ADVENTURES IN CRYSTAL ENGINEERING†

 

Edward R. T. Tiekink

 

Department of Chemistry, National University of Singapore, Singapore 117543

 

Abstract

An overview of the structural systematics of four heavy-element systems is given, namely triorganotincarboxylates (R₃Sn(O₂CR’)), zinc and mercury xanthates (A(S₂COR)₂; A = Zn and Hg) and bismuth xanthates (Bi(S₂COR)₃).  It will be demonstrated that there exists a fascinating range of structural diversity for these compounds, including differences in coordination number and molecular geometry.  Difference in structure in two of the systems, i.e. R₃Sn(O₂CR’) and Zn(S₂COR)₂, are correlated with the nature of the tin- and ligand-bound R groups, respectively.  This suggests a new design concept for crystal engineering, i.e. steric control over molecular aggregation.  However, this concept is shown not to be universal by an analysis of the related Hg(S₂COR)₂ structures.  The adoption of different motifs for Bi(S₂COR)₃ influences the nature of generated nanoparticles and thereby demonstrates the importance of structure of the precursor material.  Finally, an example of the utility of non-traditional intermolecular ‘aurophilic’ (i.e. Au…Au) interactions upon polymer formation is demonstrated for a pair of phosphinegold(I) thiolate structures.