1,3‐Diene Polymerization Promoted by Half‐Sandwich Rare‐Earth‐Metal Dimethyl Complexes: Active Species Clustering and Cationization/Deactivation Processes

2019 ◽  
Vol 25 (30) ◽  
pp. 7298-7302 ◽  
Author(s):  
Christoph O. Hollfelder ◽  
Lars N. Jende ◽  
Hans‐Martin Dietrich ◽  
Klaus Eichele ◽  
Cäcilia Maichle‐Mössmer ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Earth Metal ◽  
Active Species ◽  
Half Sandwich

scholarly journals C–H-Bond Activation and Isoprene Polymerization Studies Applying Pentamethylcyclopentadienyl-Supported Rare-Earth-Metal Bis(Tetramethylaluminate) and Dimethyl Complexes

Molecules ◽  
2019 ◽  
Vol 24 (20) ◽  
pp. 3703 ◽  
Author(s):  
Christoph O. Hollfelder ◽  
Melanie Meermann-Zimmermann ◽  
Georgios Spiridopoulos ◽  
Daniel Werner ◽  
Karl W. Törnroos ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Binary Systems ◽  
Bond Activation ◽  
Earth Metal ◽  
Active Species ◽  
Redistribution Reactions ◽  
Butadiene Polymerization ◽  
Directing Effect ◽  
Half Sandwich

As previously shown for lutetium and yttrium, 1,2,3,4,5-pentamethylcyclopentadienyl (C5Me5 = Cp*)-bearing rare-earth metal dimethyl half-sandwich complexes [Cp*LnMe2]3 are now also accessible for holmium, dysprosium, and terbium via tetramethylaluminato cleavage of [Cp*Ln(AlMe4)2] with diethyl ether (Ho, Dy) and tert-butyl methyl ether (TBME) (Tb). C–H-bond activation and ligand redistribution reactions are observed in case of terbium and are dominant for the next larger-sized gadolinium, as evidenced by the formation of mixed methyl/methylidene clusters [(Cp*Ln)5(CH2)(Me)8] and metallocene dimers [Cp*2Ln(AlMe4)]2 (Ln = Tb, Gd). Applying TBME as a “cleaving” reagent can result in both TBME deprotonation and ether cleavage, as shown for the formation of the 24-membered macrocycle [(Cp*Gd)2(Me)(CH2OtBu)2(AlMe4)]4 or monolanthanum complex [Cp*La(AlMe4){Me3Al(CH2)OtBu}] and monoyttrium complex [Cp*Y(AlMe4)(Me3AlOtBu)], respectively. Complexes [Cp*Ln(AlMe4)2] (Ln = Ho, Dy, Tb, Gd) and [Cp*LnMe2]3 (Ln = Ho, Dy) are applied in isoprene and 1,3-butadiene polymerization, upon activation with borates [Ph3C][B(C6F5)4] and [PhNHMe2][B(C6F5)4], as well as borane B(C6F5)3. The trans-directing effect of AlMe3 in the binary systems [Cp*Ln(AlMe4)2]/borate is revealed and further corroborated by the fabrication of high-cis-1,4 polybutadiene (97%) with “aluminum-free” [Cp*DyMe2]3/[Ph3C][B(C6F5)4]. The formation of multimetallic active species is supported by the polymerization activity of pre-isolated cluster [(Cp*Ho)3Me4(CH2)(thf)2].

Copolymerization of Ethylene with Norbornene Catalyzed by Cationic Rare-Earth Metal Half-Sandwich Complexes

2008 ◽  
Vol 41 (24) ◽  
pp. 9565-9569 ◽  
Author(s):  
Andrea Ravasio ◽  
Cristina Zampa ◽  
Laura Boggioni ◽  
Incoronata Tritto ◽  
Julia Hitzbleck ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Earth Metal ◽  
Sandwich Complexes ◽  
Half Sandwich

scholarly journals Unprecedentedly High Activity and/or High Regio-/Stereoselectivity of Fluorenyl-Based CGC Allyl-Type η3:η1-tert-Butyl(dimethylfluorenylsilyl)amido Ligated Rare Earth Metal Monoalkyl Complexes in Olefin Polymerization

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 836
Author(s):  
Ge Guo ◽  
Xiaolu Wu ◽  
Xiangqian Yan ◽  
Li Yan ◽  
Xiaofang Li ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Earth Metal ◽  
Active Species ◽  
Metal Centers ◽  
Tert Butyl ◽  
Alkyl Groups ◽  
Elemental Analyses ◽  
Catalytically Active ◽  
Geometry Configuration

A series of fluorenyl-based constrained-geometry-configuration (CGC) allyl-type rare earth metal monoalkyl complexes bearing the divalent anionic η3:η1-tert-butyl(dimethylfluorenylsilyl)amido (η3:η1-FluSiMe2NtBu) ligand (η3:η1-FluSiMe2NtBu)Ln(CH2SiMe3)(THF)2 (1–3) have been synthesized via the alkane elimination reaction between the FluHSiMe2NHtBu ligand and rare earth metal tri(trimethylsilylmethyl) complexes Ln(CH2SiMe3)3(THF)n. Their structures are characterized by means of NMR spectrum, elemental analyses, and X-ray diffraction. These complexes 1–3 are isostructural and isomorphous, and each of them adopts a distorted-trigonal-bipyramidal configuration containing one η3:η1-FluSiMe2NtBu ligand, one CH2SiMe3 ligand, and two THF molecules. Unlike traditional CGC allyl-type rare earth metal complexes showing no or low activity and regio-/stereoselectivity in styrene or MMA polymerization, these complexes 1–3 exhibit high catalytic activities and/or high regio-/stereoselectivities in the cis-1,4-polymerization of isoprene and myrcene or in the syndiotactic polymerization of styrene under the aid of different activators (borate or borane) and AlR3. The in situ 1H NMR spectra suggest that the exchanges of chelating ligands such as alkyl groups and divalent anionic η3:η1-FluSiMe2NtBu ligands between rare earth metal centers and Al centers result in the formation of a heterobimetallic tetraalkylaluminate complex R2Al(μ-R)2Ln(R)(μ-R)2AlR2, which is activated by activators to form a divalent cationic species [Ln(μ-R)2AlR2]2+ as a catalytically active species in the coordination–insertion polymerization of olefins.

Rare‐Earth‐Metal Pentadienyl Half‐Sandwich and Sandwich Tetramethylaluminates–Synthesis, Structure, Reactivity, and Performance in Isoprene Polymerization

2019 ◽  
Vol 25 (18) ◽  
pp. 4821-4832 ◽  
Author(s):  
Damir Barisic ◽  
Dennis A. Buschmann ◽  
David Schneider ◽  
Cäcilia Maichle‐Mössmer ◽  
Reiner Anwander
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Earth Metal ◽  
And Performance ◽  
Half Sandwich ◽  
Isoprene Polymerization

Ln(II)/Pb(II)–Ln(III)/Pb(0) Redox Approach toward Rare-Earth-Metal Half-Sandwich Complexes

2015 ◽  
Vol 34 (24) ◽  
pp. 5734-5744 ◽  
Author(s):  
André M. Bienfait ◽  
Benjamin M. Wolf ◽  
Karl W. Törnroos ◽  
Reiner Anwander
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Earth Metal ◽  
Sandwich Complexes ◽  
Half Sandwich
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