Chelidonic acid compounds of lanthanide ions

Notes

1503 0022-1901~0/1001-1503/$02.0010

]. iaovg n~L Cke¢ Vol. 42, pp. 1.503-1504 © Pergamon Press Ltd., 1980. Printed in Great Britain

C h e l i d o n k acid compounds of lanthanide ions

(First received 29 November 1979; received for publication 8 February 1980) The present note deals with the synthesis and characterization of lanthanide salts of chelidonic acid (LH2) with the basic carbonates.

0 HOOC~COOH

LH 2

It is well known that lauthanide complexes of pyridine-2, 6-dicarboxylate[1] and of carboxylates in general[2] can be prepared as crystals large enough to have their structures determined by X-ray diffraction analysis. Because of the chemical analogies it was anticipated that the ligand LH2 would likewise from lanthanide complexes susceptible to X-ray structure determination. This anticipation was not fulfilled; the lanthanide salts of LH2 being obtained only as powders. However, their emission spectra are remarkable, showing a very intense luminescence with characteristic sharp lines and allowing the symmetry of the chemical environment to be assigned. ~NTAL

Materials. The rare earth oxides were 99.99% purity and were generously supplied by Molycorp. The chelidoulc acid (Aldrich) was purified by recrystallization from ethanol-water solution. The ligand was characterized by microanalyses, melting point and IR spectrum. The lauthanide basic carbonates were prepared by the method described by Willard[3] from the freshly ignited oxides. An aqueous ethanolic solution containing 3.2mmol of the ligand was added dropwise, under vigorous stirring, to an aqueous suspension containing 2 mmol of the lanthanide basic carbonate. The solution was heated at 50--60°C and after reduction of the volume. The compounds were obtained in powdered form. The compounds that precipetated were filtered, washed with hot alcohol, and dried in a vacuum desicator over P4Om Analysis. The lanthanide content was determined by the standard EITI'A compleximetric titration using xylenol orange as the indicator. Microanalyses were performed by the microanalytical Lab. of the University of S~o Paulo Instrumentation. IR slP,ctra were recorded on Nujol and Fluorolube with a Beckman IR-10 spectrophotometer. The electronic absorption spectra, the emission spectrum of the europium compound, and the melting points, were obtained using the methods previously reported(4, 5].

RESULTS AND DISCUSSION

The reaction between the lanthanide basis carbonates and chelidonic acid (LH2) results in the formation of solid crystalline compounds. The results of the analysis of these compounds are presented in Table 1. These analytical results are in good accord with the formulation Ln2L3 • 7H20, where Ln = Nd, Eu and Ho. The compounds are only slightly hydroscopic, with their decomposition points higher than 300°C. All the compounds studied exhibit very similar IR spectra and show in all cases the presence of water molecules. The ligand free exhibits a rich IR spectrum in the 1800-600cm-' region. The relevant bands of the ligand have a strong band of intensity at 1725 cm-t and a medium band at about 1450cm-t. The first band at 1725 cm-~, generally assigned to the antisymmetry carbonyl stretch in the COOH ~'oups[6] is totally absent in the spectra of the complexes. This band is replaced by a very strong one centered at 1620-1630 cm-' which is probably the antisymmetric stretching mode of the coordinated carboxylate[4,7]~ The second band assigned to the symmetry CO stretch is shifted at 1410-1420 cm-I in compounds. These same trends have been observed for carboxylates[7-8] with other lanthanides and the spectra are characteristic. These compounds bad sufficientlylow solubilities in the usual solvents to unable us to obtain good quality solution electronic spectra. However, the electronic absorption spectrum of the neodymium compound in Nujol mull shows the peaks are shifted only a little towards the red, compared to the aquo ion. In this case of the five peaks in the Nd(lII) spectrum between 400 and 9G0nm this displacement measured from the center of each band averages 12 nm (with respect to the aquo-ion). This indicates an appreciable degree of covalency in the ligandto lanthanide bond [9]. The europium compound luminesces very strongly when excited with near ultraviolet radiation. All transitions originate on the SD manifold (mainly from SDo excited state) of Eu(llI) and terminate on the "11:o,7Ft and ~Fz components of the ground 7F term[10]. The most intense transition is SDo ~'~F2, followed by 5Do~TFI and by a very weak 5Do-~'PFo. A summar~ of the crystal-field splitting for the dominant angular monenta, ], in C2~. C2 and Cs symmetries together with the transitions allowed for magnetic dipolar selection rules (SDo--~'~Ft) or electric dipolar selection rules (SDo-~Fo,~F2) appears in Table 2. The emission spectrum is in agreement with what would be expected of Eu3+ in a C2, environment.

Acknowledgements--The authors gratefully acknowledge financial support from OAS (BR-02-CB-A), CNPq and FINEP. We are also grateful to Prof. W. M. de Azevedo and Dr. A. A. da Gama for helpful discussions.

TaMe 1. Analytical data for Ln3L3"7H20 compounds ANALYSIS Z metal

Z carbon

Z hldrogen

Compound Theor E ~ t l

Theor Exptl

Theor E x p t l

Nd2L3"7R20

30,02 - 30p05

26,25 - 26.23

2,09 - 2 , 1 0

Eu2L3"TH20

3 1 , 1 2 - 29,79

2 5 , 8 3 - 25,06

2,06 - 2 . 2 0

Ho2L3.TH20

32,91 - 32,98

25.16 - 25,85

2,01 - 2 , 1 0

Notes

!504

Table 2. Allowed transitions between selected states in C2v, C2 and Cs symmetries Transition

C2v

C2

Cs

Assignments (nm)

7Fo

AI

~

AI

A

÷

A

A' * A'

580,4

5D ° * 7F 1

A1

÷

A2

A

~

A

A' ÷ A'

591,5

A1

~

B1

A

÷

2B

A' ÷ 24%"

594,0

A1

~

B2

AI

~

2A 1

A

÷

3BA

A' ~ 3A'

AI

~

B1

A

÷

2B

A' ÷ 2A"

A1

÷

B2

5Do ~

5D ° +

7F 2

595,8

615,9

618,0 619,8

Departamento de Qufmica M.A.V. DE ALMEIDA Universidade Federal Rural de Pernambuco 50000 Recife, PE., Brasil Departamento de Ffsica Laborat6rio BS/ TR I Universidade Federal de Pernambuco 50000 Recife, PE., Brasil

613,5

G.F. DE SA*

REFERENCES

I. D. L. Hoof, D. G. Tisley and R. A. Walton, J. C. S. Dalton, 200 (1973).

*To whom correspondence should be addressed.

2. E. Hansson, Acta Chem. Scand. 27, 8 (1973) and references therein. 3. H. Willard et al. Precipitation from Homogeneus Solutions, Wiley, New York (1959). 4. G. F. de Sfi and B. de B. Neto, Proc. 12th Rare Research Conference 1, 186 (1976). 5. G. F. de S~i and M. A. V. de Almeida, J. Coord. Chem. 10, 35 (1981)). 6. K. Nakamoto, IR Spectra of Inorganic and Coordination Compounds, Wiley, New York (1970). 7. K. Nakamoto, Y. Morimoto and A. E. MartelI,J. Am. Chem. Soc. 84, 2081 0962). 8. D. G. Karraker, J. Inorg. Nucl. Chem. 31, 2815 0%9). 9. C. K. JCrgensen, R. Papalardo 'and H. H. Schmidtke, J. Chem. Phys. 39, 1422 (1963). 10. L. G. Dcshazer and G. H. Dieke, J. Chem. Phys. 38, 2190 (1%3).

J. inotg, ucl. Chem. Vol. 42, pp. 1504-1506

Pergamon Press Ltd., 1960. Printed in Great Britain

Triphenylphosphine-induced declusterification of di-p-carbonyl-tris(cyciopentadienylnickei) (First received 29 November 1979; receivedfor publication 8 February 1980) Di-#-carbonyl-tris(cyclopentadienylnickel), (,/5-CsHs)~Ni3(CO)2, l, was first reported by Fischer and Palm[l] in 1958. The structure[2] of I consists of a triangle of nickel atoms with a

,

x

C5H5 ring bonded in pentahapto fashion to each nickel and two triply bridging carbonyl groups. Molecular orbital calculations and ESR studies[3, 4] and magnetic susceptibility measurements[l] support its formulation as a closed-shell paramagnetic complex. Until now, however, no reports of the reaction of I with electron-donor ligands such as triphenylphosphine have appeared. We wish to report that PPh3 reacts with I in refluxing tetrahydrofuran solution to effect "declusterification," affording nickelocene, (PPh3hNi(CO)2, and (PPh3)3Ni(CO). EXPERIMENTAL

o

Materials. Di-#-carbonyl-tris(cyclopentadienylnickel) and authentic samples of bis(tripbenylphosphine) nickel dicarbonyl and nickelocene used for identification of reaction products are commercially available. Tetrahydrofuran, benzene, and hexanes were purified by distillation from lithium aluminum hydride,