Salalens and Salans Derived from 3‐Aminopyrrolidine: Aluminium Complexation and Lactide Polymerisation

Abstract

In this paper a series of 7 salalen ligands based on an aminopyrrolidine backbone have been prepared and characterised. Several systems have been reduced to the salan ONNO type-ligand. All ligands have been complexed to Al III with Al-(1-7)Me, Al(2a)(OiPr) and Al(7a)Me being characterised by single-crystal X-ray diffraction. In general the Al III centres are best described as being in a trigonal bipyramidal geometry. The solution and solid-state structures are discussed. All complexes [a]

Phosphasalalen Rare-Earth Complexes for the Polymerization of rac-Lactide and rac-β-Butyrolactone

“…Salalens (Figure C), combining half salen (Figure A) and half salan (Figure B) pro-ligands in a hybrid mold, are [ONNO]-type tetradentate pro-ligands that include imine- and amine-neutral donors and two phenolate arms. Their corresponding metal complexes have been used successfully in the polymerization of diverse monomers, such as the stereoselective ROP of rac -LA, the copolymerization of epoxides with carbon dioxide, and the isospecific polymerization of α-olefin. − Surprisingly, heteroatomic substitutions on the backbone of salalen pro-ligands have been less investigated; only a few sulfur-subsituted pro-ligands were reported, and in some the sulfur atom did not coordinate to the metal centers . On the other hand, the iminophosphorane moieties behave as strong σ- and π-donors due to the presence of two lone pairs at the nitrogen atom and the lack of π-accepting ability, respectively.…”