Osmium complexes allyl

Allyl bromide, irradiation of, 5 156 Allyl complexes, osmium, 37 244 ligand-centered reactions, 37 343 7t-Allyl derivatives, proton chemical shifts of, 4 182... 

Much use has also been made of the zero-valent metal complexes as metal precursors, where it is thought advisable to avoid chloride or other possible harmful ions the carbonyls of ruthenium, rhodium, osmium, and iridium (of which there are many) have been used either as vapour if that is possible, or more often as solutions in organic solvents. °° ° ° Acetylacetonate (acac) complexes and r-allylic complexes have also been used. The term chemical vapour deposition (CVD) is used when the vapour of a volatile complex reacts with a support... 

The reactions of allenes and dienes with iron and ruthenium compounds form a large number of various allyl complexes (see allene complexes). Osmium forms allyl compounds of the formulas [OsCl(C3H5)(PPh3)3] and [Os(C8Hg)(CO)3]. 

The following metal compounds are used for the preparation of the catalysts oxides, metal carbonyls, halides, alkyl and allyl complexes, as well as molybdenum, tungsten, and rhenium sulfides. Oxides of iridium, osmium, ruthenium, rhodium, niobium, tantalum, lanthanum, tellurium, and tin are effective promoters, although their catalytic activity is considerably lower. Oxides of aluminum, silicon, titanium, manganese, zirconium as well as silicates and phosphates of these elements are utilized as supports. Also, mixtures of oxides are used. The best supports are those of alumina oxide and silica. 

Ruthenium and Osmium 77 -Complexes 6.13.4.1 Parent Allyl Complexes... 

A catalytic enantio- and diastereoselective dihydroxylation procedure without the assistance of a directing functional group (like the allylic alcohol group in the Sharpless epox-idation) has also been developed by K.B. Sharpless (E.N. Jacobsen, 1988 H.-L. Kwong, 1990 B.M. Kim, 1990 H. Waldmann, 1992). It uses osmium tetroxide as a catalytic oxidant (as little as 20 ppm to date) and two readily available cinchona alkaloid diastereomeis, namely the 4-chlorobenzoate esters or bulky aryl ethers of dihydroquinine and dihydroquinidine (cf. p. 290% as stereosteering reagents (structures of the Os complexes see R.M. Pearlstein, 1990). The transformation lacks the high asymmetric inductions of the Sharpless epoxidation, but it is broadly applicable and insensitive to air and water. Further improvements are to be expected. 

Figure 2.5 Schematic representation of the Au/MPS/PAH-Os/solution interface modeled in Refs. [118-120] using the molecular theory for modified polyelectrolyte electrodes described in Section 2.5. The red arrows indicate the chemical equilibria considered by the theory. The redox polymer, PAH-Os (see Figure 2.4), is divided into the poly(allyl-amine) backbone (depicted as blue and light blue solid lines) and the pyridine-bipyridine osmium complexes. Each osmium complex is in redox equilibrium with the gold substrate and, dependingon its potential, can be in an oxidized Os(lll) (red spheres) or in a reduced Os(ll) (blue sphere) state. The allyl-amine units can be in a positively charged protonated state (plus signs on the polymer...

Allyl hydride complexes of osmium are isolated from treatment of phosphine-substituted osmacyclobutane complex 114 with a thallium salt (Scheme 21). The reaction initially provides a mixture of an unstable -benzyl hydride complex 115 and the rf -allyl hydride complex 116 the -benzyl intermediate ultimately isomerizes to the latter complex, a very rare instance of isolable allylic hydride products generated from a starting metallacyclobutane <2004OM4858>. 

Table VI lists the known trifluoroacetato complexes of iron, ruthenium, and osmium. Photochemical substitution reactions of various tricovalent phosphorus-donor ligands with (7r-allyl)Fe(C0)2(02CCF3) and (iT-Cp)Fe(C0)3(02CCF3), analogous to those described in the preceding for Mn(C0)5(02CCF3), have afforded (ir-allyl)Fe(CO)(cis-Ph2PCH=CHPPh2)(02CCF3), (7r-Cp)Fe(C0)(PR3)(02CCF3) (where...

Fig. 20. A 3-dimensional representation of allyl 4-methoxybenzoate bound in the (DHQD)2-PDZ-osmium tetroxide complex...

Epoxidation of allylic and homoallylic alcohols not part of the diene complex can be achieved using the Sharpless r-butyl hydroperoxide/vanadium acetylacetonate protocol. Dihydroxylation of alkenes adjacent to the diene complex using osmium tetraoxide-7-butyl peroxide has been reported... 

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