Tantalum complexes allyl

Tantalum(v) chloride can be used in the generation of 72-alkyne complexes (general formula 118) which have been shown to react with aldehydes to afford, after basic aqueous workup, allylic alcohols 119 (Scheme 50).180... 

Di(carbene)gold(I) salts, oxidation, 2, 293—294 Dicarbido clusters, with decarutheniums, 6, 1036 Dicarbollide amides, with tantalum, 5, 184 Dicarbollide thorium complexes, synthesis and characterization, 4, 224—225 Dicarbollyl ligands, in nickel complexes, 8, 185 Dicarbonyl complexes arylation with lead triacetates diastereoselectivity, 9, 389 enantioselectivity, 9, 391 mechanisms, 9, 387 reaction examples, 9, 382 indium-mediated allylation, 9, 675 with iridium, 7, 287 reductive cyclization, 10, 529 in Ru and Os half-sandwiches, 6, 508 with Zr—Hf(II), 4, 700... 

Trisubstituted allylic alcohols. A low-valent tantalum prepared by reduction of TaCIs with Zn in DME/benzene adds to alkynes to form a complex that reacts with aldehydes to form (E)-allylic alcohols. The regioselectivity is determined by the bulkiness of the groups on the alkyne and of the R group of the aldehyde. 

Treatment of tantalum-alkyne complexes, prepared in situ from TaCls, Zn and RC=CR (R = n-C5Hn), with the lithio-imine Li N=CR Me (R = n-CgHn), followed by aqueous NaOH, gives primary ( )-allylic amines E-RCH=CR-CR Me(NH2). Treatment of these complexes with the terminal alkyne R"C=CH (R" = n-CeHis), followed by aqueous NaOH, yields tetrasubstituted benzene derivatives (99a-d). ... 

Epoxidations. Grafting tantalum onto silica to form a useful catalyst for the Sharpless asymmetric epoxidation of allyl alcohols is contrary to the ineffective titanium species on a similar support. Vanadium-complexed chiral hydroxamic... 

The combined action of zinc and tantalum(V) chloride on alkynes generates low-valent tantalum-alkyne complexes, which react with carbonyl compounds to yield ( )-allylic alcohols stereoselectively. The tantalum-6-dodecyne complex, for instance, and j -phenyl-propionaldehyde afford the alcohol 370 in 96% yield. Mixtures of structurally isomeric a,/ -unsaturated ( )-amides 371 and 372 (R, = alkyl or Mc3Si) are obtained from the... 

Properties M.w. 184.31 sp.gr. 0.993-0.997 b.p. 95-97 C (13 mm Hg) ref. index 1.579 Toxicology TSCA listed Uses Reducing agent for prep, of silyl-substituted alkylidene complexes of tantalum, in ionic reduction of enones to sat. ketones, in reductive cyclization of unsat. ketones, for esters in presence of zinc hydride catalyst, for o-halo ketones in presence of Mo(0), reduction of thio esters to ethers, esters to alcohols with Rh catalysis, in assym. reduction of methyl ketones, reductive cleaving of allyl acetates Manuf./Distrib. ABCR http //www.abcr.de, Alfa Aesar http //www.aifa.com-. Digital Spec. Chems. http //www.digHaichem.com, Fluorochem USA... 

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. 

Reaction of but-2-yne with [(RNH)(RN=)2V(OEt2)] (R = Bu 3Si) resulted 33 in displacement of the diethyl ether ligand and formation of [(RNH)(RN=)V C(Me>=C(Me)N(R))l which underwent ligand metallation to afford the ri -i-azaallyl complex (15). The synthesis and reactions of the 16-electron bis-(Ti3-allyl) tantalum species [Cp Ta( n3.phCHCHCH2)2] have been reported 34 and the X-ray crystal structure determined 35. 

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