Ethene polymerization with bis(2-dimethylsilyl-indenyl)zir
conium(IV) di
chloride (
1)/MAO and bis(2-trimethylsilyl-indenyl)zir
conium(IV) di
chloride (
2)/MAO and ethene-
co-1-hexene polymerization with
1/MAOare presented. The end group analysis of homopolymers reveals a pronoun
ced dependen
ce of the terminationrate on temperature
changes. In
combination with the high mole
cular weights obtained, these results are ina
ccord with theoreti
cal predi
ctions. Gel permeation
chromatography, Fourier transform infrared, and
13C NMRanalyses of
copolymerization produ
cts from
1/MAO as a fun
ction of
comonomer
con
centration at two differenttemperature series denote its tenden
cy to form inhomogeneous polymer blends. Thermal analysis andfra
ctionation results of one su
ch blend indi
cate an inhomogeneity in the en
chainment pro
cess and the existen
ceof multiple a
ctive sites of differing geometry. These indi
cations are further supported by AMBER for
ce fieldand density fun
ctional theory studies of the
catalyst pre
cursors and the a
ctive site of
1/MAO. For this system,
![](/images/gif<font color=)
chars/delta.gif" BORDER=0 >-agosti
c intera
ctions for the stabilization of the zir
conium
cation are favored over
![](/images/gif<font color=)
chars/beta2.gif" BORDER=0 ALIGN="middle">-agosti
c intera
ctions,whi
ch, in
contrast to the situation in studies on bis-Cp systems, is a sparsely populated spe
cies. The gap ina
ctivation enthalphies for
![](/images/gif<font color=)
chars/beta2.gif" BORDER=0 ALIGN="middle">-hydride transfer and elimination is marginalized for these bulky zir
cono
cenes,and
con
ceptually new me
chanisms for the isomerization of the vinyl end groups are dis
cussed. Further,unexpe
cted a
ctivation of the sili
con-hydrogen bond within the ligand framework is observed with an a
ctivationenthalpy as low as 14 k
cal/mol.