Beiträge zur Chemie des Bors, 212. Azaphosphoniaborataborolidine und ihre Thermolyse zu Diazaphosphadiborinanen

Contributions to the Chemistry of Boron, 212 [1] . – Azaphosphoniaborataborolidines and their Thermolysis to Diazaphosphadiborinanes Me 3 SiN = PN(SiMe 3 ) 2 ( 1 ) adds Lewis‐acidic diborylmethanes CH 2 [B(Cl)X] 2 ( 6a–d , X = Cl, Me, Ph, Mes) to yield the five‐membered azaphosphoniaborataborolidines 9a–d by haloboration and formation of an intramolecular coordinative phosphorus boron bond. However, the less Lewis‐acidic diborylmethane CH 2 [B(Cl)NMe 2 ] 2 does not react with 1 . NMR studies on 9 exhibit conformational dependence of the ring system on the bulkiness of X, suggesting a decreasingly folded structure for X = Mes > Ph > Me and a planar ring for X = Cl, the latter proven by an X‐ray structure analysis. 9 a, b rearrange their ring framework on heating with elimination of Me 3 SiCl to give diazaphosphadiborinanes 7 . Compound 7b shows the typical reactions of a diamino(chloro)phosphane: oxidation by S 8 yields the corresponding phosphane sulfide 17 while AlCl 3 abstracts a chloride ion with formation of a phosphenium tetrachloroaluminate 13 . In the reaction of 7b with BBr 3 halogene exchange (to 16 ) dominates, while a phosphane borane adducts ( 15 ) is formed in a side reaction only.