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Copper(I) bromide complexes with heterocyclic thiones and triphenylphosphine as ligands. The X-ray crystal structure of copper(I) pyrimidine-2-thione bis (triphenylphosphine) bromide [Cu(PPh3)2(PymtH)Br]
Po~yhed,on Vol. 8, No. 8, pp. I IO%1 109, 1989 Printed in Great Britain
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0277-5387189 s3.00+ .I0 1989 Pergamon Press plc
COPPER(I) BROMIDE COMPLEXES WITH HETEROCYCLIC THIONES AND TRIPHENYLPHOSPHINE AS LIGANDS. THE X-RAY CRYSTAL STRUCTURE OF COPPER(I) PYRIMIDINE-ZTHIONE BIS (TRIPHENYLPHOSPHINE) BROMIDE [Cu(PPh,),(PymtH)Br] C. LECOMTE*
and St. SKOULIKA
Laboratoire de Min&-alogie et Cristallographie (UA no 809), Facultk des Sciences, Centre de 2&me Cycle, B.P. no 239,54506 Vandoeuvre les Nancy, France and
P. ASLANIDIS, Laboratory
P. KARAGIANNIDIS*
and St. PAPASTEFANOU
of Inorganic Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece (Received 19 October 1988 ; accepted 11 November 1988)
Abstract-Reactions of copper(I) bromide with heterocyclic thiones (L) [L = pyridine-Z thione (py2SH), pyridine-4-thione (py4SH), pyrimidine-Zthione (pymtH), 1,3&iazolidine2-thione (tzdtH), I-methyl-1,3-imidazoline-2-thione (meimtH), benz-1,3-imidazoline-2thione (bzimtH,), benz-1,3-oxazoline-2-thione (bzoxtH), 5-nitro-2-benz-1,3-imidazoline-2thione (nbzimtH,), benz-1,3-thiazoline-2-thione (bztzH) and quinazolinone-2-thione (qnotH2)] in the presence of triphenylphosphine yields mononuclear complexes of the general formula [Cu(L)(PPh,),Br]. The complexes have been characterized by elemental analysis, IR, UV-vis and NMR spectroscopy. The crystal structure of [Cu(PPh3)2 (pymtH)Br] has been determined by single-crystal X-ray diffraction methods. The yellow-orange crystals are monoclinic, space group P2 ,/n with a = 13.035(2), b = 43.660(9), c = 13.446(2) A, fi = 90.68(2)“, and Dcalc= 1.352 g cme3, V = 7652 w3, R(F) = 0.067; RJF) = 0.069, GOF = 1.19. In both molecules of the asymmetric unit, the pymtH molecule acts as a monodentate ligand through the S atom (Cu-S = 2.352(3) A).
Heterocyclic thiones as ligands are potentially ambidentate or multi-functional donors with either the exocyclic S or heterocyclic N (or S or 0) atom available for coordination. ’ The aim of the present paper is to further our present knowledge in the field of these ligands which exhibit a thionethiol (-N=C-SH % -NH-C=S) equilibrium. Recently, the complexing properties of these ligands with copper(I) in the presence of triphenylphosphine have been studied, and a variety of interesting complexes (monomeric or dimeric) with the thione ligands acting as S-donors have been obtained. 2,3 More recently, monomeric complexes
*Authors to whom correspondence should be addressed.
formulated as [Cu(PPh,),(L),]NO, have been obtained via a simple method of preparation by direct reaction of Cu(PPh3)2N03 with the ligands investigated.4 As a part of the examination of the ligation behaviour of these ligands, we report in this paper the preparation and characterization of a series of mononuclear Cu’ complexes of general formula [Cu(PPh,),(L)Br].
EXPERIMENTAL Physical measurements
Elementary analyses were performed on a Perkin-Elmer 240 B elemental analyser. IR spectra
1103
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et al.
Table 1. Experimental conditions Formula Formula weight Space group Lattice parameters Diffractometer Radiation Scan type tImin-&_ Scan range, speed Aperture, mm hkf limits Number of reflections measured Number of reflections used Z > 20(Z) Number of parameters Nr NIN, Program used WI ZW% GOF W
CuBrSP,N,C,,H,, 778.9 Monoclinic P2 ,/n a = 13.035(2) b = 43.660(5) c = 13.446(2) A /3 = 90.68(2)’ V= 7651.7 A’ 2 = 8 pEa,= 1.352 g cm-’ Enraf-Nonius CAD4F (room temp) Cu-K, 1 = 1.54051 A w-28 l-70” 1 f0.45 tan 0 0.5 < u < 2” min- ’ 4 -15
were recorded in the 4000-250 cn- ’ region on a Perkin-Elmer 467 spectrophotometer using KBr pellets. Electronic spectra in chloroform solutions were obtained on a Cary 17 DX spectrophotometer. NMR spectra were recorded on a Brucker AW 80 spectrometer. Conductivity measurements were taken in a Wheatstone bridge Model RC 216 B2 using lo- 3 M solutions in acetonitrile or chloroform. Melting points were determined with a Biichi apparatus and are uncorrected. Magnetic susceptibility measurements were taken employing the Faraday technique at different magnetic field strengths. Hg[Co(SCN)], was used as the calibrand. Starting materials
All thione ligands, supplied by EGA or Aldrich, were purified by recrystallization from ethanol. Anhydrous copper(I) bromide, triphenylphosphine and all solvents were of reagent grade and were used without further purification in synthetic work. Preparation of the complexes
CuBr (1 mmol) was suspended in 10 cm3 THF and treated with a 40 cm3 solution of 1 mmol of the appropriate ligand and 2 mmol PPh3 in the same solvent. The reaction mixture was stirred for 1 h at 40°C filtered and cooled to room temperature. Slow evaporation of the solvent at room temperature gave a microcrystalline solid, which was filtered off, washed with ethanol and ether and dried *Atomic coordinates have also been deposited with the Cambridge Crystallographic Data Centre.
in vacua. The yield in this procedure was about 65-
85%. Crystal and molecular structure determination
A suitable crystal of [Cu(PPh3)a(PymtH)Br] was obtained from recrystallization of the complex in THF. Preliminary Weissenberg photographs revealed a monoclinic cell and systematic conditions (h01: h+ I = 2n, Ok0 : k = 2n) led to space group P2,/n. The experimental conditions are given in Table 1. The scattering factors were taken from refs 6 and 7. The structure was solved by the heavy atom method by interpretation of the Patterson map and was refined by standard least-squares and Fourier techniques. Due to thermal motion or disorder problems, the C(31)--C(36) phenyl ring was refined as a rigid group ; all the coordinates of the hydrogen atoms linked to the carbon atoms were calculated and kept fixed during the refinement process. The two N-H hydrogen atom coordinates used were those found in the difference Fourier map in order to distinguish between the two nitrogens of the pyrimidine ring. Main bond distances and angles are given in Table 2. Fractional coordinates, equivalent temperature standard deviations, factors, anisotropic thermal parameters of the atoms, least-squares planes, other bond lengths and structure factors have been deposited as supplementary material with the Editor from whom copies are available on request.* RESULTS Recently,
(py2SH)Br],
AND DISCUSSION
the mononuclear
[Cu(PPh,), by the reaction
complex,
has been isolated
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Heterocyclic thiones with Cu’Br Table 2. Main bond distances (A) and angles (“) Distances Molecule 2
Molecule 1 G(l)--Br(1) Cu(l)_-s(l) Cum-P(l) Cu(l)-P(2) S(lFC(37) P(l)-W) W)_C(7) P(lEC(3) p(2)--c(l9) P(2)--c(25) p(2>--c(3 1) C(37FWl) WlFC(39) C(39)-C(40) C(4O)--c(41) C(4lk-~(2) N(2)--C(37)
Cu(2)---Br(2)
2519(l) 2.345(3) 2.303(2) 2.306(2) 1.695(S) 1.820(S) 1.825(S) 1.815(S) 1.826(9) 1.822(9) 1.820(S) 1.33(l) 1.31(l) 1.37(l) 1.33(l) 1.34(l) 1.34(l)
Cum-S(2) Cu(2k--p(3) Cu(2~p(4) 8(2F-C(79) P(3)--c(43) P(3)--c(49) P(3W(55) Pt4)--C(61) P(4F-C(67) P(4FC(73) C(79)_-N(3) N(3)-C(81) C(8 1FC(82) C(82FC(83) C(83tN4) N(4)-C(79)
2.512(2) 2.359(3) 2.304(3) 2.267(3) 1.68(l) 1.80(l) 1.829(9) 1.822(9) 1.80(l) 1.83(l) 1.817(S) 1.35(l) 1.33(2) 1.35(2) 1.32(2) 1.38(l) 1.36(l)
Angles
BrtlFJU---P(l) Br(l)--Cu(lW’(2) Br(l)-Cu(l>--S(l) W--Cu(lFp(2) ptlk--Cu(l~8(l) P(2FCu(lk---s(l) Cu(lk--s(l)-C(37)
108.0(l) 111.0(l) 108.2( 1) 112.9( 1) 106.5(l) 1lO.O(1) 114.6(3)
of Cu(PPh&Br with Zr(py2!$, in THF.3 However, we report in this study a more simple and general method for the preparation of such complexes, namely, the reaction between the heterocyclic thiones and a 1 : 2 mixture of CuBr and PPh3. Table 3 lists the compounds with their colours, melting points and analytical data. The results of the elemental analyses for all complexes show good agreement with the formula [Cu(PPh,),(L)Br]. The magnetic susceptibility measurements at room temperature indicate that the complexes are diamagnetic, consistent with a d” configuration. They can be handled in air without evident decomposition, decompose slowly in water, are soluble in chloroform, acetone and acetonitrile, slightly soluble in methanol and benzene but insoluble in ether. Their conductivity measurements in chloroform or acetonitrile show, as expected, a non-electrolytic nature. Description of the crystal structure
A stereographic projection of the two molecules of the asymmetric unit is given in Fig. 2. Figure 1 is a PLUTO drawing of the molecule with the numbering scheme used for the main atoms. In both
Br(2)-Cu(2FP(3) Br(2)--Cu(2)_-P(4) Br(2)--Cu(2F8(2) P(3)-Cu(2F-P(4) v3~Cu(2v(2) v4)--cu(2F8(2) Cu(2)_8(2)--c(79)
101.1(l) 107.1(l) 110.5(l) 124.3( 1) 106.1(l) 107.3( 1) 108.6(4)
molecules the Cu atom is four-coordinated by a bromide atom, two triphenylphosphine ligands and one monodentate pymtH molecule coordinating through the sulphur atom ; the Cu-L bond lengths in both molecules are similar (Table 2). However, the coordination polyhedra of both molecules of the asymmetric unit are different due to the P--&-P coordination angles : The Cu( 1) coordination polyhedron is close to a regular tetrahedron (106.5 < L-Cu-L’ < 112.9”), whereas in the Cu(2) polyhedron, the P,-Cu2--P, angle is 124.3(l)“. This demonstrates the flexibility of these coordination angles in this class of compounds. However, all these angles fall within the range reported for other tetrahedral complexes of copper(I).8-‘2 A possible explanation for the large value of the P3-Cu-Pq angle is the n-n interaction between the phenyl ring C(49). . . C(54) and the pymtH (N, . . . NJ entity : the angles between their least-squares planes is 16” and the distances of atoms C(51), C(50), C(49), C(52) are, respectively, 3.04, 3.02, 3.35 and 3.34 A from the pymtH plane. The average Cu-S bond length is 2.352 A as usually found for tetrahedrally coordinated copper(1) complexes with thione-sulphur donors.4*‘3
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C. LECOMTE
et al.
Fig. 1. PLUTO drawing of the two molecules of the asymmetric unit.
Fig. 2. ORTEP stereoview of the molecules.
The Cu-P bond lengths are normal (see, for example refs 4, 14, 15). The average Cu-Br bond lengths of 2.515 A are significantly longer than those observed in Cu(PPh,)3Br (2.35 A).” Moreover, it is slightly longer than the corresponding Cu-Br distance of 2.462 A in Cu(PPh,), and it compares well with that (py2SH)Br, found in (TTTCu2Br4)‘6 (TTT = tetrathiotetracene) (2.490 A) and in [Cu(PPh3)Br]4’7 (2.495 A).
Hydrogen bonds and intermolecular contacts
As described in the Experimental section, the hydrogen atoms linked to Nz and N4 were found in difference Fourier maps and no peak at a distance of about 1 A of N,, N3 was visible. Furthermore, the bond distances in the pymtH ring agree with this assignment (Table 2) and are close to those
found in most pyrimidine-2-thione complexes.‘8T’9 As shown in Fig. 2, intramolecular hydrogen bonds between the bromide atoms (Br,, BrJ and the HN,, HN4 hydrogen occur (Br, . . . N2 = 3.205(7) A, Br2-N, = 3.300(8) A). These hydrogen bonds are of different strength, as shown also by the leastsquares planes formed by the Cu, Br, S, C, N atoms (Table 4). Furthermore, short van der Waals contacts exist between one H-C hydrogen atom of the pymtH ring of one molecule, with the bromide atom of the other molecule, giving rise to an almost dimeric molecule (Br,-C(83) = 3.67(l) A, Br,---C(41) = 3.462(9) A). Then the strongest hydrogen bond to one bromide atom is associated with the weakest van der Waals contact. As a consequence of this dimer formation, Br,, Br2, NZ, N.,, C(83), C(41) form a plane within 0.6 A (Table 4). Finally, no other intermolecular contact is smaller than 3.5 A.
Heterocyclic thiones with Cu’Br
1107
IR spectra
IR spectra, in the region 4000-250 cm- ‘, provide information concerning the mode of coordination. Some selected bands and their assignments are given in Table 5. The solid-state IR spectra of complexes studied, exhibit the dominance of the thione form of the ligands investigated with the presence of v(NH) bands at 318G-3 130 cm- ‘,2%22the absence of any evidence for v(SH) bands in the 2500-2600 cm-’ region,23-24 and the production of characteristic “thioamide” bands.23 All the pymtH ligands are bonded to the metal through the sulphur atom, as shown by the shifts of the “thioamide” bands observed by comparing the IR spectra of the complexes with those of the free ligands. Of the four “thioamide” bands, those showing the most significant changes upon coordination are (III) and (IV). “Thioamide(II1)” undergoes downward shifts ranging from 10 to 60 cm- ‘. “Thioamide(IV)” shows similar behaviour, although here, the shifts are generally greater (3& 100 cm-‘), and the absorptions are in many cases pertly masked by strong triphenylphosphine bands. In agreement with the X-ray crystal structure there is no positive evidence that in the complexes discussed here, the ligands behave as bidentate. In fact, “thioamide(1)” occurred at the same wavenumbers, or showed small (+ 5 cm- ‘) shifts, signifying that the ligands are not N-bonded to the metal. The N-H stretching frequency in the complexes tends to lie at a lower wavenumber than in the free ligands, but the shifts of this band are small, suggesting that the nitrogen atoms are not involved in bonding. 24 The directions of the shifts in the position of all the bands in the spectra of the complexes are the same, indicating that the binding pattern in all the complexes must be similar. The monodentate nature of the ligands is further confirmed by the presence of a band around 350 cm-’ , which is assigned to the v(Cu-S) vibration. 25 Electronic and NMR spectra
The UV-vis spectra of the compounds in CHC13 solutions, as expected, show only two absorption bands at 31&360 and 24&280 nm, which can be assigned as intraligand transitions. The ‘H NMR spectra of the complexes in CDC13 solution also provided proof that ligands are (NH) protonated. The absence of any evidence for the thiol (SH) proton (6 3-5 ppm) and the presence of a peak for the NH group at N IO-14 ppm (sometimes very broad) indicate the thione tautomer as the dominant species in the complexes studied.
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et al.
Table 4. Equation and distances from the least-squares planes Plane 1
0.6087x
-0.5544y
-0.5676~
Brr -0.120
Cu, 0.173
S, 0.170
C 0.0;4
Plane 2
0.3576x
- 0.0576~
-0.9321~
Br, -0.234
Cu, 0.360
S2 -0.348
Plane 3
0.6953x
+ 0.0044y
-0.7187~
= -4.4328
Br, 0.372
Br, 0.584
N* 0.049
N, -0.310
C -0.Y40
Angles between
l-2 l-3 2-3
= 8.9479 N* 0.094 = 8.0309
C 0.07690
Br,” 0.119
N4 0.162
C‘%* -0.555
Cu,” 0.587
38.9” 23.3” 34.0
“Atom not included in the least-squares calculations.
Table 5. Selected NMR and IR spectroscopic data
Compound I II III IV V VI VII VIII IX X
‘H NMR &N-H) (ppm) 13.6 0 a 11.2 13.1 ll 14.1 11.3 13.2+9.0 11.8
v(N---H) 3150 3180 3140 3140 3140 3140 3135 3133 3130 3160
“Thioamide(I1)” 1305 1310 1320 1305 1285 1250 1325 1310 1330 1300
IR (cm- ‘) “Thioamide(II1)” 1025 1020 1020 1022 1030 990 1000 1025 1020 1025
v(Cu-S) 360 h 355 b b 255 b 360 360 380
“No associated N-H activity was observed. bNo absorption attributable to Cu-S vibration was observed.
REFERENCES
1. E. S. Raper, Coord. Chem. Rev. 198561, 115. 2. M. Belicchi Ferrari, G. Gaspari Fava, C. Pelizzi and P. Tarasconi, Inorg. Chim. Acta 1985,97,99. 3. P. Karagiannidis, P. Aslanidis, D. Kessissoglou, B. Krebs and M. Dartmann, Znorg. Chim. Acta (accepted for publication). 4. P. Karagiannidis, P. Aslanidis, S. Papastefanou and A. Terzis, Inorg. Chim. Acta 1989, 156,277. 5. SDP: Structure Determination Package. Enraf Nonius, Delft, The Netherlands (1977). 6. G. Sheldrick, SHELX76. University of Giittingen, Germany (1976). 7. International Tables for X-Ray Crystallography, Vol. IV. Kynoch Press, Birmingham (1974). 8. S. J. Lippard and K. M. Melmed, Znorg. Chem. 1967, 6, 2223.
9. S. J. Lippard and K. M. Melmed, Znorg. Chem. 1969, 8, 2755. 10. G. G. Messmer and G. J. Palenik, Znorg. Chem. 1969, 8, 2750. 11. S. J. Lippard and G. J. Palenik, Znorg. Chem. 1971, 10, 1322. 12. L. M. Engelhardt, C. Pakawatchai and A. H. White, J. Chem. Sot., Dalton Trans. 1985, 125. 13. S. C. Kokkou, V. Schramm and P. Karagiannidis, Acta Cryst. 1985, C41, 1040. 14. I. G. Dance, P. J. Guerney, A. D. Rae and M. L. Scudder, Znorg. Chem. 1983,22,2883. 15. P. H. Davis, R. L. Belford and I. C. Paul, Znorg. Chem. 1973,12,213. 16. R. P. Shibaeva and V. F. Kaminkii, Kristallografiya 1981, 26, 332. 17. R. D. Bereman, M. R. Churchill, P. M. Schaber and M. E. Winkler, Inorg. Chem. 1977, 18, 3122.
Heterocyclic thiones with Cu’Br 18. F. A. Cotton and W. H. Ilsley, Znorg. Chem. 1981, 20, 614. 19. C. Chieh, Can. J. Chem. 1977,56,560. 20. P. P. Singh and R. Rivest, Can. J. Chem. 1968, 46, 2361.
21. B. Singh, M. M. P. Rukhaivar and R. J. Sinha, J. Znorg. Nucl. Chem. 1977,39, 29. 22. A. W. McLellan and G. A. Melson, J. Chem. Sot. A
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1967, 137. 23. C. N. R. Rao and P. Venkataraghavan, Spectrochim. Acta 1962, 18, 541. 24. E. S. Raper and J. L. Brooks, J. Znorg. Nucl. Chem. 1977,39,2163. 25. L. J. Bellamy, The Infrared Spectra of Complex Molecules. Wiley, New York (1966).
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0277-5387189 s3.00+ .I0 1989 Pergamon Press plc
COPPER(I) BROMIDE COMPLEXES WITH HETEROCYCLIC THIONES AND TRIPHENYLPHOSPHINE AS LIGANDS. THE X-RAY CRYSTAL STRUCTURE OF COPPER(I) PYRIMIDINE-ZTHIONE BIS (TRIPHENYLPHOSPHINE) BROMIDE [Cu(PPh,),(PymtH)Br] C. LECOMTE*
and St. SKOULIKA
Laboratoire de Min&-alogie et Cristallographie (UA no 809), Facultk des Sciences, Centre de 2&me Cycle, B.P. no 239,54506 Vandoeuvre les Nancy, France and
P. ASLANIDIS, Laboratory
P. KARAGIANNIDIS*
and St. PAPASTEFANOU
of Inorganic Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece (Received 19 October 1988 ; accepted 11 November 1988)
Abstract-Reactions of copper(I) bromide with heterocyclic thiones (L) [L = pyridine-Z thione (py2SH), pyridine-4-thione (py4SH), pyrimidine-Zthione (pymtH), 1,3&iazolidine2-thione (tzdtH), I-methyl-1,3-imidazoline-2-thione (meimtH), benz-1,3-imidazoline-2thione (bzimtH,), benz-1,3-oxazoline-2-thione (bzoxtH), 5-nitro-2-benz-1,3-imidazoline-2thione (nbzimtH,), benz-1,3-thiazoline-2-thione (bztzH) and quinazolinone-2-thione (qnotH2)] in the presence of triphenylphosphine yields mononuclear complexes of the general formula [Cu(L)(PPh,),Br]. The complexes have been characterized by elemental analysis, IR, UV-vis and NMR spectroscopy. The crystal structure of [Cu(PPh3)2 (pymtH)Br] has been determined by single-crystal X-ray diffraction methods. The yellow-orange crystals are monoclinic, space group P2 ,/n with a = 13.035(2), b = 43.660(9), c = 13.446(2) A, fi = 90.68(2)“, and Dcalc= 1.352 g cme3, V = 7652 w3, R(F) = 0.067; RJF) = 0.069, GOF = 1.19. In both molecules of the asymmetric unit, the pymtH molecule acts as a monodentate ligand through the S atom (Cu-S = 2.352(3) A).
Heterocyclic thiones as ligands are potentially ambidentate or multi-functional donors with either the exocyclic S or heterocyclic N (or S or 0) atom available for coordination. ’ The aim of the present paper is to further our present knowledge in the field of these ligands which exhibit a thionethiol (-N=C-SH % -NH-C=S) equilibrium. Recently, the complexing properties of these ligands with copper(I) in the presence of triphenylphosphine have been studied, and a variety of interesting complexes (monomeric or dimeric) with the thione ligands acting as S-donors have been obtained. 2,3 More recently, monomeric complexes
*Authors to whom correspondence should be addressed.
formulated as [Cu(PPh,),(L),]NO, have been obtained via a simple method of preparation by direct reaction of Cu(PPh3)2N03 with the ligands investigated.4 As a part of the examination of the ligation behaviour of these ligands, we report in this paper the preparation and characterization of a series of mononuclear Cu’ complexes of general formula [Cu(PPh,),(L)Br].
EXPERIMENTAL Physical measurements
Elementary analyses were performed on a Perkin-Elmer 240 B elemental analyser. IR spectra
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Table 1. Experimental conditions Formula Formula weight Space group Lattice parameters Diffractometer Radiation Scan type tImin-&_ Scan range, speed Aperture, mm hkf limits Number of reflections measured Number of reflections used Z > 20(Z) Number of parameters Nr NIN, Program used WI ZW% GOF W
CuBrSP,N,C,,H,, 778.9 Monoclinic P2 ,/n a = 13.035(2) b = 43.660(5) c = 13.446(2) A /3 = 90.68(2)’ V= 7651.7 A’ 2 = 8 pEa,= 1.352 g cm-’ Enraf-Nonius CAD4F (room temp) Cu-K, 1 = 1.54051 A w-28 l-70” 1 f0.45 tan 0 0.5 < u < 2” min- ’ 4 -15
were recorded in the 4000-250 cn- ’ region on a Perkin-Elmer 467 spectrophotometer using KBr pellets. Electronic spectra in chloroform solutions were obtained on a Cary 17 DX spectrophotometer. NMR spectra were recorded on a Brucker AW 80 spectrometer. Conductivity measurements were taken in a Wheatstone bridge Model RC 216 B2 using lo- 3 M solutions in acetonitrile or chloroform. Melting points were determined with a Biichi apparatus and are uncorrected. Magnetic susceptibility measurements were taken employing the Faraday technique at different magnetic field strengths. Hg[Co(SCN)], was used as the calibrand. Starting materials
All thione ligands, supplied by EGA or Aldrich, were purified by recrystallization from ethanol. Anhydrous copper(I) bromide, triphenylphosphine and all solvents were of reagent grade and were used without further purification in synthetic work. Preparation of the complexes
CuBr (1 mmol) was suspended in 10 cm3 THF and treated with a 40 cm3 solution of 1 mmol of the appropriate ligand and 2 mmol PPh3 in the same solvent. The reaction mixture was stirred for 1 h at 40°C filtered and cooled to room temperature. Slow evaporation of the solvent at room temperature gave a microcrystalline solid, which was filtered off, washed with ethanol and ether and dried *Atomic coordinates have also been deposited with the Cambridge Crystallographic Data Centre.
in vacua. The yield in this procedure was about 65-
85%. Crystal and molecular structure determination
A suitable crystal of [Cu(PPh3)a(PymtH)Br] was obtained from recrystallization of the complex in THF. Preliminary Weissenberg photographs revealed a monoclinic cell and systematic conditions (h01: h+ I = 2n, Ok0 : k = 2n) led to space group P2,/n. The experimental conditions are given in Table 1. The scattering factors were taken from refs 6 and 7. The structure was solved by the heavy atom method by interpretation of the Patterson map and was refined by standard least-squares and Fourier techniques. Due to thermal motion or disorder problems, the C(31)--C(36) phenyl ring was refined as a rigid group ; all the coordinates of the hydrogen atoms linked to the carbon atoms were calculated and kept fixed during the refinement process. The two N-H hydrogen atom coordinates used were those found in the difference Fourier map in order to distinguish between the two nitrogens of the pyrimidine ring. Main bond distances and angles are given in Table 2. Fractional coordinates, equivalent temperature standard deviations, factors, anisotropic thermal parameters of the atoms, least-squares planes, other bond lengths and structure factors have been deposited as supplementary material with the Editor from whom copies are available on request.* RESULTS Recently,
(py2SH)Br],
AND DISCUSSION
the mononuclear
[Cu(PPh,), by the reaction
complex,
has been isolated
1105
Heterocyclic thiones with Cu’Br Table 2. Main bond distances (A) and angles (“) Distances Molecule 2
Molecule 1 G(l)--Br(1) Cu(l)_-s(l) Cum-P(l) Cu(l)-P(2) S(lFC(37) P(l)-W) W)_C(7) P(lEC(3) p(2)--c(l9) P(2)--c(25) p(2>--c(3 1) C(37FWl) WlFC(39) C(39)-C(40) C(4O)--c(41) C(4lk-~(2) N(2)--C(37)
Cu(2)---Br(2)
2519(l) 2.345(3) 2.303(2) 2.306(2) 1.695(S) 1.820(S) 1.825(S) 1.815(S) 1.826(9) 1.822(9) 1.820(S) 1.33(l) 1.31(l) 1.37(l) 1.33(l) 1.34(l) 1.34(l)
Cum-S(2) Cu(2k--p(3) Cu(2~p(4) 8(2F-C(79) P(3)--c(43) P(3)--c(49) P(3W(55) Pt4)--C(61) P(4F-C(67) P(4FC(73) C(79)_-N(3) N(3)-C(81) C(8 1FC(82) C(82FC(83) C(83tN4) N(4)-C(79)
2.512(2) 2.359(3) 2.304(3) 2.267(3) 1.68(l) 1.80(l) 1.829(9) 1.822(9) 1.80(l) 1.83(l) 1.817(S) 1.35(l) 1.33(2) 1.35(2) 1.32(2) 1.38(l) 1.36(l)
Angles
BrtlFJU---P(l) Br(l)--Cu(lW’(2) Br(l)-Cu(l>--S(l) W--Cu(lFp(2) ptlk--Cu(l~8(l) P(2FCu(lk---s(l) Cu(lk--s(l)-C(37)
108.0(l) 111.0(l) 108.2( 1) 112.9( 1) 106.5(l) 1lO.O(1) 114.6(3)
of Cu(PPh&Br with Zr(py2!$, in THF.3 However, we report in this study a more simple and general method for the preparation of such complexes, namely, the reaction between the heterocyclic thiones and a 1 : 2 mixture of CuBr and PPh3. Table 3 lists the compounds with their colours, melting points and analytical data. The results of the elemental analyses for all complexes show good agreement with the formula [Cu(PPh,),(L)Br]. The magnetic susceptibility measurements at room temperature indicate that the complexes are diamagnetic, consistent with a d” configuration. They can be handled in air without evident decomposition, decompose slowly in water, are soluble in chloroform, acetone and acetonitrile, slightly soluble in methanol and benzene but insoluble in ether. Their conductivity measurements in chloroform or acetonitrile show, as expected, a non-electrolytic nature. Description of the crystal structure
A stereographic projection of the two molecules of the asymmetric unit is given in Fig. 2. Figure 1 is a PLUTO drawing of the molecule with the numbering scheme used for the main atoms. In both
Br(2)-Cu(2FP(3) Br(2)--Cu(2)_-P(4) Br(2)--Cu(2F8(2) P(3)-Cu(2F-P(4) v3~Cu(2v(2) v4)--cu(2F8(2) Cu(2)_8(2)--c(79)
101.1(l) 107.1(l) 110.5(l) 124.3( 1) 106.1(l) 107.3( 1) 108.6(4)
molecules the Cu atom is four-coordinated by a bromide atom, two triphenylphosphine ligands and one monodentate pymtH molecule coordinating through the sulphur atom ; the Cu-L bond lengths in both molecules are similar (Table 2). However, the coordination polyhedra of both molecules of the asymmetric unit are different due to the P--&-P coordination angles : The Cu( 1) coordination polyhedron is close to a regular tetrahedron (106.5 < L-Cu-L’ < 112.9”), whereas in the Cu(2) polyhedron, the P,-Cu2--P, angle is 124.3(l)“. This demonstrates the flexibility of these coordination angles in this class of compounds. However, all these angles fall within the range reported for other tetrahedral complexes of copper(I).8-‘2 A possible explanation for the large value of the P3-Cu-Pq angle is the n-n interaction between the phenyl ring C(49). . . C(54) and the pymtH (N, . . . NJ entity : the angles between their least-squares planes is 16” and the distances of atoms C(51), C(50), C(49), C(52) are, respectively, 3.04, 3.02, 3.35 and 3.34 A from the pymtH plane. The average Cu-S bond length is 2.352 A as usually found for tetrahedrally coordinated copper(1) complexes with thione-sulphur donors.4*‘3
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Fig. 1. PLUTO drawing of the two molecules of the asymmetric unit.
Fig. 2. ORTEP stereoview of the molecules.
The Cu-P bond lengths are normal (see, for example refs 4, 14, 15). The average Cu-Br bond lengths of 2.515 A are significantly longer than those observed in Cu(PPh,)3Br (2.35 A).” Moreover, it is slightly longer than the corresponding Cu-Br distance of 2.462 A in Cu(PPh,), and it compares well with that (py2SH)Br, found in (TTTCu2Br4)‘6 (TTT = tetrathiotetracene) (2.490 A) and in [Cu(PPh3)Br]4’7 (2.495 A).
Hydrogen bonds and intermolecular contacts
As described in the Experimental section, the hydrogen atoms linked to Nz and N4 were found in difference Fourier maps and no peak at a distance of about 1 A of N,, N3 was visible. Furthermore, the bond distances in the pymtH ring agree with this assignment (Table 2) and are close to those
found in most pyrimidine-2-thione complexes.‘8T’9 As shown in Fig. 2, intramolecular hydrogen bonds between the bromide atoms (Br,, BrJ and the HN,, HN4 hydrogen occur (Br, . . . N2 = 3.205(7) A, Br2-N, = 3.300(8) A). These hydrogen bonds are of different strength, as shown also by the leastsquares planes formed by the Cu, Br, S, C, N atoms (Table 4). Furthermore, short van der Waals contacts exist between one H-C hydrogen atom of the pymtH ring of one molecule, with the bromide atom of the other molecule, giving rise to an almost dimeric molecule (Br,-C(83) = 3.67(l) A, Br,---C(41) = 3.462(9) A). Then the strongest hydrogen bond to one bromide atom is associated with the weakest van der Waals contact. As a consequence of this dimer formation, Br,, Br2, NZ, N.,, C(83), C(41) form a plane within 0.6 A (Table 4). Finally, no other intermolecular contact is smaller than 3.5 A.
Heterocyclic thiones with Cu’Br
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IR spectra
IR spectra, in the region 4000-250 cm- ‘, provide information concerning the mode of coordination. Some selected bands and their assignments are given in Table 5. The solid-state IR spectra of complexes studied, exhibit the dominance of the thione form of the ligands investigated with the presence of v(NH) bands at 318G-3 130 cm- ‘,2%22the absence of any evidence for v(SH) bands in the 2500-2600 cm-’ region,23-24 and the production of characteristic “thioamide” bands.23 All the pymtH ligands are bonded to the metal through the sulphur atom, as shown by the shifts of the “thioamide” bands observed by comparing the IR spectra of the complexes with those of the free ligands. Of the four “thioamide” bands, those showing the most significant changes upon coordination are (III) and (IV). “Thioamide(II1)” undergoes downward shifts ranging from 10 to 60 cm- ‘. “Thioamide(IV)” shows similar behaviour, although here, the shifts are generally greater (3& 100 cm-‘), and the absorptions are in many cases pertly masked by strong triphenylphosphine bands. In agreement with the X-ray crystal structure there is no positive evidence that in the complexes discussed here, the ligands behave as bidentate. In fact, “thioamide(1)” occurred at the same wavenumbers, or showed small (+ 5 cm- ‘) shifts, signifying that the ligands are not N-bonded to the metal. The N-H stretching frequency in the complexes tends to lie at a lower wavenumber than in the free ligands, but the shifts of this band are small, suggesting that the nitrogen atoms are not involved in bonding. 24 The directions of the shifts in the position of all the bands in the spectra of the complexes are the same, indicating that the binding pattern in all the complexes must be similar. The monodentate nature of the ligands is further confirmed by the presence of a band around 350 cm-’ , which is assigned to the v(Cu-S) vibration. 25 Electronic and NMR spectra
The UV-vis spectra of the compounds in CHC13 solutions, as expected, show only two absorption bands at 31&360 and 24&280 nm, which can be assigned as intraligand transitions. The ‘H NMR spectra of the complexes in CDC13 solution also provided proof that ligands are (NH) protonated. The absence of any evidence for the thiol (SH) proton (6 3-5 ppm) and the presence of a peak for the NH group at N IO-14 ppm (sometimes very broad) indicate the thione tautomer as the dominant species in the complexes studied.
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Table 4. Equation and distances from the least-squares planes Plane 1
0.6087x
-0.5544y
-0.5676~
Brr -0.120
Cu, 0.173
S, 0.170
C 0.0;4
Plane 2
0.3576x
- 0.0576~
-0.9321~
Br, -0.234
Cu, 0.360
S2 -0.348
Plane 3
0.6953x
+ 0.0044y
-0.7187~
= -4.4328
Br, 0.372
Br, 0.584
N* 0.049
N, -0.310
C -0.Y40
Angles between
l-2 l-3 2-3
= 8.9479 N* 0.094 = 8.0309
C 0.07690
Br,” 0.119
N4 0.162
C‘%* -0.555
Cu,” 0.587
38.9” 23.3” 34.0
“Atom not included in the least-squares calculations.
Table 5. Selected NMR and IR spectroscopic data
Compound I II III IV V VI VII VIII IX X
‘H NMR &N-H) (ppm) 13.6 0 a 11.2 13.1 ll 14.1 11.3 13.2+9.0 11.8
v(N---H) 3150 3180 3140 3140 3140 3140 3135 3133 3130 3160
“Thioamide(I1)” 1305 1310 1320 1305 1285 1250 1325 1310 1330 1300
IR (cm- ‘) “Thioamide(II1)” 1025 1020 1020 1022 1030 990 1000 1025 1020 1025
v(Cu-S) 360 h 355 b b 255 b 360 360 380
“No associated N-H activity was observed. bNo absorption attributable to Cu-S vibration was observed.
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