High-Spin and Spin-Crossover Behavior in Monomethylated Bis(indenyl)chromium(II) Complexes
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- 作者：M. Brett Meredith ; Jeffrey A. Crisp ; Erik D. Brady ; Timothy P. Hanusa ; Gordon T. Yee ; Neil R. Brooks ; Benjamin E. Kucera ; Victor G. Young ; Jr.
- 刊名：Organometallics
- 出版年：2006
- 出版时间：October 9, 2006
- 年：2006
- 卷：25
- 期：21
- 页码：4945 - 4952
- 全文大小：335K
- 年卷期：v.25,no.21(October 9, 2006)
- ISSN：1520-6041
文摘
Previous work on bis(indenyl)chromium(II) complexes substituted with bulky groups (i-Pr, t-Bu, SiMe3)found that their spin state (S = 1 or 2) depended on the symmetry of the molecules. Complexes withinversion symmetry (staggered rings) were high-spin; lower symmetry compounds with twisted (gauche)ligands were low spin. The present work explores the effect of methyl group substitution on the indenylligand, which leads to complexes possessing either staggered or eclipsed conformations. The monosubstituted compounds [(1 or 2)-MeC9H6]2Cr are prepared from the substituted alkali metal indenides andCrCl2 in THF. X-ray diffraction results indicate that (2-MeC9H6)2Cr exists in a staggered conformation,with Cr-C (av) = 2.308(7) Å, and is a high-spin species in the solid state and solution. In contrast, themonomeric (1-MeC9H6)2Cr is eclipsed in the solid state, where it exhibits spin-crossover behavior overa wide temperature range; the average Cr-C distances vary with temperature, from 2.179(9) Å at 105 Kto 2.262(10) Å at 298 K. An attempt to form (4-MeC9H6)2Cr produced the dimeric, thermally unstablecomplex (
5-indenyl')2(
,3-indenyl')Cr2(-Cl) instead. Correlations between the structure and magneticproperties in bis(indenyl)chromium(II) complexes have been made with density functional theorycalculations, which indicate that an eclipsed ligand conformation supports a high spin state, but not tothe extent that the staggered form does.
5-indenyl')2(,3-indenyl')Cr2(-Cl) instead. Correlations between the structure and magneticproperties in bis(indenyl)chromium(II) complexes have been made with density functional theorycalculations, which indicate that an eclipsed ligand conformation supports a high spin state, but not tothe extent that the staggered form does.