Cerium acetylacetone

A major factor in ignition of dimethylsilicone oils after heating is the presence of a cyclic trimer. Flash point can be improved by addition of cerium acetylacetonate. 

The sol-gel synthesis of some rare earths oxides has been carried out for the first time in 1971. For the preparation of ceria-based oxides, cerium isopropoxide, cerium acetylacetonate, cerium nitrate are used as the precursors. The water necessary for the hydrolysis reactions is brought in by adding directly or by the hydrated cerium nitrate. Using this method, Ce02, Ce02-PrOx, Ce02-Zr02, and CeOj-... 

The most interesting result is the formation of a transparent colloidal solution of ceria with 2 nm particles. Cerium metal tips with the superficial layers of oxide are allowed to react in 2-methoxyethanol at 250 to 300°C, and removal of coarse ceria particles originating from the superficial layers yields the colloidal solution. Addition of water to the solution does not cause any change except dilution of the color of the solution, but addition of a drop of a solution of any kind of salt immediately causes precipitation of ceria particles. - The reaction mechanism is as follows The solvent slowly dissolves the superficial layers, and when the solvent reaches the metal, rapid reaction occurs, yielding an alkoxide solution. The concentration of the ceria precursor becomes so high that a burst of nucleation occurs, yielding the colloidal solution. The reaction of cerium acetylacetonate in the same solvent yields ceria particles but does not give a colloidal solution. 

It is noteworthy to mention that the oligomerization can also be achieved using mediators as hydroquinones and cerium acetylacetonate in catalytic amounts in solution or a polypyrrole modified electrode. 

Stuart, A. P., Sun Oil Co., Polymerization of Ethylene with Cerium Acetylacetonate-Metal Alkyl Catalyst, U.S. 2921060 [I960] C.A. 1960 12657. 

In a recent paper, Moutarlier et al. [15] have claimed that the use of cerium salts in sol-gel-based corrosion protection is limited due to the high solubility of the cerium ions. In all of the papers cited here, the authors limited themselves to the use of cerium chloride or cerium nitrate. In order to examine the influence of alternative anions, in the present study, cerium sulphate, cerium acetate hydrate (cerium Ac) and cerium acetylacetonate (cerium Acac) have been compared to cerium nitrate and cerium chloride. Additionally, attempts were made to limit the solubility of cerium chloride and cerium nitrate with the addition of acetylacetone to form complexes of the cerium ions. Table 10.1 gives the solubilities of the cerium compounds examined in this study. 

The cerium compounds used for these experiments were cerium acetylacetonate (cerium Acac), cerium nitrate hexahydrate (cerium nitrate), cerium chloride heptahy-drate (cerium chloride), cerium acetate hydrate (cerium Ac) and cerium sulphate. Additionally, cerium nitrate and cerium chloride were dissolved in ethanol and mixed... 

A— 4 wt.% cerium nitrate —A— 4 wt.% cerium nitrate acac - t> 4 wt.% cerium chioride -->--4 wt.% cerium chioride acac 4 wt.% cerium sulphate — —4 wt.% cerium acetylacetonate —4 wt.% cerium acetate... 

Cerium tetrakis(acetylacetonate), a venerable compound,695 exists as a and /3 modifications. Both these contain [Ce(acac)4] monomers of D2 square antiprismatic coordination but differ in the crystal packing. In the a form,696 Ce—0 = 2.36-2.43 A with the ring angle O—Ce— 0 = 72°, while in the / form697 Ce—0 = 2.32 A and O—Ce—0 = 71.3°. The tetrakis(acetyl-acetonates) of Zr, Hf, Th, U and Pu also show dimorphism. The tetrakis(dibenzoylmethanate) [Ce(dbm)4] adopts a similar square antiprismatic structure with Ce—O = 2.299-2.363 A and O—Ce—O = 70.8° or 71,2°.698 There is some tendency for Ce3+ /J-diketonates to pass into the Ce4+ tetrakis(/3-diketonate). A series of tri- and tetra-valent cerium /3-diketonates has been examined from the point of view of the effect of additional ligands such as Ph3PO on this process, and it was found that Ce3+ /J-diketonates were stabilized by adduct formation, particularly by 1,10-phenanthroline.699... 

Treatment of 2-amino-1,4-naphthoquinone (133) and acetylacetone with Mn(OAc)3 generates an oxidatively condensed alkaloid (134) (eq. 4.46b). The same oxidative reaction of 2-amino-1,4-naphthoquinone (135) and (3-diketone with cerium(IY) ammonium nitrate (CAN) can be performed (eq. 4.47). 

Tetrakis(2,4-pentanedionato) cerium (IV) has been prepared by air oxidation of tris(2,4-pentanedionato)cerium(III) in hot benzene solution1 and by the reaction of hydrous cerium(IV) oxide with excess 2,4-pentanedione (acetylacetone) in water. The procedures presented here are based on the former approach. 

Dimeric solvated solute species [Ce2(OiPr)8(iPrOH)2] are formed when cerium isopropoxide is dissolved in its parent alcohol. These solutions are very sensitive to moisture and can be stabilized with acetylacetone. Molecular clusters are formed when a small amount of water is added. Red crystals have been... 

Cerium tetrakis(acetylacetonate), 1114 Cesium complexes crown ethers, 40 Chevrel phases, 1321 Chlorella vulgaris nitrate reductase structure, 1438 Chlorine cations... 

---