8-hydroxyquinoline 3-diketonates

The five-coordinate complexes Ir(CO)(PPh3)2L, where HL = /3-diketone, A-benzoyl-A-phenyl-hydroxylamine, salicylaldehyde, 8-hydroxyquinoline, 2-hydroxybenzophenone, 2-hydroxy-8-methoxybenzophenone, were prepared from [Ir(CO)(PPh3)2Cl].632 The resulting compounds all underwent oxidative addition reactions with Br2. Reaction of [(cod)2IrCl]2 with N-substituted 3-hydroxy-2-methyl-4-pyridine gives the bichelated complex (389). 33... 

Numerous other complexes of beryllium with organic ligands such as alloxides (276-280), /6-diketonates (90, 281-297), SchifF bases (64, 298-301), thiols (302), pyridines (303), bipyridyl (304), phthalocya-nine (305), hydroxyquinolines (306, 307), tropolones (308, 309), pyra-zolylborates, (94, 310), phosphinates (311), hydrazides (312), phenyl-hydrazonocarboxylates (313), dinaphthofuchsonedicarboxylates (314),... 

When a metal atom donates electron density to a bound ligand, usually by means of Ji-back bonding, electrophilic substitution reactions may be promoted. This is observed then usually with metals in low oxidation states and is therefore prevalent with organometallic complexes - and less with those of the Werner-type, where the metals are usually in higher oxidation states. Nevertheless there have been detailed studies of electrophilic substitution in metal complexes of P-diketones, 8-hydroxyquinolines and porphyrins. Usually the detailed course of the reaction is unaffected. It is often slower in the metal complexes than in the free ligand but more rapid than in the protonated form. 

Chelating extractants such as beta-diketones, tropolones, hydroxyoximes, and 8-hydroxyquinolines (Figure 2.1), have been used extensively for the extraction of actinide ions from moderate to weakly acidic solutions (15-17). Beta-diketones such as acetylacetone (acac), HTTA, benzoyl trifluoroacetone (BTFA), and dibenzoyl-methane (HDBM) have been commonly used for the separation of actinide ions. The extraction mechanism involved formation of the enol form of the beta-diketone prior to complexation and extraction of the metal ion (Figure 2.2). 

Acetonitrile and benzonitrile, aliphatic amines, pyridine, amides (especially DMF), alcohols, and propylene-carbonate are used as solvents in the syntheses of this type. All of them have properties of ligands. Moreover, such classic N-donors as 2,2 -bipy and 1,10-phen were used as ligands, as well as compounds with P-(triphenylphosphine) and O- donor centers (urea, pyridine-N-oxide, triphenyl-phosphinoxide) and chelating ligand systems ((3-diketones, 8-hydroxyquinoline, dimethylglioxime) [202]. 

The systems of interest here entail either 8-hydroxyquinolinate, /3-diketonate, or porphyrin complexes. Upon excitation at 351 nm, tris(8-hydroxyquinolate) [Er(8-Q)3] shows a broad emission band at room temperature in the range 380-750 nm, with a maximum at 600 nm, which is red-shifted by about 80 nm with respect to group III (e.g. Alm) quinolinates. In addition, a bright 1.54-nm emission is seen upon excitation with an argon laser at 457 nm the intensity of which varies linearly with the excitation power in the range 1-100 mW (Gillin... 

The intra-complex PCMU are those compounds in which at least one fragment is linked with the metal ion via both a valent and coordination bond. It should be noted that such compounds can be neutral, cationic, anionic or contain, in addition to chelating ligands, monofunctional varieties. The number of such PCMU is enormous therefore we shall indicate the most frequent types. A detailed consideration has been given earlier to complexes of metals with polymers containing diketone [13], o-hydroxyazomethine [14], enaminoketone [15], amino add [16], 8-hydroxyquinoline [17] and other groups. 

Scheme 1 represents the synthesis of a linear coordination polymer by use of bischeiating ligands such as rubeanic acid, bis-1,3-diketones, and bis-8-hydroxyquinolines which can be attached simultaneously to metal atoms or ions. Equation 6 describes a recent example of the coordination polymers which is prepared according to Scheme 113). This field of coordination polymers was developed from the large research program in USA during the Second World War in attempts to find thermally stable polymers. The activity in this field has been recently increased in the expecta-...

The formation of quinolines and benzoquinolines by the condensation of primary aryl amines with P-diketones followed by an acid catalyzed ring closure of the Schiff base intermediate is known as the Combes quinoline synthesis. The closely related reaction of primary aryl amines with p-ketoesters followed by the cyclization of the Schiff base intermediate is called the Conrad-Limpach reaction and it gives 4-hydroxyquinolines as products. ... 

Primary deuterium isotope effects have also been measured in 8-hydroxyquinoline N-oxides (32) . It was found that a plot of A( H, H) vs. 50H had a different slope than observed for tautomeric hydroxyquinones and /3-diketones . 

The elements which are co-precipitated as hydroxides can also be separated by organic reagents of the R-OH type, such as 8-hydroxyquinoline, cupferron, or 6-diketones. Metal ions giving sparingly soluble sulphides may be co-precipitated by organic reagents of the R-SH type, e.g., dithiocarbamates. 

Rare-earth elements can be separated from other metals by extraction methods using the complexes with TOPO (MIBK) [19], HTTA with TOPO (toluene) [20,21], HDEHP [22-24], DDTC [25], 8-hydroxyquinoline with phen [26] or with tetra-n-heptylammonium ion (CHCI3) [27], high molecular-weight amine [28], EDTA in the presence of Capriquat [29], a-diketones [30], and 2-thenoyltrifluoroacetone [31-34]. 

Reactions of THE complex (5a) with j -diketones <81IZV394> and with 8-hydroxyquinoline <86izvi645> also proceed in mild conditions affording the corresponding chelates (91) and (92) in good yields (Scheme 34). 

Chelating extractants may be used for ionic salts. Examples include beta diketones such as thenoyltrifiuoroacetone (TTA), acetylacetone, benzoylacetone, and dibenzoylmethane 8-hydroxyquinoline (oxine) oximes such as dimethyl-glyoxime nitrosophenyl compounds and nitrosohydroxylamines such as N-nitrosophenyl hydroxylamine (cupferron) and diphenylthiocarbazone (dithizone). 

Quantum yields for Er are much smaller and no data are reported for -diketonates. Among the few other quantitative figures reported, we note a quantum yield of 0.02% in deuterated water with fluorescein as the antenna chromophore, while all the other quantum yields are far below 10 %. As for neodymium, 1,10-phenanthroline and 8-hydroxyquinolinate are among the best sensitizers. 

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