Unexpected rearrangements in the synthesis of an unsymmetrical tridentate dianionic N-heterocyclic carbene

Starting from the same ethylenediamine species, three valuable carbene precursors were synthesized under differing conditions: a tridentate dianionic N-heterocyclic carbene bearing an aniline, a phenol and a central dihydroimidazolium salt, its benzimidazolium isomer by intramolecular rearrangement and a dicationic benzimidazolium-benzoxazolium salt by changing the Brønsted acid from HCl to HBF_4. A DFT study was performed to understand the rearrangement pathway. The structure of a bis[(NCO)carbene] zirconium complex was determined

Combining ligand-enhanced backdonation and steric shielding to stabilize a mono-substituted Au( i ) carbene

International audienceA mono-substituted Au(i) carbene was prepared by reacting HC(N2)(Dmp) (Dmp = 2,6-dimesitylphenyl) with an (o-carboranyl)-diphosphine AuNTf2 complex. It is stable up to −10 °C and was characterized by NMR spectrocopy. According to DFT calculations, the chelating P^P ligand enhances Au → Ccarb backdonation, while the Dmp substituent provides kinetic stabilization but does not bias the electronic structure of the carbene comple

Silver-mediated intramolecular P–C coupling

International audienceSilver(I) salts mimic copper(I) but not gold(I) salts in the reaction with peri-iodo naphthyldiisopropylphosphine. The formation of the corresponding peri-cyclic phosphonium derivatives represents the first example of silver-mediated P–C coupling through a two-electron redox sequence

Mechanistic Insights about the Ligand‐Enabled Oxy‐arylation/vinylation of Alkenes via Au(I)/Au(III) Catalysis

International audienceThe mechanism of oxy-arylation/vinylation of alkenes catalyzed by the (MeDalphos)AuCl complex was comprehensively investigated by DFT. (P,N)Au(Ph) 2 + and (P,N)Au(vinyl) 2 + are key intermediates accounting for the activation of the alkenols and for their cyclization by outersphere nucleophilic attack of oxygen. The 5-exo and 6-endo paths have been computed and compared, reproducing the peculiar regioselectivity difference observed experimentally between 4-penten-1-ol, (E) and (Z)-4-hexen-1-ols. Examining the way the alkenol coordinates to gold (more η 2 or η 1) can offer, in some cases, a simple way to predict the favored path of cyclization

Coordination of phosphinoboranes R 2PB(C 6F 5) 2 to platinum: An alkene-type behavior

cited By 21International audienceThe paucity of boron-containing heteroalkene complexes prompted us to explore the coordination of phosphinoboranes. The complexes [R 2PB(C 6F 5) 2]Pt(PPh 3) 2 (R = Cy, t-Bu) were obtained by ethylene displacement. Spectroscopic and crystallographic data indicated symmetric side-on coordination of the phosphinoborane to Pt. Thorough analysis of the bonding situation by computational means revealed important similarities but also significant differences between the phosphinoborane and ethylene complexes. © 2012 American Chemical Society

Stable (amino)(phosphino)carbenes: Difunctional molecules

cited By 69International audience(Amino)(phosphino)carbenes are stable due to the donation of the nitrogen lone pair, the phosphino group remains strongly pyramidalized. Reactions can be performed selectively at the carbene center, but also at the phosphorus center leading to new stable carbenes. These difunctional molecules can be considered as hybrid ligands. Copyright © 2002 American Chemical Society

Gold(I) α‐Trifluoromethyl Carbenes: Synthesis, Characterization and Reactivity Studies

International audienceAryl trifluoromethyl diazomethanes 2-R (R = Ph, OMe, CF 3) are readily decomposed by the (o-carboranyl)diphosphine gold(I) complex 1. The resulting α-CF 3 substituted carbene complexes 3-R have been characterized by multi-nuclear NMR spectroscopy as well as X-ray crystallography (for 3-Ph). The bonding situation was thoroughly assessed by computational means, showing stabilization of the electrophilic carbene center by π-donation from the aryl substituent and backdonation from Au, as enhanced by the chelating P^P ligand. Reactivity studies under stoichiometric and catalytic conditions substantiate typical carbene-type behavior for 3-Ph

On the versatile and unusual coordination behavior of ambiphilic ligands o-R2P(Ph)BR'2

International audienc

A Syn Outer-Sphere Oxidative Addition: The Reaction Mechanism in Pd/Senphos-Catalyzed Carboboration of 1,3-Enynes

We report a combined experimental and computational study of Pd/Senphos catalyzed carboboration of 1,3-enynes utilizing DFT calculations, 31P NMR study, kinetic study, Hammett analysis and Arrhenius/Eyring analysis. Our mechanistic study provides evidence against the conventional inner-sphere β-migratory insertion mechanism. Instead, a syn outer-sphere oxidative addition mechanism featuring a Pd-π-allyl intermediate followed by coordination-assisted rearrangements is consistent with all the experimental observations