Iron-catalyzed (E)-selective hydrosilylation of alkynes: scope and mechanistic insights

TitleIron-catalyzed (E)-selective hydrosilylation of alkynes: scope and mechanistic insights
Publication TypeJournal Article
Year of Publication2024
AuthorsSen, A, Tewari, T, Kumar, R, Vinod, CP, Sharma, H, Vanka, K, Chikkali, SH
JournalCatalysis Science and Technology
Volume14
Issue10
Date PublishedMAY
Type of ArticleArticle
ISSN2044-4753
Abstract

Iron-catalyzed hydrosilylation of internal alkynes has been rarely reported. Even in these rare cases, additives have been used for the success of the reaction, which often creates a problem for the functional group tolerance of the reaction. Herein, we report an additive-free iron-catalyzed (E)-selective hydrosilylation of internal alkynes in the presence of a phosphine ligand. A low-valent Fe(0) complex [Fe(CO)(3)(BDA)] {[Fe-1]} catalyzed the hydrosilylation of alkynes at 60 to 120 degrees C, exhibited a broad substrate (24 substrates) scope and tolerated different functional groups. The synthetic utility of the reaction was demonstrated by a gram scale experiment, preparing alkenes, and by chemo-selective hydrosilylation. The modus operandi of the reaction has been investigated by i) homogeneity test, ii) radical trapping experiments, iii) X-ray photoelectron spectroscopy, and iv) by preparing a Fe(II) complex as catalyst control. These mechanistic investigations revealed a two-electron pathway for the hydrosilylation of alkynes. In addition, kinetic investigations were undertaken to shed light on the rates of the reaction. Kinetic studies suggest the absence of an induction period, and the reaction is first order with respect to the concentration of iron catalyst [Fe-1] and zeroth order with respect to the substrate (alkyne). The Hammett plot suggests that strongly electron-withdrawing groups on the alkyne favour the hydrosilylation reaction. Meanwhile Eyring analysis suggests that the rate-determining step likely involves an associative pathway. Based on the findings of the mechanistic and kinetic investigation, a plausible Chalk-Harrod-type mechanism is likely to be operative. The proposed mechanism is substantiated by computational investigations, which suggested that the Chalk-Harrod mechanism is kinetically more favored by 15.8 kcal mol(-1) over the modified Chalk-Harrod mechanism.

DOI10.1039/d3cy01775c
Type of Journal (Indian or Foreign)

Foreign

Impact Factor (IF)

5

Divison category: 
Catalysis and Inorganic Chemistry
Physical and Materials Chemistry
Polymer Science & Engineering
Database: 
Web of Science (WoS)

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