Main Group Lewis Acid/Base-Stabilised Phosphanylboranes

Abstract

The parent compounds of phosphanylboranes of the type (LA)H2P-BH2(LB) (LA = Lewis acid, LB = Lewis base) stabilised by Lewis acid/Lewis base have been synthesised by using perfluorinated main-group Lewis acids. The Lewis acid-phosphane adducts (C6F5)3BPH3, (C6F5)3BPPhH2 and (C6F5)3GaPPhH2 (3) were used as starting materials, which upon lithiation with nBuLi react with the chlorinated Lewis base borane adduct ClBH2NMe3. The LA/LB stabilisedphosphanylboranes (C6F5)3BPH2BH2NMe3 (1), (C6F5)3BPPhHBH2NMe3 (4) and (C6F5)3GaPPhHBH2NMe3 (5), were obtained via salt elimination reactions. (C6F5)3GaPH2BH2NMe3 (2) was not accessible using this method due to the unavailability of an efficient synthetic route to (C6F5)3GaPH3. The synthesis of 2 could be achieved quantitatively via reaction of PH2BH2NMe3 with (C6F5)3Ga·Et2O. All products were comprehensively characterised by spectroscopic methods and X-ray crystallography. Additionally, the intermediate products (C6F5)3BPH2Li and (C6F5)3GaPPhH2 (3) were spectroscopically characterised.