Stabilities of Immonium Ions Derived from N‐Heterocyclic Carbenes Probed by Collision‐Induced Dissociation Mass Spectrometry

Polyakova, Svetlana M.; Kunetskiy, Roman A.; Schröder, Detlef

doi:10.1002/ejoc.201200386

Cited by 3 publications

(2 citation statements)

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“…In principle, their synthesis is analogous to that reported in 2009 by Lyapkalo, who accessed the tetrafluoroborate salts 335 by combination of 2-chloro- and 2-aminoimidazolium salts (Scheme ). An unsymmetrical derivative [(ICy)N(IPr)]BF 4 was also synthesized, and the stability of these dicarbene–nitrogen ions was probed by collision-induced dissociation mass spectrometry . In agreement with the theoretical calculations, the molecular structures of the cations in 335a and 335b reveal exocyclic nitrogen atoms in a bent environment with C–N–C angles of 124.96(13)° and 122.8(2)°, respectively (Figure ).…”

Section: N-heterocyclic Carbene Adducts Of Group 15 Elementsmentioning

confidence: 99%

“…497 An unsymmetrical derivative [(ICy)N(IPr)]BF 4 was also synthesized, and the stability of these dicarbene−nitrogen ions was probed by collision-induced dissociation mass spectrometry. 498 In agreement with the theoretical calculations, the molecular structures of the cations in 335a and 335b reveal exocyclic nitrogen atoms in a bent environment with C−N−C angles of 124.96(13)°and 122.8(2)°, respectively (Figure 38). Surprisingly, no transition metal complexes have been reported to date, which could be ascribed to a weaker donating ability in comparison with neutral carbodicarbene species, as suggested from the comparison of the calculated first and second bond dissociation energies in mono-and digold complexes of the type [{(IMe) 2 N}(AuCl) n ] + and [{(IMe) 2 C}(AuCl) n ] (n = 1, 2).…”

Section: Chemical Reviewsmentioning

confidence: 99%

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N-Heterocyclic Carbene Adducts of Main Group Elements and Their Use as Ligands in Transition Metal Chemistry

2019

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N-Heterocyclic carbenes (NHC) are nowadays ubiquitous and indispensable in many research fields, and it is not possible to imagine modern transition metal and main group element chemistry without the plethora of available NHCs with tailor-made electronic and steric properties. While their suitability to act as strong ligands toward transition metals has led to numerous applications of NHC complexes in homogeneous catalysis, their strong σ-donating and adaptable π-accepting abilities have also contributed to an impressive vitalization of main group chemistry with the isolation and characterization of NHC adducts of almost any element. Formally, NHC coordination to Lewis acids affords a transfer of nucleophilicity from the carbene carbon atom to the attached exocyclic moiety, and low-valent and lowcoordinate adducts of the p-block elements with available lone pairs and/or polarized carbon-element π-bonds are able to act themselves as Lewis basic donor ligands toward transition metals. Accordingly, the availability of a large number of novel NHC adducts has not only produced new varieties of already existing ligand classes but has also allowed establishment of numerous complexes with unusual and often unprecedented element−metal bonds. This review aims at summarizing this development comprehensively and covers the usage of N-heterocyclic carbene adducts of the p-block elements as ligands in transition metal chemistry.

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Section: N-heterocyclic Carbene Adducts Of Group 15 Elementsmentioning

confidence: 99%

Section: Chemical Reviewsmentioning

confidence: 99%

N-Heterocyclic Carbene Adducts of Main Group Elements and Their Use as Ligands in Transition Metal Chemistry

2019

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Investigation of Geminally Diaurated Arene Complexes in the Gas Phase

2015

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The stability of gem-diaurated arene complexes [Au 2 (L) 2 (μ-aryl)] + has been investigated by collision-induced dissociation (CID) experiments and density functional theory (DFT) calculations. Performed mass spectrometric experiments revealed the influence of arene-ring substituents and a gold supporting ligand L on the stability of the corresponding diaurated complexes. From the determined appearance energies it emerged that the electron-donating substituents (p-MeO, p-Me, m-MeO, m-Me) strengthen, while the electron-withdrawing ones (p-Cl, p-CN, p-NO 2 , m-Cl, m-CN, m-NO 2 ) weaken the three-center two-electron bond. More stable gem-diaurated complexes were found with electron-poor supporting ligands. It was found, however, that the electronic influences can be surpassed by the steric factors. Experimental results agree well with the performed DFT calculations at the mPW1PW91/cc-pVDZ:LanL2DZ(Au) level of theory. ■ INTRODUCTIONDinuclear gold complexes have been recently recognized as possible intermediates involved in gold-promoted catalytic transformations of alkynes. Generally, two classes of diaurated complexes are frequently mentioned in the context of gold catalysis, namely, σ,π-dicoordinated acetylides 1 and gemdiaurated vinyl and aryl complexes. 2 Collected experimental evidence convincingly showed that two gold centers can efficiently cooperate in the catalysis of chemical reactions via σ,π-activation of polyunsaturated substrates, typically diynes 3 or allenynes. 4 While the concept of dual σ,π-activation of a single substrate is being widely accepted, 5,6 the role of gem-diaurated complexes in gold catalysis remains still a subject of debate. Currently, the prevailing understanding is that gem-diaurated complexes are formed during the catalytic cycle rather as catalyst resting states than genuine reactive intermediates. 7 Still, the current upswing of gold catalysis brought about renewed interest in investigation of these species with particular focus on their preparation and structural characterization. 8,9 The groups of Gray 9a and Nolan 9b have developed convenient and general synthetic procedures affording gem-diaurated complexes smoothly and in high yields starting from arylboronic acids and suitable gold precursors.Our group reported a mechanistic study concerning the role of gem-diaurated complexes in the addition of methanol to alkynes catalyzed by Au(PMe 3 ) + . 10 Based on electrospray ionization mass spectrometric (ESI-MS) experiments, NMR kinetics, infrared multiphoton dissociation spectroscopy (IRMPD), and DFT calculations, it was suggested that the gem-diaurated species are formed as reaction intermediates and that their formation is connected with a dual activation. As a part of our ongoing research efforts aimed at the study of reaction intermediates involved in gold promoted transformations, 10,11 we have decided to investigate a group of gem-diaurated complexes derived from selected arylboronic acids by means of energy-dependent collision-induced dissociation (CID) experiments. The ...

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Sustainable and cost-efficient electro-synthesis of formamidine acetate from cyanamide in aqueous acidic electrolyte

et al. 2021

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Stabilities of Immonium Ions Derived from N‐Heterocyclic Carbenes Probed by Collision‐Induced Dissociation Mass Spectrometry

Cited by 3 publications

References 30 publications

N-Heterocyclic Carbene Adducts of Main Group Elements and Their Use as Ligands in Transition Metal Chemistry

N-Heterocyclic Carbene Adducts of Main Group Elements and Their Use as Ligands in Transition Metal Chemistry

Investigation of Geminally Diaurated Arene Complexes in the Gas Phase

Sustainable and cost-efficient electro-synthesis of formamidine acetate from cyanamide in aqueous acidic electrolyte

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