Helical Structures Featuring Thiolato Donors - Metallofoldamers: Supramolecular Architectures from Helicates to Biomimetics - page 157

5
Helical Structures Featuring Thiolato
Donors
F. Ekkehardt Hahn and Dennis Lewing
Institut fur Anorganische und Analytische Chemie, Westf alische
Wilhelms-Universitat Munster, Germany
5.1 Introduction
Metallosupramolecular structures became a field of intensive research after Lehn et al.
demonstrated the spontaneous formation of dinuclar helicates from bipyridine and Cu I
[1]. In general, metallosupramolecular chemistry deals with the construction of highly
complex functional chemical systems which are held together by noncovalent forces [2].
Spontaneous self-assembly reactions leading to metallosupramolecular assemblies have
attracted much interest over the last decades [3] and different structural motifs have been
obtained by transition metal-directed self-assembly reactions [4].
Metallohelicates belong to the first metallosupramolecular assemblies studied in detail
[1]. Most of these helicates contain ligands with N- or O-donors like oligopyrimidines or
catecholates [5]. The coordination chemistry of related polydentate ligands featuring sul-
fur donors has been less studied. We became interested in the coordination chemistry of
bis- and tris(benzene- o -dithiolato) and mixed benzene- o -dithiolato/catecholato ligands.
Such ligands can exhibit an interesting and diverse coordination chemistry.
In hexacoordinated complexes, octahedral ( OC ) coordination is by far the most com-
mon coordination geometry encountered. This is mainly due to the minimization of steric
interactions between the ligands, and OC geometry often leads to a maximization of the
ligand field stabilization energy. The second, less common structural type associated
with the coordination number 6 is trigonal-prismatic ( TP ) coordination geometry.