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-Bu-t(2)-C6H3), PEt3 and Me3SiN3 in 2 : 1 : 1 molar ratio resulted in formation of separated ion pair complexes [Me3Si-PEt3](+)[(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 [Me3Si-DABCO](+) counterions. In contrast, reaction of the La(OAr)(3)/PEt3 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 [Me3Si-PEt3](+) cation, with cleavage of the C-O bond by Si/P cooperation.