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'H₂) and 2‐cyclohexylaminomethyl‐4‐methylphenol (L″H₂), 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 (Me₅Al₃(L′)₂ ( 1 ) and Me₅Al₃(L″)₂ ( 2 )), monomeric aluminium (^t Bu₂Al(L'H) ( 3 ) and ^t Bu₂Al(L″H) ( 5 )) and gallium (^t Bu₂Ga(L'H) ( 4 ) and ^t Bu₂Ga(L″H) ( 6 )) compounds, and dinuclear gallium (Et₂Ga(L″H)·Et₃Ga ( 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.