Ru-hydroxyapatite

Heterogeneous catalysts such as Ru-Al-Mg-hydrotaldte, Ru-Co-Al-hydrotalcite, Ru-hydroxyapatite (RuHAP) (Eq. (7.40)) [91], RU-AI2O3 [92a,b], and Ru/A10(OH) [92c] are highly efficient catalysts for aerobic oxidation of alcohols. In these oxidation reactions, the key step is postulated as the reaction of Ru-H with O2 to form Ru-OO H, in analogy to Pd-OOH, which has been shown to operate in the palladium-catalyzed Wacker-type asymmetric oxidation reaction [93]. It is noteworthy that ruthenium on carbon is simple and efficient for the oxidation of alcohols (Eq. (7.41)) [92d]. 

Opre, Z., Grunwaldt, J., Maciejewski, M., etal. (2005). Promoted Ru-Hydroxyapatite Designed Structure for the Fast and Highly Selective Oxidation of Alcohols with Oxygen. / Catal, 230,... 

Venugopal and Scurrell544 reported low temperature shift activity for 3%Ru/ Caio(P04)6(OH)2 and 3%Au/Ca10(PO4)6(OH)2, the support being hydroxyapatite, a material that is similar to the mineral component of bones. A comparison of their activities is provided in Table 132, along with the catalyst properties. 

K. Yamaguchi, K. Mori, T. Mizugaki, K. Ebitani, K. Kaneda, Creation of a Monomeric Ru Species on the Surface of Hydroxyapatite as an Efficient Heterogeneous Catalyst for Aerobic Alcohol Oxidation, J. Am. Chem. Soc. 122 (2000) 7144-7145. 

The catalytic activity of gold for this reaction at low temperature was reported by Andreeva et al., who used Au/ Fe203 catalysts [260, 261]. Venugopal et al. also studied this system and showed that the combination Au-Ru/Fe203 or even gold supported on hydroxyapatite were more useful for the transformation [262]. 

Recently, Kaneda and coworkers developed a new strategy for the design of high-performance heterogeneous catalysts utilizing hydroxyapatite as a macroligand for catalytically active centers [8] an efficient hydroxyapatite-bound Ru catalyst (RuHAP) was developed for selective oxidation of various alcohols using 02 [9]. 

In 2000, Yamaguchi et al. [116] synthesized a ruthenium-based hydroxyapatite catalyst, with the formula (RuCl)10(PO4)6(OH)2. This catalyst could also be recycled and displayed a reasonable substrate scope in the aerobic alcohol oxidations (Eq. 30). TOFs reported in this case were generally somewhat lower, on the order of 1 h 1 for 2-octanol to 12 h 1 for benzyl alcohol. The fact that distinct Ru-Cl species are present at the surface points in the direction of a hydridometal mechanism. 

Other examples of heterogeneous ruthenium catalysts are a ruthenium-based hydroxyapatite catalyst [158], a ferrite spinel-based catalyst MnFe1.5Ruo.35 CU0.15O4 [159], and Ru supported on Ce02 [160], which all gave lower activities. 

Heterogeneous catalysts such as hydroxyapatite-bound Ru complex [67] and Ru/ AI2O3 [68] can be also used for the aerobic oxidation of primary amines to nitriles (Eqs. 3.32 and 3.33). 

Oxidations. Benzylic alcohols undergo aerial oxidation to aromatic aldehydes in the presence of many different catalysts OsOVCuCl-pyridine (for benzylic alcohols only OSO4 is needed)," Ru-on-hydroxyapatite, hydrotalcite-supported Pd(II)," and CuBr-SMe2 under fluorous biphasic conditions. ... 

Starting from the fact that hexacoordinated ruthenium salts of the general formula [Ru(bpy)2L2]X2 or [Ru(phen)2L2]X2 are capable of forming specific interactions with double stranded DNA, Strekas suggested that the two (A) and (A) enantiomers could be separated by using column chromatography with double-stranded DNA immobilized on hydroxyapatite as the stationary phase. 

The Heck and Suzuki reactions have been catalyzed by other NPs such as RuNPs, including alumina-supported RuNPs [43c]. Hydroxyapatite-supported RuNPs were recently found to be efficient and recyclable catalysts for cis-dihydroxlahon and oxidative cleavage of alkenes [43dj. Supported RuNPs in the pores of mesoporous Al-MCM-41 materials were prepared by Hj reduchon of adsorbed [Ru(NH3),s], and the activity in benzene hydrogenabon was studied in the absence and presence of 330ppm H2S in H2. By comparison, zeolite-supported catalysts were found to be more efficient when H2S was present [43dj. 

A cationic rathenium monomer spedes, prepared by ligand exchange of Cl with SbFu or OTf, on hydroxyapatite (HAP) (Scheme 6.15), acted as a heterogeneous Lewis acid toward carbonyl and cyano compounds for promoting Diels-Alder and aldol reactions [106]. The fine structure of an intermediate, cationic Ru species... 

Immobilization of ruthenium catalyst for dihydroxylation of alkenes was demonstrated by Yu and Che [63]. A colloidal ruthenium species was suspended with calcium hydroxyapatite in water in their grafting process. A 5 wt% Ru loading was thereby achieved on the resulting nano-ruthenium hydroxyapatite (nano-RuH AP). In... 

Baiker and co-workers developed a new methodology based on the hypothesis that the isolated Ru species should be close to the surface of the hydroxyapatite particles to improve the catalytic activity. In order to achieve this goal, metal promoters were added, the amount of ruthenium used was reduced and the pretreatment conditions were altered. It was claimed that by following this approach the efficient oxidation of aromatic and aliphatic alcohols was possible at 90 "C using toluene as the solvent at 1 bar of O2 pressure with turnover frequency (TOP) values in the range 15-80 h The higher activity of the promoted Ru catalysts was attributed to the steric effect of the promoter and the presence of Ru(OH)2 species. Mechanistic studies confirm that the alcohol oxidation proceeds via the formation... 

Mori K, Yamaguchi K, Mizugaki T, Ebitani K, Kaneda K (2001) Catalysis of a hydroxyapatite-bound Ru complex efficient heterogeneous oxidation of primary amines to nitriles in the presence of molecular oxygen. Chem Commun 461... 

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