Acetylacetonate ligand

There were several problems to address in developing the conversion of the unsaturated acyl imidazolide 18 to these ketones. The acetylacetonate ligand was found to add to 18 leading to more than 2% of a by-product, believed to be 59 (Figure 3.7), which proved difficult to remove. The reaction also consumes far more organomagnesium reagent than should be necessary 5 equiv are required for complete conversion (the theoretical is 2.0). Also, the reaction provided best results when carried out at low temperature (-35 °C). 

Table 4.50. Comparison bond lengths R, atomic charges Qa, and NRT bond orders 6Ab o/M(acac) complexes (M = Ir, Au) and free acetylacetonate ligand (cf. Figs. 4.86(e) and 4.87(e)) C(m) denotes the central methyne carbon atom...

Nickel(ll) acetylacetonate catalyzes the addition of acetylacetone or ethyl acetoacetate to carbodiimides (Equation (89)).447 The acetylacetonate ligand of Ni(acac)2 may react with a carbodiimide to give a nickel complex having a 3-substituted acetylacetonate, which is then protonated by another acetylacetone to afford an adduct and Ni(acac)2. 

Table 4.12 Adduct Formation Constants for the Reaction EuAj(org) + i>TBP(org) EuA3(TBP)t(org), Eq. (4.26a), Where org = CHClj, and HA Substituted Acetylacetone Ligands... 

An important class of chiral, nonfluorinated lanthanide shift reagents contain acetylacetonate ligands in which the pendant methyl groups are replaced by chiral residues, e.g.. europium(III) tris[(7 ,l )-dicampholylmethanate] [Eu(dcm)3, see Table 1 and Figure 9]89. 

Acetylacetone usually forms transition metal complexes by coordination through bidentate oxygens. Since platinum forms unusually strong bonds to carbon, acetylacetonato complexes of platinum(II) are frequently C-bonded. When Pt(acac)2 is treated with 1 mole of pyridine, a bidentate oxygen-bonded acetylacetonate ligand is converted to a y-carbon-bonded ligand. 

Hydrolysis of Pd(MeCOCHMe)2 in aqueous methanol is considered to involve Pd(0,0-MeCOCHCOMe)(0-MeCOCHCOMe)(MeOH) as an intermediate from which the monodentate acetylacetonate ligand is then solvolyzed.221 Subsequent studies on Lewis base complexes of palladium bis(diketonate) complexes provide ample support for the proposed intermediate. A pulse radiolysis study of the kinetics of aquation of M(MeCOCHCOMe) " (M = Cr, Co) indicates that an 17,-172 equilibrium involving one or more of the acetylacetonate ligands occurs, associated with an acid-catalyzed removal of the monodentate ligand.222 Treatment of Cu(MeCOCHCOMe)2 with picric acid in moist dichloromethane affords a partially hydrolyzed material, Cu(MeCOCHC-0Me)(H20)2[C6H2(N02)30], proposed to contain square pyramidal five-coordinate copper with the oxygen atom from the picrate moiety at the apex.223... 

Acetyl migration occurs in the reaction of Tl(MeCOCHCOMe) with Pms Pd(PhCN)2Cl2, which yields an A-acetyl-jS-ketoimine chelate (17).471 Mossbauer data indicate that Sn(MeCOCHCOMe)2 has a trigonal pyramidal geometry with one oxygen atom from each acetylacetonate ligand in an axial position.472 The equatorial lone electron pair is both stereochemically and chemically active. Complexes in which the metal acts as the donor rather than the acceptor are formed by photolysis of Sn(MeCOCHCOMe)2 and Group VI metal hexacarbonyls in THF. The products, Sn(MeCOCHCOMe)2M(CO)5 (M = Cr, Mo, W), evidently contain tin-metal bonds. The low... 

Acetylacetonate complexes are also readily available. They are usually soluble in nonpolar solvents and are often used as autoxidation catalysts.3 74a,b It is doubtful, however, whether the acetylacetonate ligands survive these conditions since they readily undergo destructive oxidation.375 377... 

Ni(acac)2 has also proved to be an efficient metal precursor by losing the acetylacetonate ligand in the form of acetylacetone. RajanBabu has used this metal precursor to coordinate the binaphtyl-chelate-chiral ligand shown in Scheme 17 [81]. 

The synthesis of complexes containing the acetylacetonate ligand can be carried out in basic solutions. How does the base function If the base is NH3, why is the product not a complex containing NH3 ... 

Mixed complexes of lanthanides with substituted porphyrin and acetylacetone ligands were characterized by UV-Vis, IR, NMR, XPS and conductivity [55]. XPS data are given... 

Spectroscopic evidence suggests that the initial product of the thermal decomposition of cobalt(III) acetylacetonate in aqueous media is cobalt(II) acetylacetonate, and therefore (presumably) an acetylacetone ligand also. The presence of the latter has not been detected, and so it is believed that it undergoes rapid decomposition. The presence of cobalt(II) acetylacetonate has been... 

These possibilities arise because of the presence of species, such as water and surfactant, with which the primary radical can Interact. Three possibilities are Illustrated in Figure 18. In each case, the radical activity is associated in the first Instance with a species in which cobalt(III) has been reduced to cobaltCII) and the acetylacetonate ligand has rearranged to give a free radical on the methylenic carbon atom. In the first possibility, the monomer reacts directly with this species, and propagation then proceeds in the normal way. The consequence of such a mechanism would be that the polymer produced would contain both cobalt (albeit perhaps more loosely bound than in an acetylacetonate) and a moiety derived from acetylacetone. In the second possibility, the species which results from the Internal redox reaction interacts with another molecule in the reaction system (such as water) in such a way that the radical-bearing entity is displaced from the metal complex. 

VO(acac)2 reacts with A. A -diphenylformamidme (98) to give oxobis[6-(phenylammo)hexane-2,4-dionato-0,0 ]vana-dium(IV) (99) via substitution onto methyl group of the acetylacetonate ligand (Scheme 59)d ... 

VO(acac)2. - An ab initio calculation was completed to determine the equilibrium geometry of this metal complex. For this calculation and our subsequent calculations, the acetylacetonate ligand was approximated by the (acac ) ligand which shows the methyl groups replaced by hydrogens so as to decrease the time required to complete the calculations. This simplification has been found satisfactory in previous studies The predicted equilibrium structure shows the (acac ) ligands were bent away from a plane that is perpendicular to the V = Obond (Fig. 2). 

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