Platinum derivatives

An insoluble compound formulated as [Pt(CO)2]n has been obtained by Booth and Chatt both by hydrolysis of Pt(CO)2Cl2 in benzene and by carbonylation of Na2PtCl4 in ethanol (19, 20). 

More recently, reductive carbonylation of Na2PtCl6 6H20 in methanol, in the presence of alkali acetates or hydroxide, has been shown to proceed 

The so-called platinum carbonyl readily reacts further with alkali, dissolving to give a series of dianions with general formula [Pt3(CO)6]n2- (n = 6, 5, 4, 3, 2). Each of these dianions can be obtained in a pure state by careful control of the initial OH /Pt(IV) ratio (n = 3, OH-/Pt = 8-9 n = 4, OH-/Pt = 6-6.1 n = 5, OH /Pt = 5.7). However, these ratios are quite critical and the reaction must be followed by IR. If the incorrect product is formed, the desired final product can be obtained by adding further small amounts of alkali or of sodium hexachloroplatinate. 

Under these experimental conditions, it has proved quite difficult to stop the reduction at [Pti8(CO) 0]- . This species has been more conveniently prepared, in the absence of alkali, by oxidation of preformed [Pt16(CO)3o]2- with sodium hexachloroplatinate according to the reaction  

The orange-red dianion [TtefCO) ]2-, which has also been obtained by reductive carbonylation in concentrated methanolic sodium hydroxide solution, is better synthesized by reducing preformed [Pt3(CO)6]n2- (n = 3, 4, or 5) with sodium or lithium metal in THF. Using Na/K alloy, the reduction goes still further to give the unstable pink dianion QPtsfCO) 6]2-(vco = 1950, 1745 cm-1), as yet not isolated in the solid state. 

---

Newer silicone adhesives having solids levels up to 97% are also commercially available [109]. Instead of using silanol condensation reactions, they rely on addition chemistry between vinyl functional silicone oligomers and silicon hydride terminated silicones. This addition reaction is typically facilitated with platinum derived catalysts. This hydrosilation process can be run at reduced oven temperatures, but the finished products typically do not yield the same balance of properties as seen for condensation cure materials. 

The cyclometallated palladium and platinum derivatives of trimesityl phosphine or arsine react with pyrazole or 3,5-dimethylpyrazole to form metal chelates 243 (E = P, As M = Pd, Pt R = H, Me) having the trans configuration (81TMC24). 

Other subgroups of alkylating agents are the nitrosoureas (examples carmustine, BCNU lomustine, CCNXJ) and the triazenes (example dacarbazine, DTIC). Platinum derivatives (cisplatin, carboplatin, oxaliplatin) have an action that is analogous to that of alkylating agents (formation of crosslinks) and therefore are appended to this class, as well. 

We note in passing that DNA-refilicase has an essential thiol group which is labelled by mercurials. To our knowledge no studies of the effect of platinum on the replicase have been made and this is clearly an omission which should be rectified. In some proteins platinum derivatives would seem to go for the same sites as mercury(II) reagents — a not surprising result as their chemistry is similar. 

As understanding of the mechanisms of platinum resistance has increased, more rationally designed platinum derivatives have been synthesized. One approach has been to insert steric... 

Pt(TV) Prodrugs. Platinum(IV) complexes have been widely studied as potential prodrugs that avoid the limitations of the cisplatin class of anticancer drugs. Indeed, the Pt(IV) compound satraplatin [Pt(cha)Cl2(OAc)2(NH3)] (cha, cyclohexylamine) is currently in clinical trials for treatment of hormone-refractory prostate cancer (Fig. 1) (22). Satraplatin is the first orally bioavailable platinum derivative under active clinical investigation and is particularly attractive because of the convenience of administration, milder toxicity profile, and lack of cross-resistance with cisplatin. These results are promising and support the idea that platinum(IV) complexes offer the opportunity to overcome some of the problems associated with cisplatin and its analogs. 

Platinum derivatives of zinc mew-ethynylporphyrins have been made by conventional reactions one product was the 1,3-diynydiyl-linked bis-porphyrin fran5-(Ph3P)2ClPt C=C Zn(porph) CsCCsC Zn(porph) CsC PtCl(PPh3)2-trans, which was identified by MALDI mass spectrometry through the ion [HC=C Zn(porph) C4 Zn(porph) CsCH - - Na]+ at miz 1197. ... 

Of the wide array of platinum derivatives, carboplatin is the only compound except cisplatin that is used in medical practice, and it differs from cisplatin in the replacement of two chlorine atoms with a cyclobutan-l,l-dicarboxylic acid fragment. Like cisplatin, carboplatin also reacts with DNA to form both internal and external cross-bonds. The range and indications of use are practically analogous to cisplatin. Synonyms of this drug are paraplatin and others. 

All three elements form complex ammino-derivatives. Those of osmium have been very little investigated those of iridium are analogous to the anunino-derivatives of platinum on the one hand and to the ammincs of cobalt and chromium on the other whilst the platinum derivatives resemble those of cobalt, save that the metal in the platinic derivatives is tetravalent and not trivalent as in the cobalt-ammines. 

Fagan, P. J., Calabrese, J. C. Malone, B. 1991a The chemical nature of C60 and the characterization of a platinum derivative. Science, Wash. 252, 1160-1161. 

The reactions of various platinum derivatives with Ru3(CO)12, Eqs. (15)—(18), were explored by Stone and co-workers (28, 30). As seen by comparison of Eqs. (14)—(18), the exact product that resulted was very dependent on the particular platinum complex employed. All of the reactions involved phosphine transfer from platinum to ruthenium during... 

Bis-platinum Derivatives. Based on the recognition that cisplatin cytotoxicity is predicated upon the formation of bifunctional interastrand and... 

---