Cyclopentadienyl product

The cyclopentadienyl products were sublimed out of the reaction mixture and characterized by powder diffraction data, showing they were isostructural with the corresponding LnCp3 (Ln = Pr, Sm, Gd). 

C-C bond-forming reactions do not, however, always involve spirocyclic intermediates. The cyclopentadienyl product 111 is obtained during the depalladation of 110, derived from a thermally induced 1,3-H shift of its isomer 114. Here, PPhj plays a role similar to that of pyridine or maleic anhydride, in that it displaces the quinoline unit bound to palladium and, hence destabilizes the metallacyclic unit. The carbocyclic product 111 is assumedly formed as a result of an intramolecular C-H activation of the ri -bound olefin unit assisted by the proximity of the... 

Addition of one equivalent of an internal allqtne, trichloro(l,2-dimethoxyethane-0,0 )-(2,2-dimethylpropylidyne)tungsten(VI) affords a stable tungstacyclobutadiene product, but reaction with additional alkyne yields q -cyclopentadienyl products of further alkyne insertion rather than products of allcyne metathesis.l l... 

The catalytic reaction described in Figure 2 will follow a different course when the olefin R(—H) is strongly attached to the metal in the complex 19. This is certainly what happens with cyclopentene which is a better ligand than the larger cycloalkenes here, further dehydrogenation of 19 gives the cyclopentadienyl product 15. 

Organochromium Catalysts. Several commercially important catalysts utilize organ ochromium compounds. Some of them are prepared by supporting bis(triphenylsilyl)chromate on siUca or siUca-alumina in a hydrocarbon slurry followed by a treatment with alkyl aluminum compounds (41). Other catalysts are based on bis(cyclopentadienyl)chromium deposited on siUca (42). The reactions between the hydroxyl groups in siUca and the chromium compounds leave various chromium species chemically linked to the siUca surface. The productivity of supported organochromium catalysts is also high, around 8—10 kg PE/g catalyst (800—1000 kg PE/g Cr). 

Photolysis of Cp2TiAr2 in benzene solution yields titanocene and a variety of aryl products derived both intra- and intermolecularly (293—297). Dimethyl titan ocene photolyzed in hydrocarbons yields methane, but the hydrogen is derived from the other methyl group and from the cyclopentadienyl rings, as demonstrated by deuteration. Photolysis in the presence of diphenylacetylene yields the dimeric titanocycle (28) and a titanomethylation product [65090-11-1]. 

A more effective control of both simple diastereoselectivity and induced stereoselectivity is provided by the titanium enolate generated in situ by transmetalation of deprotonated 2,6-dimethylphenyl propanoate with chloro(cyclopentadienyl)bis(l,2 5,6-di-0-isopropylidene-a-D-glucofuranos-3-0-yl)titanium. Reaction of this titanium enolate with aldehydes yields predominantly the. yyw-adducts (syn/anti 89 11 to 97 3). The chemical yields of the adducts are 24 87% while the n-u-products have 93 to 98% ee62. 

Reactions of the cyclopentadienyl-amidinate-supported imidotitanium complexes with CO2 proceed via initial cycloaddition reactions, but depending on the imido Af-substituent go on to yield products of either isocyanate extrusion or unprecedented double CO2 insertion (Scheme 89). ... 

In contrast to other organothallium(I) compounds, cyclopentadienyl-thallium(I) is a remarkably stable compound. Samples can be stored in sealed bottles for months without appreciable decomposition occurring it is unaffected by water and dilute alkali and it is only slowly oxidized by air at room temperature. Cyclopentadienyltballium(I) was first prepared by Meister in 1956 by addition of freshly distilled cyclopentadiene to a suspension of thallium(I) sulfate in dilute potassium hydroxide solution 101, 102). A number of variations of this procedure have been described (5, 25, 34, 56), and the compound has been made in other ways 35, 56,110, 164), but Meister s preparation, in which the yield of crude product is greater than 90%, remains the method of choice. Purification of crude cyclopenta-dienylthallium(I) is best accomplished by vacuum sublimation, and purity of samples can readily be assessed by gas-liquid chromatography on silicone oil at 170° C using hydrogen as carrier gas (7). 

The ability to control the polymer from the design of the catalyst, coupled with high catalytic efficiency has led to an explosion of commercial and academic interest in these catalysts. Exxon started up a 30 million lb/5rr ethylene copol3rmer demonstration plant in 1991 using a bis-cyclopentadienyl zirconium catalyst of structure 1. The Dow Chemical Company (Dow) began operating a 125 million Ib/yr ethylene/l-octene copolymer plant in 1993 and has since expanded production capacity to 375 million Ib/yr. This paper will focus on the structure / property relationships of the catalysts used by Dow to produce single-site ethylene a-olefin copolymers. 

The IR spectra of the polymer (P) contained two sharp absorptions near 1000 and 1100 cm-- -, indicative of the presence of unsubstituted cyclopentadienyl rings in the products. The 250-MHz - -H-NMR spectrum, shown in Figure 3, contained the expected peaks for the methyl, methylene, and cyclopentadienyl protons, respectively, at 61.52, 1.57 and 4.04 ppm. No olefinic proton resonances were present, and all of the samples of the polymer in Table II exhibited the same - -H-NMR spectrum. 

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