Chemistry and Physics Faculty Articles

Tethered Olefin Studies of Alkene versus Tetraphenylborate Coordination and Lanthanide Olefin Interactions in Metallocenes

Document Type

Article

Publication Title

Journal of the American Chemical Society

ISSN

0002-7863

Publication Date

4-30-2003

Abstract

The tethered olefin cyclopentadienyl ligand, [(C5Me4)SiMe2(CH2CH=CH2)]-, forms unsolvated metallocenes, [(C5Me4)SiMe2(CH2CH=CH2)]2Ln (Ln = Sm, 1; Eu, 2; Yb, 3), from [(C5Me4)SiMe2(CH2CH=CH2)]K and LnI2(THF)2 in good yield. Each complex in the solid state has both tethered olefins oriented toward the Ln metal center with the Ln−C(terminal alkene carbon) distances 0.2−0.3 Å shorter than the Ln−C(internal alkene carbon) distances. The olefinic C−C bond distances in 2 and 3, 1.328(4) and 1.328(5) Å, respectively, are normal. Like its permethyl analogue, (C5Me5)2Sm(THF)2, complex 1 reductively couples CO2 to form the oxalate-bridged dimer {[(C5Me4)SiMe2(CH2CH=CH2)]2Sm}2(μ-η2:η2-O2CCO2), 4, in which the tethered olefins are noninteracting substituents. Complex 1 reacts with AgBPh4 to form an unsolvated cation that has the option of coordinating [BPh4]- or a pendant olefin, a competition common in olefin polymerization catalysis. The structure of {[(C5Me4)SiMe2(CH2CH=CH2)]2Sm}[BPh4], 5, shows that both pendant olefins are located near samarium rather than the [BPh4]-counterion.

DOI

10.1021/ja020957x

Volume

125

Issue

17

First Page

5204

Last Page

5212

Comments

©2003 American Chemical Society

This document is currently not available here.

Peer Reviewed

Find in your library

Share

COinS