METAL-COMPLEXES OF A CALIX[4]ARENE DIAMIDE - SYNTHESES, CRYSTAL-STRUCTURES AND MOLECULAR MECHANICS CALCULATIONS ON [FE(L(1)-2H)][FECL4] AND[ER(L(1)-2H)(PICRATE)] L-25,27-BIS(DIETHYLCARBAMOYLMETHOXY)CALIX[4]ARENE)

Reactions of yl-25,27-bis(diethylcarbamoylmethoxy)calix[4]arene (L(1)) with metal salts have been found to produce 1:1 metal/calixarene comp lexes. The rigid nature of the lower rim of the calix[4]arene in the c one conformation ensures that four donor oxygen atoms are approximatel y coplanar thus ruling out any possibility of orthogonal coordination and restricting the types of metals that form complexes. Complexes wit h Fe(III) and Er(III) are reported and structurally characterised. The crystal structure of the complex [Fe(L(1)-2H)](FeCl4) has been determ ined. The metal coordination sphere shows a trigonal prismatic environ ment with the metal bonded to two phenolic and two ethereal oxygen ato ms at the bottom of the rim and to two carbonyl oxygen atoms. Molecula r mechanics calculations show that the cavity is ideally suited to thi s type of coordination sphere. The lanthanide complex [Er(L(1)-2H) (pi crate)] has a similar structure but the metal is eight coordinate bein g bonded to the six oxygen atoms of the calix[4]arene diamide and also to a bidentate picrate anion.