Metastable <i>P</i>-Tellurium-Substituted Phosphaalkenes: Formation, <sup>125</sup>Te- and <sup>31</sup>P-NMR Spectroscopic Characterisation, and Decomposition
Creators: name: Mahnke, Jens
name: Bugnariu, Delia
name: Wolf-W. Du Mont
name: Ruthe, Frank
name: Jones, Peter G.
Publisher: name: Taylor & Francis
Year: 2014
Subjects: subject: Cancer
subject: Developmental Biology
subject: Chemistry
subject: Evolutionary Biology
subject: FOS: Biological sciences
subject: FOS: Biological sciences
subject: Pharmacology
subject: Physiology
subject: Cell Biology
subject: Physics
subject: Biochemistry
subject: Biophysics

description: The formation and decomposition of P-tellurium-substituted phosphaalkenes was followed by <sup>31</sup>P- and <sup>125</sup>Te-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 (Me<sub>3</sub>Si)<sub>2</sub>C = PCl (1a) reacts with the disilyltelluride (iPrMe<sub>2</sub>Si)<sub>2</sub>Te (2) leading to the mixed-substituted telluride (Me<sub>3</sub>Si)<sub>2</sub>C = PTeSiMe<sub>2</sub>iPr 3a which reacts with another equivalent of 1a furnishing the tellurobis(phosphaalkene) [(Me<sub>3</sub>Si)<sub>2</sub>C = P]<sub>2</sub>Te (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 (iPrMe<sub>2</sub>Si)<sub>2</sub>C = PCl (1b) reacts with (iPrMe<sub>3</sub>Si)<sub>2</sub>Te furnishing [(iPrMe<sub>2</sub>Si)<sub>2</sub>C = P]<sub>2</sub>Te (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-Me<sub>3</sub>Ph ( = Mes): 7, Ar = 2,4,6-iPr<sub>3</sub>Ph ( = TIP): 8, Ar = 2,4,6-tBu<sub>3</sub>Ph ( = 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 <sup>31</sup>P-NMR. Reactions of elemental tellurium with P-phosphanylphosphaalkenes (Me<sub>3</sub>Si)<sub>2</sub>C = PPR´R´´ 15 - 17 (R´, R´´ = iPr: 15; R´ = iPr, R´´ = tBu: 16; R´, R´´ = tBu: 17) lead to metastable insertion products (Me<sub>3</sub>Si)<sub>2</sub>C = PTePR´R´´ 18 - 20 that decompose with formation of the tellurobisphosphanes (R´R´´P)<sub>2</sub>Te 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 iPr<sub>4</sub>P<sub>2</sub> and bis-phosphanorbornene 26. The tellurium-free products 24 and 26 were characterised by X-ray crystallography.Graphical abstract: <i>P</i>-Tellurium-substituted phosphaalkenes were detected by <sup>31</sup>P- and <sup>125</sup>Te-NMR; they are, in general, thermally labile, leading by loss of tellurium to diphosphanes, such as <b>5a</b> from the tellurobisphosphaalken<b>e 4a</b>.