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Hexafluoroarsenate as a non-coordinating anion in lanthanide complexes with the diphenyl sulphoxide ligand
Journal
of the Less-Common
Metals,
305
94 (1983) 305-308
HEXAFLUOROARSE~ATE AS A NAN-COORDINATING LANTHANIDE COMPLEXES WITH THE DIPHENYL SULPHOXIDE LIGAND*
ANION
IN
SBRGIO MAIA MEL0
Departamento de Quimica Urgcinica e Inorgdnieu, Un~vers~dade Federal da Ceard, 60.000 FortaEeza (Brazil) ALEXANDRE
DE SOUSA SILVEIRA
Departamento de CiBncias da Natureza, Funda& (Brazil)
Universidade Federal do Acre, 69.900 Rio Branco
(Received February 3,1983)
Summary A series of compounds of general formula [Ln(dpso),](AsF,), (dpso = diphenyl sulphoxide; Ln m Y, La-Lu) was synthesized and characterized. IR spectroscopy indicates that the dpso is coordinated through its oxygen atom and that the 0, symmetry of the AsF,- is not changed. The emission spectrum of the europium(II1) complex in the visible region shows a group of lines in agreement with CJ, symmetry.
1. Introduction Seven-coordinated
lanthanide
(Ln) complexes
of the type LnX,sxdpso
(dpso = diphenyl sulphoxide), where X is a non-coordinating anion (PF,- or ClO,-), are known [l, Z]. Six- and eight-coordination has been observed in lanthanide(II1) complexes containing perchlorate and iodide anions [S]. The synthesis and fluorescence spectra of complexes of the type [Ln(dpso)7](AsF6)3 are described here. 2. Experimental
details
The rare earth oxides (purity, 99.99%) were obtained from Rare Inorganic Chemicals, Milwaukee, WI. dpso (Aldrich) was used as received. Potassium hexafluoroarsenate (Alfa-Ventron) was used to precipitate the hydrated lanthanide salts. *Paper presented at the Sixteenth Rare Earth Research Conference, Tallahassee, FL, U.S.A., April B-21,1983. 00225088/83/$3.00
The Florida State University,
0 Elsevier Sequoia/Printed
in The Netherlands
306
Substantial quantities of precipitate were formed when dpso was stirred with the lanthanide hexafluoroarsenates in an anhydrous acetone-ethanol mixture. The lanthanide content was determined using standard ethylenediaminetetraacetate complexometric titration. The carbon and hydrogen contents were determined by microanalyses performed by the Centre d’Analyse, Centre National de la Recherche Scientifique. The sulphoxide content was determined using the Douglas method [4], and arsenic was determined as the AsF,- anion by anion exchange and potentiometric titration. The IR spectra were recorded in Nujol mulls using a Perkin-Elmer 283B spectrophotometer. The fluorescence spectrum of the europium compound was measured using a Perkin-Elmer MPF-44B spectrofluorometer.
3. Results and discussion The complexes were crystalline. They were soluble in a number of solvents but not in water and ethanol. The partial elemental analysis of the dried solids and the molar conductivity data for millimolar solutions of the complexes in acetonitrile, nitromethane and nitrobenzene are shown in Table 1. The hexafluoroarsenate content was determined by using an anion exchange resin to obtain the equivalent quantities of AsF,- ions after performing a potentiometric titration with NaOH solution.
TABLE 1 Analysis and conductivity
data for the complexes [Ln(dpso),](AsF,),
so(%)
Ln (%)
Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yh Lu
AsFs- (%) cm*
Observed
Calculated
Observed
Calculated
Observed
Calculated
4.27 6.57 6.67 6.63 6.67 6.99 7.18 1.48 1.51 7.48 7.71 7.72 7.84 7.96 8.23
4.21 6.59 6.60 6.63 6.77 7.05 7.11 7.34 7.42 1.57 1.67 7.77 7.85 8.02 8.10
16.0 15.5 15.0 15.5 15.8 15.2 16.1 15.6 15.5 15.8 15.8 15.5 15.1 15.6 15.4
16.2 15.8 15.8 15.8 15.8 15.7 15.7 15.7 15.6 15.6 15.6 15.6 15.6 15.5 15.5
26.1 27.7 26.2 28.0 27.0 26.0 27.4 28.0 26.6 26.8 25.6 25.8 26.3 25.2 26.0
27.26 26.78 26.70 26.69 26.60 26.57 26.55 26.50 26.41 26.43 26.42 26.39 26.34 26.29 26.27
‘In nitromethane. bin nitrobenzene. ‘In acetonitrile.
mol - i)
242’, 70.5”, 444’ 71.5b 228’ 78.5b 73.5b, 409’ 235”, 70.5b 439’ 256’ 420’ 257’, 72.5b 74.4b, 403’ 251’ 73.2b, 399’
425 390
684 s 540 s
438 w, b
stretch stretch stretch stretch deformation deformation deformation dependent deformation stretch
C-C C-C C-C C-C C-H C-H C-H Mass C-H
S-O
-
680 535 510 480
1019 s 996m 912 w 755 s 735 s 692 s
stretch
C-H
480 s
1020 1000 912 755 740 690
dpso
Assignment
vs, very strong; s, strong; m, medium; w, weak; b, broad; sh, shoulder.
970
3053 1949 1876 1797 1742 1584 1475 1448 1330 1310 1170 1160 1084 1081
3053 1949 w 1876 w 1797 w 1742 w 1584 w 1475 w 1443 s 1321 w 1305 w 1164 w 1155 w, sh 1089 vs 1071 sh
1040 vs
CNd(dpsohl(AsF&
and [Nd(dpso),](AsF,),
dpso
IR data for diphenyl sulphoxide
TABLE 2
deformation deformation deformation deformation
v,(AsF, - )
Out-of-plane ring deformation
v3(AsF,-) masking ring deformation C-H stretch
C-H Ring C-H C-H
Assignment
308
The IR spectra of the complexes show a shift in the S-O stretching mode from 1040 cm-’ in the dpso-free compound to 970-960 cm-’ in the complexes. The C-S stretching frequency observed at 680 cm- 1 in the free ligand is masked by one of the absorption frequencies of the AsF,anion. The substantial decrease of 80 cm- ’ in the S-O stretching frequency indicates bonding through the oxygen atoms [5]. In the regions of the hexafluoroarsenate vibrations the spectra show intense absorptions at 690 cm-’ (v3) and 390 cm-’ (vq) which are assigned to the Oh symmetry [6] of the uncoordinated AsF, - anion (see Table 2). The fluorescence spectrum of the europium complex shows that its structure is different from that of the euro,pium perchlorates and hexafluorophosphates. These compounds have a higher symmetry than those where the 5D, + ‘F, transition is absent. The coordination polyhedra of sevencoordinated compounds are generally assumed to be monocapped octahedra, monocapped trigonal prisms or pentagonal prisms [2]. The number of transitions appearing in the fluorescence spectrum of the europium compound at 77 K (Table 3) suggests that the site symmetry around the europium(II1) ion is probably C3”. Therefore the coordination polyhedron of this complex is probably the monocapped trigonal prism. TABLE 3 Transitions
observed in the emission spectrum of [Eu(dpso),](AsF,),
Assignment
Peakposition
Assignment
5D, + ‘F,
*D, + ‘F,
5D, -, ‘F,
17256 16949 16891 16346 16233 16077 15358 15325 15313 14635 14224
Peakposition (cm-‘)
(cm-‘) SD, + ‘F, 5D, -, ‘F,
at 77 K
‘D, + ‘F, 5D, + ‘F,
sD, + ‘F,
5D, + ‘F,
5D, + ‘F,
18993 18622 18686 18628 18315 17950 18083 17970 17814 17095 17062 17050 16372
References S. K. Ramalingam and S. Soundararajan, Bull. Chem. Sot. Jpn., 41(1968) 106. 0. A. Serra and L. C. Thompson, in C. J. Kevane and T. Moeller (eds.), Proc. 10th Rare Earth Research Conf., Carefree, AZ, 1973, U.S. Atomic Energy Commission, Technical Information Center, Oak Ridge, TN, 1973. D. K. Koppikar and S. Soundararajan, J. Inorg. Nucl. Chem., 38(1976) 174. T. B. Douglas, J. Am. Chem. Sot., SS(1946) 1072. F. A. Cotton and R. Francis, J. Am. Chem. Sot., 82(1960) 2986. F. A. Cotton, Chemical Applications of Group Theory, Wiley-Interscience, New York, 2nd edn., 1976, p. 329.
of the Less-Common
Metals,
305
94 (1983) 305-308
HEXAFLUOROARSE~ATE AS A NAN-COORDINATING LANTHANIDE COMPLEXES WITH THE DIPHENYL SULPHOXIDE LIGAND*
ANION
IN
SBRGIO MAIA MEL0
Departamento de Quimica Urgcinica e Inorgdnieu, Un~vers~dade Federal da Ceard, 60.000 FortaEeza (Brazil) ALEXANDRE
DE SOUSA SILVEIRA
Departamento de CiBncias da Natureza, Funda& (Brazil)
Universidade Federal do Acre, 69.900 Rio Branco
(Received February 3,1983)
Summary A series of compounds of general formula [Ln(dpso),](AsF,), (dpso = diphenyl sulphoxide; Ln m Y, La-Lu) was synthesized and characterized. IR spectroscopy indicates that the dpso is coordinated through its oxygen atom and that the 0, symmetry of the AsF,- is not changed. The emission spectrum of the europium(II1) complex in the visible region shows a group of lines in agreement with CJ, symmetry.
1. Introduction Seven-coordinated
lanthanide
(Ln) complexes
of the type LnX,sxdpso
(dpso = diphenyl sulphoxide), where X is a non-coordinating anion (PF,- or ClO,-), are known [l, Z]. Six- and eight-coordination has been observed in lanthanide(II1) complexes containing perchlorate and iodide anions [S]. The synthesis and fluorescence spectra of complexes of the type [Ln(dpso)7](AsF6)3 are described here. 2. Experimental
details
The rare earth oxides (purity, 99.99%) were obtained from Rare Inorganic Chemicals, Milwaukee, WI. dpso (Aldrich) was used as received. Potassium hexafluoroarsenate (Alfa-Ventron) was used to precipitate the hydrated lanthanide salts. *Paper presented at the Sixteenth Rare Earth Research Conference, Tallahassee, FL, U.S.A., April B-21,1983. 00225088/83/$3.00
The Florida State University,
0 Elsevier Sequoia/Printed
in The Netherlands
306
Substantial quantities of precipitate were formed when dpso was stirred with the lanthanide hexafluoroarsenates in an anhydrous acetone-ethanol mixture. The lanthanide content was determined using standard ethylenediaminetetraacetate complexometric titration. The carbon and hydrogen contents were determined by microanalyses performed by the Centre d’Analyse, Centre National de la Recherche Scientifique. The sulphoxide content was determined using the Douglas method [4], and arsenic was determined as the AsF,- anion by anion exchange and potentiometric titration. The IR spectra were recorded in Nujol mulls using a Perkin-Elmer 283B spectrophotometer. The fluorescence spectrum of the europium compound was measured using a Perkin-Elmer MPF-44B spectrofluorometer.
3. Results and discussion The complexes were crystalline. They were soluble in a number of solvents but not in water and ethanol. The partial elemental analysis of the dried solids and the molar conductivity data for millimolar solutions of the complexes in acetonitrile, nitromethane and nitrobenzene are shown in Table 1. The hexafluoroarsenate content was determined by using an anion exchange resin to obtain the equivalent quantities of AsF,- ions after performing a potentiometric titration with NaOH solution.
TABLE 1 Analysis and conductivity
data for the complexes [Ln(dpso),](AsF,),
so(%)
Ln (%)
Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yh Lu
AsFs- (%) cm*
Observed
Calculated
Observed
Calculated
Observed
Calculated
4.27 6.57 6.67 6.63 6.67 6.99 7.18 1.48 1.51 7.48 7.71 7.72 7.84 7.96 8.23
4.21 6.59 6.60 6.63 6.77 7.05 7.11 7.34 7.42 1.57 1.67 7.77 7.85 8.02 8.10
16.0 15.5 15.0 15.5 15.8 15.2 16.1 15.6 15.5 15.8 15.8 15.5 15.1 15.6 15.4
16.2 15.8 15.8 15.8 15.8 15.7 15.7 15.7 15.6 15.6 15.6 15.6 15.6 15.5 15.5
26.1 27.7 26.2 28.0 27.0 26.0 27.4 28.0 26.6 26.8 25.6 25.8 26.3 25.2 26.0
27.26 26.78 26.70 26.69 26.60 26.57 26.55 26.50 26.41 26.43 26.42 26.39 26.34 26.29 26.27
‘In nitromethane. bin nitrobenzene. ‘In acetonitrile.
mol - i)
242’, 70.5”, 444’ 71.5b 228’ 78.5b 73.5b, 409’ 235”, 70.5b 439’ 256’ 420’ 257’, 72.5b 74.4b, 403’ 251’ 73.2b, 399’
425 390
684 s 540 s
438 w, b
stretch stretch stretch stretch deformation deformation deformation dependent deformation stretch
C-C C-C C-C C-C C-H C-H C-H Mass C-H
S-O
-
680 535 510 480
1019 s 996m 912 w 755 s 735 s 692 s
stretch
C-H
480 s
1020 1000 912 755 740 690
dpso
Assignment
vs, very strong; s, strong; m, medium; w, weak; b, broad; sh, shoulder.
970
3053 1949 1876 1797 1742 1584 1475 1448 1330 1310 1170 1160 1084 1081
3053 1949 w 1876 w 1797 w 1742 w 1584 w 1475 w 1443 s 1321 w 1305 w 1164 w 1155 w, sh 1089 vs 1071 sh
1040 vs
CNd(dpsohl(AsF&
and [Nd(dpso),](AsF,),
dpso
IR data for diphenyl sulphoxide
TABLE 2
deformation deformation deformation deformation
v,(AsF, - )
Out-of-plane ring deformation
v3(AsF,-) masking ring deformation C-H stretch
C-H Ring C-H C-H
Assignment
308
The IR spectra of the complexes show a shift in the S-O stretching mode from 1040 cm-’ in the dpso-free compound to 970-960 cm-’ in the complexes. The C-S stretching frequency observed at 680 cm- 1 in the free ligand is masked by one of the absorption frequencies of the AsF,anion. The substantial decrease of 80 cm- ’ in the S-O stretching frequency indicates bonding through the oxygen atoms [5]. In the regions of the hexafluoroarsenate vibrations the spectra show intense absorptions at 690 cm-’ (v3) and 390 cm-’ (vq) which are assigned to the Oh symmetry [6] of the uncoordinated AsF, - anion (see Table 2). The fluorescence spectrum of the europium complex shows that its structure is different from that of the euro,pium perchlorates and hexafluorophosphates. These compounds have a higher symmetry than those where the 5D, + ‘F, transition is absent. The coordination polyhedra of sevencoordinated compounds are generally assumed to be monocapped octahedra, monocapped trigonal prisms or pentagonal prisms [2]. The number of transitions appearing in the fluorescence spectrum of the europium compound at 77 K (Table 3) suggests that the site symmetry around the europium(II1) ion is probably C3”. Therefore the coordination polyhedron of this complex is probably the monocapped trigonal prism. TABLE 3 Transitions
observed in the emission spectrum of [Eu(dpso),](AsF,),
Assignment
Peakposition
Assignment
5D, + ‘F,
*D, + ‘F,
5D, -, ‘F,
17256 16949 16891 16346 16233 16077 15358 15325 15313 14635 14224
Peakposition (cm-‘)
(cm-‘) SD, + ‘F, 5D, -, ‘F,
at 77 K
‘D, + ‘F, 5D, + ‘F,
sD, + ‘F,
5D, + ‘F,
5D, + ‘F,
18993 18622 18686 18628 18315 17950 18083 17970 17814 17095 17062 17050 16372
References S. K. Ramalingam and S. Soundararajan, Bull. Chem. Sot. Jpn., 41(1968) 106. 0. A. Serra and L. C. Thompson, in C. J. Kevane and T. Moeller (eds.), Proc. 10th Rare Earth Research Conf., Carefree, AZ, 1973, U.S. Atomic Energy Commission, Technical Information Center, Oak Ridge, TN, 1973. D. K. Koppikar and S. Soundararajan, J. Inorg. Nucl. Chem., 38(1976) 174. T. B. Douglas, J. Am. Chem. Sot., SS(1946) 1072. F. A. Cotton and R. Francis, J. Am. Chem. Sot., 82(1960) 2986. F. A. Cotton, Chemical Applications of Group Theory, Wiley-Interscience, New York, 2nd edn., 1976, p. 329.