DEPENDENCE OF COMPLEX STRUCTURE ON LIGAND CONFORMATION IN PALLADIUM(II) COMPLEXES OF THE CROWN THIOETHER LIGANDS 2,5,8-TRITHIA[9]-ORTHO-BENZENOPHANE (TT[9]OB) AND 2,5,8-TRITHIA[9]-META-BENZENOPHANE (TT[9]MB) - STRUCTURES OF PDCL2(TT[9]OB).DMSO AND PDCL2(TT[9]MB)

The tridentate crown thioether ligands 2,5,8-trithia[9]-o-benzenophane, TT[9]OB, and 2,5,8-trithia[9]-m-benzenophane, TT[9]MB, are known to have exodentate conformations in the uncomplexed form. These ligands react with PdCl2(PhCN)2 to give complexes of the general formula PdCl2L, where L = TT[9]OB. H-1 NMR spectra indicate that TT[9]MB acts as a bidentate ligand via two adjacent S atoms forming a single five-membered chelate ring and the third S atom remains exodentate to the macrocyclic ring. Similar spectra for complexes of TT[9]TOB are fluxional at room temperature, suggesting the incorporation of a third endodentate S atom into the coordination sphere. The complex PdCl2(TT[9]MB) crystallized in the space group P2(1)/c with a = 14.411 (2) angstrom, b = 8.247 (1) angstrom, c = 13.749 (2) angstrom, beta = 106.45 (1)-degrees, V = 1567.2 (2), and Z = 4. The structure refined to R = 3.61% and R(w) = 4.07% for 1672 reflections with F(o)2 > 3-sigma(F(o)2). The Pd atom is in a square-planar environment defined by two Cl atoms and two adjacent ligand S atoms (Pd-S1 = 2.259 (2) angstrom and Pd-S2 = 2.266 (2) angstrom), which form a five-membered chelate ring. The third S atom is exodentate to the macrocyclic ring and oriented away from the metal centre at a distance of 5.122 (2) angstrom. The complex PdCl2(TT[9]OB).DMSO crystallized in the space group P2(1)/c with a = 13.636 (5) angstrom, b = 11.005 (3) angstrom, c = 13.911 (4) angstrom, beta = 113.91 (2)-degrees, V = 1908.5 (10), and Z = 4. The structure refined to R = 4.83% and R(w) = 4.65% for 1930 reflections with F(o)2 > 3-sigma(F(o)2). The Pd atom is in a square-planar environment defined by two Cl atoms and two adjacent ligand S atoms (Pd-S1 = 2.259 (3) angstrom and Pd-S2 = 2.266 (3) angstrom), which form a five-membered chelate ring. The third S atom is in an apical position above the PdCl2S2 plane at a distance of 3.076 (3) angstrom.