Group 4 metal complexes of Trost's semi-crown ligand: synthesis, structural characterization and studies on the ring-opening polymerization of lactides and ε-caprolactone
| Autor: | Bijja Rajashekhar, Debashis Chakraborty, Sagnik K. Roymuhury, Venkatachalam Ramkumar |
|---|---|
| Rok vydání: | 2015 |
| Předmět: |
X-ray diffraction studies
Magnetic Resonance Spectroscopy Polymers Molecular Conformation Crystal atomic structure Zirconium compounds Ring opening polymerization Crystallography X-Ray Ligands Photochemistry Molecular weight Ring-opening polymerization Polymerization Dioxanes Lactones chemistry.chemical_compound Coordination Complexes Well drilling Titanium Crowns Chelation Chemistry Organic polymers Structural characterization Trigonal bipyramidal molecular geometry Monomer Metals Synthesis (chemical) Orthorhombic crystal system Caprolactone Single-crystal X-ray diffraction studies X ray diffraction Group 4 metal complexes Molecular weight distribution Inorganic Chemistry Metal complexes Octahedral molecular geometry Caproates Coordination insertion mechanism High-molecular weight polymers Mass spectrometry Ligand Crystallography Narrow molecular weight distributions Spectrometry Mass Matrix-Assisted Laser Desorption-Ionization Single crystals Quantum Theory Zirconium Hafnium |
| Zdroj: | Dalton Transactions. 44:16280-16293 |
| ISSN: | 1477-9234 1477-9226 |
| DOI: | 10.1039/c5dt02267c |
| Popis: | The synthesis of titanium(iv), zirconium(iv) and hafnium(iv) complexes of Trost's semi-crown ligand is described. All complexes were fully characterized by 1H and 13C NMR and mass spectroscopy. The molecular structures of the representative complexes 2, 3 and 4 were determined by single-crystal X-ray diffraction studies. The X-ray diffraction studies reveal that complexes 2, 3 and 4 crystallized in an orthorhombic crystal system. Complexes 2 and 3 have a monomeric structure in the solid state with distorted octahedral geometry around the metal center, whereas complex 4 was found to crystallize in a trimeric structure bridging with an oxygen atom, where the geometry around the titanium is distorted trigonal bipyramidal. The activities and stereoselectivities of these complexes toward the ring-opening polymerization (ROP) of lactides (l-LA and rac-LA) and ?-caprolactone (CL) have been investigated. Complexes 1-4 were found to be efficient single-component initiators for the ring-opening polymerization of cyclic esters and yielded high molecular weight polymers (Mn) with narrow molecular weight distributions (MWD).The microstructure of the resultant polylactides (PLAs) from rac-LA was determined. Complexes 2 and 3 afforded isotactic-enriched PLA (Pm = 0.78-0.71) with narrow MWD (1.07-1.04), on the other hand complexes 1 and 4 produced atactic PLA. Kinetic and post polymerization studies confirm that the polymerization proceeds through the coordination-insertion mechanism. This journal is � The Royal Society of Chemistry 2015. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|