Lanthanum nitrate complexes

Sometimes, small differences in stoichiometry that would not readily be detected by analysis are revealed by crystallography. For example, crystals of two lanthanum nitrate complexes of the terdentate 4-amino-bis(2,6-(2-pyridyl))-l,3,5-triazine, 10- and 11-coordinate [La(abptz)(N03)3(H20) ] (n = 1, 2), can be isolated from the same reaction mixture, evidently because of similar solubilities. This subtle difference in stoichiometry leads to significant differences in the molecular geometry. Thus, the increase in coordination number of the lanthanum from 10 to 11 is accompanied by a sharp increase in La-0... 

The most popular device for fluoride analysis is the ion-selective electrode (see Electro analytical techniques). Analysis usiag the electrode is rapid and this is especially useful for dilute solutions and water analysis. Because the electrode responds only to free fluoride ion, care must be taken to convert complexed fluoride ions to free fluoride to obtain the total fluoride value (8). The fluoride electrode also can be used as an end poiat detector ia titration of fluoride usiag lanthanum nitrate [10099-59-9]. Often volumetric analysis by titration with thorium nitrate [13823-29-5] or lanthanum nitrate is the method of choice. The fluoride is preferably steam distilled from perchloric or sulfuric acid to prevent iaterference (9,10). Fusion with a sodium carbonate—sodium hydroxide mixture or sodium maybe required if the samples are covalent or iasoluble. 

The apparent failure of trivalent and tetravalent cations to enter plants could result from the interaction of the cations with the phospholipids of the cell membranes. Evidence for such interactions is provided by the use of lanthanum nitrate as a stain for cell membranes (143) while thorium (IV) has been shown to form stable complexes with phospholipid micelles (144). However, it is possible that some plant species may possess ionophores specific to trivalent cations. Thomas (145) has shown that trees such as mockernut hickory can accumulate lanthanides. The proof of the existence of such ionophores in these trees may facilitate the development of safeguards to ensure that the actinides are not readily transported from soil to plants. 

There has been recent interest in lanthanide complexes of ligands of the type (21). These are in some sense nitrogen analogues of the crown ethers. As Schiff bases, their lanthanide complexes may be synthesized by a template condensation, for example from 2,6-diacetylpyridine, 1,2-diaminoethane and lanthanum nitrate. These components react in alcohols to give [La(N03)3L], where the aza-crown L = (21 R = Me). This compound has a structure (Figure 6), quite analogous to that of [La(N03)3(18-crown-6)], in which La—N... 

Ciampolini, M., Dapporto, P., and Nardi, N. (1979) Structure and properties of some lanthanoid(III) perchlorates with the cryptand 4,7,13,16,21,24-hexaoxa-l,10-diazabicyclo[8.8.8]hexacosane, Dalton Trans, 974-977 Hart, F. A., Hursthouse, M. B., Abdul Malik, K. M., and Moorhouse, S. (1978) X-ray crystal structure of a cryptate complex of lanthanum nitrate, Chem. Commun. 549-50. 

A number of other complexes involve the lanthanide bonding to nitrogens in rings, either in aza crowns or in more classic macrocycles like cyclen. 1,4,7,10,13-pentaazacyclopentadecane (L) forms nitrate complexes [Ln(L)(N03)3] (Ln = Y, La Yb except Ce, Pm, Ho) the structure of [La(L)(N03)3] shows it to have 11-coordinate lanthanum As another example of structurally characterised... 

A NMR study of lanthanum nitrate solutions in MeCN led to the identification of a number of complexes including [La(N03)3(MeCN)4] and [La(N03)3(MeCN)3(H20)], but they were not isolated.A few complexes such as [Eu(MeCN) c(BF4)3] ( " 3) have previously been prepared, in this case by oxidation of metallic Eu by NOBF4, but have lacked structural characterization. " ... 

In the presence of 15-crown-5, reaction of lanthanum nitrate with bipy in MeOH-MeCN led to [La(bipy)(N03)3(H20)2(Me0H)] 15-crown-5, which has 11-coordinate lanthanum. The increase in coordination number in comparison with [La(bipy)2(N03)3] results in an slight (and possibly not statistically significant) increase in La—N distance from 2.66 A to 2.70 A, and in La—O from 2.56-2.63 A to 2.69 A. The presence of the coordinated MeOH molecule supplies a fifth hydrogen atom so that hydrogen bonds can be formed to all the crown ether oxygens. In another synthesis in the presence of a crown ether, a 10-coordinate complex, [La(bipy) (N03)3(H20)2] benzo-15-crown-5, is obtained. ... 

If lanthanum nitrate and ammonia are added to the test solution without iodine being present, a white precipitate of basic lanthanum nitrate develops. The precipitation initiates slowly at room temperature but is speeded up by heating. This precipitate will, in the presence of acetate ions, form a complex with iodine that can have the form of a blue solution or a blue precipitate. 

The La-M heterobinuclear complexes noted LaxM(fsa)2en,N03.H20 were synthesized according to the methods previously described using nickel or copper acetates (Aldrich, 98%), lanthanum nitrate (Janssen, 98%) and N,N -Bis(3-carboxysalicydene)ethylene diamine (noted (fsa)2en) as a ligand ([5], [6], [7]). M (Ni2+ or Cu " ") was introduced at first in sodium carbonate medium, whereas La was complexed in a second step in Li0H/CH30H medium. 

Phosphorus has been determined [23, 24] in thermally stable polymers by mineralisation with a nitric - perchloric acid mixture and subsequent titration with lanthanum nitrate or by photometric determination of the phosphomolybdic blue complex. 

A spectrophotometric method was worked out by Wang and coworkers [53] for the determination of trace level fluoride concentration of water samples. In this procedure, the samples are mixed with a reagent mixture (alizarin-3-methylimino-N,N-diacetic acid/ sodium acetate/12.5% acetic acid buffer of pH 4.1/1 mM lanthanum nitrate (1 1 1 )). After a reaction time the colored complex is extracted with 5% N,N-dimethylaniline solution in 3-methylbutan-l-ol and the absorbance is detected in a special, long capillary at 580 nm. 

The complex formations and reaction stoichiometry of the equilibrium extraction of lanthanum nitrate by purified-water equilibrated HDEHP was reported by Kosinski and Bostian (1969). The transfer of water molecules from the lanthanum-enriehed organic phase to the aqueous phase was verified, indicating that it should be ineluded in the extraction mechanism. The three predominant extraction mechanisms involving pure lanthanum ions and partially nitrated lanthanum ions are... 

Aqueous DMF solutions of lanthanum nitrate, chloride, and perchlorate have been investigated by La-NMR spectroscopy as a fimction of the mole fraction Xj of the organic solvent (Tarasov et al. 1986). Both the perchlorate and chloride anions remain in the outer coordination sphere and the cation is preferentially solvated by DMF molecules. In the range 0.14 < Xs < 1, nitrate ions are located both in the outer and inner coordination sphere, forming [La(DMF)j (N03) ] complexes. In solutions with a high content of DMF (1 >Xs > 0.7) the composition of the coordination sphere of La is constant and the predominant complex is [La(DMF)5(N03)2]. ... 

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