Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: wildfyr on October 19, 2016, 06:12:42 PM
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Hey everyone,
Myself and former lab mates have had a shared frustration with inconsistency doing hydrosilations of ordinary terminal alkenes with ordinary silanes using Speiers and Karstedts' catalysts. Sometimes it works great, sometimes it goes to 10% and stops. We always suspected catalyst poisoning of some kind, but could never figure it out. I think I finally figured it out. It was the result of trying to do more and more careful hydrolsilations under inert atmosphere. In reality, hydrosilations of terminal alkenes need oxygen.
http://pubs.acs.org/doi/abs/10.1021/ja9825377
"The oxygen effect was first noted by Chalk and Harrod who reported that triethoxysilane and 1-alkenes did not react in the absence of air but reacted vigorously upon exposure to air using chloroplatinic acid as the catalyst."
My careful exclusion of air and correct shlenk technique wasted countless hours. Is this oxygen effect something that is well known that I (and lets be honest, my PI who taught me) just totally missed?