Pt IV

The activity of Pt(IV) species is considered to result from reduction to the Pt(II) complex. Biological reductants such as ascorbic acid and cysteine readily effect this reduction [9] the reduction has been observed in tissue culture [17]. In accordance with these observations, cis-[PtCl2(/-PrNH2)2] has been identified as one of the metabolites of the corresponding Pt(rV) complex [18]. Similarly, there is a report surveying Pt(IV) complexes that concludes that only those with active reduction products had activity [19]. 

Model studies with nucleobases such as 5 -GMP showed that Pt(II) products are formed [27] but results from oxidation of Pt(II)-cytosine complexes are indicating novel modes of reaction and binding for the oxidized species [28] (see also Chapter 4). 

The caution which must be exercised in the purity of materials, especially where side products also have biological activity, is underlined by the observation of a surprisingly rapid isomerization between the isomers of [PtCl2(OH)2(NH3)2] [29]. The structures of three isomers have been resolved, complex 30 being obtained from 28 in solution [29, 30]  

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PtCl2, and platiaum tetrachloride [37773-49-2]. Platiaum dichloride exists in an a- and P-form, the latter containing a Pt core and edge-bridging chlorides. Platinum trichloride [25909-39-1], PtCl, contains Pt(II) and Pt(IV) centers. Other haHdes include two bromides, PtBr2 [13455-12-4] and PtBr ... 

Plating and Coatings. Thin surface coatings of platinum and platinum alloys are used as decorative finishes and in critical appHcations where it is necessary to provide finishes resistant to corrosion or high temperature, eg, coatings on jet-engine turbine components (258). Compounds used in the electro deposition of platinum are based on Pt(Il) and Pt(IV) and include H2[PtCl3] and its salts, eg, Pt—P—Salt, [Pt(NH3)2(N02)2] H2[Pt(S04)(N02)2] ... 

N. M. Bikales and L. Segal, eds.. Cellulose and Cellulose Derivatives, High Polymers, Vol. V, Wiley-Interscience, New York, 1971, Pts. IV—V. 

The capacity of studied organopolymeric sorbents depends on metal nature (Pd (II) > Au (III) > Pt (IV)) as well as on the composition and stmcture of sorbent matrix (polyvinylpyridine macroporous > polystyrene macroporous > polystyrene fibrous). 

The liquid membrane (thickness 0.2 cm) was separated from the aqueous solutions by two vertical cellophane films.The electrode compartments were filled with 0.05 M sulfuric acid solutions and were separated by the solid anion-exchange membranes MA-40. Binary mixtures contained, as a mle, 0.04 M Cu(II) and 0.018 M Pt(IV) in 0.01 M HCl. 0.1 M HCl was used usually as the strip solution. 

Suppose that the metal is replaced by Pt(IV) write the formula of the complex ion. 

The complexation of 6-nitro-2,3(lfif,47/)-quinoxalinedithione with Co(II) and Ni(II) froms the basis of a procedure for the simultaneous estimation of both metals with serious interference from only Cu(II), Pd(II), Pt(IV), or Os(VIII). ... 

Bis complexes of pyrrole-A -carbodithiolate (L) with Pt(II), Pd(II), and Co(II), as well as Cu(II), have been reported. A mixed chlorine-ligand complex of Pt(IV), [PtCl2L2], was also prepared. Infrared spectra of these complexes indicated an exocyclic single C-N bond, as opposed to similar complexes containing other dithiocarbamate ligands (407). 

Reaction between (Ph3P)4Pt and Mc2BBr follows a different path since a 1 2 stoichiometry is observed. The 6-coordinate Pt(IV) derivative (Ph3P)2Pt(BMc2)2Br is formed. ... 

The change in the group trans to the silyl ligand is thought to account for the reversal of substitution pattern in the case of the monodentate phosphine 63). Six-coordinate Pt(IV) intermediates have been postulated for these Pt(II) reactions (27, 71). Such an intermediate has recently been isolated [Eq. (62)] (27). 

This yellow crystalline Pt(IV) complex decomposes slowly at 20° C with evolution of hydrogen and formation of tra r-Hl2SiPtI(PEt3)2. The proposed mechanism is shown in Eq. (63). 

Basolo et al., have found similar platinum(II)-catalysed chloride exchange reactions with other Pt(IV) complexes, including cis- and ran5-Pt(NH3)4Cl, Pt(NH3)5CP and rra J-Pt(NH3)3Cl3. These reactions proceed by the chloride bridge mechanism above and the apparent rate coefficients k P.mole . sec, 25 °C) for platinum exchange, which was concluded to occur via this pathway. 

Beattie and Basolo have investigated the reactions of the substitution-inert octahedral complexes of Pt(IV) with tris(bipyridine)chromium(II). A rapidmixing, stopped-flow apparatus was made use of in the majority of experiments. 

Kinetic data were obtained by following the disappearance of Cr(bipy)3 562 m/i, usually with Pt(IV) in excess. The stoichiometry corresponds to... 

Although Pb(IV) is sufficiently strong an oxidant to oxidise halides, no kinetic data are available. Complexes of Pt(IV) and Au(III) oxidise iodide and thiocyanate ions but the other oxidants are weaker and form stable halo-complexes. However, some simple molecules such as hypophosphorous acid, carbon monoxide and molecular hydrogen are oxidised by the weaker members. 

The work with iodide (preceding sub-section) was extended to thiosulphate , and isosbestic points and second-order kinetics were again obtained with the various Pt(IV) complexes (Table 8). Two 8203 ions are consumed per mole of Pt(IV) reduced, suggesting tetrathionate to be the product of oxidation, viz. 

Redox behaviour of this type is considered to influence many substitution reactions of Pt(IV) . ... 

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