Reactions of Rare‐Earth Metal Based Lewis Pairs with Azides†

Abstract

Summary of main observation and conclusionThe reactivity of homoleptic rare‐earth metal aryloxide based Lewis pairs toward organic azide substrates has been investigated herein. Treatment of RE(OAr)3 (RE = La, Sm, Y, and Sc, Ar = 2,6‐tBu2‐C6H3), PEt3 and Me3SiN3 in 2 : 1 : 1 molar ratio resulted in formation of separated ion pair complexes [Me3Si‐PEt3]+[(ArO)3RE‐N=N=N‐RE(OAr)3]– under mild conditions. Replacement of phosphine with the nitrogen‐containing Lewis base 1,4‐diazabicyclo[2.2.2]octane (DABCO) produced analogous rare‐earth azide complexes with [Me3Si‐DABCO]+ counterions. In contrast, reaction of the La(OAr)3/PEt3 Lewis pair with 1‐adamantyl azide (AdN3) afforded the typical frustrated Lewis pair‐type 1,1‐addition product. A tetrahydrofuran ring‐opening reaction was also observed for the resulting rare‐earth azide complex with the [Me3Si‐PEt3]+ cation, with cleavage of the C—O bond by Si/P cooperation.