Oxidative Additions of Aryl Halides to Palladium Proceed through the Monoligated Complex

Abstract

Palladium(0) complexes facilitate many catalytic transformations that begin with the oxidative addition of a halobenzene. The ligation state of the palladium during this reaction is a vexing issue, owing to the inherent difficulty of isolating reactive, coordinatively unsaturated metal complexes. By isolating them in the gas phase in an ion‐trap mass spectrometer, the reactivity of mono‐ and bisligated palladium complexes can be directly compared, and the former proved to be several orders of magnitude more reactive towards halobenzenes. Calculations of barrier heights for the oxidative addition led to additional experiments, which demonstrated that although the reaction proceeded to completion for iodobenzene, the reaction was slower for bromobenzene and progressed only as far as an ion–molecule adduct for chloro‐ and fluorobenzene.

Spatial effects on electrospray ionization response

“…In particular, we were interested in differential effects, that is, where moving the spray head affected one signal more than another. Electrospray ionization has become increasingly popular as an investigatory tool in the study of reaction mechanisms [8,9] and its explorative capacity may be strengthened with a greater knowledge of instrument response with respect to the position of the capillary spray head, along with other experimentally-controlled conditions. In particular, it is important for reproducibility purposes across different concentration ranges that we are not perturbing the relative response of different ions, because such effects may provide misleading kinetic data.…”

Palladium‐Catalyzed Direct C2‐Arylation of an N‐Heterocyclic Carbene: An Atom‐Economic Route to Mesoionic Carbene Ligands

“…[26,27] At elevated temperature, [(LPd) 2 (dba)] generates a catalytically active monoligated L-Pd 0 species, which readily undergoes oxidative addition with an aryl halide. [28,29] Therefore, formation of [ (IPrPd) . [21] To examine the validity of the proposed cycle (Scheme 3), catalytic activity of the bis-NHC-Pd 0 compound [(IPr) 2 Pd] (11), [30] prepared by the treatment of a THF solution of [(IPr) 2 PdCl 2 ] with KC 8 , was tested.…”

Alkylation of [Pt2(μ-S)2(PPh3)4] with boronic acid derivatives

“…An overpressure of 2 -4 psi is applied displacing the reacting solution into the MS. This allows for real-time observation of all charged species and how they behave over the course of the reaction, [31][32][33][34] and providing a better understanding of mechanism and optimization of synthetic protocols. For this report speciation and dynamic behavior in the reaction of 1 with 4-(bromomethyl)phenylboronic acid pinacol ester, BrCH2(C6H4)B{OC(CH3)2}2, 2 was monitored.…”