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New thiourea complexes of cobalt(II) and nickel(II) nitrates
Notes
1973
ever, this apparent anomaly can be explained on the basis of the proposed protonation mechanism to the extent that ethylenebisbiguanidepalladium(lI) ion might be more easily protonated than is the ethylenebisbiguanidenickel(II) ion. Because a palladium atom is larger than a nickel atom (covalent atomic radii[2]: Ni, 1.15 A; Pd, 1-28 A) the palladium(ll) complex of ethylenebisbiguanide will be larger than the corresponding nickel(ll) complex and therefore should be able to accept more readily the added ionic charge which it must acquire upon protonation.
Department of Chemistry University of Nevada Reno, Nevada 89507
D.J. M A C D O N A L D
2. R.T. Sanderson, Inorganic Chemistry p. 74. Reinhold, New York (1967).
J. inorg, nucl. Chem,, 1968, Vol. 30, pp. 1973 to 1974.
Pergamon Press,
Printed in Great Britain
New thiourea complexes of cobait(II) and nickel(lI) nitrates (Received 23 October 1967) THERE has been a growing interest, recently, in the chemistry of Co(II) and Ni(ll) complexes with thiourea and N-substituted thioureas ligands[l-6]. It was found that the stereochemistry of these complexes is determined by the simultaneous action of electronic, steric, ligand field and crystal packing effects. We wish to report here some unexpected results obtained during an investigation of the thiourea(TU) derivatives of Co(II) and Ni(I I) nitrates. We have found that the complex Co(TU)4(NO3)2 can exist at room temperature both as a bluegreen stable form and also as a dark green unstable modification. The dark green form can be isolated by addition of cold chloroform to an ethanol solution containing stoichiometric quantities of COOI) nitrate and thiourea. The i.r. [7] and electronic spectral data[ 1] for the solid complex suggest that this form can be correctly formulated as [Co(TU)a] (NO3)~ involvfng the tetrahedral tetrakisthiourea cobalt(lI) cation. This complex reverts on standing at room temperature to the stable green-blue form, which was previously isolated by Cotton et al.[1] from an ethyl acetate solution. They suggested that this complex has the formula[Co(TU)4(NO3)~] with co-ordinated nitrato groups. The convertion can be followed by the changes in the out-of-plane deformation and symmetric stretching frequencies of the ionic nitrato group, due to concomitant lowering of symmetry of the anion in passing from [Co(TU)4] (NOa)2 to [Co(TU)4(NO3)2][7]. Thus, the out-of-plane deformation band shifts from 8 3 4 c m - ' to 819 cm-', whereas the symmetric stretching vibration becomes active in the i.r. at 1045 cm 1. The nature of the reaction product is apparently determined by the magnitude of the solvation energy of the nitrate ion. It is reasonable to assume that the interaction between the nitrate ion and the molecules of solvent is appreciably greater in ethanol than in ethyl acetate. On the other hand, no
1. 2. 3. 4. 5. 6. 7.
F. A. Cotton, O. D. Faut and J. T. Mague, Inorg. Chem. 3, 17 (1964). R. L. Carlin and S. L. Holt, lnorg. Chem. 2, 849 (1963). S. L. Holt and R. L. Carlin, J.Am. chem.Soc. 86, 3017 (1964). G. Yagupsky, R. H. Negrotti and R. Levitus, J. inogr.Nucl. Chem. 27, 2603 (1965). G. Yagupsky and R. Levitus, lnorg.Chem. 4, 1589 (1965). G. Yagupsky and R. Levitus,J.inorg.nucI.Chem. 27, 263 (1965). B. M. Gatehouse, S. E. Livingstone and R. S. Nyholm,J.chem.Soc. 4222 (1957).
1974
Notes
evidence of the formation of the species [Co(TUh(NOa)2] was obtained from conductivity and spectral studies in ethanol, acetone and ethyl acetate. Hence, there appear to be predominant solid state effects in stabilizing the six co-ordinated arrangement in this complex. The reaction between Ni(II) nitrate and excess of thiourea in various polar organic leads to the formation of the light green octahedral complex [Ni(TU)d (NOa)2 [3]. However, using a 1 : 2 mole ratio a red-brown hygroscopic complex of formula Ni(TU)2(NOa)2 can be obtained. The diffuse reflectance spectrum of the solid is clearly indicative of distorted octahedral co-ordination of the Ni(II) ion[8] (As ~ 9000 cm-1). Its i.r. spectrum, on the other hand, shows the typical bands of coordinated nitrate groups[7] (NO str.: 1040cm -1, out-of-plane deform.: 815cm -1, sym. NO2 str.: 1290 cm-l). Unfortunately, the i.r. data does not permit to decide whether the complex involves unior bidentate nitrate groups. However, it is significant that the thioamide B and F bands [9], found at 1473 and 727 cm -~ in free thiourea, occur in this complex at appreciably higher and lower frequencies, respectively, than in other Ni(II) thiourea complexes containing unidentate thiourea groups (Table 1).
Table 1 Compound
[Ni(TU)~(NO3)2]n [Ni(TU)z(NCS)2] n? [Ni(TU)6](NOa)~t [Ni(TU)e]I2:~ [Ni(TU)4CI2]~: THIOUREA
B band* (cm -1)
F band* (cm -1)
1532 1518 1500 1490 1488 1473
690 717 697 717 718 727
*The thioamide B band originates chiefly from the N-C-N antysymmetric stretching motion. The F band is absent in the spectra of tetrasubstituted thioureas and it has been assumed that the main contribution to this hand is a torsional NH vibration (Ref. [9]). ?See Ref. [4]. ¢See Ref.[11].
We tentatively suggest that this fact can be accounted for by assuming the existence of bridging thiourea groups[4] similar to those found in the polymeric pseudo-octahedral complexes[M(TU)2 (NCS)z]n[10]. (M = Ni(II), Co(II), Mn(II), Cd(II)).
Universidad T~cnica del Estado Laboratorio Central de Quimica Santiago, Chile
S I L V A N A BASSO RUBEN LEVITUS
8. C.J. Ballhausen, Introduction to Ligand Field Theory. McGraw-Hill, New York (1962). 9. K. Jensen and P. H. Nieisen, Acta. chem. scand. 20, 597 (1966). 10. M. Nardelli, G. Fava Gasparri, G. Gilardi Battistini and P. Domiano, Acta crystallogr. 20, 349 (1966). 11. R.W. OlliffJ. chem. Soc. 2036 (1965).
1973
ever, this apparent anomaly can be explained on the basis of the proposed protonation mechanism to the extent that ethylenebisbiguanidepalladium(lI) ion might be more easily protonated than is the ethylenebisbiguanidenickel(II) ion. Because a palladium atom is larger than a nickel atom (covalent atomic radii[2]: Ni, 1.15 A; Pd, 1-28 A) the palladium(ll) complex of ethylenebisbiguanide will be larger than the corresponding nickel(ll) complex and therefore should be able to accept more readily the added ionic charge which it must acquire upon protonation.
Department of Chemistry University of Nevada Reno, Nevada 89507
D.J. M A C D O N A L D
2. R.T. Sanderson, Inorganic Chemistry p. 74. Reinhold, New York (1967).
J. inorg, nucl. Chem,, 1968, Vol. 30, pp. 1973 to 1974.
Pergamon Press,
Printed in Great Britain
New thiourea complexes of cobait(II) and nickel(lI) nitrates (Received 23 October 1967) THERE has been a growing interest, recently, in the chemistry of Co(II) and Ni(ll) complexes with thiourea and N-substituted thioureas ligands[l-6]. It was found that the stereochemistry of these complexes is determined by the simultaneous action of electronic, steric, ligand field and crystal packing effects. We wish to report here some unexpected results obtained during an investigation of the thiourea(TU) derivatives of Co(II) and Ni(I I) nitrates. We have found that the complex Co(TU)4(NO3)2 can exist at room temperature both as a bluegreen stable form and also as a dark green unstable modification. The dark green form can be isolated by addition of cold chloroform to an ethanol solution containing stoichiometric quantities of COOI) nitrate and thiourea. The i.r. [7] and electronic spectral data[ 1] for the solid complex suggest that this form can be correctly formulated as [Co(TU)a] (NO3)~ involvfng the tetrahedral tetrakisthiourea cobalt(lI) cation. This complex reverts on standing at room temperature to the stable green-blue form, which was previously isolated by Cotton et al.[1] from an ethyl acetate solution. They suggested that this complex has the formula[Co(TU)4(NO3)~] with co-ordinated nitrato groups. The convertion can be followed by the changes in the out-of-plane deformation and symmetric stretching frequencies of the ionic nitrato group, due to concomitant lowering of symmetry of the anion in passing from [Co(TU)4] (NOa)2 to [Co(TU)4(NO3)2][7]. Thus, the out-of-plane deformation band shifts from 8 3 4 c m - ' to 819 cm-', whereas the symmetric stretching vibration becomes active in the i.r. at 1045 cm 1. The nature of the reaction product is apparently determined by the magnitude of the solvation energy of the nitrate ion. It is reasonable to assume that the interaction between the nitrate ion and the molecules of solvent is appreciably greater in ethanol than in ethyl acetate. On the other hand, no
1. 2. 3. 4. 5. 6. 7.
F. A. Cotton, O. D. Faut and J. T. Mague, Inorg. Chem. 3, 17 (1964). R. L. Carlin and S. L. Holt, lnorg. Chem. 2, 849 (1963). S. L. Holt and R. L. Carlin, J.Am. chem.Soc. 86, 3017 (1964). G. Yagupsky, R. H. Negrotti and R. Levitus, J. inogr.Nucl. Chem. 27, 2603 (1965). G. Yagupsky and R. Levitus, lnorg.Chem. 4, 1589 (1965). G. Yagupsky and R. Levitus,J.inorg.nucI.Chem. 27, 263 (1965). B. M. Gatehouse, S. E. Livingstone and R. S. Nyholm,J.chem.Soc. 4222 (1957).
1974
Notes
evidence of the formation of the species [Co(TUh(NOa)2] was obtained from conductivity and spectral studies in ethanol, acetone and ethyl acetate. Hence, there appear to be predominant solid state effects in stabilizing the six co-ordinated arrangement in this complex. The reaction between Ni(II) nitrate and excess of thiourea in various polar organic leads to the formation of the light green octahedral complex [Ni(TU)d (NOa)2 [3]. However, using a 1 : 2 mole ratio a red-brown hygroscopic complex of formula Ni(TU)2(NOa)2 can be obtained. The diffuse reflectance spectrum of the solid is clearly indicative of distorted octahedral co-ordination of the Ni(II) ion[8] (As ~ 9000 cm-1). Its i.r. spectrum, on the other hand, shows the typical bands of coordinated nitrate groups[7] (NO str.: 1040cm -1, out-of-plane deform.: 815cm -1, sym. NO2 str.: 1290 cm-l). Unfortunately, the i.r. data does not permit to decide whether the complex involves unior bidentate nitrate groups. However, it is significant that the thioamide B and F bands [9], found at 1473 and 727 cm -~ in free thiourea, occur in this complex at appreciably higher and lower frequencies, respectively, than in other Ni(II) thiourea complexes containing unidentate thiourea groups (Table 1).
Table 1 Compound
[Ni(TU)~(NO3)2]n [Ni(TU)z(NCS)2] n? [Ni(TU)6](NOa)~t [Ni(TU)e]I2:~ [Ni(TU)4CI2]~: THIOUREA
B band* (cm -1)
F band* (cm -1)
1532 1518 1500 1490 1488 1473
690 717 697 717 718 727
*The thioamide B band originates chiefly from the N-C-N antysymmetric stretching motion. The F band is absent in the spectra of tetrasubstituted thioureas and it has been assumed that the main contribution to this hand is a torsional NH vibration (Ref. [9]). ?See Ref. [4]. ¢See Ref.[11].
We tentatively suggest that this fact can be accounted for by assuming the existence of bridging thiourea groups[4] similar to those found in the polymeric pseudo-octahedral complexes[M(TU)2 (NCS)z]n[10]. (M = Ni(II), Co(II), Mn(II), Cd(II)).
Universidad T~cnica del Estado Laboratorio Central de Quimica Santiago, Chile
S I L V A N A BASSO RUBEN LEVITUS
8. C.J. Ballhausen, Introduction to Ligand Field Theory. McGraw-Hill, New York (1962). 9. K. Jensen and P. H. Nieisen, Acta. chem. scand. 20, 597 (1966). 10. M. Nardelli, G. Fava Gasparri, G. Gilardi Battistini and P. Domiano, Acta crystallogr. 20, 349 (1966). 11. R.W. OlliffJ. chem. Soc. 2036 (1965).