Acetylacetone, acacH

CoCl2 was bound to the silica surface using the previous reaction and acetylacetone (AcAcH) (Scheme 7.13).241,242... 

The reaction of metal ion M"+ with the keto, enol tautomeric mixture of acetylacetone (acacH) in acidic aqueous solution has been treated by a similar approach to that outlined above (see Prob. 16). 

The reaction of Cu(II) ion with acetylacetone (acacH) to form the mono complex Cu(acac) in methanol is interpreted in terms of the scheme... 

Treatment of the complex (XXVII X = Cl) with acetylacetone (acacH) in alkali gives the mononuclear a-acetylacetonyl compound [Rh(acac)(C8Hi2)]. The stable, diamagnetic complex cyclo-octa-l,5-dicne-cyclopentadienylrhodium(I), [Rh(C6H6) (CgH )], is formed from the dimer (XXVII X = Cl) and cyclopentadienyl sodium (44, 45). The analogous complex, with cyclopentadiene as the chelating diene, has been prepared in 1-2% yield (91) by the reaction ... 

The reaction of diethylzinc with acetylacetone (acacH) in toluene resulted in the dimeric compound [EtZn(acac)]2 (39), which consists of a four-membered Zn202 ring . The El mass spectrum of 39 displayed three groups of peaks, attributed to the [Zn(acac)2] (miz 262), [EtZn(acac)] (m/z 192) and [Zn(acac)]+ (m/z 163) ions. The ion with m/z 192 simply represents a monomer fragment, whereas the ion with m/z 262 can be written as [M- EtiZn]. ... 

Complexes of acetylacetone (acacH), benzoylacetone (bzacH) and dipivaloylmethane (dpmH) have been reported. The acetylacetonate [Cr(acac)2] has been prepared from chromium(II) acetate and acetylacetone.142,143 It can also be obtained by the addition of aqueous sodium acetylacetonate to an aqueous solution of chromium(II) chloride, but in any preparation the yellow solid must be filtered off and dried as rapidly as possible, otherwise the chromium(III) compound is obtained. Its magnetic moment is 4.99 BM at room temperature consistent with a high-spin d4 configuration. 142The powerful reducing ability of [Cr(acac)2] has been used to prepare iron(II) and chromium(II) complexes80 of porphyrins and related ligands. 

Martin and Stewart1199 first described the preparation of the deep-violet complex [Co(SacSac)2] (363 R = Me) from the reaction of CoCl2 with acetylacetone (acacH) and H2S. A similar synthesis1200 where CF,acac is substituted for acac yields [Co(CF3SacSac)2] (363 R = CF3). The preparation of [Co(PhSacSac)2] via BHf reduction of the dithiolium salt (364) in the presence of CoCl2 has also been reported.1201... 

Complexation is also observed with acetylacetone (acacH=CH3-CO-CH2-CO-CH3). Its enolic form contains hydroxyl groups and reacts with metal alkoxides as a chelating ligond. Oligomers are not readily formed, and for a stoichiometric acac/Ti = 1 ratio, the nucleophilic substitution leads to monomers in which Ti is only fivefold coordinated (Fig. 5b). 

Titania and Zirconia Membranes Prepared by the Polymeric Route Titanium and zirconium propoxides can be used as precursors for the preparation of nanoporous titania and zirconia membranes. To avoid the precipitation of inhomogeneous hydroxide particles during the hydrolysis step, the alkoxide reactivity can be modified with acetylacetone (acacH). This chelating agent reacts readily with transition metal alkoxides, as follows [34] ... 

The well-known rhodium (136) and iridium 137) peroxo complexes (PhgPlaRhCKOa) (40), [(PhgPlaRhCKOalJa (41), and (Ph3P)2(C0)IrCl(02) (42) have been investigated for their reactivity with acetylacetone, acacH 138). Only the former complex, 40, exhibited any reactivity (in the presence of two equivalents of triphenylphosphine), yielding the hydroperoxo complex (43), (see Scheme 8). Complex 43 reacts with PPhg to form triphenylphosphine oxide, but does not react with any active methylene compounds (methyl acetoacetate, diethyl malonate, or acetone) save for cyclopentadiene. In the last instance, a poorly characterized, unstable system tentatively formulated as 44 may have been formed. In refluxing benzene, 43 did react with excess acacH to form the bis(acac) complex 45. 

Similarly, preparation of anhydrous and/or unsolvated lanthanide tris-acetylacetonates remained a challenge till 1965, as the efforts to remove ligated water from Ln()S-dik>3.2H2O (obtained from aqueous media) led to hydrolyzed products. However, pure tris-j6-diketonates of lanthanum, praseodymium, and neodymium could be easily synthesized by the reactions of their alkoxides (methoxides/isopropoxides) with 3 equivalents of acetylacetone (acacH) ... 

Rate laws, rate constants, and activation parameters have been established for exchange of acetylacetone (acacH) with [V(acac)3] in several organic solvents, including acetylacetone itself. The mechanism is thought to be associative, but to involve intermediates containing unidentate acetyl-acetonate. Rate constants for exchange in methanol, ethanol, chloroform, acetonitrile, and dimethyl sulfoxide cover a range of 10 rates appear to... 

The direct preparation of styrene from the oxidative arylation of ethylene constitutes a highly desirable reaction, notably from an industrial point of view. In 2000, Matsumoto and Yoshida reported a rhodium-catalyzed oxidative coupling of benzene and ethylene under ojgrgen. Rhodium(i) complexes such as Rh(acac)(CO)2, Rh(acac)(C2H4)2, [Rh(cod)Cl]2, and Wilkinson s catalyst [RhCl(PPh3)3] afforded similar catalytic activities in the presence of acetylacetone (acacH) and 0)g gen pressure, while a decreased rate was observed with Rh(iii) pre-catalysts and no reaction in the absence of acacH (Scheme 9.2). Additionally, the C-H bond activation was demonstrated to be the rate-limiting step. ... 

The )S-dicarbonyl compound (/S-dikH) generally exists as an equilibrium mixture of the tautomeric keto and enol forms. The rate of spontaneous interconversion between these forms is rather slow at room temperature, and their simultaneous NMR spectroscopic observation is possible. For instance, the NMR spectrum of neat acetylacetone (acacH) is composed of OH, CH, CHj, and CH3 signals in accordance with the following equilibrium in ppm from internal Me4Si) ... 

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