Careful investigation of the hydrosilylation of olefins at poly(ethylene glycol) chain ends and development of a new silyl hydride to avoid side reactions

Abstract

Hydrosilylation of olefin groups at poly(ethylene glycol) chain ends catalyzed by Karstedt catalyst often results in undesired side reactions such as olefin isomerization, hydrogenation, and dehydrosilylation. Since unwanted polymers obtained by side reactions deteriorate the quality of end‐functional polymers, maximizing the hydrosilylation efficiency at polymer chain ends becomes crucial. After careful investigation of the factors that govern side reactions under various conditions, it was related that the short lifetime of the unstable Pt catalyst intermediate led to the formation of more side products under the inherently dilute conditions for polymers. Based on these results, two new chelating hydrosilylation reagents, tris(2‐methoxyethoxy)silane (5) and 2,10‐dimethyl‐3,6,9‐trioxa‐2,10‐disilaundecane (6), have been developed. It was demonstrated that the hydrosilylation efficiency at polymer chain ends was significantly increased by employing the internally coordinating hydrosilane 5. In addition, employment of the internally coordinating disilane species 6 in an addition polymerization with 1,5‐hexadiene by hydrosilylation reaction yielded a polymer with high molecular weight (Mn = 9300 g/mol), which was significantly higher than that (Mn = 2600 g/mol) of the corresponding polymer obtained with non‐chelating dihydrosilane, 1,1,3,3‐tetramethyldisiloxane. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 527–536

Photoinduced hydrosilylation through hydrogen abstraction: an NMR and computational study of the structural effect of silane

“…7d ) arising from the coupling of the triphenylsilyl radical with the double bond. 20,21 The signals at 0.57 ppm and 1.36 ppm of the 1 H NMR spectrum can be assigned to the protons located at the f and g positions of the product, as shown in Scheme 3 .…”

The iterative synthesis of discrete dimethylsiloxane oligomers: A practical guide

“…Although Karstedt's catalyst provides a robust synthetic route toward the hydrosilylation product, side reactions can occur (Figure 4A). Factors governing the byproduct formation are carefully investigated by Moon and coworkers 36 . They described a second catalytic cycle, which leads to isomerized substrate.…”

Iridium-Catalyzed Hydrosilylation of Polymeric Olefins: Moving beyond Platinum-Based Catalysts for Surfactants

“…22 Additionally, Karasiewicz et al employed Karstedt's catalyst, 14 and Shin et al provided an in-depth approach in explicating the difficulties of platinic systems and how to circumvent side reactions that arise. 23 Hydrosilylation of unsaturated compounds is not limited to platinum as other approaches to prepare organosilicon compounds have been utilized. 24−29 To effectively move beyond fluorocarbon surfactants in AFFF formulations and incorporate siloxane surfactant chemistries as an alternative, new synthetic approaches and catalyst development are necessary.…”

“…Inomata et al utilized a ruthenium catalyst under neat conditions to generate the desired hydrosilylated products . Additionally, Karasiewicz et al employed Karstedt’s catalyst, and Shin et al provided an in-depth approach in explicating the difficulties of platinic systems and how to circumvent side reactions that arise . Hydrosilylation of unsaturated compounds is not limited to platinum as other approaches to prepare organosilicon compounds have been utilized. − …”