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Ph2Si-bridged constrained-geometry complexes of hafnium and titanium for copolymerization of ethylene and 1-octene: an experimental and computational comparison.

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Title: Ph2Si-bridged constrained-geometry complexes of hafnium and titanium for copolymerization of ethylene and 1-octene: an experimental and computational comparison.
Authors: Kuchuk, Ekaterina1 (AUTHOR), Giffin, Kaitie A.2 (AUTHOR), Welle, Alexandre2 (AUTHOR), Dauw, Katty Den2 (AUTHOR), Fernandez, Alvaro2 (AUTHOR), Cordier, Marie3 (AUTHOR), Roisnel, Thierry3 (AUTHOR), Carpentier, Jean-Francois1 (AUTHOR) jean-francois.carpentier@univ-rennes.fr, Kirillov, Evgueni1 (AUTHOR) evgueni.kirillov@univ-rennes.fr
Source: Dalton Transactions: An International Journal of Inorganic Chemistry. 5/19/2026, Vol. 55 Issue 19, p7512-7520. 9p.
Subjects: Copolymerization, Titanium catalysts, Hafnium compounds, Density functional theory, Octene, Ethylene, Metallocene catalysts
Abstract: A series of new constrained-geometry hafnium and titanium complexes, including {Me2Si(2,7-tBu2Flu)NtBu}HfCl2 (1-HfCl2), {Ph2Si(2,7-tBu2Flu)NtBu}HfCl2 (2-HfCl2) and {Ph2Si(2,7-tBu2Flu)NtBu}TiCl2 (2-TiCl2), was synthesized and fully characterized using solution NMR spectroscopy and X-ray crystallography. These complexes were subsequently evaluated in the copolymerization of ethylene with 1-octene ([C8]0 = 0.48–1.88 M), revealing striking differences in catalytic performance and properties of the resulting polyolefin elastomers/plastomers (POE/POP). The hafnium complexes 1-HfCl2 and 2-HfCl2 exhibited low catalytic activity, yielding polymers with broad molecular weight distributions and only modest incorporation of 1-octene. In contrast, the titanium complex 2-TiCl2 demonstrated significantly higher catalytic activity and achieved substantial 1-octene incorporation at an ethylene/1-octene molar ratio of ca. 6 : 1, with values reaching up to 36.6 mol%. 2-TiCl2 exhibited approximately half the productivity of benchmark CGC {Me4CpSiMe2NtBu}TiCl2 (3-TiCl2), yet yielding POE with a much higher molecular weight and a density of 0.8547 g cm−3. DFT calculations were also performed for the cationic catalytic species derived from the pre-catalysts 2-HfCl2 and 2-TiCl2 to rationalize the relative performance of the titled systems in incorporating ethylene and 1-octene and undergoing termination and transfer reactions. A +5.6 kcal mol−1 energy difference (in terms of ΔΔH‡) was computed between the transition states for the third ethylene insertion into the M–C(polymeryl) bond for the Hf-based system compared to the Ti-based system; other phenomena possibly plaguing efficiency of the Hf-system are discussed. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:A series of new constrained-geometry hafnium and titanium complexes, including {Me2Si(2,7-tBu2Flu)NtBu}HfCl2 (1-HfCl2), {Ph2Si(2,7-tBu2Flu)NtBu}HfCl2 (2-HfCl2) and {Ph2Si(2,7-tBu2Flu)NtBu}TiCl2 (2-TiCl2), was synthesized and fully characterized using solution NMR spectroscopy and X-ray crystallography. These complexes were subsequently evaluated in the copolymerization of ethylene with 1-octene ([C8]0 = 0.48–1.88 M), revealing striking differences in catalytic performance and properties of the resulting polyolefin elastomers/plastomers (POE/POP). The hafnium complexes 1-HfCl2 and 2-HfCl2 exhibited low catalytic activity, yielding polymers with broad molecular weight distributions and only modest incorporation of 1-octene. In contrast, the titanium complex 2-TiCl2 demonstrated significantly higher catalytic activity and achieved substantial 1-octene incorporation at an ethylene/1-octene molar ratio of ca. 6 : 1, with values reaching up to 36.6 mol%. 2-TiCl2 exhibited approximately half the productivity of benchmark CGC {Me4CpSiMe2NtBu}TiCl2 (3-TiCl2), yet yielding POE with a much higher molecular weight and a density of 0.8547 g cm−3. DFT calculations were also performed for the cationic catalytic species derived from the pre-catalysts 2-HfCl2 and 2-TiCl2 to rationalize the relative performance of the titled systems in incorporating ethylene and 1-octene and undergoing termination and transfer reactions. A +5.6 kcal mol−1 energy difference (in terms of ΔΔH‡) was computed between the transition states for the third ethylene insertion into the M–C(polymeryl) bond for the Hf-based system compared to the Ti-based system; other phenomena possibly plaguing efficiency of the Hf-system are discussed. [ABSTRACT FROM AUTHOR]
ISSN:14779226
DOI:10.1039/d6dt00602g