The mechanism of transition metal catalyzed carbonylation of allyl halides: A theoretical investigation

Mechanistic Investigation of the Nickel-Catalyzed Carbonylation of Alcohols

“…Both the activation barriers for equivalent mechanistic scenarios based on systems with zero (three CO ligands) or two TBP ligands are higher in energy (see Schemes S3−S6 in Supporting Information). The reaction proceeds from Ni(CO) 2 (TBP) 2 (A) via phosphine dissociation and formation of the R−I adduct B (ΔG 393 = 114.0 kJ mol −1 ), which has also been computationally studied by other groups for Ni 42,43 and Pd 53 complexes. B is assumed to undergo barrierless homolytic cleavage of the R−I bond to yield the Ni(I) complex C and the corresponding phenylethyl radical (ΔG 393 = 73.7 kJ mol −1 ).…”

“…Similarly high two-electron oxidative addition barriers have been reported by Bottoni et al, which investigated the formation of β,γunsaturated acyl derivatives via a Ni(0)/Ni(II) pathway. 42,43 These considerations were also transferred to the depe ligand (1,2-bis(diethylphosphino)ethane), which was used as a model for the barely active dppe ligand (1,2-bis(diphenylphosphino)ethane). The calculated activation barrier of the rate- determining step was found to be significantly higher than the ones of the previous systems (ΔG ⧧ = 156.1 kJ mol −1 ), and the strong dependence on the length of the ligand's backbone observed experimentally was also probed and similarly observed computationally (see Supporting Information).…”

“…To further understand the underlying processes, a detailed investigation of the reaction mechanism was carried out on the basis of density functional theory (see Supporting Information for details). Mechanistic pathways via two one-electron steps have been computationally evaluated in previous publications, mainly focusing on a variety of alkyl–alkyl coupling reactions. ,,,− Comparable mechanisms have been proposed for the carbonylation of alkyl iodides with palladium, where the single-electron transfer (SET) is initiated photocatalytically. The subsequent reaction steps are very similar to those proposed for nickel and considered for the system presented here. , The involvement of alkyl radicals generated by SET from the corresponding alkyl halides in Ni-catalyzed reactions has been suggested by different research groups. ,− However, to the best of our knowledge, an in-depth comparison between oxidative addition/reductive elimination and potential radical pathways has not been carried out yet.…”

Mechanistic Origin of Cross‐Coupling Selectivity in Ni‐Catalysed Tishchenko Reactions

“…[21] The geometry optimization of all species in this study is performed with the hybrid Becke3 LYP (B3LYP) functional, [22] which has been used in recent mechanistic studies on Ni-catalysed reactions. [23] The standard Pople allelectron basis set of 6-31G(d) was used for C, H, O, N and Cl atoms, while the effective core potentials (ECPs) of Hay and Wadt with a double-valence basis set (Lanl2DZ) was used for the Ni atom. [24] Frequency calculations at the same level of theory were performed to identify the number of imaginary frequencies (zero for local minimum and one for transition states) and provide the thermal corrections of Gibbs free energy.…”

DFT investigations for the reaction mechanism of dimethyl carbonate synthesis on Pd(ii)/β zeolites

“…Bell and co-workers have systemically studied the kinetics of DMC formation on a well characterized Cu-Y sample prepared by dry exchange of H-Y with CuCl. 17,18 They pointed out that when carbon monoxide is present in the gas phase, the methoxide species reacts slowly to form monomethyl carbonate (MMC) 25 rather than carbonmethoxide (CH 3 OCO-) as proposed by King. 21,22 Engeldinger et al also conformed the formation of a MMC intermediate using the simultaneous combination of steady state isotopic transient kinetic analysis (SSITKA).…”