III Acetylacetonate

CO(NH2)2 + H20- 2NH3 + C02 CrCl3 + 3CjH802 + 3NH3- Cr(C6H702)2 + 3NH4C1 

Checked by Burl E. BryantI and Kazuji TERADA.f and by Russell S. Dr ago J and John K. Stiller 

Previous preparations of chromium (III) acetylacetonate have involved the treatment of freshly precipitated hydrous chromium(III) oxide with acetylacetone.1,2 The preparation presented here was suggested by Cooperstein3 and involves exact pH control through the homogeneous generation of ammonia (by the hydrolysis of urea) in a solution of a chromium(III) salt and acetylacetone. The operations involved are simple and easy to perform. 

To 100 ml. of water are added 2.66 g. of chromium(III) chloride 6-hydrate (0.01 mol) and, after complete solution, 

of urea and 6 g. of acetylacetone (0.06 mol). The reaction mixture is covered with a watch glass and heated overnight on a steam bath. As the urea hydrolyzes to release ammonia, deep maroon platelike crystals form. These are removed by suction filtration and dried in air. 

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Chromium (III) tris-2,4-pentanedionate [21679-31-2] chromic chloride). See chromium (III) acetylacetonate on p. 412. 

Highly active gold catalysts can be prepared by an appropriate selection of preparation methods such as CP, DP, DR, and SG with dimethyl Au(III) acetylacetonate, depending on the kind of support materials and reactions... 

Komiya, S., and Kochi, J.K. (1977) Reversible linkage isomerisms of p-diketonato ligands. Oxygen-bonded and carbon-bonded stmctures in gold(III) acetylacetonate complexes induced by phosphines. Journal of the American Chemical Society, 99, 3695. 

Chromium(III) acetylacetonate, physical properties, 6 528t Chromium alloys, 6 468-523 Chromium alumina pink corundum, formula and DCMA number, 7 347t Chromium antimony titanium buff rutile, formula and DCMA number, 7 347t Chromium-based catalysts, 20 173 Chromium baths, 9 800-804... 

Fig. 4.15 The system La(III) acetylacetone (HA) - IM NaC104/benzene at 25°C as a function of lanthanide atomic number Z. (a) The distribution ratio Hl (stars, right axis) at [A ] = 10 and [HA] rg = 0.1 M, and extraction constants (crosses, left axis) for the reaction Ln + 4HA(org) LnA3HA(org) + 3FE. (b) The formation constants, K , for formation of LnA " lanthanide acetylacetonate complexes (a break at 64Gd is indicated) circles n = 1 crosses n = 2 triangles w = 3 squares w = 4. (c) The self-adduct formation constants, for the reaction of LnA3(org) + HA(org) LnA3HA(org) for org = benzene. (A second adduct, LnA3(HA)2, also seems to form for the lightest Ln ions.) (d) The distribution constant Ajc for hydrated lanthanum triacetylacetonates, LnAs (H20)2 3, between benzene and IM NaC104. (From Ref. 28.)...

Traditional Ziegler-Natta syndioselective homogeneous vanadium initiators such as vanadium(III) acetylacetonate with A1(C2H5)2C1 yield living polymerizations at low temperatures (<—60°C) [Doi, 1986 Hagen et al., 2002]. 

Cobalt (III) acetylacetonate [Co(acac)3] (14), manganese (III) acetylacetonate [Mn(acac)3] (15), iron(III) acetylacetonate [Fe(acac)3] (30), chromium(III) acetylacetonate [Cr(acac)3] (13), nickel(II) acetylacetonate [Ni(acac)2] (8), and copper (II) acetylacetonate [Cu(acac)2] (18) were prepared and purified. Cobalt, manganese, iron, chromium, nickel, and copper naphthenates were all commercially available. 

The oxidation proceeded smoothly when catalyzed by a metallic ion, with the exception of chromium (III) acetylacetonate, which is entirely inactive in promoting the reaction. This may be attributed to... 

The results published thereafter by Kochi s group are especially interesting from a mechanistic point of view . Indeed, for preparative chemistry the yields are not satisfactory and the reaction is limited to reactive alkenyl bromides such as propenyl and styryl bromides (Table 4). Neumann and Kochi were the first to replace iron(III) chloride by iron(III) acetylacetonate or related complexes such as Fe(dbm)3 (iron tris-dibenzoylmethanato) that are less hygroscopic and easier to handle. 

Only 1 to 3% iron(III) acetylacetonate are required and the scope of the reaction is very large. A vast array of alkenyl iodides, bromides and even chlorides can be successfully used and the stereoselectivity is excellent even in the case of the Z-alkenyl halides (Scheme 19). 

In 2002, Figad re and coworkers reported the mono-reduction of 2-aryl (or heteroaryl)-1,1-dibromo-l-alkenes (Scheme 23). The reaction is achieved with one equivalent of isopropylmagnesium chloride in the presence of iron(III) acetylacetonate. Pure ( )-alkenyl bromides are obtained. With two equivalents of alkyl Grignard reagent, the mono-substituted product is obtained in moderate yield. 

In 2007, Cahiez and coworkers disclosed two new catalytic systems to improve the reaction, especially for large-scale syntheses. In the first catalytic system, iron(III) acetylacetonate is used instead of iron(III) chloride. In addition, the use of hexamethylenetetramine (HMTA, 5%), a very cheap new ligand, allows one to significantly lower the amount of TMEDA (10% instead of 120%) (Scheme 42). This catalytic system is based on a synergy between TMEDA and HMTA. 

Yamamoto and coworkers studied the substitution of ally lie phosphates by Grignard reagents in the presence of copper or iron salts. Only the Sn2 product is formed under copper catalysis whereas, in the presence of iron(III) acetylacetonate, the Sn2 product is generally obtained with an excellent selectivity (Scheme 49). It should be noted that aryl-, alkenyl-, aUcynyl- and aUcyhnagnesium halides can be used successfully. 

In 2003, FUrstner and Mdndez reported an elegant reaction between optically active propargyhc epoxides and organomagnesium compounds in the presence of iron(III) acetylacetonate (Scheme 50). Interestingly, the chirality of the starting product is transferred to the final 2,3-allenols which are obtained with a good enantiomeric purity. 

During a study of the reactions of aromatic hydrocarbons with the hydrides formed by reducing cobalt(III) acetylacetonate with triisobuty-laluminum, Tyrlik and Michalski (98) observed that some of the cumene solvent is converted to ethylbenzene, e.g.,... 

A search of the literature revealed two instances in which metal acetylaceto-nate rings had been substituted without degradation of the chelate rings. Treatment of chromium (III) acetylacetonate with bromine in chloroform had been reported to yield two products—a tribromo- and a hexabromochelate (III and IV) (31). These structures were assigned on the basis of halogen analyses. Later work simultaneous with our own revealed that IV was actually a chloroform solvate of III (24). 

Treatment of chromium (III) acetylacetonate with acetic anhydride and boron trifluoride etherate yielded a complex mixture of acetylated chelates but very little starting material. Fractional crystallization and chromatographic purification of this mixture afforded the triacetylated chromium chelate (XVI), which was also prepared from pure triacetylmethane by a nonaqueous chelation reaction (8, 11). The enolic triacetylmethane was prepared by treating acetylacetone with ketene. The sharp contrast between the chemical properties of the coordinated and uncoordinated ligand is illustrated by the fact that chromium acetylacetonate does not react with ketene. 

It is concluded that mechanism B is unlikely, since no total racemization was found in the reactions of chromium (III) and cobalt (III) acetylacetonates with a variety of electrophiles, and that these reactions occur in the same manner as in an aromatic system. 

To understand how the value of g and g are obtained from the experimental spectra, we shall consider their determination for Ti3+ in a single crystal of aluminium (III) acetylacetonate. This crystal is monoclinic with two molecules per unit cell. The trigonal axes of the two molecules in the unit cell point in different directions, and thus in general two absorption lines will be seen. In Fig. 6 are shown the orientations of the appropriate... 

CL2099). Dihydrofurans (67) were synthesized by a photochemical reaction of enamines with metallic complexes of diketones (83CL1499). As an example, the reaction with cobalt(III) acetylacetonate is presented. 

Friedel—Crafts acetylation can be achieved, but the introduction of one acetyl group deactivates the remaining chelate rings so that mixtures of mono-, di- and tri-acetyl products are formed in the case of chiomium(III) and cobalt(III) complexes, but only mono- and di-acetyl products from rhodium(III) acetylacetonate. 

Hexaammineplatinum(IV) salts also undergo imine-forming reactions with acetylacetone (equation 49).172 A cobalt(III) acetylacetone complex can be formed as a result of intramolecular addition of cobalt-bound hydroxide ion to acetylacetone. The cobalt-bound oxygen atoms are retained in the new chelate ring (equation 50).173... 

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