Homogeneous catalysis of platinum(II) complexes in photochemical hydrogen production from water

Group 10 metal(II) complexes of H2tbu-salen (H2tbu-salen = N,N'-bis(3',5'-di-tert-butylsalicylidene)ethylenediamine) and H2tbu-salcn (H2tbu-salcn = N,N'-bis(3',5'-di-tert-butylsalicylidene)-1,2-cyclohexanediamine) containing two 2,4-di(tert-butyl)phenol moieties, [Ni(tbu-salen)] (1a), [Ni(tbu-salcn)] (1b), [Pd(tbu-salen)] (2a), [Pd(tbu-salcn)] (2b), and [Pt(tbu-salen)] (3), were prepared and structurally characterized by X-ray diffraction, and the electronic structures of their one-electron-oxidized species were established by spectroscopic and electrochemical methods. All the complexes have a mononuclear structure with two phenolate oxygens coordinated in a very similar square-planar geometry. These complexes exhibited similar absorption spectra in CH2Cl2, indicating that they all have a similar structure in solution. Cyclic voltammograms of the complexes showed a quasi-reversible redox wave at E1/2 = 0.82-1.05 V (vs Ag/AgCl), corresponding to formation of the relatively stable one-electron-oxidized species. The electrochemically oxidized or Ce(IV)-oxidized species of 1a, 2a, and 3 displayed a first-order decay with a half-life of 83, 20, and 148 min at -20 degrees C, respectively. Ni(II) complexes 1a and 1b were converted to the phenoxyl radicals upon one-electron oxidation in CH2Cl2 above -80 degrees C and to the Ni(III)-phenolate species below -120 degrees C. The temperature-dependent conversion was reversible with the Ni(III)-phenolate ground state and was found to be a valence tautomerism governed by the solvent. One-electron-oxidized 1b was isolated as [Ni(tbu-salcn)]NO3 (4) having the Ni(II)-phenoxyl radical ground state. One-electron-oxidized species of the Pd(II) complexes 2a and 2b were different from those of the Ni(II) complexes, the Pd(II)-phenoxyl radical species being the ground state in CH2Cl2 in the range 5-300 K. The one-electron-oxidized form of 2b, [Pd(tbu-salcn)]NO3 (5), which was isolated as a dark green powder, was found to be a Pd(II)-phenoxyl radical complex. On the other hand, the ESR spectrum of the one-electron-oxidized species of Pt(II) complex 3 exhibited a temperature-independent large g anisotropy in CH2Cl2 below -80 degrees C, while its resonance Raman spectrum at -60 degrees C displayed nu8a of the phenoxyl radical band at 1600 cm-1. These results indicated that the ground state of the Pt(II)-phenoxyl radical species has a large distribution of the radical electron spin at the Pt center. One-electron oxidation of 3 gave [Pt(tbu-salen)]NO3 (6) as a solid, where the oxidation state of the Pt center was determined to be ca. +2.5 from the XPS and XANES measurements.

Syntheses and Electronic Structures of One-Electron-Oxidized Group 10 Metal(II)−(Disalicylidene)diamine Complexes (Metal = Ni, Pd, Pt)

In this article, we provide a detailed description of the synthesis and properties of Pt dendrimerencapsulated nanoparticles (DENs) prepared using sixth-generation, hydroxyl-terminated, poly(amidoamine) (PAMAM) dendrimers (G6-OH) and three different PtCl4 2- /G6-OH ratios: 55, 147, and 240. Results obtained from UV-vis spectroscopy, X-ray photoelectron spectroscopy, electron microscopy, X-ray absorption spectroscopy, and high-energy X-ray diffraction show that only a fraction of the Pt 2+ /dendrimer precursors are reduced by BH4 - and that the reduction process is highly heterogeneous. That is, after reduction each Pt 2+ /dendrimer precursor complex is either fully reduced, to yield a DEN having a size and structure consistent with the original PtCl4 2- /dendrimer ratio used for the synthesis, or the precursor is not reduced at all. This result is consistent with an autocatalytic process that entails slow formation of a nascent catalytic Pt seed within the dendrimer, followed by rapid, catalytic reduction of nearby Pt 2+ ions. Details concerning the formation of the Pt 2+ /dendrimer precursor are also discussed.

/pdf/synthesis-and-characterization-of-pt-dendrimer-encapsulated-1ggqxu2vu4.pdf

Synthesis and Characterization of Pt Dendrimer-Encapsulated Nanoparticles: Effect of the Template on Nanoparticle Formation

Neatly wrapped up: alternately stacked square-planar platinum(II) complexes inside a dinuclear coordination cage were prepared to give a discrete and soluble Pt(5) -array of the Magnus' salt type. Characterization of the complex in solution was complemented by an X-ray crystal structure of {[Pt(pyridine)(4)]⋅ [PtCl(4)](2) @Cage}; this structure showed the linear, pentanuclear array within the cages and their circular packing into a hollow tubular superstructure.

Stacked Platinum Complexes of the Magnus’ Salt Type Inside a Coordination Cage

Regulation of metal–metal interactions and chromic phenomena of multi-decker platinum complexes having π-systems

The first mixed-valent octanuclear platinum blue compounds with bridging acetamidate and 2-fluoroacetamidate ligands, [(H 3 N) 2 Pt(CH 3 CONH) 2 Pt(NH 3 ) 2 ] 4 (NO 3 ) 10 .4H 2 O and [(H 3 N) 2 Pt(CH 2 FCONH) 2 Pt(NH 3 ) 2 ] 4 (NO 3 ) 8.66 .4H 2 O, are crystallographically characterized.

Syntheses, Crystal Structures, and Electronic, ESR, and x-ray Photoelectron Spectra of Acetamidate-and 2-Fluoroacetamidate-Bridged Mixed-Valent Octanuclear Platinum Blues

We studied the adhesion of a silicon dioxide film, formed from silane and nitrous oxide gas by plasma‐enhanced chemical vapor deposition, to a polycarbonate substrate and the bonding between the film and the substrate by x‐ray photoelectron spectroscopy Adhesion of the SiO2 film to the polycarbonate increases with increasing SiH4 flow rate All SiO2 film squares produced at a SiH4 flow rate of 10 standard cm3 min−1 exhibited good adhesion to the substrate An analysis of the x‐ray photoelectron spectra indicates that more phenyl groups are decomposed as adhesion increases The bonding between the SiO2 film and the polycarbonate substrate is discussed on the basis of x‐ray photoelectron spectroscopy The Si–O–C bonding between SiO2 and polycarbonate results in good adhesion between the film and the substrate

Yushi Shichi

Papers

Syntheses, Crystal Structures, and Electronic, ESR, and x-ray Photoelectron Spectra of Acetamidate-and 2-Fluoroacetamidate-Bridged Mixed-Valent Octanuclear Platinum Blues

Adhesion between polycarbonate substrate and SiO2 film formed from silane and nitrous oxide by plasma‐enhanced chemical vapor deposition