Synthesis and characterisation of palladium(II) complexes of mixed thioether/oxa ionophores. Crystal structures of [PdCl2([18]aneS(2)O(4))], [Pd([18]aneS(2)O(4))(2)][PF6](2) ([18]aneS(2)O(4)=1,4,7,10-tetraoxa-13,16-dithiacyclooctadecane) and [Pd([18]aneS(3)O(3))(2)][PF6](2) ([18]aneS(3)O(3)=1,4,7-trioxa-10,13,16-trithiacyclooctadecane)

The palladium(il) complexes cis-[PdCl2([18]aneS(2)O(4))], [Pd([18]aneS(2)O(4))(2)][PF6](2) ([18]aneS(2)O(4) = 1,4,7,10-tetraoxa-13,16-dithiacyclooctadecane), [Pd([18]aneS(3)O(3))(2)][PF6](2) ([18]aneS(3)O(3) = 1,4,7-trioxa-10,13,16-trithiacyclooctadecane) and [PdCl([20]aneS(3)O(3))]BPh(4) ([20]aneS(3)O(3) = 1,4,7-trioxa-10,14,18-trithiacycloicosane) have been synthesised and characterised. Reaction of PdCl2 with 1 molar equivalent of [18]aneS(2)O(4) afforded cis-[PdCl2([18]aneS(2)O(4))]; addition of a second equivalent gave the bis complex cation [Pd([18]aneS(2)O(4))(2)](2+). The crystal structure of cis-[PdCl2([18]aneS(2)O(4))] showed the Pd-II in a square-planar co-ordination geometry with mutually cis Cl- ligands, Pd-S(1) 2.276(2), Pd-S(4) 2.2786(14), Pd-CI(1) 2.307(2), Pd-Cl(2) 2.3100(14) Angstrom, CI(1)-Pd-Cl(2) 92.12(5), CI(1)-Pd-S(1) 176.33(5), CI(1)-Pd-S(4) 87.76(5), Cl(2)-Pd-S(1) 91.19(4) Cl(2)Pd-S(4) 179.24(4) and S(1)-Pd-S(4) 88.96(4)degrees. The near-planar macrocycle co-ordinates as a bidentate chelating ligand via the exo oriented S-donor atoms leaving the endo oriented O atoms free. The SCH2CH2S moiety adopts a gauche conformation [S(1)-C(2)-C(3)-S(4) -58.3(4)degrees] with the ethylene bridge occupying part of the macrocyclic cavity. The crystal structure of [Pd([18]aneS(2)O(4))(2)] [PF6](2) showed the Pd-II occupying a crystallographic inversion centre, with square-planar co-ordination by the [18]aneS(2)O(4) ionophores through the thioether S donors, Pd-S(1) 2.3217(14), Pd-S(4) 2.3102(13) Angstrom and S(1)-Pd-S(4) 88.71(5)degrees. The conformation of the macrocycle is very similar to that found in cis-[PdCl2([18]aneS(2)O(4))], with the O atoms in endo orientations. Reaction of PdCl2 with 2 equivalents of [18]aneS(3)O(3) afforded [Pd([18]aneS(3)O(3))(2)][PF6](2) which has the Pd-II occupying a crystallographic inversion centre, with square-planar co-ordination by the [18]aneS(3)O(3) ligands via two of their three thioether S-donor atoms, Pd-S(1) 2.308(2), Pd-S(4) 2.319(2) Angstrom, S(1)-Pd-S(4) 88.33(8)degrees. The structure exhibits some disorder in the polyether/thioether chain which was modelled in terms of two half-occupied orientations. In one component of the disorder the third S-donor atom of each ligand exhibits a long-range apical interaction with the Pd-II, Pd ... S(16) 3.290(2) Angstrom. Reaction of PdCl2 with 1 equivalent of [20]aneS(3)O(3) afforded the monocation [PdCl([20]aneS(3)O(3))](+).