Dearomatization of Transition Metal-Coordinated N-Heterocyclic Ligands and Related Chemistry

Arévalo, Rebeca; Espinal‐Viguri, Maialen; Huertos, Miguel A.; Pérez, Julio; Riera, Lucı́a

doi:10.1016/bs.adomc.2016.03.002

Cited by 12 publications

(8 citation statements)

References 171 publications

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“…The ability to synthetically manipulate ligand additives for catalysis has enabled the development of a large selection of commercially available organometallic precatalysts and ligands for use in catalytic reactions. N -heterocyclic carbenes (NHCs) are a particularly popular class of ligand additives and have been used in a vast number of catalytic reactions as organocatalysts, 1,2 and in tandem with transition metals 3–9 and Group 13 elements. 1,2,10 NHCs are available in the form of stable salts with a large number of different N -substituents, central ring size, and even central ring functionalization, making them very easy to access and work with.…”

Section: Introductionmentioning

confidence: 99%

Combined Effects of Backbone and N-Substituents on Structure, Bonding, and Reactivity of Alkylated Iron(II)-NHCs

et al. 2018

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Iron and N-heterocyclic carbenes (NHCs) have proven to be a successful pair in catalysis, with reactivity and selectivity being highly dependent on the nature of the NHC ligand backbone saturation and N-substituents. Four (NHC)Fe(1,3-dioxan-2-ylethyl)2 complexes have been isolated and spectroscopically characterized to correlate their reactivity to steric effects of the NHC from both the backbone saturation and N-substituents. Only in the extreme case of SIPr where NHC backbone and N-substituent steric effects are the largest is there a major structural perturbation observed crystallographically. The addition of only two hydrogen atoms is sufficient for a drastic change in product selectivity in the coupling of 1-iodo-3-phenylpropane with (2-(1,3-dioxan-2-yl)ethyl)magnesium bromide due to resulting structural perturbations to the precatalyst. Mössbauer spectroscopy and magnetic circular dichroism enabled the correlation of covalency and steric bulk in the SIPr case to its poor selectivity in alkyl–alkyl cross-coupling with iron. Density functional theory calculations provided insight into the electronic structure and molecular orbital effects of ligation changes to the iron center. Finally, charge donation analysis and Mayer bond order calculations further confirmed the stronger Fe–ligand bonding in the SIPr complex. Overall, these studies highlight the importance of considering both N-substituent and backbone steric contributions to structure, bonding, and reactivity in iron-NHCs.

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Section: Introductionmentioning

confidence: 99%

Combined Effects of Backbone and N-Substituents on Structure, Bonding, and Reactivity of Alkylated Iron(II)-NHCs

et al. 2018

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“…This behavior of the ligand is already reported for structurally analogous ligands with a number of metal ions. 27,28 In some reports 29,30 , both nitrogen atoms of the thiazole ring gave two isomers with different biological activities.…”

Section: Chemistry and X-ray Diffractionmentioning

confidence: 99%

Methyl-substituted 2-aminothiazole–based cobalt(II) and silver(I) complexes:synthesis, X-ray structures, and biological activities

Khan¹,

Ahmad²,

Gul³

et al. 2019

Turk J Chem

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2-Aminothiazole derivatives bear three nucleophilic centers, i.e. endocyclic N, exocyclic NH 2 , and S atom in the ring system. In addition to these centers there are π-electrons in the ring system which can also expectedly be involved in some sort of coordination. To the best of our knowledge the solid state coordination chemistry of such ligands has not been fully presented in the literature. These ligands (2-amino-4-methylthiazole and 2-amino-5-methylthiazole) were coupled with CoCl 2 under aerobic conditions to form tetrahedral complexes, bis(2-amino-4methylthiazole)dichlorocobalt(II) (1) and bis(2-amino-5-methylthiazole)dichlorocobalt(II) (2). Reaction of 2-amino-5-methylthiazole with AgNO 3 led to an expected two-coordinated, bis(2-amino-5-methylthiazole)silver(I) nitrate (3) as crystalline material. In all complexes the coordination behavior of the aminothiazole derivatives was identical, coordinating to the metal center through endocyclic N atom. The structures of these complexes were confirmed by single-crystal X-ray analysis. Compounds (1-3) were screened for their antimicrobial potency against gram-negative (E. sakazkii, E. coli, K. pneumoniae) and a gram-positive bacteria (S. aurus). Additionally, their role as enzyme inhibitors (acetylcholinesterase, AChE, and butyrylcholinesterase, BChE) and their free radical scavenging ability (2,2-Diphenyl-1-picrylhydrazyl, DPPH, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid, ABTS) were studied. These ligands bear additional nucleophilic centers (S and NH 2) and can be involved in secondary interactions as confirmed by their solid-state structures. These interactions make the molecules biologically important and thus play a pivotal role in establishing the supramolecular network. We report here the coordination chemistry and selected biological applications of complexes 1-3.

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“…In previouss tudies, we showedt hat bipy and phenc oordinated to cationic fac-rhenium(I)t ricarbonyl [14] or cis-molybdenum(II) dicarbonyl [14a, e] fragments are not chemically inert ligands [15] and can undergo, under very mild conditions, the addition of internal nucleophiles generated, in most cases, by deprotonationo fa ppropriately positioned co-ligands (Scheme 1a). As ar esult of the additions being intramolecular, the C(sp 3 )c enters were built on the chelate positions closest to the metal fragment-C2 upon deprotonation of SMe 2 [16] and C6 upon deprotonation of N-alkylimidazoles, [14a, b, e] PMe 3 , [17] or a-methyl-N-heterocycles.…”

Section: Introductionmentioning

confidence: 99%

Building C(sp³) Molecular Complexity on 2,2′‐Bipyridine and 1,10‐Phenanthroline in Rhenium Tricarbonyl Complexes

Arévalo

López

Falvello

et al. 2020

Chemistry A European J

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Ther eactions of [Re(N-N)(CO) 3 (PMe 3)]OTf (N-N = 2,2'-bipyridine, bipy;1 ,10-phenanthroline, phen) compounds with tBuLi andw ith LiHBEt 3 have been explored. Addition to the N-N chelate took place with different site-selectivity dependingo nb othc helate and nucleophile. Thus, with tBuLi, an unprecedenteda ddition to C5 of bipy,aregiochemistry not accessible for free bipy, was obtained, whereas coordinated phen underwent tBuLi addition to C2 and C4. Remarkably,when LiHBEt 3 reactedwith [Re(bipy)(CO) 3 (PMe 3)]OTf, hy-dride addition to the 4a nd 6p ositions of bipy triggered an intermolecularc yclodimerization of two dearomatized pyridyl rings. In contrast, hydride addition to the phen analog resultedi np artial reduction of one pyridine ring. The resulting neutral Re I products showedav aried reactivity with HOTf and with MeOTf to yield cationic complexes.T hese strategies rendereda ccess to Re I complexes containing bipy-and phen-derived chelatesw ith several C(sp 3)c enters.

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Dearomatization of Transition Metal-Coordinated N-Heterocyclic Ligands and Related Chemistry

Cited by 12 publications

References 171 publications

Combined Effects of Backbone and N-Substituents on Structure, Bonding, and Reactivity of Alkylated Iron(II)-NHCs

Combined Effects of Backbone and N-Substituents on Structure, Bonding, and Reactivity of Alkylated Iron(II)-NHCs

Methyl-substituted 2-aminothiazole–based cobalt(II) and silver(I) complexes:synthesis, X-ray structures, and biological activities

Building C(sp³) Molecular Complexity on 2,2′‐Bipyridine and 1,10‐Phenanthroline in Rhenium Tricarbonyl Complexes

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Dearomatization of Transition Metal-Coordinated N-Heterocyclic Ligands and Related Chemistry

Cited by 12 publications

References 171 publications

Combined Effects of Backbone and N-Substituents on Structure, Bonding, and Reactivity of Alkylated Iron(II)-NHCs

Combined Effects of Backbone and N-Substituents on Structure, Bonding, and Reactivity of Alkylated Iron(II)-NHCs

Methyl-substituted 2-aminothiazole–based cobalt(II) and silver(I) complexes:synthesis, X-ray structures, and biological activities

Building C(sp3) Molecular Complexity on 2,2′‐Bipyridine and 1,10‐Phenanthroline in Rhenium Tricarbonyl Complexes

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Building C(sp³) Molecular Complexity on 2,2′‐Bipyridine and 1,10‐Phenanthroline in Rhenium Tricarbonyl Complexes