Structures of three substituted pentacyclo[5.4.0.02, 6.03, 10.05, 9]undecanes and a computational analysis of bond lengths |
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| Authors: | Watson William H Kashyap Ram P Krawiec Mariusz Marchand Alan P Tsay Fuh-Rong |
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| Institution: | (1) Department of Chemistry, Texas Christian University, 76129 Fort Worth, Texas;(2) Department of Chemistry, University of North Texas, P.O. Box 5068, 76203 Denton, Texas |
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| Abstract: | 5-Methyl-2-phenylpentacyclo5.4.0.02, 6.03, 10.05, 9]undecane-8, 11-dione,5-methyl-2-phenylpentacyclo 5.4.0.02,6.03,10.05,9]undecane-8-one-11-ol,and 5-methyl-2-phenylpentacyclo5.4.0.02,6.03,10.05,9]undecane-8,11-diol are three cage compounds which differ only in the oxidation state at C(8) and C(11). The three compounds contain a four-membered, a six-membered, and four five-membered rings fused into a cagelike structure. An X-ray structure analysis shows the C(1)-C(7) and C(9)-C(10) bonds in the diketo cage to be 1.606(2) and 1.586(2) Å, which are significantly longer than in the other two molecules. In order to assess the effects of strain, steric, and electronic factors in these compounds, we investigated the unsubstituted parent cage compounds and a series of derivatives by molecular mechanics (MM3), AMPAC (AM1), MOPAC (PM3), and GAUSSIAN 90 calculations. These data suggest that dipolar through space interactions are responsible for the bond elongation and not a
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* interaction, which has been postulated in parallel-systems originating from a common bond. A small degree of
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*  through-bond interaction may contribute to the lengthening in the dimethylene cage analogues. |
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| Keywords: | Cage compounds long C-C bonds X-ray diffraction molecular mechanics semi-empirical calculations ab initio calculations |
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