Structural and Dynamic Features of
Bis[2-(2-furyl)indenyl]zirconium Derivatives<sup>†</sup>
Thorsten Dreier
Klaus Bergander
Elina Wegelius
Roland Fröhlich
Gerhard Erker
10.1021/om0104518.s002
https://acs.figshare.com/articles/journal_contribution/Structural_and_Dynamic_Features_of_Bis_2-_2-furyl_indenyl_zirconium_Derivatives_sup_sup_/3766497
Treatment of 2-indanone with 2-lithio-5-methylfuran, followed by hydrolysis, dehydration,
deprotonation with <i>n</i>-butyllithium, and transmetalation, gave bis[2-(5-methyl-2-furyl)indenyl]zirconium dichloride (<b>6a</b>). The dynamic 600 MHz <sup>1</sup>H NMR spectroscopic analysis in the
temperature range between 253 and 128 K revealed the presence of two metallocene
conformational isomers in a 60:40 ratio. It is likely that this observed feature just originates
from freezing out the indenyl−furyl rotation. The corresponding activation barrier of <b>6a</b>
was determined at Δ<i>G</i><sup>⧧</sup><sub>rot</sub> = 7.0 ± 0.4 kcal mol<sup>-1</sup> by a line shape analysis. A series of analogous
5-methyl-2-furyl- and 5-methyl-2-thienyl-substituted bis(indenyl)zirconium dibromides and
dichlorides show analogous conformational behavior and almost identical rotational activation
energies. In the bis[2-(5-methyl-2-furyl)indenyl]ZrR<sub>2</sub> series the metallocene rotational barrier
can apparently be frozen on the 600 MHz <sup>1</sup>H NMR time scale for R = CH<sub>2</sub>CMe<sub>3</sub> and
R = CH<sub>2</sub>Ph. The di(neopentyl)Zr complex <b>7b</b> shows a metallocene rotational barrier of
Δ<i>G</i><sup>⧧</sup><sub>rot(Cp)</sub>(213 K) = 9.0 ± 0.3 kcal mol<sup>-1</sup>, and for the di(benzyl)Zr complex <b>7c</b> a Δ<i>G</i><sup>⧧</sup><sub>rot(Cp)</sub> value
of 11.4 ± 0.3 kcal mol<sup>-1</sup> was obtained at 243 K. In the cases of <b>7b</b> and <b>7c</b> only chiral <i>rac</i>-type metallocene conformers were found in solution within the limits of the accuracy of the
<sup>1</sup>H NMR method. The complexes bis[2-(5-ethyl-2-furyl)indenyl]ZrCl<sub>2</sub> (<b>8</b>) and bis[2-(5-methyl-2-furyl)indenyl]Zr(neopentyl)<sub>2</sub> (<b>7b</b>) were characterized by X-ray crystal structure analyses.
In the solid state both complexes exhibit chiral <i>rac</i>-like metallocene frameworks.
2001-10-19 00:00:00
rot
CH 2 Ph
methyl
activation
mol
complexes exhibit chiral rac
series
barrier
dichloride
1 H NMR method
CH 2 CMe 3
600 MHz 1 H NMR time scale
7 b
7 c
kcal
600 MHz 1 H NMR spectroscopic analysis
0.3
di
type metallocene conformers
line shape analysis