2,4-Pentanedione, transition metal chelates

Pentanedione (acacH) is a common ligand, forming chelates with almost all transition metals.1 Bis(2,4-pentanedionato)platinum(II) was first prepared by Werner,2 but the yield reported later by Grinberg and Chapurskii3 was only 35%. Furthermore, the platinum(II) chelates of other /3-diketones have not been reported. The yield of Pt(acac)2 has been increased to 75% by aquating the tetrachloroplatinate(ll) anion by treatment with mercury(II) and silver(I) ions... 

At about the same time that the potential of the lanthanide chelates for studying carbohydrates was first recognized, another group described experiments with chelates of normal transition metals, such as the 2,4-pentanedione derivatives (6) shown. As the shifts induced by these... 

In this reaction, one mole of iso-lysergic acid hydrazide is dissolved in an inert, water-miscible solvent like ethanol. Then an excess of 1-molar hydrochloric acid is added to form a salt with the iso- lysergic acid hydrazide. To this mixture is then added two moles of acetylacetone (2,4-pentanedione), which forms the desired pyrazoie. This reaction is not nearly as touchy as the formation of the hydrazide. The presence of traces of moisture from the air poses no problem. 2,4-pentanedione finds use in analytical chemistry as a chelating agent for transition metals, and as such should be available without raising too many red flags. Synthesis of this compound is not hard, and directions for doing so are found in US Patents 2,737,528 and 2,834,811. 

The beryllium chelate of 2,4-pentanedione is another example of a stable chelate it melts at 108°, boils at 270°, and is soluble in many organic solvents. By replacing the methyl groups of 2,4-pentanedione with rert-butyl groups, a diketone is obtained which, with many metals including transition and rare-earth metals, forms complexes that often are highly soluble in nonpolar organic solvents. The interior of these chelates is saltlike but the exterior is hydrocarbonlike and nonpolar, which accounts for the substantial solubility in nonpolar solvents. 

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