- Email: [email protected]
A novel Cu(II)-5′-adenylic acid complex
1388
Notes
L inorg,nacl.Chem.Vol.41,pp. 1388-1390 © PergamonPressLtd., 1979. Printedin GreatBritain
0022-1902/79/0901-13881502.00/0
A novel Cu(II)-5'-adenylic acid complex (Received 30 November 1978; received [or publication 2 February 1979)
In an effort to systematically elucidate the chemical properties of copper (ll) coordination compounds with nucleic acid constituents, we recently reported the bonding, and electronic and magnetic properties of a copper(ll)-nucleotide complex of 5'guanylic acid, 5'-GMP [1]. The study of metal complexation with nucleotides is especially relevant since these compounds constitute the monomer units of DNA and RNA and since transition metal complexes containing nucleotides might serve as models for elucidating the role played by various transition metal ions like copper(I1) in both the reversible unwinding and the replication and transcription processes of DNA [2]. In spite of the current interest in transition metal-nucleic acid complexes [3], no reports of any coordination compound with 5'-adenylic acid (Y-AMP), Fig. 1, and copper(lI) have appeared to date. In this paper we wish to report the synthesis, and electronic and magnetic properties of the first copper(II) coordination compound with 5'-AMP.
EXPERIMENTAL Measurements. The electron paramagnetic resonance (EPR) spectra were obtained on a Varian HFE-12 spectrometer at room and liquid nitrogen (77°K) temperatures using X-band frequencies, the variable temperature bulk magnetic susceptibility measurements (12-300°K) in a Faraday balance setup previously described [4], the electronic spectra (8-25 kK) as Nujol mulls in a Beckman DK-2A spectrometer, and the IR spectra (0.66-4.0 kK) as KBr pellets in a Perkin-EImer Model 21 spectrometer. All measurements were made with polycrystalline samples; IR spectra run as pellets and mulls (Nujol and fluorolube) were comparable. Preparation of Cu(5'-AMP).8/3H20. A solution of 0.5 mmole of Cu(NO3)2'3I'[20 in 5 ml of distilled water was added with constant stirring to a neutral solution of Y-AMP, prepared by addition of 0.3395 g (I mmole) of ligand to 40 ml of distilled water at 55°C containing 8 drops of 10% NaOH solution. The light blue, cloudy mixture that developed (pH 3) was heated gently until the final volume was ca. 35 ml. A pale green product was noted at this time and the mixture was allowed to concentrate further for two days at room temperature. The shiny, light green product was filtered, washed with water and methanol, and oven-dried at 80"C. The product when ground in a mortar and pestle lost its luster and had the consistency of talcum powder. Anal. Calc. for CuCioHtT.32N5Og.66Pt:C, 26.29; H, 3.79; N, 15.33. Found: C, 26.72; H, 4.25, N, 16.31%. RESULTS AND DISCUSSION A tabulation of the major IR bands of the complex is given in Table 1. Evidence for ring nitrogen coordination comes from the loss of C--C and C=N stretches at 1706 and 1689cm -t, respec-
I-IO 3'
Oil 2'
Fig. 1. Numbering scheme of 5'-adenylic acid (Y-AMP).
Table 1. Selected IR data (cm -~) for the Cu(5'-AMP).813H20 complex'i" Ligand
Complex
5'-AMP(LH2)
CuL'g/3H20
3378 w 3360 s 3250 s 1706 s 1689 s 1656 m, ap 1613 m 1539 w, sp 1475 w, sp 1420 m, sp 1222 s --
3378 s 3356 s 3270 s -1689 sh 1656 s, bd 1603 m 1539 sh 1479 sh 1425 w -1120 s 980 m 943 sh 1145 s, sh 1075 s 1050 s
-938 s ! 143 s 1071 s 1044 s 975 w 899 w 867 w
899 sh 867 sh
Assignment
vOH(H20) rNH2(asym.) uNH:,(sym.) uC=C ~,C=N 8NH2(comb. with 8H20) uring -uP=O (free) uP03 (asym.) uP03 (sym.) uP--O(OH)2 uribose (deg.)
uribose (sym.)
tAbbreviations: s, strong; m, medium; w, weak; sh, shoulder; bd, broad; sp, sharp. tively, upon complexation. The presence, however, of the NH2 stretch (asym. and sym.) at 3360 and 3250cm -~, respectively, as well as the NH2 bend at 1656 cm -j precludes C(6)NH2 as a site of metal coordination. These data do not distinguish between N(I), N(3), or N(7) coordination. However, since steric constraints imposed by the ribose sugar moiety militate against N(3) coordination, and since the relative basicity of N(7) is greater than N(I) (N(7) has the proton in neutral adenine), the coordination site on the ring can be assigned as N(7). Indeed, recent crystallographic studies on metal complexes containing adenine [5], 9-CHradenine (an adenosine analog)[6, 7], and Y-AMP [8] support this conclusion. Evidence for phosphate involvement is seen in the loss in intensity and shift to lower energy of the P=O stretch at 1222cm -~ and the loss of the P=O(OH)2 stretch at 938cm -~ upon complexation. Support for this assignement comes from the appearance of the PO3 stretches (asym. and sym.) in the complex at 1120 and 985cm -~, respectively. This change is qualitatively similar to that observed in the disodium [9], magnesium [10], and cadium [11] salts of 5'-GMP and Y-AMP. The magnitude of the metal phosphate interaction can be followed quantitatively by the shift towards higher energies of the band at about 980cm -j upon complexation. In the present case the band lies at 980cm -~, intermediate between highly ionic and covalent in character. No evidence for ribose sugar coordination is seen as the degenerate ribose stretching frequencies at !143, 1071, 1044 and 975 cm -f, and the symmetric ribose stretching frequencies at 899 and 867 cm -t are virtually unchanged in position or intensity upon complexation. The EPR spectrum of this compound consists of a single, broad, structureless absorption at go~ = 2.16. From the general shape, g-value, and intensity measurements at different tern-
Notes
~
peratures, it was concluded that the absorption originates in a doublet state species of approximate D4h symmetry [12]. A magnified scan at lower fields revealed the presence [13] of HM~N. the spin forbidden transition for S = I species, at 1450G (v = 9.25GHz). This absorption is conclusive evidence for the presence of Cu-Cu interactions in the complex. A Zero Field Splitting IDI value[14] of 0.107cm ' can be calculated from eqn (1) where h and /3 have their usual meanings, v is the spectrometer frequency, g is the average g-value, and HM~N is the magnetic field position of the HMtN band. D~p,i = [0.75[(hv)'- - (2g3HMIN)2]]I/2
= Ng2/32/2kT exp(- 2JflkT)+exp(-2J2/kT)
E/kT)I + Na.
1 + 3 exp ( - 2JJkT) + 3 exp ( - 2JJkT) + exp ( -
(2)
r6
i 4
3OO
i/X 200
//
1(30
I
1
I
t
20
,40
60
80
Fig, 2. Corrected inverse molar susceptibility (V]) and magnetic moment (0) in the range 101-15°K for Cu(5'-AMP).8/3H20. The solid line is a theoretical best fit to the magnetic model described in the text. Here g, k, 3, n, X, and T have their usual meanings; 2Jl and 2./2 are the corresponding singlet-triplet energy separations, E is the separation between the ground states of both dimers, and Na is the temperature-independent paramagnetism (TIP) term. The best fit values obtained were - 120, - 10, - 2 cm-~ and 2.03 for 2J~, 2./2, E, and g, respectively (negative 2J values indicate a singlet ground state). The routine employed calculated and compared the g-values at each experimental point to the average g-value. The goodness of the fit is seen by inspection of Fig. 2. Although the energy separation between ground states of both dimers, E, was allowed to vary, the value of 2 cm ~in the best fit is too small to be considered significant because of the inherent -+ 10cm ~ uncertainty in the method. Therefore, both ground states are assumed to be of equal energy. As can be seen from Fig. 3, Cu(a0 and Cu(b) are connected via a PO2 group. This allows for considerable delocalization of an antiferromagnetic nature through overlapping orbitals producing
iN(7)
~
0
H z
~XXN(7)
I
.O~P(31
H2
l
o
0
Cu(b)
I
01-12
I CO
7".°K
N(9)
0
~ef~
400~
(1)
Additional resonances originating in S = 1 species were observed at 2210, 2340 and 5100G. The electronic spectrum has one broad, structureless absorption in the visible-near IR region at 15.8kK (lkK= 1000cm ~) with a tail to the IR. This band can be attributed to the nearly accidental degenerate transition from the B~ ground state to the E~ set and B2g excited state in approximate D4h symmetry [15]. The transition to the A~ state is at much higher energies. The corrected inverse molar susceptibilities (I-7) and magnetic moments (0) of the compound in the important region from I01 to 15°K are shown in Fig. 2. Several models were attempted in an effort to interpret the data including the Van Vleck dimer [161 and the Ising straight chain polymer[17] models. Both models proved unsatisfactory and a new model was devised that successfully duplicates the experimental points and is consistent with the IR, electronic, and EPR data previously discussed. The model consists of two different dimeric systems, Cu(a)-Cu(a) and Cu(a)--Cu(b) where a and b represent the two types of copper(II) ions in the polymer (each with a 2J value associated with it), Fig. 3, and is completely analogous to the polymeric Cu(ll)-nucleotide complex of 5'-GMP, [Cu3(5'-GMP)3(H20)s.SH20],, recently characterized structurally[18, 19] and magnetically[I]. In addition, the energy separation between the ground states of the dimers was allowed to vary. Equation (2) is obtained by summing over a Boltzman distribution [201 in the energy levies present in the system.
1389
'0
Fi(l) /
0
jOH 2
O~ --C~(ot)"
HzO j
~OH 2 N(7)..-.--~
Fig. 3. Schematic representation of the proposed structure of Cu(5'-AMP).8/3 H20 (after Ref.[18, 19]).
1390
Notes
the large 2J value. Also, Cu(a0 and Cu(a2) are situated such that there can be some through space antiferromagnetic coupling of a much smaller magnitude, corresponding to 22".,, The connections between the unit cell depicted in Fig. 3 and adjacent ones, indicated by arrows, are not conducive to magnetic coupling because the metal ions are presumed to be well separated in space by nucleotide moieties and there are only multi-atom bridges between the ions.
Acknowledgement--The authors acknowledge support from a G. N. Shuster Fellowship. Department o[ Chemistry The University o[ Texas at Austin Austin, TX 78712 U.S.A.
HAROLD C. NELSON
Department o! Chemistry Herbert H. Lehman College of The City University o[ New York Bronx, NY 10468 U.S.A.
JUAN F. VILLA
REFERENCES I. J. F. Villa, F. J. Rudd and H. C. Nelson, J. Chem. Sac. (Dalton Trans.) 110 (1979). 2. Inorganic Biochemistry (Edited by G. L. Eichhorn), Vol. 2, Chap. 32 and 33, Elsevier, New York (1973).
3. D. J. Hodgson, In Progress in Inorganic Chemistry (Edited by S. J. Lippard), VoL 23, p. 211. Wiley, New York (1977). 4. H. C. Nelson and J. F. Villa, Spectrosc. Lett. I1, 67 (1978); J. Chem. Educ. 53, 28 (1976). 5. M. R. Taylor, Acta Crystallogr. 29B, 884 (1973). 6. E. Sletten and M. Rudd, Acta Crystallogr. 31B, 982 (1975). 7. D. J. Szalda, T. J. Kistenmacher, and L. G. Marzilli, lnorg. Chem. 14, 2623 (1975). 8. A. C. Skapski, A. D. Collins, P. De Meester and D. M. L. Goodgame, Biochim. Biophys. Acta 402, 1 (1975). 9. T. Shimanouchi, M. Tsuboi, and Y. Kyogoku, In Advances in Chemical Physics (Edited by I. Prigogine), Vol. 7, Chap. 12. lnterscience, New York (1971). 10. A. Epp, T. Ramasarman, and L. R. Wetter, J. Am. Chem. Sac. 80, 724 (1958). II. M. Ogawa, Yakugaku Zasshi 91,618 (1971). 12. B. J. Hathaway and D. E. Billings, Coord. Chem. Rev. 5, 143 (1970). 13. J. F. Villa, J. M. Flowers, and W. E. Hatfield, Spectrosc. Lett. 3, 201 (1970). 14. N. D. Chasteen and R. L. Belford, Inorg. Chem. 9, 169 (1970). 15. A. B. P. Lever, Inorganic Electronic Spectroscopy. Elsevier, New York (1%8). 16. J. H. Van Vleck, The Theory o/ Electric and Magnetic Susceptibilities, p. 189. Oxford University Press, London (1932). 17. M. E. Fisher, J. Math. Phys. 4, 124 (1%3). 18. K. Aoki, G. R. Clark, and J. D. Orbell, Biochim. Biophys. Acta 425, 369 (1976). 19. E. Sletten and B. Lie, Acta Crystallogr. 32B, 3301 (1976). 20. W. Wojciechowski, lnorg. Chim. Acta 1,319 (1976).
J. inorg,nucl.Chem.Vol.41, pp. 1390-1392 © PergamonPressLtd., 1979. Printedin GreatBritain
oo22-19o21791o9o1-139Ol5O2.OOlO
Preparation and thermal decomposition of some metal thiophenolates (Received 18 December 1978; received for publication 2 February 1979) The metal thiolates or mercaptides, M(SR)x, are frequently mentioned in the chemical literature but most have not been well characterized[I]. Some metal derivatives of ethane- and butanethiol[2], as well as pentafluorothiophenol[3] have recently been described. In this paper the preparation, characterization and thermal decomposition of a number of metal thiophenolates are reported. The copper and lead derivatives CuSPh and Pb(SPhh have been reported previously as useful synthetic reagents [4, 5], but only in the case of Pb(SPhh has its preparation been discussed. Various methods have been reported for the preparation of thiophenolates: reactions of thiophenol with an aqueous ammoniacal solution of zinc and cobalt ions, forming Co(SPh)2.PhSH and Zn(SPh).2NH3[6]; reactions of thiophenol with organometallics such as BiPh3 forming Bi(SPh)3, Pb(SPh)2 (from PIuPb), Hg(SPh)2[7]; reactions of thiophenol with Group V trichlorides forming As(SPhh, Sb(SPh)3, Bi(SPh)3[10-13]; reaction of thiophenol with Ni(SBu n): in cyclohexane forming Ni(SPh)2 [6]. Metal derivatives of the thiols can readily be prepared by stirring an aqueous solution of the requisite metal ion with a liquid thiol or a solution of a thiol. The heavy metal thiolates will precipitate. In this way the thiophenolates M(SPh) (M = Ag, T1, Au, Cu), M(SPh)2 (M = Pd, Pb, Hg, Pt, Cd, Sn, Ni, Co, Zn) and M(SPh)3 (M = As, Bi) were prepared from simple salts. In the cases of Au(I), Cu(I) and Pt(II) the starting materials were Au(III), Cu(II) and Pt(IV) and a disproportionation reaction occurred, as has been observed with other thiols [3], forming 2Cu 2÷ + 4PhSH ~ 2CuSPh + PhSSPh diphenyldisulfide and the metal in its lower oxidation state. The
precipitated disulfide was removed by washing with a suitable solvent such as benzene or ether. The metal thiophenolates are generally totally insoluble in common organic solvents, see Table 2, and can only be purified by washing with solvents suitable for the reagents involved. The lack of solubility is probably due to the formation of polymeric units through sulfur bridges, as has been observed in thiolates such as Ni(SR)2[14]. In some cases the Ph
S
/ \,/
Ph
S~
Ph
S
\
Ph
",./
S,~
Ph
/ S.,. /
Ph chemical analyses do not correspond to a simple metal thiophenolate. Particularly the zinc and cobalt compounds are intermediate between M(SPh)2 and the previously reported Zn(SPh)2.2NH3 and Co(SPhh'PhSH[6]. Similarly poor results were obtained for Ni(SPh)2 and Cd(SPh)2 and being low probably correspond to the partially hydrated form M(SPh)2.(H20)=. It is noteworthy that in a previous report on metal thiolates some difficulty was encountered with the analytical results [6]. Due to the polymeric nature of most metal thiolates they often appear to decompose at or before their melting points. The thermal decomposition of some metallic derivatives of pentafluoro- and pentachloro-thiophenol have been studied and found to give the metal, its halide or sulfide[15]. The thermal decompositionof the metal thiophenolateswas studied at approx. 450°. The solid remaining was identified from its X-ray powder pattern (see Table 1). The volatile products were not identified.
Notes
L inorg,nacl.Chem.Vol.41,pp. 1388-1390 © PergamonPressLtd., 1979. Printedin GreatBritain
0022-1902/79/0901-13881502.00/0
A novel Cu(II)-5'-adenylic acid complex (Received 30 November 1978; received [or publication 2 February 1979)
In an effort to systematically elucidate the chemical properties of copper (ll) coordination compounds with nucleic acid constituents, we recently reported the bonding, and electronic and magnetic properties of a copper(ll)-nucleotide complex of 5'guanylic acid, 5'-GMP [1]. The study of metal complexation with nucleotides is especially relevant since these compounds constitute the monomer units of DNA and RNA and since transition metal complexes containing nucleotides might serve as models for elucidating the role played by various transition metal ions like copper(I1) in both the reversible unwinding and the replication and transcription processes of DNA [2]. In spite of the current interest in transition metal-nucleic acid complexes [3], no reports of any coordination compound with 5'-adenylic acid (Y-AMP), Fig. 1, and copper(lI) have appeared to date. In this paper we wish to report the synthesis, and electronic and magnetic properties of the first copper(II) coordination compound with 5'-AMP.
EXPERIMENTAL Measurements. The electron paramagnetic resonance (EPR) spectra were obtained on a Varian HFE-12 spectrometer at room and liquid nitrogen (77°K) temperatures using X-band frequencies, the variable temperature bulk magnetic susceptibility measurements (12-300°K) in a Faraday balance setup previously described [4], the electronic spectra (8-25 kK) as Nujol mulls in a Beckman DK-2A spectrometer, and the IR spectra (0.66-4.0 kK) as KBr pellets in a Perkin-EImer Model 21 spectrometer. All measurements were made with polycrystalline samples; IR spectra run as pellets and mulls (Nujol and fluorolube) were comparable. Preparation of Cu(5'-AMP).8/3H20. A solution of 0.5 mmole of Cu(NO3)2'3I'[20 in 5 ml of distilled water was added with constant stirring to a neutral solution of Y-AMP, prepared by addition of 0.3395 g (I mmole) of ligand to 40 ml of distilled water at 55°C containing 8 drops of 10% NaOH solution. The light blue, cloudy mixture that developed (pH 3) was heated gently until the final volume was ca. 35 ml. A pale green product was noted at this time and the mixture was allowed to concentrate further for two days at room temperature. The shiny, light green product was filtered, washed with water and methanol, and oven-dried at 80"C. The product when ground in a mortar and pestle lost its luster and had the consistency of talcum powder. Anal. Calc. for CuCioHtT.32N5Og.66Pt:C, 26.29; H, 3.79; N, 15.33. Found: C, 26.72; H, 4.25, N, 16.31%. RESULTS AND DISCUSSION A tabulation of the major IR bands of the complex is given in Table 1. Evidence for ring nitrogen coordination comes from the loss of C--C and C=N stretches at 1706 and 1689cm -t, respec-
I-IO 3'
Oil 2'
Fig. 1. Numbering scheme of 5'-adenylic acid (Y-AMP).
Table 1. Selected IR data (cm -~) for the Cu(5'-AMP).813H20 complex'i" Ligand
Complex
5'-AMP(LH2)
CuL'g/3H20
3378 w 3360 s 3250 s 1706 s 1689 s 1656 m, ap 1613 m 1539 w, sp 1475 w, sp 1420 m, sp 1222 s --
3378 s 3356 s 3270 s -1689 sh 1656 s, bd 1603 m 1539 sh 1479 sh 1425 w -1120 s 980 m 943 sh 1145 s, sh 1075 s 1050 s
-938 s ! 143 s 1071 s 1044 s 975 w 899 w 867 w
899 sh 867 sh
Assignment
vOH(H20) rNH2(asym.) uNH:,(sym.) uC=C ~,C=N 8NH2(comb. with 8H20) uring -uP=O (free) uP03 (asym.) uP03 (sym.) uP--O(OH)2 uribose (deg.)
uribose (sym.)
tAbbreviations: s, strong; m, medium; w, weak; sh, shoulder; bd, broad; sp, sharp. tively, upon complexation. The presence, however, of the NH2 stretch (asym. and sym.) at 3360 and 3250cm -~, respectively, as well as the NH2 bend at 1656 cm -j precludes C(6)NH2 as a site of metal coordination. These data do not distinguish between N(I), N(3), or N(7) coordination. However, since steric constraints imposed by the ribose sugar moiety militate against N(3) coordination, and since the relative basicity of N(7) is greater than N(I) (N(7) has the proton in neutral adenine), the coordination site on the ring can be assigned as N(7). Indeed, recent crystallographic studies on metal complexes containing adenine [5], 9-CHradenine (an adenosine analog)[6, 7], and Y-AMP [8] support this conclusion. Evidence for phosphate involvement is seen in the loss in intensity and shift to lower energy of the P=O stretch at 1222cm -~ and the loss of the P=O(OH)2 stretch at 938cm -~ upon complexation. Support for this assignement comes from the appearance of the PO3 stretches (asym. and sym.) in the complex at 1120 and 985cm -~, respectively. This change is qualitatively similar to that observed in the disodium [9], magnesium [10], and cadium [11] salts of 5'-GMP and Y-AMP. The magnitude of the metal phosphate interaction can be followed quantitatively by the shift towards higher energies of the band at about 980cm -j upon complexation. In the present case the band lies at 980cm -~, intermediate between highly ionic and covalent in character. No evidence for ribose sugar coordination is seen as the degenerate ribose stretching frequencies at !143, 1071, 1044 and 975 cm -f, and the symmetric ribose stretching frequencies at 899 and 867 cm -t are virtually unchanged in position or intensity upon complexation. The EPR spectrum of this compound consists of a single, broad, structureless absorption at go~ = 2.16. From the general shape, g-value, and intensity measurements at different tern-
Notes
~
peratures, it was concluded that the absorption originates in a doublet state species of approximate D4h symmetry [12]. A magnified scan at lower fields revealed the presence [13] of HM~N. the spin forbidden transition for S = I species, at 1450G (v = 9.25GHz). This absorption is conclusive evidence for the presence of Cu-Cu interactions in the complex. A Zero Field Splitting IDI value[14] of 0.107cm ' can be calculated from eqn (1) where h and /3 have their usual meanings, v is the spectrometer frequency, g is the average g-value, and HM~N is the magnetic field position of the HMtN band. D~p,i = [0.75[(hv)'- - (2g3HMIN)2]]I/2
= Ng2/32/2kT exp(- 2JflkT)+exp(-2J2/kT)
E/kT)I + Na.
1 + 3 exp ( - 2JJkT) + 3 exp ( - 2JJkT) + exp ( -
(2)
r6
i 4
3OO
i/X 200
//
1(30
I
1
I
t
20
,40
60
80
Fig, 2. Corrected inverse molar susceptibility (V]) and magnetic moment (0) in the range 101-15°K for Cu(5'-AMP).8/3H20. The solid line is a theoretical best fit to the magnetic model described in the text. Here g, k, 3, n, X, and T have their usual meanings; 2Jl and 2./2 are the corresponding singlet-triplet energy separations, E is the separation between the ground states of both dimers, and Na is the temperature-independent paramagnetism (TIP) term. The best fit values obtained were - 120, - 10, - 2 cm-~ and 2.03 for 2J~, 2./2, E, and g, respectively (negative 2J values indicate a singlet ground state). The routine employed calculated and compared the g-values at each experimental point to the average g-value. The goodness of the fit is seen by inspection of Fig. 2. Although the energy separation between ground states of both dimers, E, was allowed to vary, the value of 2 cm ~in the best fit is too small to be considered significant because of the inherent -+ 10cm ~ uncertainty in the method. Therefore, both ground states are assumed to be of equal energy. As can be seen from Fig. 3, Cu(a0 and Cu(b) are connected via a PO2 group. This allows for considerable delocalization of an antiferromagnetic nature through overlapping orbitals producing
iN(7)
~
0
H z
~XXN(7)
I
.O~P(31
H2
l
o
0
Cu(b)
I
01-12
I CO
7".°K
N(9)
0
~ef~
400~
(1)
Additional resonances originating in S = 1 species were observed at 2210, 2340 and 5100G. The electronic spectrum has one broad, structureless absorption in the visible-near IR region at 15.8kK (lkK= 1000cm ~) with a tail to the IR. This band can be attributed to the nearly accidental degenerate transition from the B~ ground state to the E~ set and B2g excited state in approximate D4h symmetry [15]. The transition to the A~ state is at much higher energies. The corrected inverse molar susceptibilities (I-7) and magnetic moments (0) of the compound in the important region from I01 to 15°K are shown in Fig. 2. Several models were attempted in an effort to interpret the data including the Van Vleck dimer [161 and the Ising straight chain polymer[17] models. Both models proved unsatisfactory and a new model was devised that successfully duplicates the experimental points and is consistent with the IR, electronic, and EPR data previously discussed. The model consists of two different dimeric systems, Cu(a)-Cu(a) and Cu(a)--Cu(b) where a and b represent the two types of copper(II) ions in the polymer (each with a 2J value associated with it), Fig. 3, and is completely analogous to the polymeric Cu(ll)-nucleotide complex of 5'-GMP, [Cu3(5'-GMP)3(H20)s.SH20],, recently characterized structurally[18, 19] and magnetically[I]. In addition, the energy separation between the ground states of the dimers was allowed to vary. Equation (2) is obtained by summing over a Boltzman distribution [201 in the energy levies present in the system.
1389
'0
Fi(l) /
0
jOH 2
O~ --C~(ot)"
HzO j
~OH 2 N(7)..-.--~
Fig. 3. Schematic representation of the proposed structure of Cu(5'-AMP).8/3 H20 (after Ref.[18, 19]).
1390
Notes
the large 2J value. Also, Cu(a0 and Cu(a2) are situated such that there can be some through space antiferromagnetic coupling of a much smaller magnitude, corresponding to 22".,, The connections between the unit cell depicted in Fig. 3 and adjacent ones, indicated by arrows, are not conducive to magnetic coupling because the metal ions are presumed to be well separated in space by nucleotide moieties and there are only multi-atom bridges between the ions.
Acknowledgement--The authors acknowledge support from a G. N. Shuster Fellowship. Department o[ Chemistry The University o[ Texas at Austin Austin, TX 78712 U.S.A.
HAROLD C. NELSON
Department o! Chemistry Herbert H. Lehman College of The City University o[ New York Bronx, NY 10468 U.S.A.
JUAN F. VILLA
REFERENCES I. J. F. Villa, F. J. Rudd and H. C. Nelson, J. Chem. Sac. (Dalton Trans.) 110 (1979). 2. Inorganic Biochemistry (Edited by G. L. Eichhorn), Vol. 2, Chap. 32 and 33, Elsevier, New York (1973).
3. D. J. Hodgson, In Progress in Inorganic Chemistry (Edited by S. J. Lippard), VoL 23, p. 211. Wiley, New York (1977). 4. H. C. Nelson and J. F. Villa, Spectrosc. Lett. I1, 67 (1978); J. Chem. Educ. 53, 28 (1976). 5. M. R. Taylor, Acta Crystallogr. 29B, 884 (1973). 6. E. Sletten and M. Rudd, Acta Crystallogr. 31B, 982 (1975). 7. D. J. Szalda, T. J. Kistenmacher, and L. G. Marzilli, lnorg. Chem. 14, 2623 (1975). 8. A. C. Skapski, A. D. Collins, P. De Meester and D. M. L. Goodgame, Biochim. Biophys. Acta 402, 1 (1975). 9. T. Shimanouchi, M. Tsuboi, and Y. Kyogoku, In Advances in Chemical Physics (Edited by I. Prigogine), Vol. 7, Chap. 12. lnterscience, New York (1971). 10. A. Epp, T. Ramasarman, and L. R. Wetter, J. Am. Chem. Sac. 80, 724 (1958). II. M. Ogawa, Yakugaku Zasshi 91,618 (1971). 12. B. J. Hathaway and D. E. Billings, Coord. Chem. Rev. 5, 143 (1970). 13. J. F. Villa, J. M. Flowers, and W. E. Hatfield, Spectrosc. Lett. 3, 201 (1970). 14. N. D. Chasteen and R. L. Belford, Inorg. Chem. 9, 169 (1970). 15. A. B. P. Lever, Inorganic Electronic Spectroscopy. Elsevier, New York (1%8). 16. J. H. Van Vleck, The Theory o/ Electric and Magnetic Susceptibilities, p. 189. Oxford University Press, London (1932). 17. M. E. Fisher, J. Math. Phys. 4, 124 (1%3). 18. K. Aoki, G. R. Clark, and J. D. Orbell, Biochim. Biophys. Acta 425, 369 (1976). 19. E. Sletten and B. Lie, Acta Crystallogr. 32B, 3301 (1976). 20. W. Wojciechowski, lnorg. Chim. Acta 1,319 (1976).
J. inorg,nucl.Chem.Vol.41, pp. 1390-1392 © PergamonPressLtd., 1979. Printedin GreatBritain
oo22-19o21791o9o1-139Ol5O2.OOlO
Preparation and thermal decomposition of some metal thiophenolates (Received 18 December 1978; received for publication 2 February 1979) The metal thiolates or mercaptides, M(SR)x, are frequently mentioned in the chemical literature but most have not been well characterized[I]. Some metal derivatives of ethane- and butanethiol[2], as well as pentafluorothiophenol[3] have recently been described. In this paper the preparation, characterization and thermal decomposition of a number of metal thiophenolates are reported. The copper and lead derivatives CuSPh and Pb(SPhh have been reported previously as useful synthetic reagents [4, 5], but only in the case of Pb(SPhh has its preparation been discussed. Various methods have been reported for the preparation of thiophenolates: reactions of thiophenol with an aqueous ammoniacal solution of zinc and cobalt ions, forming Co(SPh)2.PhSH and Zn(SPh).2NH3[6]; reactions of thiophenol with organometallics such as BiPh3 forming Bi(SPh)3, Pb(SPh)2 (from PIuPb), Hg(SPh)2[7]; reactions of thiophenol with Group V trichlorides forming As(SPhh, Sb(SPh)3, Bi(SPh)3[10-13]; reaction of thiophenol with Ni(SBu n): in cyclohexane forming Ni(SPh)2 [6]. Metal derivatives of the thiols can readily be prepared by stirring an aqueous solution of the requisite metal ion with a liquid thiol or a solution of a thiol. The heavy metal thiolates will precipitate. In this way the thiophenolates M(SPh) (M = Ag, T1, Au, Cu), M(SPh)2 (M = Pd, Pb, Hg, Pt, Cd, Sn, Ni, Co, Zn) and M(SPh)3 (M = As, Bi) were prepared from simple salts. In the cases of Au(I), Cu(I) and Pt(II) the starting materials were Au(III), Cu(II) and Pt(IV) and a disproportionation reaction occurred, as has been observed with other thiols [3], forming 2Cu 2÷ + 4PhSH ~ 2CuSPh + PhSSPh diphenyldisulfide and the metal in its lower oxidation state. The
precipitated disulfide was removed by washing with a suitable solvent such as benzene or ether. The metal thiophenolates are generally totally insoluble in common organic solvents, see Table 2, and can only be purified by washing with solvents suitable for the reagents involved. The lack of solubility is probably due to the formation of polymeric units through sulfur bridges, as has been observed in thiolates such as Ni(SR)2[14]. In some cases the Ph
S
/ \,/
Ph
S~
Ph
S
\
Ph
",./
S,~
Ph
/ S.,. /
Ph chemical analyses do not correspond to a simple metal thiophenolate. Particularly the zinc and cobalt compounds are intermediate between M(SPh)2 and the previously reported Zn(SPh)2.2NH3 and Co(SPhh'PhSH[6]. Similarly poor results were obtained for Ni(SPh)2 and Cd(SPh)2 and being low probably correspond to the partially hydrated form M(SPh)2.(H20)=. It is noteworthy that in a previous report on metal thiolates some difficulty was encountered with the analytical results [6]. Due to the polymeric nature of most metal thiolates they often appear to decompose at or before their melting points. The thermal decomposition of some metallic derivatives of pentafluoro- and pentachloro-thiophenol have been studied and found to give the metal, its halide or sulfide[15]. The thermal decompositionof the metal thiophenolateswas studied at approx. 450°. The solid remaining was identified from its X-ray powder pattern (see Table 1). The volatile products were not identified.