Rhodium complexes acetylacetone

Rhodium, tetrakis(trimethylphosphine)-reactions, 4, 926 Rhodium carboxylates, 4,903 chemotherapy, 4, 903 Rhodium complexes, 4. 901 acetylacetone synthesis, 2, 376 alkylperoxo... 

These NMR experiments provided great insight into the catalytic reaction. Whereas the catalytic reaction requires a high reachon temperature of 100 °C, aU three transformations in Scheme 3.5 proceed at 25 °C. In the same paper [16], Hayashi answered the question of why the catalytic reaction does not take place at the lower temperature. An outline of the reason is illustrated in Scheme 3.6. In the catalytic reaction, Rh(acac)(BINAP) is involved as a significant intermediate, because Rh(acac)(C2H4)2 is used as the rhodium precursor. It was confirmed that the hydroxo-rhodium complex is immediately converted into Rh(acac) (BINAP) by the reaction with 1 equiv. acetylacetone at 25 °C, in which the transmetallation from boron to rhodium is very slow at the same temperature. Thus, the acetylacetonato Hgand inhibits the catalytic reaction (Scheme 3.6, path a). 

The combination of rhodium dicarbonyl acetylacetonate complex (Rh(acac)(CO)2) and a diphosphite ligand, (2,2 -bis[(biphenyl-2,2 -dioxy)phosphinoxy]-3,3 -di-/i t/-butyl-5,5 -dimethoxy-l,T-biphenyl (BIPHEPHOS), is an excellent catalyst system for the linear-selective hydroformylation of a wide range of alkenes. This catalyst system has been successfully applied to the cyclohydrocarbonylation reactions of alkenamides and alkenylamines, which are employed as key steps for the syntheses of piperidine,indolizidine, and pyrrolizidine alkaloids. ... 

Friedel—Crafts acetylation can be achieved, but the introduction of one acetyl group deactivates the remaining chelate rings so that mixtures of mono-, di- and tri-acetyl products are formed in the case of chiomium(III) and cobalt(III) complexes, but only mono- and di-acetyl products from rhodium(III) acetylacetonate. 

Rhodium(I) acetylacetonate derivatives form allyl complexes when reacted with allene ss- ... 

Rhodium complexes with 2 or 17 [58] Acetylacetonate dicarbonyltris rhodium (I) (0.2 g) in toluene (15-50 mL) was mixed with the ligand (1 g) and stirred overnight at reflux. The solution was then added to anhydrous ethyl ether (150 mL) and the product isolated by filtration. Purification was achieved by precipitation from methylene chloride with ethyl ether. 

The NHC-rhodium carbonyl acetylacetonate complexes depicted below (R = iPr and Mes) have been investigated in the transformation with 1-hexene (C0/H2= 1 1, 60 bar 85 C, toluene, 2h) [72]. Both became active only after the addition of phosphorus ligands such as PPh3 or Alkanox 240. Detailed... 

Mixtures of homogeneous rhodium and iron catalysts were tested in the hydroformylation of 1-hexene by Trzeciak and Zidtkowski [146]. In the absence of a rhodium complex, Fe(CO)5 did not show any catalytic activity at 80 °C and 10 atm of syngas pressure. Addition of Rh(acac)(CO)2 (acac = acetylacetonate) led to the formation of 2-hexene and eventually 3-hexene, but no aldehyde was formed. Hydroformylation commenced only in the presence of Rh(acac)(CO)(PPh3). The bimetallic catalyst benefited from the presence of additional PPhg. At a ratio of P/Rh = 3, a rate acceleration of 2 times was observed, and eventually an 83% yield of aldehyde was obtained. No change in the Ub ratio was observed as a result of these modifications. 

The preparation of silicon-fiinctionalised acetylacetonate rhodium complexes of the type [Rh(L)(Ti2.C2H4)2] (L = (EtO)3Si(CH2)3C(C(0)Me)2) has been reported . These complexes were readily immobilised on silica, as shown in (8), to produce materials which were active catalysts for the synthesis of trisubstituted alkenes firom simple alkenes and diazoalkanes. The... 

In the early work on the thermolysis of metal complexes for the synthesis of metal nanoparticles, the precursor carbonyl complex of transition metals, e.g., Co2(CO)8, in organic solvent functions as a metal source of nanoparticles and thermally decomposes in the presence of various polymers to afford polymer-protected metal nanoparticles under relatively mild conditions [1-3]. Particle sizes depend on the kind of polymers, ranging from 5 to >100 nm. The particle size distribution sometimes became wide. Other cobalt, iron [4], nickel [5], rhodium, iridium, rutheniuim, osmium, palladium, and platinum nanoparticles stabilized by polymers have been prepared by similar thermolysis procedures. Besides carbonyl complexes, palladium acetate, palladium acetylacetonate, and platinum acetylac-etonate were also used as a precursor complex in organic solvents like methyl-wo-butylketone [6-9]. These results proposed facile preparative method of metal nanoparticles. However, it may be considered that the size-regulated preparation of metal nanoparticles by thermolysis procedure should be conducted under the limited condition. 

The reaction of Rh(I) derivatives such as Rh(acac)(CO)2 (acac = acetylaceton-ate) with dendrimers of generation 1,5 and 6 also proceeds readily at room temperature (Scheme 25). The complexation is unambiguously characterized in all cases by the appearance of a doublet (1JpRh=175 Hz) in the 31P-NMR spectra and corroborated by H NMR (two different CH3 groups for the acac moieties due to the decrease of symmetry of rhodium in complexes). The poor solubility of complexes of generations 5 and 6 precludes their characterization by 13C... 

Scheme 8. The synthesis of an acetylacetonate complex of rhodium from the peroxo complex.

In the above examples, the nucleophilic role of the metal complex only comes after the formation of a suitable complex as a consequence of the electron-withdrawing effect of the metal. Perhaps the most impressive series of examples of nucleophilic behaviour of complexes is demonstrated by the p-diketone metal complexes. Such complexes undergo many reactions typical of the electrophilic substitution reactions of aromatic compounds. As a result of the lability of these complexes towards acids, care is required when selecting reaction conditions. Despite this restriction, a wide variety of reactions has been shown to occur with numerous p-diketone complexes, especially of chromium(III), cobalt(III) and rhodium(III), but also in certain cases with complexes of beryllium(II), copper(II), iron(III), aluminum(III) and europium(III). Most work has been carried out by Collman and his coworkers and the results have been reviewed.4-29 A brief summary of results is relevant here and the essential reaction is shown in equation (13). It has been clearly demonstrated that reaction does not involve any dissociation, by bromination of the chromium(III) complex in the presence of radioactive acetylacetone. Furthermore, reactions of optically active... 

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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