Stability of organo-mercury, -thallium, -tin and -lead complexes with anionic and neutral ligands

A decacationic ferrocene-based metallostar

Decacationic metallostars have been prepared by the reaction of permercurated ferrocene FeC₁₀(HgO₂CCF₃)₁₀ with superacidic (C₅F₅NH)(SbF₆) (pK _a = -11 estimated in H₂O) in multigram scale. In the resulting compound, [FeC₁₀Hg₁₀(NC₅F₅) _n ][SbF₆]₁₀, the labile pentafluoropyridine ligands are readily displaced by acetonitrile (MeCN) or tetrahydrothiophene (THT). In the X-ray structure of [FeC₁₀Hg₁₀(THT)₁₀][SbF₆]₁₀·24 MeCN no cation-anion contacts between mercury and fluorine were observed. Moreover, cyclic voltammetry measurements of [FeC₁₀(Hg(MeCN))₁₀]¹⁰⁺ and [FeC₁₀(Hg(THT))₁₀]¹⁰⁺ revealed a (quasi)reversible one-electron oxidation of Fe(ii) to Fe(iii). From the reaction of [FeC₁₀(Hg(MeCN))₁₀]¹⁰⁺ with MoF₆ as oxidant the ferrocenium cation [FeC₁₀(Hg(MeCN))₁₀]¹¹⁺ was obtained and characterized via single crystal XRD. These electrophilic metallostars are promising potential building blocks for the synthesis of dendritic architectures containing a robust, tenfold functionalized ferrocene core.

Synthesis of the complexes [PdCIR(cod)] (R = benzyl, ethyl; cod = 1,5-cyclooctadiene). β-Elimination from [PdCIEt(cod)] to give the η1,η2 and η3 isomers of [Pd2(μ-Cl)2(C8H13)2]

Treatment of [PdCl2(cod)] with tetrabenzyltin gives the benzylpalladium complex [PdCl(CH2Ph)(cod)] (cod = 1,5-cyclooctadiene), 1a, whose structure has been determined by X-ray crystallography. It adopts approximate square-planar geometry, with the double bonds perpendicular to the square plane. The corresponding ethylpalladium derivative 1b has been prepared by a similar method, but it is considerably less stable. It decomposes by (β-elimination to produce ethene and a transient hydride complex, which either undergoes migratory insertion to give [Pd2(μ-Cl)2(η1,η2-C8H13)2], 2a, or dinuclear reductive elimination with a second molecule of 1b to produce ethane, [PdCl2(cod)], free cyclooctadiene, and palladium metal. Complex 2a has also been prepared by reaction of [PdCl2(cod)] with NaBH4. At higher temperatures 2a converts to an equilibrium mixture with its η3-allyl isomer, 2b. Reactions of [PdCl2(cod)] or K2PdCl4 in the presence of cyclooctadiene in aqueous solution to produce 2a or 2b have also been investigated. Key words: palladium, diene complexes, allyl complexes, isomerization, β-elimination.

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], [PtI(PhS(CH2)3S(CH2)2SPh)][BF4], and [Pt(PPh3)(iPrS(CH2)3S(CH2)3SiPr)][BF4]2•CH2Cl2

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) Å, β = 104.49(4)°, V = 1961(2) Å3 and Z = 4. The structure refined toR = 5.62% and Rw = 6.86% for 2121 reflections with F02 > 3σ(Fo2). [PtI(L3)][BF4] crystallized in the monoclinic space group P21/n with a = 13.415(4), b = 12.350(5), c = 14.316(5) Å, β = 107.48(3)°, V = 2262(1) Å3 and Z = 4. The structure refined to R = 4.85% and Rw = 6.33% for 2168 reflections with Fo2 > 3σ(Fo2). 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 [Formula: see text] with a = 13.266(3), b = 11.315(2), c = 13.970(2) Å, α = 106.04(2)°, β = 84.95(2)°, γ = 86.56(2)°, V = 1999.7(7) Å3 and Z = 2. The structure refined to R = 4.22% and Rw = 5.38% for 4493 reflections with Fo2 > 3σ(Fo2). Unlike the two halide complex structures, which crystallized in the meso-B form, [Pt(PPh3)(L2][BF4]2 crystallized in the racemic form. Key words: tridentate thioether ligand, crystal structure, platinum(II) halide, dynamic NMR spectroscopy.