The acid-catalyzed reaction between formaldehyde and 1H-indene, 3-alkyl- and 3-aryl-1H-indenes, and six-membered-ring substituted 1H-indenes, with the 1H-indene/CH2O ratio of 2 : 1, at temperatures above 608 in hydrocarbon solvents, yields 2,2’-methylenebis[1H-indenes] 1–8 in 50–100% yield. These 2,2’-methylenebis[1H-indenes] are easily deprotonated by 2 equiv. of BuLi or MeLi to yield the corresponding dilithium salts, which are efficiently converted into ansa-metallocenes of Zr and Hf. The unsubstituted dichloro{(1,1’,2,2’,3,3’,3a,3’a,7a,7’a-eta)-2,2’-methylenebis[1H-inden-1-yl]}zirconium ([ZrCl(2)(1’)]) is the least soluble in organic solvents. Substitution of the 1H-indenyl moieties by hydrocarbyl substituents increases the hydrocarbon solubility of the complexes, and the presence of a substituent larger than a Me group at the 1,1’ positions of the ligand imparts a high diastereoselectivity to the metallation step, since only the racemic isomers are obtained. Methylene-bridged ‘ansa-zirconocenes’ show a noticeable open arrangement of the bis[1H-inden-1-yl] moiety, as measured by the angle between the planes defined by the two p-ligands (the ‘bite angle’). In particular, of the ‘zirconocenes’ structurally characterized so far, the dichloro{(1,1’,2,2’,3,3’,3a,3’a,7a,7’a-eta)-2,2’-methylenebis[4,7-dimethyl-1H-inden-1-yl]}zirconium ([ZrCl(2)(5’)] is the most open. The mixture [ZrCl(2)(1’)]/methylalumoxane (MAO) is inactive in the polymerization of both ethylene and propylene, while the metallocenes with substituted indenyl ligands polymerize propylene to atactic polypropylene of a molecular mass that depends on the size of the alkyl or aryl groups at the 1,1’ positions of the ligand. Ethene is polymerized by rac-dichloro-{(1,1’,2,2’,3,3’,3a,3’a,7a,7’a-eta)-2,2’-methylenebis[1-methyl-1H-inden-1-yl]}zirconium ([ZrCl(2)(2’)])/MAO to polyethylene waxes (average degree of polymerization ca. 100), which are terminated almost exclusively by ethenyl end groups. Polyethylene with a high molecular mass could be obtained by increasing the size of the 1-alkyl substituent.

Methylene-bridged metallocenes with 2,2´-methylenebis[1H-inden-1-yl] ligands : Synthesis, characterization, and polymerization catalysis of a synthetically simple class of C(2)- and C(2v)-symmetric ansa-metallocenes / L. Resconi, I. Camurati, C. Fiori, D. Balboni, P. Mercandelli, A. Sironi. - In: HELVETICA CHIMICA ACTA. - ISSN 0018-019X. - 89:8(2006), pp. 1497-1523. [10.1002/hlca.200690154]

Methylene-bridged metallocenes with 2,2´-methylenebis[1H-inden-1-yl] ligands : Synthesis, characterization, and polymerization catalysis of a synthetically simple class of C(2)- and C(2v)-symmetric ansa-metallocenes

P. Mercandelli
Penultimo
;
A. Sironi
Ultimo
2006

Abstract

The acid-catalyzed reaction between formaldehyde and 1H-indene, 3-alkyl- and 3-aryl-1H-indenes, and six-membered-ring substituted 1H-indenes, with the 1H-indene/CH2O ratio of 2 : 1, at temperatures above 608 in hydrocarbon solvents, yields 2,2’-methylenebis[1H-indenes] 1–8 in 50–100% yield. These 2,2’-methylenebis[1H-indenes] are easily deprotonated by 2 equiv. of BuLi or MeLi to yield the corresponding dilithium salts, which are efficiently converted into ansa-metallocenes of Zr and Hf. The unsubstituted dichloro{(1,1’,2,2’,3,3’,3a,3’a,7a,7’a-eta)-2,2’-methylenebis[1H-inden-1-yl]}zirconium ([ZrCl(2)(1’)]) is the least soluble in organic solvents. Substitution of the 1H-indenyl moieties by hydrocarbyl substituents increases the hydrocarbon solubility of the complexes, and the presence of a substituent larger than a Me group at the 1,1’ positions of the ligand imparts a high diastereoselectivity to the metallation step, since only the racemic isomers are obtained. Methylene-bridged ‘ansa-zirconocenes’ show a noticeable open arrangement of the bis[1H-inden-1-yl] moiety, as measured by the angle between the planes defined by the two p-ligands (the ‘bite angle’). In particular, of the ‘zirconocenes’ structurally characterized so far, the dichloro{(1,1’,2,2’,3,3’,3a,3’a,7a,7’a-eta)-2,2’-methylenebis[4,7-dimethyl-1H-inden-1-yl]}zirconium ([ZrCl(2)(5’)] is the most open. The mixture [ZrCl(2)(1’)]/methylalumoxane (MAO) is inactive in the polymerization of both ethylene and propylene, while the metallocenes with substituted indenyl ligands polymerize propylene to atactic polypropylene of a molecular mass that depends on the size of the alkyl or aryl groups at the 1,1’ positions of the ligand. Ethene is polymerized by rac-dichloro-{(1,1’,2,2’,3,3’,3a,3’a,7a,7’a-eta)-2,2’-methylenebis[1-methyl-1H-inden-1-yl]}zirconium ([ZrCl(2)(2’)])/MAO to polyethylene waxes (average degree of polymerization ca. 100), which are terminated almost exclusively by ethenyl end groups. Polyethylene with a high molecular mass could be obtained by increasing the size of the 1-alkyl substituent.
Settore CHIM/03 - Chimica Generale e Inorganica
2006
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/30130
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