A "Lithium-Bonded" Cyclopropyl Edge: The X-ray Crystal Structure of [Li-O-C(Me)-(c-CHCH2CH2)2]6 and Computational Studies
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- 作者：Bernd Goldfuss ; Paul von Ragué ; Schleyer ; and Frank Hampel
- 刊名：Journal of the American Chemical Society
- 出版年：1996
- 出版时间：December 4, 1996
- 年：1996
- 卷：118
- 期：48
- 页码：12183 - 12189
- 全文大小：511K
- 年卷期：v.118,no.48(December 4, 1996)
- ISSN：1520-5126
文摘
The short Li-C distances (Li1-C2 =2.615(3) Å, Li1-C3 = 2.644(3) Å) inthe X-ray crystal structure of[Li-O-C(Me)-(c-CHCH2CH2)2]6(7)6 characterize Li-cyclopropane edgecoordinations. The Li-cyclopropaneinteractions increase the C2-C3 distances(1.519(3) Å) relative to those of the free cyclopropyl edges(C2-C4 =C6-C7 = 1.499(2) Å) by 0.02 Å.The bent bonds of cyclopropane give rise to an electrostaticpotential pattern,which strongly favors edge coordination as is observed experimentallyin (7)6, but also permits a metastableLi+face complex. The cyclopropane edge also is the favored site forhydrogen bonding, but not for protonation. TheC-C bond length elongations, the coordination energiesEcoord, and the charge redistributions uponmetal cationedge interactions all are related to the distances between thecyclopropane C-C bond centers and the cations. Thisis evaluated for the alkali metal cation-cyclopropane complexes(cation = Li+ to Cs+). Moregenerally, thecyclopropane C-C bond length variations can be employed as astructural measure for the magnitudes of electrostaticinteractions.