Ion pairing in NHC gold(I) olefin complexes: A combined experimental/theoretical study

Salvi, Nicola; Belpassi, Leonardo; Zuccaccia, Daniele; Tarantelli, Francesco; Macchioni, Alceo

doi:10.1016/j.jorganchem.2010.08.035

Cited by 42 publications

(22 citation statements)

References 74 publications

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“…17 ). 153 These results demonstrate that the counterion is placed away from the gold( i ) site, although the specific localization strongly depends on the neutral ligand (phosphine or NHC).…”

Section: Anion Effectsmentioning

confidence: 77%

Anatomy of gold catalysts: facts and myths

2015

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Section: Anion Effectsmentioning

confidence: 77%

Anatomy of gold catalysts: facts and myths

2015

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“…[17] Lowtemperature 19 F, 1 H HOESY NMR of 2 and related gold Nheterocyclic carbene (NHC) complexes indicated that the BF 4 À counterion is positioned predominantly (65-83 % occupancy) near the IPr imidazole ring remote from the p ligand. [17,18] Brown, Dickens, and Widenhoefer subsequently reported the synthesis of a diverse family of air-and thermally-stable complexes of the form [(IPr)Au(p alkene)]-[SbF 6 ] [alkene = isobutylene (3 a), 2,3-dimethyl-2-butene (3 b), norbornene, 2-methyl-2-butene, methylenecyclohexane, cis-2-butene, 1-hexene, and 4-methylstyrene; Figure 1]. [19] This study included solution and solid-state characterization, analysis of alkene binding affinities, and ligand exchange kinetics.…”

Section: N-heterocyclic Carbene Complexesmentioning

confidence: 99%

Cationic, Two‐Coordinate Gold π Complexes

2013

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Cationic, two-coordinate gold π complexes that contain a phosphine or N-heterocyclic supporting ligand have attracted considerable attention recently owing to the potential relevance of these species as intermediates in the gold-catalyzed functionalization of C-C multiple bonds. Although neutral two-coordinate gold π complexes have been known for over 40 years, examples of the cationic two-coordinate gold(I) π complexes germane to catalysis remained undocumented prior to 2006. This situation has changed dramatically in recent years and well-defined examples of two-coordinate, cationic gold π complexes containing alkene, alkyne, diene, allene, and enol ether ligands have been documented. This Minireview highlights this recent work with a focus on the structure, bonding, and ligand exchange behavior of these complexes.

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“…Our experimental work makes use of advanced NMR spectroscopic techniques such as NOE27–29 and pulsed field gradient spin‐echo (PGSE) NMR spectroscopy,30 which we have developed31 and found particularly suitable for gaining detailed information on the relative anion–cation orientation in solution and on the degree of aggregation of the organometallic compounds. Combined with extensive computational studies of the potential energy surfaces and Coulomb potential of the ions, these approaches give detailed information on the structure and on the strength of the ion pairs and may also help in characterizing the most important interactions at the origin of a given ion‐pair structure 32–34. Both phosphane and carbenes have been investigated as effective ligands, showing that the anion position is strongly affected by the ligand and may be finely modulated, with varying intensity, by substituent groups.…”

Section: Introductionmentioning

confidence: 99%

Ligand Effects on Bonding and Ion Pairing in Cationic Gold(I) Catalysts Bearing Unsaturated Hydrocarbons

et al. 2013

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We critically review recent experimental and theoretical investigations into some key aspects of the chemistry of gold(I) complexes of the type [L-Au-S]X-+(-) (L = NHC carbenes and phosphanes, S = alkenes and alkynes, and X- = weakly coordinating counterion). These systems are important intermediates formed during gold-catalyzed nucleophilic additions to an unsaturated substrate, and their specific activity is largely governed by two fundamental factors: the nature of the gold-substrate bond and the role of the ion-pair structure in solution. Both are crucially influenced by the nature and properties of the auxiliary ligand L, and on this interplay we focus our discussion. The relative anion-cation orientation, investigated by NOE NMR spectroscopy and DFT calculations, shows that the exact position of the counterion is determined by the natures of the ancillary ligand and substrate: the counterion is located near the substrate in the phosphane complexes, while for the NHC complexes the preferred position of the counterion is near the ligand. This tunable interionic structure opens the way to greater control over the properties and activity of these catalysts. The bond between Au-I and the unsaturated substrate is investigated using an original and powerful theoretical method of analysis. Our approach permits a rigorous definition and assessment of the charge-displacement (CD) components at the heart of the Dewar-Chatt-Duncanson model: substrate-to-metal (sigma donation) and metal-to-substrate (back-donation) and how these change with different ligands. The results consistently reveal that back-donation is a large and crucially important component of the Au-I-substrate bond in all systems: back-donation penetrates the external side of coordinated alkynes, where nucleophile attack is directed, thus partially mitigating the electron depletion caused by sigma donation

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Ion pairing in NHC gold(I) olefin complexes: A combined experimental/theoretical study

Cited by 42 publications

References 74 publications

Anatomy of gold catalysts: facts and myths

Anatomy of gold catalysts: facts and myths

Cationic, Two‐Coordinate Gold π Complexes

Ligand Effects on Bonding and Ion Pairing in Cationic Gold(I) Catalysts Bearing Unsaturated Hydrocarbons

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