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Penta-coordinate complexes of palladium(II) chloride with sulphur (Naphthyl thiourea) and nitrogen (Heterocyclic amines) containing ligands
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PENTA-COORDINATE COMPLEXES OF PALLADIUM(II) CHLORIDE WITH SULPHUR (NAPHTHYL THIOUREA) AND NITROGEN (HETEROCYCLIC AMINES) CONTAINING LIGANDS M. MAHFOOZ KHAN Department of Chemistry, Aligarh Muslim University, Aligarh, U.P., India
t Receired 20 S~7~temher 1972) Abstract On the interaction of naphthyl thiourea with palladium(lI) chloride in methanol a pentacoordinate complex, [Pd(Ntu)4CI]CI, was obtained. On further coordination of this species with 2,2'dipyridyl, o-phenanthroline, pyridine, :g/:¢ and y-picolines, 2-4 and 2-6 lutidines, quinoline, isoquinoline and acridine mixed ligand penta-coordinate complexes of the type [Pd(Ntu)~LCI 1C1 and [Pd(Ntul2 L',CI1CI (where L stands for 2,2'-dipyridyl and o-phenanthroline and L' for pyridine, :
INTRODUCTION
lutidine (2-4L), 2-6,1utidine (2-6L), quinoline IQ), isoquinoline (Isoq) and acridine (acrid) were all AnalaR, B.D.H. products and used as such, whereas picolines. lutidines and quinolines were further purified by redistillation. Preparation of naphdTyl thiourea palladium(II ) chhn'ide About 50 ml aqueous solution of 1 per cent palladium(lI) chloride containing a few drops of conc. HCI was added to 100 ml solution of 5 per cent naphthyl thiourea in methyl alcohol. The resulting solution was heated over a water bath for about five minutes and filtered. The filtrate was kept for crystallization and after about three days lemon coloured crystals of the complex appeared. The crystals were separated from the main liquor and recrystallized from acetone. Finally, they were dried in a vacuum desiccator over CaO.
THE ABILI'rYof nitrogen and sulphur containing ligands to form complexes with palladium{II) are well known [1-5]. However, palladium(II) ions are one of the heavier elements which have a pronounced tendency to form square planar complexes[6]. Besides tetra coordinate complexes, there are some penta-coordinate species with trigonal bipyramidal structures which act as 1 : 1 electrolytes in solution[7]. But hexa-coordinate complexes of palladium(lI) are rare and a large number of complexes which were previously considered to be octahedral have later been shown not to be soE8 101. Although there is some evidence for higher coordination by the action of excess halide ion on chelates such as [Pd phen2] 2+ and tetrahalogeno palladates(II)[11]. This paper describes the preparation and properties of penta coordinate complex of palladium(II) chloride with naphthyl thiourea. The complex, [Pd(Ntu)4CI]CI, is further subjected to substitution reaction with some heterocyclic amines resulting in the formation of penta-coordinate mixed ligand species. All the complexes are characterized by elemental analysis, molar conductance values, and the bonding discussed on the basis of i.r. and far i.r. spectra studies.
1. Monochlorotetrakis (naphthyl chloride, [Pd(Ntu)4Cll CI
thiourea)
palladium(If)
Lemon yellow crystals, decomp, point 183°C, molar conductance in methyl alcohol 96"01 cm2,'fl. Calcd for C44H4oN8S4 Pd Cb: C, 53,58: H, 4.06; N, 11.37: S, l"!.98: C1, 7.20; Pd, 10.79. Found: C, 54.20; H, 4.23: N. 11.00: S, 12.88; C1, 7.41; Pd, 10-81. General method for the preparation of mixed ligand complexes from monochlorotetrakis (naphthyl thiourea) palladium(II) chloride. Solutions of naphthyl thiourea complex and heterocyclic amine in methyl alcohol were mixed in 1:5 molar ratio. The solution was filtered and the filtrate was heated on a water bath to complete dryness. To the impure dried compound methanol was again added and heated to complete dryness. After repeating this process at least three or four times,
EXPERIMENTAL
Palladium(I1) chloride (Johnson Matthey and Co.), and naphthyl thiourea (Ntu), o-phenanthroline (o-phen), 2,2'dipyridyl tdipy), :~-picoline (~-pic), fl-picoline (fl-pic), 2-4, 299
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M. MAHFOOZKHAN
the unreacted ligand was removed by washing the complex several times with small aliquots of acetone, in which the amines were highly soluble, the pure complex being poorly soluble. The purified complex was crystallized from methyl alcohol.
2. Monochloro bis(naphthyl thiourea) bis pyridine palladium(II) chloride, [Pd(Ntu)2(py)2Cl]C1 Brown crystalline substance, decomp, point 138°C, conductance in methyl alcohol 89-37cm2/t). Calcd for Ca2HaoN6S2 Pd C12: C, 51'9; H, 4-05; N, 11'3; S, 8-65; Cl, 9"60; Pd, 14'39. Found: C, 52'83; H, 4"25; N, 10"91; 8"51; C1, 9.52; Pd, 14"60.
3. Monochloro bis(naphthyl thiourea) bis(ct-picoline) paUadium(II) chloride, [Pd(Ntu)2(ct-pic)2C1]Cl Brown crystalline substance, m.p. 134°C, molar conductance 101.20 cm2/~. Calcd for C34Ha4N6S2 Pd C12: C, 53-16; H, 4.19; N, 10.94; S, 8.06; Cl, 9-25; Pd, 13'86. Found: C, 54'50; H, 4.3; N, 10'58; S, 8'25; C1, 9.57; Pd, 13.51.
4. Monochloro bis(naphthyl thiourea) bis(fl-picoline) palladium(II) chloride, [Pd(Ntu)2(fl-pic)2Cl~C1 Brown crystalline substance, molar conductance 99.28 cm2/f~. Calcd for C34H34N652 Pd C12: C, 53.16; H, 4.19; N, 10.94; S, 8"05; Cl, 9.25; Pd, 13.86. Found: 54.18; H, 4.55; N, 10.59; S, 8.23; Cl, 9.18; Pd, 13.59.
5. Monochloro bis(naphthyl thiourea) bis(~-picoline) palladium(II) chloride, [Pd(Ntu)2(7-pic)2C1]C1 Brown crystalline substance, molar conductance 121.8 cm2/f~. Calcd for C34H34N6S2 Pd C12: C, 53.16; H, 4.19; N, 10.94; S, 8.06; Cl, 9.25; Pd, 13"86. Found: C, 54.44; H, 4.39; N, 10.80; S, 8.10; Cl, 9.35; Pd, 13.55.
6. Monochloro bis(naphthyl thiourea) bis(2-4,1utidine) palladium(II) chloride, [Pd(Ntu)z(2-4,L)2Cl] C1 Brown crystalline substance, decomp, point 138° C, molar conductance 110.0cm2/f~. Calcd for C36H3aN6S2 Pd C12: C, 54.32; H, 4.77; N, 10.56; S, 8.04; C1, 8.92; Pd, 13.37. Found: C, 55.80; H, 4.80; N, 10.09; S, 8.10; C1, 8.81; Pd, 13.29.
7. Monochloro bis(naphthyl thiourea) bis(2-6,1utidine) palladium (II) chloride, [Pd(Ntu)z(2-6,L)2CI] CI Brown crystalline substance, molar conductance 110-01 cm2/~. Calcd for C36HaaN6S2 Pd C12: C, 54-32; H, 4.77; N, 10"56; S, 8.04; C1, 8"92; Pd, 13-37. Found: C, 56"01; H, 4.71; N, 10.48; S, 8-11; C1, 8.87; Pd, 13-41.
8. Monochloro bis(naphthyl thiourea) palladium(II) chloride, [Pd(Ntu)2(Q)2C1]CI
bis
quinoline
Black crystalline substance, decomp, point 114°C, molar conductance 90.38 cm2/~. Calcd for C4oH34N6S2 Pd C12: C, 57-17; H, 4.19; N, 10.07; S, 7.62; C1, 8-45; Pd, 12.67. Found: C, 55.01 ; H, 4.20; N, 10.20; S, 7.81 ; Cl, 8.35; Pd, 12.59.
9. Monochloro bis(naphthyl thiourea) bis(isoquinoline) palladium(II) chloride, [Pd(Ntu)2(Isoq)2 C1]C1 Black crystalline substance, m.p. 115°C, molar conductance 91.50 cm2/~. Calcd for C40H34N6S2 Pd CI2: C, 57.17;
H, 4.19; N, 10.07; S, 7.62; CI, 8.45; Pd, 12.67. Found: C, 56.81; H, 3.99; N, 10.24; S, 7.63; C1, 8-38; Pd, 12.72. 10. Monochloro bis(naphthyl thiourea) bis palladium(II) chloride, [Pd(Ntu)2(acrid)2C1]C1
acridine
Brown crystalline substance, m.p. 116°C, molar conductance 121"0cm2/~. Calcd for C48H38N6S2 Pd C12: C, 61'13; H, 4.04; N, 8.94; S, 6.81; C1, 7.55; Pd, 11.32. Found: C, 62.27; H, 4.21; N, 8.71; S, 6'90; CI, 7.44; Pd, 11.46.
11. Monochloro bis(naphthyl thiourea) mono(o-phenanthroline) palladium(II) chloride, [Pd(Ntu)2(o-phen)C1]C1 Orange yellow crystalline substance, m.p. 113°C, molar conductance 97.20 cm2/~. Calcd. for C34H28N6S2PdC12 : C, 53.58; H, 3.67; N, 11.03; S, 8.40; CI, 9.32; Pd, 13.97. Found: C, 54.88, H, 3.91; N, 10.68; S, 8.11; C1, 9.21; Pd, 13.88. 12. Monochloro bis(naphthyl thiourea) mono(2-2',dipyridyl) palladium(II) chloride, [Pd(Ntu)2(2-2',dipy)C1]C1 Lemon yellow crystals, decomp, point 158°C, molar conductance 133'0cm2/f~. Calcd for C32H2aN6S2 Pd C12: C, 52.07; H, 3"8; N, 11.39; S, 8.67; C1, 9.62; Pd, 14.42. Found: C, 50.43; H, 4.03; N, 11"06;S, 8.52; C1, 9-71; Pd, 14-51.
Solubility All the complexes are soluble in ethyl and methyl alcohols but insoluble in other common organic solvents such as benzene, toluene, chloroform and nitrobenzene. The analyses of carbon, hydrogen, nitrogen and chlorine were carried out by the Indian Institute of Technology, Kanpur, India. I.R. spectra were recorded with a Perkin-Elmer infracord model 137 for the range 4000-700 crn -1 using KBr pellets whereas the spectra in the range 700-350 were recorded on a Beckman 11 in KBr. Molar conductance of the complexes was measured in methyl alcohol with a Philips conductivity bridge, model PR 9500 using a dip-type conductivity cell (cell constant 0.76).
RESULTS AND DISCUSSION Like thiourea, naphthyl thiourea has coordinating capacity both through sulphur and nitrogen. The only difference between them is the attachment of the naphthyl group to one nitrogen of the thiourea. Previous studies on the coordination chemistry of thiourea and substituted thioureas with palladium(II) chloride have indicated the presence of metal to sulphur bond[I, 4]. Thus, it will be of interest to compare the manner in which thiourea and naphthyl thiourea coordinate with palladium(II) chloride, because naphthyl is an electron withdrawing group and, therefore, it should be expected to reduce the nucleophilicity of the naphthyl amino nitrogen and so the chances of coordination through this nitrogen become less than for the primary amino group and sulphur which are present in the molecule. Furthermore, it is also important to note that as the nucleophilic nature of such compound decreases the N - H
Penta-coordinate complexes of palladium(II ) chloride
301
deformation and C-N antisymmetric stretching vibra- It is, therefore, evident that a species like [Pd(Ntu)4] 2+ tion frequencies will also decrease and the double bond is not present in such circumstances and the precharacter of C-S will be stronger in the substituted dominant species is [Pd(Ntu)4C1] +. But in a weakly thiourea than thiourea[12, 13]. Therefore, the co- polar medium, acetone, further association of chlorine ordinating capacity of thiourea through sulphur must takes place which leads to the formation of nonbe greater than that of naphthyl thiourea. In conse- conducting species by the loss of one coordinated quence an investigation has been made of the co- naphthyl thiourea molecule provided the coordination ordinating site in the naphthyl thiourea complex of does not exceed five. However, the conductivity palladium(II) chloride and this has also been extended again increases as much as before, i.e. to a value to the mixed ligand complexes formed by subjecting appropriate to a 1:I electrolyte on the addition of naphthyl thiourea-palladium(II) chloride complex to excess naphthyl thiourea, according to the following equilibrium(l) further substitution with heterocyclic amines. Acetone Identification of the coordinating sites in the [Pd(Ntu)4C1]Cl ~ IPd(Ntu)3Cl2] + Ntu. l l) naphthyl thiourea complex and mixed ligand complexes of palladium(II) chloride has been made on the basis The i.r. spectra of palladium(I!) substituted of i.r. spectra studied in the range ca. 4000-350 cm naphthyl thiourea complex, [Pd(Ntu)zLCIICI and using standard KBr technique and conductometric [Pd(Ntu)2L~C1]CI, (where L stands for 2,2'-dipyridyl measurements in methyl alcohol and acetone. and o-phenanthroline, and L' for pyridine, ~, [~ and The N H stretching bands which are present in the 7-picolines, 2-4 and 2-6 lutidines, quinoline, iso31~ region in the spectrum of naphthyl thiourea are quinoline and acridine) were also studied in the range neither shifted to lower frequency nor split on formation 4000 350cm 1. The changes that take place in the of the metal naphthyl thiourea complex. Two bands mixed ligand complexes are obtained by comparing present in pure naphthyl thiourea at ~ 3100 (V S) and the spectra of these complexes with that of the naphthyl 3389 (S) cm ~ appear at the same frequencies with thiourea complex. similar sharpness but with lower intensity on complex Two bands which are present in the naphthyl formation. This suggests that coordination is taking thiourea complex in the 3/~ region change into a place through the sulphur. single band in all the complexes at between 3077 Furthermore, the bands present in naphthyl thiourea 3030cm -1 on further coordination of heterocyclic at ~ 1610 and ~ 1500 cm 1 resulting from the NH2 amines. However, no appreciable changes are recorded bending modes and antisymmetric N- C N stretching in the characteristic aromatic ring vibration appear in vibration frequencies, the former remains almost un- the region 1600 1350cm 1 in most of the heterocyclic affected while the latter is shifted to higher frequency compounds. The naphthyl thiourea complex shows region to the extent of ~ 35 cm- ~on coordination. This four bands in this particular region around 1613 (vs), shift is attributed to the development of double bond 1538(vs), 1414(w)and 1390(s)cm 1, all these bands character of the carbon-to-nitrogen. remain unaffected except one which is shifted to the The band observed at ~ 770 (S) cm ~in the spectrum lower frequency side, 1538-~ 1515cm ~ in all the of the complex corresponds to the 775 cm 1 band of above mixed ligand complexes. Similarly, no major naphthyl-thiourea. This lowering of the C S stretching changes are recorded in the CH in-plane and out of the frequency is indicative of the reduced double bond plane deformation regions. The important band which character of the C = S bond. However, in pure thiourea is attributed to the C = S stretching frequency appearthis band is found at 733 cm-~ and shifts towards the ing at 770cm ~ in the naphthyl thiourea complex lower frequency region to the extent of 30 cm-I on remains unaffected on further substitution of heretocomplex formation[l, 14!. In comparison, it is evident cyclic amines. that the capacity of changing the double bonded It is therefore evident from the i.r. spectra studies character of the carbon sulphur link, C----S, in the that coordination is taking place through the sulphur direction of the value for a single bond, C S, is greater of the naphthyl thiourea and nitrogen of the heteroin thiourea than with naphthyl-thiourea. cyclic amines in the mixed ligand complexes of palThese data indicate the presence of a metal- sulphur ladium(II) chloride. All these complexes have a strong bond and the absence of metal nitrogen bonds in the band at .~357cm 1 which can be assigned to the metal chlorine bond[19]. naphthyl thiourea complex [14]. The number of coordinated halide ions present in all The naphthyl thiourea complex of palladium(II) chloride can be formulated Pd(Ntu)4C12, as is con- the mixed ligand complexes was inferred from the elecfirmed by the elemental analysis for C, H, N, S, CI and trical conductance of the complexes in methyl alcohol Pd. However, it behaves as a five-coordinate species, solution at room temperature (31.5°C). Uni-univalent [Pd(NtuhCll+C1 in non-aqueous solvents, as is electrolytes exhibit molar conductances i~ the range indicated by thc molar conductance tending to the 89.37 1330 cmZ/f~ in this solvent. value for a 1:1 electrolyte in polar solvents, e.g. 96-01 cm 2 f~ in methyl alcohol[15, 16]. It shows an Acknowledgement--The author is thankful to ProL W. appreciable lower conductance, e.g. 15"00cm2/~2 in Rahman, for research facilities and also to Dr. Asif Zaman acetone[17, 183 which is less polar than methanol. for helpful suggestions.
M. MAHFOOZ KHAN
302 REFERENCES
1. A. Yamaguchi, R. B. Penland, S. Mizushima, T. J. Lane, C. Curran and J. V. Quangliano, J. Am. chem. Soc. 80, 527 (1958). 2. T. J. Lane, A. Yamaguchi, T. V. Quagliano, J. A. Ryan and S. Mizushima, J. Am. chem. Soc. 81, 3824 (1959). 3. A. D. Westland, J. chem. Soc, 3060 (1965). 4. M. Schafer and C. Curran, Inorg. Chem. 5, 265 (1966). 5. K. A. Jensen and P. H. Nielsen, Acta chem. scand. 20, 597 (1966). 6. R. J. H. Clark, G. Natile, U. Belluco, L. Cattalini and C. Fillipin, J. chem. Soc. 659 (1970). 7. L. M. Venanzi et al., J. chem. Soc. 2771, 5210, 5521 (1965); Angew. Chem. inter, ed. 3, 453 (1964). 8. N. C. Stephenson, J. inorg, nucl. Chem. 24, 791, 797 (1962); N. C. Stephenson and G. A. Jeffrey, Proc. chem. Soc 173 (1963).
9. R. A. D. Wentworth and C. H. Brubaker, Jr., Inorg. Chem. 3, 1472 (1964). 10. J. Lewis, R. F. Long and C. Oldham, J. chem. Soc. 6740 (1965). 11. C. M. Harris, S. E. Livingstone and I. H. Reece, J. chem. Soc. 1505 (1959). 12. H. O. Pritchard and H. A. Skinner, Chem. Rev. 55, 745 (1955). 13. A. U. Malik, J. inorg, nucl. Chem. 32, 1744 (1970). 14. M. M. Khan, J. inorg, nucl. Chem. 35, 1395 (1973). 15. W. J. Geary, Coord. chem. Rev. 7, 112 (1971). 16. J. R. Hall, R. A. Plowman and H. S. Preston, Aust. J. Chem. 18, 1346 (1965). 17. W. J. Geary, Coord. chem. Rev. 7, 105 (1971). 18. T. J. Huttemann, B. M. Foxman, C. R. Sperati and J. G. Verkade, lnorg. Chem. 4, 950 (1966). 19. M. N. Hughes and K. J. Rutt, J. h~org, nucl. Chem. 33, 924 (1971).
. 19-4. k'td
~,~, p p . 2 9 9
302. P e r g a m o n
Press P r i m e d in G r e a t B r i t a i n .
PENTA-COORDINATE COMPLEXES OF PALLADIUM(II) CHLORIDE WITH SULPHUR (NAPHTHYL THIOUREA) AND NITROGEN (HETEROCYCLIC AMINES) CONTAINING LIGANDS M. MAHFOOZ KHAN Department of Chemistry, Aligarh Muslim University, Aligarh, U.P., India
t Receired 20 S~7~temher 1972) Abstract On the interaction of naphthyl thiourea with palladium(lI) chloride in methanol a pentacoordinate complex, [Pd(Ntu)4CI]CI, was obtained. On further coordination of this species with 2,2'dipyridyl, o-phenanthroline, pyridine, :g/:¢ and y-picolines, 2-4 and 2-6 lutidines, quinoline, isoquinoline and acridine mixed ligand penta-coordinate complexes of the type [Pd(Ntu)~LCI 1C1 and [Pd(Ntul2 L',CI1CI (where L stands for 2,2'-dipyridyl and o-phenanthroline and L' for pyridine, :
INTRODUCTION
lutidine (2-4L), 2-6,1utidine (2-6L), quinoline IQ), isoquinoline (Isoq) and acridine (acrid) were all AnalaR, B.D.H. products and used as such, whereas picolines. lutidines and quinolines were further purified by redistillation. Preparation of naphdTyl thiourea palladium(II ) chhn'ide About 50 ml aqueous solution of 1 per cent palladium(lI) chloride containing a few drops of conc. HCI was added to 100 ml solution of 5 per cent naphthyl thiourea in methyl alcohol. The resulting solution was heated over a water bath for about five minutes and filtered. The filtrate was kept for crystallization and after about three days lemon coloured crystals of the complex appeared. The crystals were separated from the main liquor and recrystallized from acetone. Finally, they were dried in a vacuum desiccator over CaO.
THE ABILI'rYof nitrogen and sulphur containing ligands to form complexes with palladium{II) are well known [1-5]. However, palladium(II) ions are one of the heavier elements which have a pronounced tendency to form square planar complexes[6]. Besides tetra coordinate complexes, there are some penta-coordinate species with trigonal bipyramidal structures which act as 1 : 1 electrolytes in solution[7]. But hexa-coordinate complexes of palladium(lI) are rare and a large number of complexes which were previously considered to be octahedral have later been shown not to be soE8 101. Although there is some evidence for higher coordination by the action of excess halide ion on chelates such as [Pd phen2] 2+ and tetrahalogeno palladates(II)[11]. This paper describes the preparation and properties of penta coordinate complex of palladium(II) chloride with naphthyl thiourea. The complex, [Pd(Ntu)4CI]CI, is further subjected to substitution reaction with some heterocyclic amines resulting in the formation of penta-coordinate mixed ligand species. All the complexes are characterized by elemental analysis, molar conductance values, and the bonding discussed on the basis of i.r. and far i.r. spectra studies.
1. Monochlorotetrakis (naphthyl chloride, [Pd(Ntu)4Cll CI
thiourea)
palladium(If)
Lemon yellow crystals, decomp, point 183°C, molar conductance in methyl alcohol 96"01 cm2,'fl. Calcd for C44H4oN8S4 Pd Cb: C, 53,58: H, 4.06; N, 11.37: S, l"!.98: C1, 7.20; Pd, 10.79. Found: C, 54.20; H, 4.23: N. 11.00: S, 12.88; C1, 7.41; Pd, 10-81. General method for the preparation of mixed ligand complexes from monochlorotetrakis (naphthyl thiourea) palladium(II) chloride. Solutions of naphthyl thiourea complex and heterocyclic amine in methyl alcohol were mixed in 1:5 molar ratio. The solution was filtered and the filtrate was heated on a water bath to complete dryness. To the impure dried compound methanol was again added and heated to complete dryness. After repeating this process at least three or four times,
EXPERIMENTAL
Palladium(I1) chloride (Johnson Matthey and Co.), and naphthyl thiourea (Ntu), o-phenanthroline (o-phen), 2,2'dipyridyl tdipy), :~-picoline (~-pic), fl-picoline (fl-pic), 2-4, 299
300
M. MAHFOOZKHAN
the unreacted ligand was removed by washing the complex several times with small aliquots of acetone, in which the amines were highly soluble, the pure complex being poorly soluble. The purified complex was crystallized from methyl alcohol.
2. Monochloro bis(naphthyl thiourea) bis pyridine palladium(II) chloride, [Pd(Ntu)2(py)2Cl]C1 Brown crystalline substance, decomp, point 138°C, conductance in methyl alcohol 89-37cm2/t). Calcd for Ca2HaoN6S2 Pd C12: C, 51'9; H, 4-05; N, 11'3; S, 8-65; Cl, 9"60; Pd, 14'39. Found: C, 52'83; H, 4"25; N, 10"91; 8"51; C1, 9.52; Pd, 14"60.
3. Monochloro bis(naphthyl thiourea) bis(ct-picoline) paUadium(II) chloride, [Pd(Ntu)2(ct-pic)2C1]Cl Brown crystalline substance, m.p. 134°C, molar conductance 101.20 cm2/~. Calcd for C34Ha4N6S2 Pd C12: C, 53-16; H, 4.19; N, 10.94; S, 8.06; Cl, 9-25; Pd, 13'86. Found: C, 54'50; H, 4.3; N, 10'58; S, 8'25; C1, 9.57; Pd, 13.51.
4. Monochloro bis(naphthyl thiourea) bis(fl-picoline) palladium(II) chloride, [Pd(Ntu)2(fl-pic)2Cl~C1 Brown crystalline substance, molar conductance 99.28 cm2/f~. Calcd for C34H34N652 Pd C12: C, 53.16; H, 4.19; N, 10.94; S, 8"05; Cl, 9.25; Pd, 13.86. Found: 54.18; H, 4.55; N, 10.59; S, 8.23; Cl, 9.18; Pd, 13.59.
5. Monochloro bis(naphthyl thiourea) bis(~-picoline) palladium(II) chloride, [Pd(Ntu)2(7-pic)2C1]C1 Brown crystalline substance, molar conductance 121.8 cm2/f~. Calcd for C34H34N6S2 Pd C12: C, 53.16; H, 4.19; N, 10.94; S, 8.06; Cl, 9.25; Pd, 13"86. Found: C, 54.44; H, 4.39; N, 10.80; S, 8.10; Cl, 9.35; Pd, 13.55.
6. Monochloro bis(naphthyl thiourea) bis(2-4,1utidine) palladium(II) chloride, [Pd(Ntu)z(2-4,L)2Cl] C1 Brown crystalline substance, decomp, point 138° C, molar conductance 110.0cm2/f~. Calcd for C36H3aN6S2 Pd C12: C, 54.32; H, 4.77; N, 10.56; S, 8.04; C1, 8.92; Pd, 13.37. Found: C, 55.80; H, 4.80; N, 10.09; S, 8.10; C1, 8.81; Pd, 13.29.
7. Monochloro bis(naphthyl thiourea) bis(2-6,1utidine) palladium (II) chloride, [Pd(Ntu)z(2-6,L)2CI] CI Brown crystalline substance, molar conductance 110-01 cm2/~. Calcd for C36HaaN6S2 Pd C12: C, 54-32; H, 4.77; N, 10"56; S, 8.04; C1, 8"92; Pd, 13-37. Found: C, 56"01; H, 4.71; N, 10.48; S, 8-11; C1, 8.87; Pd, 13-41.
8. Monochloro bis(naphthyl thiourea) palladium(II) chloride, [Pd(Ntu)2(Q)2C1]CI
bis
quinoline
Black crystalline substance, decomp, point 114°C, molar conductance 90.38 cm2/~. Calcd for C4oH34N6S2 Pd C12: C, 57-17; H, 4.19; N, 10.07; S, 7.62; C1, 8-45; Pd, 12.67. Found: C, 55.01 ; H, 4.20; N, 10.20; S, 7.81 ; Cl, 8.35; Pd, 12.59.
9. Monochloro bis(naphthyl thiourea) bis(isoquinoline) palladium(II) chloride, [Pd(Ntu)2(Isoq)2 C1]C1 Black crystalline substance, m.p. 115°C, molar conductance 91.50 cm2/~. Calcd for C40H34N6S2 Pd CI2: C, 57.17;
H, 4.19; N, 10.07; S, 7.62; CI, 8.45; Pd, 12.67. Found: C, 56.81; H, 3.99; N, 10.24; S, 7.63; C1, 8-38; Pd, 12.72. 10. Monochloro bis(naphthyl thiourea) bis palladium(II) chloride, [Pd(Ntu)2(acrid)2C1]C1
acridine
Brown crystalline substance, m.p. 116°C, molar conductance 121"0cm2/~. Calcd for C48H38N6S2 Pd C12: C, 61'13; H, 4.04; N, 8.94; S, 6.81; C1, 7.55; Pd, 11.32. Found: C, 62.27; H, 4.21; N, 8.71; S, 6'90; CI, 7.44; Pd, 11.46.
11. Monochloro bis(naphthyl thiourea) mono(o-phenanthroline) palladium(II) chloride, [Pd(Ntu)2(o-phen)C1]C1 Orange yellow crystalline substance, m.p. 113°C, molar conductance 97.20 cm2/~. Calcd. for C34H28N6S2PdC12 : C, 53.58; H, 3.67; N, 11.03; S, 8.40; CI, 9.32; Pd, 13.97. Found: C, 54.88, H, 3.91; N, 10.68; S, 8.11; C1, 9.21; Pd, 13.88. 12. Monochloro bis(naphthyl thiourea) mono(2-2',dipyridyl) palladium(II) chloride, [Pd(Ntu)2(2-2',dipy)C1]C1 Lemon yellow crystals, decomp, point 158°C, molar conductance 133'0cm2/f~. Calcd for C32H2aN6S2 Pd C12: C, 52.07; H, 3"8; N, 11.39; S, 8.67; C1, 9.62; Pd, 14.42. Found: C, 50.43; H, 4.03; N, 11"06;S, 8.52; C1, 9-71; Pd, 14-51.
Solubility All the complexes are soluble in ethyl and methyl alcohols but insoluble in other common organic solvents such as benzene, toluene, chloroform and nitrobenzene. The analyses of carbon, hydrogen, nitrogen and chlorine were carried out by the Indian Institute of Technology, Kanpur, India. I.R. spectra were recorded with a Perkin-Elmer infracord model 137 for the range 4000-700 crn -1 using KBr pellets whereas the spectra in the range 700-350 were recorded on a Beckman 11 in KBr. Molar conductance of the complexes was measured in methyl alcohol with a Philips conductivity bridge, model PR 9500 using a dip-type conductivity cell (cell constant 0.76).
RESULTS AND DISCUSSION Like thiourea, naphthyl thiourea has coordinating capacity both through sulphur and nitrogen. The only difference between them is the attachment of the naphthyl group to one nitrogen of the thiourea. Previous studies on the coordination chemistry of thiourea and substituted thioureas with palladium(II) chloride have indicated the presence of metal to sulphur bond[I, 4]. Thus, it will be of interest to compare the manner in which thiourea and naphthyl thiourea coordinate with palladium(II) chloride, because naphthyl is an electron withdrawing group and, therefore, it should be expected to reduce the nucleophilicity of the naphthyl amino nitrogen and so the chances of coordination through this nitrogen become less than for the primary amino group and sulphur which are present in the molecule. Furthermore, it is also important to note that as the nucleophilic nature of such compound decreases the N - H
Penta-coordinate complexes of palladium(II ) chloride
301
deformation and C-N antisymmetric stretching vibra- It is, therefore, evident that a species like [Pd(Ntu)4] 2+ tion frequencies will also decrease and the double bond is not present in such circumstances and the precharacter of C-S will be stronger in the substituted dominant species is [Pd(Ntu)4C1] +. But in a weakly thiourea than thiourea[12, 13]. Therefore, the co- polar medium, acetone, further association of chlorine ordinating capacity of thiourea through sulphur must takes place which leads to the formation of nonbe greater than that of naphthyl thiourea. In conse- conducting species by the loss of one coordinated quence an investigation has been made of the co- naphthyl thiourea molecule provided the coordination ordinating site in the naphthyl thiourea complex of does not exceed five. However, the conductivity palladium(II) chloride and this has also been extended again increases as much as before, i.e. to a value to the mixed ligand complexes formed by subjecting appropriate to a 1:I electrolyte on the addition of naphthyl thiourea-palladium(II) chloride complex to excess naphthyl thiourea, according to the following equilibrium(l) further substitution with heterocyclic amines. Acetone Identification of the coordinating sites in the [Pd(Ntu)4C1]Cl ~ IPd(Ntu)3Cl2] + Ntu. l l) naphthyl thiourea complex and mixed ligand complexes of palladium(II) chloride has been made on the basis The i.r. spectra of palladium(I!) substituted of i.r. spectra studied in the range ca. 4000-350 cm naphthyl thiourea complex, [Pd(Ntu)zLCIICI and using standard KBr technique and conductometric [Pd(Ntu)2L~C1]CI, (where L stands for 2,2'-dipyridyl measurements in methyl alcohol and acetone. and o-phenanthroline, and L' for pyridine, ~, [~ and The N H stretching bands which are present in the 7-picolines, 2-4 and 2-6 lutidines, quinoline, iso31~ region in the spectrum of naphthyl thiourea are quinoline and acridine) were also studied in the range neither shifted to lower frequency nor split on formation 4000 350cm 1. The changes that take place in the of the metal naphthyl thiourea complex. Two bands mixed ligand complexes are obtained by comparing present in pure naphthyl thiourea at ~ 3100 (V S) and the spectra of these complexes with that of the naphthyl 3389 (S) cm ~ appear at the same frequencies with thiourea complex. similar sharpness but with lower intensity on complex Two bands which are present in the naphthyl formation. This suggests that coordination is taking thiourea complex in the 3/~ region change into a place through the sulphur. single band in all the complexes at between 3077 Furthermore, the bands present in naphthyl thiourea 3030cm -1 on further coordination of heterocyclic at ~ 1610 and ~ 1500 cm 1 resulting from the NH2 amines. However, no appreciable changes are recorded bending modes and antisymmetric N- C N stretching in the characteristic aromatic ring vibration appear in vibration frequencies, the former remains almost un- the region 1600 1350cm 1 in most of the heterocyclic affected while the latter is shifted to higher frequency compounds. The naphthyl thiourea complex shows region to the extent of ~ 35 cm- ~on coordination. This four bands in this particular region around 1613 (vs), shift is attributed to the development of double bond 1538(vs), 1414(w)and 1390(s)cm 1, all these bands character of the carbon-to-nitrogen. remain unaffected except one which is shifted to the The band observed at ~ 770 (S) cm ~in the spectrum lower frequency side, 1538-~ 1515cm ~ in all the of the complex corresponds to the 775 cm 1 band of above mixed ligand complexes. Similarly, no major naphthyl-thiourea. This lowering of the C S stretching changes are recorded in the CH in-plane and out of the frequency is indicative of the reduced double bond plane deformation regions. The important band which character of the C = S bond. However, in pure thiourea is attributed to the C = S stretching frequency appearthis band is found at 733 cm-~ and shifts towards the ing at 770cm ~ in the naphthyl thiourea complex lower frequency region to the extent of 30 cm-I on remains unaffected on further substitution of heretocomplex formation[l, 14!. In comparison, it is evident cyclic amines. that the capacity of changing the double bonded It is therefore evident from the i.r. spectra studies character of the carbon sulphur link, C----S, in the that coordination is taking place through the sulphur direction of the value for a single bond, C S, is greater of the naphthyl thiourea and nitrogen of the heteroin thiourea than with naphthyl-thiourea. cyclic amines in the mixed ligand complexes of palThese data indicate the presence of a metal- sulphur ladium(II) chloride. All these complexes have a strong bond and the absence of metal nitrogen bonds in the band at .~357cm 1 which can be assigned to the metal chlorine bond[19]. naphthyl thiourea complex [14]. The number of coordinated halide ions present in all The naphthyl thiourea complex of palladium(II) chloride can be formulated Pd(Ntu)4C12, as is con- the mixed ligand complexes was inferred from the elecfirmed by the elemental analysis for C, H, N, S, CI and trical conductance of the complexes in methyl alcohol Pd. However, it behaves as a five-coordinate species, solution at room temperature (31.5°C). Uni-univalent [Pd(NtuhCll+C1 in non-aqueous solvents, as is electrolytes exhibit molar conductances i~ the range indicated by thc molar conductance tending to the 89.37 1330 cmZ/f~ in this solvent. value for a 1:1 electrolyte in polar solvents, e.g. 96-01 cm 2 f~ in methyl alcohol[15, 16]. It shows an Acknowledgement--The author is thankful to ProL W. appreciable lower conductance, e.g. 15"00cm2/~2 in Rahman, for research facilities and also to Dr. Asif Zaman acetone[17, 183 which is less polar than methanol. for helpful suggestions.
M. MAHFOOZ KHAN
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