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Density functional theory (DFT) calculation has been used to reveal the mechanism of the Pd-catalyzed disilylation reaction of aryl halides. The DFT calculations indicate that the reaction starts with the oxidative addition of the C–I bond to the Pd(0) catalyst. Concerted metalation–deprotonation (CMD) can then generate a five-membered palladacycle. Insertion of Pd(II) into the Si–Si bond in disilane followed by two sequential steps of reductive eliminations yields the disilylation product and regenerates the Pd(0) catalyst. According to the NPA charge analysis along the reaction coordinates, the formal oxidative addition of the Si–Si bond to palladium could be considered as the insertion of palladium into the Si–Si bond. However, the conventional oxidative addition of the C–I bond to palladium is exactly an oxidation process with the electron transfer from the palladium atom to the C–I bond. Therefore, electron rich Pd(0) is beneficial for the oxidation process, and Pd(II) prone to acquire electrons is beneficial for the insertion process. [ABSTRACT FROM AUTHOR]

Employing the oxidative coupling of phenylacetylene with benzaldehyde as a model reaction, a density functional theory (DFT) study combined with extended X-ray absorption fine structure (EXAFS) experiment was carried out to reveal the difference between dinuclear and mononuclear zinc mediated nucleophilic addition. Newly reported DFT method M11-L computed results suggest that the mononuclear zinc mediated pathway, in which nucleophilic addition occurs via a four-membered ring transition state, is unfavourable both thermodynamically and kinetically. The dinuclear zinc mechanism, which appropriately explains the experimental observations, involves a six-membered ring transition state for nucleophilic addition. Subsequent in situ EXAFS experiment confirmed the existence of dinuclear zinc active species. Moreover, frontier molecular orbital (FMO) analysis and distortion–interaction energy analysis along the whole reaction pathways have provided interpretations for the advantage of dinuclear zinc mediated nucleophilic addition. Consequently, we believe this dinuclear zinc pathway will open up a general consideration of the dinuclear zinc mechanism for nucleophilic additions. [ABSTRACT FROM AUTHOR]