Functionalization of an iridium–diamidocarbene complex by ligand-based reactions with titanocene and zirconocene sources

Liberman‐Martin, Allegra L.; Ziegler, Micah S.; DiPasquale, Antonio G.; Bergman, Robert G.; Tilley, T. Don

doi:10.1016/j.poly.2016.03.044

Cited by 10 publications

(5 citation statements)

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“…Therefore, triarylsilylium and diarylalkylsilylium ions are significant stronger Lewis acids than neutral boron compounds such as B(C 6 F 5 ) 3 (Δδ 31 P = 30.6) and B(OC 6 F 5 ) 3 (Δδ 31 P = 34.5) 4 or than the neutral silicon Lewis acid Si(CatF) 2 , 11 (Δδ 31 P = 35.9), recently reported by Liberman-Martin et al (Scheme 3). 33 Their Lewis acidity is in the same range as that determined for electrophilic phosphorus(V) cations such as [(F 5 C 6 ) 3 PF] + , 12 (Δδ 31 P = 40.4). 8 Silylium ions are outperformed with respect to Lewis acidity only by cationic borenium compounds such as 13.…”

Section: ■ Results and Discussionmentioning

confidence: 74%

Quantitative Assessment of the Lewis Acidity of Silylium Ions

et al. 2015

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The Lewis acidity of several aryl-substituted tetrylium ions was classified experimentally by applying the Gutmann−Beckett method and computationally by calculation of fluoride ion affinities (FIA) (tetrel elements = Si, Ge). According to these measures, tetrylium ions are significantly more Lewis acidic than boranes, and aryl-substituted silylium borates are among the strongest isolable Lewis acids. A finetuning of the Lewis acidity of silylium ions is possible by taking advantage of electronic and/or steric substituent effects.

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Section: ■ Results and Discussionmentioning

confidence: 74%

Quantitative Assessment of the Lewis Acidity of Silylium Ions

et al. 2015

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“…Other systems with Pt nanoparticles on silica have shown that addition of Zn leads to higher turnover rates for dehydrogenation catalysis likely due to the electronic modulation of the Pt center . Similar effects have been studied in the homogeneous literature with the use of Lewis acid triggers. − In these systems, remote binding of a Lewis acid to the ligand framework has been shown to modulate the reactivity of the transition metal (Figure C). Specifically, the binding of B(C 6 F 5 ) 3 at remote nitrogen positions of the pyrazine ligand leads to an increase in electrophilicity at the Pt, which then led to a 64 000-fold rate acceleration for biaryl reductive elimination.…”

Section: Modified Silica Supportsmentioning

confidence: 68%

Nontraditional Catalyst Supports in Surface Organometallic Chemistry

et al. 2020

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The field of Surface Organometallic Chemistry (SOMC) aims to blend the positive attributes of homogeneous and heterogeneous catalysis. Significant insight into heterogeneous systems has been gained over the years through the synthesis, characterization, and application of well-defined surface organometallic catalysts, predominantly supported on silica and alumina. Considerable research efforts have focused on the application of homogeneous methods to the synthesis and characterization of these systems. Homogeneous catalysis has thrived on its ability to electronically and sterically tune ligands to yield desired reactivity and selectivity. Efforts in SOMC, however, have only recently turned to harnessing the stereoelectronic diversity of potential inorganic support materials beyond silica and alumina in order to exert similar control on the reactivity of the organometallic active site. The support material is intrinsically linked to electronic structure and reactivity of heterogeneous organometallic systems in the same way that ligands exert control over homogeneous catalyst systems. The ability to tune the reactivity of heterogeneous catalysts by changing the support is of great value, and it is anticipated that this will represent an area of significant growth in the field. In this Perspective, the use and future of nontraditional catalyst supports, such as sulfated metal oxides, modified silicas, and redox active supports are discussed.

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“…This design strategy has been employed for a wide range of complexes, where protonation/deprotonation, interactions with a Lewis acid, or addition of an electrophile in the secondary sphere has led to significant rate enhancements in stoichiometric and catalytic processes (Figure ). ,− …”

Section: Protic Groups Remote From the Reactive Sitementioning

confidence: 99%

Hydrogen Transfer Catalysis beyond the Primary Coordination Sphere

Hale

Szymczak

2018

ACS Catal.

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In this Perspective, we outline recent examples of homogeneous transition-metal hydrogen transfer catalysts for which functionality within the complex's outer coordination sphere influences the outcome of a reaction. Secondarysphere groups are often applied to hydrogen transfer reactions, but their specific role during catalysis is not always wellunderstood. New experimental and theoretical work details the complexity associated with predicting secondary-sphere interactions and therefore designing improved catalysts. This Perspective highlights examples of catalysts containing secondary-sphere groups that (1) accelerate a key turnoverlimiting step such as H 2 heterolysis or hydride transfer, (2) limit competing catalytic cycles, (3) prevent catalyst decomposition, and/or (4) provide access to new catalysts through postmetalation modifications. The examples described herein emphasize numerous roles of the secondary sphere in hydrogen transfer catalysis and illustrate how the optimal use of these interactions is predicated on the analyses of key reaction intermediates in a catalytic reaction.

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Functionalization of an iridium–diamidocarbene complex by ligand-based reactions with titanocene and zirconocene sources

Cited by 10 publications

References 60 publications

Quantitative Assessment of the Lewis Acidity of Silylium Ions

Quantitative Assessment of the Lewis Acidity of Silylium Ions

Nontraditional Catalyst Supports in Surface Organometallic Chemistry

Hydrogen Transfer Catalysis beyond the Primary Coordination Sphere

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