tBu3P-Coordinated 2-Phenylaniline-Based Palladacycle Complex As Precatalyst for Pd-Catalyzed Coupling Reactions of Aryl Halides with Polyfluoroarenes via C-H Activation Strategy

Palladium-Catalyzed Homocoupling of Highly Fluorinated Arylboronates: Studies of the Influence of Strongly vs Weakly Coordinating Solvents on the Reductive Elimination Process

C-C reductive elimination from [PdL₂(C₆F₅)₂] to form polyfluorinated biaryls has been a challenge for over 50 years. Thus, palladium-catalyzed homocoupling of arylboronates (Ar_F-Bpin) containing two ortho-fluorine substituents is very difficult, as the reaction typically stops at the [PdL₂(Ar_F)₂] stage after two transmetalation steps. The transmetalated complexes cis-[Pd(MeCN)₂(C₆F₅)₂] (3a), cis-[Pd(MeCN)₂(2,4,6-C₆F₃H₂)₂] (3b), and cis-[Pd(MeCN)₂(2,6-C₆F₂H₃)₂] (3e) have been isolated from the reaction of Ar_F-Bpin with Pd(OAc)₂ in acetonitrile solvent, with no homocoupling observed. However, catalytic homocoupling proceeds smoothly in a "weakly coordinating" arene solvent as long as no ancillary ligands or coordinating solvents are present. DFT computations reveal that the active catalyst formed by arene solvent coordination leads to an overall reduced barrier for the reductive elimination step compared to the formation of stable [PdL₂(Ar_F)₂] complexes in the presence of a donor ligand or solvent L.

Promoting Difficult Carbon-Carbon Couplings: Which Ligand Does Best?

A Pd complex, cis-[Pd(C₆ F₅ )₂ (THF)₂ ] (1), is proposed as a useful touchstone for direct and simple experimental measurement of the relative ability of ancillary ligands to induce C-C coupling. Interestingly, 1 is also a good alternative to other precatalysts used to produce Pd⁰ L. Complex 1 ranks the coupling ability of some popular ligands in the order P^t Bu₃ >o-TolPEWO-F≈tBuXPhos>P(C₆ F₅ )₃ ≈PhPEWO-F>P(o-Tol)₃ ≈THF≈tBuBrettPhos≫Xantphos≈PhPEWO-H≫PPh₃ according to their initial coupling rates, whereas their efficiency, depending on competitive hydrolysis, is ranked tBuXPhos≈P^t Bu₃ ≈o-TolPEWO-F>PhPEWO-F>P(C₆ F₅ )₃ ≫tBuBrettPhos>THF≈P(o-Tol)₃ >Xantphos>PhPEWO-H≫PPh₃ . This "meter" also detects some other possible virtues or complications of ligands such as tBuXPhos or tBuBrettPhos.

t-Bu3P-Coordinated 2-Phenylaniline-Based Palladacycle Complex/ArBr as Robust Initiators for Controlled Pd(0)/t-Bu3P-Catalyzed Suzuki Cross-Coupling Polymerization of AB-Type Monomers

t-Bu₃P-coordinated 2-phenylaniline-based palladacycle complex (1) as the unique source of Pd(0)/t-Bu₃P to form efficient initiators with ArBr for controlled Suzuki cross-coupling polymerizations of AB-type monomers was described. The in situ generated initiators were demonstrated to be robust initiator systems for controlled Suzuki cross-coupling polymerization, affording polymers with unprecedentedly narrow PDIs and well-controlled functional end groups. ³¹P NMR study suggested that the fast and efficient generation of ArPd(t-Bu₃P)Br complexes from precatalyst 1 and ArBr might be the reason for better control of polymerization with precatalyst 1/ArBr as initiators. Our study provided a family of unprecedented, highly efficient initiators for controlled Suzuki cross-coupling polymerizations and a direct route to access conjugated polymers with a variety of heterobisfunctional chain end groups.

Reactivity of (poly)fluorobenzamides in palladium-catalysed direct arylations

Under PdCl₂/PivOK as reaction conditions, fluoro substituents act as better directing groups than amides in the palladium-catalysed direct arylations.

Accessing conjugated polymers with precisely controlled heterobisfunctional chain ends via post-polymerization modification of the OTf group and controlled Pd(0)/t-Bu3P-catalyzed Suzuki cross-coupling polymerization

Accessing of conjugated polymers with precisely controlled heterobisfunctional chain ends was achieved via the post-polymerization modification of the triflate (OTf) group.

C–H activation dependent Pd-catalyzed carbonylative coupling of (hetero)aryl bromides and polyfluoroarenes

The first intermolecular Pd-catalyzed carbonylative coupling of aryl bromides relying on C–H activation is presented.