Substitution reactions of platinum

Ring opening reactions are the main feature of a brief review (though with 69 references) of kinetics and mechanisms of hydrolysis and substitution reactions of platinum(II) complexes (219). 

Toblt III Sterlc Factors In Substitution Reactions of Platinum (II) Comploxos in Ithyl Alcohol. 

Among the less common oxidation states those of I and III have the most significance. Complexes of platinum(III) have been of interest for many years because of their intermediacy in substitution reactions of platinum(II) and (IV). More recently binuclear platinum(I) and (III) complexes have been isolated, and the chemistry of these new complexes will be of increasing interest in platinum chemistry. Platinum forms strong homometallic bonds giving rise to multimetallic chain compounds and cluster complexes. The increasing use of X-ray crystallography, and 31P and 19 PtNMR will allow systematic studies to be made on these multimetallic platinum complexes. 

Table 13 Books and Reviews Covering Substitution Reactions of Platinum Complexes...

Any detailed description of the mechanism of an octahedral substitution must also account for the stereochemical changes that accompany reaction. Werner recognized this and made use of it in his discussions of the stereochemistry of reactions of cobalt(III) complexes. The available experimental results can be explained on the basis of possible molecular rearrangements and some cautious predictions can even be made. The base hydrolysis of cobalt III)ammines appears to be unique in that it often occurs with rearrangement it also affords the few known examples of optical inversion. These results can be explained by formation of a 5-coordinated species with a trigonal bipyramidal structure. Optically active metal complexes racemize by either an intramolecular or an in-termolecular process. Substitution reactions of platinum metal complexes often occur with retention of configuration. 

Substitution reactions of platinum(II) complexes containing one or more metal carbon bond(s) have a long history.217 Interest in such complexes and their reactivity is associated with their function as catalysts in synthetic procedures and in environmental applications. One important characteristic is the kinetic trans effect this is ascribed to the labilisation of a ra/is-positioned group caused by a C-bonded ligand,218 typically alkyl or aryl. In a mechanistic study in which kinetics measurements at elevated pressures were employed, cyclometallated Pt(II) complexes were used.219 The complex shown in Scheme 4 is water-soluble permitting the kinetics of substitution by a wide range of nucleophiles to be studied in aqueous solution. 

We were very fortunate at this point in time because Harry Gray had collected a great deal of rate data on substitution reactions of platinum(ii) complexes. This was my first exposure to the more noble of the transition metals. I soon had a great deal more because I was fortunate enough to be a collaborator with Joe Chatt on the kinetics of substitution reactions of a series of organometallic compounds of nickel(ii), palladium(ii) and platinum(ii). ... 

Kinetics and Mechanisms of Ligand Substitution Reactions of Platinum(II) Complexes... 

It was clear in the 1950s that there was a need for detailed kinetic studies of ligand substitution reactions of platinum(ii) complexes, and our laboratory was prepared to do this because it was engaged in such studies of octahedral substitution. However, only a brief account of our studies is given in this article. At about this time Martin and his students initiated their investigations of aquation reactions of chloroammineplatinum(ii) complexes. 

The IV state, d6. Although Pdlv compounds exist they are generally less stable than those of Pt,v. The coordination number is invariably 6. The substitution reactions of platinum(iv) complexes are greatly accelerated by presence of Pt11 species.4 Solutions also readily undergo photochemical reactions in light. 

A further example is provided by platinum(IV) complexes. Such complexes are generally prepared by the oxidation of the corresponding platinum(ll) complexes, e.g. [Pt(NH3)J + Clj -> trans-[Pt(NHj)4Cl2]. The observation that platinum(II) catalyses the substitution reactions of platinum(lV) led to the synthesis by Johnson of the previously imknown /rans-[Pt(en)2(SCN)2] by the reaction of tra y-[Pt(en)2Cy with NCS in the presence of a catalytic amount of [Pt(en)J. ... 

Formation.—Amongst substitution reactions of platinum(u) complexes the reaction of /ra j-[Pt(PEt8)2(R)Cl] (R = o-tolyl) with pyridine in methanol solution is anomalous. In dealing with this reaction in Volume 3 we reported on the nature of the anomaly and its explanation in terms of the mechanism... 

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