Tropolones metal complexes

Tris(l, 10-phenanthroline) complexes structure, 63 Tropolone metal complexes electrophilic substitution, 422 Tungstate, pcntachlorothio-stereochemistry, 50 Tungsten, octacyano-photoreactivity, 406 structure, 84... 

Dyrssen, D., Studies on the extraction of metal complexes. XVIII. The dissociation constant and partition coefficient of tropolone, Acta Chem. Scand. 8, 1394—1397 (1954). 

The tropolones form transition-metal complexes of high affinity constants, for example [M(77 )3] with M = Co(n), Ni(H) and Zn(H), but M(77 )2 with M = Cu(II)2 . Moreover, these compounds form complexes with heavy metals (Os, Ir, Pt, Mo and W) , the lanthanides(in) and main-group metal ions (Ga, In, Sn, Sb and Pb) many have crystal structures determined and some show biological activities and potential... 

That tropolone is such an effective chelating agent contributes to its wide application in chemistry. The tropolonate ion forms a five-membered chelating ring of which the bite , that is, the oxygen-to-oxygen distance, is smaller than that in the S-diketonate, i.e. acetylacetonate. The bite is also well illustrated by the bite angle, O-M-0, in metal complexes. 

Alkylation and acylation reactions which are promoted by metal catalysts, such as the Friedel-Crafts reaction, do not take place because tropolones form complexes with the metal salts which,- like tropolonium salts, are resistant to further attack. 

General methods for the preparation of niobium(v) and tantalum(v) complexes have been discussed and better synthetic routes to some known compounds have been described. [Nb(bpha) Cl], [Ta(bpha) Cl], and [NbO(t)3] (where bpha and t are the anions of benzoylphenylhydroxylamine and tropolone, respectively) have been prepared for the first time. NbClj or TaClj in methanol react with Hbpha to form the [M(bpha)4Cl] complexes. An aqueous solution of niobiumfv) which contains tartaric acid to prevent condensation of the hydrolysed metal species affords [NbO(t)3] with tropolone." " ... 

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). 

Dynamics of Intramolecular Metal-Centered Rearrangement Reactions of Tris-Chelate Complexes B. Tris(tropolonates)... 

The a-substituted tropolonates 2 which are tris chelate complexes with a M06 coordination core have received considerable study by DNMR.27, 4S 46) The complexes are of the M(A-B)3 and M(A-B )3 types and therefore the averaging sets of Eaton efa/.26, 27 in Table 1 are applicable. The metal ions and a-R-substituents used in these studies include M = Al(III), Ga(III), Co(III), V(III), Mn(III), Ru(III), Rh(III) and Ge(IV) R = isopropyl (C3H7) and isopropenyl (C3HS), however, only complexes of Al(III), Ga(III), and Co(III) have yielded definitive mechanistic information.27, 45 46> On the basis of line shape changes of the methyl resonances these complexes can be classed kinetically as follows stereochemically nonrigid complexes which attain the fast-exchange limit of inversion and/or isomerization... 

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