Theoretical studies of iridium-mediated tautomerization of substituted pyridines

Su, Yan; Song, Guoyong; Han, Keli; Li, Xingwei

doi:10.1016/j.jorganchem.2011.01.029

Cited by 11 publications

(10 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…DFT studies of the metalation process suggest an initial C–H oxidative addition to give a five-coordinate iridium(III) hydride intermediate . Calculations reveal two plausible pathways for the subsequent 1,3-shift of the iridium-bound hydrogen to the pyridyl nitrogen including either β-H insertion or a water-assisted proton transfer with the latter more favored energetically.…”

Section: Complexes With Pyridylidenes and Related Ligandsmentioning

confidence: 99%

Mesoionic and Related Less Heteroatom-Stabilized N-Heterocyclic Carbene Complexes: Synthesis, Catalysis, and Other Applications

2018

View full text Add to dashboard Cite

Mesoionic carbenes are a subclass of the family of N-heterocyclic carbenes that generally feature less heteroatom stabilization of the carbenic carbon and hence impart specific donor properties and reactivity schemes when coordinated to a transition metal. Therefore, mesoionic carbenes and their complexes have attracted considerable attention both from a fundamental point of view as well as for application in catalysis and beyond. As a follow-up of an earlier Chemical Reviews overview from 2009, the organometallic chemistry of N-heterocyclic carbenes with reduced heteroatom stabilization is compiled for the 2008-2017 period, including specifically the chemistry of complexes containing 1,2,3-triazolylidenes, 4-imidazolylidenes, and related 5-membered N-heterocyclic carbenes with reduced heteratom stabilization such as (is)oxazolylidenes, pyrrazolylidenes, and thiazolylidenes, as well as pyridylidenes as 6-membered N-heterocyclic carbenes with reduced heteroatom stabilization. For each ligand subclass, metalation strategies, electronic and steric properties, and applications, in particular, in metal-mediated catalysis, are compiled. Mesoionic carbenes demonstrate particularly high activity in (water) oxidation, hydrogen transfer reactions, and cyclization reactions. Unique features of these ligands are identified such as their dipolar structure, their specific donor properties, as well as stability aspects of the ligand and the complexes, which provides opportunities for further research.

show abstract

Section: Complexes With Pyridylidenes and Related Ligandsmentioning

confidence: 99%

Mesoionic and Related Less Heteroatom-Stabilized N-Heterocyclic Carbene Complexes: Synthesis, Catalysis, and Other Applications

2018

View full text Add to dashboard Cite

show abstract

“…Han, Zhang, and Li obtained an equilibrium mixture of the hydrido-pyridyl complex 50 and the protic dihydropyridin-2-ylidene complex 51 by reaction of an iridium(I) precursor with 1,9-phenanthroline (Scheme ). The facile 1,3-H shift between the product of the oxidative addition, 50 , and the complex bearing the protic carbene, 51 , which can be accelerated in the presence of water, appears to be involved in the redox tautomerization reaction sequence. Theoretical studies also support the initial oxidative addition of the C10–H bond of phenanthroline .…”

Section: Synthesismentioning

confidence: 99%

Complexes Bearing Protic N-Heterocyclic Carbene Ligands

2018

View full text Add to dashboard Cite

Complexes bearing protic N-heterocyclic carbenes (protic NHCs, pNHCs), defined as cyclic carbenes stabilized by two heteroatoms including at least one NH group, have been less explored in comparison to the conventional N,N'-disubstituted NHCs. The small and reactive NH group of the pNHCs differentiates this class of compounds from the classical NR,NR-NHCs with regard to their properties and reactivity. While the free pNHCs have so far eluded isolation due to isomerization to the azole tautomer, a significant number of transition-metal pNHC complexes have by now been prepared by a variety of methods. This article reviews the coordination chemistry of the pNHCs. Synthetic approaches toward complexes of pNHCs are first described, followed by a discussion of the properties and reactivity of pNHC complexes with emphasis on the Brønsted-acidic nature of the NH wingtip. Involvement of the pNHC ligands in catalytically active intermediates and in cooperative catalysis is also discussed.

show abstract

“…The equilibrium is significantly shifted to the protic 2-pyridylidene side by the counteranion X and solvent that can form a hydrogen bond with the NH group and thus stabilize the protic carbene ligand. 37,47 Similarly, Brønsted basic substituents at an appropriate position on the pyridine ring advantage the protic carbene isomer. 36,47 The 1,3-shift associated with formal redox of the metal center and umpolung of the hydrido ligand is accelerated by water, which participates in the proton transfer through a cyclic transition state.…”

Section: Reversible Deprotonationmentioning

confidence: 99%

“…37,47 Similarly, Brønsted basic substituents at an appropriate position on the pyridine ring advantage the protic carbene isomer. 36,47 The 1,3-shift associated with formal redox of the metal center and umpolung of the hydrido ligand is accelerated by water, which participates in the proton transfer through a cyclic transition state. (6) Oxidative addition of 2-bromopyridines bearing nitrogen and sulfur donor tethers to [Pd(dba) 2 ] (dba = dibenzylideneacetone) affords a series of dinuclear complexes 40.…”

Section: Reversible Deprotonationmentioning

confidence: 99%

Metal–ligand bifunctional reactivity and catalysis of protic N-heterocyclic carbene and pyrazole complexes featuring β-NH units

2014

View full text Add to dashboard Cite

Metal-ligand bifunctional cooperation has attracted much attention because it offers a powerful methodology to realize a number of highly efficient and selective catalysts. In this article, recent developments in the metal-ligand cooperative reactions of protic N-heterocyclic carbene (NHC) and pyrazole complexes bearing an acidic NH group at the position β to the metal are surveyed. Protic 2-pyridylidenes as related cooperating non-innocent ligands are also described.

show abstract

Theoretical studies of iridium-mediated tautomerization of substituted pyridines

Cited by 11 publications

References 65 publications

Mesoionic and Related Less Heteroatom-Stabilized N-Heterocyclic Carbene Complexes: Synthesis, Catalysis, and Other Applications

Mesoionic and Related Less Heteroatom-Stabilized N-Heterocyclic Carbene Complexes: Synthesis, Catalysis, and Other Applications

Complexes Bearing Protic N-Heterocyclic Carbene Ligands

Metal–ligand bifunctional reactivity and catalysis of protic N-heterocyclic carbene and pyrazole complexes featuring β-NH units

Contact Info

Product

Resources

About