Ruthenium catalysts coordination complexes

Olefin metathesis catalysts based on ruthenium have been shown to exhibit a quite good tolerance to a variety of functional groups. The ring opening metathesis polymerization of strained, cyclic olefins initiated by group VIII salts and coordination complexes in aque-... 

Because of the creative minds contributing to the field, the tools of C-H bond transformation available to synthetic chemists are actively expanding [1], Among these, coordination-directed C-H bond-activation has long preserved its appeal, because it enables selective functionalization of a particular C-H bond in the presence of other functional groups. This can be achieved by using a heteroatom (FG = functional group shown in Scheme 1) in the substrate structure to direct the metal complex to the proximity of the specific C-H bond. Even unactivated sp3-centered C-H bonds tend to react in a cyclometalation step with palladium, platinum [2], and ruthenium catalysts [3]. 

A variety of NHC-ruthenium catalysts exhibiting different coordination spheres were synthesized, for example Schiff base (see complex 28) [77], arene (see complex 29) [78], and metallic moieties (see complexes 30) [7,79, 80] (Fig. 5) and show activity in RCM and ROMP. 

We have demonstrated the ACP reaction catalyzed by Ru Pybox complexes. The catalytic activity of ruthenium complexes is commonly not strong. Nevertheless, ruthenium catalysts activated by newly designed ligands have recently received much attention not only for ACP but also for the nonasymmetric version in terms of coordination chemistry and also industrial curiosity because of high stereoselectivity. We believe that further improvement of the ruthenium catalysts will be in environmental interest to realize industrially applicable process. 

All effective catalysts for the asymmetric reduction of prochiral C=N groups are based on complexes of rhodium, iridium, ruthenium, and titanium. Whereas in early investigations (before 1984) emphasis was on Rh and Ru catalysts, most recent efforts were devoted to Ir and Ti catalysts. In contrast to the noble metal catalysts which are classical coordination complexes, Buchwald s a sa-titanocene catalyst for the enantioselective hydrogenation of ketimines represents a new type of hydrogenation catalyst [6]. In this chapter important results and characteristics of effective enantioselective catalysts and are summarized. 

Two palladium coordination complexes of 68 have been reported and used in asymmetric aldol and Mannich-type reactions. " Both the catalysts are recyclable although longer reaction times are needed on subsequent uses. Diamine ruthenium complexes bound to 68 have also been made and used in the asymmetric hydrogenation of ketones. ... 

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