Generation of cationic indenyl silylamide gadolinium and scandium complexes [(Ind)Ln{N(SiMe3)2}]+[B(C6F5)4]− and their reactivity for 1,3-butadiene polymerization

Abstract

Highly efficient cis-polymerization of butadiene was achieved by using new bis(indenyl) silylamide rare earth complexes with the cooperation of both a borate salt and i-Bu3Al; treatment of these complexes with organoboron compounds unexpectedly yielded new cationic mono(indenyl) amido species relevant to polymerization.

1,3-Diene Polymerization Mediated by Homoleptic Tetramethylaluminates of the Rare-Earth Metals

“…As a clear identification of the active species was not successful so far, due to the paramagnetic character of most of the lanthanide ions and the low tendency of the active species toward crystallization, active species elucidation remains challenging. A reasonable interpretation of this polymerization behavior seems to be that solvent [4,5,13,37], pre-reaction side products (e.g., Ph 3 CMe (A) and PhNMe 2 (B): Ln(III)-arene coordination) [38][39][40], or even anion coordination (e.g., via Ln(III)-F interactions) [41] come into play. Furthermore, dimerization might take place or a η 2 -to-η 3 coordination switch of the remaining tetramethylaluminate moiety, which tendency seems more pronounced for the larger lanthanides as found for the neutral precatalysts [4,10,12].…”

Indenyl Abstraction versus Alkyl Abstraction of [(Indenyl)ScR2(thf)] by [Ph3C] [B(C6F5)4]: Aspecific and Syndiospecific Styrene Polymerization

“…We believe that this represents the first example of [Ph 3 C] + abstracting a Cp-type p ligand rather than a s-alkyl ligand. [20] can abstract a pbonded indenyl ligand rather than a s-alkyl ligand. The abstraction pathway is influenced by the substituents on the indenyl ligands, and can be controlled by employing different indenyl ligands.…”

Precisely Controlled Polymerization of Styrene and Conjugated Dienes by Group 3 Single‐Site Catalysts

“…A higher conversion and better control molecular weight by using the more bulky bis(indenyl) silylamide rare‐earth metal complex (2‐Ph‐Ind) 2 Gd[N(SiMe 3 ) 2 ] ( 56 ) was reported by Tardif, and high cis ‐,4‐PBD (>99 %) was obtained. Conversely, for the analogous complex 57 , a lower cis ‐1,4‐selectivity was found …”