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C–S bond cleavage in pyridylmethylthioether systems promoted by oxorhenium(V) ion
Inorganic Chemistry Communications 12 (2009) 1112–1115
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C–S bond cleavage in pyridylmethylthioether systems promoted by oxorhenium(V) ion Biswajit Das a, Sandipan Sarkar a, Ennio Zangrando b, Pabitra Chattopadhyay a,* a b
Department of Chemistry, Burdwan University, Golapbag, Burdwan 713 104, India Dipartimento di Scienze Chimiche, Via Licio Giorgieri 1, 34127 Trieste, Italy
a r t i c l e
i n f o
Article history: Received 26 June 2009 Accepted 14 August 2009 Available online 4 September 2009 Keywords: C–S bond cleavage Oxorhenium(V) ion Crystal structure
a b s t r a c t C–S bond cleavage in pyridylmethylthioether systems promoted by oxorhenium(V) ion has been established performing the reaction of 1,2-bis(2-pyridylmethylthio)ethane(BPT1), 1,3-bis(2-pyridyl-methylthio)propane(BPT2) and 3,4-bis(2-pyridylmethylthio)-5-methyltoluene (BPT3) with Bu4N[ReOCl4] in dry alcoholoic medium. In case of BPT1 and BPT2, new 2-(2-pyridylmethylthio)ethane-1-thiol (L1H) and 3(2-pyridylmethylthio)propane-1-thiol (L2H) ligand, respectively were formed in situ through cleavage of one C–S(thioether) bond, resulting in the neutral oxorhenium(V) complexes of formulation [ReO(L1)Cl2] (1a) and [ReO(L2)Cl2] (1b); where as in case of BPT3, binary oxorhenium(V) complex of 3,4-dimercapto-toluene ligand (L3H2), formulated as Bu4N[ReO(L3)2] (1c) through cleavage of two C–S(thioether) bonds. The presence of picolinic acid, as by-product in the filtrates of the C–S bond cleavage reactions in dry alcohol, was detected by treatment of copper(II) salts and GC–MS techniques. But in hydrated alcoholic medium no C–S bond cleavage induced by ReO(V) ion occurred in any of the BPT systems rather the conversion of ReO(V) into perrhenate salt was observed; this reaction mixture, in turn on reaction with copper(II) nitrate trihydrate salt, produce [Cu(BPT)Cl]ReO4 (2) type complexes. The solidstate structures of complexes 1a and 2a were established by X-ray crystallography. Ó 2009 Elsevier B.V. All rights reserved.
The transition-metal-mediated cleavage of a C–S bond has been paid considerable attention due to its importance in synthetic chemistry, [1–3] petrochemical hydrodesulfurization, [4–11] biorganic and bioinorganic chemistry [12–15]. Several examples of C–S bond cleavage within organic molecules by different metal ions [16–21] were reported, considering the fundamental urgency of this aspect. To the best of our knowledge, there are reports of C–S bond cleavage within oxorhenium(V) complexes of organic moiety comprising C–S fragment [19–21] and within thiophenes by Re2(CO)10 through hydrogenation, [22] but the present results are unprecedented. In fact we have found that the reaction under mild conditions between oxorhenium(V) ion and pyridylthioether systems cleaves C–S bond selectively, giving thiolato oxorhenium(V) products, although earlier reports showed that the C–S bond in 1,2-bis(2-pyridylmethylthio)ethane (BPT1) and 1,3-bis(2pyridylmethylthio)propane (BPT2), and in similar type of organic compounds having N,S donor environment is quite stable towards hydrolysis in the presence of transition metal ions and different metal complexes have been reported so far [23–37]. Treatment of 1,2-bis(2-pyridylmethylthio)ethane (BPT1) or 1,3bis(2-pyridyl-methylthio)propane (BPT2) with Bu4N[ReOCl4] in dry
* Corresponding author. Tel.: +91 342 2558545; fax: +91 342 25304502. E-mail address: [email protected] (P. Chattopadhyay). 1387-7003/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2009.08.035
methanol/ethanol medium led to the formation of oxorhenium(V) complexes of 2-(2-pyridylmethylthio)ethane-1-thiol (L1H) and 3(2-pyridylmethylthio)propane-1-thiol (L2H) formed in situ from BPT1 and BPT2, respectively, due to the cleavage of one C–S(thioether) bond. As a result, [ReO(L1)Cl2] (1a) and [ReO(L2)Cl2] (1b) were obtained in good yield vide Scheme 1 [38]. X-ray diffraction analysis of complex (1a) [39] reveals that the metal has a severely distorted six-co-ordinate octahedral environment, being surrounded by the terminal oxo ligand, two chlorides and the monobasic tridentate NSS ligand (see Fig. 1). The latter presents a facial configuration with sulphur donors trans to chlorides. Assuming the equatorial plane defined by S2Cl2 donors, the metal is displaced by 0.73 Å from this mean plane in the direction of the oxo ligand. The O–Re–Cl and O–Re–S angles (range 93.5(2)– 104.4(2)°) and the corresponding N–Re–Cl and N–Re–S angles values, all smaller than 90° (range 74.40(16)–87.24(16)°), are indicative of an umbrella-shaped conformation of the equatorial plane towards the py ring. The dihedral angle formed by the ReCl2 and ReS2 planes is 25.2(1)°. The Re–S1(thiol) bond length of 2.287(2) Å is significantly shorter than the Re–S2(thioether) one, of 2.374(2) Å, to which corresponds a reversed trend for the trans located Re–Cl bond distances, 2.425(2) and 2.355(2) Å. The Re– S(thioether) and the trans Re-Cl distance values are comparable to those found in the [(2-(2-pyridylmethylthio)-aniline)ReOCl2] complex [40] of 2.379(4) and 2.333(4) Å, respectively.
B. Das et al. / Inorganic Chemistry Communications 12 (2009) 1112–1115
( )
( )
n
S
S
N
N
Bu4N[ReOCl 4]
S
1113
n S O
Dry MeOH/EtOH
N
Re Cl Cl
BPT 1 (n=0) and BPT 2 (n=1)
BPT + Bu4N[ReOClO4 ]
[ReO(L 1)Cl 2] (1a), n = 0; [ReO(L 2)Cl 2] (1b), n = 1,
Reflux Dry MeOH/EtOH
[ReO(L1)Cl2] (1a); [ReO(L2)Cl2] (1b);
Scheme 1.
Fig. 1. An ORTEP view (40% thermal ellipsoid probability) of [ReO(L1)Cl2] (1a) with atom numbering scheme. Relevant bond distances (Å) and angles (°): Re–O(1) 1.676(6), Re–S(1) 2.287(2), Re–S(2) 2.374(2), Re–Cl(1) 2.425(2), Re–Cl(2) 2.355(2), Re–N(1) 2.383(6), O(1)–Re–S(1) 104.4(2), O(1)–Re–S(2) 94.7(2), O(1)– Re–Cl(1) 93.5(2), O(1)–Re–Cl(2) 104.1(2); O(1)–Re–N(1); 165.7(3), S(1)–Re–Cl(1) 161.99(8), S(1)–Re–Cl(2) 86.77(9).S(1)–Re–S(2) 87.25(8), S(1)–Re–N(1) 84.68(16), S(2)–Re– Cl(1) 92.93(8), S(2)–Re–Cl(2) 161.13(8), S(2)–Re–N(1) 74.40(16), Cl(1)–Re–Cl(2) 87.33(9), Cl(1)–Re–N(1) 78.05(16), Cl(2)–Re–N(1) 87.24(16).
The Re–N(py) bond, trans to the doubly bonded oxygen, is slightly lengthened [2.383(6) Å], as expected [40–42]. In fact in two 2-mercaptomethylpyridine-ReO complexes [43], the Re–N bond (trans to alkoxy donor) were found to be 2.158(6) and 2.227(6) Å. The Re@O bond distance, of 1.676(6) Å, is in agreement with the values found in the cited complexes [40–43]. In the complex the two five-membered rings in the coordination sphere, defined by the S–C–C–S and N–C–C–S atoms of the tridentate ligand and the metal ion, exhibit a dihedral angle of 49.6(10)° and 25.5(11)°, respectively.
S N
S N
Bu4N[ReOCl4] Dry MeOH/EtOH
On the other hand, treatment of 3,4-bis(2-pyridylmethylthio)5-methyltoluene (BPT3) with oxorhenium(V) ion under the same conditions led to the formation of a binary oxorhenium(V) complex of 3,4-dimercapto-toluene (L3H2) structurally characterized as Bu4N[ReO(L3)2] (1c). The cleavage of both the C–S (thioether) bonds occurring in BPT3 is sketched in Scheme 2. The mononuclear oxorhenium(V) complex 1c was isolated in pure form and characterized by physicochemical and spectroscopic methods along with X-ray crystallographic studies. We do not include the crystal data of 1c since the structure having the same cell and composition has been reported by us, as obtained through the direct reaction of 3,4-dimercapto-toluene (L3H2) with Bu4N[ReOCl4] [44]. The structural results for 1a (extended to 1b) evidenced the unexpected cleavage of one of the C–S bond within the BPT1 and BPT2 molecules during metal complexation. This result is quite different from the phenomenon occurred in BPT3 during ReO(V) ion complexation where both C–S bonds result cleaved. This feature may be ascribed to the presence of the aromatic ring between sulphur atoms in the BPT3 backbone. The reduced electron density expected on sulphur in BPT3 with respect to that in BPT1/BPT2 induces the CH2-S bond to be more susceptible to cleavage, being correspondingly the methylene group (–CH2) more positive. GC–MS studies were carried out to examine the possible byproducts resulting from the reaction of the organic ligands (BPT1, BPT2 and BPT3) with Bu4N[ReOCl4] in dry methanol/ethanol by injecting the solutions after removal of the precipitated oxorhenium(V) complexes. The mass spectra signals suggest the presence of picolinic acid (picH) in the mixture: m/z peaks at 124 and 106 are attributable to the [picolinic acid + H+] and [{picolinic acid + H+} H2O] ion, respectively [45]. But these signals are missing in the control experiment spectra where the ligands were not submitted to reaction with Bu4N[ReOCl4]. It has also been noticed that the treatment of the filtrates obtained from these reaction mixtures with copper(II) perchlorate or nitrate salts led to the formation of the copper(II) complex with picolinate, [Cu(pic)2] [46]. When this type of reactions was carried out under the same conditions in hydrated methanol/ethanol, no oxorhenium(V) complex of BPT was obtained but rather a perrhenate salt due to the
Bu4N
S O
S
Re S
S
Bu4N[ReO(L3)2] (1c) BPT 3 Scheme 2.
1114
B. Das et al. / Inorganic Chemistry Communications 12 (2009) 1112–1115
BPT + Bu4N[ReOCl4]
Reflux MeOH/EtOH (not dried)
Cu(NO3)2, 3H2O
Mixture
Slow evaporation
[Cu(BPT)Cl]ReO4 (2)
Bu4NReO4
Scheme 3.
hydrolysis of oxorhenium(V), and the organic moiety remains unaffected. To confirm the presence of the unchanged organic species in the aqueous methanol/ethanol reaction mixture, copper(II) nitrate trihydrate salt was added followed by a stirring of 30 min, obtaining the correspondent copper(II) complex with perrhenate as counter anion, [Cu(BPT)Cl]ReO4 (2) (see Scheme 3). The complexes were characterized by physicochemical and spectroscopic tools [47] along with the single crystal X-ray structural characterization of one of these, [Cu(BPT1)Cl]ReO4 (2a). X-ray crystallographic data analysis [48] shows that the complex 2a posses five coordinate environment with CuN2S2Cl (Fig. 2) and it is isomorphous with the reported copper(II) complex [Cu(BPT1)Cl]ClO4 [29]. The complex 2a is distorted trigonal-bipyramidal where two pyridinic-N atoms are in the axial position while the two thioether-S and chlorine form the equatorial plane. Comparing all the bond lengths and bond angles of 2a with the reported one, it may be suggested that the geometry around the Cu(II) centre is slightly distinct from that in [Cu(BPT1)Cl]ClO4. Due to the slight lower largest angle around the copper centre (b: N(1)–Cu– N(2) = 171.05(16)°) and the considerable higher second-largest one (a: Cl(1)–Cu-S(1) = 142.40(6)°) in comparison to the corresponding b and a respectively in [Cu(BPT1)Cl]ClO4, its angular structural index parameter (trigonality index) evaluated by the two largest angles (a < b) as s = (b a)/60 in five-coordinated geometry [34] is 0.478 which is comparatively lower than that in [Cu(BPT1)Cl]ClO4 (s = 0.619). From these observations (vide Scheme 3) it is clear that the water plays a role in the conversion of ReO(V) into ReO4 in the hydrated alcoholic medium; whereas it is evident the involvement of
oxohenium(V) ion in the C–S bond cleavage in the processes indicated in Schemes 1 and 2 and carried out in dry methanol/ethanol. In summary, the results presented in this study indicate that in dry methanol/ethanol medium cleavage of C–S bond promoted by oxorhenium(V) ion occurred in pyridylmethylthioether ligands (BPT). During reaction with Bu4N[ReOCl4], BPT ligands undergo the cleavage of one C–S bond, and the aromatic ring containing BPT derivative of both the C–S bonds to form in all cases oxorhenium(V) complexes with new organic ligands. On the other hand, in hydrated alcoholic medium pyridylmethylthioether systems remain unchanged, with conversion of ReO(V) into ReO4 , later confirmed by the formation of [Cu(BPT)Cl]ReO4 complexes by addition of copper(II) nitrate. In fact from earlier studies we were aware that BPTs are quite stable towards copper(II) nitrate or perchlorate [29,31] but not towards chloride salts [46]. Acknowledgements Financial support from Department of Science and Technology (DST), New Delhi, India is gratefully acknowledged. E. Zangrando thanks MIUR-Rome, PRIN No. 2005035123 for financial support. Appendix A. Supplementary data CCDC 714738 and 737398 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.inoche.2009.08.035. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
Fig. 2. An ORTEP view of [Cu(BPT1)Cl]ReO4 (2a). Relevant bond distances (Å) and angles (°): Cu–S(1) 2.4148(15), Cu–S(2) 2.4623(15), Cu–N(1) 1.999(4), Cu–N(2) 1.993(4), Cu–Cl(1) 2.2551(15), S(1)–Cu–S(2) 91.40(5), N(1)–Cu–N(2) 171.05(16), N(1)–Cu–S(1) 84.05(11), N(1)–Cu–S(2) 89.24(11), N(2)–Cu–S(1) 89.97(13), N(2)– Cu–S(2) 84.25(12), Cl(1)–Cu–S(1) 142.40(6), Cl(1)–Cu–S(2) 126.20(6), N(1)–Cu– Cl(1) 95.62(11), N(2)–Cu–Cl(1) 93.18(12).
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[39]
[40] [41] [42] [43] [44] [45] [46]
[47]
[48]
1115
NMR (d, ppm) in CDCl3: 8.81 (d, 1H), 8.08–7.60 (m, 3H), 4.26 (s, 2H), 3.06 (t, 2H), 2.51 (t, 2H), 1.98 (m, 2H). Conductivity (Ko, ohm 1 cm2 mol 1) in CH3CN: 70. UV–vis (, dm3 mol 1 cm 1): 99 at 561 nm in CH2Cl2. Electrochemistry in CH3CN at 298 K: only one quasi-reversible voltammogram for ReV/ReVI couple at 1.18 V (Epa, 1.35 V, Epc, 1.01 V) (w.r.t. SCE). Yield: 50–55%. Crystallographic data for 1a: Formula: C8H10Cl2NOReS2; Fw: 457.39; triclinic, space group P1; a = 7.340(3), b = 7.846(3), c = 12.136(4) Å; a = 77.75(2); b = 81.26(3), c = 64.73(3)°; V = 616.2(4) Å3; Z = 2; q = 2.465 g/cm3; F(0 0 0) = 428; l = 10.604 mm 1; R1 = 0.0428, wR2 = 0.1133; GOF = 1.058. P. Chattopadhyay, Y.-H. Chiu, J.-M. Lo, C.-S. Chung, T.-H. Lu, Appl. Radiat. Isot. 52 (2000) 217. S. Fortin, A.L. Beauchamp, Inorg. Chem. 39 (2000) 4886. S. Tzanopoulou, I.C. Pirmettis, G. Patsis, C. Raptopoulou, A. Terzis, M. Papadopoulos, M. Pelecanou, Inorg. Chem. 45 (2006) 902. J.W. Babich, W. Graham, F.J. Femia, Qing Dong, M. Barzana, K. Ferrill, A.J. Fischman, J. Zubieta, Inorg. Chim. Acta 323 (2000) 23. B. Das, S. Sarkar, E. Zangrando, P. Chattopadhyay, J. Coord. Chem., submitted for publication. U. Riegert, G. Heiss, P. Fischer, A. Stolz, J. Bacteriol. 180 (1998) 2849. In another type of reactions with copper(II) ion performed in our laboratory, we observed the cleavage of both C–S bonds in BPT1 BPT2 and BPT3 during the reaction with copper(II) chloride but not with copper(II)nitrate or perchlorate salts [29,31]. So, here copper(II) chloride has not been used to isolate the product [Cu(BPT1)Cl]ReO4 (2) in order to unfold the fact of the existence of the unreacted BPT ligands. [Cu(BPT1)Cl]ReO4 (2a): C14H16ClCuN2O4ReS2: Anal. Found: C, 26.71; H, 2.51; N, 4.46; Calc.: C, 26.87; H, 2.56; N, 4.48 (%). IR (cm 1): mC@N, 1478; mC–S, 760, mReO4 , 910; mCu–Cl, 320. Conductivity (Ko, ohm 1 cm2 mol 1) in acetonitrile: 145. Yield: 70–75%. [Cu(BPT2)Cl]ReO4 (2b): C15H18ClCuN2O4ReS2: Anal. Found: C, 27.93; H, 2.89; N, 4.43; Calc.: C, 28.16; H, 2.81; N, 4.38 (%). IR (cm 1): mC@N, 1468; mC–S, 758, mReO4 , 912; mCu–Cl, 318. Conductivity (Ko, ohm 1 cm2 mol 1) in acetonitrile: 141. Yield: 70–72%. [Cu(BPT3)Cl]ReO4 (2c): C19H18ClCuN2O4ReS2: Anal. Found: C, 32.99; H, 2.69; N, 4.21; Calc.: C, 33.18; H, 2.62; N, 4.07 (%). IR (cm 1): mC@N, 1478; mC–S, 762, mReO4 , 912; mCu–Cl, 318. Conductivity (Ko, ohm 1 cm2 mol 1) in acetonitrile: 144. Yield: 68–70%. Crystallographic data for 2a: Formula: C14H16ClCu N2O4ReS2; Fw: 625.60; triclinic, space group P1; a = 8.414(3), b = 10.512(3), c = 11.392(4) Å; a = 76.720(4), b = 75.603(4), c = 72.035(4)°; V = 915.5(5) Å3; Z = 2; q = 2.269 g/cm3; F(0 0 0) = 598, l = 23.512 mm 1; R1 = 0.0318, wR2 = 0.0820; GOF = 1.080.
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C–S bond cleavage in pyridylmethylthioether systems promoted by oxorhenium(V) ion Biswajit Das a, Sandipan Sarkar a, Ennio Zangrando b, Pabitra Chattopadhyay a,* a b
Department of Chemistry, Burdwan University, Golapbag, Burdwan 713 104, India Dipartimento di Scienze Chimiche, Via Licio Giorgieri 1, 34127 Trieste, Italy
a r t i c l e
i n f o
Article history: Received 26 June 2009 Accepted 14 August 2009 Available online 4 September 2009 Keywords: C–S bond cleavage Oxorhenium(V) ion Crystal structure
a b s t r a c t C–S bond cleavage in pyridylmethylthioether systems promoted by oxorhenium(V) ion has been established performing the reaction of 1,2-bis(2-pyridylmethylthio)ethane(BPT1), 1,3-bis(2-pyridyl-methylthio)propane(BPT2) and 3,4-bis(2-pyridylmethylthio)-5-methyltoluene (BPT3) with Bu4N[ReOCl4] in dry alcoholoic medium. In case of BPT1 and BPT2, new 2-(2-pyridylmethylthio)ethane-1-thiol (L1H) and 3(2-pyridylmethylthio)propane-1-thiol (L2H) ligand, respectively were formed in situ through cleavage of one C–S(thioether) bond, resulting in the neutral oxorhenium(V) complexes of formulation [ReO(L1)Cl2] (1a) and [ReO(L2)Cl2] (1b); where as in case of BPT3, binary oxorhenium(V) complex of 3,4-dimercapto-toluene ligand (L3H2), formulated as Bu4N[ReO(L3)2] (1c) through cleavage of two C–S(thioether) bonds. The presence of picolinic acid, as by-product in the filtrates of the C–S bond cleavage reactions in dry alcohol, was detected by treatment of copper(II) salts and GC–MS techniques. But in hydrated alcoholic medium no C–S bond cleavage induced by ReO(V) ion occurred in any of the BPT systems rather the conversion of ReO(V) into perrhenate salt was observed; this reaction mixture, in turn on reaction with copper(II) nitrate trihydrate salt, produce [Cu(BPT)Cl]ReO4 (2) type complexes. The solidstate structures of complexes 1a and 2a were established by X-ray crystallography. Ó 2009 Elsevier B.V. All rights reserved.
The transition-metal-mediated cleavage of a C–S bond has been paid considerable attention due to its importance in synthetic chemistry, [1–3] petrochemical hydrodesulfurization, [4–11] biorganic and bioinorganic chemistry [12–15]. Several examples of C–S bond cleavage within organic molecules by different metal ions [16–21] were reported, considering the fundamental urgency of this aspect. To the best of our knowledge, there are reports of C–S bond cleavage within oxorhenium(V) complexes of organic moiety comprising C–S fragment [19–21] and within thiophenes by Re2(CO)10 through hydrogenation, [22] but the present results are unprecedented. In fact we have found that the reaction under mild conditions between oxorhenium(V) ion and pyridylthioether systems cleaves C–S bond selectively, giving thiolato oxorhenium(V) products, although earlier reports showed that the C–S bond in 1,2-bis(2-pyridylmethylthio)ethane (BPT1) and 1,3-bis(2pyridylmethylthio)propane (BPT2), and in similar type of organic compounds having N,S donor environment is quite stable towards hydrolysis in the presence of transition metal ions and different metal complexes have been reported so far [23–37]. Treatment of 1,2-bis(2-pyridylmethylthio)ethane (BPT1) or 1,3bis(2-pyridyl-methylthio)propane (BPT2) with Bu4N[ReOCl4] in dry
* Corresponding author. Tel.: +91 342 2558545; fax: +91 342 25304502. E-mail address: [email protected] (P. Chattopadhyay). 1387-7003/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2009.08.035
methanol/ethanol medium led to the formation of oxorhenium(V) complexes of 2-(2-pyridylmethylthio)ethane-1-thiol (L1H) and 3(2-pyridylmethylthio)propane-1-thiol (L2H) formed in situ from BPT1 and BPT2, respectively, due to the cleavage of one C–S(thioether) bond. As a result, [ReO(L1)Cl2] (1a) and [ReO(L2)Cl2] (1b) were obtained in good yield vide Scheme 1 [38]. X-ray diffraction analysis of complex (1a) [39] reveals that the metal has a severely distorted six-co-ordinate octahedral environment, being surrounded by the terminal oxo ligand, two chlorides and the monobasic tridentate NSS ligand (see Fig. 1). The latter presents a facial configuration with sulphur donors trans to chlorides. Assuming the equatorial plane defined by S2Cl2 donors, the metal is displaced by 0.73 Å from this mean plane in the direction of the oxo ligand. The O–Re–Cl and O–Re–S angles (range 93.5(2)– 104.4(2)°) and the corresponding N–Re–Cl and N–Re–S angles values, all smaller than 90° (range 74.40(16)–87.24(16)°), are indicative of an umbrella-shaped conformation of the equatorial plane towards the py ring. The dihedral angle formed by the ReCl2 and ReS2 planes is 25.2(1)°. The Re–S1(thiol) bond length of 2.287(2) Å is significantly shorter than the Re–S2(thioether) one, of 2.374(2) Å, to which corresponds a reversed trend for the trans located Re–Cl bond distances, 2.425(2) and 2.355(2) Å. The Re– S(thioether) and the trans Re-Cl distance values are comparable to those found in the [(2-(2-pyridylmethylthio)-aniline)ReOCl2] complex [40] of 2.379(4) and 2.333(4) Å, respectively.
B. Das et al. / Inorganic Chemistry Communications 12 (2009) 1112–1115
( )
( )
n
S
S
N
N
Bu4N[ReOCl 4]
S
1113
n S O
Dry MeOH/EtOH
N
Re Cl Cl
BPT 1 (n=0) and BPT 2 (n=1)
BPT + Bu4N[ReOClO4 ]
[ReO(L 1)Cl 2] (1a), n = 0; [ReO(L 2)Cl 2] (1b), n = 1,
Reflux Dry MeOH/EtOH
[ReO(L1)Cl2] (1a); [ReO(L2)Cl2] (1b);
Scheme 1.
Fig. 1. An ORTEP view (40% thermal ellipsoid probability) of [ReO(L1)Cl2] (1a) with atom numbering scheme. Relevant bond distances (Å) and angles (°): Re–O(1) 1.676(6), Re–S(1) 2.287(2), Re–S(2) 2.374(2), Re–Cl(1) 2.425(2), Re–Cl(2) 2.355(2), Re–N(1) 2.383(6), O(1)–Re–S(1) 104.4(2), O(1)–Re–S(2) 94.7(2), O(1)– Re–Cl(1) 93.5(2), O(1)–Re–Cl(2) 104.1(2); O(1)–Re–N(1); 165.7(3), S(1)–Re–Cl(1) 161.99(8), S(1)–Re–Cl(2) 86.77(9).S(1)–Re–S(2) 87.25(8), S(1)–Re–N(1) 84.68(16), S(2)–Re– Cl(1) 92.93(8), S(2)–Re–Cl(2) 161.13(8), S(2)–Re–N(1) 74.40(16), Cl(1)–Re–Cl(2) 87.33(9), Cl(1)–Re–N(1) 78.05(16), Cl(2)–Re–N(1) 87.24(16).
The Re–N(py) bond, trans to the doubly bonded oxygen, is slightly lengthened [2.383(6) Å], as expected [40–42]. In fact in two 2-mercaptomethylpyridine-ReO complexes [43], the Re–N bond (trans to alkoxy donor) were found to be 2.158(6) and 2.227(6) Å. The Re@O bond distance, of 1.676(6) Å, is in agreement with the values found in the cited complexes [40–43]. In the complex the two five-membered rings in the coordination sphere, defined by the S–C–C–S and N–C–C–S atoms of the tridentate ligand and the metal ion, exhibit a dihedral angle of 49.6(10)° and 25.5(11)°, respectively.
S N
S N
Bu4N[ReOCl4] Dry MeOH/EtOH
On the other hand, treatment of 3,4-bis(2-pyridylmethylthio)5-methyltoluene (BPT3) with oxorhenium(V) ion under the same conditions led to the formation of a binary oxorhenium(V) complex of 3,4-dimercapto-toluene (L3H2) structurally characterized as Bu4N[ReO(L3)2] (1c). The cleavage of both the C–S (thioether) bonds occurring in BPT3 is sketched in Scheme 2. The mononuclear oxorhenium(V) complex 1c was isolated in pure form and characterized by physicochemical and spectroscopic methods along with X-ray crystallographic studies. We do not include the crystal data of 1c since the structure having the same cell and composition has been reported by us, as obtained through the direct reaction of 3,4-dimercapto-toluene (L3H2) with Bu4N[ReOCl4] [44]. The structural results for 1a (extended to 1b) evidenced the unexpected cleavage of one of the C–S bond within the BPT1 and BPT2 molecules during metal complexation. This result is quite different from the phenomenon occurred in BPT3 during ReO(V) ion complexation where both C–S bonds result cleaved. This feature may be ascribed to the presence of the aromatic ring between sulphur atoms in the BPT3 backbone. The reduced electron density expected on sulphur in BPT3 with respect to that in BPT1/BPT2 induces the CH2-S bond to be more susceptible to cleavage, being correspondingly the methylene group (–CH2) more positive. GC–MS studies were carried out to examine the possible byproducts resulting from the reaction of the organic ligands (BPT1, BPT2 and BPT3) with Bu4N[ReOCl4] in dry methanol/ethanol by injecting the solutions after removal of the precipitated oxorhenium(V) complexes. The mass spectra signals suggest the presence of picolinic acid (picH) in the mixture: m/z peaks at 124 and 106 are attributable to the [picolinic acid + H+] and [{picolinic acid + H+} H2O] ion, respectively [45]. But these signals are missing in the control experiment spectra where the ligands were not submitted to reaction with Bu4N[ReOCl4]. It has also been noticed that the treatment of the filtrates obtained from these reaction mixtures with copper(II) perchlorate or nitrate salts led to the formation of the copper(II) complex with picolinate, [Cu(pic)2] [46]. When this type of reactions was carried out under the same conditions in hydrated methanol/ethanol, no oxorhenium(V) complex of BPT was obtained but rather a perrhenate salt due to the
Bu4N
S O
S
Re S
S
Bu4N[ReO(L3)2] (1c) BPT 3 Scheme 2.
1114
B. Das et al. / Inorganic Chemistry Communications 12 (2009) 1112–1115
BPT + Bu4N[ReOCl4]
Reflux MeOH/EtOH (not dried)
Cu(NO3)2, 3H2O
Mixture
Slow evaporation
[Cu(BPT)Cl]ReO4 (2)
Bu4NReO4
Scheme 3.
hydrolysis of oxorhenium(V), and the organic moiety remains unaffected. To confirm the presence of the unchanged organic species in the aqueous methanol/ethanol reaction mixture, copper(II) nitrate trihydrate salt was added followed by a stirring of 30 min, obtaining the correspondent copper(II) complex with perrhenate as counter anion, [Cu(BPT)Cl]ReO4 (2) (see Scheme 3). The complexes were characterized by physicochemical and spectroscopic tools [47] along with the single crystal X-ray structural characterization of one of these, [Cu(BPT1)Cl]ReO4 (2a). X-ray crystallographic data analysis [48] shows that the complex 2a posses five coordinate environment with CuN2S2Cl (Fig. 2) and it is isomorphous with the reported copper(II) complex [Cu(BPT1)Cl]ClO4 [29]. The complex 2a is distorted trigonal-bipyramidal where two pyridinic-N atoms are in the axial position while the two thioether-S and chlorine form the equatorial plane. Comparing all the bond lengths and bond angles of 2a with the reported one, it may be suggested that the geometry around the Cu(II) centre is slightly distinct from that in [Cu(BPT1)Cl]ClO4. Due to the slight lower largest angle around the copper centre (b: N(1)–Cu– N(2) = 171.05(16)°) and the considerable higher second-largest one (a: Cl(1)–Cu-S(1) = 142.40(6)°) in comparison to the corresponding b and a respectively in [Cu(BPT1)Cl]ClO4, its angular structural index parameter (trigonality index) evaluated by the two largest angles (a < b) as s = (b a)/60 in five-coordinated geometry [34] is 0.478 which is comparatively lower than that in [Cu(BPT1)Cl]ClO4 (s = 0.619). From these observations (vide Scheme 3) it is clear that the water plays a role in the conversion of ReO(V) into ReO4 in the hydrated alcoholic medium; whereas it is evident the involvement of
oxohenium(V) ion in the C–S bond cleavage in the processes indicated in Schemes 1 and 2 and carried out in dry methanol/ethanol. In summary, the results presented in this study indicate that in dry methanol/ethanol medium cleavage of C–S bond promoted by oxorhenium(V) ion occurred in pyridylmethylthioether ligands (BPT). During reaction with Bu4N[ReOCl4], BPT ligands undergo the cleavage of one C–S bond, and the aromatic ring containing BPT derivative of both the C–S bonds to form in all cases oxorhenium(V) complexes with new organic ligands. On the other hand, in hydrated alcoholic medium pyridylmethylthioether systems remain unchanged, with conversion of ReO(V) into ReO4 , later confirmed by the formation of [Cu(BPT)Cl]ReO4 complexes by addition of copper(II) nitrate. In fact from earlier studies we were aware that BPTs are quite stable towards copper(II) nitrate or perchlorate [29,31] but not towards chloride salts [46]. Acknowledgements Financial support from Department of Science and Technology (DST), New Delhi, India is gratefully acknowledged. E. Zangrando thanks MIUR-Rome, PRIN No. 2005035123 for financial support. Appendix A. Supplementary data CCDC 714738 and 737398 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.inoche.2009.08.035. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
Fig. 2. An ORTEP view of [Cu(BPT1)Cl]ReO4 (2a). Relevant bond distances (Å) and angles (°): Cu–S(1) 2.4148(15), Cu–S(2) 2.4623(15), Cu–N(1) 1.999(4), Cu–N(2) 1.993(4), Cu–Cl(1) 2.2551(15), S(1)–Cu–S(2) 91.40(5), N(1)–Cu–N(2) 171.05(16), N(1)–Cu–S(1) 84.05(11), N(1)–Cu–S(2) 89.24(11), N(2)–Cu–S(1) 89.97(13), N(2)– Cu–S(2) 84.25(12), Cl(1)–Cu–S(1) 142.40(6), Cl(1)–Cu–S(2) 126.20(6), N(1)–Cu– Cl(1) 95.62(11), N(2)–Cu–Cl(1) 93.18(12).
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B. Das et al. / Inorganic Chemistry Communications 12 (2009) 1112–1115 [23] S.E. Livingstone, J.D. Nolan, Aust. J. Chem. 23 (1970) 1553. [24] G.R. Brubaker, J.N. Brown, M.K. Yoo, R.A. Kinsey, T.M. Kutchan, E.A. Mottel, Inorg. Chem. 18 (1979) 299. [25] B. Adhikary, S. Liu, C.R. Lucas, Inorg. Chem. 32 (1993) 5957. [26] B. Adhikary, C.R. Lucas, Inorg. Chem. 31 (1994) 1376. [27] T. Pandiyan, S. Bernes, C. Duran de Bazua, Acta Crystallogr. Sect. C 55 (1999) 318. [28] H. Nekola, D. Wang, C. Gru1ning, J. Ga1tjens, A. Behrens, D. Rehder, Inorg. Chem. 41 (2002) 2379. [29] S. Sarkar, A. Patra, M.G.B. Drew, E. Zangrando, P. Chattopadhyay, Polyhedron 28 (2009) 1. [30] A. Patra, S. Sarkar, M.G.B. Drew, E. Zangrando, P. Chattopadhyay, Polyhedron 28 (2009) 1261 and refs. therein. [31] S. Sarkar, H. Paul, M.G.B. Drew, E. Zangrando, P. Chattopadhyay, J. Mol. Struct. 933 (2009) 126. [32] H.A. Goodwin, F. Lions, J. Am. Chem. Soc. 82 (1960) 5013. [33] P.J.M.W.L. Birker, J. Helder, G. Henkel, B. Krebs, J. Reedijk, Inorg. Chem. 21 (1982) 357. [34] A.W. Addison, T.N. Rao, J. Reedijk, J. van Rijn, G.C. Verschoor, J. Chem. Soc., Dalton Trans. (1984) 1349. [35] E. Bouwman, A. Burik, J.C.T. Hove, W.L. Driessen, J. Reedijk, Inorg. Chim. Acta 150 (1988) 125. [36] E. Bouwman, R. Day, W.L. Driessen, W. Tremel, B. Krebs, J.S. Wood, J. Reedijk, Inorg. Chem. 27 (1988) 4614. [37] W.G. Haanstra, W.L. Driessen, R.A.G. de Graaff, J. Reedijk, Y.F. Wang, C.H. Stam, Inorg. Chim. Acta 186 (1991) 215. [38] BPT1 (276.0 mg, 1.0 mmol) or BPT2 (292.0 mg, 1.0 mmol) was mixed with 1.0 mmol of Bu4NReOCl4, and stirred for half an hour in dry methanol/ethanol media followed by reflux for 1 h, obtaining a green precipitate by filtration. The pure crystallized products were achieved from dichloromethane solution and suitable single crystals for X-ray crystallography of 1a were collected from a CH2Cl2/hexane solution (1:2). [ReO(C8H10NS2)Cl2] (1a): C8H10Cl2NOReS2: Anal. Found: C, 20.99; H, 2.18; N, 3.06; Calc.: C, 21.09; H, 2.12; N, 2.99 (%). IR (cm 1): mC@N, 1476;mC–S, 761, mRe@O, 960; mRe–N 532; mRe–Cl, 323. 1H NMR (d, ppm) in CDCl3: 8.63 (d, 1H), 7.71–7.18 (m, 3H), 4.25 (s, 2H), 2.95 (t, 2H), 2.58 (t, 2H). Conductivity (Ko, ohm 1 cm2 mol 1) in CH3CN: 80. UV–vis (, dm3 mol 1 cm 1): 154 at 556 nm in CH2Cl2. Electrochemistry in CH3CN at 298 K: one quasi-reversible voltammogram for ReV/ReVI couple at 1.23 V (Epa, 1.30 V, Epc, 1.15 V) (w.r.t. SCE). Yield: 75–80%. [ReO(C9H12NS2)Cl2] (1b): C9H12Cl2NOReS2: Anal. Found: C, 22.91; H, 2.54; N, 2.97; Calc.: C, 23.01; H, 2.52; N, 2.92 (%). IR (cm 1): mC@N, 1465; mC–S, 760, mRe@O, 957; mRe–N 530. 1H
[39]
[40] [41] [42] [43] [44] [45] [46]
[47]
[48]
1115
NMR (d, ppm) in CDCl3: 8.81 (d, 1H), 8.08–7.60 (m, 3H), 4.26 (s, 2H), 3.06 (t, 2H), 2.51 (t, 2H), 1.98 (m, 2H). Conductivity (Ko, ohm 1 cm2 mol 1) in CH3CN: 70. UV–vis (, dm3 mol 1 cm 1): 99 at 561 nm in CH2Cl2. Electrochemistry in CH3CN at 298 K: only one quasi-reversible voltammogram for ReV/ReVI couple at 1.18 V (Epa, 1.35 V, Epc, 1.01 V) (w.r.t. SCE). Yield: 50–55%. Crystallographic data for 1a: Formula: C8H10Cl2NOReS2; Fw: 457.39; triclinic, space group P1; a = 7.340(3), b = 7.846(3), c = 12.136(4) Å; a = 77.75(2); b = 81.26(3), c = 64.73(3)°; V = 616.2(4) Å3; Z = 2; q = 2.465 g/cm3; F(0 0 0) = 428; l = 10.604 mm 1; R1 = 0.0428, wR2 = 0.1133; GOF = 1.058. P. Chattopadhyay, Y.-H. Chiu, J.-M. Lo, C.-S. Chung, T.-H. Lu, Appl. Radiat. Isot. 52 (2000) 217. S. Fortin, A.L. Beauchamp, Inorg. Chem. 39 (2000) 4886. S. Tzanopoulou, I.C. Pirmettis, G. Patsis, C. Raptopoulou, A. Terzis, M. Papadopoulos, M. Pelecanou, Inorg. Chem. 45 (2006) 902. J.W. Babich, W. Graham, F.J. Femia, Qing Dong, M. Barzana, K. Ferrill, A.J. Fischman, J. Zubieta, Inorg. Chim. Acta 323 (2000) 23. B. Das, S. Sarkar, E. Zangrando, P. Chattopadhyay, J. Coord. Chem., submitted for publication. U. Riegert, G. Heiss, P. Fischer, A. Stolz, J. Bacteriol. 180 (1998) 2849. In another type of reactions with copper(II) ion performed in our laboratory, we observed the cleavage of both C–S bonds in BPT1 BPT2 and BPT3 during the reaction with copper(II) chloride but not with copper(II)nitrate or perchlorate salts [29,31]. So, here copper(II) chloride has not been used to isolate the product [Cu(BPT1)Cl]ReO4 (2) in order to unfold the fact of the existence of the unreacted BPT ligands. [Cu(BPT1)Cl]ReO4 (2a): C14H16ClCuN2O4ReS2: Anal. Found: C, 26.71; H, 2.51; N, 4.46; Calc.: C, 26.87; H, 2.56; N, 4.48 (%). IR (cm 1): mC@N, 1478; mC–S, 760, mReO4 , 910; mCu–Cl, 320. Conductivity (Ko, ohm 1 cm2 mol 1) in acetonitrile: 145. Yield: 70–75%. [Cu(BPT2)Cl]ReO4 (2b): C15H18ClCuN2O4ReS2: Anal. Found: C, 27.93; H, 2.89; N, 4.43; Calc.: C, 28.16; H, 2.81; N, 4.38 (%). IR (cm 1): mC@N, 1468; mC–S, 758, mReO4 , 912; mCu–Cl, 318. Conductivity (Ko, ohm 1 cm2 mol 1) in acetonitrile: 141. Yield: 70–72%. [Cu(BPT3)Cl]ReO4 (2c): C19H18ClCuN2O4ReS2: Anal. Found: C, 32.99; H, 2.69; N, 4.21; Calc.: C, 33.18; H, 2.62; N, 4.07 (%). IR (cm 1): mC@N, 1478; mC–S, 762, mReO4 , 912; mCu–Cl, 318. Conductivity (Ko, ohm 1 cm2 mol 1) in acetonitrile: 144. Yield: 68–70%. Crystallographic data for 2a: Formula: C14H16ClCu N2O4ReS2; Fw: 625.60; triclinic, space group P1; a = 8.414(3), b = 10.512(3), c = 11.392(4) Å; a = 76.720(4), b = 75.603(4), c = 72.035(4)°; V = 915.5(5) Å3; Z = 2; q = 2.269 g/cm3; F(0 0 0) = 598, l = 23.512 mm 1; R1 = 0.0318, wR2 = 0.0820; GOF = 1.080.