Symmetric {cyclopentadienyl/indenyl}-metallocene catalysts: synthesis, structure, isospecific polymerization of propylene and stereocontrol mechanism

• Published in: Dalton transactions : an international journal of inorganic chemistry 2023-06, Vol.52 (25), p.862-863
• Main Authors: Theodosopoulou, Dimitra, De La Pena, Miguel Alonso, Abou Derhamine, Sary, Douair, Iskander, Roisnel, Thierry, Cordier, Marie, Piola, Lorenzo, Fernandez, Alvaro, Welle, Alexandre, Maron, Laurent, Carpentier, Jean-François, Kirillov, Evgueni
• Format: Article
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d3dt01306e

A series of new Me 2 Si-bridged cyclopentadiene/indene proligands {Me 2 Si(R 2′,5′ 2 -R 3′,4′ 2 -Cp)(R 2 ,R 4 ,R 5 ,R 6 -Ind)H 2 } ( 1a-j ) with various substitutions both on the indene and cyclopentadiene moieties was prepared. The corresponding C 1 -symmetric group 4 ansa -metallocene complexes (M = Zr, Hf), namely, {Me 2 Si(Me 4 Cp)(Ind)}ZrCl 2 ( 2a-Zr ), {Me 2 Si(Me 4 Cp)(2-Me,4-Ph-Ind)}MCl 2 ( 2b-M ), {Me 2 Si(Me 4 Cp)(2-Me,4-Ph,6- t Bu-Ind)}ZrCl 2 ( 2c-Zr ), {Me 2 Si(Me 4 Cp)(2-Me,4-Ph,5-OMe,6- t Bu-Ind)}MCl 2 ( 2d-M ), {Me 2 Si(Me 4 Cp)(2-R′,4-(3′,5′- t Bu 2 ,4′-OMe-C 6 H 2 ),5-OMe,6- t Bu-Ind)}ZrCl 2 , R′ = Me ( 2e-Zr ), R′ = Et ( 2f-Zr ), {Me 2 Si(2,5-Ph 2 -3,4-Me 2 -Cp)(2-Me,4-(3′,5′- t Bu 2 ,4′-OMe-C 6 H 2 ),5-OMe,6- t Bu-Ind)}ZrCl 2 ( 2g-Zr ), {Me 2 Si(Me 4 Cp)(2-Me,4-(3′,6′- t Bu 2 -carbazol-4′-yl)-Ind)}ZrCl 2 ( 2h-Zr ), {Me 2 Si(2,5-Me 2 ,3,4-iPr 2 -Cp)(2-Me,4-Ph-Ind)}ZrCl 2 ( 2i-Zr ), {Me 2 Si(2,5-Me 2 ,3,4-iPr 2 -Cp)(2-Me,4-Ph,6- t Bu-Ind)}ZrCl 2 ( 2j-Zr ) and {Me 2 Si(Me 4 Cp)(2-Me-4,5-[ a ]anthracene-Ind)}MCl 2 ( 2 k-Zr ) were synthesized and characterized by NMR spectroscopy and mass spectrometry. The solid-state molecular structures of 2b-Zr , 2d-Zr , 2e-Zr , 2f-Zr , 2j-Zr and 2k-Zr were determined by X-ray crystallography. The zirconocene complexes, once activated with MAO in toluene solution, exhibited propylene polymerization activities at 60 °C up to 161 000 kg(PP) mol(Zr) −1 h −1 , affording highly isotactic polypropylenes ( i PP) with [ m ] 4 up to 96.5% and T m up to 157 °C. Also, metallocene complexes 2b-e-Zr were supported on SiO 2 -MAO and evaluated in slurry bulk propylene polymerization at 70 °C, producing i PPs with [ m ] 4 = 91.7-96.6 mol% and low regiodefects (0.2-0.3 mol%) content, with productivities up to 636 000 kg(PP) mol(Zr) −1 h −1 . DFT calculations allowed rationalizing a polymerization reaction mechanism occurring through "chain-stationary" enchainment with preference for 1,2-insertions. A series of new Me 2 Si-bridged cyclopentadiene/indene proligands {Me 2 Si(R 2′,5′ 2 -R 3′,4′ 2 -Cp)(R 2 ,R 4 ,R 5 ,R 6 -Ind)H 2 } ( 1a-j ) with various substitutions both on the indene and cyclopentadiene moieties was prepared.