations CONSPECTUS: Low-valent, low-coordinate 3d metal complexes represent a class of extraordinarily reactive compounds that can act as reagents and catalysts for challenging bond-activation reactions.The pursuit of these electron-deficient metal complexes in low oxidation states demands ancillary ligands capable of providing not only energetic stabilization but also sufficiently high steric bulk at the metal center. From this perspective, pincer ligands are particularly advantageous, as their prearranged, meridional coordination mode scaffolds the active center while the substituents of the peripheral donor atoms provide effective steric shielding for the coordination sphere. In a T-shaped geometry, the transition metal complexes possess a precisely defined vacant coordination site, which, combined with the often observed high-spin electron configuration, exhibits unusually high selectivity of these compounds with respect to one-electron redox chemistry. In light of the intractable reaction pathways typically observed with related electronically unsaturated 3d transition metal complexes, the pincer coordination mode enables the isolation of low-valent compounds with more controlled and unique reactivity. We have thus investigated a series of T-shaped metal(I) complexes using three different types of pincer ligands, which may be regarded as "metalloradicals" due to their selectively exposed unpaired electrons. These compounds display remarkably high thermal stability and represent rarely observed "naked" monovalent metal species featuring both monomeric and dimeric structures. Extensive reactivity studies using various organic substrates highlight a strong tendency of these paramagnetic compounds to undergo one-electron oxidation, leading to the isolation of a plethora of metal(II) species with reduced organic ligands as unusual structural elements. The exploration of C 2 symmetric T-shaped Ni(I) complexes as asymmetric catalysts also shows success in enantioselective hydrodehalogenation of geminal dihalogenides. In addition, this specific class of low-valent, low-coordinate complexes can be further diversified by introducing redox-active pincer ligands or building homobimetallic systems with two T-shaped units. This Account focuses on the discussion of selected examples of iron, cobalt, and nickel pincer complexes bearing a [P,N,P] or [N,N,N] donor set; however, their electronic structure and radical-type reactivity can be broadly extended to other pincer systems.The availability of various types of pincer ligands should allow fine-tuning of the reactivity of the T-shaped complexes. Given the unprecedented reactivity observed with these compounds, we expect the studies of T-shaped 3d metal complexes to be a fertile field for advancing base metal catalysis.

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Synthesis, characterization, and reactivity of a novel magnetically recyclable triazine‐based Cu–NNN–pincer complex

Ahmed

Amani

2022

Applied Organom Chemis

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A new heterogeneous catalytic system containing triazine-based copper(II) tridentate-NNN-pincer complex, covalently anchored to the aminefunctionalized silica-coated Fe 3 O 4 magnetic nanoparticles, Fe 3 O 4 @SiO 2 -NH-CCl-AT-Cu(II), was synthesized. Its structure was studied through the standard methods of FT-IR, NMR, EDX, TGA, FE-SEM, MAP images, XRD, ICP, and N 2 adsorption-desorption isotherm analysis and utilized for the production of propargylamines by one-pot A 3 coupling of phenylacetylene, aldehydes, and secondary amines, attaining TOF values of up to 40,000 h À1 . The impact of various solvents, reaction time, temperature, catalyst amount, and recyclability of the catalyst were studied to optimize reaction conditions. The catalyst was re-examined five times, and no noteworthy reduction in activity was observed. K E Y W O R D S2-amino-5-mercapto-1,3,4-thiadiazole (denoted as AT), A 3 coupling reaction, copper(II), propargylamine, triazine-based NNN-pincer ligand

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New Chemistry with Anionic NNN Pincer Ligands

Cited by 15 publications

References 124 publications

LNL-Carbazole Pincer Ligand: More than the Sum of Its Parts

LNL-Carbazole Pincer Ligand: More than the Sum of Its Parts

3d Metal Complexes in T-shaped Geometry as a Gateway to Metalloradical Reactivity

Synthesis, characterization, and reactivity of a novel magnetically recyclable triazine‐based Cu–NNN–pincer complex

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