Metastable P-Tellurium-Substituted Phosphaalkenes: Formation, 125Te- and 31P-NMR Spectroscopic Characterization,and Decomposition |
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Authors: | Jens Mahnke Delia Bugnariu Frank Ruthe Peter G. Jones |
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Affiliation: | Institut fuer Anorganische und Analytische Chemie, Technische Universitaet Braunschweig, Germany |
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Abstract: | AbstractThe formation and decomposition of P-tellurium-substituted phosphaalkenes was followed by 31P- and 125Te-NMR spectroscopy. Acyclic compounds with C?P-Te moieties are in general thermally labile, but bulky substituents enhance the lifetime of a number of species. The P-chlorophosphaalkene (Me3Si)2C?PCl (1a) reacts with the disilyltelluride (iPrMe2Si)2Te (2) leading to the mixed-substituted telluride (Me3Si)2C?PTeSiMe2iPr 3a which reacts with another equivalent of 1a furnishing the tellurobis(phosphaalkene) [(Me3Si)2C?P]2Te (4a). 4a is a shortlived compound decomposing thermally with precipitation of elemental tellurium, leading to a known diphosphabicyclobutane 5a. In a similar way, the bulkier P-chlorophosphaalkene (iPrMe2Si)2C?PCl (1b) reacts with (iPrMe3Si)2Te furnishing [(iPrMe2Si)2C?P]2Te (4b), which loses tellurium much more slowly than 4a and can be kept in cold solutions for an extended time. Reactions of in situ-prepared lithium aryltellurolates LiTeAr 6 – 9 [Ar?Ph: 6, Ar?2,4,6-Me3Ph (?Mes): 7, Ar?2,4,6-iPr3Ph (?TIP): 8, Ar?2,4,6-tBu3Ph (?Mes*): 9] with 1a provide P-aryltellurophosphaalkenes 10 – 13, which decompose with the loss of diarylditellurides leading to 5a. After a 2 + 4 cycloaddition trapping experiment of 12 with cyclopentadiene, a metastable P-aryltelluro phosphanorbornene 14 was detected by 31P-NMR. Reactions of elemental tellurium with P-phosphanylphosphaalkenes (Me3Si)2C?PPR′R′;′ 15 – 17 (R′, R′′?iPr: 15; R′?iPr, R′′?tBu: 16; R′, R′′?tBu: 17) lead to metastable insertion products (Me3Si)2C?PTePR′R′′ 18 – 20 that decompose with formation of the tellurobisphosphanes (R′R′′P)2Te 21 – 23, and of the bicyclic diphosphane 5a, which isomerises thermally to the diphosphabicyclooctane 24. The P-di-i-propylphosphanyl-phosphanorbornene 25 dismutates under the action of tellurium into the symmetric diphosphanes iPr4P2 and bis-phosphanorbornene 26. The tellurium-free products 24 and 26 were characterized by X-ray crystallography. |
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Keywords: | Phosphaalkenes P-Tellurophosphaalkenes tellurophosphanes diphoshanes 125Te-NMR X-ray crystallography |
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