Copper complexes 1,3-diketones

The selectivity of the aldol addition can be rationalized in terms of a Zimmer -man-Traxler transition-state model with TS-2-50 having the lowest energy and leading to dr-values of >95 5 for 2-51 and 2-52 [18]. The chiral copper complex, responsible for the enantioselective 1,4-addition of the dialkyl zinc derivative in the first anionic transformation, seems to have no influence on the aldol addition. To facilitate the ee-determination of the domino Michael/aldol products and to show that 2-51 and 2-52 are l -epimers, the mixture of the two compounds was oxidized to the corresponding diketones 2-53. 

More advanced semiempirical molecular orbital methods have also been used in this respect in modeling, e.g., the structure of a diphosphonium extractant in the gas phase, and then the percentage extraction of zinc ion-pair complexes was correlated with the calculated energy of association of the ion pairs [29]. Semiempirical SCF calculations, used to study structure, conformational changes and hydration of hydroxyoximes as extractants of copper, appeared helpful in interpreting their interfacial activity and the rate of extraction [30]. Similar (PM3, ZINDO) methods were also used to model the structure of some commercial extractants (pyridine dicarboxylates, pyridyloctanoates, jS-diketones, hydroxyoximes), as well as the effects of their hydration and association with modifiers (alcohols, )S-diketones) on their thermodynamic and interfacial activity [31 33]. In addition, the structure of copper complexes with these extractants was calculated [32]. 

Maverick. A.W. and Klavetter, F.E. (1984) Cofadal binuclear copper complexes of a bis(P-diketone) ligand. Inorg. Chem., 23, 4129 130. 

Separation of the pnnlucts is accomplished by shaking an ethereal solution of the reaction mixture with saturated copper acetate solution. which leads to precipitation of the ether-insoluble copper complex 22. Diketone 5 is then obtained by treating this complex with ICKv sulfuric acid/... 

The acylating reagent may be an acid chloride or an acid anhydride. Symmetrical ketones (—CH2 R = R2) yield only a single regioisomer. Thus acetone or cyclohexanone may be acylated with acetic anhydride in the presence of boron trifluoride-etherate to pentane-2,4-dione and 2-acetylcyclohexanone respectively (Expt 5.102). Both diketones are present in the reaction mixture as boron difluoride complexes [(10) and (11) respectively], from which they may be released by treatment with sodium acetate. Pentane-2,4-dione is appreciably water soluble and is isolated by means of its characteristic copper complex (12). 

A large class of coordination compounds, metal chelates, is represented in relation to microwave treatment by a relatively small number of reported data, mainly p-diketonates. Thus, volatile copper) II) acetylacetonate was used for the preparation of copper thin films in Ar — H2 atmosphere at ambient temperature by microwave plasma-enhanced chemical vapor deposition (CVD) [735a]. The formed pure copper films with a resistance of 2 3 pS2 cm were deposited on Si substrates. It is noted that oxygen atoms were never detected in the deposited material since Cu — O intramolecular bonds are totally broken by microwave plasma-assisted decomposition of the copper complex. Another acetylacetonate, Zr(acac)4, was prepared from its hydrate Zr(acac)4 10H2O by microwave dehydration of the latter [726]. It is shown [704] that microwave treatment is an effective dehydration technique for various compounds and materials. Use of microwave irradiation in the synthesis of some transition metal phthalocyanines is reported in Sec. 5.1.1. Their relatives - porphyrins - were also obtained in this way [735b]. 

S-Diketones which contain aliphatic, aromatic, or heterocyclic radicals as well as a selenienyl radical have in the UV spectrum two characteristic absorption maxima (280 and 300 m/a) and high absorption intensity almost equal to that of their copper complexes. In the... 

The crystal structures of the free ligand (47a) and that of its copper(II) complex were reported.18 In both cases the terminal /3-diketone residue is present in the keto tautomeric form. The /3-ketoimine fragment of the free ligand is planar and is stabilized by an internal hydrogen bond. The crystal structure of the copper complex shows the metal coordinated in the inner N202 site.18... 

The synthesis of arsonium ylides 384 from diazocyclopentadienes 383 and tri-phenylarsine has been reexamined with respect to the efficiency of various copper-containing catalysts Whereas copper bronze gave only ca. 55 % of ylide, yields over 80% were provided by the use of Ou(II) complexes of p-diketonates derived from acetylacetone, 3-methylacetylacetone, benzoylacetone or dibenzoylmethane, as well as by bis[4-(phenylimino)-2-pentanonato-N,0-]copper(II) and Cu(II) acetate, all used in boiling benzene. The sterically more demanding complex bis(dipivaloyl-methanato)copper(II) as well as dichlorodipyridinecopper(II) proved less efficient. CopperfTI) tartrate, the dibenzo-14-crown 6/copper complex and furthermore the acetylacetonate complexes of Co, Ni, Pt and Zn were totally ineffective. When 383a was decomposed by Cu(acac)2 in the presence of pyridine or thioanisole. 

The crude H(tod) is purified first by vacuum distillation (1 torr, 60-90°) to separate the ligand from high boiling but organic-soluble impurities. Second, the copper complex is synthesized, as described below, to isolate the beta-diketone from any by-products that are formed by self-condensation of the ketone. Crude [Cu(tod)2] (20 g) is placed in a 250-mL separatory funnel with 30 mL of hexane and 150 mL of 10% (1 M) aqueous sulfuric acid. The mixture is shaken until no blue color remains in the organic phase. The organic solution is isolated and the solvent is removed by rotary evaporation. Generally, the H(tod) product is 97-99% pure. 

The Cu(tod)2 is much more soluble in hexane than almost all previously reported copper beta-diketonates.3 The logarithm of the partition coefficient of Cu(tod)2 between 1-octanol and water (log Poe,) is 3.64 0.20. This value, which is unusually large for a metal complex, is an indication of the expected bioavailability9 of [Cu(tod)2]. We have shown that a 50% (v/v) solution of H(tod) in kerosene is capable of extracting copper(II) ion from ammoniacal aqueous solutions in high yield, which may be useful for commercial recovery of copper from ore leachates.5... 

Complementary to the acylation of enolate anions is the acid-catalyzed acylation of the corresponding enols, where the regiochemistry of acylation can vary from that observed in base-catalyzed reactions. Although the reaction has been studied extensively in simple systems, it has not been widely used in the synthesis of complex molecules. The catalysts most frequently employed are boron trifluoride, aluminum chloride and some proton acids, and acid anhydrides are the most frequently used acylating agents. Reaction is thought to involve electrophilic attack on the enol of the ketone by a Lewis acid complex of the anhydride (Scheme 58). In the presence of a proton acid, the enol ester is probably the reactive nucleophile. In either case, the first formed 1,3-dicarbonyl compound is converted into its borofluoride complex, which may be decomposed to give the 3-diketone, sometimes isolated as its copper complex.164... 

In the meantime, Ohta et studied the complete series of symmetric copper complexes ((53) M = Cu R = R = C H2 +i, = 0 to 14), which confirmed the previous results. The ligand showed a crystal smectic E phase from the octyl derivative onwards as determined by miscibility studies. The first four complexes ((53) M = Cu R = R = C H2 +i, = 0 to 3) were not mesomorphic, then a mono tropic phase was detected for = 4, which became enantiotropic for > 5. Moreover, for n = l and 8, the copper complexes showed an additional mesophase, while the nonyl derivative exhibited two additional mesophases. Crystalline structures of some tetra-alkyl copper, palladium, and nickel complexes of / -diketonates revealed that the flat molecular species were stacked into columns, the planes of the molecules forming a small tilt with respect to the columnar axis-these columns were further organized into layers. Variable-temperature and NMR ... 

A number of a-substituted-j8-diketone ((200) R = R" = Me), a-substituted-j8-ketoaldehyde ((200) R = Me, R" = H), and a-substituted-yS-dialdehyde ((200) R = R" = H) complexes were investigated to evaluate their liquid crystalline properties. Whereas none of the diketone and ketoalde-hyde copper(II) complexes was mesomorphic, bis(4-alkoxyphenylmalonaldehyde)copper and oxovanadium(rV) complexes " ((200) R = R" = H R = OC H2 +i, m > 8 for M = Cu and n > 10 for M=VO) and bis(4-alkoxyphenylmalonaldehyde)copper complexes ((200) M = Cu R = R" = H R = C H2 +i, ra>5) displayed a narrow-temperature-range ( 10°Q nematic phase above 200 °C. Some nickel complexes were also prepared but extensive decomposition hampered mesophase characterization. Fliiorination and/or chlorination at the 2- or 3-position was found to lower the transition temperature substantially in the copper complexes without destroying the nematic phase, but to inhibit mesophase formation in nickel and oxovanadium complexes. 

Only one such bis(o -substituted-/ -diketone) copper complex, with an elongated core, was found to be mesomorphic, showing a nematic phase ((202) Cr 222 N 226 I ). ... 

Polymers containing yS-diketonate metal complexes of copper(ll), nickel(Il), and co-balt(III) were synthesized and examined by DSC, polarizing microscopy and X-ray diffraction. The copper complex exhibits a SmA phase while both the nickel and the cobalt complexes do not work as mesogens [72]. 

It has been shown that a j8-diketonate liquid crystal containing palladium(II) and oxo-vanadium(IV), analogous to known copper complexes (which display discotic lamellar and columnar mesophases), has been prepared and characterized palladium complexes are mesomorphic but their identification is difficult due to their decomposition in the isotropic phase the complex n = 10 seems to present a Nj phase on the basis of optical microscopy. The vanadium complexes are enantiotropic discotic [75], while the vanadium complex, 30, presented by Styring et al. [76] (n= 10), exhibited a short monotropic columnar discotic phase. 

A 10%-soln. of pentane-2,4-dione copper complex in chloroform shaken 12-24 hrs. at room temp, with a 10%-soln. of m-nitrobenzoyl chloride in the same solvent, and the crude intermediate triketone heated 10-15 min. with aq. 3 N NHg l-m-nitrophenylbutane-l,3-dione. Y 92%.—The method is simple, gives good yields of pure products, and is the most convenient one for the prepn. of certain / -diketones. F. e., also deacetylation of the triketones with ethanolic 30%-H2S04, and condensations with ethyl acetoacetate copper complex, s. W. J. Barry, Soc. 1960, 670. 

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