Chromium phenylate

An organometallic dioxygen adduct of an even more fleeting kind was observed in the reaction of the divalent chromium phenyl complex Tp > Cr-... 

Scheme 3 Formation of a chromium phenyl superoxo intermediate and a stable analog thereof...

Scheme 12 Intramolecular O2 insertion into chromium phenyl bond yield 0x0 alkoxide...

Several reactions of metal-carbene complexes with alkynes leading to five-membered ring compounds have been described. The action of acetylenes on the chromium phenyl(pyrrolidino)carbene complex 472 results in mixtures of indanones 473 and indenes 474297 Terminal alkynes (pent-l-yne or hex-l-yne) react with the molybdenum carbene complex 475 to afford, after oxidative work-up, indanones 476 in contrast, trimethylsilylacetylene gave only the naphthoquinone 477. ... 

Treatment of chromium(III) chloride with phenylmagnesium bromide under an atmosphere of carbon monoxide provided a route to chromium hexacarbonyl (Job-Cassels reaction). When this reaction was carried out under nitrogen it was possible to isolate organochromium complexes, but these are now known to be rj -arene compounds, formed via unstable chromium phenyls (see p. 314). 

Crpc=pentacarbonyl-chromium-phenyl-carbenyl, see K. WeiS, E.O. Fischer, Chem. Ber. 1976, 109,1868 and references therein. 

The product is the isomer with the two phenyl groups cis to each other, since decarboxylation with quinoline-copper chromium oxide at 210-220° yields cis-stilbene. 

In equation 1, the Grignard reagent, C H MgBr, plays a dual role as reducing agent and the source of the arene compound (see Grignard reaction). The Cr(CO)g is recovered from an apparent phenyl chromium intermediate by the addition of water (19,20). Other routes to chromium hexacarbonyl are possible, and an excellent summary of chromium carbonyl and derivatives can be found in reference 2. The only access to the less stable Cr(—II) and Cr(—I) oxidation states is by reduction of Cr(CO)g. 

Pyridazines form complexes with iodine, iodine monochloride, bromine, nickel(II) ethyl xanthate, iron carbonyls, iron carbonyl and triphenylphosphine, boron trihalides, silver salts, mercury(I) salts, iridium and ruthenium salts, chromium carbonyl and transition metals, and pentammine complexes of osmium(II) and osmium(III) (79ACS(A)125). Pyridazine N- oxide and its methyl and phenyl substituted derivatives form copper complexes (78TL1979). 

UV irradiation. Indeed, thermal reaction of 1-phenyl-3,4-dimethylphosphole with (C5HloNH)Mo(CO)4 leads to 155 (M = Mo) and not to 154 (M = Mo, R = Ph). Complex 155 (M = Mo) converts into 154 (M = Mo, R = Ph) under UV irradiation. This route was confirmed by a photochemical reaction between 3,4-dimethyl-l-phenylphosphole and Mo(CO)6 when both 146 (M = Mo, R = Ph, R = R = H, R = R" = Me) and 155 (M = Mo) resulted (89IC4536). In excess phosphole, the product was 156. A similar chromium complex is known [82JCS(CC)667]. Complex 146 (M = Mo, R = Ph, r2 = R = H, R = R = Me) enters [4 -H 2] Diels-Alder cycloaddition with diphenylvinylphosphine to give 157. However, from the viewpoint of Woodward-Hoffmann rules and on the basis of the study of UV irradiation of 1,2,5-trimethylphosphole, it is highly probable that [2 - - 2] dimers are the initial products of dimerization, and [4 - - 2] dimers are the final results of thermally allowed intramolecular rearrangement of [2 - - 2] dimers. This hypothesis was confirmed by the data obtained from the reaction of 1-phenylphosphole with molybdenum hexacarbonyl under UV irradiation the head-to-tail structure of the complex 158. 

If the reaction temperature is raised to 430 K and the carbon monoxide pressure to 3 atm, coordination of the metal atom in the rearranged product occurs via the phosphorus site, as in 159 (M = Cr, Mo, W) [84JOM(263)55]. Along with this product (M = W) at 420 K, formation of the dimer of 5-phenyl-3,4-dimethyl-2//-phosphole, 160 (the a complex), is possible as a consequence of [4 - - 2] cycloaddition reactions. Chromium hexacarbonyl in turn forms phospholido-bridged TiyP)-coordinatedcomplex 161. At 420 K in excess 2,3-dimethylbutadiene, a transformation 162 163 takes place (82JA4484). 

Dimesitylimidazolium chloride with chromocene gives the carbene 32 (R = C1) (990M529). With phenylmagnesium chloride, 32 (R = C1) gives 32 (R = Ph), the product of substitution of the chloride ligand by phenyl radical. In chloroform, 32 (R = C1) gives the chromium(III) species 33. In contrast,... 

Both R and MMA radicals are found to be responsible for the photoinitiation process. Chaturvedi and coworkers [54,55] introduced phenyl dimethyl sulfonium-ylide cupric chloride and chromium thiophene carboxylate as the photoinitiator of styrene and MMA. No reaction mechanism was given for these systems. 

Determination of tungsten as the trioxide (tannic acid-phenazone method) Discussion. Tungstic acid is incompletely precipitated from solutions of tungstates by tannic acid. If, however, phenazone (2,3-dimethyl-l-phenyl-5-pyrazolone) is added to the cold solution after treatment with excess of tannic acid, precipitation is quantitative. This process effects a separation from aluminium, and also from iron, chromium, manganese, zinc, cobalt, and nickel if a double precipitation is used. 

Pyrazolone, l-phenyl-3-methyl-4-(2-carboxyphenylazo)-chrotnium complex geometrical isomerism, 6, 68 5-Pyrazolone, l-phenyl-3-methyl-4-(2-hydroxy-4-sulfonaphth-l-ylazo)-chromium complex... 

Aumann et al. showed that 1,2,4-tridonor-substituted naphthalenes, such as 126, are accessible from 3-donor-substituted propenylidenecarbene complexes 124 containing a (Z)-positioned 3-phenyl substituent and isocyanide (Scheme 26). These transformations constitute formal [5+1] cycloadditions [39, 89, 90]. Since isocyanides are strongly coordinating ligands on chromium, at least... 

Structural analogues of the /]4-vinylketene E were isolated by Wulff, Rudler and Moser [15]. The enaminoketene complex 11 was obtained from an intramolecular reaction of the chromium pentacarbonyl carbene complex 10. The silyl vinylketene 13 was isolated from the reaction of the methoxy(phenyl)-carbene chromium complex 1 and a silyl-substituted phenylacetylene 12, and -in contrast to alkene carbene complex 7 - gave the benzannulation product 14 after heating to 165 °C in acetonitrile (Scheme 6). The last step of the benzannulation reaction is the tautomerisation of the /]4-cyclohexadienone F to afford the phenol product G. The existence of such an intermediate and its capacity to undergo a subsequent step was validated by Wulff, who synthesised an... 

Other miscellaneous imines that underwent photoreaction with chromium alkoxycarbenes include iminodithiocarbonates [33],the mono-N-phenylimine of benzil and the bis-JV-phenyl imine of acetoin [20]. By preparing the chromium carbene complex from 13CO-labeled chromium hexacarbonyl, /J-lactams with two adjacent 13C labels were synthesized [34]. 

Carboxylic acids, a-bromination of 55, 31 CARBOXYLIC ACID CHLORIDES, ketones from, 55, 122 CARBYLAMINE REACTION, 55, 96 Ceric ammonium nitrate [Ammonium hexa mtrocerate(IV)[, 55, 43 Chlorine, 55, 33, 35, 63 CHROMIUM TRIOXIDE-PYRIDINE COMPLEX, preparation in situ, 55, 84 Cinnamomtnle, a-phenyl- [2-Propeneni-tnle 2,3-diphenyl-], 55, 92 Copper(l) iodide, 55, 105, 123, 124 Copper thiophenoxide [Benzenethiol, copper(I) salt], 55, 123 CYCLIZATION, free radical, 55, 57 CYCLOBUTADIENE, 55, 43 Cyclobutadieneiron tricarbonyl [Iron, tn-carbonyl(r)4-l,3-cyclo-butadiene)-], 55,43... 

Nickel and palladium react with a number of olefins other than ethylene, to afford a wide range of binary complexes. With styrene (11), Ni atoms react at 77 K to form tris(styrene)Ni(0), a red-brown solid that decomposes at -20 °C. The ability of nickel atoms to coordinate three olefins with a bulky phenyl substituent illustrates that the steric and electronic effects (54,141) responsible for the stability of a tris (planar) coordination are not sufficiently great to preclude formation of a tris complex rather than a bis (olefin) species as the highest-stoichiometry complex. In contrast to the nickel-atom reaction, chromium atoms react (11) with styrene, to form both polystyrene and an intractable material in which chromium is bonded to polystyrene. It would be interesting to ascertain whether such a polymeric material might have any catal3dic activity, in view of the current interest in polymer-sup-ported catalysts (51). 

In contrast, when chromium atoms were reacted with benzyl ether, complexation to only one phenyl group of the ether was observed. 

Recently Mosher and Driscoll 2 have noted that the polymerization of acrylonitrile can be observed during the chromic acid oxidation of 2,2-dimethyl-l-phenyl-l-propanol. The polymerization is caused by radicals formed during the oxidation of benzaldehyde (which is one of the cleavage product of phenyl-1-butylcarbinol). The oxidation of benzaldehyde is due to the chromium(IV), most probably, or chromiun(V) intermediates. 

Pentacarbonyl[phenyl(methoxy)carbene]chromium was prepared by the checkers in 75% yield according to the literature Hegedus, L. S. McGuire, M. A. Schultze, L. M. Org. Synth. 1987, 65,140. This material was stored under nitrogen at -30°C and purified immediately prior to use by filtration through a plug of Celite (hexane solvent). If the chromium carbene is purchased from Aldrich Chemical Company, Inc., the submitters found it was only 65% pure based on capillary GLC analysis. 

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