C-3-symmetric azaphosphatranes

C-3-Symmetric azaphosphatranes, (3S, 7S,10S)-2,3,7,8,9,10-hexamethyl-2,8,9- triaza-5-azonial-lambda(5)-phosphabicyclo[3.3.3]undecane chloride and (3S,7 S,10S)-3,7,10-triisopropyl-2,8,9-trimethyl -2,8,9-triaza-5-azonia-1-lambda( 5)-phosphabicyclo[3.3.3]undecane chloride, have been prepared starting from the corresponding chiral tripodal tetraamines and chlorobis-(diethylamino) phosphane. The compounds are weak acids which are not fully deprotonated by potassium tert-butoxide. Density functional calculations of the compounds and their conjugate bases demonstrate that the weak acidity originates in a conformational change upon deprotonation leading to substantial steric rep ulsion.