Reaction mechanism of palladium‐catalyzed silastannation of allenes by density functional theory

Abstract

The reaction mechanism of Pd(0)-catalyzed allenes silastannation reaction is investigated by the density functional method B3LYP. The overall reaction mechanism is examined. For the allene insertion step, the Pd-Si bond is preferred over the Pd-Sn bond. The electronic mechanism of the allene insertion into Pd-Si bond to form sigma-vinylpalladium (terminal-insertion) and sigma-allylpalladium (internal-insertion) insertion products is discussed in terms of the electron donation and back-donation. It is found that the electron back-donation is significant for both terminal- and internal-insertion. During allene insertion into Pd-Si bond, internal-insertion is preferred over terminal-insertion. By using methylallene, the regio-selectivity for the monosubstituted allene insertion into Pd-Si and Pd-Sn bond is analyzed.

Allenes and computational chemistry: from bonding situations to reaction mechanisms

“…128 Based on the theoretical studies on the Pd(0)-catalysed allene silaboration 125 and alkyne silastannation, 131 (Scheme 15). 132 The results suggested that the reaction pathway proceeds via (a) oxidative addition of Si-Sn to Pd(PH 3 ) 2 , (b) dissociation to form complex 89, (c) allene coordination and insertion into the Pd-Si bond, (d) isomerization from s-allyl 90 to p-allyl complex 91, and (e) reductive elimination to give the final product Z-93. The rate-determining step is the allene insertion into the Pd-Si bond.…”

DFT-Based Insights into Pd–Zn Cooperative Effects in Oxidative Addition and Reductive Elimination Processes Relevant to Negishi Cross-Couplings

“…Similarly, in a DFT study on Me–Me couplings a similar interaction was reported at the transmetalation TS . Support for the viability of such metal–metal-bonded bimetallic species is found in one particular example of an isolated complex with a Ni–Al bond, where X-ray data have revealed a structural arrangement with bridging methyl and oxy groups, which would actually be a model for a transmetalation event. , Perhaps not surprisingly, dinuclear complexes with metal–metal bonds have been shown to be active in catalysis. ,− …”

Mechanism of methylacetylene bisselenation catalyzed by palladium complex from density functional study

“…2), and reductive elimination can proceed through two pathways, i.e., monophosphine and bisphosphine pathway (Fig. 4), the reductive elimination prefers to proceed through the monophosphine pathway 3Ba?TS 34 ?4?6, similar to the palladium-catalyzed allenes bisselenation 48 and silastannation 60 reactions, in which the reductive elimination prefers the monophosphine pathway. In monophosphine pathway, the reductive elimination takes place directly through the transition state TS 34 to form complex 4.…”

“…As transition state TS 56 is 1.9 kcal/mol higher than TS 34 (Fig. 4), the reductive elimination prefers to proceed through the monophosphine pathway 3Ba?TS 34 ?4?6, similar to the palladium-catalyzed allenes bisselenation 48 and silastannation 60 reactions, in which the reductive elimination prefers the monophosphine pathway.…”

“…Lowest unoccupied molecular orbital (LUMO) is mainly the empty d orbital of Pd atom for both 1A and 1B. For methylacetylene, only the in-plane p and p* orbitals are considered to interact with 1A and 1B, whereas the out-of-plane p and p* orbitals are ignored, as they have less influence on the insertion into PdÀ ÀSe as in the theoretical studies of alkynes insertion into PdÀ ÀSn bond 60 of Pd(PH 3 )(SiH 3 )(SnH 3 ) and into PdÀ ÀS bond 49 of Pd(SH)(CN)(PH 3 ).…”