Formation of Platinum—Pyrimidine and a-Pyridone Blues

The formation of the blues may now be traced from monomeric to dimeric and on to tetrameric structures. This progression has not necessarily been chronological, being usually dependent on X-ray structural characterization, but it is perhaps useful to the interested chemist to describe the progression in this order. The solution chemistry is complicated and while selective and reproducible recrystallization has been achieved in most cases this does not mean that the species isolated are the only ones obtained from any particular reaction. A recent review covers many of the structures mentioned in the following discussion [29]. 

The reaction of ci [Pt(NH3)2(H20)2] with 1-MeU or 1-MeT anions in basic solution gives the bis(pyrimidine) complexes [32, 33] which with HCl yield the mono complexes [34] e.g.  

The analogous mono complexes with ethylenediamine have also been structurally characterized [35]. The corresponding bis-a-pyridone complex has been obtained from reaction with cw-[PtCl2(NH3)2] [36] in fact this is a neutral 2-hydroxypyridine (a-pyrH) species with cldoride counteranion, the minor tautomer being stabilized in the complex. The iminol form of 1-MeThymine has also been recognized upon protonation of cis-[Pt(NH3)2(l-MeT)2] [33]. The stabilization of tautomeric forms of the unsubstituted pyrimidines has also been noted [31]. 

Concurrent Pt NMR studies on the a-pyridone reaction also identified the aqua species [Pt(NH3)2(a-pyr)H20] as present in solution [37]. The mono chloro complexes all give aqua species on reaction with silver salts  

In some systems (1-MeU) the cationic aqua species may be isolated [38] 

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