Platinum(II) complexes of the tridentate thioether ligands RS(CH2)3S(CH2)3SR (R = Et, iPr, Ph). Structures of [PtCl(iPrS(CH2)3S(CH2)3SiPr)][BF4], [Ptl(PhS(CH2)3S(CH2)2SPh)][BF4], and

Article abstract of DOI:10.1139/v96-156

The tridentate thioether ligands RS(CH₂)₃S(CH₂)₃SR (L¹, R = Et; L², R = iPr, L³, R = Ph) were synthesized by nucleophilic addition of thiolate, SR^-, to the ditosylate TsO(CH₂)₃S(CH₂)₃OTs. The complexes [PtX(Lⁿ)][BF₄] were prepared by displacement of 1,5-COD from [PtX₂(1,5-COD)] (X = Cl, I) in the presence of one equivalent of AgBF₄ and one equivalent of thioether ligand. [PtCl(L²)][BF₄] crystallized in the monoclinic space group P2₁/c with a = 10.409(6), b = 14.180(4), c = 13.726(8) angstrom, β = 104.49(4)°, V = 1961(2) angstrom³, and Z = 4. The structure refined to R = 5.62% and R_w = 6.86% for 2121 reflections with F₀² > 3σ(F₀²). [PtI(L³)][BF₄ crystallized in the monoclinic space group P2_l/n with a = 13.415(4), b = 12.350(5), c = 14.316(5) angstrom, β = 107.48(3)°, V = 2262(1) angstrom³, and Z = 4. The structure refined to R = 4.85% and R_w 6.33% for 2168 reflections with F₀² > 3σ(F₀²). In both compounds, the thioether ligand acts as a tridentate chelator occupying three of the four sites of the square-planar Pt(II) complex. Variable temperature ¹³C{¹H} NMR verified that there are three possible stereoisomers for these complexes resulting from inversion at sulphur: meso-A, meso-B, and racemic. Thermodynamic parameters were calculated for the interconversion among isomers of [PtCl(L²)][BF₄] by a full line-shape analysis. Removal of chloride ligand from [PtCl(L²)][BF₄] with Ag⁺ in the presence of PPh₃ yielded the phosphine adduct [Pt(PPh₃)(L²)][BF₄]₂, which crystallized in the triclinic space group PI with a = 13.266(3), b = 11.315(2), c = 13.970(2) angstrom, α = 106.04(2)°, β = 84.95(2)°, γ = 86.56(2)°, V = 1999.7(7) angstrom³, and Z = 2. The structure refined to R = 4.22% and R_w = 5.38% for 4493 reflections with F₀² > 3σ(F₀²). Unlike the two halide complex structures, which crystallized in the meso-B form, [Pt(PPh₃)(L²)][BF₄]₂ crystallized in the racemic form.