Synthesis and structure 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]aneS3(1,4,7-trithiacyclononane) in MeCN–CH2Cl2(3 : 1 v/v) afforded cis-[Pd([9]aneS3)Cl2] which can be converted into a range of half-sandwich palladium(II) complexes cis-[Pd([9]aneS3)Cl(L)]PF6[L = PPh3 or P(C6H11)3] and cis-[Pd([9]aneS3)L][PF6]2{L = 2PPh3, Ph2PCH2PPh2(dppm), Ph2PCH2CH2PPh2(dppe), (Ph2PCH2)3CMe, (Ph2PCH2)2[Ph2P(O)CH2]2 CMe, 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen)}. The single-crystal structures of cis-[Pd([9]aneS3)Cl(PPh3)]PF6 and cis-[Pd([9]aneS3)L][PF6]2{L = 2PPh3, dppm, (Ph2PCH2)2[Ph2P(O)CH2]CMe, bipy or phen} have been determined. They all show square-planar co-ordination of PdII by L and two S-donors of [9]aneS3, as well as an additional apical interaction with the third S-donor of [9]aneS3, Pd ⋯ Sap 2.990(2)Å for cis-[Pd([9]aneS3)Cl(PPh3)]PF6, 2.948(13)Å for cis-[Pd([9]aneS3)(phen)][PF6]2, 2.877(3)Å for cis-[Pd([9]aneS3)(PPh3)2][PF6]2, 2.808(13)Å for cis-[Pd([9]aneS3)(bipy)][PF6]2, 2.722(4) and 2.768(5)Å for the two independent molecules of cis-[Pd([9]aneS3){(Ph2PCH2)2[Ph 2P(O)CH2]CMe}][PF6]2 and 2.698(3)Å for cis-[Pd([9]aneS3)(dppm)][PF6]2. In the solid state there is, therefore, a general tendency for the third S-donor of [9]aneS3 to form a long-range apical interaction giving overall five-co-ordination at PdII. 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.