Platinum complex compounds with pyridine

Aresta (54) has investigated the platinum complexes formed with o-allylphenol and o-allylthiophenol. The phenolic ligand reacts with the PtCl4 ion (in a suitable acetate buffer) to form the chelate complex shown in Fig. 40. The coordinated double bonds of this compound are successively replaced by two equivalents of pyridine. 

Tetrammino-platinous salts are known containing pyridine in place of ammonia. Thus, diammino-dipyridino-platinous salts have been prepared. These salts are interesting, as they exist in isomeric forms, and through them the configuration of the isomeric diacido-diammino-platinous compounds have been determined. It is well known that diacido-diammino-platinum exists in stereo-isomeric forms. These isomers react with two molecules of pyridine in such a manner that pyridine replaces acidic radicles in the complex with formation of diammino-dipyTidino-platinous salts. Depending upon which isomer is treated with pyridine, two different diammino-dipyridino-platinous salts are produced. Cis- or unsymmetrical dichloro-diammino-platinum is... 

Dichloro(l, 3-propanediyl)platinum and its bis(pyridine) derivative have been studied by a number of authors. Dichloro(l,3-propanediyl)platinum, and the corresponding substituted 1,3-propanediyl platinum compounds release the parent cyclopropane on treatment with potassium cyanide, potassium iodide, a tertiary phosphine, carbon monoxide, and other ligands.2,6 Reduction by means of hydrogen or lithium aluminum hydride yields chiefly isomeric substituted propanes. Dichlorobis(pyridine)(l,3-propanediyl)platinum in refluxing benzene yields a pyridinium ylid complex, - (CH3CH2CHNC5Hs)-PtpyCla. 

The compound is a dark red-purple dichroic cystalline material. In time, the crystals develop a thin coating of sulfur. The rhodium(III) complex, which appears to be structurally similar to the platinum(IV) compound, shows much greater reactivity in that sulfur is readily lost on dissolving in water, dimethyl-formamide, or pyridine. From water, a product may be precipitated which appears to contain the [RhSi0] anion. Reaction with cyanide ultimately produces the thiocyanato complex. 

On the other hand, the palladium and platinum complexes of pyridine-2-aldoxime, when treated with acetyl chloride in hot chloroform, gave stable chelates containing the acylated ligand. A monoacetylated palladium chelate was isolated in which 1 mole of pyridine-2-aldoxime was replaced by two chloride ions (see reaction XXIV). This compound was identified by its infrared spectrum, which had a strong carbonyl absorption band near 1790 cm-1. The platinum complex of pyridine-2-aldoxime gave a... 

Bis(trifluoromethyl)platinum complexes may conveniently be prepared by the reaction of dimethyl(cyclo-octa-l,5-diene)platinum with trifluoro-iodomethane in methylene chloride, followed by displacement of the cydo-octadiene with the required ligand L (L = AsMcs, PMeaPh, pyridine, RNC, etc.) Oxidative addition of iodine thence gives the platinum(iv) compounds ... 

These compounds are convenient starting materials for the preparation of a wide variety of platinum(II) complexes. The chlorine atoms can be replaced by other negative groups such as bromide, iodide, hydroxide, nitrate, nitrite, and thiocyanate. The ammonia molecules can be replaced by other bases such as pyridine, arylamines, and quinoline. Oxidation with aqua regia or chlorine yields the corresponding isomers of tetrachlorodiammineplatinum(IV) (synthesis 62). A supposedly third (7-) form has been shown to be a solid solution or mixture of the cis (jS-) and trans (a-) isomers. 

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