Platinum cations

Many of the recent efforts in this area of chemistry have been designed to explore the chemistry of the trifluoromethyl species prepared by these reactions. Among the more interesting results have been the construction of carbene and tetramethylcyclobutadiene ligands affixed to trifluoromethyl platinum cations (78), the synthesis of difluoro-carbene complexes like (Cp)Mo(CO)3CF2+ (79), the formation of (CF3)2CS from CF3Re(CO)5 (38), and the insertion reaction of S02 into CF3-metal bonds (80). 

Fig. 31 Locant numbering of initial atom in each of the modules of a self-assembled platinum cation...

The -allenyl/propargyl platinum cations generally exhibit electrophilicity at the central carbon. The unsubstituted rj -allenyl/propargyl species is particularly reactive and is subject to addition to a wide variety of nncleophiles (see Nucleophile). The reactions of the -allenyl/propargyl species with alcohol,... 

Taylor et al.8 were the first to report an electrochemical method for preparation of MEAs for PEMFCs. In their technique, Pt was electrochemically reduced and deposited at the electrode membrane interface, where it was actually utilized as an electrocatalyst. Nation, which is an ion exchange polymer membrane, is first coated on a noncatalyzed carbon support. The Nafion-coated carbon support is then immersed into a commercial acidic Pt plating solution for electrodeposition. Application of a cathodic potential results in diffusion of platinum cations through the active Nation layer. The migrated platinum species are reduced and form Pt particle at the electrode/membrane interface only on the sites which are both electronically and ionically conductive. The deposition of Pt particles merely at the electrode/membrane interface maximizes the Pt utilization. The Pt particles of 2-3.5 nm and a Pt loading of less than 0.05 mg cm-2 were obtained employing this technique.8 The limitation of this method is the difficulty of the diffusion of platinum... 

Fig. 1.83. Observed reaction cycles for the oxidation of carbon monoxide by nitrous oxide catalyzed by gas-phase atomic platinum cations [408]...

The oxidation of methane with molecular oxygen is catalyzed by the atomic platinum cation [11b]. A key step in the catalytic cycle is the reaction of PtCHi with molecular oxygen to mainly (70%) regenerate PF via liberation of neutral species [C,Hi,Oil which either represents vibrationally excited formic acid and/or its decomposition products (CO-f-HiO) and (CO2+H2). Final oxygenates are methanol, formaldehyde as well as higher oxidation products (Scheme V.4). Experimentally determined reaction energies for the elemental steps are summarized in Table V.2 [11b]. The coupling of carbon dioxide and aromatic C-H bonds mediated by ion SiFs" has also been observed [11c]. 

The reaction of electrophilic platinum cations developed to study the oxidative addition of alkanes to platinum center with diethyl ether has been shown to generate carbene complex 163 in high yield the product is thought to arise from the C-H activation of diethyl ether followed by an a-H elimination reaction (Equation (30)). 

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