The Proton Cryptate of Hexaethylenetetramine.

The next higher homologue of hexamethylenetetramine was synthesized as the proton cryptate H @1⋅Br (shown schematically), and its X-ray structure determined. The proton trapped by the lone pairs accumulated at the center of the T-symmetric tetraaza cage could not be exchanged or removed, even after heating for three days in 3 M NaOD.