Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Diruthenium hydride

These transition-metal catalysts contain electronically coupled hydridic and acidic hydrogen atoms that are transferred to a polar unsaturated species under mild conditions. The first such catalyst was Shvo s diruthenium hydride complex reported in the mid 1980s [41 14], Noyori and Ikatiya developed chiral ruthenium catalysts showing excellent enantioselectivity in the hydrogenation of ketones [45,46]. [Pg.36]

Casey and Beetner used in situ IR spectroscopy to monitor the hydrogenation of benzaldehyde catalyzed by the Shvo hydrogenation catalyst 1-tol [68]. The disappearance of benzaldehyde and the concentrations of the ruthenium species present throughout the hydrogenation reaction were observed (Fig. 2). In toluene, bridging diruthenium hydride 1-tol was the only observable ruthenium species until nearly all of the substrate was consumed. The dependence of the hydrogenation rate on substrate, H2 pressure, and total ruthenium concentration were all found to be less than first order. [Pg.111]

The reaction of the coordinatively unsaturated ruthenium amidinates with [Cp RuCl]4 tetramer or [CpRufMeCNlsJPFg provides access to novel amidinate-bridged dinuclear ruthenium complexes (Scheme 146), which in turn can be transformed into cationic complexes or hydride derivatives. In these complexes, a bridging amidinate ligand perpendicular to the metal-metal axis effectively stabilizes the highly reactive cationic diruthenium species. [Pg.282]

Arene(tricarbonyl)chromium complexes, 19 Nickel boride, 197 to trans-alkenes Chromium(II) sulfate, 84 of anhydrides to lactones Tetrachlorotris[bis(l,4-diphenyl-phosphine)butane]diruthenium, 288 of aromatic rings Palladium catalysts, 230 Raney nickel, 265 Sodium borohydride-1,3-Dicyano-benzene, 279 of aryl halides to arenes Palladium on carbon, 230 of benzyl ethers to alcohols Palladium catalysts, 230 of carboxylic acids to aldehydes Vilsmeier reagent, 341 of epoxides to alcohols Samarium(II) iodide, 270 Sodium hydride-Sodium /-amyloxide-Nickel(II) chloride, 281 Sodium hydride-Sodium /-amyloxide-Zinc chloride, 281 of esters to alcohols Sodium borohydride, 278 of imines and related compounds Arene(tricarbonyl)chromium complexes, 19... [Pg.372]

A similar rapid exchange of bridging and terminal hydride ligands and the hydrogen atoms in Ru-H-Si 3c-2e bonds is observed in the C-type diruthenium complexes Cp Ru(ju.- T2-HSiR2) 2(Ju,-H)(H) (R = Et, Ph) [see Eq. (13)].38 In these complexes, all the four hydride ligands are equivalent in the H NMR spectrum at 25°C, whereas they separate to three signals... [Pg.279]

Rhodium-based catalysis suffers from the high cost of the metal and quite often from a lack of stereoselectivity. This justifies the search for alternative catalysts. In this context, ruthenium-based catalysts look rather attractive nowadays, although still poorly documented. Recently, diruthenium(II,II) tetracarboxylates [42], polymeric and dimeric diruthenium(I,I) dicarboxylates [43], ruthenacarbor-ane clusters [44], and hydride and silyl ruthenium complexes [45 a] and Ru porphyrins [45 b] have been introduced as efficient cyclopropanation catalysts, superior to the Ru(II,III) complex Ru2(OAc)4Cl investigated earlier [7]. In terms of efficiency, electrophilicity, regio- and (partly) stereoselectivity, the most efficient ruthenium-based catalysts compare rather well with the rhodium(II) carboxylates. The ruthenium systems tested so far seem to display a slightly lower level of activity but are somewhat more discriminating in competitive reactions, which apparently could be due to the formation of less electrophilic carbenoid species. This point is probably related to the observation that some ruthenium complexes competitively catalyze both olefin cyclopropanation and olefin metathesis [46], which is at variance with what is observed with the rhodium catalysts. [Pg.805]

The diruthenium /i-hydrosulfido complex 88 reacted with a monometallic hydride complex to yield bis(/it3-sulfido) complex 89 having a terminally bonded chloro ligand (Equation (33)). The hydrido derivative 90 was obtained by the treatment of 89 with NaBH4. [Pg.814]

The diruthenium bridging hydride 1 is unreactive toward aldehydes and ketones at room temperature and above and is not the active reducing agent in the Shvo system... [Pg.95]


See other pages where Diruthenium hydride is mentioned: [Pg.678]    [Pg.678]    [Pg.291]    [Pg.292]    [Pg.65]    [Pg.240]    [Pg.203]    [Pg.187]    [Pg.291]    [Pg.292]    [Pg.561]    [Pg.648]    [Pg.650]    [Pg.659]    [Pg.673]    [Pg.682]    [Pg.684]    [Pg.693]    [Pg.694]    [Pg.699]    [Pg.705]    [Pg.1035]    [Pg.197]    [Pg.149]    [Pg.96]    [Pg.112]   
See also in sourсe #XX -- [ Pg.36 ]




SEARCH



© 2024 chempedia.info