Group 4 metal complexes containing the salalen ligands: Synthesis, structural characterization and studies on the ROP of cyclic esters

Publication date: Available online 23 March 2018Source: Journal of Organometallic ChemistryAuthor(s): Debashis Chakraborty, Bijja Rajashekhar, Mrinmay Mandal, Venkatachalam RamkumarAbstractThe synthesis of homoleptic salalen ligand supported group 4 complexes and their applications in the ring-opening polymerization (ROP) of ε-caprolactone (ɛ-CL) and lactide (LA) are described. All these complexes of type M(L)2 (LH = (E)-N-(2-(3,5-dibromo-2-hydroxybenzylideneamino)phenyl)-4-methylbenzenesulfonamide: M = Ti (1), M = Zr (4), M = Hf (7); LH = (E)-N-(2-(2-hydroxybenzylideneamino)phenyl)-4-methylbenzenesulfonamide: M = Ti (2), M = Zr (5), M = Hf (8); LH = (E)-N-(2-(3,5-di-t-butyl-2-hydroxybenzylideneamino)phenyl)-4-methylbenzenesulfonamide: M = Ti (3), M = Zr (6), M = Hf (9)) are characterized by various spectroscopic techniques. The single crystal X-ray diffraction analysis confirmed that the metal centers in complexes 6 and 8 adopt distorted dodecahedral geometry. The self-assembly of the complexes in solid state through the molecular interactions demonstrated that the supramolecular network forms molecular channels which act as a host lattice for the assembly of toluene solvent molecules. Complexes (1–9) are effective catalysts for the ROP of ɛ-CL and LA and produced high molecular weight (Mn) polycaprolactone (PCL) and poly (lactic acid) (PLA) respectively with narrow molecular weight distributions (MWDs) in the range of 1.17–1.28. PL...

Source: Journal of Organometallic Chemistry - July 11, 2018 Category: Chemistry Source Type: research