Platinum , ammine complexes

Platinum ammine complexes have been a fertile area for studying transinfluence. Table 3.21 lists data for a range of ammines showing how /(195Pt-15N) depends upon the trans-atom [153]. (A further selection of data can be found in R.V. Parish, NMR, NQR, EPR and Mossbauer Spectroscopy in Inorganic Chemistry, Ellis-Horwood, Chichester, 1991, pp. 76, 87.) Possibly the most detailed study (of complexes of tribenzylphosphine) examined over a hundred neutral and cationic complexes [154] (Table 3.22). 

In recent years a large number of polyclonal and monoclonal antisera have been produced against adducts or modified DNA samples of a variety of chemical classes, including methylating and ethylating agents, aromatic amines, polycyclic aromatic hydrocarbons (PAH), aflatoxins, psoralens and platinum-ammine complexes (1.2). These antisera have been used to establish highly-sensitive quantitative immunoassays and have been adapted for immunohistochemistry, and electron microscopy. 

The results cited above indicated the platinum—pyrimidine blues to be oligomeric, mixed-valent cations with metal—metal bonding, in line with opinions on the original platinblau , first described in 1908 from the reaction of platinum salts in the presence of amides [10]. The bridging, and thus chain extension, occurs through the pyrimidines and the remarkable propensity of platinum—ammine complexes to stack in species such as [Pt(NH3)2Br2Pt(NH3)2Br4] [11] undoubtedly contributes to the chain extension and indeed, the platinum—pyrimidine blues are another example of this tendency. 

Dispersed Metals. Bifimctional zeoHte catalysts, principally zeoHte Y, are used in commercial processes such as hydrocracking. These are acidic zeoHtes containing dispersed metals such as platinum or palladium. The metals are introduced by cation exchange of the ammine complexes, foUowed by a reductive decomposition (21) ... 

Another platinum(IV) ammine complex studied as a possible anti-tumour compound is shown in Figure 3.101 [171] m-(l,2-diaminocyclohexane)tetra-chloroplatinum has undergone clinical trials but was found to be too neurotoxic. 

Stein and co-workers have reported the structure of an unusual tetranuclear platinum(II) complex possessing both ammine and carbonato ligands.325 During a study of the reaction of cisplatin with Ag+, followed by the addition of 2 -deoxyuridine to afford platinum blue -like products from aqueous solution (pH < 2), a colorless minor product was isolated from the reaction mixture. X-ray crystallography confirmed that the product was a cyclo tetra-cation... 

In the early development of analogs of the platinum compounds, complexes with windows of reactivity similar to the platinum complexes were examined extensively. Whereas direct Ni and Pd analogs of Pt complexes are too kinetically reactive to be of use as drugs, Ir and Os ammine... 

In addition to chelate complexes, the cyclic amine 1,4,7-triazacyclononane will complex to platinum(II) and (IV). The hexacoordinate platinum(IV) complexes are bonded to two molecules of the tridentate ligand, but platinum(II) complexes with the ligand monodentate and bidentate.988 Also the formation of platinum(II) ammine complexes from chloride complexes is a reversible process. The rate constants decrease as the basicity of the leaving amine increases.989... 

The reaction of PtX and liquid ammonia gives mixtures of haloammine complexes [PtX (NH3)6 ]X4 n (X = Cl, Br, I n = 3, 2, 1, 0). The salts Pt(NH3)6]X, may be isolated as the main product only after several weeks of reaction. Interactions at room temperature of PtCl -and PtBr salts with liquid ammonia yield the dinuclear p-amido ammine complex [(NH3)4Pt(/i-NH2)2Pt(NH3)4]X6 quantitatively.1033 The structure shows a Pt-Pt separation of 3.16(1) A. 34 Interaction of PtXg with liquid or gaseous ammonia followed by addition of excess KNH2 yields the hexakis(amido) complex K2[Pt(NH2)6] (equation 333).1033 Complexes of the anionic ligand NC12 bonded to platinum(IV) have also been prepared. One method is by treatment of [PtCl(NH3)s]CI3 with chlorine (equation 334).1035... 

The next major theory of metal ammines was proposed by Carl Ernst Claus (1796—1864). In 1854, Claus rejected the ammonium theory and suggested a return to Berzelius view of complexes as conjugated compounds. He compared the platinum ammines not with ammonium salts nor with ammonium hydroxide but with metal oxides. He designated the coordinated ammonia molecule as passive, in contrast to the active, alkaline state in the ammonium salts, where it can easily be detected and replaced by other bases . 

Deposits from solutions of ammine complexes are often good. Two specific examples have been mentioned, namely platinum (Section 57.2.5.4(ii)) and zinc (Section 57.2.5.6). However, such processes have found no large-scale applications. 

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