Scandium acetylacetonate [(CH₃.CO)₂CH]3Sc

Scandium acetylacetonate [(CH₃.CO)₂CH]3Sc, is obtained by adding scandium chloride solution to acetyl-acetone dissolved in a slight excess of ammonia. It may be purified by crystallisation from 70 per cent, alcohol, or by dissolving it in benzene and precipitating with light petroleum. By the former method it crystallises in colourless sparkling prisms; by the latter, in needles. It is soluble in ether and chloroform, and melts at 188° C.; it crystallises in the rhombic system and is isomorphous with the indium salt. Molecular weight determinations have been made by the freezing-point method in benzene, and by the boiling-point method in benzene, chloroform and carbon disulphide, and the results show clearly that the molecular formula is that given above, and not [(CH₃.CO)₂CH]2Sc or [(CH₃.CO)₂CH]4Sc₂, with Sc = 29.

Under a pressure of 8 to 10 mm., scandium acetylacetonate begins to sublime at 157°, and sublimes rapidly at 187° without decomposition. At atmospheric pressure it melts at 188°, and commences to volatilise appreciably at 190°; no decomposition occurs below 250°. The acetylacetonate does not combine with ammonia. In its properties it therefore resembles thorium acetylacetonate closely, and differs appreciably from the acetylacetonates of the rare earth elements.