Aminophenolates of aluminium, gallium and zinc: Synthesis, characterization and polymerization activity

Complexes containing aminophenolate ligands are considered as very efficient initiators of ring‐opening polymerization (ROP). Our systematic studies of the reactions of two selected aminophenols, 2‐[( p ‐tolylamino)methyl]‐4‐(2,4,4‐trimethylpentan‐2‐yl)phenol (L'H 2 ) and 2‐cyclohexylaminomethyl‐4‐methylphenol (L″H 2 ), with alkyl compounds of aluminium, gallium and zinc resulted in the formation of a variety of products depending on the type of metallic centre and alkyl groups bonded to metal atoms. New trinuclear aluminium complexes (Me 5 Al 3 (L′) 2 ( 1 ) and Me 5 Al 3 (L″) 2 ( 2 )), monomeric aluminium ( t Bu 2 Al(L'H) ( 3 ) and t Bu 2 Al(L″H) ( 5 )) and gallium ( t Bu 2 Ga(L'H) ( 4 ) and t Bu 2 Ga(L″H) ( 6 )) compounds, and dinuclear gallium (Et 2 Ga(L″H)·Et 3 Ga ( 7 )) and zinc ( t BuZn(L″H)] 2 ( 8 )) complexes were isolated and characterized. The molecular and crystal structures of 7 and 8 were determined on the basis of an X‐ray diffraction study. Polymerization tests showed that only three complexes ( 6 – 8 ) had activity in the ROP of ε ‐caprolactone, whereas 1 – 5 were inactive in ROP.