Synthesis and structure of half-sandwich palladium(II) complexes of 1,4,7-trithiacyclononane ([9]aneS3) incorporating halide, phosphine and heterocyclic ligands

Abstract

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 Pd^II 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 ⋯ S_ap 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 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.