Effect of Ligand Steric Properties and Halide Identity on the Mechanism for Oxidative Addition of Haloarenes to Trialkylphosphine Pd(0) Complexes

Abstract

The oxidative addition of PhX (X = I, Br, Cl) to the complexes Pd(P t Bu 3 ) 2 (1), Pd(1-AdP t Bu 2 ) 2 (2), Pd(CyP t Bu 2 ) 2 (3), and Pd(PCy 3 ) 2 (4) were studied to determine the effect of steric properties on the coordination number of the species that undergoes oxidative addition and to determine if the type of halide affects the identity of this species. The kinetic data imply that the number of phosphines coordinated to the complex that reacts in the irreversible step of the oxidative addition processes for complexes 1-4 depends on the halide more than the steric properties of the ligands. The rate-limiting step of the oxidative addition of PhI occurred with L 2 Pd (0) 3 . The irreversible step of the oxidative addition of PhCl occurred with a monophosphine species in each case, as signaled by an inverse dependence of the rate constant on the concentration of ligand. The irreversible step of the oxidative addition of PhBr occurred with a bisphosphine species, as signaled by the zeroth-order or small dependence of the rate constant on the concentration of phosphine. Thus, the additions of the less reactive chloroarenes occur through lower-coordinate intermediates than additions of the more reactive haloarenes.

Palladium-Catalyzed Cross-Coupling Reactions of Perfluoro Organic Compounds

“…On the other hand, in the presence of 4a, transmetalation between the transient iodopalladium(II) species and 4a took place smoothly to give the coupling product 13a. These assumptions are consistent with the results from Hartwig's kinetic studies wherein the oxidative addition of chlorobenzene to Pd(PCy 3 ) 2 , giving trans-(PCy 3 ) 2 Pd(Ph)(Cl), involved the dissociation process of a PCy 3 ligand at the initial stage of the reaction [102]. Unfortunately, any attempt to prepare the transient intermediate failed due to its coordinative unsaturation, and therefore, cis-(C 6 F 5 )Pd(I)(py)(PCy 3 ) (25), in which pyridine acts as a labile ligand to generate a tentative 3-coordinate (PCy 3 )Pd(C 6 F 5 )(I) species, was prepared as an alternative catalytic precursor.…”

Mediumeffekte in Palladium‐katalysierten Kreuzkupplungen und Implikationen bezüglich der katalytisch aktiven Spezies

“…[6,7] Experimentelle und theoretische mechanistische Studien deuteten an, dass eine einfach koordinierte Palladiumspezies der aktive Katalysator in Reaktionen mit Pd und PtBu 3 sei. [8][9][10][11][12] Außerdem demonstrierte Fu einen bemerkenswerten Ligandeneffekt in Pd-Kupplungen des Chloraryltriflats 1 (Schema 1). [7,13] PCy 3 führte zur Kupplung an der C-OTfBindung, PtBu 3 dagegen ausschließlich zur Reaktion an der C-Cl-Bindung.…”

Tetrachlorinated Polycyclic Aromatic Dicarboximides: New Electron‐Poor π‐Scaffolds and NIR Emitters by Palladium‐Catalyzed Annulation Reaction

“…In any conducted reaction the potential C−C cross‐coupling side reaction of substrate 1 a with the chlorine substituents of 2 was not observed, underlining the high tolerance of this Pd‐catalyzed C−C coupling reaction for chlorinated coupling components. Such selectivity of bromo over chloro halides in Suzuki–Miyaura cross‐coupling reactions is generally known …”