Synthesis, Structure, Strain Energy, and Excess Strain of a Phospha[3]triangulane
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- 作者：Koop Lammertsma ; Bing Wang ; Jui-Te Hung ; Andreas W. Ehlers ; and Gary M. Gray
- 刊名：Journal of the American Chemical Society
- 出版年：1999
- 出版时间：December 22, 1999
- 年：1999
- 卷：121
- 期：50
- 页码：11650 - 11655
- 全文大小：96K
- 年卷期：v.121,no.50(December 22, 1999)
- ISSN：1520-5126
文摘
(7-Phenyl-7-phosphadispiro[2.0.2.1]heptane)pentacarbonyltungsten (8), a phospha[3]triangulane, wassynthesized from bicyclopropylidene. Its single-crystal X-ray structure determination is reported. Comparisonof the crystal structure data with those of the related phosphaspiropentane 7 and phosphirane 6 complexessuggests that the phosphirane ring tightens when the number of spiro atoms is increased. This is supported bythe B3LYP and MP2/6-31G* computed geometries of the uncomplexed parent systems. Ab initio calculatedheats of formation and strain energies (SE) are reported for the parent phosphirane 11, phosphaspiropentane12, and phospha[3]triangulane 13 using both G2MP2 theory and ring separation reactions. Our best estimatesfor the 
Hf of 11, 12, and 13 are 18.3, 48.4, and 78.2 kcal/mol, respectively, with corresponding SE valuesof 21.3, 54.7, and 87.9 kcal/mol. For comparison, the slightly modified G2MP2 method was also applied tocyclopropane 1, spiropentane 2, and [3]triangulane 3 to give respective Hf values of 12.6, 44.3, and 75.3kcal/mol, with corresponding SEs of 28.0, 64.6, and 100.5 kcal/mol, all of which are in excellent agreementwith reported experimental data. These strain energies suggest that the excess strain per spiro atom is 5.3kcal/mol for phospha[n]triangulanes, which is smaller than the 8.6 kcal/mol determined from the heat ofcombustion measurements for the [n]triangulanes.
Hf of 11, 12, and 13 are 18.3, 48.4, and 78.2 kcal/mol, respectively, with corresponding SE valuesof 21.3, 54.7, and 87.9 kcal/mol. For comparison, the slightly modified G2MP2 method was also applied tocyclopropane 1, spiropentane 2, and [3]triangulane 3 to give respective Hf values of 12.6, 44.3, and 75.3kcal/mol, with corresponding SEs of 28.0, 64.6, and 100.5 kcal/mol, all of which are in excellent agreementwith reported experimental data. These strain energies suggest that the excess strain per spiro atom is 5.3kcal/mol for phospha[n]triangulanes, which is smaller than the 8.6 kcal/mol determined from the heat ofcombustion measurements for the [n]triangulanes.