Tetrakis 2,4-pentanedionato cerium IV

TETRAKIS (2,4-PENTANEDIONATO) CERIUM (IV) AND TETRAKIS (1,1,1-TRIFLUORO-2,4-PENTANEDIONATO) CERIUM (IV) 

Submitted by THOMAS J. PINNAVAIA and ROBERT C. FAYt Cheeked by J. P. FACKLER.t J. FETCHING and WILLIAM SEIDELf 

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. 

To a solution containing 10.8 g. (0.0249 mole) of cerium(III) nitrate 6-hydrate (Fisher Scientific Co.) in 26 ml. of 2.8 M nitric acid is added, with stirring, a second solution containing 12.7 ml. (0.124 mole) of freshly distilled 2,4-pentanedione (Matheson Coleman and Bell b.p. 136-140°C.) in 36 ml. of 

0 M ammonia. The pH of the mixture is increased to 6.0 by dropwise addition of 2.0 M ammonia the resulting yellow precipitate of hydrous tris(2,4-pentanedionato) cerium (III) is filtered, washed with three 25-ml. portions of water, and dried in air at room temperature. The precipitate is then slurried in 250 ml. of benzene in an open beaker at a temperature slightly below the boiling point. ( Hood ) 

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After a 1 -hour heating time, the dark red-brown solution of tetrakis(2,4-pentanedionato)cerium(IV) is transferred to a glass-stoppered 500-ml. Erlenmeyer flask, boiled down to a volume of 40 ml., diluted to 300 ml. with hot hexane, and finally cooled in a Dry Ice-acetone bath. The fine, needle-shaped, red-black crystals are quickly filtered and washed with two 25-ml. portions of hexane. A small amount (co. 0.35 g.) of the 6.55 g. of product is a powdery, insoluble, yellow impurity. The yield based on cerium(III) nitrate 6-hydrate is 62%.f... 

Tetrakis(l,l,l-trifluoro-2,4-pentanedionato)cerium(IV) is a dark red-brown crystalline substance which melts at 132-132.5°C. Its solubility properties are similar to those of tetrakis(2,4-pentanedionato)cerium(IV). In chloroform solution (concentration, 10 g./lOO ml. of solvent) the compound exhibits n.m.r. lines at r = 4.19 (ring protons) and r = 7.84 (methyl protons). 

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