Platinum complexes chlorination

These isomers differ in chemical behaviour, for if two molecules of pyridine are caused to act upon Compound L, dichloro-diammino-platinum, the chlorine is replaced in the complex by two molecules of pyridine, and the substance dipyridino-diammino-plato-chloride is formed ... 

Although homogeneously catalyzed reactions of platinum complexes are mostly concerned with hydrogenation, hydroformylation, isomerization and hydrosilylation reactions, the complexes trans-PtHX(PPh3)2 (X = C1, Br, I) have been used used as catalysts for the oxidative chlorination of n-pentane. H2PtCl6 and K2PtCl are used as oxidants.201... 

As mechanistic hypothesis it was proposed (9-11) that the excited platinum complex undergoes homolytic Pt Cl cleavage affording a Ptm intermediate and an adsorbed chlorine atom (Scheme 1), by analogy with the known photochemistry of hexachloroplatinate in homogeneous solution (23,31). Electron injection from the platinum(III) complex into the titania conduction band reforms PtIv. Thus, the... 

K [PtClJ Here the platinum complex is [PtClJ-, so assigning a normal oxidation state of - 1 to chlorine gives, for a - 2 charge on the complex ... 

Alkanes and arenes can also be activated to other reactions by platinum complexes in aqueous solution (57,58). For arenes in the presence of H2PtCl5, reduction from Pt(IV) to Pt(II) occurs and the arene undergoes chlorination. The reaction is catalyzed by platinum(II) (59). Similarly, if a platinum(IV) catalyst such as HjPtClg is used, chloroalkanes are formed from alkanes. As an example, chloromethane is formed from methane (Eq. 23) (60-62). Linear alkanes preferentially substitute at the methyl... 

In this new class of platinum complexes some examples do not present the necessary cis configuration with respect to the chlorines. Oxaliplatin has been approved for clinical use in France and China for colorectal cancer. The interest in developing platinum complexes that bind to DNA in a fundamentally different manner to cisplatin is an attempt to overcome the resistance pathways that have evolved to eliminate the drug. 

The cytotoxicity of cisplatin originates from the hydrolysis facility of the chlorine, its binding to DNA, and the formation of covalent cross-links. One disadvantage of cisplatin is its limited solubility in aqueous solutions and its intravenous administration. Platinum complexes with distinctively different DNA binding modes from those of cisplatin may provide higher antitumor activity against cis-platin-resistant cancer cells. 

Subsequent x-ray diffraction analysis proved the square planar configuration (Fig. 5-1) to be correct. Furthermore, it was revealed that the three chloride atoms are in the same plane as the platinum, while the ethylene molecule is perpendicular to the plane, as shown. A slight distortion of the basic square planar structure is noted since the platinum to chlorine bond length trans to ethylene is longer than those that are cis. A similar example of a square planar metal 7r-complex is seen in 7r-allylpalladium chloride [(tt-C3H5)PdCl]2(Fig.5-2). 

Platinum(IV) complexes of phosphine and arsine ligands formed by oxidation with chlorine or bromine are well known. Chloro complexes such as ci5-[PtCl2(PEt3)4]2+ can be generated by electrolysis of the platinum(II) complex c -[PtCl2(PEt3)2].433 Similar platinum(IV) complexes... 

The first reported porphyrin complexes of platinum(IV) date from 1980 and were obtained by hydrogen peroxide oxidation of platinum(II) porphyrin complexes in an acidic medium (HC1).479 Since then oxidation of platinum(II) complexes of other porphyrins has been achieved by the same method,480 and by chlorine,481 or bromine482 oxidation. Reaction with iodine did not lead to oxidation and treatment of platinum(IV) porphyrin complexes with iodide resulted in reduction to platinum(II). 

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