Platinum compounds tetranuclear

Chemistry, p. 1429 - A tetranuclear platinum compound designed to overcome cisplatin resistance . 

Fig. 2. Schematic structures of compounds related to platinum blues . Diplatinum(II) species with HH (A-l) and HT (A-2) oriented amidate ligands, tetraplatinum(II) species (A-3), tetranuclear [Pt2 25]4 blues without (B-l) and with axial ligand (B-2), tetranuclear [Pt2 5]4 tans (C-l, C-2), and various types of diplatinum(III) species with HH (D-l, D-3) and HT (D-2) orientation of the bridging ligands. The amidate ligands are expressed with their N- and O-coordinating atoms only.

Since it is known that the tetranuclear mixed-valent platinum blue and tan complexes such as 1 and 2 undergo disproportionation and reduction by water as Eqns. 1-3 and 7-9 show [54] [66], all the species appearing in Eqns. 1-3 and 7-9 are present in the solution. However, only one or several of the four species in the solution may in fact be active during catalytic olefin oxidation. To clarify this point, the effects of the Pt oxidation state in the platinum complexes were compared. The results are summarized in Table 2. It clearly shows that the dinuclear Pt111 complex is most effective, and is likely to be a true catalyst. Compound 1 also exhibits high activity, whereas the dinuclear Pt11 complex is ineffective. All other factors expected to affect the catalytic efficiency, including the presence of 02, the surfactant and the choice of solvent, have been examined and the results are summarized... 

Platinum vapour also has been observed to react with unsaturated compounds [286]. With propene and but-l-ene, compounds of undetermined structure are produced. Reaction with 1,5-cyclooctadiene produces b/s(l,5-cyclooctadiene) platinum(O), while reaction with allyl chloride yields the tetranuclear complex [PtCl(C3Hs)] 4. 

Direct evidence for the formation of a metalla-2-oxetane in a metal mediated oxidation reaction was recently reported by Sharp and coworkers [121]. The oxidation of norbornylene by the tetranuclear platinum(II) p-oxo complex 1 yielded nearly quantitative formation of the platina-2-oxetane 2 shown in Fig. 18. The compound 2 could be isolated and the structure was identified with X-ray structure analysis. However, it is unclear if the reaction of this late transition metal complex takes place via [2-1-2] addition of a metal-oxo moiety across the C=C double bond. The authors write that the formation of the C-0 bond allows considerable speculation on this process. DFT calculations are underway to help differentiate the various possibihties [121]. 

Platinum-acetamide-blue and platinum-uracil-blue compounds have been reported. The tetranuclear uracil blue [Pt4(l-MeU)4(NH3)g](N03)5-H20, where 1-MeU is the mono-anion of 1-methyluracil, has structure and properties resembling 2-pyridone-blues. Platinum blue compounds with uridine, isonicotinamide, malonamide, and biuret have been described. ... 

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