Mononuclear Complexes Scope

Finally, the dendrimer or star may be surface or internally functionalized or decorated with metal-containing motifs. This type of dendrimer is widely investigated with a view to preparing novel catalytic systems in which a dendritic effect results in enhanced or modified catalytic properties with respect to a similar number of mononuclear complexes. As many of these species are strictly organometaUic they do not fall properly within the scope of this volume. 

An exhaustive treatment of the electrochemical behaviour of transition metal complexes is beyond the scope of this book, because the enormous number of ligands available, combined with the possibility to prepare mono- and/or polynuclear complexes using identical or mixed ligands, would render such a task almost impossible. Therefore, the discussion is limited to some aspects associated with the redox properties of (essentially) mononuclear metal complexes. In particular, we will concentrate representatively on the redox changes of first row transition metal complexes (excluding the metallocene complexes, as they have been already discussed in Chapter 4) that give stable, or relatively stable products. A systematic and useful examination of the redox activity of organometallic complexes of transition metals dated to 1984 has appeared.1... 

The chemistry of indium complexes of aU types in metal oxidation states lower than +3 has been comprehensively reviewed. Few lower oxidation state mononuclear amido complexes of indium are well characterized, however, and no structure has been reported for an In(I) amide. The compound In N(SiMe3)2 n. which is unstable, " has been characterized NMR spectroscopy but its structure is unknown. The structures of several In(I) complexes, related to amides but outside our current scope, have been described. Like its aluminium and gallium counterparts, the p-diketuninate derivative [ In N(Dipp)C(Me) 2CH] has been characterized, as has the closely related species [ In N(Dipp)C(CF3) 2CH]. ° These feature V-shaped, two-coordination at the metal. The less bulky [(In N(Mes)C(Me) 2-CH)2] ° and 15-2.6-.Vlc,)( (Me) i are dimeric with long In In bonds of... 

Although ruthenium is significantly less expensive than rhodium and although its use has been recommended since 1960 (7) for the oxo synthesis, complexes of this metal have not been developed as catalysts. However, many papers and patents have referred to the results obtained employing various ruthenium complexes. The purpose of this article is to analyze the work done involving ruthenium compounds, restricting the scope only to the hydroformylation reaction and not to the carbonylation reaction, which would demand to too lengthy an article. In this review we examine successively mononuclear ruthenium complexes, ruthenium clusters as precursors, photochemical activation, and supported catalysis. 

By contrast with the use of biological material such as hydrogenase or PS I, the synthetic approach benefits from the creativity of chemists that exploit the versatile and modular character of coordination chemistry to develop efficient molecular photosensitizers and catalysts. The last few years have seen tremendous achievements in the area of hght-driven hydrogen production [55,81,82], with the emergence of efficient catalysts based on Earth-abimdant elements, that is, diiron mimics of the active site of the [FeFe]-hydrogenases (Chapter 8), mononuclear nickel- and cobalt-based complexes. The latter series has been extensively reviewed recently and is thus out of the scope of this chapter [83-85]. 

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