| Item type: | Article | ||||
|---|---|---|---|---|---|
| Journal or Publication Title: | Chemistry - A European Journal | ||||
| Publisher: | WILEY-V C H VERLAG GMBH | ||||
| Place of Publication: | BERLIN | ||||
| Volume: | 6 | ||||
| Number of Issue or Book Chapter: | 20 | ||||
| Page Range: | pp. 3806-3820 | ||||
| Date: | 2000 | ||||
| Institutions: | Chemistry and Pharmacy > Institut für Organische Chemie | ||||
| Identification Number: |
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| Keywords: | PYRAMIDAL INVERSION; FULLERENE FORMATION; CYCLYNES; PHOSPHORUS; PHOSPHINES; BARRIERS; ELEMENTS; UNITS; coupling reactions; inversion barriers; macrocycles; NMR spectroscopy; phosphacyclopolyynes; phosphanes | ||||
| Dewey Decimal Classification: | 500 Science > 540 Chemistry & allied sciences | ||||
| Status: | Published | ||||
| Refereed: | Yes, this version has been refereed | ||||
| Created at the University of Regensburg: | Yes | ||||
| Item ID: | 74065 |
Abstract
The Eglinton reaction of diethynyl(2,4,6-tri-tert-butylphenyl)phosphane (7a), that is. the oxidative coupling of 3, 4, 5, or 6 of these phosphane units, affords a mixture of the 15-, 20-, 25-, and 30-membered macrocycles 8, 9, 10, and 11. Pure triphosphacyclopentadecahexayne 8 and pentaphosphacyclopentacosadecayne 10 were isolated by HPLC, while the mixture of 9 and 11 could not be separated. ...
Abstract
The Eglinton reaction of diethynyl(2,4,6-tri-tert-butylphenyl)phosphane (7a), that is. the oxidative coupling of 3, 4, 5, or 6 of these phosphane units, affords a mixture of the 15-, 20-, 25-, and 30-membered macrocycles 8, 9, 10, and 11. Pure triphosphacyclopentadecahexayne 8 and pentaphosphacyclopentacosadecayne 10 were isolated by HPLC, while the mixture of 9 and 11 could not be separated. Multistep syntheses of open-chain polyphosphapolyynes are described, whose intra- or intermolecular coupling yields the phosphamacrocycles 8, 9, and 11. Eglinton coupling of bis(ethynylphosphanyl)butadiyne (17) gave a mixture of the 20-membered tetraphssphacycloicosaoctayne 9, the 30-membered hexaphosphacyclotriacontadodecayne 11, and the 40-membered octaphosphacyclotetracontahexadecayne 23 as result of a di-, tri-, and tetramerization, respectively. Intramolecular coupling of bis[(ethynylphosphanyl)butadiynyl]phosphane 25a gave 8, while intermolecular coupling gave 11; these two compounds were isolated by chromatography to give yields of 70 and 5%, respectively. The open-chain tetraphosphaeikosaoctayne 28 couples intramolecularly to give 9 and intermolecularly to give the 40-membered octaphosphacyclotetracontahexadecayne 23, which was isolated in the pure form. Octaphosphatetracontahexadecayne 32 cyclized ro give 23, exclusively. The temperature-dependent H-1 and P-31 NMR spectra of the open-chain and cyclic ethynylphosphanes indicated a lowering of the inversion barrier of the tertiary phosphanes from the usual 130-140 kJ mol(1) to 65 - 75 kJ mol(-1). Ab initio calculations proved that the dramatic reduction of the inversion barriers results from the interaction of the lone pair on phosphorus with the pi orbitals of the triple bonds in the planar transition state during inversion. The situation is comparable with the dramatic reduction of the P inversion barrier in phospholes, because of the planar, aromatic transition state. The polyphospha[m]cyclo[n]carbons may be considered as precursors to cyclic PmCn systems.
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