Platinum mononuclear compounds

B. Mononuclear Compounds of Iron, Molybdenum, Tungsten, Rhenium, Platinum,... 

Arene and olefin compounds, pure or in admixture, are efficient ligands in promoting the aggregation of platinum atoms from mononuclear species to ligand-stabilized soluble clusters and solid-supported nanoparticles (Scheme 14). 

Chiral bis-(binaphthophosphole) (bis(BNP)) ligands have been used in the asymmetric hydroformylation of styrene. In solution, the free diphospholes display fluxional behavior. Consistent with their structure, the reaction of the bis(BNP) compounds with platinum(II) derivatives gives either cis chelate mononuclear complexes or trans phosphorus-bridged polynuclear derivatives. Coordination to platinum enhances the conformational stability of bis(BNP)s and diastereomeric complexes can be detected in solution. In the presence of SnCl2, the platinum complexes give rise to catalysts that exhibit remarkable activity in the hydroformylation of styrene. Under optimum conditions, reaction takes place with high branched selectivity (80-85%) and moderate enantio-selectivity (up to 45% ee). 

The polynuclear platinum compounds stand in vivid contrast to mononuclear platinum complexes because the predominant DNA lesions are long-range inter- and intrastrand cross-links where the sites of platination may be separated by up to four base pairs. The consequent structural and conformational changes in DNA are also distinct. 

Organom etallic Compounds. Organometallic complexes of platinum are usually more stable than palladium complexes. Carbon monoxide complexes of platinum are formed more readily than with palladium. Mononuclear and polynuclear complexes in oxidation states 0 to +2 exist such as... 

Bis(alkyl) complexes, with mercury, preparation, 2, 428 Bis(alkylidene)s, in Ru and Os half-sandwiches, 6, 583 Bis(alkylimido) complexes, with chromium(VI), 5, 346 Bis(rj2-alkyne)platinum(0) complexes, preparation, 8, 640 Bis(alkynyl) complexes in [5+2+l + l]-cycloadditions, 10, 643 with manganese, 5, 819 with mercury, preparation, 2, 426 mononuclear Ru and Os compounds, 6, 409 with platinum, 12, 125 with platinum(II), 8, 539 with titanium(IV), 4, 643 with zirconium, 4, 722... 

Spontaneously adsorbed monolayers of the dimeric complex (Figure 5.11) [(pOp) Os(bpy)2 (4-tet) Os(bpy)2 Cl]3+, where pOp is 4,4 -bipyridyl, bpy is 2,2/-bipyridyl and 4-tet is 3,6-bis(4-pyridyl)-l,2,4,5-tetrazine, have been assembled on platinum microelectrodes in an attempt to address these issues [33]. Significantly, as illustrated in Figure 5.11, the voltammetric response associated with the Osn/m reaction is unusually ideal for both metal centers. Studies using mononuclear model compounds reveal that the redox responses centered at approximately 0.620 and 0.300 V correspond to the inner [(pOp) Os(bpy)2 (4-tet)]2+ and outer [(4-tet) Os(bpy)2 Cl]+ moieties, respectively. The observation of two well-defined voltammetric waves indicates that electron transfer can occur across the [(pOp) Os(bpy)2 (4-tet)]2+ bridge to the outer [Os(bpy)2 Cl]+ moiety, i.e. charge trapping does not occur. 

Both pyridine (pyr) and quinoline (quin) compounds are efficient cross-linking agents but not potent cytotoxic agents. Interstrand cross-linking is thus not by itself a sufficient requirement for cytotoxicity. These results were also of considerable interest because the mononuclear precursors were found to be similar in cytotoxicity to cisplatin itself, violating the classical structure-activity relationship of platinum compounds. Yet incorporation into the dinuclear structure did not produce active compounds ... 

The polymeric bis[arcnetellurolato]platinum compounds were depolymerized by tri-phenylphosphane to mononuclear complexes1. 

Disilyl chalcogen compounds react in a similar manner (eqnation 39), to give both mononuclear complexes and bridged complexes (if excess platinum hydride precursor is used). ... 

Preparation of carbon-bonded CH2COO complexes gives the impression that the platinum ion favors carbon-bonded structures as is known in the case of various mononuclear platinum complexes (26-29), and the tetraacetate complexes do not exist as stable compounds. The tetra(acetato)diplatinum complex, [Pt2(CH3C00)4(H20)2] (Fig. 8), was eventually prepared, however, by refluxing a solution of K2[Pt (NOalJ in CH3COOH-I M HCIO4 (2 1) (30, 31). 

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