Heterolytic bond activation at gold: evidence for gold(iii) H–B, H–Si complexes, H–H and H–C cleavage

We report selective formation of heterobimetallic PtII/CuI complexes that demonstrate how facile bond activation processes can be achieved by altering reactivity of common organoplatinum compounds through their interaction with another metal center. The interaction of the Cu center with Pt center and with a Pt-bound alkyl group increases the stability of PtMe2 towards undesired rollover cyclometalation. The presence of the CuI center also enables facile transmetalation from electron-deficient tetraarylborate [B(ArF)4]- anion and mild C-H bond cleavage of a terminal alkyne, which was not observed in the absence of an electrophilic Cu center. The DFT study indicates that the role of Cu center acts as a binding site for alkyne substrate, while activating its terminal C-H bond.

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Pt-Pd Nanoalloy for the Unprecedented Activation of Carbon-Fluorine Bond at Low Temperature

10.26434/chemrxiv.11145098 ◽

2019 ◽

Author(s):

Raghu Nath Dhital ◽

keigo nomura ◽

Yoshinori Sato ◽

Setsiri Haesuwannakij ◽

Masahiro Ehara ◽

...

Keyword(s):

Activation Energy ◽

Low Temperature ◽

Dft Calculations ◽

Bond Activation ◽

Mild Conditions ◽

Selective Transformation ◽

Rate Determining Step ◽

Highly Active ◽

Harsh Conditions ◽

Reaction Profile

Carbon-Fluorine (C-F) bonds are considered the most inert organic functionality and their selective transformation under mild conditions remains challenging. Herein, we report a highly active Pt-Pd nanoalloy as a robust catalyst for the transformation of C-F bonds into C-H bonds at low temperature, a reaction that often required harsh conditions. The alloying of Pt with Pd is crucial to activate C-F bond. The reaction profile kinetics revealed that the major source of hydrogen in the defluorinated product is the alcoholic proton of 2-propanol, and the rate-determining step is the reduction of the metal upon transfer of the beta-H from 2-propanol. DFT calculations elucidated that the key step is the selective oxidative addition of the O-H bond of 2-propanol to a Pd center prior to C-F bond activation at a Pt site, which crucially reduces the activation energy of the C-F bond. Therefore, both Pt and Pd work independently but synergistically to promote the overall reaction

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The Exchange of Cyclometalated Ligands

Molecules ◽

10.3390/molecules26010210 ◽

2021 ◽

Vol 26 (1) ◽

pp. 210

Author(s):

Alexander D. Ryabov

Keyword(s):

Transition Metal ◽

Metal Complexes ◽

Transition Metal Complexes ◽

Bond Activation ◽

Bond Cleavage ◽

Cyclopalladated Complexes ◽

Derivatives Of ◽

Cyclometalated Ligand ◽

Incoming Ligand

Reactions of cyclometalated compounds are numerous. This account is focused on one of such reactions, the exchange of cyclometalated ligands, a reaction between a cyclometalated compound and an incoming ligand that replaces a previously cyclometalated ligand to form a new metalacycle: + H-C*~Z ⇄ + H-C~Y. Originally discovered for PdII complexes with Y/Z = N, P, S, the exchange appeared to be a mechanistically challenging, simple, and convenient routine for the synthesis of cyclopalladated complexes. Over four decades it was expanded to cyclometalated derivatives of platinum, ruthenium, manganese, rhodium, and iridium. The exchange, which is also questionably referred to as transcyclometalation, offers attractive synthetic possibilities and assists in disclosing key mechanistic pathways associated with the C–H bond activation by transition metal complexes and C–M bond cleavage. Both synthetic and mechanistic aspects of the exchange are reviewed and discussed.

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Carbon-Hydrogen Bond Activation of Phenyldi(2- Thienyl)Phosphine at A Triruthenium Cluster Center

Journal of Bangladesh Chemical Society ◽

10.3329/jbcs.v25i1.11764 ◽

2012 ◽

Vol 25 (1) ◽

pp. 1-6 ◽

Cited By ~ 1

Author(s):

Shahed Rana ◽

Shishir Ghosh ◽

Shariff E Kabir

Keyword(s):

Hydrogen Bond ◽

Elemental Analysis ◽

Bond Activation ◽

Bond Cleavage ◽

Chemical Society ◽

Cluster Center ◽

Carbon Hydrogen Bond Activation

Ketyl-initiated reaction between Ru3(CO)12 and phenyldi(2-thienyl)phosphine (PhPTh2) furnished simple phosphine-substituted triruthenium clusters [Ru3(CO)10(PhPTh2)21 and [Ru3(CO)9(PhPTh2)3] 2. Heating 1 in boiling benzene afforded [Ru3(CO)8{?3- PhThP(C4H2S)}(PhPTh2)] 3 by carbon-hydrogen bond cleavage of a coordinated thienylphosphine ligand. All three new clusters have been characterized by elemental analysis, IR and NMR spectroscopic data.DOI: http://dx.doi.org/10.3329/jbcs.v25i1.11764 Journal of Bangladesh Chemical Society, Vol. 25(1), 1-6, 2012

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Palladium-Catalysed C–F Alumination of Fluorobenzenes: Mechanistic Diversity and Origin of Selectivity

10.26434/chemrxiv.12053601.v1 ◽

2020 ◽

Author(s):

Feriel Rekhroukh ◽

Wenyi Chen ◽

Ryan Brown ◽

Andrew J. P. White ◽

Mark Crimmin

Keyword(s):

Dft Calculations ◽

Bond Activation ◽

Oxidative Addition ◽

Fluorine Content ◽

Model Potential ◽

Heterometallic Complex ◽

Experimental Support ◽

Highly Active ◽

Reaction Proceeds ◽

Directing Group

A palladium pre-catalyst, [Pd(PCy3)2] is reported for the efficient and selective C–F alumination of fluorobenzenes with the aluminium(I) reagent [{(ArNCMe)2CH}Al] (1, Ar = 2,6-di-iso-propylphenyl). The catalytic protocol results in the transformation of sp2 C–F bonds to sp2 C–Al bonds and provides a route into reactive organoaluminium complexes (2a-h) from fluorocarbons. The catalyst is highly active. Reactions proceed within 5 minutes at 25 ºC (and at appreciable rates at even –50 ºC) and the scope includes low-fluorine-content substrates such as fluorobenzene, difluorobenzenes and trifluorobenzenes. The reaction proceeds with complete chemoselectivity (C–F vs C–H) and high regioselectivities ( >90% for C–F bonds adjacent to the most acidic C–H sites). The heterometallic complex [Pd(PCy3)(1)2] was shown to be catalytically competent. Catalytic C–F alumination proceeds with a KIE of 1.1–1.3. DFT calculations have been used to model potential mechanisms for C–F bond activation. These calculations suggest that two competing mechanisms may be in operation. Pathway 1 involves a ligand-assisted oxidative addition to [Pd(1)2] and leads directly to the product. Pathway 2 involves a stepwise C–H to C–F functionalisation mechanism in which the C–H bond is broken and reformed along the reaction coordinate, allowing it to act as a directing group for the adjacent C–F site. This second mechanism explains the experimentally observed regioselectivity. Experimental support for this C–H activation playing a key role in C–F alumination was obtained by employing [{(MesNCMe)2CH}AlH2] (3, Mes = 2,4,6-trimethylphenyl) as a reagent in place of 1. In this instance, the kinetic C–H alumination intermediate could be isolated. Under catalytic conditions this intermediate converts to the thermodynamic C–F alumination product.

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Steric C–N bond activation on the dimeric macrocycle [{P(μ-NR)}2(μ-NR)]2

Chemical Communications ◽

10.1039/c5cc06034f ◽

2015 ◽

Vol 51 (92) ◽

pp. 16468-16471 ◽

Cited By ~ 9

Author(s):

Yan X. Shi ◽

Rong Z. Liang ◽

Katherine A. Martin ◽

Daniel G. Star ◽

Jesús Díaz ◽

...

Keyword(s):

Bond Activation ◽

Bond Cleavage ◽

Elemental Selenium ◽

Cleavage Reaction ◽

Ring Strain

The dimeric macrocyclophosphazane [{P(μ-NtBu)}2(μ-NtBu)]2 ( 1) was reacted with elemental selenium. An unexpected C–N cleavage reaction occurred producing P4(μ-NtBu)3(μ-NH)3Se4 ( 2). The C–N bond cleavage is driven by the high steric ring strain present within the ring.

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Pt(II)-Chiral Diene-Catalyzed Enantioselective Formal [4+2] Cycloaddition Initiated by C-C Bond Cleavage and Elucidation of a Pt(II)/(IV) Cycle by DFT Calculations

Organic Chemistry Frontiers ◽

10.1039/d1qo01467f ◽

2021 ◽

Author(s):

Takanori Shibata ◽

Natsumi Shiozawa ◽

Shun Nishibe ◽

Hideaki Takano ◽

Satoshi Maeda

Keyword(s):

Dft Calculations ◽

Bond Cleavage

A chiral Pt(II) complex was readily prepared from [PtCl2(C2H4)]2 and Hayashi’s diene. Its dicationic derivative efficiently catalyzed a formal intramolecular [4+2] cycloaddition of biphenylenes possessing substituted arylalkynes tethered by an...

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Computational studies on Ni-catalyzed amide C–N bond activation

Chemical Communications ◽

10.1039/c9cc05763c ◽

2019 ◽

Vol 55 (76) ◽

pp. 11330-11341 ◽

Cited By ~ 15

Author(s):

Hongliang Wang ◽

Shuo-Qing Zhang ◽

Xin Hong

Keyword(s):

Bond Activation ◽

Bond Cleavage ◽

Mechanistic Models ◽

Computational Studies

This review summarizes the mechanistic models of Ni-catalyzed amide C–N bond cleavage and discusses their applications in related transformations.

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On the role of the surface oxygen species during A–H (A = C, N, O) bond activation: a density functional theory study

Chemical Communications ◽

10.1039/c4cc08658a ◽

2015 ◽

Vol 51 (13) ◽

pp. 2621-2624 ◽

Cited By ~ 28

Author(s):

Jong Suk Yoo ◽

Tuhin S. Khan ◽

Frank Abild-Pedersen ◽

Jens K. Nørskov ◽

Felix Studt

Keyword(s):

Density Functional ◽

Bond Activation ◽

Bond Cleavage ◽

Oxygen Species ◽

Final States ◽

Surface Oxygen ◽

Density Functional Theory Study ◽

Reaction Energy ◽

Functional Theory

During A–H (A = C, N, O) bond cleavage on O* or OH* pre-covered (111) surfaces, the oxygen species play the role of modifying the reaction energy by changing the species involved in the initial and final states of the reaction.

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