Synthesis and structures of half-sandwich palladium(II) complexes of 1,4,7-trithiacyclononane ([9]aneS(3)) incorporating halide, phosphine and heterocyclic ligands

Reaction of PdCl2 with [9]aneS(3) (1,4,7-trithiacyclononane) in MeCN-CH2Cl2 3:1 v/v) afforded cis-[Pd([9]aneS(3))Cl-2] which can be converted into a range of half-sandwich palladium(II) complexes cis-[Pd([9]aneS(3))Cl(L)]PF6 [L = PPh(3) or P(C6H11)(3)] and cis-[Pd([9]aneS(3))L][PF6](2) {L = 2PPh(3), Ph(3)PCH(2)PPh(2) (dppm), Ph(2)PCH(2)CH(2)PPh(2) (dppe), (Ph(2)PCH(2))(3)CMe, (Ph(2)PCH(2))(2)[Ph(2)P(O)CH2](2)CMe, 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen)). The single-crystal structures of cis-[Pd([9]aneS(3))Cl(PPh(3))]PF6 and cis-[Pd([9]aneS(3))L][PF6](2) {L = 2PPh(3), dppm, (Ph(2)PCH(2))(2)[Ph(2)P(O)CH2]CMe, bipy or phen} have been determined. They all show square-planar co-ordination of Pd-II by L and two S-donors of [9]aneS(3), as well as an additional apical interaction with the third S-donor of [9]aneS(3), Pd ... S-ap 2.990(2) Angstrom for cis-[Pd([9]aneS(3))Cl(PPh(3))]PF6, 2.948(13) Angstrom for cis-[Pd([9]aneS(3))(phen)][PF6](2), 2.877(3) Angstrom; for cis-[Pd([9]aneS(3))[PPh(3))(2)][PF6](2), 2.808(13) Angstrom for cis-[Pd([9]aneS(3))(bipy)][PF6](2), 2.722(4) and 2.768(5) Angstrom for the two independent molecules of cis-[Pd([9]aneS(3)){(Ph(2)PCH(2))(2)[Ph(2)P(O)CH2]CMe}][PF6](2) and 2.698(3) Angstrom for cis-[Pd([9]aneS(3))(dppm)][PF6](2). In the solid state there is, therefore, a general tendency for the third S-donor bf [9]aneS(3) to form a long-range apical interaction giving overall five-co-ordination at Pd-II. The length of this interaction is influenced strongly by the electronic properties of the ligand L and by the overall charge of the complex cation. The redox properties of these complexes are discussed.