Multi-frequency continuous-wave and pulsed EPR techniques are employed to investigate Ti(III)-chloro complexes obtained by dissolving TiCl3 in anhyd. and hydrated methanol. Two distinctly different species, characterized by different g matrixes are obsd. in the two cases. Hyperfine sublevel correlation (HYSCORE) spectroscopy is found to be a powerful method to identify the type of nuclei surrounding the Ti3+ ion. For the first time, the hyperfine and nuclear quadrupole data of Ti(III)-bound 35/37Cl nuclei are reported together with 1H and 13C hyperfine data of the coordinated methanol mols. DFT modeling allows interpreting the measured spin Hamiltonian parameters in terms of microscopic models of the solvated species. The theor. observable properties (g matrix, 35/37Cl, 1H and 13C hyperfine tensors) are in quant. agreement with the expts. for two families of complexes: [TiCln(CH3OH)6-n](3-n)+ (with n ranging from 1 to 3) and [Ti(CH3OH)5(OH)]2+ or [Ti(CH3OH)5(OCH3)]2+. The first complex is obsd. in anhyd. methanol, while the second type of complex is obsd. when water is added to the soln., the presence of OH- and/or CH3O- species being promoted by water hydrolysis. The results obtained for the frozen solns. are critically compared to EPR spectra recorded for a MgCl2-supported Ti-based Ziegler-Natta model catalyst.
EPR investigation of TiCl3 dissolved in polar solvents - implications for the understanding of active Ti(III) species in heterogeneous Ziegler-Natta catalysts / Maurelli, S; Morra, E; Van Doorslaer, S; Busico, Vincenzo; Chiesa, M.. - In: PHYSICAL CHEMISTRY CHEMICAL PHYSICS. - ISSN 1463-9076. - 16:(2014), pp. 19625-19633. [10.1039/c4cp02722a]
EPR investigation of TiCl3 dissolved in polar solvents - implications for the understanding of active Ti(III) species in heterogeneous Ziegler-Natta catalysts
BUSICO, VINCENZO;
2014
Abstract
Multi-frequency continuous-wave and pulsed EPR techniques are employed to investigate Ti(III)-chloro complexes obtained by dissolving TiCl3 in anhyd. and hydrated methanol. Two distinctly different species, characterized by different g matrixes are obsd. in the two cases. Hyperfine sublevel correlation (HYSCORE) spectroscopy is found to be a powerful method to identify the type of nuclei surrounding the Ti3+ ion. For the first time, the hyperfine and nuclear quadrupole data of Ti(III)-bound 35/37Cl nuclei are reported together with 1H and 13C hyperfine data of the coordinated methanol mols. DFT modeling allows interpreting the measured spin Hamiltonian parameters in terms of microscopic models of the solvated species. The theor. observable properties (g matrix, 35/37Cl, 1H and 13C hyperfine tensors) are in quant. agreement with the expts. for two families of complexes: [TiCln(CH3OH)6-n](3-n)+ (with n ranging from 1 to 3) and [Ti(CH3OH)5(OH)]2+ or [Ti(CH3OH)5(OCH3)]2+. The first complex is obsd. in anhyd. methanol, while the second type of complex is obsd. when water is added to the soln., the presence of OH- and/or CH3O- species being promoted by water hydrolysis. The results obtained for the frozen solns. are critically compared to EPR spectra recorded for a MgCl2-supported Ti-based Ziegler-Natta model catalyst.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
