Mechanistic study on the coupling reaction of aryl bromides with arylboronic acids catalyzed by (iminophosphine)palladium(0) complexes. Detection of a palladium(ii) intermediate with a coordinated boron anion

Abstract

3 and activated olefins (ol = dmfu, fn), the latter compounds react with an excess of 4-R 2 C 6 H 4 B(OH) 2 (R 2 = H, Me, OMe, Cl) to give [Pd(g 2 -ol)(P-N)] and the corresponding biaryl through transmetallation and fast reductive elimination. The transmetallation proceeds via a palladium(II) intermediate with an O-bonded boron anion, the formation of which is markedly retarded by increasing the bulkiness of R. The intermediate was isolated for R = CHMe 2 , R 1 = CF 3 and R 2 = H. The boron anion is formulated as a diphenylborinate anion associated with phenylboronic acid and/or as a phenylboronate anion associated with diphenylborinic acid. In general, the oxidative addition proceeds at a lower rate than transmetallation and represents the rate-determining-step in the coupling reaction of aryl bromides with arylboronic acids catalyzed by [Pd(g 2 -dmfu)(P-N)].

A Bis(Boronic Ester)-Based Fluorogenic and Chromogenic Sensor for F-and Cu2+

“…The sharp peak that is observed in the most up‐field region at 4.10 ppm can be assigned as for –OCH 2 groups. 11 B NMR spectrum exhibits twobroad signals at 29.1 and−5.6 ppm for tri and tetravalent boron, respectively(Figure S1, Supporting Information) . Due to presence of boronate ester moiety, the Lewis acidity of the boron atom increased and strongly interacts with DMSO‐ d 6 solvent molecule and ultimately gives rise to the formation of tetravalent boron.…”

Role of the base and endogenous anions in “ligand-free” catalytic systems for the Suzuki–Miyaura reaction

“…Evidence in favor of the interaction of neutral molecules of phenylbo ronic acid with palladium-base anion complexes at the transmetalation stage (II) is provided by results of detailed kinetic studies [11][12][13][14], including those in which the substrate was enriched with a heavy isotope [15]. Until recently, the involvement of arylboronate anions in the transmetalation stage (reaction (III)) has been mainly proved by quantum chemical calculations [16][17][18]. However, the results of investigation of the Suzuki-Miyaura reaction under conditions of two arylboronic acids competing with one another were published in 2014, and these results are consistent with the opinion that arylboronate anions participate in the transmetalation process [19].…”

Synthesis and Characterization of Tantalum(V) Boronate Clusters: Multifunctional Lewis Acid Cages for Binding Guests

“…A major advantage of boronic acids is their widespread commercial availability, which allows R to be easily modified to vary the steric and electronic properties. Few aryl boronate complexes of transition metals have been reported previously, and they are limited to zirconium, [14] manganese, [15] copper, [16] rhodium, [17] palladium, [18] and platinum. [19] Group 9 and 10 boronate complexes are transient species in Suzuki-Miyaura coupling reactions, and the structural features of the other boronate metal complexes reveal a tendency for aryl boronates to bridge transition metals in a fashion similar to that of their close carbon analogues, carboxylates.…”