Platinum complexes ethylene

The last condition, the orientation principle, is illustrated for the benzene-iodine and ethylene-platinum complexes. It is seen that the orientation depicted in Fig. 2a leads to a positive overlap integral and... 

Organoplatinum compounds easily react with unsaturated hydrocarbons such as monoolefins, diolefins and acetylenes to afford the 7r-complexes. For example, reactions are shown in eqs. (21.1)-(21.5). The compound shown in eq. (21.1) is the Zeise salt of an ethylene-platinum complex found at first as an organotransition metal compound [11-17]. 

Salts of neodecanoic acid have been used in the preparation of supported catalysts, such as silver neodecanoate for the preparation of ethylene oxide catalysts (119), and the nickel soap in the preparation of a hydrogenation catalyst (120). Metal neodecanoates, such as magnesium, lead, calcium, and zinc, are used to improve the adherence of plasticized poly(vinyl butyral) sheet to safety glass in car windshields (121). Platinum complexes using neodecanoic acid have been studied for antitumor activity (122). Neodecanoic acid and its esters are used in cosmetics as emoUients, emulsifiers, and solubilizers (77,123,124). Zinc or copper salts of neoacids are used as preservatives for wood (125). 

The shift in the C=C frequency, vi, for adsorbed ethylene relative to that in the gas phase is 23 cm-1. This is much greater than the 2 cm-1 shift that is observed on liquefaction (42) but is less than that found for complexes of silver salts (44) (about 40 cm-1) or platinum complexes (48) (105 cm-1). Often there is a correlation of the enthalpy of formation of complexes of ethylene to this frequency shift (44, 45). If we use the curve showing this correlation for heat of adsorption of ethylene on various molecular sieves (45), we find that a shift of 23 cm-1 should correspond to a heat of adsorption of 13.8 kcal. This value is in excellent agreement with the value of 14 kcal obtained for isosteric heats at low coverage. Thus, this comparison reinforces the conclusion that ethylene adsorbed on zinc oxide is best characterized as an olefin w-bonded to the surface, i.e., a surface w-complex. 

Visser and Ramakers [6] liberated 465 by the action of 2-methylthiirene 1,1-dioxide on the bis(triphenylphosphane)platinum complex 469 (Scheme 6.96) and observed a dimer, probably 474, or several dimers. The synthesis of 469 was accomplished by dehydrobromination of 468b in the presence of bis(triphenylphospha-ne)(ethylene)platinum and was believed to proceed via the trapping of 465 by the platinum complex. Jones et al. [185] doubted this opinion and regarded the reversed sequence as more likely, that is, the complexation of 468b by (PPh3)2Pt followed by the dehydrobromination. 

The platinum complex Pt(PPh3)2C2H is inserted into Si-H and Ge-H bonds with the elimination of ethylene ligands ... 

The main difference between Pt and Mn is that the platinum complex has 16 electrons and undergoes addition of silane before eliminating ethylene, following path 1... 

Significant advances in organonickel chemistry followed the discovery of frtzws,fraws,fraws-(l,5,9-cyclododecatriene)nickel, Ni(cdt), and bis(l,5-cycloocta-diene)nickel Ni(cod)2 by Wilke et. al.1 In these and related compounds, in which only olefinic ligands are bonded to the nickel, the metal is especially reactive both in the synthesis of other compounds and in catalytic behavior. Extension of this chemistry to palladium and to platinum has hitherto been inhibited by the lack of convenient synthetic routes to zero-valent complexes of these metals in which mono- or diolefins are the only ligands. Here we described the synthesis of bis(l,5-cyclooctadiene)platinum, tris(ethylene)-platinum, and bis(ethylene)(tricyclohexylphosphine)platinum. The compound Pt(cod)2 (cod = 1,5-cyclooctadiene) was first reported by Muller and Goser,2 who prepared it by the following reaction sequence ... 

Tris(ethylene)platinum(0) is stable for several hours at 20° under 1 atm of ethylene and keeps for many weeks at -20°.6 In the absence of ethylene, decomposition to metallic platinum occurs in minutes at room temperature. The complex is quite volatile, with a vile smell, and sublimes slowly at 20° in an atmosphere of ethylene onto a cold finger at 0°. 

Flynn and Hulburt, however, went further into a study of the hydrogenation of ethylene by hydrogen when a stream of these gases was passed through a solution of ethylene platinum chloride. They found that ethylene inhibits the formation of platinum metal. This inhibition seems to indicate that the first step of the reduction is a dissociation of the complex with ethylene as one of its products. The platinum formed as a result of the initial dissociation and reduction would catalyze the reduction of the complex. Ethylene, however, still inhibits the reaction markedly in the presence of platinum. 

Likewise, mononuclear complexes of rhodium and platinum containing only one meth-ylenecyclopropane ligand are prepared by ligand exchange reactions of the Feist s esters with (acac)Rh(CO)2 and rra 5-Cl2(pyr)Pt(ethylene), giving complexes (acac)(CO)Rh(tF) and trans-C 2(pyr)FiL (L = cF, tF), respectively (equation 311). 

Scheme 4 shows a platinum catalyst 1 containing such a bis-SPO bidentate ligand anion, designed for the hydroformylation of ethylene and of 1-heptene, and various other, similarly built, platinum catalysts. Catalyst 1 has an activity comparable to that of the commercial cobalt catalysts that were used at the time and displays a higher selectivity for linear products than the cobalt-containing catalysts (66). Like the latter, the platinum complex exhibits hydrogenation activity to give, in part, alcohols in addition to aldehydes and also produces alkanes (an undesired reaction that implies a loss of feedstock). The catalysts are also active for isomerization, as are the cobalt complexes, and for internal heptene hydroformylation (Table 1), with formation of 60% linear products. 

The reaction could be carried out stepwise. First, reaction of the hydride complex 1 with ethylene under pressure at 90 °C gives the ethyl platinum complex 2 then, treatment of 2 with CO at ambient temperature and pressure rapidly gives the propionyl platinum complex 3. Reaction of... 

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