Lanthanide Ion Complexes of Calixarenes. VII. Bimetallic Lanthanide Complexes of p-t-Butylcalix[8]arene From Dimethyl Sulfoxide Solutions

Reaction of Ln (ClO4)3.x dmso ( dmso denotes dimethyl sulfoxide ) with a warm p-t- butylcalix [8] arene (L) slurry in acetone/ dmso yields crystalline 2:1 Ln/ligand adducts, characterized as dmso olvates and established to be [Ln2(L-6H)( dmso )5].~2dmso by single- crystal X-ray studies at c. 295 K for Ln = La, Eu , Tm and Lu. All complexes are isomorphous , orthorhombic, Pcnb, a ˜ 34, b ˜ 23, c ˜ 14 ?, Z 4, with a similar complex molecule in each case, one half comprising the asymmetric unit; the second half is generated by a crystallographic twofold axis. The two lanthanide atoms are encompassed by the macrocycle and are eight coordinate, involving phenolic and dmso O-donor atoms, five of the former (two bridging) and three of the latter (one bridging). The array closely resembles that found in analogous dmf solvent adducts: the bridging dmso lies on the crystallographic twofold axis through the complex, its peripheral atoms being modelled by disorder.