Oxidative addition of some mono, di or tetra haloalkanes to organoplatinum(II) complexes

Photochemical Oxidation of Pt(IV)Me3(1,2-diimine) Thiolates to Luminescent Pt(IV) Sulfinates

We report the formation of dinuclear complexes from, and photochemical oxidation of, (CH₃)₃-Pt(IV)(N^N) (N^N = 1,2-diimine derivatives) complexes of thiophenolate ligands to the analogous sulfinates (CH₃)₃Pt(N^N)(SO₂Ph) and structural, spectroscopic, and theoretical studies of the latter revealing tunable photophysics depending upon the 1,2-diimine ligands. Electron-rich thiolate and conjugated 1,2-diimines encourage formation of thiolate-bridged dinuclear complexes; smaller 1,2-diimines or electron-poor thiolates favor mononuclear complexes. Photooxidation of the thiolate ligand yields hitherto unreported Pt(IV)-SO₂R complexes, promoted by electron-deficient thiolates such as 4-nitrothiophenol, which exclusively forms the sulfinate complex. Such complexes exhibit expected absorptions due to π-π* ligand transitions of the 1,2-diimines mixed with spin-allowed singlet MLCT (d-π*) at relatively high energy (270-290 nm), as well as unexpected broad, lower energy absorptions between 360 and 490 nm. DFT data indicate that these low energy absorption bands result from excitation of Pt-S and Pt-C σ-bonding electrons to π* orbitals on sulfinate and 1,2-diimine, the latter of which gives rise to emission in the visible range.

Ligand-Mediated C-Br Oxidative Addition to Cycloplatinated(II) Complexes and Benzyl-Me C-C Bond Reductive Elimination from a Cycloplatinated(IV) Complex

Reaction of the Pt(II) complexes [PtMe₂(pbt)], 1a, (pbt = 2-(2-pyridyl)benzothiazole) and [PtMe(C^N)(PPh₂Me)] [C^N = deprotonated 2-phenylpyridine (ppy), 1b, or deprotonated benzo[h]quinoline (bhq), 1c] with benzyl bromide, PhCH₂Br, is studied. The reaction of 1a with PhCH₂Br gave the Pt(IV) product complex [PtBr(CH₂Ph)Me₂(pbt)]. The major trans isomer is formed in a trans oxidative addition (2a), while the minor cis products (2a' and 2a″) resulted from an isomerization process. A solution of Pt(II) complex 1a in the presence of benzyl bromide in toluene at 70 °C after 7 days gradually gave the dibromo Pt(IV) complex [Pt(Br)₂Me₂(pbt)], 4a, as determined by NMR spectroscopy and single-crystal XRD. The reaction of complexes 1b and 1c with PhCH₂Br gave the Pt(IV) complexes [PtMeBr(CH₂Ph)(C^N)(PPh₂Me)] (C^N = ppy; 2b; C^N = bhq, 2c), in which the phosphine and benzyl ligands are trans. Multinuclear NMR spectroscopy ruled out other isomers. Attempts to grow crystals of the cycloplatinated(IV) complex 2b yielded a previously reported Pt(II) complex [PtBr(ppy)(PPh₂Me)], 3b, presumably from reductive elimination of ethylbenzene. UV-vis spectroscopy was used to study the kinetics of reaction of Pt(II) complexes 1a-1c with benzyl bromide. The data are consistent with a second-order S_N2 mechanism and the first order in both the Pt complex and PhCH₂Br. The rate of reaction decreases along the series 1a ≫ 1c > 1b. Density functional theory calculations were carried out to support experimental findings and understand the formation of isomers.

PtSn Nanoalloy Thin Films as Anode Catalysts in Methanol Fuel Cells

Reactions of SnX₂ (X = Cl, Br) with [PtMe₂(bipy)], 1, (bipy = 2,2'-bipyridine), followed by NaBH₄ reduction at the toluene/water interface in the presence or absence of graphene oxide support rendered PtSn nanoalloy thin films. They were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The electrocatalytical activity of the PtSn thin films was investigated in the methanol oxidation reaction. Our studies showed that the PtSn/reduced-graphene oxide (RGO) thin film gave better catalytic results for MOR in comparison to bare PtSn or Pt thin films. A maximum j_f/j_b ratio (j_f and j_b are the maximum current densities in the forward and backward scans, respectively) of 6.77 was obtained for the PtSn/RGO thin film deriving from the 1 + SnBr₂ + NaBH₄ sequence.

Exchange of pyridine and bipyridine ligands in trimethylplatinum(iv) iodide complexes: substituent and solvent effects

Exchange of pyridine ligands with 2,2′-bipyridines in trimethylplatinum(iv) iodide complexes have been studied. Substituent as well as solvent effects on the ligand-exchange studies have also been investigated.

Pt−Me bond cleavage in the reactions of dimethylplatinum(II) complexes containing chelating phosphine ligands with organotin(IV) chlorides

Selective Pt−Me bond activation of dimethylplatinum(II) complexes [PtMe2(PP)] (PP = dppm (bis(diphenylphosphino)methane), dppe (1,2-bis(diphenylphosphino)ethane), dppp (1,3-bis(diphenylphosphino)propane)) was achieved by SnMe2Cl2 to yield the corresponding platinum(II) complexes [PtMeCl(PP)] (PP = dppm, dppe, dppp) and cis-[PtCl2(PP)] (PP = dppm, dppp). On the other hand, the reactions of complexes [PtMe2(PP)] (PP = dppm, dppe, dppp) with SnPh3Cl resulted in the selective cleavage of the Pt−Me bond to afford the methylplatinum(II) complexes [PtMeCl(PP)]. Notably, the reaction of [PtMe2(dppm)] with SnMe2Cl2 and SnPh3Cl also gave the ionic A-frame complex [Pt2Me2(μ-Cl)(μ-dppm)2]Cl. The variable-temperature 1H and 31P NMR spectroscopy shows that the cleavage of the Pt−Me bond occurs very rapidly and the short-lived platinum(IV) intermediate is difficult to detect during the reaction. An explanation is presented on the basis of the nature of the strong π-acceptance of the phosphine ligand, which resulted in the formation of a very unstable platinum(IV) intermediate.