A New Mode of Metal Encapsulation

All ten oxygen atoms of the acyclic oligomer 1 c participate in the coordination of Ba2⊕ in the “scorpion” complex 1c · Ba(SCN)2 · Me2CO. The eleventh coordination site is occupied by the acetone molecule. A further characteristic of the complex are strong OHċN hydrogen bonds to the thiocyanate counterion. The ligands 1 also exhibit a high selectivity for cations with ionic radii of 1.2–1.3 Å, which could be explained with the help of molecular modeling studies. (Figure Presented.) Copyright © 1990 by VCH Verlagsgesellschaft mbH, German