Acetylacetone dimer

For the synthesis of aminotriacetylpyrans 84 a reaction of 3-bromoace-tylacetone 85 with cyanoacetic ester in ethanolic NaOH was employed. Possibly, it proceeds via the formation of acetylacetone dimer 86... 

Palladium(II) acetate was found to be a good catalyst for such cyclopropanations with ethyl diazoacetate (Scheme 19) by analogy with the same transformation using diazomethane (see Sect. 2.1). The best yields were obtained with monosubstituted alkenes such as acrylic esters and methyl vinyl ketone (64-85 %), whereas they dropped to 10-30% for a,p-unsaturated carbonyl compounds bearing alkyl groups in a- or p-position such as ethyl crotonate, isophorone and methyl methacrylate 141). In none of these reactions was formation of carbene dimers observed. 7>ms-benzalaceto-phenone was cyclopropanated stereospecifically in about 50% yield PdCl2 and palladium(II) acetylacetonate were less efficient catalysts 34 >. Diazoketones may be used instead of diazoesters, as the cyclopropanation of acrylonitrile by diazoacenaph-thenone/Pd(OAc)2 (75 % yield) shows142). 

Acetylacetone was deprotonated with diethylzinc in toluene to afford [EtZn(acac)]2 (Figure 65, 140) which crystallized in dimeric form. The quality of the X-ray data was too low to obtain reliable bond parameters, but the coordination environment about zinc is distorted tetrahedral, with two intramolecular and one intermolecular Zn-O bond.200... 

An obvious method to investigate the formation and the nature of the catalytically active nickel species is to study the nature of products formed in the reaction of complexes such as 3 or 4 with substrate olefins. This has been investigated in some detail in the case of the catalytic dimerization of cyclooctene to 1-cyclooctylcyclooctene (17) and dicy-clooctylidene (18) [Eq. (4)] using as catalyst 7r-allylnickel acetylacetonate (11) or 7r-allylnickel bromide (1) activated by ethylaluminum sesquihalide or aluminum bromide (4). In a typical experiment, 11 in chlorobenzene was activated with excess ethylaluminum sesquichloride cyclooctene was then added at 0°C and the catalytic reaction followed by removing... 

Reactions leading to the formation of the catalytically active nickel hydride species from organonickel precursors (Section III) can be regarded as model reactions for olefin oligomerization reactions. The reactions described by Eq. (8) and Scheme 3 (Section III) show that RNiX compounds (R = methyl orallyl, X = halide or acetylacetonate) activated by Lewis acids add to double bonds under mild reaction conditions (-40° or 0°C). It follows further from these reactions that under conditions leading to olefin dimerization a rapid nickel hydride /3-hydrogen elimination reaction occurs. The fact that products resulting from olefin insertion into the nickel-carbon bond are only observed when /3-hydride... 

Ti(OPr )4 reacts with the Schiff bases acetylacetone, 2-hydroxylalkyIimines, and N-[(3-hydroxy-2-naphthyl)methylene]-2-hydroxylalkylimines (H L) in a 1 1 or 1 2 molar ratio to give [TiL(OPr )2] and [TiLj], respectively. Similarly, TKOR) (R = Et or Bu ) react with Af-salicylidene-2-hydroxyethyl-amine (H2L ) to form [TiL (OR)2] or [TiLa]. Treatment of [TiLHOEt)2] with MeOH gives [TiL OMelj] and both these alkoxides appear to have the dimeric structure (16), whereas [TiL (OBu )] and TiLj are monomeric. ... 

Mn(acac)3 reacts with ethylenediamine (L2) or other primary amines (L) to yield [Mn"(acac)2L2], which can also be prepared by the reaction of the amine or diamine with [Mn(acac)2(H20)2]. Allylamine reacts with [Mn(acac)2-(H20)2] in ether to give a second complex, [Mn(acac)2(H2NCH2==CH2)]2 which is dimeric both in the solid and vapour phases. This is the First example of a dinuclear manganese(ii) acetylacetonate complex. Thermodynamic data have been reported for the manganese(ii)-acetylacetone system in propan-1-ol-water. ... 

Both monomers and polymers have been reported in the mass spectra of metal acetylacetonates (105, 106), depending on the nature of the metal, and its oxidation state different laboratories have reported conflicting results. Undergraduates in our freshman laboratory (107) recently discovered Cr2(acac)5 ions in the spectrum of Cr(acac)j but found that this dimer was removed if the sample was carefully purified, thus casting doubt on the purity of some of the previously reported (acac) derivatives showing dimers. 

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]. ... 

There is a dimethylgallium acetylacetonate Me2Ga(acac), m.p. 22 °C, and a dimethylgallium tropolonate, the structure of which proves to be dimeric with Ga—O bonds of 197.4 and 202.5 pm to the chelation ligand and distances of 246.3 pm within the central Ga202 ring of the dimer.548... 

Several polydentate SBs may act as binucleating ligands see Section 33.5.12.1. Only a few miscellaneous polydentate SBs will be included here. A complex with the SB obtained in the reaction of two moles of benzoyl hydrazide with acetylacetone had v(V=0) = 995 cm 1, Pea =1.7BM and was monomeric square pyramidal (117).792 A few complexes with the ethylenediamine derivatives of 2,2 -dihydroxychalcones (118) were prepared in ethanol.793 The stoichiometry is 1 1 and the atoms involved in the coordination were two deprotonated oxygens and two nitrogen atoms. v(V—O) (970-985 cm-1) and f4 (1.73-1.83 BM) suggest a monomer however, molecular weights in nitrobenzene suggest a dimer. 

Iridium complexes having oxygen ligands are not nearly as extensive as those having nitrogen. Examples include acetylacetonates [Ir(P(C(5H5)3)2 (acac)H2] [64625-61-2], aqua complexes Ir(OH2)6]3+ [61003-29-0], nitrato complexes [Ir(0N02)(NH3),J2 [42482 42-8], and peroxides IrCl(P(C6I fy)3)2(02-/-(>/ I I9)2(CO) [81624-11-5]. Unlike rhodium, very few Ir(II) carboxylate-bridged dimers have been claimed and [Ir,2(OOCCI I3)4 has not been reported. Some Ir(T) complexes exhibit reversible oxidative addition of 02 to form Ir(III) complexes. That chemistry has been reviewed (172). 

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