2,4-Pentanedione, complexes with

Silver fluoborate, reaction with ethyl bromide in ether, 46, 114 Silver nitrate, complexing with phenyl-acetylene, 46, 40 Silver oxide, 46, 83 Silver thiocyanate, 45, 71 Sodium amide, in alkylation of ethyl phenylacetate w ith (2-bromo-ethyl)benzene, 47, 72 in condensation of 2,4-pentanedione and 1 bromobutane to give 2,4-nonanedione, 47, 92 Sodium 2 ammobenzenesulfinate, from reduction of 2 mtrobenzenesul-finic acid, 47, 5... 

The compound 2,4-pentanedione (also known as acetylacetone and abbreviated to acac) is acidic and can be deprotonated. The anion forms complexes with metals that are used in gasoline additives, lubricants, insecticides, and fungicides, (a) Estimate the bond angles marked with arcs and lowercase letters in 2,4-pentanedione and in the acac ion. 

The tris and bis complexes of acetylacetone (2,4-pentanedione) (167) with chromium(III) have been known for many years (168,169).739 The tris compound is generally prepared by the reaction of an aqueous suspension of anhydrous chromium(III) chloride with acetylacetone, in the presence of urea.740 Recently a novel, efficient synthesis of tris(acetylacetonato)chromium-(III) from Cr03 in acetylacetone has been reported.741 The crystal structure of the tris complex has been determined.744 A large anisotropic motion was observed for one of the chelate rings, attributed to thermal motion, rather than a slight disorder in the molecular packing. 

The archetype of -diketones is acetylacetone (2,4-pentanedione Scheme 21 R = R = Me R" = H). Nickel complexes with this ligand are very numerous and are the ones studied in most detail. 

Beryllium has been determined [764] in non saline waters and in sea water at oceanic levels of 2.30pM. Two ml of 0.1M EDTA, 2ml of 1.0M sodium acetate, 1.0ml of benzene and lOOpl of l,l,l-trifluoro-2-4-pentanedione were added sequentially to 150ml samples. Following liquid-liquid extraction using detailed handling procedures, the organic phase was mixed with 1.0ml of 1.0M sodium hydroxide (de-emulsifier), washed several times with distilled water and the resultant beryllium l,l,l-trifluoro-2,4-pentanedione complex analysed by gas chromatography with electron capture detection. 

Figure 2.24 Asymmetric unit of Eu(L )3(DDXPO) thermal ellipsoids drawn with 30% probability, H atoms, and non-coordinated solvent molecules omitted for clarity [34], (Reproduced from D.B.A. Raj, S. Biju and M.L.R Reddy, 4,4,5,5,5-Pentafluoro-l-(9H-fluoren-2-yl)-l,3-pentanedione complex of Eu with 4,5-bis(diphenylphosphino)-9,9-drmethylxanthene oxide as a promising hght-conversion molecular device, Dalton Transactions, 36, 7519-7528, 2009, by permission of the Royal Society of Chemistry.)...

As Section IV will be mostly devoted to 2,4-pentanedione, acacH, it is worthwhile to dwell on this well studied species. The rate of interconversion between the keto and the enol form of acacH is rather slow at room temperature , thus they can be simultaneously detected by NMR spectroscopy it has been observed that the lower the polarity of the solvent, the higher the percentage of the enol tautomer . Electron diffraction studies indicate that in the gas phase acacH adopts the enol configuration with a keto/enol ratio of 8/92. More recently, an X-ray analysis of acacH, carried out at 110 showed that it exists as a mixture of the two enol forms 86 and 87, with the enolic hydrogen atom equally distributed over two positions close to the oxygen atoms as in 88. It should be noted that inclusion compounds containing different host molecules show different ratios of acacH in the enol form. For example, acacH exists as a dynamically averaged 1 1 mixture of 86 and 87 in an inclusion complex with l,T-binaphthyl-2,2 -dicarboxylic acid as host , while l,l-bis( >-hydroxyphenyl)cyclohexane and (4R,5R)-trawi-4,5-bis(hydroxydiphenylmethyl)-2,2-dimethyl-l,3-dioxolane include acacH in pure enolic form. ... 

A bis-/3-diketone with a disulfide bridge (10) was shown to form dinuclear derivatives with V022+ ions,91 but reacts with [Ru(acac)2(MeCN)2] yielding two products, a mononuclear complex containing the 0,S-coordinated 3-S-2,4-pentanedionate fragment, and a dinuclear complex with the bridged 0,0,S-coordinated 3-S-2,4-pentanedionate fragment.92... 

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