In this paper we report the full characterization (solution-state NMR spectroscopy and solid-state structures) of a series of Al­(III) half-salan complexes and their exploitation for the ring-opening polymerization of rac-lactide. Depending on the ligand employed and stoichiometry of the complexation, structures of the form Al­(X)2Me or Al­(X)­Me2 were isolated. Interestingly Al­(2)2Me and Al­(2)­Me2 produce PLA with a strong isotactic bias (P m up to 0.80), whereas all other complexes produced atactic PLA. This is in contrast to recent studies on similar salan ligand systems. PLAs with predictable molecular weights and narrow distributions were achieved. The results are discussed in terms of steric and electronic properties of the ligands.

Controlling the microstructure of polymers through chemical reactivity is key to control the material properties of synthetic polymers. Herein we investigate the ring-opening copolymerization of a mixture of lactide and 2-ethyl-2-oxo-1,3,2-dioxaphospholane, promoted by an aluminum pyrrolidine monophenolate complex or 1,8-diazabicyclo[5.4.0]­undec-7-ene (DBU). This monomer mixture provides fast access to amphiphilic copolymers. The reaction conditions control the copolymer microstructure, which has been determined via a combination of 1H and 31P NMR spectroscopy. The choice of initiator has a profound impact: both initiators produce tapered block copolymers but with reverse monomer selectivity. While the aluminum initiator favors the cyclic phosphonate monomer, DBU favors lactide polymerization. Moreover, a sequential control of temperature facilitates the preparation of block copolymers in one pot. Thermal properties measured by TGA and DSC correlate to copolymer architectures. This methodology is the first report of copolymerization between cyclic phosphonates and lactide and opens the possibility to tune the thermal properties, solubility, and degradation rates of the resulting materials.

Herein the preparation and characterisation of a series of group 13 salan complexes, with a bipyrrolidine or N,N 0-ethylenediamine backbone are disclosed. For the bipyrrolidine derived-salan ligand 1H 2 , the Al(III) and Ga(III) complexes are pseudo trigonal bipyramidal in the solid-state, whereas the In(III) complexes are best described as square based pyramidal structures. However, for the ethylenediamine derived-salan ligand 2H 2 , all complexes are effectively square based pyramidal in their structure. The complexes' solution behaviour is also investigated by NMR spectroscopic methods and it is observed that the solid-state structure is maintained in solution. The complexes have all been trialled for the ring opening polymerisation of rac-lactide. With In(1)Cl controlled polymerisation and narrow molecular weight distributions (1.01-1.08) are observed with heterotactic polylactide being prepared. Under the conditions tested the Ga(III) and Al(III) complexes were shown to be inactive.

and revealed a dinuclear catalytically active species.

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]