Helical Structures Featuring Thiolato Donors - Metallofoldamers: Supramolecular Architectures from Helicates to Biomimetics - page 160

SH

SH

SH SH

SH

SH

SH

SH

SH

SH

SH

HN O

HN O

O

O

SH

NH

NH

NH

NH

SH O

O

SH HN O

HN O

SH SH

SH SH

SH

SH

SH SH

SH

SH

H 4 - 1 H 4 - 2 H 4 - 3 H 4 - 4 H 4 - 5 H 4 - 6

HS

HS

HS

HS

HS O

HS O

HN O

= R

HN

NH

HS SH

NH O

NH HS SH

O

O NH HN

NH

SH N

O N NHR

SH

SH

N

RHN

SH

H 6 - 7 H 6 - 8 H 6 - 9

Figure 5.3 Bis- and tris(benzene-o-dithiol) ligands.

Apart from ligands containing exclusively benzene- o -dithiol groups, mixed benzene- o -
dithiol/catechol ligands like H 4 - 10 -H 4 - 13 (Figure 5.4) have been prepared from 2,3-
dimercaptobenzoic acid and functionalized catechol using standard protection group
chemistry [29].

5.2 Coordination Chemistry of Bis- and Tris(Benzene-o-Dithiolato) Ligands

5.2.1 Mononuclear Chelate Complexes
Depending on the topology of the ligand and the preferred coordination geometry of a
given metal ion, polydentate ligands can form several different coordination compounds.
Ligands with long and flexible backbones, such as H 4 - 14 and H 4 - 15 , react with Co III ions
under the formation of mononuclear chelate complexes. Both complexes (NEt 4 )[Co( 14 )]
and (NEt 4 )[Co( 15 )] have been obtained in a thermodynamically controlled ligand transfer
reaction utilizing (NEt 4 ) 2 [CoCl 4 ] and the halophilic di(titanocene) complexes of 14 4 and
15 4 (Scheme 5.2) [30].