Platinum hydrogen abstraction

Adsorption of CD on palladium showed distinct differences from that on platinum, which is already apparent from the spectra compared in Fig. 33. The ATR spectra did not show any indication of the presence of a species covalently bound by Pt C ci-bond (a-hydrogen abstraction, species 2 in the case of platinum). The strongly adsorbed 7i-bonded flat species (1 and T) were found to be more favored on platinum, whereas on palladium the tilted, nitrogen lone-pair-bound species (3 ) were dominant. Furthermore, the comparative study showed that CD is more strongly adsorbed on platinum than on palladium, indicated by the more prominent shift of the vibrational modes with respect to the free molecule on platinum than on palladium. 

Abstract The primary method for pH is based on the measurement of the potential difference of an electrochemical cell containing a platinum hydrogen electrode and a silver/silver chloride reference electrode, often called a Harned cell. Assumptions must be made to relate the operation of this cell to the thermodynamic definition of pH. National metrology institutes use the primary method to assign pH values to a limited number of primary standards (PS). The required comparability of pH can be ensured only if the buffers used for the calibration of pH meter-electrode assemblies are traceable to... 

The remainder of this review is devoted to giving a closer look at the hydrido complexes of iridium and their reactions. Iridium gives the most extensive and versatile range of hydrido complexes of any platinum metal (29). The main types of compounds known and some of their reactions are shown in Table II. To this, one must add the hydrogen abstraction reaction mentioned earlier. 

The Pt2(pop)4 complex offers a unique opportunity for studying hydrogen transfer reactivity of nucleotides and DNA. The DNA cleavage reactions are unique in that the tetraanionic platinum complex is repelled from DNA, so if hydrogen abstraction does occur, it must proceed via an unfavorable binding equilibrium ... 

We have demonstrated (a) the diversity of mechanistic pathways that exists for the thermal decompositon of metal alkoxides, and (b) how the preferred pathway is a function of the nature of the alkoxide ligand. A perhaps surprising conclusion that emerges from the study is that neither M-OR nor MO-R bond homolysis plays a direct role in these decompositions. It should be noted, however, that we have only examined the alkoxides of oxophilic metal ions that are not easily reduced. It is conceivable that for the later transition metal ions that are both less oxophilic and more reducible, decompositon pathways that lead to the reduction of the metal ion may become more important. These include -hydrogen abstraction followed by reductive elimination (cf., eq. 6), as well as M-OR bond cleavage. Note that P-hy(6ogen abstraction has been demonstrated to be quite facile for the platinum-group metal alkoxides. 

Heat a little sodium chloride in a platinum crucible to bright redness, and add a couple of drops of water to the hot crucible so that the water assumes the spheroidal state. In a moment, transfer the water to a beaker containing a faintly coloured soln. of blue litmus —the litmus is reddened, showing the presence of an acid—hydrochloric acid. The salt remaining in the crucible is dissolved in water, and it turns red litmus blue, showing the presence of an alkali—sodium hydroxide. There appears to be a reaction NaCl+H20 NaOH +HC1, and the water abstracts the more volatile hydrogen chloride. 

Over the alumina-supported metals, the activity sequences for isomerisation and hydroisomerisation were observed to be similar. With these catalysts, the results were interpreted in terms of a H-atom addition-abstraction mechanism involving an adsorbed but-2-yl intermediate the importance of the alumina support as a source of hydrogen atoms to initiate the isomerisation was stressed [130,133]. It was suggested that, with platinum black, isomerisation occurred by both an addition—abstraction and an abstraction—addition mechanism, the relative contributions of each depending upon the experimental conditions [135]. 

D KIEs proved439 that in the oxidation of formaldehyde on a polycrystalline platinum electrode modified with Pb atoms and on pure platinum electrode, the cleavage of both OH and CH bonds and the abstraction of the hydrogen atom from an OH bond in hydrated formaldehyde are rate-determining on the Pt/Pb and on the Pt electrode, respectively. The ku/ku for the oxidation of formaldehyde at copper electrode (at pH 13, at 25 °C) depends on the electrode potential and reaches the highest value of 7 at low potentials and drops to about 2.5 at higher positive potentials440. 

Abstract. The statistical theory of processes of phase transformations realized by hydrogenation of metalfiilleride has been developed in present paper. Such reaction was studied experimentally for fullerides of palladium and platinum [1,2],... 

Abstract. The detailed study of carbon nanomaterials constitution with allowance for of reduction conversions Pt (II, IV) allows to realize directional looking up of methods of preparation of platinum catalysts for redox reactions in hydrogen fuel cells. 

---