Platinum-blues structure

Stein and co-workers have reported the structure of an unusual tetranuclear platinum(II) complex possessing both ammine and carbonato ligands.325 During a study of the reaction of cisplatin with Ag+, followed by the addition of 2 -deoxyuridine to afford platinum blue -like products from aqueous solution (pH < 2), a colorless minor product was isolated from the reaction mixture. X-ray crystallography confirmed that the product was a cyclo tetra-cation... 

Structures and Reactivities of Platinum-Blues and the Related Amidate-Bridged Platinum111 Compounds Kazuko Matsumoto and Ken Sakai... 

STRUCTURES AND REACTIVITIES OF PLATINUM-BLUES AND THE RELATED AMIDATE-BRIDGED PLATINUM111 COMPOUNDS... 

II. Syntheses and Structures of Platinum-Blues and Related Amidate-Bridge Platinum111 Compounds... 

The first direct evidence for the structure of platinum-blues was provided by the single-crystal X-ray studies of cis-diammineplatinum a-pyridonate-blue, [Pt(2.25+)4(NH3)8(/x-a-pyridonato-N,0)4] (N03)5 H20 (48, 49). In the study, Barton and Lippard selected a-pyridone as a simplified model of pyrimidine bases (see Fig. 3), which must be the primary reason of their success in obtaining the first crystalline-blue material. 

Followed by the X-ray studies on cc-pyridonate-blue, various platinum-blues and the related complexes of exocyclic amidate and imidate ligands (see Fig. 3) have been prepared and structurally ana-... 

Pt(2.5 + ), and Pt(3.0+). These oxidation states correspond to their formal oxidation states of Pt(II)2, Pt(II)3Pt(III), Pt(II)2Pt(III)2 and Pt(III)2, respectively. To date the Pt(2.75+) state corresponding to Pt(II)Pt(III)3 has never been found. In addition to this classification, the structures can also be grouped according to the orientation of the two bridging amidate ligands within a dimeric unit head-to-head (HH) and head-to-tail (HT) are known to Pt(II)2 and Pt(III)2 compounds (52, 53, 94, 95) (see A-l, A-2, D-l, and D-3 in Fig. 5). However, only the HH isomers afford a dimer of dimers, leading to the tetrapla-tinum chain structure of platinum-blues. On the other hand, the HT... 

In general, such derivatives are constituted by tetraplatinum complexes having as the main ligand a wide range of bio-compatible molecules. The first, structurally characterized platinum blue complex was the oc-pyridonate [Pt4(NH3)8(C5H4N0)4](N03)5, Figure l.15... 

Several blue tetra- and octanuclear Pt complexes, prepared upon reaction of cis-[Pt(NH3)2(H20)2]2+ with open and cyclic amides, as well as cyclic imides and a uracil nu-cleobase, and comprised of binuclear building blocks interacting through Pt-Pt bond formation, have been isolated and structurally characterized in recent years. Without exception, the average Pt oxidation state in these compounds is 2.25. Nevertheless, the structure and mode of action as antitumor agents of the Platinum Pyrimidine Blues , as prepared by Rosenberg in the early 70 s, remain elusive. This account represents a summary of our present knowledge on cationic Platinum Blues , with a focus on those blues obtained from cis-[Pt(NH3)2(H20)2]2+ and pyrimidine nucleobases, and presents speculations on reasonable alternative structures. 

Matsumoto etal. [103] [104] used a-pyrrolidone as bridging ligand and obtained a tan colored compound having analogous structure to the platinum blue of Lippard, except that the average oxidation state was +2.50... 

Syntheses and Structures of Cisplatin-Derived Platinum Blues and the Related Diplatinum(III) Complexes... 

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.

Fig. 6 A mixed copper-platinum tetracyanide, structurally analogous to PtS, with sulphur replaced by a bridging copper tetracyano complex.19 Pink spheres denote platinum, gray carbon, and blue nitrogen, with PtC4 square planes in pink and CiiNg tetrahedra in blue. Reproduced with permission. Copyright 1990, Royal Society of Chemistry.

Pt complexes have been reviewed. These are often mixed Pt VPt complexes many have a chain structure with M M interactions or even M M bonds. Others have Pt -Hal-Pt -Hal-Pt chains. An example of the latter has Pt L4Cl2 " units alternating with Pt L2Cl2 units. Many analogs are now known. The related platinum blues are oligomeric mixed valence compounds with Pt- Pt interactions and formed from [PtCl2(NH3)2] and pyrimidines, of which examples have now been crystallized. ... 

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