Big Chemical Encyclopedia

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

Articles Figures Tables About

DIPHOS ethane

Diphos (dppe) l,2-bis-Diphenylphosphino)ethane Diphos-4 (dppb) l,4-Wj-Dipheiiylphosphino)butane... [Pg.2100]

Rhodium and ruthenium complexes have also been studied as effective catalysts. Rh(diphos)2Cl [diphos = l,2-bis(diphenyl-phosphino)ethane] catalyzed the electroreduction of C02 in acetonitrile solution.146 Formate was produced at current efficiencies of ca. 20-40% in dry acetonitrile at ca. -1.5 V (versus Ag wire). It was suggested that acetonitrile itself was the source of the hydrogen atom and that formation of the hydride HRh(diphos)2 as an active intermediate was involved. Rh(bpy)3Cl3, which had been used as a catalyst for the two-electron reduction of NAD+ (nicotinamide adenine dinucleotide) to NADH by Wienkamp and Steckhan,147 has also acted as a catalyst for C02 reduction in aqueous solutions (0.1 M TEAP) at -1.1 V versus SCE using Hg, Pb, In, graphite, and n-Ti02 electrodes.148 Formate was the main... [Pg.378]

The catalytic activity of cationic rhodium precursors of formula [Rh(diene)(di-phosphine)]+ was also explored by Schrock and Osborn [28]. Halpern and coworkers made very detailed mechanistic studies of olefin hydrogenation by [RhS2(diphos)]+ species (diphos = l,2-bis(diphenylphosphino)ethane S = solvent) [31]. Significant differences have been observed in the reaction of the catalyst precursors [Rh(NBD)(PPh3)2]+ and [Rh(NBD)(diphos)]+ in methanol, as shown in Eqs. (8) and (9) ... [Pg.17]

Although the latter product is a solvated mononuclear [Rh(MeOH)2(diphos)]+ cation, in the solid state it is isolated as a binuclear complex of formula [Rh2 (diphos)2](BF4)2, in which each rhodium center is bonded to two phosphorus atoms of a chelating bis(diphenylphosphino)ethane ligand, and to a phenyl ring of the bis(diphenylphosphino)ethane ligand of the other rhodium atom. This dimer reverts to a mononuclear species on redissolving. The mechanism of hydrogenation of the prochiral alkene methyl(Z)-a-acetamidocinnamate, studied in detail by Halpern [31], is depicted in Scheme 1.7. [Pg.17]

Complexes of other metals are also capable of catalyzing useful carbonylation reactions under phase transfer conditions. For example, certain palladium(o) catalysts, like Co2(C0)g, can catalyze the carbonylation of benzylic halides to carboxylic acids. When applied to vinylic dibromides, unsaturated diacids or diynes were obtained, using Pd(diphos)2[diphos l,2-bis(diphenylphosphino)ethane] as the metal catalyst, benzyltriethylammonium chloride as the phase transfer agent, and t-amyl alcohol or benzene as the organic phase(18),... [Pg.12]

DIPHOS (DPPE) 1,2-bis(diphenylphosphino)ethane, (C6H5)2PCH2CH2P(C< ,H5) ... [Pg.202]

By contrast, diphos (l,2-bis(diphenylphosphino)ethane) was found to react146 with the Ni and Pd complexes in solution to form planar complexes of type (80), while the Pt complex formed an isolable adduct of unknown structure, which could be thermally or photochemically converted into the planar product. [Pg.620]

Stereoselective allylic alkylations have been carried out with the aid of palladium catalysts. The 17-(Z)-ethylidene groups of steroids (obtained from the ketones by Wittig olefination) form n-allyl palladium complexes in the presence of copper(n) salts (B.M. Trost, 1974, 1976). Their alkylation with dimethyl malonate anions in the presence of 1,2-ethane-diylbis[diphenylphosphine] (— diphos) gives a reaction exclusively at the side chain and only the (20S) products. If one starts with the endocyclic 16,17 double bond and replaces an (S)-20-acetoxy group by using tetrakis(triphenylphospbine)palladium,the substitution occurs with complete retention of configuration, resulting from two complete inversions (B.M. Trost, 1976). [Pg.27]

The fragmentation patterns of a number of phosphine-metal carbonyl complexes have been reported 164). Complexes of bis(diphenylphos-phino)ethane (diphos) appear to lose ethylene to give ions of the type (Ph2P)2Mo+. In contrast to thermal decomposition by loss of phosphine,... [Pg.295]

Chelatingbidentate ligands such as l,2-bis(diphenylphosphino)ethane-(diphos)152,191 cis-l,2-bis(diphenylphosphino)ethylene152 and 2,2 -bipyridyl(bipy)197) replace two moles of CO. In the reaction of the ditertiary phosphines (L) and Fe(CO)2cp(Sime3) there was some evidence for production of bridged derivatives of the type [(R3Si)cp(CO)Fe]2L154l Diphos and two... [Pg.145]

The following tables summarize the silicon-transition-metal compounds known up to 1973. The abbreviations used for organic substituents are me = CH3, et = C2Hs, pr = C3H7, bu = C4H10, ph = C6H5,bz = CH2C6Hs, cp = w-cyclopentadienyl, diphos = l,2-bis(diphenylphosphino)-ethane. [Pg.153]

Trans-bromo structures are also found in the similar ditertiary phosphine bidentate complex [MnBr2(dmpe)2] (dmpe = l,2-bis(dimethylphosphino)ethane) 28 the Mn—P bond length in this compound (2.655 A) being comparable with that found in [MnCl2(diphos)2] (2.625 A). The reaction of [MnBr2(dmpe)] with LiAlH4 yields a Mn1 compound of stoichiometry Mn(AlH4)(dmpe)2 (Section 41.2.4). [Pg.32]


See other pages where DIPHOS ethane is mentioned: [Pg.27]    [Pg.185]    [Pg.402]    [Pg.423]    [Pg.353]    [Pg.23]    [Pg.58]    [Pg.10]    [Pg.293]    [Pg.579]    [Pg.329]    [Pg.17]    [Pg.176]    [Pg.414]    [Pg.81]    [Pg.207]    [Pg.311]    [Pg.36]    [Pg.298]    [Pg.347]    [Pg.138]    [Pg.142]    [Pg.124]    [Pg.52]    [Pg.69]    [Pg.69]    [Pg.58]    [Pg.467]    [Pg.122]    [Pg.136]    [Pg.12]    [Pg.62]    [Pg.62]    [Pg.217]    [Pg.206]    [Pg.281]    [Pg.10]    [Pg.202]    [Pg.1234]   
See also in sourсe #XX -- [ Pg.551 ]




SEARCH



© 2024 chempedia.info