Platinum-sulfur bonds

Platinum-ruthenium carbonyl clusters, characteristics, 8, 419 Platinum-sulfur bonds, in platinacycles, 8, 505 Platinum-thallium carbonyl clusters, characteristics,... 

AG = 58.6 kJ mor applies to a process involving 60° pivoting of the cyclic ligand with respect to the platinum-sulfur bonds, which averages CH2 and CH3 environments. At higher temperatures scrambling by ligand dissociation and recombination is possible. 

Extended Htickel calculations have been used to analyze the electronic structure of platinum complexes and also to rationalize their reactivity with various nucleophiles. Their inability to form four coordinate species of the type [Pt(S2CNR2)(ri -S2CNR2)2] has been ascribed to the lower charge on platinum (when compared with xanthate complexes), strong platinum-sulfur bonds and a repulsive interaction between the platinum 2>d electrons and the incoming ligand (1601). 

Dithiophosphato metal complexes are usually prepared by metathesis of metal halides with alkali metal or ammonium salts. A convenient method uses the redox reaction of his th iophosphory 1 )d is ulfanes (RO)2(S)PSSP(S)(OR)2, with metal species in low oxidation states resulting in the insertion of the metal into the sulfur-sulfur bond.24 Recently it was used for the synthesis of long alkyl chain, liquid platinum(II) dithiophosphates25 and for the synthesis of Ru (CO)2[S2P(OPr%]2 from Ru3(CO)i2 with (Pr 0)2(S)PSSP(S)(0Pr,)2.26... 

The first published example of the anodic cyclization with carbon-sulfur bond formation was the oxidation of thiobenzanilide to 2-phenyl-l,3-benzothiazole.120 The oxidation of the thioacetanilides (106) and /V-(3-coumaryl)thioacetamide (108) at a platinum electrode in CH3CN-Et4NC104 gave the expected 1,3-thiazole derivatives 107 and 109 in 60-75% yield169 [Eqs. (81) and (82)]. 

On the contrary, the bond could be polarized for large differences in electronic affinities. For the platinum-sulfur system, the electronic affinities are, respectively, equal to 2.12 and 2.08 eV (29). Thus the Pt—S bond is essentially a covalent one, whereas for Ir the electronic affinities are more different (2.08 eV for sulfur and 1.6 eV for Ir). In such conditions,... 

The different toxicities found for 1-butene, 1,3-butadiene, and l-butyne hydrogenation can be explained by assuming that the energetic adsorption of unsaturated hydrocarbons destabilizes the metal-sulfur bond producing a real desulfurization with l-butyne. The destabilization exists also with the butadiene, as has been shown on platinum (71). 

The antitumor activities of some sulfoxide complexes themselves, [PtCl(RR S0)(biL)]N03 (biL are diamines), have come under scrutiny, being the first active compounds of this sort with sulfur-bonded ligands. The nature (and, when appropriate, the chirality) of the sulfoxides has a marked effect on activity. The sulfoxides can be displaced by Cl or H2O, and the lability order is Ph2SO>PhMeSO>(tol)MeSO>(PhCH2)2SO> (PhCH2)MeSO>dmso. Initial loss of RR SO was precluded as the mechanism of the antitumor activity. Possibly RR SO is eliminated after the platinum has bound to DNA. 

Metals and alloys, the principal industrial metalhc catalysts, are found in periodic group TII, which are transition elements with almost-completed 3d, 4d, and 5d electronic orbits. According to theory, electrons from adsorbed molecules can fill the vacancies in the incomplete shells and thus make a chemical bond. What happens subsequently depends on the operating conditions. Platinum, palladium, and nickel form both hydrides and oxides they are effective in hydrogenation (vegetable oils) and oxidation (ammonia or sulfur dioxide). Alloys do not always have catalytic properties intermediate between those of the component metals, since the surface condition may be different from the bulk and catalysis is a function of the surface condition. Addition of some rhenium to Pt/AlgO permits the use of lower temperatures and slows the deactivation rate. The mechanism of catalysis by alloys is still controversial in many instances. 

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