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Influence of the Anion on the Structure of Bis(methylthio)methane Supramolecular Coordination Complexes

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posted on 06.12.2006, 00:00 by Mohamed Osman Awaleh, Antonella Badia, François Brisse
A series of coordination networks has been synthesized by the self-assembly of the small bis(methylthio)methane building block and AgX (X = NO3- (1), ClO4- (2, 3), p-TsO- (4), CF3COO- (5), CF3CF2CF2COO- (6), CF3SO3- (7), C6H5COO- (8), CH3SO3- (9), and HOOCCF2CF2COO- (10)) in order to rationalize the effect of the size of the anions and the ligands upon the structure adopted by the supramolecular coordination network. In complexes 17, each silver(I) is coordinated with sulfur atoms from three different ligands. They form very similar two-dimensional solid-state organizations. The structures consist of layers, made up of Ag and bis(methylthio)methane ligands only, in which the anions complete the tetrahedral coordination of the silver atoms. Upon closer inspection, the neutral 2D networks may be sorted into two distinct classes. Group 1 incorporates the smallest anions, NO3- and ClO4-, whereas the more elongated anions, p-TsO-, CF3COO-, CF3CF2CF2COO-, and CF3SO3-, are found in group 2. The main difference between these groups is in the organization of the neutral layers. In group 1, the repeat unit consists of a large 14-membered metallomacrocycle, whereas in group 2, the metallomacrocycle consists of 10-membered rings. The two polymorphs of the perchlorate complexes are structurally comparable. Dimeric units are the basis for the other three complexes. In benzoate 8, the dimers are formed with two anions. They are linked by ligand molecules to form a 1D polymeric chain that adopts a distorted hexagonal packing. The silver atoms have a distorted triangular bipyramidal coordination and the Ag···Ag distance is 2.911 Å. In complex 9, two ligands each bridge a pair of silver atoms to form a dimer (Ag···Ag = 3.243 Å). A neutral 1D coordination polymer is obtained when anions connect, in a dibridging mode, the silver atoms of adjacent dimers [Ag(CH3SCH2SCH3)]2. Weak hydrogen interactions between chains result in a 3D network. The silver coordination is triangular bipyramidal. Complex 10 is also a 1D coordination polymer with a centrosymmetric dimer. Two ligands and two anions are coordinated to the silver atoms. The Ag···Ag contact is 3.067 Å. A 1D coordination polymer is obtained through H-bonding between carboxylate groups. The stoichiometries of the complexes are independent of the initial metal-to-ligand ratios and are not influenced by the solvent of recrystallization.