Density functional study on the reaction mechanism of palladium‐catalyzed addition of cyanoboranes to alkynes

Abstract

The B3LYP hybrid density functional method has been carried out to study theoretically the mechanism of Pd(0)-catalyzed alkyne cyanoboration reaction. Both the intermolecular and intramolecular alkyne cyanoboration reactions were studied. For each reaction, three paths were proposed. In path A of each reaction, the first step is B-CN bond oxidative addition to bisphosphine complex Pd(PH(3))(2), in path B of each reaction, the first step is alkyne coordination to bisphosphine complex Pd(PH(3))(2), and in path C of each reaction, the first step is the PH(3) dissociation from Pd(PH(3))(2) to form monophosphine complex Pd(PH(3)). For both reactions, path B is favored. The dissociation and recoordination of phosphine ligand are found to be very important for the entire reaction, in agreement with the experiment. In both intermolecular and intramolecular cyanoboration reactions, cyano migration is preferred to take place compared with alkenylboryl migration for the formation of the final cis products. The rate-determining step for both intermolecular and intramolecular cyanoboration reactions is found to be the insertion of carbon-carbon triple bond into Pd-B bond with the activation energy of 38.4 and 34.3 kcal/mol relative to the initial reactants, respectively. These values suggest that intramolecular reaction is relatively easy to occur.

Quantitative Structure–Activity Relationships for the Nucleophilicity of Trivalent Boron Compounds

“…For the electrophilic boryl–palladium complex [Pd(Bpin)Cl(PMe 3 ) 2 ] ( 12 ), the trend is inverted and the electrophilic path is kinetically favored over the nucleophilic path (Figure B). Previously, Wu and co‐workers had characterized computationally the mechanism for palladium‐catalyzed alkyne cyanoboration, the rate‐determining step of which was found to be the insertion of the C≡C triple bond into the Pd−B bond . In this case the formation of the key intermediate, [Pd(BX 2 )Cl(HCCH)(PH 3 )], involves one phosphine dissociation and the coordination of the π substrate.…”

“…Previously,W ua nd co-workersh ad characterized computationally the mechanism for palladium-catalyzeda lkyne cyanoboration, the rate-determining step of whichw as found to be the insertiono ft he CCt riple bond into the PdÀB bond. [30] In this case the formation of the keyi ntermediate, [Pd(BX 2 )Cl(HCCH)(PH 3 )],i nvolves one phosphine dissociation and the coordinationo ft he p substrate. Based on these findings we propose ad issociative mechanism involving the innersphere insertion of the substrate into the PdÀBb ond (Figure 4B).…”

Quantification of mutual trans influence of ligands in Pd(ii) complexes: a combined approach using isodesmic reactions and AIM analysis

“…3 Very often the trans influence has been invoked in organometallic chemistry to explain several reaction pathways. [13][14][15][16][17][18][19][20][21][22][23][24] This influence is not only significant in transition metal complexes and p-block metal compounds, 25-27 but also plays a major role in the stability of hypervalent aryl l 3 -iodanes. 28 Though a number of experimental studies are available, 6,8,29-31 theoretical investigations of trans influence 32-38 are comparatively less.…”

Dioxygen-Promoted Pd-Catalyzed Aminocarbonylation of Organoboronic Acids with Amines and CO: A Direct Approach to Tertiary Amides

“…Then, E is generated through transmetalation process of Pd species D with 1 . (3) Alternatively, the oxidative addition of arylboronic acids to Pd(0) produces F , which subsequently undergoes CO insertion and ligand exchange with amines to form intermediate C . Finally, the desired product 3 is produced via the reductive elimination of C and E .…”