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|3.2 Bisphenanthroline: A Suitable Molecular Bridge?| 3.2.1 Preparation of phenphen and Related Complexes The synthesis of 5,5’-bi-1,10-phenanthroline (phenphen) was performed according to a procedure described by Thummel et al. using a Ni-mediated homocoupling reaction. Scale up of this reaction and application of the previously prepared phenBr as substrate instead of the otherwise used 5-chloro-1,10-phenanthroline resulted in the formation of phenphen in moderate yields (see figure 59). [131, 133] N 2 N Br 1. Ni(PPh 3 ) 4 /Zn 2. KCN (DMF) N N N N Figure 59: Synthesis of phenphen from phenBr. The scheme in figure 60 gives an overview of the applied synthesis steps toward the heterobinuclear photocatalyst and important reference compounds. In a first attempt it was possible to prepare the homobinuclear phenphen-bridged ruthenium complex [(tbbpy) 2 Ru(µ-phenphen)Ru(tbbpy) 2 ] 4+ (Ru(phenphen)Ru) in quantitative yield via reaction of phenphen and [Ru(tbbpy) 2 Cl 2 ] in 1:2-stoichiometry through the protocol for the preparation of ruthenium complexes from the Rau group (method C1). [120] This complex is very similar to the complex of Campagna et al. which contains bpy-ligands instead of tbbpy-ligands but in contrary, was not prepared via [Ni(PPh 3 ) 4 ]-mediated cross-coupling of [(bpy) 2 Ru(5-chloro-1,10-phenanthroline)] 2+ as described there. [131] The same microwave reaction was applied to the 1:1 mixture of phenphen and [Ru(tbbpy) 2 Cl 2 ] for the mononuclear ruthenium complex Ru(phenphen) ([(tbbpy) 2 Ru(phenphen)] 2+ ). But counter ion exchange with NH 4 PF 6 and work up yielded a mixture of the desired mononuclear complex Ru(phenphen) and the binuclear ruthenium byproduct Ru(phenphen)Ru, as first indicated by TLC-experiments and later supported by 1 H-NMR-experiments. Using a solvent mixture of KNO 3 /water/ACN (very polar), it was possible to separate the two products by column chromatography over silica and to obtain the mononuclear complex in 65% yield. Platinum was chosen as active metal at the reaction center due to its increased stability under reductive conditions in a NN-coordination sphere and, furthermore, because platinum |85|
|3.2 Bisphenanthroline: A Suitable Molecular Bridge?| N N phenphen N N i N N N N Ru 2 + N N N N N N N N Ru 2+ 4[PF 6 ] - i Ru(phenphen)Ru N N N N Ru 2+ N N N N 2[PF 6 ] - ii N N N N Ru 2+ N N N Cl Pt N Cl 2[PF 6 ] - Ru(phenphen) Ru(phenphen)Pt Figure 60: Synthesis of the homo- and binuclear ruthenium and platinum complexes Ru(phenphen), Ru(phenphen)Ru and Ru(phenphen)Pt from phenphen. i) [Ru(tbbpy) 2 Cl 2 ], (EtOH/H 2 O), 2 h, microwave, reflux. ii) K 2 PtCl 4 (DMF), 28 h, reflux, 36%. compounds display about the same high catalytic activity as their related palladium compounds. [82, 134, 135] In this way the system would be protected from decomposition by colloid formation after the photoreduction with retention of the catalytic activity of the palladium catalyst. For this synthesis, Ru(phenphen) was treated with K 2 PtCl 4 for 28 hours in a two-phase system of dichloromethane/water and later DMF to obtain the hetero-binuclear ruthenium-platinum complex [(tbbpy) 2 Ru(µ-phenphen)PtCl 2 ] 2+ (Ru(phenphen)Pt) in 36% yield according to the reaction pathway in figure 60. |86|
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Development of Novel Catalysts for
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Diese Arbeit entstand auf Anregung
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Den Arbeisgruppen von Prof. Dr. U.
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Contents 1 Introduction 1 1.1 Fossi
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|Contents| 6 Experimental Section 1
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|1 Introduction| 1 Introduction The
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|1.1 Fossil Fuels and Nuclear Power
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|1.2 Renewable Fuels| of natural ga
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|1.3 Energy Transformation and Stor
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|1.4 Solar Energy Conversion| A fra
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|1.5 Photosynthesis| Figure 9: Mole
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|1.6 Photocatalyzed Reactions| 2 NA
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|1.6 Photocatalyzed Reactions| (1)
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|1.7 Mimicking Photosynthesis| So t
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|1.8 Formalisms of Photocatalytic S
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|1.9 Multicomponent Systems from Fu
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|3.3 NN-NHC-Ligand bbip: Toward Sec
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|3.4 Outlook, Exploratory Investiga
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|4 Summary| 4 Summary Against the b
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|4 Summary| The resulting complexes
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|4 Summary| 10 [TEA] + TEA visible
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|4 Summary| absorption between 430
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|4 Summary| additional NN- and NHC-
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|5 Zusammenfassung| Die Herstellung
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|5 Zusammenfassung| phenphen und Ru
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|5 Zusammenfassung| Fragment tragen
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|5 Zusammenfassung| [TEA] + TEA vis
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|5 Zusammenfassung| In einer abschl
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|6 Experimental Section| Spectroele
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|6 Experimental Section| 1.3648 was
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|6.1 Synthesis of the Organic Ligan
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|6.2 Synthesis of the Metal Complex
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|7 Appendix| 7 Appendix dd ddd DEI
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|7 Appendix| Ru(tpphz)Os [Ru(bpy) 2
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|References| [26] M. Chanon, M. Sch
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|References| [81] S. Tschierlei, M.
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|References| [138] L. Pazderski, J.
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|References| [194] C. Liu, J. Li, B
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Selbstständigkeitserklärung: Ich
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