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Peroxo complexes of chromium(VI), molybdenum(VI), tungsten(VI) and zirconium(IV) ions containing tridentate and quadridentate neutral ligands
Polyhedron Vol. 1 I, No. 7, pp. 795-798, Printed in Great Britain
1992 0
PEROXO COMPLEXES OF CHROMIUM(VI), MOLYBDENUM(VI), TUNGSTEN(W) AND ZIRCONIUM(W) IONS CONTAINING TRIDENTATE QUADRIDENTATE NEUTRAL LIGANDS M. T. H. TARAFDER,*
P. BHATTACHARJEE
0277-5X37/92 $5.CO+.OO 1992 Pergamon Press plc
AND
and A. K. SARKAR
Department of Chemistry, University of Rajshahi, Rajshahi, Bangladesh (Received 22 October 1991; accepted 5 November 1991)
Abstract-Several organoperoxo complexes of compositions [M(O),(O,)(L)] [M = CrV’, MoV’ and WV’; L = diethylene triamine(det), 2,2,2_triethylenetetraamine(tet) and 2,3,2triethylenetetraamine (2,3,2-tet)] and [Zr(O)(O,)(2,3,Ztet)] have been synthesized and characterized. These complexes were all non-electrolytes in DMSO and inert towards oxidation. The IR spectral data indicate that the ~~(0-0) stretching mode decreases with the increase in atomic number of metals in a group.
The chemistry of peroxo complexes has received considerable attention in recent years, I-’ 3 because they are the potential sources of active oxygen atoms and can be used as stoichiometric as well as catalytic oxidants for organic and inorganic substrates. l-7 The coordinated peroxo moiety is greatly stabilized by co-ligands of multidentate nature, terdentate or quadridentates, in particular. 8-’3 We are interested in extending such a study to new peroxo complexes of different elements of groups 6A and 4A containing terdentate and quadridentate open chain nitrogen donor ligands. We report here the synthesis of these complexes and studies on their potential as oxygen transfer reagents. An attempt has also been made to study the effect of the size of the metal ions on ~~(0-0) modes of the complexes in their IR spectra. EXPERIMENTAL IR spectra (as KBr discs) were recorded with a Pye-Unicam SP3-300 IR spectrophotometer. Conductivities of lo- 3 M solutions of the complexes in dimethyl sulphoxide (DMSO) were measured at 25°C using a WPA CM35 conductivity meter and dip-type cell with platinized electrodes.
*Author to whom correspondence should be addressed. 795
Reagents
All chemicals used were reagent grade and were used as supplied by E. Merck. Analyses
Carbon, hydrogen and nitrogen analyses were carried out by the Microanalytical Services at the University of St Andrews, Scotland. Preparation of the complexes General method for the preparation of complexes
[Cr(0),(02)L] [L = NH2CH2CH2NHCH2CH2NH2 (det), NH2CH2CH2NHCH2CH2NHCH2CH2NH2NH2 (tet), NH2CH2CH2NHCH,CH2CH2NHCH2CH2 NH, (2,3,2-tet)] (1, 2 and 3). Cr03 (0.01 mol) dissolved in cold 30% H202 (60 cm’) was added to a cold solution of L (0.01 mol) in ethanol (100 cm’). The mixture was further cooled in an ice-salt bath and the products which separated out were filtered and washed with ethanol and ether and dried in vucuo over P,O, ,,. General method for the preparation of the complexes [M(O),(O,)L] (L = det, tet and 2,3,2-tet;
M = MoV’ and WV’) (47). A suspension of MO3 (0.01 mol) in 30% H202 (80 cm3) was stirred for 6 h at 4045°C. This was filtered and to the clear filtrate was added a solution of L (0.01 mol) in
796
et al.
M. T. H. TARAFDER
ethanol (100 cm’). The mixture was stirred whilst cooling at the same time in an ice-salt bath. A precipitate appeared which was washed successively with ethanol and ether and stored as above. Preparation of [Zr(O)(O,)(2,3,2-tet)] (8). A solution of ZrOClz (0.01 mol) in 30% H202 (65 cm’) was added to a solution of 2,3,2-tet (0.01 mol) in ethanol (100 cm3). The product was filtered, washed successively with ethanol and ether, and stored.
M-N bonding is shown by the appearance of M-N stretching vibrations at 280-325 cm-’ (Table 2) in the far-1 R spectra of the complexes. 5-’3 Complexes 14 show diagnostic bands at 880-910 cm- ‘, attributable to v(M=O) modes.4’9” ‘-I3 The metal peroxo grouping (local Czv symmetry) gives rise to three IR and Raman-active vibrational modes. These are predominantly O-O stretching (vl), the symmetric M-O stretch (vz) and the antisymmetric M-O stretch (v3). The characteristic ~~(0-0) modes of 1-8 appear at 800-870 cm-’ (Table 2). In particular, the v, mode decreases upon passing from chromium complexes (1,2 and 3) (865, 870 and 860 cm-‘) to the corresponding molybdenum complexes (4, 5 and 6) (810, 820 and 830 cm- ‘), which is then further decreased in the tungsten peroxo complex (7) (800 cm-‘). The vl mode of the zirconium peroxo complex (8) appears at 840 cm-‘, higher than that in the thorium peroxo complex, for instance [Th(02)((&H ‘4N202)] (v I : 805 cm- ’ ). ” The present study thus clearly reveals that for M(0,) grouping, the ~~(0-0) modes decrease with an increase in the atomic number of metals in a particular group. The present peroxo complexes display v3 and v2 modes at 60&650 and 510-555 cm- ‘, respectively (Table 2).
Attempted reactions of 4 and 5 with triphenylphosphine and triphenylarsine, respectively. Reflux-
ing of 4 and 5 with equimolar quantities of triphenylphosphine and triphenylarsine, respectively, in THF for 48 h failed to produce any reaction ; 4 and 5 were recovered unchanged. RESULTS
AND DISCUSSION
The analytical and conductivity data are presented in Table 1. The molar conductance data indicated that all of the complexes were undissociated. These data are consistent with seven-fold coordination of the Zr’” complex, while the Cr”‘, MO”’ and WV’ complexes are eight-coordinated with the peroxo groups side-bonded to the metal atoms. Griffith et al. I4 reported recently a number of eight-coordinate organoperoxo complexes of elements of group 5A. The complexes 1 and 4 are, however, likely to contain seven-coordinate Cr”’ and MO”’ ions, respectively. IR spectral data are shown in Table 2. All of the complexes have characteristic v(NH,) and v(NH) stretching modes in the regions 335&3460 and 3 lo&3 160 cm- ‘, respectively. ’ ‘,’ 6 The presence of
Table 1. Analytical
Compound Kr(WOz)(det)l (1) Kr(WW(tet)l(2) [Cr(WW(2,3,2-tet)l(3)
~MdOMW(det)l(4) W~OM02Net)l (5) tMo(O),(O,)(2,3,2-tet)l(6;
W&%(%)@et)1(7) [zr(o>(o,)(2,3,2-tet)l@)
Reactivity
Compounds 4 and 5 were inert towards phosphine and arsine. These negative results outline the enhanced stability of the metal peroxo moiety in the presence of terdentate or quadridentate ligands which precludes oxygen transfer reactions. We
data and other physical properties
Colour
Carbon (%) Calc. Found
Yellow Yellow Yellow Yellow
21.9 27.5 30.4 18.3
21.8 27.3 30.2 18.1
Yellow
23.5
23.3
Yellow Yellow Colourless
26.3
26.1 18.1 26.4
18.3 26.6 _
‘The organic moieties for the compounds
indicated
are :
of the complexes”
Hydrogen (%) Calc. Found 5.9 6.9 7.3 4.9
Nitrogen (%) Calc. Found 19.0 21.3 20.3 15.8
Molar conductance R- ’ cm2 mol
5.8 6.7 7.1 4.7
19.2 21.4 20.3 15.9
2 1 4 1
5.9
5.8
18.3
18.1
3
6.3 4.6 6.4
6.2 4.4 6.1
17.5 14.2 17.7
17.2 14.1 17.5
2 2 4
Peroxo complexes
of Cr”‘, MO”‘, WV’ and Zr’”
Table 2. IR spectral data for the complexes
Compound
797
band maxima (cm - ‘)
v(NH,)
v(M=O)
3400w 3350m 3100m
900s
865~s
630sh
535w
280m
3405m 3360~ 3110m
900m
870s
640sh
510br
310w
3400w 3355w 3105m
900m
860s
600sh
530br
305w
341ow 3370m 3145br
910vs
810s
625s
520m
280~
3450br 3380m 3140w
910vs
820m
630~s
555m
310w
3460br 3375w 3160br
910vs
830s
625~s
520m
310w
3420br 3360m 3180m
880m
8OOn-l
650sh
520~
295m
3400w 3355m 3120m
900s
840s
610sh
510m
325m
v(M-N)
“Relative band intensities are denoted by vs, s, m, w, br and sh, representing strong, strong, medium, weak, broad and shoulder, respectively.
observed similar behaviour for various peroxo complexes containing multidentate ligands. I”-’ 3 Mimoun et al. 2s’7 argued that insertion of substrates like phosphines or arsines into the metal-peroxide bond forming a peroxymetallocycle is a concerted process, but perhaps the multidentate co-ligands greatly stabilize the peroxo ligand and that the nucleophiles (PPh3 or AsPh,) cannot cause opening
of the metal peroxo triangle, thus explaining the inertness of these complexes. Acknowledgements-We are indebted to the Department of Chemistry, Rajshahi University, Bangladesh, for the provision of laboratory facilities. Financial assistance provided by the Bangladesh University Grants Commission, Dhaka, is gratefully acknowledged.
REFERENCES 1. D. A. Muccigrosso, S. E. Jacobson, P. A. Apgar and F. Mares, J. Am. Chem. Sot. 1978,100,7063.
very
2. H. Mimoun, J. Molec. Catal. 1980, 7, 1. 3. A. D. Westland, F. Haque and J. M. Bouchard, Inorg. Chem. 1980, 19,2255. 4. A. D. Westland and M. T. H. Tarafder, Znorg. Chem. 1981,20,3992. 5. A. D. Westland and M. T. H. Tarafder, Znorg. Chem. 1982,21,3228. 6. M. T. H. Tarafder and M. A. L. Miah, Znorg. Chem. 1986,25,2265. 7. M. T. H. Tarafder and A. R. Khan, Polyhedron 1987, 6, 275. 8. M. T. H. Tarafder and A. Ahmed, Znd. J. Chem.
1986,25A, 729. 9. M. T. H. Tarafder, M. B. H. Howlader, B. Nath, R. Khan and A. A. M. A. Islam, Polyhedron 1989, 8, 977. 10. M. T. H. Tarafder, Znd. J. Chem. 1987,26A, 874. 11. M. T. H. Tarafder and A. A. M. A. Islam, Polyhedron 1989,8, 109. 12. M. T. H. Tarafder and A. R. Khan, Polyhedron 199 1, 10, 819.
798
M. T. H. TARAFDER
13. M. T. H. Tarafder and A. R. Khan, Polyhedron 1991, 10, 973. 14. A. C. Dengel and W. P. Griffith, Polyhedron 1989, 8, 1371. 15. D. A. House, R. W. Hay and M. A. Ali, Znorg. Chim. Acta 1983,72, 239.
et al.
16. R. W. Hay and M. T. H. Tarafder, J. Chem. Sot., Dalton Trans. 1991, 823. 17. H. Mimoun, M. Postel, F. Casabiance, J. Fischer and A. Mitschler, Znorg. Chem. 1982, 21, 1303.
1992 0
PEROXO COMPLEXES OF CHROMIUM(VI), MOLYBDENUM(VI), TUNGSTEN(W) AND ZIRCONIUM(W) IONS CONTAINING TRIDENTATE QUADRIDENTATE NEUTRAL LIGANDS M. T. H. TARAFDER,*
P. BHATTACHARJEE
0277-5X37/92 $5.CO+.OO 1992 Pergamon Press plc
AND
and A. K. SARKAR
Department of Chemistry, University of Rajshahi, Rajshahi, Bangladesh (Received 22 October 1991; accepted 5 November 1991)
Abstract-Several organoperoxo complexes of compositions [M(O),(O,)(L)] [M = CrV’, MoV’ and WV’; L = diethylene triamine(det), 2,2,2_triethylenetetraamine(tet) and 2,3,2triethylenetetraamine (2,3,2-tet)] and [Zr(O)(O,)(2,3,Ztet)] have been synthesized and characterized. These complexes were all non-electrolytes in DMSO and inert towards oxidation. The IR spectral data indicate that the ~~(0-0) stretching mode decreases with the increase in atomic number of metals in a group.
The chemistry of peroxo complexes has received considerable attention in recent years, I-’ 3 because they are the potential sources of active oxygen atoms and can be used as stoichiometric as well as catalytic oxidants for organic and inorganic substrates. l-7 The coordinated peroxo moiety is greatly stabilized by co-ligands of multidentate nature, terdentate or quadridentates, in particular. 8-’3 We are interested in extending such a study to new peroxo complexes of different elements of groups 6A and 4A containing terdentate and quadridentate open chain nitrogen donor ligands. We report here the synthesis of these complexes and studies on their potential as oxygen transfer reagents. An attempt has also been made to study the effect of the size of the metal ions on ~~(0-0) modes of the complexes in their IR spectra. EXPERIMENTAL IR spectra (as KBr discs) were recorded with a Pye-Unicam SP3-300 IR spectrophotometer. Conductivities of lo- 3 M solutions of the complexes in dimethyl sulphoxide (DMSO) were measured at 25°C using a WPA CM35 conductivity meter and dip-type cell with platinized electrodes.
*Author to whom correspondence should be addressed. 795
Reagents
All chemicals used were reagent grade and were used as supplied by E. Merck. Analyses
Carbon, hydrogen and nitrogen analyses were carried out by the Microanalytical Services at the University of St Andrews, Scotland. Preparation of the complexes General method for the preparation of complexes
[Cr(0),(02)L] [L = NH2CH2CH2NHCH2CH2NH2 (det), NH2CH2CH2NHCH2CH2NHCH2CH2NH2NH2 (tet), NH2CH2CH2NHCH,CH2CH2NHCH2CH2 NH, (2,3,2-tet)] (1, 2 and 3). Cr03 (0.01 mol) dissolved in cold 30% H202 (60 cm’) was added to a cold solution of L (0.01 mol) in ethanol (100 cm’). The mixture was further cooled in an ice-salt bath and the products which separated out were filtered and washed with ethanol and ether and dried in vucuo over P,O, ,,. General method for the preparation of the complexes [M(O),(O,)L] (L = det, tet and 2,3,2-tet;
M = MoV’ and WV’) (47). A suspension of MO3 (0.01 mol) in 30% H202 (80 cm3) was stirred for 6 h at 4045°C. This was filtered and to the clear filtrate was added a solution of L (0.01 mol) in
796
et al.
M. T. H. TARAFDER
ethanol (100 cm’). The mixture was stirred whilst cooling at the same time in an ice-salt bath. A precipitate appeared which was washed successively with ethanol and ether and stored as above. Preparation of [Zr(O)(O,)(2,3,2-tet)] (8). A solution of ZrOClz (0.01 mol) in 30% H202 (65 cm’) was added to a solution of 2,3,2-tet (0.01 mol) in ethanol (100 cm3). The product was filtered, washed successively with ethanol and ether, and stored.
M-N bonding is shown by the appearance of M-N stretching vibrations at 280-325 cm-’ (Table 2) in the far-1 R spectra of the complexes. 5-’3 Complexes 14 show diagnostic bands at 880-910 cm- ‘, attributable to v(M=O) modes.4’9” ‘-I3 The metal peroxo grouping (local Czv symmetry) gives rise to three IR and Raman-active vibrational modes. These are predominantly O-O stretching (vl), the symmetric M-O stretch (vz) and the antisymmetric M-O stretch (v3). The characteristic ~~(0-0) modes of 1-8 appear at 800-870 cm-’ (Table 2). In particular, the v, mode decreases upon passing from chromium complexes (1,2 and 3) (865, 870 and 860 cm-‘) to the corresponding molybdenum complexes (4, 5 and 6) (810, 820 and 830 cm- ‘), which is then further decreased in the tungsten peroxo complex (7) (800 cm-‘). The vl mode of the zirconium peroxo complex (8) appears at 840 cm-‘, higher than that in the thorium peroxo complex, for instance [Th(02)((&H ‘4N202)] (v I : 805 cm- ’ ). ” The present study thus clearly reveals that for M(0,) grouping, the ~~(0-0) modes decrease with an increase in the atomic number of metals in a particular group. The present peroxo complexes display v3 and v2 modes at 60&650 and 510-555 cm- ‘, respectively (Table 2).
Attempted reactions of 4 and 5 with triphenylphosphine and triphenylarsine, respectively. Reflux-
ing of 4 and 5 with equimolar quantities of triphenylphosphine and triphenylarsine, respectively, in THF for 48 h failed to produce any reaction ; 4 and 5 were recovered unchanged. RESULTS
AND DISCUSSION
The analytical and conductivity data are presented in Table 1. The molar conductance data indicated that all of the complexes were undissociated. These data are consistent with seven-fold coordination of the Zr’” complex, while the Cr”‘, MO”’ and WV’ complexes are eight-coordinated with the peroxo groups side-bonded to the metal atoms. Griffith et al. I4 reported recently a number of eight-coordinate organoperoxo complexes of elements of group 5A. The complexes 1 and 4 are, however, likely to contain seven-coordinate Cr”’ and MO”’ ions, respectively. IR spectral data are shown in Table 2. All of the complexes have characteristic v(NH,) and v(NH) stretching modes in the regions 335&3460 and 3 lo&3 160 cm- ‘, respectively. ’ ‘,’ 6 The presence of
Table 1. Analytical
Compound Kr(WOz)(det)l (1) Kr(WW(tet)l(2) [Cr(WW(2,3,2-tet)l(3)
~MdOMW(det)l(4) W~OM02Net)l (5) tMo(O),(O,)(2,3,2-tet)l(6;
W&%(%)@et)1(7) [zr(o>(o,)(2,3,2-tet)l@)
Reactivity
Compounds 4 and 5 were inert towards phosphine and arsine. These negative results outline the enhanced stability of the metal peroxo moiety in the presence of terdentate or quadridentate ligands which precludes oxygen transfer reactions. We
data and other physical properties
Colour
Carbon (%) Calc. Found
Yellow Yellow Yellow Yellow
21.9 27.5 30.4 18.3
21.8 27.3 30.2 18.1
Yellow
23.5
23.3
Yellow Yellow Colourless
26.3
26.1 18.1 26.4
18.3 26.6 _
‘The organic moieties for the compounds
indicated
are :
of the complexes”
Hydrogen (%) Calc. Found 5.9 6.9 7.3 4.9
Nitrogen (%) Calc. Found 19.0 21.3 20.3 15.8
Molar conductance R- ’ cm2 mol
5.8 6.7 7.1 4.7
19.2 21.4 20.3 15.9
2 1 4 1
5.9
5.8
18.3
18.1
3
6.3 4.6 6.4
6.2 4.4 6.1
17.5 14.2 17.7
17.2 14.1 17.5
2 2 4
Peroxo complexes
of Cr”‘, MO”‘, WV’ and Zr’”
Table 2. IR spectral data for the complexes
Compound
797
band maxima (cm - ‘)
v(NH,)
v(M=O)
3400w 3350m 3100m
900s
865~s
630sh
535w
280m
3405m 3360~ 3110m
900m
870s
640sh
510br
310w
3400w 3355w 3105m
900m
860s
600sh
530br
305w
341ow 3370m 3145br
910vs
810s
625s
520m
280~
3450br 3380m 3140w
910vs
820m
630~s
555m
310w
3460br 3375w 3160br
910vs
830s
625~s
520m
310w
3420br 3360m 3180m
880m
8OOn-l
650sh
520~
295m
3400w 3355m 3120m
900s
840s
610sh
510m
325m
v(M-N)
“Relative band intensities are denoted by vs, s, m, w, br and sh, representing strong, strong, medium, weak, broad and shoulder, respectively.
observed similar behaviour for various peroxo complexes containing multidentate ligands. I”-’ 3 Mimoun et al. 2s’7 argued that insertion of substrates like phosphines or arsines into the metal-peroxide bond forming a peroxymetallocycle is a concerted process, but perhaps the multidentate co-ligands greatly stabilize the peroxo ligand and that the nucleophiles (PPh3 or AsPh,) cannot cause opening
of the metal peroxo triangle, thus explaining the inertness of these complexes. Acknowledgements-We are indebted to the Department of Chemistry, Rajshahi University, Bangladesh, for the provision of laboratory facilities. Financial assistance provided by the Bangladesh University Grants Commission, Dhaka, is gratefully acknowledged.
REFERENCES 1. D. A. Muccigrosso, S. E. Jacobson, P. A. Apgar and F. Mares, J. Am. Chem. Sot. 1978,100,7063.
very
2. H. Mimoun, J. Molec. Catal. 1980, 7, 1. 3. A. D. Westland, F. Haque and J. M. Bouchard, Inorg. Chem. 1980, 19,2255. 4. A. D. Westland and M. T. H. Tarafder, Znorg. Chem. 1981,20,3992. 5. A. D. Westland and M. T. H. Tarafder, Znorg. Chem. 1982,21,3228. 6. M. T. H. Tarafder and M. A. L. Miah, Znorg. Chem. 1986,25,2265. 7. M. T. H. Tarafder and A. R. Khan, Polyhedron 1987, 6, 275. 8. M. T. H. Tarafder and A. Ahmed, Znd. J. Chem.
1986,25A, 729. 9. M. T. H. Tarafder, M. B. H. Howlader, B. Nath, R. Khan and A. A. M. A. Islam, Polyhedron 1989, 8, 977. 10. M. T. H. Tarafder, Znd. J. Chem. 1987,26A, 874. 11. M. T. H. Tarafder and A. A. M. A. Islam, Polyhedron 1989,8, 109. 12. M. T. H. Tarafder and A. R. Khan, Polyhedron 199 1, 10, 819.
798
M. T. H. TARAFDER
13. M. T. H. Tarafder and A. R. Khan, Polyhedron 1991, 10, 973. 14. A. C. Dengel and W. P. Griffith, Polyhedron 1989, 8, 1371. 15. D. A. House, R. W. Hay and M. A. Ali, Znorg. Chim. Acta 1983,72, 239.
et al.
16. R. W. Hay and M. T. H. Tarafder, J. Chem. Sot., Dalton Trans. 1991, 823. 17. H. Mimoun, M. Postel, F. Casabiance, J. Fischer and A. Mitschler, Znorg. Chem. 1982, 21, 1303.