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)(3)BPH3, (C6F5)(3)BPPhH2 and (C6F5)(3)GaPPhH2 (3) were used as starting materials, which upon lithiation with nBuLi react with the chlorinated Lewis base borane adduct ClBH2NMe3. The LA/LB stabilised phosphanylboranes (C6F5)(3)BPH2BH2NMe3 (1), (C6F5)3BPPhHBH(2)NMe(3) (4) and (C6F5)(3)GaPPhHBH2NMe3 (5), were obtained via salt elimination reactions. (C6F5)3GaPH(2)- BH2NMe3 (2) was not accessible using this method due to the unavailability of an efficient synthetic route to (C6F5)(3)GaPH3. The synthesis of 2 could be achieved quantitatively via reaction of PH2BH2NMe3 with (C6F5)(3)Ga center dot Et2O. All products were comprehensively characterised by spectroscopic methods and X-ray crystallography. Additionally, the intermediate products (C6F5)(3)BPH2Li and (C6F5)(3)GaPPhH2 (3) were spectroscopically characterised. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)