Synthesis, characterization and ethylene polymerization activity of zirconium complexes containing nonsymmetric diamido ligands derived from 2-aminobenzylamine

Citation
Rm. Gauvin et al., Synthesis, characterization and ethylene polymerization activity of zirconium complexes containing nonsymmetric diamido ligands derived from 2-aminobenzylamine, EUR J INORG, (9), 2001, pp. 2337-2346
Citations number
21
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Inorganic & Nuclear Chemistry
Journal title
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
ISSN journal
1434-1948 → ACNP
Issue
9
Year of publication
2001
Pages
2337 - 2346
Database
ISI
SICI code
1434-1948(200109):9<2337:SCAEPA>2.0.ZU;2-7
Abstract
Several N,N ' -bis(trialkylsilyl)-substituted diamines of the general formu la [(SiR3)(2)-ABA]H-2 [ABA = 2-amidobenzylamido, SiR3 = SiMe3 (la), SiMePh2 (1b), SiMe(2)tBu (1c) Or SiiPr(3) (1d)], together with related compounds i n which the substituents of the two nitrogen atoms are different, e.g. [(Si MePh2)(SiMe3)-ABA]H-2 (1g), have been synthesized. Their reaction with 2 eq uiv. of nBuLi afforded the dilithiated derivatives, which reacted with ZrCl 4 to yield metallaspirocyclic complexes of the type Zr[(SiR3)(2)-ABA](2). P rotonolysis of Zr(NMe2)(4) with 1 equiv. of the parent diamines led to the monosubstituted complexes Zr((SiR3)2-ABA](NMe2)2 [SiR3 = SiMe3 (4a), SiMePh 2 (4b) or SiMe(2)tBu (4c)] and Zr[(SiMePh2)(SiMe3)-ABA](NMe2)(2) (4g) in hi gh yield, and subsequent reaction with excess SiMe3Cl afforded the dichlori des Zr[(SiMe3)(2)-ABA]Cl-2 (5a), Zr[(SiMe(2)tBu)(2)-ABA]Cl-2 (5c), and Zr[( SiMePh2)(SiMe3)-ABA]Cl-2 (5g). The X-ray crystal structure of 5c shows that it forms dimers via two Zr-Cl bridges; moreover, a bonding interaction bet ween the zirconium centre and the aryl ipso-carbon atom linked to the anili nic nitrogen atom is evident. A hydrochlorinated derivative of 5c, Zr[(SiMe (2)tBu)(2)(H)-ABA]Cl-3 (6c), was also analysed by X-ray diffraction and sho wn to exhibit analogous structural characteristics. Low-temperature NMR stu dies revealed all these complexes to be fluxional and permitted an insight into the molecular structures in solution. The ABA framework undergoes a ro cking motion about the corresponding ZrN2 plane, whose activation energy is between 37 and 43 kJ mol(-1). Compounds 3 and 5 exist as several stereoiso mers that interconvert by this process. On activation with MAO, the dichlor ide complexes of type 5 polymerize ethylene at both room temperature and pr essure to yield linear high molecular mass polyethylenes with a broad molec ular mass distribution.