Abstract:
The main objective of this work was to synthesize original metal complexes of original tetradentate dianionic ligands of the type (O,E,E,O), with E = N or S with different steroelectronic properties and to examine the potential of these new complexes as radical initiators and control agents in organometallic-mediated radical polymerization (OMRP). The tetradentate dianionic scaffold of these ligands was shown to be a suitable environment for stabilizing transition metal complexes. Different coordination modes or ligand arrangements were observed depending on the nature of the donor atoms and stereoelectronic parameters of the ligands. A series of acetylacetonato complexes of cobalt(III) and iron(III) of tetradentate diamino-bis (phenolate) ligands was synthesized and characterized by mass spectrometry (ESI-MS), infrared spectroscopy (FT-IR), elemental analysis (EA) and nuclear magnetic resonance (NMR: 1H and 13C{1H}). The molecular structure of all the complexes was confirmed in the solid-state by X-ray diffraction. These complexes are thermally stable, even in the presence of vinyl monomers, and unfortunately the “metal-acac” entity was not able to produce radicals under the thermal conditions investigated in this study. Another series of diamino- or dithioether-bis(phenolate) tetradentate ligands-supported CoII, FeIII and CuII complexes were synthesized, isolated and characterized. The test of polymerization of vinyl acetate, using the CoII complex as moderator, revealed a pseudo first-order kinetic plot, but the evolution of the molar mass with respect to the conversion showed the process to be not wellcontrolled.
