Platinum alkyl compounds

The most important of the tertiary phosphine complexes of platinum(IV) are Pt(QR3)2X4, generally prepared by halogen oxidation [174] of cis- or trans-Pt(QR3)2X2 (Q = P, As, R = alkyl Q = Sb, R = Me), since direct reaction of the platinum(IV) halides with the ligands leads to reduction. Once made, the platinum(IV) compounds are stable to reduction ... 

The use of this phosphine facilitates assignment of configuration as virtual coupling is observed when the phosphines are trans (section 2.9.5).) Syntheses follow established routes using methyllithium as an alkylating agent the platinum(iV) complexes can be made by direct alkylation of platinum(IV) compounds or by oxidative addition to platinum(II) species. 

Certain platinum-containing compounds are capable of crosslinking DNA and kill cells by similar pathways to alkylating chemotherapeutic agents. 

Substantially more work has been done on reactions of square-planar nickel, palladium, and platinum alkyl and aryl complexes with isocyanides. A communication by Otsuka et al. (108) described the initial work in this area. These workers carried out oxidative addition reactions with Ni(CNBu )4 and with [Pd(CNBu )2] (. In a reaction of the latter compound with methyl iodide the complex, Pd(CNBu )2(CH3)I, stable as a solid but unstable in solution, was obtained. This complex when dissolved in toluene proceeds through an intermediate believed to be dimeric, which then reacts with an additional ligand L (CNBu or PPh3) to give PdL(CNBu )- C(CH3)=NBu I [Eq. (7)]. 

It has been shown (p. 266) that transition metal alkyl compounds containing Cpd and C6H6 groups, ir-bonded to the metal inactivate the metal center for polymerization. It has also been shown by Nyholm and Aresta (45), in the platinum series, that five- or six-membered rings containing only sigma and ir-carbon-to-metal bonds are very stable compounds. These observations add chemical plausibility to reaction (29). 

Many transition metal alkyls react with carbon monoxide to give acyl compounds. In all these cases the acyl derivatives can be detected at least by infrared methods and in most cases isolated. Molybdenum, manganese, rhenium, iron, cobalt, rhodium, nickel, palladium, and platinum alkyls, Grignard reagents, and boranes, all react with carbon monoxide, and one can explain the products from these on the basis of carbon monoxide inserting into the metal alkyl. 

The cis/trans isomerization of platinum(II) complexes is a subject which will be discussed in some detail when the halide (Group VII) complexes are covered. Nevertheless the importance of reductive elimination reactions of platinum(II) alkyl and aryl complexes makes it imperative that this reaction be discussed here for alkyl and aryl platinum(II) compounds. 

The X-ray diffractometric studyof a product resulting from insertion of an alkyl-isocyanide into a platinum-alkyl bond has shown the compound to have the expected square-planar geometry with a Pt—C bond distance of 2.027(11) A. 

Colvin M. Alkylating agents and platinum antitumor compounds. In 91. 

Various other compounds containing metal alkyl bonds have been studied by He(I) P.E.S., and in most cases reasonable assignments of the M—C ionization have proved possible. In the case of some platinum alkyls, only a preliminary communication has appeared with no spectra or evidence for the assignments given, so these must be regarded as tentative30). 

Probably the most unorthodox cross-linking alkylating agent is an inorganic platinum-coordinating compound m-platinum (II) diamminedichloride, (c/s-DDP, cisplatin, Platinol). It is a classic square-planar four-coordinate platinum (II) compound. 

Coq, Figueras and their associates have conducted wide-ranging investigations of surface modification of supported platinum, rhodium, and especially ruthenium catalysts by treating them when hydrided with alkyl compounds of aluminium, zinc, antimony, germanium, tin or lead. The purpose of this work was to explore the locations of the modifying atoms on the surface of the active metal particles, and to see whether in any case there was evidence for the selective blocking of sites on either low co-ordination number... 

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