Titanium complexes based on aminodiol ligands for the ring-opening polymerization of ε-caprolactone, rac-β-butyrolactone, and trimethylene carbonate

Titanium and Vanadium Complexes of Tridentate Phenoxy-Imine and Phenoxy-Amine Ligands and Their Application in the Ring-Opening Polymerization of Cyclic Esters

Phenoxy-imine and phenoxy-amine proligands, with the additional OH donor groups 2,4-tBu2-6-(2-CH2(OH)-C6H4N=CH)C6H3OH (L1H2), 6-(2-CH2(OH)-C6H4N=CH)C6H3OH (L2H2), and 2,4-tBu2-6-(2-CH2(OH)-C6H4NH-CH)C6H3OH (L3H2), were synthesized and their titanium (Ti-L1-Ti-L3) and vanadium (V-L1-V-L2) complexes were prepared in reactions with Ti(OiPr)4 and VO(OiPr)3, respectively. All new compounds were characterized with the use of FTIR, 1H, and 13C NMR spectroscopy; X-ray crystallography was also used to study proligands. All the complexes proved to be active catalysts in the ring-opening polymerization (ROP) of ε-caprolactone, rac-lactide, and L-lactide in the melt. The effects of the complex structure (transition metal type, presence of tBu substituents, and type of nitrogen donor group), as well as the polymerization time and temperature, on the monomer conversion and polymer properties were investigated in detail.

Living ring-opening polymerization of β-butyrolactone initiated by mononuclear zirconium compounds containing sterically hindered N,O-chelate and anionic dimethylamide ligands†

The ring-opening polymerization of β-lactones into polyhydroxyalkanoates (PHA), biodegradable polymers with high molecular weight and narrow polydispersity, is of significant interest. The mononuclear zirconium compound containing sterically hindered N,O-chelate and anionic dimethylamide ligands was used as an initiator for the polymerization of β-butyrolactone (BBL), resulting in polyhydroxylbutyrate (PHB) with a number-average molecular weight of 12 000 g mol⁻¹. Kinetic studies demonstrate a first-order dependence on β-butyrolactone (BBL) concentration at room temperature, accompanied by narrow molecular weight distributions (ca. 1.03–1.07), indicating a well-controlled living polymerization.

The ring-opening polymerization of β-lactones into polyhydroxyalkanoates (PHA), biodegradable polymers with high molecular weight and narrow polydispersity, is of significant interest.

Ring opening polymerization of ε-caprolactone initiated by titanium and vanadium complexes of ONO-type schiff base ligand

A phenoxy-imine proligand with the additional OH donor group, 4,6-tBu2-2-(2-CH2(OH)-C6H4N = CH)C6H3OH (LH2), was synthesized and used to prepare group 4 and 5 complexes by reacting with Ti(OiPr)4 (LTi) and VO(OiPr)3 (LV). All new compounds were characterized by the FTIR, 1H and 13C NMR spectroscopy and LTi by the single-crystal X-ray diffraction analysis. The complexes were used as catalysts in the ring opening polymerization of ε-caprolactone. The influence of monomer/transition metal molar ratio, reaction time, polymerization temperature as well as complex type was investigated in detail. The complexes showed high (LTi) and moderate (LV) activity in ε-caprolactone polymerization and the resultant polycaprolactones exhibited Mn and Mw/Mn values ranging from 4.0 · 103 to 18.7 · 103 g/mol and from 1.4 to 2.5, respectively.

Magnesium and aluminum complexes bearing bis(5,6,7-trihydro quinolyl)-fused benzodiazepines for ε-caprolactone polymerization

New bis(5,6,7-trihydroquinolyl)-fused benzodiazepine ligands were synthesized and used to form dinuclear magnesium and aluminum complexes which showed efficient catalytic activity toward the ROP of ε-CL.

Titanium pyridonates for the homo- and copolymerization of rac-lactide and ε-caprolactone

A series of titanium pyridonate complexes have been synthesized under very mild reaction conditions from a common precursor, Ti(NMe₂)₄. These complexes have been explored as initiators for the ring-opening polymerization of rac-lactide and ε-caprolactone and have proven to be competitive with leading titanium initiators.

Synthesis and characterization of bimetallic lanthanide-alkali metal complexes stabilized by aminophenoxy ligands and their catalytic activity for the polymerization of 2,2-dimethyltrimethylene carbonate

Electronic properties of the aminophenolate groups have obvious effect on the synthesis of aminophenolate lanthanide-lithium complexes. Amine elimination reactions of Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 with lithium aminophenolates [ArNHCH2(3,5-(t)Bu2C6H2-2-O)Li(THF)]2 (Ar = p-ClC6H4, [ONH](Cl-p); p-BrC6H4, [ONH](Br-p)) in tetrahydrofuran (THF) in a 1 : 2 molar ratio gave the bimetallic lanthanide-lithium amido complexes [NO](Cl-p)2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (1), Yb (2)), and [NO](Br-p)2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (3), Yb (4)). When the Ar groups are p-MeOC6H4, ([ONH](MeO-p)) and o-MeOC6H4 ([ONH](MeO-o)), similar reactions generated the homoleptic lanthanide-lithium complexes [NO](MeO-p)3Ln[Li(THF)]3 (Ln = Y (5), Yb (6)) and [NO](MeO-o)2Ln[Li(THF)] (Ln = Y (7), Yb (8)) in high isolated yields, respectively. Whereas the bimetallic lanthanide-lithium amido complexes [NO](Cl-o)2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (9), Yb (10)) can be obtained in good yields, when the Ar group is o-ClC6H4 ([ONH](Cl-o)). All of these complexes were well characterized. X-ray structure determination revealed that these complexes have solvated monomeric structures. In complexes 1-4, 9, and 10, the lanthanide atom is five-coordinated by two oxygen atoms and two nitrogen atoms from two aminophenoxy ligands and one nitrogen atom from N(SiMe3)2 group to form a distorted trigonal bipyramidal geometry, whereas in complexes 5-8, the central lanthanide atom is six-coordinated by oxygen atoms, and nitrogen atoms from the aminophenoxy ligands to form a distorted octahedron. It was found that complexes 1-10 are highly efficient initiators for the ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC), affording the polymers with high molecular weights, and the homoleptic heterobimetallic lanthanide complexes showed apparently high activity.