Dinuclear ruthenium catalysts

More recently, Llobet and coworkers reported the anodic electropolymerization of A -substituted pyrroles as a convenient method of anchoring a redox-active dinuclear ruthenium catalyst onto conducting solid supports, like vitreous carbon sponges (VCS) and fluorine-doped tin oxide (FTO). In the presence of Ce(IV) as the sacrificial oxidant, turnover numbers up to 76 have been achieved. A major improvement of the system is accomplished by the copolymerization with a robust non active redox species, able to further separate the catalytically active species on the solid support, obtaining up to 250 catalytic cycles. 

In 2006, Hulshof and colleagues reported the synthesis of a novel dinuclear ruthenium catalyst, bearing tetrafluorosuccinate and racemic BINAP ligands. This catalyst was applied to the DKR of various secondary alcohols in the presence of isopropyl butyrate as the acyl donor and Novozym 435 as the... 

The Blue Dimer and Other Dinuclear Ruthenium Catalysts... 

THE BLUE DIMER AND OTHER DINUCLEAR RUTHENIUM CATALYSTS... 

In 2006, Hulshof et ah reported the synthesis of a novel dinuclear ruthenium catalyst, bearing tetrafluorosuccinate and racemic BINAP ligands. This catalyst was applied to the DKR of various secondary alcohols in the presence of isopropyl butyrate as the acyl donor and Novozym 435 as the enzyme (Scheme 8.23). The activation of the ruthenium catalyst with K2CO3 was necessary. When the reaction was performed in the presence of the ketone corresponding to the substrate, it was complete within 10 hours with an excellent enantioselectivity, whereas, without this ketone, the complete reaction was achieved in 23 hours, also giving an excellent enantioselectivity. 

As a general preparation procedure of the water oxidation catalyst of dinuclear ruthenium complex, [(bpy)2(H20)Ru0Ru(H20)(bpy)2], the corresponding mononuclear ruthenium complex ds-[Ru(bpy)2(H20)2] has been used as a precursor complex . However, other reports claimed that the mononuclear ruthenium complex itself can mediate water oxidation under... 

Finally, the structural characteristics of the 1,8-naphthyridines favour their behavior as bidentate and dinucleating ligands, thus leading to short metal-metal separations in late transition-metal complexes,24"26 and to the stabilization of mixed-valence complexes.27,28 The dinuclear ruthenium complex [ Ru(napy)(H20)2 (/i-Cl)(/i-0H)](C104)2 is a stable and active catalyst for the oxidation of alcohols and the epoxidation of alkenes, while its mononuclear precursor is much less active.29... 

In 1986, a peculiar hydrogen transfer catalyst was reported by Shvo and co-workers (272). Shvo s catalyst is a dinuclear ruthenium complex (I) that dissociates in solution into compounds II and III (Fig. 68), which interconvert in the presence of a hydrogen acceptor D or a donor DH2. Both hydrogens, the metallic hydride and that of the hydroxocyclopentadienyl substituent, can be transferred... 

Dinuclear ruthenium(ii) complexes 199, which have been used as catalysts in a large number of hydrogen-transfer reactions, are known to dissociate in solution into the mononuclear hydride complexes 200 and the coordinatively unsaturated dienone derivatives 201 (Scheme 15). Remarkably, hydrides 200 are selectively formed when THF solutions of 199 are heated under hydrogen atmosphere. This process involves the conversion of 201 into 200 via heterolytic addition of The related amino-cyclopentadienyl complexes 202 and 203 are also known, being... 

Another method for reductive dimerization has been developed in hy-drosilylation. NiCl2-SEt2 is an effective catalyst in silylative dimerization of aromatic aldehydes with a hydrosilane (Scheme 12) [40]. A catalytic thiolate-bridged diruthenium complex [Cp RuCl(/ 2-SPrI)2RuCp ][OTf] also induces the conversion to 1,2-diaryl-1,2-disiloxyethane [41]. A dinuclear (siloxyben-zyl)ruthenium complex is considered to be formed, and the homolytic Ru - C bond fission leads to the siloxybenzyl radicals, which couple to the coupling product 14. 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

Besides mononuclear, dinuclear complexes were also applied successfully as Kharasch addition catalysts (Fig. 38) [200, 201]. Ruthenium amidinate complex... 

Recently, Severin reported the Kharasch addition of several mixed rhodium(I)-ruthenium(II) and rhodium(III)-ruthenium(II) catalysts (see Part 3, Sect. 8.5). It was also demonstrated that 0.5 mol% of dinuclear rhodium(I) complex 434 having a bridging THDP ligand is an active catalyst for the Kharasch addition of BrCCl3 to simple olefins 433 in water [228]. The yields of adducts 435 ranged from 81 to 92%. 

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