Modulating the propeller-like shape of a tripodal C(CH2PPh2)3 fragment by the size of the substituent at the pivotal carbon atom in macrobicyclic tri-λ5-phosphazenes
The chiral macrobicyclic tri-λ5-phosphazenes formed by tripod–tripod coupling of tris(3-azidobenzyl)amines and 1,1,1-tris[(diphenylphosphino)methyl]methanes present helical topologies as a result of combining two propeller-shaped tripodal fragments with the same sense of twist. The introduction of a series of Rpiv substituents of increasing size at the pivotal carbon of the lower tert-butane fragment