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A Bis(acetyl)-Bridged Platinum(II) Coordination Polymer as a Building Block for Diacetylplatinum(II) Complexes and Platina-β-diketones

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journal contribution
posted on 27.04.2009, 00:00 by Sebastian Schwieger, Frank W. Heinemann, Christoph Wagner, Ralph Kluge, Cornelia Damm, Gunter Israel, Dirk Steinborn
The bis(acetyl)-bridged complex [{Pt(COMe)2}n] (2) has been prepared from the platina-β-diketone [Pt2{(COMe)2H}2(μ-Cl)2] (1) with hexamethyldisilazane. Reactions of complex 2 with the monodentate P and N donors PPh3, pyrazole (Hpz), pyridine (py), 4-methylpyridine (4-Mepy), and benzylamine (BnNH2) resulted in the formation of the cis-diacetylplatinum(II) complexes cis-[Pt(COMe)2L2] (L = PPh3, 3; Hpz, 5; py, 6a; 4-Mepy, 6b; BnNH2, 7). Reactions with the bidentate N donors 2,2′-bipyridine (bpy), dimethylglyoxime (H2dmg), and pyridazine (pydz) resulted in formation of the complexes cis-[Pt(COMe)2(L∩L)] (L∩L = bpy, 4; H2dmg, 8) and [Pt2(COMe)4(μ-pydz)2] (9), respectively. Furthermore, complex 2 has been found to react with acids such as HX (X = Cl, Br), generated in situ from Me3SiX/H2O, acetylacetone (Hacac), and hexafluoroacetylacetone (Hhfacac) to yield the known platina-β-diketone 1, the new dinuclear bromo-bridged platina-β-diketone [Pt2{(COMe)2H}2(μ-Br)2] (10), and new mononuclear platina-β-diketones [Pt{(COMe)2H}(L∩L)] (L∩L = acac, 11; hfacac, 12). All complexes were characterized by means of microanalysis and IR and NMR spectroscopy. X-ray diffraction analyses were performed for complexes 1012, showing a two-dimensional network built up by closed-shell Pt···Pt (d8−d8) interactions and bifurcated hydrogen bonds in crystals of complex 10 as well as infinite platinum chains built up by closed-shell Pt···Pt (d8−d8) interactions in crystals of complexes 11 and 12. Complexes 8, 11, and 12 have further been analyzed by UV/vis and luminescence spectroscopy in solution and in the solid state as well as time-resolved photo-emf measurements. Additionally, quantum chemical studies on the DFT level of theory revealed very strong O−H···O hydrogen bonds in the platina-β-diketones 1012 (25.6−27.9 kcal/mol).