Platinum complexes, reaction with silver

The original blue (K.A. Hofmann, 1908) was obtained from the reaction of Pt(MeCN)2Cl2 with silver salts over some hours. Under these conditions, the nitrite is hydrolysed to acetamide. Very recently, the structure of the complex [(H3N)2Pt(MeCONH)2Pt(NH3)2]4(NO3)10 has been determined (Figure 3.37). The average oxidation state of the platinums in the octamer is 2.25. 

Oriho-vinylbenzenethiol forms similar polymeric and hexameric complexes (55) which can be converted to monomers by reaction with two moles of triphenylphosphine per platinum. Attempts were made to remove one phosphine to give a chelate, using anhydrous silver perchlorate the product isolated had the unusual structure shown in Fig. 41. 

S-bonded alkyl and aryl sulfinato complexes can be prepared by the reaction of sulfonyl chlorides with Pt(C2H4)(PPh3)2,1633 the phase-catalyzed reaction of PtCl with NaS02R, 4 or the insertion of S02 into a platinum-alkyl bond1635 as shown in equations (481)-(483). When PtCl(S02R)L2 is treated with silver ion the 0,0 -bonded chelate complex (173) is formed (equation 484). 

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Alcohols, hydrocarbons, and their halide-containing derivatives, and their mixtures, are the most frequently used solvents (Solv). The majority of these reactions take place at room temperature or with slight heating, necessary for dissolution of the reagents. The transformation (3.199) was one of the first template reactions of the examined type [434]. In this reaction, the coordinatively unsaturated platinum complex is an N-base and silver nitrate is a Lewis acid ... 

Transition metal complexes containing catecholate and semiquinone ligands have been reviewed by Pierpont and Buchanan.336 The syntheses of catecholate adducts of platinum group metals by oxidative addition of benzoquinone (BQ) have been reported (reaction 92).337 The coordinated catechol can then be oxidized to the semiquinone with silver ion (reaction 93). In reactions (92) and (93), L M = lr(Cl)(CO)(PPh3)2] and the benzoquinones (BQ) are shown in (146). The oxidative addition of phenanthrenequinone to [Ir(Cl)(CO)(PPh3)2] has also been cited.338... 

The availability of equipment to measure molar conductivity of solutions was turned to good use. It is interesting to note that coordination chemists still make use of physical methods heavily in their quest to assign structures - it s just that the extent and sophistication of instrumentation has grown enormously in a century. What conductivity could tell the early coordination chemist was some further information about the apparently ionic species inferred to exist through the silver ion precipitation reactions. This is best illustrated for a series of platinum(IV) complexes with various amounts of chloride ion and ammonia present (Figure 3.1). From comparison of measured molar conductivity with conductivities of known compounds, the number of ions present in each of the complexes could be determined. We now understand these results in terms of modern formulation of the complexes as octahedral platinum(IV) compounds with coordinated ammonia, where coordinated chloride ions make up any shortfall in the fixed coordination number of six. This leaves in most cases some free ionic chloride ions to balance the charge on the complex cation. 

The second reaction (Eq. (3)) with silver perchlorate affords a trinuclear derivative, can be easily understood, since the silver center has two coordination positions which, in principle, could be occupied by the platinum centers of two [Pt(C6F5)3(tht)]" moieties. " This explains why the reaction takes place in a 2 1 molar ratio. However, the X-ray study of these anionic complexes reveals some interesting features. There are two anions per asymmetric unit, which present slight but significant differences. Their structures are presented in Fig. 5 and there are several points about these structures, which are worth commenting on ... 

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