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

Summary of main observation and conclusion The 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‐ t Bu 2 ‐C 6 H 3 ), PEt 3 and Me 3 SiN 3 in 2 : 1 : 1 molar ratio resulted in formation of separated ion pair complexes [Me 3 Si‐PEt 3 ] + [(ArO) 3 RE‐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 [Me 3 Si‐DABCO] + counterions. In contrast, reaction of the La(OAr) 3 /PEt 3 Lewis pair with 1‐adamantyl azide (AdN 3 ) 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 [Me 3 Si‐PEt 3 ] + cation, with cleavage of the C—O bond by Si/P cooperation.