Chromium, tetrakis

Chromium, tetraaquadichloro-chloride dihydrate hydrate isomerism, 1, 183 Chromium, tetrabromo-solvated, 3, 758 synthesis, 3, 763 Chromium, tetrachloro-antiferromagnetic, 3, 761 ferromagnetic magnetic properties, 3,7559 optical properties, 3,759 structure, 3,759 solvated, 3. 758 synthesis. 3, 759 Chromium, tetrachlorooxy-tetraphenylarsenate stereochemistry, 1,44 Chromium, tetrahalo-, 3,889 Chromium, tetrakis(dioxygen)-stereochemistry, 1,94 Chromium, triamminediperoxy-structure. 1, 78 Chromium, tricyanodiperoxy-structure, 1, 78 Chromium, trifluoro-electronic spectra, 3, 757 magnetic properties, 3, 757 structures, 3, 757 synthesis, 3, 756 Chromium, trihalo-clcctronic spectra, 3, 764 magnetic properties, 3, 764 structure, 3, 764 synthesis, 3, 764 Chromium, tris(acetylacetone)-structure. 1, 65 Chromium, tris(bipyridyl)-... 

FgCrNsOgSsCizHzi, Chromium(III), (N,N, N"-trimethyl-1,4,7-triazacyclononane)tris(tri-fluoromethanesulfonato)-, 34 152 Fi2FegN4PioS4Ci28Hii6, Iron, tetrakis /i-... 

HOMOALLYLIC ALCOHOLS Cerium amalgam. Chromium(II) chloride. Fluorodimethoxyborane. Hypochlorous acid. Lithium bronze. Manganesc(II) chloride-Lithium aluminum hydride. Methylenetriphenylphosphorane. Organotitanium reagents. Tetrakis(triphenylphosphine)palladium. Tin. Tin(II) fluoride. 

Tetrakis(bromomethyl)-9,9-dimethyl-l,2,4,5,7,8-hexoxonane, 3167 Tetrakis(butylthio)uranium, 3725 Tetrakis(chloroethynyl)silane, 2874 Tetrakis(A, A -dichloroaminomethyl)methane, 1894 Tetrakis(diethylphosphino)silane, 3727a Tetrakis(dimethylamino)titanium, 3098 Tetrakis(2,2-dimethylpropyl)chromium, 3808b Tetrakis(ethylthio)uranium, 3090... 

Tetrakis(trimethylsilylmethyl)chromium, 3727b Tetrakis(2,2,2-trinitroethyl)orthocarbonate, 3126 Tetramethoxyethylene, 2511... 

Wilkinson (9) isolated the tetrakis(trihalogenophosphine)nickel compounds Ni(PX3)4 (X= F, Cl, Br), and Behrens (10) isolated the triphenylphosphine complex Ni[P(C6H5)3]4 via [Ni(CN)4]4. With iron pentacarbonyl, isonitriles and phosphines yield (11) mono- and disubstituted derivatives, Fe(CO)4L and Fe(CO)3L2, respectively, the latter being the well-known cyclization catalyst of Reppe (7). With the same ligands, carbonyls of the chromium group afforded pentacarbonyl derivatives M(CO)5L. However,... 

The crystal structure of [Cr(CH2CMe2Ph)4] has been determined and the CrIV atom shown to be co-ordinated by a slightly distorted tetrahedron of carbon atoms (Cr—C = 205 pm).220 The e.s.r. spectrum of tetrakis-(l-norbornyl)chromium(iv) has been recorded for the compound contained in organic glasses at low temperatures. 

Moran et al. 41 attached the Cr(CO)3 moiety to tetrakis(phenylsilane) 32 (prepared by the hydrosilylation of tetraallylsilane with four equivalents of dimethylphenylsilane) by treatment with excess Cr(CO)6 in dibutyl ether—THF at 140 °C affording the air-stable, crystalline tetrakis(chromium carbonyl) dendrimer 33, which was also prepared by reaction of tetraallylsilane with [r76-C6H5Si(Me)2H]Cr(CO)3) (Scheme 8.9). 42a Reaction of the corresponding eight phenyl-terminated analogues afforded the partially metalated silane dendrimer 34 as the major product, even with an excess of Cr(CO)6. 

The tetrafunctional alcohol pentaerythritol is a popular core in dendrimer chemistry it has been modified into a tetrakis chromium phenylcarbene 85, which underwent a quadruple benzannulation upon reaction with 3-hexyne. The reaction proceeded with only moderate diastereoselectivity in terms of the planes of chirality formed demetalation by mild oxidative work-up gave the tetrakis-hydroquinone derivative 86 (Scheme 33) [76]. 

Interestingly, although the reaction of 1,3-cyclohexadiene, chromium atoms, and PF3 yields bis(//4-cyclohexadiene)bis(trifluorophos-hine)chromium, the corresponding reaction with 1,4-cyclohexadiene yields the //5-cyclohexadienyl hydrido tris(trifluorophosphine)-chromium complex, which rearranges in the presence of silica gel to form [Cr( 4-C6H8)2(PF3)2] rather than (i/4-cyclohexadiene)tetrakis-(trifluorophosphine)chromium (40) (Scheme 2). 

Reaction of chromium atoms, l,5-cyclooctadiene(l,5-cod), and PF3 on the other hand yielded a separable mixture of [Cr(C8Hu)(PF3)3H] and (j74-cycloocta-l,5-diene)tetrakis(trifluorophosphine)chromium. The latter is readily converted to the former by warming a solution of it to 90°C (Scheme 3). This rearrangement is impaired under an atmosphere of PF3 and the 1,5-cod is preferentially displaced to give [Cr(PF3)6]. 

Many chromium oxidants suffer from problems of stability, light sensitivity or acidity, but tetrakis(py-ridine)silver dichromate is stable, nonphotosensitive, nonhygroscopic and a neutral oxidant It can be used to oxidize allylic and benzylic alcohols selectively in benzene. Unfortunately, it cannot be used in chlorinated solvents because it decomposes in these solvents. 

Co4Cl6N,2O32C4H40 5H2O, Cobalt(III), p4-(acetylenedicarboxylato)tetra-p-hy-droxo-tetrakis[triammine-, hexaperchlorate, pentahydrate, 23 115 CrAs04PC34H32, Chromium, tetracar-bonyl(tributylphosphine)(triphenyl-arsine)-, trans-, 23 38... 

G. He, T. C. Bruice, The rate-limiting step in the one-electron oxidation of an alkene by oxo[meso-tetrakis(2,6-dibromophenyl)porphinato]chromium(V) is the formation of a charge-transfer complex, /. Am. Chem. Soc. 113 (1991) 2747. 

Another tetravalent compound, tetrakis-(neopentyl)chromium, behaved similarly [295]. It had no activity by itself, but did adsorb on various carriers to yield active catalysts. It reacted slowly with all carriers. Even in contact with fluorided silica-coated alumina, it had to be heated to about 65 °C to start its reaction with the support. Then, gradually, the purple solution adsorbed on the carrier to yield a brown catalyst. Again, the polymerization activity paralleled the reactivity with the support, and the fluorided silica-coated alumina provided catalysts with unusually high polymerization activities. 

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