The laterally nonsymmetric aza cryptand L o readily forms mononuclear inclusion complexes with metal ions like Cu II , Ni II , Ag I , Tl I , and so forth. However, when the secondary amines present in the three bridges are substituted by a cyanomethyl group to yield a new cryptand L, its metal-binding properties are drastically altered. Thus, while L o binds Ag I at the tren end, showing AgN 4 coordination, in L, the bridgehead nitrogen atoms are pulled inside to form a two-coordinate complex of Ag I and none of the O or N atoms present in the three bridges are involved in coordination. This is probably the first example where the two bridgehead atoms are pulled inside to the maximum to bind the metal ion. Likewise, the Tl I ion shows TlN 4 coordination with L o , while in L it is loosely bound at the tren end, showing TlN 3 coordina-