Relieving Steric Strain at Octahedral Platinum(IV): Isomerization and Reductive Coupling of Alkyl and Aryl Chlorides

Oxidation of monocyclometalated platinum­(II) complexes results in octahedral platinum­(IV) complexes. Depending on the substitution, two different reactions occur: either a simple isomerization, resulting in the exchange of ligand positions, or a reductive coupling of aryl chloride. With a doubly cyclometalated complex, stability of the oxidized form is dependent on isomeric form: whereas the <i>trans</i> isomer is robust, being manipulable in air at room temperature, the <i>cis</i> isomer decomposes at −20 °C and above. Reductive coupling at this <i>cis</i> isomer is 100% selective for alkyl chloride over aryl chloride and is suggested to be a concerted process

Relieving Steric Strain at Octahedral Platinum(IV): Isomerization and Reductive Coupling of Alkyl and Aryl Chlorides

Oxidation of monocyclometalated platinum­(II) complexes results in octahedral platinum­(IV) complexes. Depending on the substitution, two different reactions occur: either a simple isomerization, resulting in the exchange of ligand positions, or a reductive coupling of aryl chloride. With a doubly cyclometalated complex, stability of the oxidized form is dependent on isomeric form: whereas the <i>trans</i> isomer is robust, being manipulable in air at room temperature, the <i>cis</i> isomer decomposes at −20 °C and above. Reductive coupling at this <i>cis</i> isomer is 100% selective for alkyl chloride over aryl chloride and is suggested to be a concerted process

Oxidative Addition of MeI to a Rollover Complex of Platinum(II): Isolation of the Kinetic Product

A pair of new Pt­(II)/Pt­(IV) 2,2′-bipyridine cyclometalated rollover complexes have been synthesized and characterized. [Pt­(bpy-H)­(CH₃)­(PMe₃)] (<b>1</b>), where bpy-H = κ²<i>N</i>,<i>C</i>-2,2′-bipyridine, was obtained from the electron-rich precursor <i>cis</i>-[Pt­(CH₃)₂(DMSO)₂] with a one-pot, two step synthesis; its reactivity has been tested with CH₃I, giving the corresponding Pt­(IV) complex <i>cis</i>-[Pt­(bpy-H)­(CH₃)₂(I)­(PMe₃)] (<b>2</b>), which was fully characterized. Crystals suitable for X-ray analysis were obtained and allowed the determination of the structure of isomer <b>2A</b> which is the product of the <i>trans</i> addition of CH₃I, usually thought of as the <i>kinetic</i> product

Oxidative Addition of MeI to a Rollover Complex of Platinum(II): Isolation of the Kinetic Product

A pair of new Pt­(II)/Pt­(IV) 2,2′-bipyridine cyclometalated rollover complexes have been synthesized and characterized. [Pt­(bpy-H)­(CH₃)­(PMe₃)] (<b>1</b>), where bpy-H = κ²<i>N</i>,<i>C</i>-2,2′-bipyridine, was obtained from the electron-rich precursor <i>cis</i>-[Pt­(CH₃)₂(DMSO)₂] with a one-pot, two step synthesis; its reactivity has been tested with CH₃I, giving the corresponding Pt­(IV) complex <i>cis</i>-[Pt­(bpy-H)­(CH₃)₂(I)­(PMe₃)] (<b>2</b>), which was fully characterized. Crystals suitable for X-ray analysis were obtained and allowed the determination of the structure of isomer <b>2A</b> which is the product of the <i>trans</i> addition of CH₃I, usually thought of as the <i>kinetic</i> product

Selective Imaging of Discrete Polyoxometalate Ions on Graphene Oxide under Variable Voltage Conditions

Monosubstituted lacunary Keggin [CoSiW₁₁O₃₉]^6– ions on graphene oxide (GO) were used in a comparative imaging study using aberration corrected transmission electron microscopy at two different acceleration voltages, 80 and 200 kV. By performing a set of static and dynamical studies, together with image simulations, we show how the use of lower voltages results in better stability and resolution of the underlying GO support while the use of higher voltages permits better resolution of the individual tungsten atoms and leads to less kinetic motion of the cluster, thus leading to a more accurate identification of cluster orientation and better stability under dynamical imaging conditions. Applying different voltages also influences the visibility of both GO and the lighter Co at lower or higher voltages, respectively

Acclimatization study of <i>Tagetes lucida</i> L. in Egypt and the chemical characterization of its essential oils

<p>Seeds of <i>Tagetes lucida</i> were imported to Egypt from Canada and propagated under greenhouse conditions in peat moss media. Soil was sandy in texture and the irrigation system was dripping irrigation. The growth parameters were determined at five successive plant ages, fresh and dry weights of herb were determined at three successive plant ages. The yield of aerial parts after 175 days, was about 7.5 Mg/ha. The essential oil (EO) was extracted by hydro-distillation for three hours with a yield of about 0.5% (w/v). The EO of each sample was subjected to gas-chromatography/mass spectrometry analyses to study the chemical composition. The main component of the EO was identified as methyl chavicol which matched over 90% of the whole composition. Chlorophyll a and carotenes increased with increasing plant age in both sites and seasons. Flavonoids decreased with the development of plant age, while the opposite was true with coumarines content.</p

Resolving the Nanoscale Morphology and Crystallographic Structure of Molecular Thin Films: F₁₆CuPc on Graphene Oxide

Electron microscopy and diffraction are used to examine the nanoscale structure and molecular orientation in molecular films down to nominally monolayer thickness. The films studied consist of the planar n-type molecular semiconductor copper hexadecafluorophthalocyanine (F₁₆CuPc) directly deposited onto graphene oxide (GO) membranes by organic molecular beam deposition. The graphene oxide support crucially provides the strength and low background required to analyze the crystal structure and morphology of even nominally monolayer thick films and is of relevance for molecular electronic applications. The crystal structure of the F₁₆CuPc polymorph is solved by X-ray diffraction of single crystals and used to analyze the electron diffraction patterns from the thin-films, revealing that the F₁₆CuPc molecules assemble with their molecular plane oriented perpendicular to the GO. There is no evidence for changes in the unit cell with film thickness, although the thinnest films show the greatest disorder in molecular packing. Direct deposition of molecular materials on low contrast and relevant substrates combined with electron and scanning probe microscopy is thus shown to be a powerful technique for elucidating structure in nanostructured organic thin films

Heterobimetallic Rollover Derivatives

Heterobimetallic complexes with metal centers connected by a small delocalized ligand constitute an interesting class of compounds. Here we report that starting from the mononuclear platinum­(II) rollover complexes [Pt­(bipy-H)­(L)­Cl] (bipy-H = 2,2′-bipyridine C(3′)-N cyclometalated, L= DMSO, PPh₃) a second rollover cyclometalation may produce a series of Pt­(II)/Pd­(II) heterobimetallic complexes where the two metals are linked by the planar, highly delocalized, doubly deprotonated 2,2′-bipyridine

Heterobimetallic Rollover Derivatives

Heterobimetallic complexes with metal centers connected by a small delocalized ligand constitute an interesting class of compounds. Here we report that starting from the mononuclear platinum­(II) rollover complexes [Pt­(bipy-H)­(L)­Cl] (bipy-H = 2,2′-bipyridine C(3′)-N cyclometalated, L= DMSO, PPh₃) a second rollover cyclometalation may produce a series of Pt­(II)/Pd­(II) heterobimetallic complexes where the two metals are linked by the planar, highly delocalized, doubly deprotonated 2,2′-bipyridine

Deoxygenation of Graphene Oxide: Reduction or Cleaning?

We show that the two-component model of graphene oxide (GO), that is, composed of highly oxidized carbonaceous debris complexed to oxygen functionalized graphene sheets, is a generic feature of the synthesis of GO, independent of oxidant or protocol used. The debris present, roughly one-third by mass, can be removed by a base wash. A number of techniques, including solid state NMR, demonstrate that the properties of the base-washed material are independent of the base used and that it contains similar functional groups to those present in the debris but at a lower concentration. Removal of the oxidation debris cleans the GO, revealing its true monolayer nature and in the process increases the C/O ratio (i.e., a deoxygenation). By contrast, treating GO with hydrazine both removes the debris and reduces (both deoxygenations) the graphene sheets