Chelating and Bridging Roles of 2-(2-Pyridyl)benzimidazole and Bis(diphenylphosphino)acetylene in Stabilizing a Cyclic Tetranuclear Platinum(II) Complex.

The reaction of complex [Pt(Me)(DMSO)(pbz)], 1, (pbz = 2-(2-pyridyl)benzimidazolate) with [PtMe(Cl)(DMSO)2], B, followed by addition of bis(diphenylphosphino)acetylene (dppac), gave the novel tetranuclear platinum complex [Pt4Me4(μ-dppac)2(pbz)2Cl2], 2, bearing both the pbz and dppac ligands. In this structure, the pbz ligands are both chelating and bridging to stabilize the tetraplatinum framework. The tetranuclear Pt(II) complex was fully characterized by NMR spectroscopy, X-ray crystallography, and mass spectrometry, and its electronic structure was investigated and supported by DFT calculations

Functionalization and solubilization of inorganic nanostructures and carbon nanotubes by employing organosilicon and organotin reagents

Covalent functionalization of nanowires of TiO2, ZnO and Al2O3 has been carried out by employing the organosilicon reagents aminopropyltriethoxysilane and hexadecyltrimethoxysilane (HDTMS). The presence of the organosilane coating was confirmed by electron microscopy, energy dispersive X-ray analysis (EDXA) and IR spectroscopy. HDTMS-coated oxide nanowires give stable dispersions in CCl4 and toluene. Nanoparticles of these metal oxides as well as of CeO2 and Fe3O4 could be solubilized in non-polar solvents by functionalizing with HDTMS. Nanotubes and nanoparticles of BN could also be functionalized and solubilized with HDTMS. Organotin reagents have also been used to covalently functionalize oxide nanostructures and multi-walled carbon nanotubes, thereby producing stable dispersions in CCl4 and toluene. The organotin reagents used were dibutyldimethoxytin and trioctyltinchloride. Covalent functionalization of nanostructures using organosilane and organotin reagents provides a general method applicable to large class of inorganic materials as well as carbon nanotubes and is likely to be useful in practice

Substitution and Organohalide Oxidative Addition Reactions Involving a Dimethylplatinum(II) Complex in a Micelle Medium

Micellar system of sodium dodecyl sulfate (SDS) in a mixture of water/ethanol (1/1) is used as a new medium for stabilization of the platinum­(II) complex [PtMe₂(bipy)], in which bipy = 2,2′-bipyridine, knowing that the complex is unstable in water or ethanol in the absence of SDS. Kinetic studies for oxidative addition reactions of complex [PtMe₂(bipy)] with methyl iodide, allyl bromide, or propargyl bromide and also for substitution reactions of the chelate 2,2′-bipyridine ligand in the complex [PtMe₂(bipy)] by the P donor reagent P­(O-ⁱPr)₃, L, to form the complex <i>cis</i>-[PtMe₂L₂], were successfully investigated in the green and safe solvent micellar system of SDS by monitoring the decay of the MLCT band in the UV–visible spectra

Enhanced Catalytic Performance and Tolerance to Carbon Monoxide Poisoning of CoO/PtPd/r‐GO Nanocomposite Thin Film for Methanol Fuel Cells

This study presents the facile synthesis of CoO/PtPd and CoO/PtPd/reducedgraphene oxide (r-GO) nanocomposites, highlighting their significant role in methanol fuel cells. To create a CoO/PtPd thin film at the toluene/water interface, we employed NaBH4 to effectively reduce PtCl2(COD), PdCl2(COD), and Co (acac)3 (COD = cis,cis-1,5- cyclooctadiene, acac = acetylacetonate). The two nanocomposites were analyzed using XRD, FE-SEM, AFM, XPS, BET, and TEM techniques. In the electrooxidation of methanol in the anodic part of fuel cell, cobalt (II) oxide can serve as an oxygen source in the catalytic oxidation of carbon monoxide (CO) or it can play a role in producing the HO-CoO intermediate to facilitate the oxidation of CO-PtPd to carbon dioxide (CO2). This reaction can help eliminate CO, which is a common poison for Pt-based catalysts in methanol oxidation. Our research reveals significant improvements in current densities and catalyst tolerance when using the CoO/PtPd/r-GO nanocomposite thin film. The observed current density for CoO/PtPd/r-GO is 263.33 mA.cm&#x1;2, surpassing the reported value of 30.00 mA.cm&#x1;2 for PtPd/r- GO. The jf/jb ratios, commonly used to evaluate catalyst tolerance, are approximately 2.80 for CoO/PtPd and 4.98 for CoO/PtPd/r-GO, in contrast to ratios larger than 0.99 for ETEK Pt and 0.58 for other types of commercial Pt/C. These findings indicate that the CoO/PtPd/r-GO thin film exhibits enhanced catalytic performance and improved tolerance to CO poisoning. Furthermore, the power output calculated for CoO/PtPd/r-GO is 104.5 mW&#x3;cm&#x1;2, which is comparable to the reported value of 48.03 mW&#x3;cm&#x1;2 for commercial Pt/C. These results demonstrate the potential of the CoO/PtPd/r-GO nanocomposite thin film as a promising alternative to traditional catalyst materials in methanol fuel cells

PtAu Thin Film as Anode Electrocatalyst in Methanol Fuel Cell

Expanding the application of methanol fuel cells in the energy economy is only feasible when a low-cost or highly COtolerant electrocatalyst replaces Pt catalysts to enhance the electrocatalytic properties of Pt. In this study, a PtAu thin film was produced at the liquid-liquid interface through the simple reduction of [Pt(cod)Cl2] and [Au(PPh3)Cl] complexes. The resulting thin film was directly transferred onto a glassy carbon electrode (without the application of NafionTM) and used as an electrocatalyst in the methanol oxidation reaction. Experimental and theoretical results both confirmed that PtAu exhibits lower CO poisoning compared to PtPd or Pt films. The high jf/jb ratio (where jf is the maximum current of the anodic peak in the forward route and jb is the maximum of peak current in the backward route), and theoretically calculated adsorption energies for PtAu thin film showed higher CO tolerance compared to Pt or PtPd thin film electrocatalysts

Luminescent mononuclear and dinuclear cycloplatinated (II) complexes comprising azide and phosphine ancillary ligands

A new series of cycloplatinated (II) complexes with general formulas of [Pt (bhq)(N-3)(P)] [bhq = deprotonated 7,8-benzo[h]quinoline, P = triphenyl phosphine (PPh3) and methyldiphenyl phosphine], [Pt (bhq)(PP)]N-3 [PP = 1,1-bis (diphenylphosphino)methane (dppm) and 1,2-bis (diphenylphosphino)ethane] and [Pt-2(bhq)(2)(mu-PP)(N-3)(2)] [PP = dppm and 1,2-bis (diphenylphosphino)acetylene] is reported in this investigation. A combination of azide (N-3(-)) and phosphine (monodentate and bidentate) was used as ancillary ligands to study their influences on the chromophoric cyclometalated ligand. All complexes were characterized by nuclear magnetic resonance spectroscopy. To confirm the presence of the N-3(-) ligand directly connected to the platinum center, complex [Pt (bhq)(N-3)(PPh3)] was further characterized by single-crystal X-ray crystallography. The photophysical properties of the new products were studied by UV-Vis spectroscopy in CH2Cl2 and photoluminescence spectroscopy in solid state (298 or 77 K) and in solution (77 K). Using density functional theory calculations, it was proved that, in addition to intraligand charge-transfer (ILCT) and metal-to-ligand charge-transfer (MLCT) transitions, the L ' LCT (L ' = N-3, L = CN) electronic transition has a remarkable contribution in low energy bands of the absorption spectra (for complexes [Pt (bhq)(N-3)(P)] and [Pt-2(bhq)(2)(mu-PP)(N-3)(2)]). It is indicative of the determining role of the N-3(-) ligand in electronic transitions of these complexes, specifically in the low energy region. In this regard, the photoluminescence studies indicated that the emissions in such complexes originate from a mixed (ILCT)-I-3/(MLCT)-M-3 (intramolecular) and also from aggregations (intermolecular)

Reactivity and Mechanism in the Oxidative Addition of Allylic Halides to a Dimethylplatinum(II) Complex

The complex [PtMe₂(2,2′-bipyridine)], <b>1</b>, reacts with allyl chloride and allyl bromide, to give [PtXMe₂(CH₂CHCH₂)­(2,2′-bipyridine)], <b>2</b>, X = Cl; <b>3</b>, X = Br, with 2-methylallyl chloride to give [PtClMe₂(CH₂CMeCH₂)­(2,2′-bipyridine)], <b>4</b>, and with crotyl chloride (a mixture of <i>trans</i>- and <i>cis</i>-MeCHCHCH₂Cl), to give a mixture of [PtClMe₂(<i>trans-</i>CH₂CHCHMe)­(2,2′-bipyridine)], <b>5</b>, and [PtClMe₂(<i>cis-</i>CH₂CHCHMe)­(2,2′-bipyridine)], <b>6</b>. The complexes are formed mostly by <i>trans</i> oxidative addition and, for the crotyl complexes, without allylic rearrangement. Complex <b>1</b> reacts with CH₂CHCHMeCl, mostly with allylic rearrangement, to give complex <b>5</b>, with complexes <b>6</b> and [PtClMe₂(CHMeCHCH₂)­(2,2′-bipyridine)], <b>7</b>, as minor products. The reactions of <b>1</b> with CH₂CHCH₂X (X = Cl or Br) and MeCHCHCH₂Cl follow second-order kinetics (first-order in both reagents), but <b>1</b> reacts with CH₂CHCHMeCl by third-order kinetics (first-order in <b>1</b>, second-order in CH₂CHCHMeCl) and with CH₂CMeCH₂Cl by a mixture of second- and third-order kinetics. The second-order reactions are proposed to occur by the S_N2 mechanism, and potential mechanisms of the third-order reactions are discussed

Chelating and Bridging Roles of 2-(2-Pyridyl)benzimidazole and Bis(diphenylphosphino)acetylene in Stabilizing a Cyclic Tetranuclear Platinum(II) Complex.

The reaction of complex [Pt(Me)(DMSO)(pbz)], 1, (pbz = 2-(2-pyridyl)benzimidazolate) with [PtMe(Cl)(DMSO)2], B, followed by addition of bis(diphenylphosphino)acetylene (dppac), gave the novel tetranuclear platinum complex [Pt4Me4(μ-dppac)2(pbz)2Cl2], 2, bearing both the pbz and dppac ligands. In this structure, the pbz ligands are both chelating and bridging to stabilize the tetraplatinum framework. The tetranuclear Pt(II) complex was fully characterized by NMR spectroscopy, X-ray crystallography, and mass spectrometry, and its electronic structure was investigated and supported by DFT calculations

Reactivity and Mechanism in the Oxidative Addition of Allylic Halides to a Dimethylplatinum(II) Complex

The complex [PtMe₂(2,2′-bipyridine)], <b>1</b>, reacts with allyl chloride and allyl bromide, to give [PtXMe₂(CH₂CHCH₂)­(2,2′-bipyridine)], <b>2</b>, X = Cl; <b>3</b>, X = Br, with 2-methylallyl chloride to give [PtClMe₂(CH₂CMeCH₂)­(2,2′-bipyridine)], <b>4</b>, and with crotyl chloride (a mixture of <i>trans</i>- and <i>cis</i>-MeCHCHCH₂Cl), to give a mixture of [PtClMe₂(<i>trans-</i>CH₂CHCHMe)­(2,2′-bipyridine)], <b>5</b>, and [PtClMe₂(<i>cis-</i>CH₂CHCHMe)­(2,2′-bipyridine)], <b>6</b>. The complexes are formed mostly by <i>trans</i> oxidative addition and, for the crotyl complexes, without allylic rearrangement. Complex <b>1</b> reacts with CH₂CHCHMeCl, mostly with allylic rearrangement, to give complex <b>5</b>, with complexes <b>6</b> and [PtClMe₂(CHMeCHCH₂)­(2,2′-bipyridine)], <b>7</b>, as minor products. The reactions of <b>1</b> with CH₂CHCH₂X (X = Cl or Br) and MeCHCHCH₂Cl follow second-order kinetics (first-order in both reagents), but <b>1</b> reacts with CH₂CHCHMeCl by third-order kinetics (first-order in <b>1</b>, second-order in CH₂CHCHMeCl) and with CH₂CMeCH₂Cl by a mixture of second- and third-order kinetics. The second-order reactions are proposed to occur by the S_N2 mechanism, and potential mechanisms of the third-order reactions are discussed