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Department of Inorganic Chemistry, Faculty of Sciences. University of Granada ... compared to those of free HDATP and of 4, 6-diamine-2- methylthiopyrimidine ...
Transition Met. Chem., 13, 451-454 (1988)

Thiopyrimidine Co r~, Co m, Ni H and Cu ~ complexes

451

Study of the complex formation between 4, 6-diamine-1, 2-dihydro-2-thiopyrimidine and cobalt(II), cobalt(Ill), nickel(II) and copper(II) ions Maria Do Gutierrez-Valero, Maria A. Romero-Molina*, Rafael L6pez-Garz6n and Juan M. Salas-Peregrin

Department of Inorganic Chemistry, Faculty of Sciences. University of Granada, 18071 Granada. Spain Summary Reactions of 4, 6-diamine-1, 2-dihydro-2-thiopyrimidine (HDATP) with cobalt(II), nickel(II) and copper(II) ions in 1:2 metal:tigand ratio in aqueous media at 25~ and 0.1 M ionic strength (KNO3), lead to the formation of both [M(DATP)] + and [M(DATP)2] species, whose stability constants were obtained. On the other hand, in aqueous or ethanolic media, solid complexes with 1:1, 1:2, or 1:3 stoichiometries were isolated. These have been characterized by analytical, i.r. and electronic spectral and magnetic measurement studies, and tentative structures are proposed.

Introduction The stimulus for much of the research into the coordination chemistry of heterocyclic thione donors stems from their wide-ranging applications (1). Among these types of compound, pyrimidine 2-thione derivatives are known for their biological and pharmaceutical importance(2-a). Thus, 2-thiouracil, 4-thiouracil, and 2-thiocytosine are normal constituents of some t-RNA species (*-~) although their functions are not well understood. Complexes of pyrimidine-2-thiones have been reported with a number of metals (~'6-~3) and several structures have been solved by x-ray diffraction methods (I). We have described the preparation and characterization of several metal complexes of pyrimidine-2-thione derivatives and 2-thiopurine derivatives(~'~-z4). As a continuation to this work, the synthesis and characterization of several cobalt(II), cobalt(III), nickel(II) and copper(II) complexes of the 4, 6-diamine-1, 2-dihydro-2-thiopyrimidine (HDATP, scheme 1) are described here.

H~N~r/~H HDATP

Results and discussion The stability constants obtained by application of Bjerrum's method to potentiometric titration curves of solutions containing cobalt(II), nickel(II) and copper(II) and HDATP are indicated in Table 1. These values are consistent with those obtained for other metal-pyrimidine complexes(2~), being in accordance with the Irving-Williams rule (25).

* Author to whomall correspondenceshouldbe directed. 0340-4285/88 $03.00+ .12

The elemental analyses and colours of the solid complexes are shown in Table 2. Under the experimental conditions, 3:1, 2:1 and I: 1 complexes are formed. The i.r. spectral data of the isolated complexes, when compared to those of free HDATP and of 4, 6-diamine-2methylthiopyrimidine (DAMTP) 126) indicate the donor atoms of the ligand, the mode of bonding of the counter ion and the presence in the solids of water molecules. These data are summarized in Table 3. HDATP and the complexes containing water all show in their i.r. spectra one broad band in the 3450-3460 cmregion which is characteristic of v(OH). Coordinated water is also indicated by the metal-sensitiYe bands attributable to wagging modes in the range 560530 cm - t(z~). Bands corresponding to c~(H--O--H) and v(Co--O)aqu, modes of coordinated water are presumably masked by the ligand absorptions.

Complexes with DATP as ligand In those complexes with the monoanionic ligand DATP, bands corresponding to 6(N--H) and v(C~---S) are not present. In its monoanionic form, the negative charge of the ligand is located on the sulphur atom and, therefore, the i.r. spectra of these complexes show the same vibration modes as the molecule DAMTp(26L This may be due to the change in the C = S bond upon coordination of DATP through the sulphur atom; the formation of an S - - M bond is expected to increase the singlebond character of the carbon-sulphur bond; consequently, the contribution of the - - N = C - - S - structure increases and a significant frequency change is observed in the bands assigned to C = C , C = N , C - - N and NCS vibrational modes. The presence in the far i.r. spectra, of two new bands assignable to v(M--N) and v(M--S) vibration modes, is in accordance with N, S chelation through the nonprotonated ring nitrogen atom and the exocyclic sulphur atom. The solution electronic spectra of HDATP, DATPand their complexes exhibit the bands shown in Table 4. The magnetic moment and electronic spectrum of [Co(DATP)3]'H20 is typical of a low-spin octahedral species showing two main absorption bands at 21300 and 15400cm -1, which are assigned to the tAlo--~ lr2g and Table L Stability constants for CoI~, Nin, and Cun complexes with HDATP at 25~C and 0.1 M KNO~ ionic strength. System

KI(1 x tool -I)

K2(1 x mo1-1)

Con/HDATP Nin/HDATP Cu~I/HDATP

9.8 x 104 1.7 x 105 7.4 x 108

7.9 x 104 6.2 x 104 5.0 x 10v

9 1988 Chapmanand Hall Ltd

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M . D . G u t i e r r e z - V a l e r o et at.

Transition Met. Chem., 13, 4 5 t - 4 5 4 (1988)

Table 2. Colour and analytical data of the isolated complexes. Compound

Colour

[-Co(DATP) 3] ' H 2 0

Brown

[Co(HDATP)2(H20)/] (N03) 2

Pink

[Co(HDATP)(H20)2] (NO3)2

Violet

[Ni(DATP)2]

Yellow

[Ni(HDATP)z(NO3)2]

Yellow

[Cu(DATP)2]

Light brown

F o u n d (Calcd)~o C H

N

S

M

28,7 (28.8) 19.0 (19.1) 13.8 (13.3) 28.1 (28.2) 20.6 (20.6) 28.1 (27.8)

33.0 (33.6) 27.6 (27.8) 22.8 (23.3) 32.4 (32.9) 29.4 (30.0) 32.5 (32.4)

-

11.5 (11.8) 12.8 (11.7)

3.40 (3.4) 3.20 (3.2) 3.15 (2.8) 2.60 (2.9) 2.50 (2.6) 2.90 (2.9)

-

15.8

-

(16.3) 18.0 (17,2) 12.5 (12.6) (18.4)

18.5 (18.8) 12.6 (13.7) -

Table 3. I.r. bands (cm- 1) of H D A T P and its complexes. Compound

v(O--H)

v(NH)

6(NH)

v(C=C) + v ( C z N )

v(C=N) + v ( N - - C ~ S )

HDATP. 1/2H20 [Co(DATP)3-H20 [Co(HDATP)2(H20)2] (NO3) 2 [Co(HDATP)(H20)2] (NOa) z [Ni(DATP)2 ] [Ni(HDATP)2(NO3)2] [Cu(DATP)2]

3460 3440 3450 3455 -

3410-3270 3180 3390-3100 3390-3100 3409-3083 3460-3100 3470-3000

1635 1620 1640 1640 1656 1678 1625

1615, 1565 1570, 1530, 1460 1625 1625 1606, 1581, 1550, 1440 1640, 1570, 1540 1600, 1570

Compound

v(N--C~S)

6(N1--H)

v(ONO)

v(CN) + v(NCS) + v(CS)

v(M--OH2)

HDATP.1/2H20 [Co(DATP)3].HzO [Co(HDATP)z(H20)z](NO3)z [Co(HDATP)(H20)2](NO3) 2 [Ni(DATP)e] [Ni(HDATP)2(NO3)2] [Cu(DATP)2 ]

1510" 1540 -

1420 1420 1420 1420 -

1380 1380 1382 -

1315, 1240, 1195b 1315, 1275, 1245 1330, 1265, 1230 1330, 1265, 1230 1327, 1272, 1235 1315, 1256 1330, 1280, 1240

. 555 534 -

1535 1530 -

.

v(MN) .

v(MO)

v(MS)

250 -

372 205 182 195 180 221

. 305 312 312 311

a)Thioamide I; b)Thioamide III. Table 4, Electronic spectra of the ligand and its isolated complexes. Compound

Solvent

HDATP NaDATP [Co(DATP)3~ " H 2 0

H20 HzO H20

[Co(HDATP)2 (H20)2] (NO3)2

DMSO EtOH EtOH

[Co(HDATP)(H20)2] (NO3)2

EtOH DMSO EtOH

[Ni(DATP)2]

DMSO DMSO

[Ni(HDATP)2(NO3)2]

H20 DMSO

[Cu(DATP) 2]

H~O

2,,,~ (cm- 1)

Assignment

40984, 38168, 34364 37037 37736 21300 15400 42553, 37037, 34364 22990 19011 18083 42553, 37037, 34364 23256 19231 18518 17860, 15380 33003 36900 38760 41152, 37453, 34483 25000 14490 12990 37037

7z~ r~* ~ ~ n* ~ ~Tr*

IAlg ~ ITzg 1Alg ~ i Tlg rc ~ re* Charge transfer 1T10 ~ 4Tlg(p ) 4 T1 o(F) -74A 20 7r ~ z* Charge transfer 4Tto ~ 4 Tlg(P) r ~(F) ~ 4A2g 3TI(F) --+ 3 TI(P)

rc --r ~z*

aA2q~ 3Teg(P) 3A2g ~ 3 T4g(F)

3A2g~ leg ~z~ 7z*

Transition Met. Chem., 13, 451-454 (1988)

Thiopyrimidine Co H, Co Ill, Ni n and Cu ll complexes

~Alg-~ aTlg transitions. Octahedral ligand field parameters Dq = 1607 cm- 1 and fl = 0.53 are consistent with a moderate ligand-field strength. The [Ni(DATP)21 complex has a magnetic moment of 3.61/zB which is in accordance with the spin-only values for regular tetrahedral complexes (3.5-4.2B.M.). Its electronic absorption spectrum comprises a broad multiple band in the visible region, with two main maxima at 15380 and 17860 cm- 1, assignable to the 3T1(F) ~ 3T1(p) transition; this splitting can be justified by a spin-orbit coupling, which lifts the degenerancy of the 37"1(P) state. On the other hand, the green colour of the complex is attributable to a charge-transfer absorption tailing into the visible region from the ultraviolet. This has also been observed in other tetrahedral nickel complexes containing chloride and bromide ions (2st. The solution spectrum of [Cu(DATP)2] could not obtained due to the insolubility of the complex in common solvents. The magnetic moment value is 1.25/zs; the quenching of the expected spin-only moment can be attributed to antiferromagnetic interactions(29'3~

Complexes with HDA TP as ligand Three new complexes of simplified formulae [Co(HDATP)2(H20)/] (NO3)2, [Co(HDATP)(H20)2] (NO3) 2 and [Ni(HDATP)z(NO3)2] have been isolated. The i.r. spectra of these complexes show the same bands as the i.r. spectrum of the free HDATP, besides a new band about 1380 cm- i (see Table 3). In i.r. spectra of all three complexes the thioamide I band undergoes a shift to higher frequency which is indicative of nitrogen donation(~k A similar displacement occurs in the position of the v(CzS) bands which may be due to sulphur donation. Analogous shifts have been observed in the complex [Cd(HDATP)C12].H20, where HDATP acts as S, N-chelate (17). This coordination mode is also supported by low-•quency i.r. spectral data, which include bands due to v(M--N) and v(M--S) (see Table 3). The magnetic moments of [Co(HDATP)a(H20)2 ] (NO3) 2 and [Co(HDATP)(HaO)z ] (NO3) 2 are 4.66 and 4.72/~s, respectively. These values are in the upper portion of the range observed for tetrahedral Co n complexes and in the lower region of experimental values obtained for octahedral Co ~ complexes(3t). The magnetic moment of the molecular nickel(II) complex is 3.24/as, in the expected range for nickel(II) octahedral complexes. The electronic absorption bands of the Co II and Ni n complexes having HDATP as ligand are shown in Table 4. The values for octahedral ligand field parameters are Dq = 919 cm- 1 and fl --- 0.79 ([Co(HDATP)2(HzO)2 ] (NO3)2) and Dq = 940cm- 1 and fl = 0.80 ([Ni(HDATP)2 (NO3)2]). These values indicate a moderate ligand-field strength. In the case of [Ni(HDATP)2(NO3)2] , the tentative assignment of a band to v(Ni--O) of nitrate groups was done on the basis of combined TG and i.r. studies; the i.r. bands corresponding to v(ONO) and v(Ni--O) disappear when a sample of the solid complex is heated to 300 ~C, which is indicative of the elimination of coordinated nitrate groups.

Experimental The HDATP was prepared by a previously reported method (32). The complexes were prepared as follows.

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[Co(DATP)3]'H20, [Ni(DATP)2], and [Cu(DATP)2] HDATP (2 retool) was dissolved in the minimum amount of H20 (or a 50~ H 2 0 - - N H 4 O H mixture for the copper complex). To this solution the corresponding metallic salt [Co(NO3)2, Ni(NO3)z or CuSO4] was added to reach a metal-ligand molar ratio 1/1 or 3/1 (nickel(II) complex). The resulting solutions were kept under stirring at 40 ~C. A precipitate appeared immediately in the case of copper(II) complex, and after reducing the initial volumen down to the middle in the case of cobalt(II) complex. The nickel(II) complex is precipitated immediately after the pH of the solution reached the 6.5 value by slowly adding a previously prepared 0.1N NaOH solution. All the above reported complexes were filtered, thoroughly washed with H20 and EtOH and dried in an evacuated dessicator over P20 5.

[Co(HDATP)2(H20)2](NOa)2,[Co(HDATP )(H 20)2 ] (NO3) 2 and [Ni(HDA TP)2 (NO 3)2] A solution containing HDATP (2 mmol) in the minimum amount of anhydrous EtOH was stirred at 40 ~C for 2 h. To this solution the corresponding metal nitrate was added until a 1/1 metal-ligand molar ratio was reached. Precipitation occurs after complete addition of the salt to the hot solution, in all cases. The complexes were filtered, washed with cold H20 and EtOH and dried in an evacuated dessicator over P20 5. C, H, and N were analyzed in the Instituto de Quimica Bioorg/mica (C.S.I.C) (Barcelona). Cobalt was determined by complexometric titration with EDTA after destruction of the complexes with aqua regia. Nickel was determined gravimetrically using dimethylglyoxime. The percentage of H20 in the hydrated complexes was determined from t.g. curves. Electronic spectra were recorded in a Bausch and Lomb Spectronic 2000 spectrophotometer from dimethyl sulphoxide (DMSO), HzO or EtOH solutions. Lr. spectra were obtained from the solids in KBr pellets (4000250 cm- t) and polyethylene pellets (600-180 cm- 1) with a Perkin-Elmer 983 G spectrophotometer. Magnetic susceptibilities at room temperature were determined with Bruker B-E15 Faraday balance. Hg[Co(NCS),] was used as standard and susceptibility values were corrected for diamagnetism using the Pascal constants (33). Thermogravimetric studies were made under a dynamic air atmosphere (100 cm3/min- 1) in a Mettler TG50 thermobalance at a heating rate of 10degmin -1, whereas DSC runs were carried out on a Mettler DSC-20 differential scanning calorimeter, in the 35-600~ temperature range at a heating rate of 10degmin -1. The potentiometric titration curves of solutions containing Co Ix,Ni II or CuII and HDATP in a 1/2 molar ratio, at 25 ~C and 0.1 M ionic strength (KNO3) , were recorded using a Radiometer TTT-60 titrator fitted with glass and calomel electrodes. The stability constant values were obtained by application of Bjerrum's method (34).

Referenees mE. S. Raper Coord. Chem. Rev., 61, 115 (1985) and refs. therein. (2JR. E. Handschumacher and A.D. Welch, The Nucleic Acids, Academic Press, New York, 1960, Vol. 3 p. 453.

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M . D . Gutierrez Valero et al.

~3)G. T. Martin, Biological Antagonism, Blakiston, New York 1951. (4)j. A. Carbon, L. Hung and D. S. Jones, Proc. Nat. Acad. Sci. USA, 53, 979 (1965). (5)j. A. Carbon, H. David and M. H. Studier, Science, 161, 1146 (1968). (6)B. A. Cartwright, D.M.L. Goodgame, I. Jeeves, P.O. Langguth and A. C. Skapski, Inor9. Chim. Acta, 24, L45 (1977). (71D. M. L. Goodgame and G. A. Leach, Inor#. Chim. Acta, 25, L127 (1977). (s)D. M. L. Goodgame and G. A. Leach, J. Chem. Sot., Dalton Trans., 1705 (1978). (9)D. M. L. Goodgame, I. Jeeves and G. A. Leach, Inor9. Chim. Aeta, 39, 247 (1980). ~I~ Goodgame and K. W. Jhons, tnory. Chim. Acta, 55, 15 (1981). (~1)R. Battistuzzi and G. Peyronel, Spectrochim. Acta, 36A, 113 (1980). (12)R. Battistuzzi and G. Peyronel, Z. Anory. Ally. Chem., 509, 192 (1984). (13)R. Battistuzzi, Polyhedron, 4, 933 (1985). (14)C. Valenzuela-Calahorro, J. D. L6pez-Gonz/dez, R. L6pezGarz6n and M. Melgarejo-Sampedro, An. Quire., 79B, 143 (1981). ~ls)C. Valenzuela-Calahorro, J.D. L6pez Gonzalez and R. L6pez-Garz6n, An. Qulm., 78B, 184 (1982); 1bid., 79B, 467 (1983). ~16)j. M. Salas-Peregrin, M.A. Romero-Molina, E. ColacioRodriguez and R. L6pez-Garz6n, An. Quire., 80B, 465 (1984). (171M. Moreno-Carretero, A. Martinez-Garz6n, R. L6pezGarz6n and J. M. Salas-Peregrin, Rev. Chim. Min., 22, 369 (t985). ~lS)A. Martinez-Garz6n, R. L6pez-Garz6n and M. MorenoCarretero, Thermochim Acta, 80, 143 (1984). (19)11. L6pez-Garz6n, A. Martinez-Garz6n, M.D. GutierrezValero and M. Domingo-Garcia, Thermochim. Acta, 108, 181 (1986).

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(Received 8 February 1988)

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