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NIOBIUM (V)- S C H I F F BASE COMPLEXES 11

haltigen Blei (II)-Verbindungen allein für die Photo-leitfähigkeit der Schichten verantwortlich gemacht werden kann. Es ist anzunehmen, daß die Wirkung zugesetzter Oxydationsmittel in erster Linie als inter-mediäre Oxydation des Thioharnstoffs mit anschlie-ßender Bildung von Sulfoxylat und als dessen redu-

zierender Einfluß auf die Eigenschaften der Schich-ten anzusprechen ist.

Wir danken Herrn Dr. A. STRASHEIM für die Erlaub-nis zur Veröffentlichung dieser Arbeit und Herrn Dr. G. J. RITTER für sein stets förderndes Interesse. Unser Dank gilt auch Frau K . KROOK für die wertvolle Hilfe bei der Durchführung der Experimente und Messungen.

Studies in Niobium (V) - Schi f f Base Complexes** P . PRASHAR a n d J. P . T A N D O N

Department of Chemistry, University of Rajasthan, Jaipur (India)

(Z. Naturforsch. 26 b, 11—13 [1971] ; eingegangen am 8. Oktober 1970)

A number of new niobium ( V ) - S c h i f f base complexes of the type Nb(SB)x(0Pri)5_2x and Nb(SB)2(SBH) (where SB 2 0 and SBH® are anions of the S c h i f f bases and x = l or 2) have been synthesised by the interaction of niobium pentaisopropoxide with the S c h i f f bases in different stoichiometric ratios. The molecular weight determinations and IR studies of a few derivatives have also been carried out.

Scanty references are available in the literature regarding the S c h i ff base complexes of niobium (V) and tantalum (V) 2 and such derivatives have been prepared from the corresponding metal chlorides and the S c h i f f bases. In a series of papers published earlier3' *, a more con-venient method, for the synthesis of such derivatives, by the interaction of metal alkoxides with the S c h i f f bases in anhydrous benzene medium, has been reported. The present paper describes the synthesis of several new niobium (V) derivatives with the S c h i f f bases derived from the con-densation of salicylaldehyde or o-hydroxyacetophenone with n-hydroxyalkylamines.

Experimental

Niobium pentaisopropoxide, prepared by the am-monia method5, was sublimed before use. S c h i f f bases salicylidene-2-hydroxyethylamine6, salicylidene-2-hydroxy-n-propylamine, o-hydroxyacetophenone-2-hydroxyethylimine and o-hydroxyacetophenone-2-hy-droxy-n-propylimine 7 were prepared as described ear-lier. The reactions were carried out under strictly an-hydrous conditions and found to be quite facile. The experimental technique followed in these reactions was almost the same as already reported6. The reaction mixtures, in benzene medium, were refluxed under an efficient fractionating column and isopropanol pro-duced, was removed azeotropically. The course of

Reprints request to Dr. J. P. TANDON, Reader in Chemistry, University of Rajasthan, Jaipur (Indien).

** Accepted for the presentation at the XII International Conference in Coordination Chemistry, Sydney, Australia, August, 1969.

1 A . S . KUDRAVTSEV and I. A . SAVICH, Z h . Obshch. K h i m . 33,3763 [1963].

2 Y . - Y . CHUANG, I . A . SAVICH, A . V . LAPITSKII, V . R . SAMO-ROKOV, and H. G. TITOV, Vestn. Mosk. Univ. Ser. II, Khim., 1 5 , 3 , 4 0 [I960].

reaction was ascertained by estimating the liberated alcohol in isopropanol-benzene azeotrope. The resulting new derivatives were obtained in almost theoretical yields and for brevity their analyses have been sum-marised in Table I.

Analytical Methods Niobium was determined as pentoxide and nitrogen

by the K j e l d a h l method. Isopropanol liberated in the reaction was estimated by the oxidation method 8.

The molecular weights were determined by a semi-microebulliometer (Gallenkamp) using thermistor sensing. The IR spectra were recorded with Perkin-Elmer 337 Grating Infrared Spectrophotometer using KBr optics.

3 P. PRASHAR and J. P. TANDON, Bull. Chem. Soc., Japan 43, 1244 [1970].

4 P . PRASHAR and J. P . TANDON, Z . Naturforsch. 2 5 b , 3 2 [1970].

5 D . C . BRADLEY, B . N . CHAKRAVARTY, and W . W A R D L A W , J. Chem. Soc. 1958, 2381, 4439.

6 P . PRASHAR and J. P . TANDON, J . L e s s - C o m m o n M e t a l s 13,541 [1967].

7 P . PRASHAR and J. P . TANDON, J. Indian C h e m . Soc . 4 7 , 1081 [1970].

8 D . C . BRADLEY, F . M . E . HALIM, and W . W A R D L A W , J. Chem. Soc. 1950, 3450.

12 P. PRASHAR AND J. P. TANDON

Compounds, Nature Isopropanol Analysis Mol. Remarks in the Wt .

azeotrope Metal Nitrogen [g] [ % ] [ % ]

In 1 : 1 molar ratio Nb(0Pri)3(C9H9N02) (a) 0.74 Pale yellow semisolid. (b) 0.78 Nb(OPri)3(CioHnN02) (a) 0.42 Pale yellow semisolid. (b) 0.44 Nb(OPri)3(CioHuN02*) (a) 0.43 Pale yellow and viscous. (b) 0.44 Nb(0Pri)3(CnHi3N02) (a) 0.44 Pale yellow and sticky (b) 0.46 2 molar ratio Nb(0Pri)(C9H9N02)2 (a) 0.90 Yellow and foamy (b) 0.92 Nb(OPri)(CioHiiN02)2 (a) 0.98 Yellow and foamy (b) 0.99

Nb(OPri)(CioHnN02*)2 (a) 0.70 Yellow and foamy (b) 0.73 Nb(0Pri)(CiiHi3N02)2 (a) 0.69 Yellow and foamy (b) 0.71

3 molar ratio Nb(C9H9N02)2(C9HioN02) (a) 0.88 Yellow and foamy (b) 0.89 Nb(CioH11N02)2(CioHi2N02) (a) 0.88 Yellow and foamy (b) 0.90 Nb(CioHnN02*)2(CioHi2N02*) (a) 1.36 Yellow and foamy (b) 1,42 Nb(Ci1H 1 3N02)2(CiiH 1 4N02) (a) 0.97 Yellow and foamy (b) 0.98

21.41 3.20 477 Decomposed on heating 21.43 3.23 433 under reduced pressure. 21.04 3.09 593 Did not melt up to 20.77 3.13 447 200 °C. 20.88 3.00 617 20.77 3.13 447 20.38 2.99 536 Melted at 1 4 8 - 1 5 0 °C 20.14 3.03 461 into a clear mass.

19.22 5.80 766 19.42 5.86 478 18.05 5.39 759 Softened at about 64 °C 18.34 5.53 506 and melted into a yellow

liquid at 1 1 0 - 1 1 1 °C. 19.02 5.35 735 18.34 5.53 506 17.02 5.20 636 Melted at 7 4 - 7 7 °C and 17.39 5.24 534 then the colour darkened.

15.75 7.15 582 Melted into a viscous 15.92 7.20 583 mass at about 60 °C. 14.82 6.60 617 Changed into a viscous

14.85 6.71 625 mass at about 62 °C. 14.57 6.62 647 Turned into a viscous 14.85 6.71 625 mass at about 59 °C. 13.85 6.12 655 Changed into a viscous 13.91 6.27 667 mass at about 69 °C.

Table I. Reactions of Niobium isopropoxide with S c h i f f bases, (a) = analysis of the compound, (b) = calculated for the formula, * = anion of the S c h i f f base, o-hydroxy acetophenone 2-hydroxyethylimine.

Results and Discussions

The reactions of niobium isopropoxide with the S c h i f f bases in 1 : 1, 1 : 2 and 1 : 3 molar ratios liberated 2,4 and 5 moles of isopropanol respecti-vely and resulted in the synthesis of the cor-responding mono-, bis- and tris-S c h i f f base deri-vatives of niobium (V). They were isolated in the form of a pale yellow solid or foamy mass, and found to be soluble in benzene and isopropanol. A few complexes could also be recrystallized from these solvents.

The monoisopropoxy-bis - S c h i f f base and the triisopropoxy-mono - S c h i f f base niobium (V) compounds appear to be similar to the correspond-ing tantalum (V) 3' 4 and niobium (V) 4 or the di-alkoxy titanium (IV) 6>7 derivatives as far as their hydrolytic tendency is concerned. All these com-pounds are non-volatile and resemble the tantalum (V) derivatives. Analogous to the triisopropoxy-tan-talum-salicylidene-2-hydroxyethylamine3, the cor-responding niobium (V) derivatives decomposed,

when an attempt was made to distil them under reduced pressure.

The molecular weight determinations indicate that mono - S c h i f f base 1 and tris - S c h i f f base 2 derivatives are monomeric and probably contain the central metal atom in the hexa- and octa-coordi-nated states respectively and can be tentatively re-presented by the structures 1 and 2. The molecular complexity of the bis - S c h i f f base derivatives ranges between 1.2 to 1.6, which probably indicates an equilibrium between structures 3 and 4.

N—Nb--OPr1 -OPr' -OPr'

Pr1 0 I N-̂ Nb—W

cr 3

n° ^ 0H

>N—»-Mb-—N V - 2 V

0 0 0

/-N XZHNb NbZ l / l V I v

Pr'Oj/ 4

In the above structures, the ligands have been represented by the HO — N — OH system.

HALBWERTZEIT VON RADIOCHEMISCH REINEM 59Fe 13

The IR spectra of the S c h i f f bases as well as their metal complexes are very much similar and quite complicated. However, the following points appear to be significant:

1. The disappearence of broad and medium to strong bands of ligands in the region 3100 — 3350 cm - 1 , which can be ascribed to the stretching modes of hydrogen bonded OH or NH, probably indicates chelation through 0 as well as N atoms of ligands.

2. The band of the stretching frequencies of — C = N — appears in the almost same region in the S c h i f f bases as well as metal complexes.

3. The absorption band for the free hydroxyl

group is not observed in niobium (V) -tris - S c h i f f base derivatives.

4. In the IR spectra of metal complexes the ap-pearence of the new bands or increase in the inten-sity of the absorption bands already present in the ligand in 520 — 590 c m - 1 region may be attributed to the Nb — 0 stretching vibrations.

The authors wish to thank Dr. R. C. MEHROTRA, Professor and Head of the Chemistry Department, Uni-versity of Rajasthan, Jaipur, for providing research facilities. Thanks are also due to Dr. V. K. MATHUR for the infra-red spectra and C.S.I.R., New Delhi, for the award of a Research Fellowship (JRF) to one of them (PP).

Physikalische und biologische Halbwertzeit von radiochemisch reinem 59Fe

Physical and Biological Half-Life of Radiochemically Pure 59Fe H . C . HEINRICH, E . E . GABBE u n d D . H . W H A N G

Abteilung Medizinische Biochemie, Institut für Physiologische Chemie der Universität Hamburg

(Z. Naturforsch. 26 b, 13—20 [1971] ; eingegangen am 14. Oktober 1970)

At delivery commercial 59Fe-preparations contain up to 1% contamination by 60Co, 65Zn, 54Mn, 46Sc, 134Cs, etc., so that the physical half-life of such preparations is not constant and starts to increase permanently after about 100 days. Anion exchange chromatography was used to prepare 59Fe with a radiochemical purity of 99.9999993? as demonstrated by analytical anion exchange chromatography, paper- and thin-layer chromatography, and /-spectroscopy. The physical half-life of radiochemically pure 59Fe was found to be constant over 500 days with 44.52 ±0 .016 days (A= 0.015568 ±0.0000056 [ d " 1 ] ) .

The whole-body retention of radiochemically pure 59Fe was measured in man over one year with a 4 Ti-geometry whole-body radioactivity detector and utilized for the estimation of the ef-fective half-life of 59Fe. The correct physical half-life of radiochemically pure 59Fe was used for the calculation of the biological half-life. Normal male subjects showed an effective half-life of 43.6 ± 0.34 days and a biological half-life of 2136 ± 807 days. This means a whole-body-59Fe-turn-over rate of 0.032 ± 0.012%/d equivalent to 1.25 ± 0.46 mg Fe/d (for a whole-body iron pool of 3850 mg in a 70 kg man). Menstruating females were observed to have effective half-lives of 43.1 ± 0.22 days and therefore biological half-lives of 1389 ± 224 days. Their whole-body-59Fe-turnover rate is higher (than in males) with 0.050 ±0.008%/d. For an optimal whole-body iron pool of 3300 mg (in 60 kg female) this would mean an iron loss of 1.65 ± 0.26 mg/d. Non-menstruating females were quite similar to males. They showed effective and biological 59Fe-half-lives of 43.5 ± 0.48 and 1833 ± 857 days, respectively. Their whole-body-59Fe-turnover rate was calculated to be 0.038 ±0.018%/d or 1.25 ± 0.59 mg Fe/d (60 kg female with 3300 mg Fe-pool). These experimen-tal data are the first direct and reliable proof for the magnitude of daily iron loss and iron re-quirements in man.

Die Ergebnisse aller bisher aus Gesamtkörper-Retentionsmessungen des 59Fe berechneten biologi-schen Halbwertzeiten waren durch besonders kurze Werte und die sich daraus ergebenden Mittelwerte der Gesamtkörper-59Fe-Umsatzraten entsprechend

Sonderdruckanforderungen an Prof. Dr. med. H. C. HEIN-RICH, Abteilungsvorstehen u. Prof. d. Univ. Hamberg, Phy-siolog.-Chem. Institut d. Univ., D-2000 Hamburg 20, Mar-tinistr. 52.

durch zu hohe Werte von z.B. 0,14 — 0,31% des Gesamtkörper-Fe-Pools/Tag charakterisiert (Uber-sich und Literatur bei HEINRICH1). Für den Gleich-gewichtszustand zwischen einem Gesamtkörper-Fe-Pool von 3850 mg (beim 70-kg-Standard-Mann)

1 H. C. HEINRICH, Review in Intern. Geigy Therapy Sympo-sion on Iron Deficiency, March 25-29, 1969, Arosa/Switzer-land; in: „Iron Deficiency" (Edit. L. HALLBERG, H. G. HARWERTH and A . V A N N O T T I ) , S. 2 1 3 , A c a d e m i c Press, London 1970.