Ruthenium complexes Subject

In 2009, Buchmeiser and co-workers reported the synthesis of a novel ruthenium complex 54 based on a seven-membered NHC ligand [68] (Fig. 3.22). To examine the catalytic activity of complex 54 in the RCM reaction, the authors subjected the complex to a series of typical RCM reactions by using substrates 1, 3, and 5. Pre-catalyst 54 showed only moderate reactivity with 1 and 3 and no reaction occurred with 5. 

For these reasons, and the relative ease with which the complexes are prepared, an increasing number of studies have been performed on the photophysical and photochemical properties of such complexes. Though most of the studies in this area have been performed on dinuclear ruthenium complexes, an increasing number of Ru/Os and Os/Os dimers have been studied in recent years (228, 541-552) and this subject has been reviewed (222). 

Similarities between [Ru(bpy),]2+ (discussed in Chapter 13) and [Pt,(pop)J4 are apparent. Reactive excited states are produced in each when it is subjected to visible light. The excited state ruthenium cation, [Ru(bpy)3]" +, can catalytically convert water to hydrogen and oxygen. The excited slate platinum anion, [Pt,(pop)J 4-, can catalytically convert secondary alcohols to hydrogen and ketones. An important difference, however, is that the ruthenium excited stale species results from (he transfer of an electron from the metal to a bpy ligand, while in the platinum excited state species the two unpaired electrons are metal centered. As a consequence, platinum reactions can occur by inner sphere mechanisms (an axial coordination site is available), a mode of reaction rot readily available to the 18-clectron ruthenium complex.-03... 

Dinuclear ruthenium complexes form the largest group by far of any mixed-valence system and are the exclusive subject of this chapter. Ruthenium is the transition metal of choice to study electron transfer or exchange because it is relatively inexpensive and forms stable Ru(III) and Ru(II) coordination complexes. In addition, the synthetic coordination chemistry of ruthenium is well developed (1). 

Metal enolates have played a Umited role in the metal-catalyzed isomerization of al-kenes . As illustrated in a comprehensive review by Bouwman and coworkers, ruthenium complex Ru(acac)3 (51) has been used to isomerize a wide range of substituted double bonds, including aUylic alcohols (131), to the corresponding ketones (132) (equation 38) . The isomerization of aUylic alcohols affords products that have useful applications in natural product synthesis and in bulk chemical processes. An elegant review by Fogg and dos Santos shows how these complexes can be used in tandem catalysis, where an alkene is subjected to an initial isomerization followed by a hydroformylation reaction ... 

In comparison with classic Lewis acids derived from main group halides (e.g., B, Al, Sn), f-elements, and early transition metal halides, late transition metal Lewis acids often are more inert to ubiquitous impurities such as water, offer higher stability, tunable properties by ligand modification, and a well-defined structure and coordination chemistry, thus allowing detailed studies of reaction mechanisms, and a rational basis for catalyst optimization. Among this new class of late transition metal Lewis acids, ruthenium complexes - the subject of this chapter - display remarkable properties... 

Cadmium Sulfide-Ruthenium Complex System. It has previously been noted by Kalyanasundaram et al. that pure CdS is subject to photocorrosion [104]. Holes generated in the valence band migrate to the surface and... 

Rhodium and ruthenium complexes of 2,2 -bis(diphenylphosphino)-l,l -binaphthyl (BINAP) have frequently been used as catalysts for enantioselective hydrogenation of olefins and ketones." "" From consideration of the literature on this subject, it was proposed that the presence of a mono-oxidized BINAP in an organometallic catalyst could have interesting consequences." Accordingly, Rh(BINAP)(CO)Cl was prepared, and upon reaction with O2, (BINAP(0))Rh(CO)Cl was formed. These compounds were authenticated by X-ray crystallography, and IR and NMR spectroscopies. The kinetics of this reaction were monitored by solution (chloroform was the solvent) IR spectroscopy. In the absence of added CO, the oxygenated compound was formed in about 50% yield. BINAP(0)2 and CO2 are also produced. Plots of obs (from loss of reactant) versus [O2] at various temperatures yielded... 

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