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N,N-dimethylacetamide adducts of the lanthanide chlorides
J. inorg,nucl.Chem.,1968,VoL30, pp. 2771to 2778. PergamonPress. Printedin Great Britain
N,N-DIMETHYLACETAMIDE LANTHANIDE
ADDUCTS CHLORIDES
OF
THE
G. V I C E N T I N I and R. N A J J A R Department of Chemistry, Faculdade de Filosofia, Cifincias e Letras and Faculdade de Farmficia e Bioquimica, University of Sao Paulo, Brazil
(Received 18 December 1967) A b s t r a c t - C o m p o u n d s of general formula LNCI3.3.5 D M A (Ln = Ce. Pr, Nd, Sm, Eu, Gd, Tb, Dy and D M A = N,N-dimethylacetamide) and LnCI:c3 D M A (Ln = Y. Ho, Er, Tm, Yb, Lu) have been obtained by the reaction between hydrated lanthanide chlorides and N,N-dimethylacetamide. The spectra between 340 and 900 m/x, the i.r. spectra and the molar conductivities (including the compound LaCI:~.4 D M A described in a recent article) of the compounds have been determined. INTRODUCTION
THE REACTIONS between N,N-dimethylacetamide (DMA) and hydrated lanthanide salts are being systematically investigated. Some of the results obtained with perchlorates [1 ], nitrates [2], acetates [3] were published. In a recent article [4] we described the preparation of some lanthanum salt adducts with D M A , including the lanthanum trichloride-tetra kis-N ,N-dimethylacetamide (LaCI3.4 D M A) [4]. In the present paper we describe the reaction between hydrated lanthanide chlorides and DMA. Compounds corresponding to the general formula LnCI:c3-5 D M A (Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy) and LnCI3.3 DMA (Ln = Y, Ho, Er, Tm, Yb, Lu) were obtained. The spectra in D M A between 340 and 900 m/z, the i.r. spectra and the molar conductivities of the compounds (including in this case the compound LaCI3.4 DMA) have been determined. EXPERIMENTAL
Materials. The hydrated lanthanide chlorides were prepared from 99.9 per cent pure oxides (Johnson, Matthey and Co. London) by the reaction with concentrated hydrochloric acid. The hydrated cerium(! I 1) chloride was obtained by the reaction of cerous basic carbonate with diluted hydrochloric acid. The solutions obtained were evaporated in a water bath to near dryness, the crystals were collected and maintained in a desiccator over sodium hydroxide. Reagent quality N,N-dimethylacetamide from Koch-Light Laboratories Ltd, England, was fractionated. The nitromethane, from the Koch-Light Laboratories Ltd.. for the conductance measurements was fractionated and the middle fraction redistilled. Preparation o f the lanthanide chlorides N,N-dimethylacetamide adducts. The hydrated chlorides were dissolved in excess of warm N,N-dimethylacetamide and the solution boiled a few minutes. The solutions were cooled and the crystals formed were collected and maintained in vacuo over anhydrous calcium chloride. Analytical procedure. The lanthanides were determined by the oxalate-oxide method. Chloride was determined by passing an aqueous solution of the compound through a cationic resin column (Amberlite IR-120 H +) and titrating the liberated hydrochloric acid with standard alkali. Nitrogen was determined by hydrolysing the compound with sodium hydroxide solution, distilling the liberated dimethylamine into a measured excess of 0,1 M hydrochloric acid solution, and back-titrating the excess of acid. 1. 2. 3. 4.
T. Moeller and G. Vicentini,J. inorg, nucl. Chem. 27, 1477 (1965). G. Vicentini and E. de Carvalho Filho,J. inorg, nucl. Chem. 28, 2987 (1966). G. Vicentini andJ. C. Prado, Ci~ncia e Cultura 19, 687 (1967). G. Vicentini, M. Perrier, J. C. Prado and R. Najjar, An aisAcad, bras. Cienc. 39, 149 (1967). 2771
2772
G. V1CENT1NI and R. N A J J A R
Spectrophotometric measurements. Measurements in the region between 340 and 900 m/z were made with a Cary Model 14 Spectrophotometer. The measurements in the i.r. region were made with a Perkin-Elmer Model 221, using Nujol mulls between rock salt plates. C o n d u c t a n c e measurements. The conductance measurements were made at 25.00 __0.02°C with an Industrial Instrument Model RC-16B conductivity bridge, using a Leeds and Northrup cell (K~ = 0.10708).
RESULTS AND DISCUSSION
In this series of compounds three different types of adducts were observed, considering the compound of lanthanum. They are all hygroscopic and slightly soluble in DMA. The analytical data are summarized in Table 1. Table 1. Summary of analytical results Analysis (%) Ln
CI
N
Compound
Theor.
Exp.
Theor.
Exp,
Theor.
Exp.
CEC13,3.5 D M A PRC13"3.5 D M A NDC13-3.5 D M A SMC13.3.5 D M A EUC13.3-5 D M A GDC13.3.5 D M A TbCla,3.5 D M A DYC13.3.5 D M A Y C13'3 D M A HOC13.3 D M A ErCI3"3 D M A TmCla-3 D M A YbCla'3 D M A LuCla'3 D M A
25.41 25.51 25.96 26.76 26.97 27.65 27-87 28.32 19.46 30.96 31.26 31'47 31"99 32"24
25,36 25.50 26,13 26,58 27.04 27-66 27.90 28.25 19.25 31.13 31.14 31.34 31.92 32-17
19,28 19.26 19,14 18.93 18,88 18,70 18,65 18.53 23.29 19-96 19,88 19.81 19.66 19.59
19.24 19"21 19.19 18"89 18.84 18-62 18.64 18.75 23-06 19"85 19.75 19.79 19"54 19"61
8.89 8.87 8.82 8.72 8.70 8.62 8.59 8.54 9.20 9.88 7.85 7.82 7"76 7-74
8.60 8.56 8.66 8.42 8.42 8,39 8.31 8.66 9-00 7.84 7-60 7.65 7"66 7'74
Table 2. Some frequencies (cm -~) for the compounds of formula LnCh'x D M A Compound CeClz-3-5 D M A PrCIz.3.5 D M A NDC13.3-5 D M A SMC13"3"5 D M A EUC13.3"5 D M A GDC13-3"5 D M A TBC13.3'5 D M A DYC13"3'5 D M A YCI~.3 D M A HOC13.3 D M A ErCI3.3 D M A TmCI3.3 D M A YbCI3'3 D M A LtiCI3"3 D M A
vC--N v~O 1506 1502 1502 1506 1506 1506 1504 1504 1513 1515 1502 1515 1506 1515
1602 1582 1592 1602 1597 1602 1597 1607 1597 1602 1607 1602 1582 1597
vC--C--N--C 978 970 969 968 972 972 973 973 972 971 972 974 974 974
8C--C--N--C 755 749 750 750 752 751 752 752 749 748 748 752 751 751
N ,N-dimethylacetamide adducts of the lanthanide chlorides
2773
Infra-red spectra. The i.r. spectra of the solid adducts were determined in the NaC1 region. Some aspects may be considered: (a) absence of water bands indicating that anhydrous compounds were obtained; (b) a very significant shift of the C ~ O stretching mode of the amide to lower frequencies (to ca. 1600 cm -1) and small shifts of the C - - N stretching mode to higher frequencies are evidences for the coordination through the carbonyi oxygen: (c) small shifts to higher frequencies and a considerable increase in the bands near 730 cm -1 and 960 cm -~, as observed by Carty[5] in some D M A adducts. Table 2 contains some observed frequencies for the compounds obtained. Spectra in the region between 340 and 900 m l z - T a b l e 3 contains the molar absorptivities obtained for the different bands for the compounds in D M A . In Table 3, Molar absorptivities of LnCI:3 in N,N-Dimethylacetamide Ln
m/~
Pr
447,5 472 486 592
Nd
351 353 355
10.00 7.30 7.76
358 362-5 432 514 525 528 529 533 577 585 591 594 602 607 742 747 763 797 804 807 823 877.5
6.98 5-10 1.14 1-62 2.28 2.50 2.38 2.20 8.42 12.62 4.36 3.62 1.58 0.96 8.24 5,44 1.00 2.20 5.14 9.60 1.48 3.18
363 365 378 406 417
3.80 3.65 2.15 3.42 0.92
Sm
~
6.49 2-71 2.60 1.65
5. A . J . Carty, Can. J. Chem. 44, 1881 (1966).
Ln
m/~
Eu
375.5 394
1.70 3.10
Tb
369
0.17
372.5 377.5 487
0-16 0.28 0.04
Dy
352 366
4.28 3.25
Ho
362 419 448 455 459 538 652.5
9.34 1-94 12-49 5.08 7.02 2.72 0.88
Er
366 378 383 387 488 521 ~22 522.5 ~25 532.5 653
7.61 15.71 6.04 2.61 3-32 7-99 8.35 7.23 3.73 1.55 1.12
Tm
692.5 796
0-69 1.42
2774
G. V I C E N T I N I and R. NAJJAR
some cases (spectra of the compounds of Pr, Sm, Eu, Tb, Dy) the shape is not essentially modified but differences in the intensities of the bands and small shifts to the red are in general observed. The spectrum of the thullium compound presented a considerable shift to higher wavelength and an inversion in the intensities of the bands. The spectra of the compounds of neodymium (Figs. 1, 2 and 3), holmium (Fig. 4) and erbium (Fig. 5) are presented. In all three cases a considerable change in the spectra is observed as compared with the spectra of the respective perchlorates in aqueous solutions, giving us the idea of a chloride complexation. The spectra of the lanthanides are, on the other I
I
[
I
I
017 (16 05 0,4
01:3
\
0.2 OI O0
0.6
o z
0.5 0.4
~
0:3 02 OI 0.0 Q5 0.4 0..3 0.2
c
OJ 0.0 ~30
400
450
500
I
I
550
600
MILLIMICRONS
Fig. 1. (a) Absorption spectrum ol'0.0250 M NdCI3 in DMA (20.0 mm cell). (b) Absorption spectrum of 0-0250M NdCI3 containing 0.271 mot/I, of LiC1 in DMA (20.0mm cell). (c) Absorption spectrum of aqueous 0.0655 M Nd(CIO4)3 (10.0 mm cell).
N,N-dimethylacetamide adducts of the lanthanide chlorides I
I
I
2775
I
05
O4 O3 O2
/L
01 _
O0
_
A
02
~ o~ z
m
O6 O5 O4
03
02
01
O0 650
I
[
I
700
750
800
850
9OO
MILLIMICRONS
Fig. 2. (a) Absorption spectrum of 0.0250 M NdCl3 in D M A (20.0 mm cell), (b) Absorption spectrum of 0.0250 M NdCI:~ containing 0-271 mol/L of LiCI in DMA (20.0 mm cell). (c) Absorption spectrum of aqueous 0.0655 M Nd(C104)3 (I 0.0 mm cell).
....... t
o~7
z o93 O02
001 000 I
4oo
450
__
J
5oo
4oo
J
L
450 MILLIM~CRONS
50o
I
4o0
45o
50o
Fig. 3, (a) Absorption spectrum of 0.0250 M NdCI3 in DMA (z0.0 mm cell), (b) Absorption spectrum of 0.0250 M NdCla containing 0-271 mol/l, of LiCI in DMA (20.0 mm cell). (c) Absorption spectrum of aqueous 0.0655 M Nd (CIO4).~ (10.0 mm cell).
2776
G. VICENTINI and R. NAJJAR 07 06 05 04 0.3 0.2
0.1
0.7 0-6 0'5
0"3 0-2 0.1 0-0 0-5 0-4 03 02 Ol
0.0 I 350
[
I
400
450
I
500
I 55O
I
"600
650
MILLIMICRONS
Fig. 4. (a) Absorption spectrum of 0.0257 M HoC]~ D M A (20.0 mm ceil). (b) Absorption spectrum of 0.0257 M HoCh containing 0.253 tool/1, of" LiCI in D M A (20.0 mm cell). (c) Absorption spectrum of aqueous 0.1056 M Ho(CIO4)a (10-0 mm cell).
side, extremely dependent of the chloride ion concentration, indicating that anionic species might be present and that the symmetry around the central ion is probably altered and consequently considerable alterations in the spectra are observed (Figs. 1,2,3,4, and 5). Recently Ryan and J~rgensen [6] have observed hexalide complexes in aprotic solvents and isolated triphenylphosphonium and pyridinium salts, giving us a favorable argument for the existence of such anionic species in DMA solutions. C o n d u c t a n c e m e a s u r e m e n t s . Conductance data for the compounds in nitromethane are summarized in Table 4. These conductance values indicate that all the compounds are practically non electrolytes in this solvent. The existence of products of formula LnC13..3 DMA suggests the coordination number six for these compounds. However, the existence of compounds of the composition ENC13.3.5 DMA also gives us the idea that the DMA may act as 6. J. L. Ryanand C. K. Jergensen,J. phys. Chem. 70, 2845 (1966).
2777
N ,N-dimethylacetamide adducts of the lanthanide chlorides I
-
-
T
I
r~
]
05 04 0"3 02
OlI °° 06 L 05 I 0.4 !
~m O3
~o2
b
0"1
\
O-G 07 0"6 05 04 0"3
~V
Oq O4? 55O
3 400
L450
L 500
J 550
t
I
600
650
~]
MkLLIMICRONS
Fig. 5. (a) Absorption spectrum of 0.0197 M ErCI3 in D M A (20.0 mm cell). (b) Absorption spectrum of 0.0197 M ErCI3 containing 0.287 mol/I, of LiCI in D M A (20.0 mm cell). (c) Absorption spectrum of aqueous 0.0526 M Er(CIO4)3 (20.0 mm cell), Table 4. Electrolytic conductance in nitromethane Compound
A,,(mho, cm 2, mole -1)
LaCI3.4 D M A CEC13-3.5 D M A PRC13-3.5 D M A NdCI.~.3.5 D M A SMC13.3'5 D M A EuCI3.3.5 D M A GdCI~.3-5 D M A TbCI.~-3.5 D M A DyCI3-3.5 D M A YCla.3 D M A HOC13.3 D M A ErC13-3 D M A TmCI3-3 D M A YbCI3.3 D M A LuCI3-3 D M A
4,7 7.2 8.5 6-2 7.5 8.0 6.0 6.4 2.9 6.8 7.0 5.0 2.7 5-3 6.4
2778
G. VICENTINI and R. NAJJAR
bridges a n d b o n d i n g t h r o u g h the n i t r o g e n is n o t e x c l u d e d . F o r this r e a s o n we do n o t s p e c u l a t e a b o u t the c o o r d i n a t i o n n u m b e r of the l a n t h a n i d e ion in t h e s e compounds.
Acknowledgements-The authors are much indebted to Professor P. Krumholz for many valuable suggestions and discussions, and to the Ford Foundation and Fundo de Amparo h Pesquisa do Estado de Sho Paulo for financial support.
N,N-DIMETHYLACETAMIDE LANTHANIDE
ADDUCTS CHLORIDES
OF
THE
G. V I C E N T I N I and R. N A J J A R Department of Chemistry, Faculdade de Filosofia, Cifincias e Letras and Faculdade de Farmficia e Bioquimica, University of Sao Paulo, Brazil
(Received 18 December 1967) A b s t r a c t - C o m p o u n d s of general formula LNCI3.3.5 D M A (Ln = Ce. Pr, Nd, Sm, Eu, Gd, Tb, Dy and D M A = N,N-dimethylacetamide) and LnCI:c3 D M A (Ln = Y. Ho, Er, Tm, Yb, Lu) have been obtained by the reaction between hydrated lanthanide chlorides and N,N-dimethylacetamide. The spectra between 340 and 900 m/x, the i.r. spectra and the molar conductivities (including the compound LaCI:~.4 D M A described in a recent article) of the compounds have been determined. INTRODUCTION
THE REACTIONS between N,N-dimethylacetamide (DMA) and hydrated lanthanide salts are being systematically investigated. Some of the results obtained with perchlorates [1 ], nitrates [2], acetates [3] were published. In a recent article [4] we described the preparation of some lanthanum salt adducts with D M A , including the lanthanum trichloride-tetra kis-N ,N-dimethylacetamide (LaCI3.4 D M A) [4]. In the present paper we describe the reaction between hydrated lanthanide chlorides and DMA. Compounds corresponding to the general formula LnCI:c3-5 D M A (Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy) and LnCI3.3 DMA (Ln = Y, Ho, Er, Tm, Yb, Lu) were obtained. The spectra in D M A between 340 and 900 m/z, the i.r. spectra and the molar conductivities of the compounds (including in this case the compound LaCI3.4 DMA) have been determined. EXPERIMENTAL
Materials. The hydrated lanthanide chlorides were prepared from 99.9 per cent pure oxides (Johnson, Matthey and Co. London) by the reaction with concentrated hydrochloric acid. The hydrated cerium(! I 1) chloride was obtained by the reaction of cerous basic carbonate with diluted hydrochloric acid. The solutions obtained were evaporated in a water bath to near dryness, the crystals were collected and maintained in a desiccator over sodium hydroxide. Reagent quality N,N-dimethylacetamide from Koch-Light Laboratories Ltd, England, was fractionated. The nitromethane, from the Koch-Light Laboratories Ltd.. for the conductance measurements was fractionated and the middle fraction redistilled. Preparation o f the lanthanide chlorides N,N-dimethylacetamide adducts. The hydrated chlorides were dissolved in excess of warm N,N-dimethylacetamide and the solution boiled a few minutes. The solutions were cooled and the crystals formed were collected and maintained in vacuo over anhydrous calcium chloride. Analytical procedure. The lanthanides were determined by the oxalate-oxide method. Chloride was determined by passing an aqueous solution of the compound through a cationic resin column (Amberlite IR-120 H +) and titrating the liberated hydrochloric acid with standard alkali. Nitrogen was determined by hydrolysing the compound with sodium hydroxide solution, distilling the liberated dimethylamine into a measured excess of 0,1 M hydrochloric acid solution, and back-titrating the excess of acid. 1. 2. 3. 4.
T. Moeller and G. Vicentini,J. inorg, nucl. Chem. 27, 1477 (1965). G. Vicentini and E. de Carvalho Filho,J. inorg, nucl. Chem. 28, 2987 (1966). G. Vicentini andJ. C. Prado, Ci~ncia e Cultura 19, 687 (1967). G. Vicentini, M. Perrier, J. C. Prado and R. Najjar, An aisAcad, bras. Cienc. 39, 149 (1967). 2771
2772
G. V1CENT1NI and R. N A J J A R
Spectrophotometric measurements. Measurements in the region between 340 and 900 m/z were made with a Cary Model 14 Spectrophotometer. The measurements in the i.r. region were made with a Perkin-Elmer Model 221, using Nujol mulls between rock salt plates. C o n d u c t a n c e measurements. The conductance measurements were made at 25.00 __0.02°C with an Industrial Instrument Model RC-16B conductivity bridge, using a Leeds and Northrup cell (K~ = 0.10708).
RESULTS AND DISCUSSION
In this series of compounds three different types of adducts were observed, considering the compound of lanthanum. They are all hygroscopic and slightly soluble in DMA. The analytical data are summarized in Table 1. Table 1. Summary of analytical results Analysis (%) Ln
CI
N
Compound
Theor.
Exp.
Theor.
Exp,
Theor.
Exp.
CEC13,3.5 D M A PRC13"3.5 D M A NDC13-3.5 D M A SMC13.3.5 D M A EUC13.3-5 D M A GDC13.3.5 D M A TbCla,3.5 D M A DYC13.3.5 D M A Y C13'3 D M A HOC13.3 D M A ErCI3"3 D M A TmCla-3 D M A YbCla'3 D M A LuCla'3 D M A
25.41 25.51 25.96 26.76 26.97 27.65 27-87 28.32 19.46 30.96 31.26 31'47 31"99 32"24
25,36 25.50 26,13 26,58 27.04 27-66 27.90 28.25 19.25 31.13 31.14 31.34 31.92 32-17
19,28 19.26 19,14 18.93 18,88 18,70 18,65 18.53 23.29 19-96 19,88 19.81 19.66 19.59
19.24 19"21 19.19 18"89 18.84 18-62 18.64 18.75 23-06 19"85 19.75 19.79 19"54 19"61
8.89 8.87 8.82 8.72 8.70 8.62 8.59 8.54 9.20 9.88 7.85 7.82 7"76 7-74
8.60 8.56 8.66 8.42 8.42 8,39 8.31 8.66 9-00 7.84 7-60 7.65 7"66 7'74
Table 2. Some frequencies (cm -~) for the compounds of formula LnCh'x D M A Compound CeClz-3-5 D M A PrCIz.3.5 D M A NDC13.3-5 D M A SMC13"3"5 D M A EUC13.3"5 D M A GDC13-3"5 D M A TBC13.3'5 D M A DYC13"3'5 D M A YCI~.3 D M A HOC13.3 D M A ErCI3.3 D M A TmCI3.3 D M A YbCI3'3 D M A LtiCI3"3 D M A
vC--N v~O 1506 1502 1502 1506 1506 1506 1504 1504 1513 1515 1502 1515 1506 1515
1602 1582 1592 1602 1597 1602 1597 1607 1597 1602 1607 1602 1582 1597
vC--C--N--C 978 970 969 968 972 972 973 973 972 971 972 974 974 974
8C--C--N--C 755 749 750 750 752 751 752 752 749 748 748 752 751 751
N ,N-dimethylacetamide adducts of the lanthanide chlorides
2773
Infra-red spectra. The i.r. spectra of the solid adducts were determined in the NaC1 region. Some aspects may be considered: (a) absence of water bands indicating that anhydrous compounds were obtained; (b) a very significant shift of the C ~ O stretching mode of the amide to lower frequencies (to ca. 1600 cm -1) and small shifts of the C - - N stretching mode to higher frequencies are evidences for the coordination through the carbonyi oxygen: (c) small shifts to higher frequencies and a considerable increase in the bands near 730 cm -1 and 960 cm -~, as observed by Carty[5] in some D M A adducts. Table 2 contains some observed frequencies for the compounds obtained. Spectra in the region between 340 and 900 m l z - T a b l e 3 contains the molar absorptivities obtained for the different bands for the compounds in D M A . In Table 3, Molar absorptivities of LnCI:3 in N,N-Dimethylacetamide Ln
m/~
Pr
447,5 472 486 592
Nd
351 353 355
10.00 7.30 7.76
358 362-5 432 514 525 528 529 533 577 585 591 594 602 607 742 747 763 797 804 807 823 877.5
6.98 5-10 1.14 1-62 2.28 2.50 2.38 2.20 8.42 12.62 4.36 3.62 1.58 0.96 8.24 5,44 1.00 2.20 5.14 9.60 1.48 3.18
363 365 378 406 417
3.80 3.65 2.15 3.42 0.92
Sm
~
6.49 2-71 2.60 1.65
5. A . J . Carty, Can. J. Chem. 44, 1881 (1966).
Ln
m/~
Eu
375.5 394
1.70 3.10
Tb
369
0.17
372.5 377.5 487
0-16 0.28 0.04
Dy
352 366
4.28 3.25
Ho
362 419 448 455 459 538 652.5
9.34 1-94 12-49 5.08 7.02 2.72 0.88
Er
366 378 383 387 488 521 ~22 522.5 ~25 532.5 653
7.61 15.71 6.04 2.61 3-32 7-99 8.35 7.23 3.73 1.55 1.12
Tm
692.5 796
0-69 1.42
2774
G. V I C E N T I N I and R. NAJJAR
some cases (spectra of the compounds of Pr, Sm, Eu, Tb, Dy) the shape is not essentially modified but differences in the intensities of the bands and small shifts to the red are in general observed. The spectrum of the thullium compound presented a considerable shift to higher wavelength and an inversion in the intensities of the bands. The spectra of the compounds of neodymium (Figs. 1, 2 and 3), holmium (Fig. 4) and erbium (Fig. 5) are presented. In all three cases a considerable change in the spectra is observed as compared with the spectra of the respective perchlorates in aqueous solutions, giving us the idea of a chloride complexation. The spectra of the lanthanides are, on the other I
I
[
I
I
017 (16 05 0,4
01:3
\
0.2 OI O0
0.6
o z
0.5 0.4
~
0:3 02 OI 0.0 Q5 0.4 0..3 0.2
c
OJ 0.0 ~30
400
450
500
I
I
550
600
MILLIMICRONS
Fig. 1. (a) Absorption spectrum ol'0.0250 M NdCI3 in DMA (20.0 mm cell). (b) Absorption spectrum of 0-0250M NdCI3 containing 0.271 mot/I, of LiC1 in DMA (20.0mm cell). (c) Absorption spectrum of aqueous 0.0655 M Nd(CIO4)3 (10.0 mm cell).
N,N-dimethylacetamide adducts of the lanthanide chlorides I
I
I
2775
I
05
O4 O3 O2
/L
01 _
O0
_
A
02
~ o~ z
m
O6 O5 O4
03
02
01
O0 650
I
[
I
700
750
800
850
9OO
MILLIMICRONS
Fig. 2. (a) Absorption spectrum of 0.0250 M NdCl3 in D M A (20.0 mm cell), (b) Absorption spectrum of 0.0250 M NdCI:~ containing 0-271 mol/L of LiCI in DMA (20.0 mm cell). (c) Absorption spectrum of aqueous 0.0655 M Nd(C104)3 (I 0.0 mm cell).
....... t
o~7
z o93 O02
001 000 I
4oo
450
__
J
5oo
4oo
J
L
450 MILLIM~CRONS
50o
I
4o0
45o
50o
Fig. 3, (a) Absorption spectrum of 0.0250 M NdCI3 in DMA (z0.0 mm cell), (b) Absorption spectrum of 0.0250 M NdCla containing 0-271 mol/l, of LiCI in DMA (20.0 mm cell). (c) Absorption spectrum of aqueous 0.0655 M Nd (CIO4).~ (10.0 mm cell).
2776
G. VICENTINI and R. NAJJAR 07 06 05 04 0.3 0.2
0.1
0.7 0-6 0'5
0"3 0-2 0.1 0-0 0-5 0-4 03 02 Ol
0.0 I 350
[
I
400
450
I
500
I 55O
I
"600
650
MILLIMICRONS
Fig. 4. (a) Absorption spectrum of 0.0257 M HoC]~ D M A (20.0 mm ceil). (b) Absorption spectrum of 0.0257 M HoCh containing 0.253 tool/1, of" LiCI in D M A (20.0 mm cell). (c) Absorption spectrum of aqueous 0.1056 M Ho(CIO4)a (10-0 mm cell).
side, extremely dependent of the chloride ion concentration, indicating that anionic species might be present and that the symmetry around the central ion is probably altered and consequently considerable alterations in the spectra are observed (Figs. 1,2,3,4, and 5). Recently Ryan and J~rgensen [6] have observed hexalide complexes in aprotic solvents and isolated triphenylphosphonium and pyridinium salts, giving us a favorable argument for the existence of such anionic species in DMA solutions. C o n d u c t a n c e m e a s u r e m e n t s . Conductance data for the compounds in nitromethane are summarized in Table 4. These conductance values indicate that all the compounds are practically non electrolytes in this solvent. The existence of products of formula LnC13..3 DMA suggests the coordination number six for these compounds. However, the existence of compounds of the composition ENC13.3.5 DMA also gives us the idea that the DMA may act as 6. J. L. Ryanand C. K. Jergensen,J. phys. Chem. 70, 2845 (1966).
2777
N ,N-dimethylacetamide adducts of the lanthanide chlorides I
-
-
T
I
r~
]
05 04 0"3 02
OlI °° 06 L 05 I 0.4 !
~m O3
~o2
b
0"1
\
O-G 07 0"6 05 04 0"3
~V
Oq O4? 55O
3 400
L450
L 500
J 550
t
I
600
650
~]
MkLLIMICRONS
Fig. 5. (a) Absorption spectrum of 0.0197 M ErCI3 in D M A (20.0 mm cell). (b) Absorption spectrum of 0.0197 M ErCI3 containing 0.287 mol/I, of LiCI in D M A (20.0 mm cell). (c) Absorption spectrum of aqueous 0.0526 M Er(CIO4)3 (20.0 mm cell), Table 4. Electrolytic conductance in nitromethane Compound
A,,(mho, cm 2, mole -1)
LaCI3.4 D M A CEC13-3.5 D M A PRC13-3.5 D M A NdCI.~.3.5 D M A SMC13.3'5 D M A EuCI3.3.5 D M A GdCI~.3-5 D M A TbCI.~-3.5 D M A DyCI3-3.5 D M A YCla.3 D M A HOC13.3 D M A ErC13-3 D M A TmCI3-3 D M A YbCI3.3 D M A LuCI3-3 D M A
4,7 7.2 8.5 6-2 7.5 8.0 6.0 6.4 2.9 6.8 7.0 5.0 2.7 5-3 6.4
2778
G. VICENTINI and R. NAJJAR
bridges a n d b o n d i n g t h r o u g h the n i t r o g e n is n o t e x c l u d e d . F o r this r e a s o n we do n o t s p e c u l a t e a b o u t the c o o r d i n a t i o n n u m b e r of the l a n t h a n i d e ion in t h e s e compounds.
Acknowledgements-The authors are much indebted to Professor P. Krumholz for many valuable suggestions and discussions, and to the Ford Foundation and Fundo de Amparo h Pesquisa do Estado de Sho Paulo for financial support.