Platinum complexes halides

The most important of the tertiary phosphine complexes of platinum(IV) are Pt(QR3)2X4, generally prepared by halogen oxidation [174] of cis- or trans-Pt(QR3)2X2 (Q = P, As, R = alkyl Q = Sb, R = Me), since direct reaction of the platinum(IV) halides with the ligands leads to reduction. Once made, the platinum(IV) compounds are stable to reduction ... 

In addition to the methods already outlined for platinum(II) complexes, simultaneous crystallization can be used to prepare mixed complex halides (Figure 3.105). 

Ru(bipy)3 formed in this reaction is reduced by the sacrificial electron donor sodium ethylenediaminetetra-acetic acid, EDTA. Cat is the colloidal catalyst. With platinum, the quantum yield of hydrogenation was 9.9 x 10 . The yield for C H hydrogenation was much lower. However, it could substantially be improv l by using a Pt colloid which was covered by palladium This example demonstrates that complex colloidal metal catalysts may have specific actions. Bimetalic alloys of high specific area often can prepared by radiolytic reduction of metal ions 3.44) Reactions of oxidizing radicals with colloidal metals have been investigated less thoroughly. OH radicals react with colloidal platinum to form a thin oxide layer which increases the optical absorbance in the UV and protects the colloid from further radical attack. Complexed halide atoms, such as Cl , Br, and I, also react... 

These ligands all form 1 1 complexes with platinum(II) halides which are non-conductors, monomeric and, in the solid state, contain one coordinated and two free double bonds. Proton n.m.r. data indicate that all three double bonds are equivalent in solution due to a rapid equilibrium between bonded and non-bonded —CH=CH2 groups. The phosphine and arsine complexes PtBraL (L = tvpp, tvpa) react with two equivalents of bromine giving what are believed to be platinum(II) species containing one coordinated double bond and two —CHBr-CHaBr groups arising from the saturation by bromine of the two free double bonds. 

Platinum(II) halides in ethanol cleave trimethylsilylalkynyls, without isolation of a complex 126). Possibly 7r-complex formation occurs as an intermediate step. 

Palladium complexes exhibit even higher catalytic activity and produce branched acids preferentially.132 133 The selectivity, however, can be shifted to the formation of linear acids by increasing the phosphine concentration.134 Temperature, catalyst concentration, and solvent may also affect the isomer ratio.135 Marked increase in selectivity was achieved by the addition of Group IVB metal halides to palladium136 and platinum complexes.137 Linear acids may be prepared with selectivities up to 99% in this way. The formic acid-Pd(OAc)2-l,4-bis(diphe-nylphosphino)butane system has been found to exhibit similar regioselectivities.138 Significant enhancements of catalytic activity of palladium complexes in car-bomethoxylation by use of perfluoroalkanesulfonic acid resin cocatalysts was reported.139,140... 

Chelating phosphines can be used to generate Ph2PCH2CH2CH2P(H)Ph, Cy2PCH2CH2CH2P(H)Ph P(H)Ph with platinum(II) halides in the presence complexes of type (149).1431,1432... 

Platinum(II) halides react with cyanate salts to give cyanato complexes. Reacting the compounds Pt(NCO)4 with triphenylphosphine gives Pt(NCO)2(PPh3)2.1628 These platinum(II) complexes are N-bonded. Treatment with carbon monoxide and alcohol yields the complex (172 equation 476).1629... 

Since these substitution reactions follow a two-term rate law, it is clear that solvent effects are very significant. Poorly coordinating solvents are benzene, carbon tetrachloride and sterically hindered alcohols and strongly coordinating solvents are water, lower alcohols, DMF, DMSO, acetonitrile and nitromethane. The first-order rate constants are greater in DMSO than in water. Since the majority of precursor platinum complexes used in synthetic and mechanistic studies are halo complexes, the replacement of halide ligands by solvent and the reversibility of this reaction are important features of platinum halide chemistry. 

The most common route to alkyl or aryl complexes of the type [AuRL] is by the treatment of a halide complex with an alkyl- or aryllithium reagent. The first reactions of this type were performed (15) in 1959 [Eq. (5)], and the methyl and phenyl compounds were found to have chemical and thermal stabilities intermediate between those of the previously known organopalladium and -platinum complexes. 

Alcohols, hydrocarbons, and their halide-containing derivatives, and their mixtures, are the most frequently used solvents (Solv). The majority of these reactions take place at room temperature or with slight heating, necessary for dissolution of the reagents. The transformation (3.199) was one of the first template reactions of the examined type [434]. In this reaction, the coordinatively unsaturated platinum complex is an N-base and silver nitrate is a Lewis acid ... 

Finally, copper(I), silver(I), and mercury(II) triazenides react with selected rhodium(I), iridium(l), and platinum(II) halide complexes to afford metal-metal bonded binuclear triazenide-bridged species 129). 

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