2020
DOI: 10.3390/molecules25092231
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NHC Core Pincer Ligands Exhibiting Two Anionic Coordinating Extremities

Abstract: The chemistry of NHC core pincer ligands of LX2 type bearing two pending arms, identical or not, whose coordinating center is anionic in nature, is here reviewed. In this family, the negative charge of the coordinating atoms can be brought either by a carbon atom via a phosphonium ylide (R3P+–CR2−) or by a heteroatom through amide (R2N−), oxide (RO−), or thio(seleno)oxide (RS−, RSe−) donor functionalities. Through selected examples, the synthetic methods, coordination properties, and applications of such tride… Show more

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Cited by 38 publications
(33 citation statements)
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“…One strategy that has been successfully employed in the past years to reduce catalyst loadings and enhance the catalytic potential of metal complexes is the introduction of one or more N -heterocyclic carbene (NHC) ligands. Despite high-valent molybdenum­(VI)-oxo NHC complexes having been found to be rare and lack stability, Buchmeiser and co-workers have shown that NHC ligands are indeed valuable supporting ligands in high-valent molybdenum- and tungsten-catalyzed metathesis reactions. Closing the gap for dioxo, oxo-imido, and bis-imido molybdenum complexes we have recently discovered the facile and simple synthesis of a series of high-valent molybdenum­(VI) NHC complexes 1 – 3 (compare Figure ) , taking advantage of anionic tethered NHC-ligands, using a pincer-type OCO-benzimidazolylidene ligand originally introduced by Bellemin-Laponnaz and Bercaw. …”
Section: Introductionmentioning
confidence: 99%
“…One strategy that has been successfully employed in the past years to reduce catalyst loadings and enhance the catalytic potential of metal complexes is the introduction of one or more N -heterocyclic carbene (NHC) ligands. Despite high-valent molybdenum­(VI)-oxo NHC complexes having been found to be rare and lack stability, Buchmeiser and co-workers have shown that NHC ligands are indeed valuable supporting ligands in high-valent molybdenum- and tungsten-catalyzed metathesis reactions. Closing the gap for dioxo, oxo-imido, and bis-imido molybdenum complexes we have recently discovered the facile and simple synthesis of a series of high-valent molybdenum­(VI) NHC complexes 1 – 3 (compare Figure ) , taking advantage of anionic tethered NHC-ligands, using a pincer-type OCO-benzimidazolylidene ligand originally introduced by Bellemin-Laponnaz and Bercaw. …”
Section: Introductionmentioning
confidence: 99%
“…On the basis of this knowledge, considerable effort has been provided to introduce structural diversity, and a large variety of polydentate NHC ligands bearing coordinating atoms of different nature (N, P, O, and C) have been prepared improving the efficiency and selectivity of metal complexation. In particular, NHC-based ligands exhibiting L-type coordinating extremities such as pyridine and phosphine donors or X-type such as phenolate and phosphonium ylide donors were notably devised in the bi- and tridentate series naturally extending the scope of accessible metal fragments.…”
Section: Introductionmentioning
confidence: 99%
“…Scorpionate ligands, on the other hand, were first developed in the late 1960s by Trofimenko, and include species like tris­(pyrazolyl)­borate , and tris­(pyrazolyl)­methane (Figure ). The defining features of these ligands are a fac coordination geometry and the ability to interchange between tridentate and bidentate binding modes. , This hemilability can lead to higher reactivity levels over other tridentate ligands, such as pincer ligands, which tend to form very stable complexes. , Moreover, scorpionate ligands are extremely versatile in that their bonding strengths, electronic parameters, and steric encumbrance can be readily tuned. Since their development, complexes incorporating these types of ligands have been widely studied for medical purposes, catalysis, as well as other applications. ,, Surprisingly, despite their versatility, to the best of our knowledge, only a handful of scorpionate ligands have been explored on aluminum centers. Martínez et al investigated a family of aluminum scorpionate complexes for the catalytic synthesis of cyclic carbonates from epoxides and carbon dioxide. , Additionally, aluminum scorpionate complexes have been utilized by the Otero group, and others, to affect the ROP of lactide and ε-CL. , By increasing the steric bulk of the tridentate ligands, more control over polymerization was seen and products with narrower PDIs were generated .…”
Section: Introductionmentioning
confidence: 99%
“…58,59 This hemilability can lead to higher reactivity levels over other tridentate ligands, such as pincer ligands, which tend to form very stable complexes. 60,61 Moreover, scorpionate ligands are extremely versatile in that their bonding strengths, electronic parameters, and steric encumbrance can be readily tuned. Since their development, complexes incorporating these types of ligands have been widely studied for medical purposes, 62 catalysis, 63 as well as other applications.…”
Section: ■ Introductionmentioning
confidence: 99%