A Unique Rare-Earth Cluster within a Calixarene Sandwich: Parallels in the Chemistry of Cyclosiloxanes and Calixarenes

Abstract

Determination of the crystal structure of a complex obtained by the reaction of the dimethyl sulfoxide (dmso) solvate of neodymium(III) nitrate with p-t-butyltetrathiacalix[4]arene in dimethylformamide (dmf) in the presence of base showed a regular, planar cluster of four neodymium atoms bridged by a hydroxyl group to be sandwiched between two fully deprotonated calixarene moieties. The sulfur and oxygen donor atoms of the calixarenes are both involved in coordination to the rare-earth atoms. Both dmf and dmso are found as ligands on neodymium but occupation of the calixarene cavity is by dmf only. The proposed overall stoichiometry of the complex is [Nd₄(OH){(p-t-butyltetrathiacalix[4]arene-4H)(dmf)}₂(dmf)₆(dmso)₂](NO₃)₃.3H₂O.