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Synthesis of cyclopentadienyl ruthenium complexes containing 5-membered N-heterocyclic thiolates
Inorganica Chimica Acta 363 (2010) 4134–4139
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Synthesis of cyclopentadienyl ruthenium complexes containing 5-membered N-heterocyclic thiolates Deeb Taher a, Mousa Al-Noaimi b, Sahar Mohammad c, John F. Corrigan d, Daniel G. MacDonald d, Mohammad El-khateeb c,* a
Department of Chemistry, Tafila Technical University, Tafila, Jordan Chemistry Department, Faculty of Science, The Hashemite University, Zarqa, Jordan Chemistry Department, Jordan University of Science and Technology, Irbid 22110, Jordan d Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7 b c
a r t i c l e
i n f o
Article history: Received 12 January 2010 Received in revised form 2 May 2010 Accepted 12 May 2010 Available online 20 May 2010 Keywords: Ruthenium Heterocyclic-thiolates 5-Memberd N-containing heterocycles Structure Chelates Sulfur Complexes
a b s t r a c t Mononuclear ruthenium–thiolate complexes of structural type CpRu(PPh3)2SR (1) [R = 2-imidazolyl (a), 1-methylimidazolyl (b), 5-methyl-1,3,5-thiadiazolyl (c) and 5-methyl-4H-1,2,4-triazolyl (d)] are accessible from the reaction of CpRu(PPh3)2Cl with the corresponding thiolate anions. Reaction of CpRu(PPh3)2Cl with the heterocyclic-thiolate anions in the presence of the bisphosphine ligands affords CpRu(P–P)SR [P–P = bis(diphenylphosphino)methane; dppm (2), bis(diphenylphosphino)ethane; dppe (3)]. If CO gas was bubbled through a THF solution of 1b, the complex CpRu(PPh3)(CO)S(C4N2H5) (4b) is produced. These ruthenium–heterocyclic thiolate complexes have been characterized by elemental analysis, spectroscopy (IR, 1H, 31P{1H} NMR and MS) and cyclic voltammetry for some samples. The solid-state structures of 3a and 3b are determined by single-crystal X-ray structure analysis. Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction Transition metal complexes containing sulfur-ligands have attracted much attention due to their central roles in biological systems [1–4] and catalysis [5–7]. Of particular interest are the ruthenium–sulfur complexes which are known to exhibit good catalytic activity toward hydrodesulfurization process [8–17]. Several ruthenium thiolates have been synthesized to model the active sites of metal-sulfide catalysts of the hydrodesulfurization process [18–21]. The interaction of thiophene or its analogues with ruthenium has been investigated as models for the hydrodesulfurization of crude oil [13,14,22]. In our lab, we studied the interaction of heterocyclic thiolates with ruthenium [23–25]. The reaction of CpRu(PPh3)2Cl with 2-pyridine thiolate or 2-pyrimidine thiolate produced the complexes CpRu(PPh3)(j2S,N-SR) (R = C5H4N, C5H3N2) where the heterocyclic thiolato ligand is bonded to Ru in a chelating manner through both S and N atoms [23]. On the other hand, the same Ru-species reacted with heterocyclic-thiolate anions (RS = 2-mercaptobenzimidazolyl, 2-mercaptobenzoxazolyl
* Corresponding author. Tel.: +962 2 7201000; fax: +962 2 7201071. E-mail address: [email protected] (M. El-khateeb). 0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2010.05.022
and 2-mercaptobenzthiazolyl, thiophene, or furan-thiolates) to give CpRu(PPh3)2(jS-SR) where the thiolate is bonded to Ru in a monodentate fashion [24]. Treatment of CpRu(PPh3)(j2S,N-SR) or CpRu(PPh3)2(jS-SR) with CO or NOBF4 gave the mixed carbonylphosphine complexes CpRu(PPh3)(CO)(jS-SR) or the nitrosyl salts [CpRu(PPh3)(NO)(jS-HSR)]+ [23,24]. The bis(phosphine)-complexes CpRu(P–P)(jS-SR) {P–P = Ph2PCH2CH2PPh2 (dppe), Ph2PCH2PPh2 (dppm) were prepared by the reaction of CpRu(PPh3)2Cl, thiolato anions and P–P ligands [23–25]. As part of investigation dealing with the study of heterocyclic thiolate complexes of ruthenium, we report herein the synthesis and structural characterization of ruthenium complexes with Ncontaining five-membered ring thiolates. These thiolates act as monodentate ligands.
2. Experimental 2.1. Materials All reactions and manipulations were carried out in an inert atmosphere of dinitrogen using standard Schlenk techniques. Solvents were purified by distillation (dichloromethane: P2O5; n-hexane, toluene, tetrahydrofuran: sodium/benzophenone).
D. Taher et al. / Inorganica Chimica Acta 363 (2010) 4134–4139
2.2. Synthesis of CpRu(PPh3)2SR (1) Heterocyclic thiol (1.0 mmol) was dissolved in 50 mL of THF and cooled to 78 °C. Methyllithium (1.6 M in diethylether, 0.70 mL, 1.12 mmol) was dropwise added. The cooling bath was removed after 10 min and the reaction mixture was stirred for 15 min at room temperature. CpRu(PPh3)2Cl (0.50 g, 0.68 mmol) was added and the resulting mixture was refluxed for 4 h. The volatiles were removed under vacuum and the remaining solid was dissolved in toluene (10.0 mL) and filtered over celite to ensure removal of LiCl, the supernatant was taken and concentrated under vacuum to about 4.0 mL, then 30.0 mL of cooled hexane was added, an orange-yellow precipitate was formed which was collected by removing the mother liquor and washed several times with cooled hexane and dried in vacuum. 2.2.1. CpRu(PPh3)2S(C3N2H3) (1a) Yield = 60% (0.30 g, 0.41 mmol). M.p.: 119–120 °C. EI-MS: m/z (rel. int. %) 790 (10) [M+], 691 (25) [M+C3N2H3S], 528 (48) [M+PPh3], 429 (35) [M+C3N2H3PPh3]. 1H NMR (C6D6): d 2.30 (bs, 1H, NH), 4.68 (s, 5H, Cp), 6.29 (bs, 1H, C3N2H3), 6.95 (m, 18H, PPh3), 7.31 (bs, 1H, C3N2H3), 7.64 (m, 12H, PPh3). 31P NMR (C6D6): d 42.51. Anal. Calc. for C44H38N2P2RuSTHF (%): C, 66.88; H, 5.38; S, 3.72; N, 3.25. Found: C, 65.73; H, 4.98; S, 3.15; N, 3.01%. 2.2.2. CpRu(PPh3)2S(C4N2H5) (1b) Yield = 73% (0.40 g, 0.50 mmol). M.p.: 93–95 °C. EI-MS: m/z (rel. int. %) 805 (6) [M+], 691 (36) [M+C4N2H5S], 542 (56) [M+PPh3]. 1 H NMR (C6D6): d 2.91 (s, 3H, CH3), 4.20 (s, 5H, Cp), 5.47 (bs, 1H, C3N2H2), 5.83 (bs, 1H, C4N2H3), 6.92 (m, 18H, PPh3), 7.63 (m, 12H, PPh3). 1H NMR (C6D6): d: 42.14. Anal. Calc. for C45H40N2P2RuS (%): C, 67.23; H, 5.02; S, 3.99; N, 3.48. Found: C, 67.15; H, 4.91; S, 3.50; N, 3.00%. 2.2.3. CpRu(PPh3)2S(C3N2SH3) (1c) Yield = 80% (0.45 g, 0.54 mmol). M.p.: 123–125 °C. EI-MS: m/z (rel. int. %) 691 (38) (M+C3N2H3S2), 429 (63) (M+C3N2H3S2PPh3). 1 H NMR (C6D6): d 2.14 (s, 3H, CH3), 4.73 (s, 5H, Cp), 6.92 (m, 18H, PPh3), 7.63 (m, 12H, PPh3). 31P NMR (, C6D6): d 42.09. Anal. Calc. for C44H38N2P2RuS2 (%): C, 64.30; H, 4.66; S, 7.80; N, 3.41. Found: C, 63.61; H, 4.52; S, 7.75; N, 3.28%. 2.2.4. CpRu(PPh3)2S(C3N3H4) (1d) Yield = 85% (0.46 g, 0.58 mmol). M.p.: 138–140 °C. EI-MS: m/z (rel. int. %) 691 (45) [M+C3N3H4S], 429 (56) [M+C3N3H4SPPh3]. 1 H NMR (C6D6): d 2.74 (s, 3H, CH3), 4.77 (s, 5H, Cp), 6.94 (m, 18H, PPh3), 7.45 (m, 6H, PPh3), 7.50 (s, 1H, C2N3H). 31P NMR (C6D6): d 42.34. Anal. Calc. for C44H39N3P2RuS (%): C, 65.66; H, 4.88; S, 3.98; N, 5.22. Found: C, 65.11; H, 4.63; S, 3.26; N, 5.01%. 2.3. Synthesis of CpRu(dppm)SR (2), CpRu(dppe)SR (3) Heterocyclic thiols (1.0 mmol) was dissolved in THF (50 mL) and cooled to 78 °C. Methyllithium (1.6 in diethylether, 0.70 mL, 1.12 mmol) was added dropwise. The cooling bath was removed after 10 min and the reaction was stirred for a further 15 min at room temperature. CpRu(PPh3)2Cl (0.50 g, 0.68 mmol) and bis(diphenylphosphino)methane or bis(diphenylphosphino)ethane (0.68 mmol) were added and the resulting mixture was refluxed for 4 h. The volatiles were removed under vacuum and the remaining solid was dissolved in toluene (10.0 mL). The resulting solution was filtered over celite to ensure removal of LiCl. The supernatant was taken and concentrated under vacuum to about 4.0 mL then 30.0 mL of cooled hexane was added, a light yellow precipitate was formed which was collected by removing the mother liquor and recrystallized from THF/hexane.
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2.3.1. CpRu(dppm)S(C3N2H3) (2a) Yield = 87% (0.38 g, 0.59 mmol). M.p.: 144–145 °C. EI-MS: m/z (rel. int. %) 651 (93) [M+], 551 (100) [M+C3N2H3S]. 1H NMR (C6D6): d 4.30 (m, 1H, Ph2PCH2), 4.66 (m, 1H, Ph2PCH2), 5.12 (s, 5H, Cp), 5.81 (bs, 1H, NH), 6.99 (m, 12H, PPh2), 7.14 (bs, 1H, C3N2H3), 7.31 (bs, 1H, C3N2H3), 7.51 (m, 8H, PPh3). 31P NMR (C6D6): d 13.00. Anal. Calc. for C33H30N2P2RuSTHF (%): C, 61.48; H, 5.44; S, 4.44; N, 3.88. Found: C, 61.03; H, 4.98; S, 4.02; N, 3.13%. 2.3.2. CpRu(dppm)S(C4N2H5) (2b) Yield 80% (0.36 g, 0.54 mmol). M.p.: 213–215 °C. EI-MS: m/z (rel. int. %) 665 (90) [M+], 551 (93) [M+C4N2H5S]. 1H NMR (C6D6): d 3.02 (s, 3H, CH3), 4.52 (m, 1H, Ph2PCH2), 4.80 (m, 1H, Ph2PCH2), 5.30 (s, 5H, Cp), 6.90 (m, 12H, PPh2), 6.99 (bs, 1H, C3N2H2), 7.01 (bs, 1H, C3N2H2), 7.57 (m, 8H, PPh2). 31P NMR (C6D6): d 15.23. Anal. Calc. for C34H32N2P2RuS (%): C, 61.53; H, 4.86; S, 4.22; N, 4.83. Found: C, 60.52; H, 4.08; S, 3.90; N, 4.15%. 2.3.3. CpRu(dppm)S(C3N2SH3) (2c) Yield = 60% (0.28 g, 0.41 mmol). M.p.: 173–175 °C. EI-MS: m/z (rel. int. %) 682 (98) [M+], 550 (100) [M+C3N2H3S2]. 1H NMR (C6D6): d 2.06 (s, 3H, CH3), 4.38 (m, 1H, Ph2PCH2), 4.54 (m, 1H, Ph2PCH2), 5.05 (s, 5H, Cp), 6.82 (m, 12H, PPh2), 7.53 (m, 8H, PPh2). 31P NMR (C6D6): d 15.01. Anal. Calc. for C33H30N2P2RuS2 (%): C, 58.14; H, 4.44; S, 9.41; N, 4.11%. Found: C, 57.15; H, 3.92; S, 8.62; N, 3.78%. 2.3.4. CpRu(dppm)S(C3N3H4) (2d) Yield = 65% (0.29 g, 0.44 mmol). M.p.: 163–165 °C. EI-MS: m/z (rel. int. %) 666 (88) [M+], 551 (95) [M+C3N3H4S]. 1H NMR (C6D6): d 3.05 (s, 1H, CH3), 4.44 (m, 1H, Ph2PCH2), 4.69 (m, 1H, Ph2PCH2), 5.23 (s, 5H, Cp), 6.89 (m, 12H, PPh2), 7.37 (s, 1H, C2N3H), 7.55 (m, 8H, PPh3). 31P NMR (C6D6): d 15.84. Anal. Calc. for C33H31N3P2RuS (%): C, 59.63; H, 4.70; S, 4.82; N, 6.32. Found: C, 58.70; H, 4.23; S, 4.23; N, 6.01%. 2.3.5. CpRu(dppe)S(C3N2H3) (3a) Yield = 90% (0.41 g, 0.61 mmol). M.p.: 133–135 °C. EI-MS: m/z (rel. int. %) 665 (95) [M+], 565 (100) [M+C3N2H3S]. 1H NMR (C6D6): d 1.95 (m, 2H, PPh2CH2), 2.49 (m, 2H, PPh2CH2), 4.96 (s, 5H, Cp), 5.36 (bs, 1H, NH), 6.95 (m, 12H, PPh2), 7.06 (bs, 1H, C3N2H3), 7.08 (bs, 1H, C3N2H3), 7.77 (m, 8H, PPh2). 31P NMR (C6D6): d 81.51. Anal. Calc. for C34H32N2P2RuS: C, 61.53; H, 4.86; S, 4.83; N, 4.22. Found: C, 60.91; H, 4.18; S, 4.22; N, 3.91%. 2.3.6. CpRu(dppe)S(C4N2H5) (3b) Yield = 80% (0.37 g, 0.54 mmol). M.p.: 128–130 °C. EI-MS: m/z (rel. int. %) 679 (99) [M+], 565 (100) [M+C4N2H5S]. 1H NMR (C6D6): d 2.02 (m, 2H, PPh2CH2), 2.36 (m, 2H, PPh2CH2), 2.93 (s, 3H, CH3), 5.20 (s, 5H, Cp), 5.48 (bs, 1H, C3N2H2), 5.80 (bs, 1H, C3N2H2), 7.01 (m, 12H, PPh2), 7.67 (m, 8H, PPh2). 31P NMR (C6D6): d 80.80. Anal. Calc. for C35H34N2P2RuS (%): C, 62.03; H, 5.06; S, 4.73; N, 4.13. Found: C, 61.69; H, 5.60; S, 4.36; N, 3.90%. 2.3.7. CpRu(dppe)S(C3N2SH3) (3c) Yield = 85% (0.40 g, 0.58 mmol). M.p.: 124–125 °C. EI-MS: m/z (rel. int. %) 565 (100) [M+C3N2H3S2]. 1H NMR (C6D6): d 1.98 (m, 2H, PPh2CH2), 2.16 (s, 3H, CH3), 2.48 (m, 2H, PPh2CH2), 4.99 (s, 5H, Cp), 6.94 (m, 12H, PPh2), 7.75 (m, 8H, PPh2). 31P NMR (C6D6): d 80.79. Anal. Calc. for C34H32N2P2RuS2THF (%): C, 59.44; H, 5.25; S, 8.35; N, 3.65% Found: C, 58.51; H, 5.05; S, 7.65; N, 3.49%. 2.3.8. CpRu(dppe)S(C3N3H4) (3d) Yield = 85% (0.39 g, 0.58 mmol). M.p.: 158–160 °C. EI-MS: m/z (rel. int. %) 679 (98) [M+], (100) [M+C3N2H4S]. 1H NMR (acetoned6): d 2.54 (m, 2H, PPh2CH2), 2.59 (m, 2H, PPh2CH2), 4.99 (s, 5H, Cp), 7.27 (m, 12H, PPh2), 7.50 (s, 1H, C2N3H), 7.79 (m, 8H, PPh2). 1H
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NMR (C6D6): d 81.37. Anal. Calc. for C34H33N3P2RuS: C, 60.17; H, 4.90; S, 4.72; N, 6.19% Found: C, 59.38; H, 4.81; S, 4.12; N, 5.92%.
2.4. Synthesis of CpRu(PPh3)(CO)S(C4N2H5) (4b) CO gas was bubbled through a THF solution (30 mL) of complex 1b (0.40 g, 0.50 mmol) for 30 min at room temperature. The mixture was stirred under CO-atmosphere for 3 h. The solution was concentrated under vacuum to about 4.0 mL then 30.0 mL of cooled hexane was added, a yellow precipitate was formed which was collected by removing the mother liquor and washed several Table 1 Crystal data and structure refinement for 3a and 3b.
CCDC number Chemical formula Molecular weight Crystal system Space group Unit cell dimension a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Dcalc (g cm3) F(0 0 0) Crystal size (mm) Reflections measured Unique reflections Data/restraints/parameters Goodness-of-fit (GOF) on F2 R1a, wR2a [I P 2r(I)] R1a, wR2a Maximum and minimum peak in final Fourier map (e Å3) a
3a
3b
728102 C34H32N2P2RuS 663.69 orthorhombic Pna2(1)
728101 C36H36Cl2N2P2RuS 762.64 triclinic P1
20.7860(10) 14.5939(7) 9.5541(4) Å 90 90 90 2898.2(2) 4 1.521 1360 0.30 0.18 0.10 12 255 5452 5452/1/361 0.909 0.0628, 0.1391 0.1220, 0.1758 0.858, 1.317
9.2741(3) 10.6145(3) 18.3048(7) 96.983(2) 101.6070(10) 106.760(2) 1658.82(10) 2 1.527 780 0.28 0.18 0.15 33 137 9702 9702/0/393 0.972 0.0585, 0.1247 0.1219, 0.1520 1.138, 1.686
2.5. Instrumentation FT-IR spectra were recorded with a Perkin–Elmer FT-IR 1000 spectrometer (KBr disks or CH2Cl2 solution). NMR spectra were recorded on a Bruker Avance 400 MHz spectrometer, operating in the fourier-transform mode. 1H NMR spectra were recorded at 400 MHz (relative to C6D6, d 7.16, acetone-d6, 2.05). 31P{1H} NMR spectra were recorded at 161.2 MHz in C6D6 with P(OMe)3 as external standard (d 139.0, relative to 85% H3PO4). Mass spectra were performed on a Finnigan MAT 8200 instrument. Melting points were determined using analytically pure samples, sealed off in nitrogen-purged capillaries on a Gallenkamp MFB 595 010 melting point apparatus. Microanalyses were performed by the Institute of Organic and Macromolecular Chemistry, FSU-Jena, Jena, Germany. CpRu(PPh3)2Cl was prepared by published procedures [26]. All other chemicals were purchased from commercial suppliers and were used as received. Cyclic voltammetric studies were performed in dichloromethane using a BAS 100 electrochemical workstation. Three electrodes were utilized in this system, gold working electrode; platinum flag counter electrode, and a silver wire pseudo-reference electrode. For ease of comparison, all potentials are converted to the ferrocene–ferrocenium couple as a reference (E0 = 0.00 V, DE = 125 mV) [27–29]. The cell temperature was maintained at 25.0 ± 0.1 °C. Tetrabutylammonium tetrafluoroborate was used as the supporting electrolyte. 2.6. Crystallography X-ray structural analyses were carried out on an Enraf-Nonius Kappa CCD single-crystal X-ray diffractometer. Table 1 summarizes
x ¼ 1=r2 ðF 2o Þ þ ð0:0598PÞ2 where P ¼ ðF 2o þ 2F 2c Þ=3.
Ru Ph3P
times with cooled n-hexane and dried in vacuum. Yield = 60% (0.17 g, 0.30 mmol). M.p.: 181–183 °C. 1H NMR (C6D6): d 3.02 (s, 3H, CH3), 4.92 (s, 5H, Cp), 6.45 (d, 1H, JH–H = 2 Hz, C4N2H5), 6.90 (m, 9H, PPh3), 7.21 (d, 1H, JH–H = 2 Hz, C4N2H5), 7.57 (m, 6H, PPh3). 31P NMR (C6D6): d 57.36. IR (CH2Cl2): 1950 cm1. Anal. Calc. for C28H25N2OPRuS (%): C, 59.04.53; H, 4.42; S, 5.63; N, 4.92. Found: C, 58.88; H, 4.32; S, 5.23; N, 4.85%.
Cl
+
+
Ru
RSLi Ph3P
SR
PPh3
LiCl
PPh3
(1) CO
P-P
Ru Ph2P
SR
+
PPh3
Ru Ph3P
PPh2
PPh3
4b
N N H
+
CO
P-P = dppm (2), dppe (3)
RS =
SR
NMe S (a)
N
S
(b) Me
N
N S
Scheme 1. Synthesis of complexes.
N S (c)
N N Me
S (d)
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the structural data of 3a and 3b. Data were corrected for Lorentz and polarization effects. The SHELXTL (G.M. Sheldrick, Madison, WI) program package was used to solve (direct methods) and refine the structures. All non-hydrogen atoms, with the exception of disordered carbon centers, were refined with anisotropic thermal parameters. Hydrogen atoms were included as riding on their respective carbon atoms. 3. Results and discussion 3.1. Synthesis The heterocyclic-thiolato complexes, CpRu(PPh3)2SR (1) [R = imidazolyl: C3N2H3 (a), 1-methylimidazolyl: C4N2H5 (b), 5methyl-1,3,5-thiadiazolyl: C3N2SH3 (c) and 5-methyl-4H-1,2,4triazolyl C3N3H4 (d)] are accessible in a two-step synthesis protocol: selective metallation of the heterocyclic thiol by using excess of MeLi, followed by the reaction of the generated heterocyclic anion with Ru-chloride (Scheme 1). The work-up includes removal of LiCl, accomplished by dissolving the complexes in toluene and filtration over celite. Complexes 1a–d can be precipitated from toluene solution by slow addition of n-hexane. In the presence of the bisphospine-ligands (dppm, dppe), the same reaction (CpRu(PPh3)2Cl + LiSR) gives the chelate complexes CpRu(dppm)SR (2) and CpRu(dppe)SR, (3) (Scheme 1). If CO gas is bubbled through a THF solution of 1b, the complex CpRu(PPh3)(CO)S(C4N2H5); 4b is produced in which a CO group replaced one PPh3 ligand (Scheme 1). The thiolato complexes 1–3 and 4b are air-stable solids but airsensitive in solution. They are yellow solids, isolated in 60–87% yield and are soluble in polar organic solvents. These complexes were characterized by elemental analysis and spectroscopy (IR, 1 H, 31P{1H} NMR and MS). The solid-state structures of 3a and 3b by X-ray diffraction are determined. The 1H NMR spectra of the thiolate complexes show a singlet in the ranges of 4.68–4.77, 4.96–5.20, 5.05–5.30 ppm and at 4.92 ppm characteristic for the Cp-ring protons of 1, 2, 3 and 4b, respectively. These ranges are consistent with the ranges observed for the alkyl or aryl thiolate complexes CpRu(L)(L’)SR (L = L0 = PPh3, ½ dppe, ½ dppm, L = PPh3, L0 = CO) [24,25,30–32]. The spectra of these complexes exhibit well-resolved resonance signals with the expected coupling pattern for each of the heterocyclic groups present in these compounds. Their 31P NMR spectra show a singlet in the ranges of 42.09–42.51, 13.00–15.84, 80.79–81.37 and at 57.36 ppm for complexes 1, 2, 3 and 4b, respectively. These ranges of the 31P NMR data are also similar to those found for the corresponding thiolates CpRu(L)(L0 )SR, thiocarboxylates [24,25,30–32] CpRu(L)(L0 )SCOR [33] and thiocarbonates CpRu(L)(L0 )SCO2R [34]. The IR spectrum of 4b displays a strong band at 1946 cm1 for the terminal carbonyl group bonded to ruthenium. This value is comparable to those reported for analogues ruthenium alkyl or aryl-thiolates [24,25,30–32]. The TOF-MS spectra of 1–3 and 4b show the molecular ion peak for most complexes. For compounds 1c, 1d and 2c, TOF-MS spectra show the highest peak as (M+SR). The base peak for complex 1 is found to be [CpRu(PPh3)2]+, for 2 is [CpRu(dppm)]+ and for 3 is [CpRu(dppe)]+. Further ions by loss of the phosphine groups are also observed. 3.2. Crystal structures The X-ray structures of 3a and 3b were determined by singlecrystal X-ray structure analysis. Single-crystals of these complexes could be obtained by slow vapor diffusion of n-pentane into a dichloromethane solution containing 3a and 3b at 25 °C. The structures of 3a and 3b are presented in Figs. 1 and 2, respectively. Se-
lected bond distances and angles of these complexes are summarized in Table 2. The structures of 3a and 3b consist of a simple complex formed by coordination of the 2-mercapto-1-imidazolyl or 2-mercapto-1-methylimidazolyl (3b) ligand to the CpRu(dppe) fragment. These complexes have a three-legged piano stool structure with the thiolate ligand and the two P-atoms of the dppe-ligand are the legs while the Cp ring (bonded to ruthenium in an g5 fashion) as its base. In both structures 3a and 3b, the planar five-membered ring is attached to the Ru-center by the sulfur atom with a Ru–S bond lengths of 2.416(2) and 2.4153(10) Å for 3a and 3b, respectively. These bond distances are similar for those
Fig. 1. X-ray structure of CpRu(dppe)S(C3N2H3) (3a).
Fig. 2. X-ray structure of CpRu(dppe)S(C4N2H5) (3b).
Table 2 Selected bond length (Å) and bond angle (°) for compounds 3a and 3b. 3a Ru(1)–C(33) Ru(1)–C(29) Ru(1)–C(30) Ru(1)–C(32) Ru(1)–C(31) Ru(1)–S(1) Ru(1)–P(1) Ru(1)–P(2) S(1)–C(25) P(1)–Ru(1)–S(1) P(2)–Ru(1)–S(1) P(1)–Ru(1)–P(2) Ru(1)–S(1)–C(25)
3b 2.195(10) 2.224(9) 2.235(10) 2.260(9) 2.276(8) 2.416(2) 2.260(2) 2.274(3) 1.761(9) 87.40(9) 87.82(9) 82.68(9) 109.6(3)
Ru(1)–C(1) Ru(1)–C(2) Ru(1)–C(3) Ru(1)–C(4) Ru(1)–C(5) Ru(1)–S(1) Ru(1)–P(1) Ru(1)–P(2) S(1)–C(32) P(1)–Ru(1)–S(1) P(2)–Ru(1)–S(1) P(2)–Ru(1)–P(1) Ru(1)–S(1)–C(32)
2.237(4) 2.231(4) 2.198(4) 2.209(4) 2.231(4) 2.4153(10) 2.2692(11) 2.2644(11) 1.747(4) 87.32(4) 85.27(4) 83.98(4) 111.64(14)
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Table 3 Cyclic voltammetry data of CpRu(PPh3)2SR complexes.a Compound CpRu(PPh3)2Cl CpRu(dppm)Cl CpRu(dppe)Cl 1c 1d 2c 2d 3c 3d
b Eox p (V)
0.028 0.164 0.161 0.189 0.102 0.221
Ered (V) p
DE (mV)
E1/2 (V)c
0.334 0.06 0.251 0.311 0.312 0.313
360 340 110 362 104 90 122 210 108
0.10 [36] 0.03 [36] 0.05 [36] 0.153 0.112 0.206 0.25 0.207 0.239
a Solvent dichloromethane, supporting electrolyte Bu4NBF4 (0.10 M), scan rate (0.1 V s1), gold disk working electrode, Pt-wire auxiliary electrode, reference electrode Ag at 25 °C. b The cathodic peak maximum. red c E1=2 ðVÞ ¼ ðEox p þ Ep Þ=2.
reported of the known Ru(II) thiolato complexes [23–25,30–32]. The Ru–P bond lengths in 3a (2.260(2), 2.274(3) Å) and in 3b (2.2692(11), 2.2644(11) Å) are close to the corresponding values of CpRu(dppe)SCOCO2Et (2.2772(6), 2.2527(6) Å) [35]. Angles around Ru-center are consistent with the usual distorted octahedral coordination usually found in these complexes. The bite angles [P–Ru–P] of the dppe-ligand are 82.68(9)° for (3a) and 83.98(4)° for (3b). The other two angles of the three-legged structure of 3a are P1–Ru–S = 87.40(9)° and P2–Ru–S = 87.82(9)°, and for compound 3b P1–Ru–S 87.40(9)° and P2–Ru–S = 87.82(9)°. These data are similar to those found in CpRu(dppe)SX (X = R, COR, CO2R) complexes indicating a distorted octahedral geometry around the Rucenter [24,25,30–35]. 3.3. Electrochemistry The electron-transfer behavior of the complexes in dichloromethane solution was examined by cyclic voltammetry and the corresponding results are summarized in Table 3. As a representa-
tive example, the cyclic voltammogram for complex 3c is shown in Fig. 3. Our concern here is the quasi-reversible single oxidation wave lies between 0.112 to 0.25 V. This wave is assigned to Ru(III/II) and was obtained from an average of anodic and cathodic peak potentials. On the CV timescale, complexes 1(c, d), 2(c, d) and 3(c, d) displayed chemically quasi-reversible oxidation processes at rate of 100 mV s1. The one electron nature of this oxidation has been verified by comparing its current height (ip) with that of the standard ferrocen/ferrocenium couple under identical experimental conditions. The redox potentials (E1/2) are independent of the various scan rates, supporting quasi-reversibility. Complexes 1(c, d), 2(c, d) and 3(c, d) also displayed one chemically irreversible oxidation process suggesting instability of the more highly oxidized state. However, the shift for Ru(III/II) couples is affected with the electron-donor capability of the corresponding ligands. For these complexes, the formal potentials decreased in the order dppm < dppe < (PPh3)2, although the total difference in oxidation potential spanning is relatively small (60 mV). These complexes are easily oxidized relative to the parent [CpRuL2Cl] analogue. The small cathodic shift for Ru(III/II) couples in the [CpRuL2SR] complexes can be explained by the difference in the electron density at the metal center influenced by the nature of the heterocyclic group. 4. Supplementary material CCDC 728102 and 728101 contain the supplementary crystallographic data for 3a and 3b. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Acknowledgement The financial support from the Deanship of Scientific Research, JUST (Grant No. 123/2007) is greatly acknowledged. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23]
Fig. 3. Cyclic voltammogram of 3c in a dichloromethane solution in the presence of Bu4NBF4 (0.10 M) as supporting electrolyte at 25 °C under nitrogen at a scan rate of 100 mV s1, positive going potential scan, potentials are referenced to the Cp2Fe/ Cp2Fe+ couple (Cp2Fe = (g5-C5H5)2Fe) as internal standard.
[24] [25] [26] [27]
E.I. Stiefel, Pure Appl. Chem. 70 (1998) 889. I. Bratsos, Inorg. Biochem. 102 (2008) 1120. P. Sengupta, R. Dinda, S. Ghosh, W.S. Sheldrick, Polyhedron 22 (2003) 447. J.S. Bair, R.G. Harrison, J. Org. Chem. 72 (2007) 6653. J. Carles Bayón, C. Claver, A.M. Masdeu-Bultó, Coord. Chem. Rev. 193–195 (1999) 73. X.-F. Hou, Y.-Q. Cheng, X. Wang, G.-X. Jin, J. Organomet. Chem. 690 (2005) 1855. M. Albrecht, R.A. Gossage, M. Lutz, A.L. Spek, G. van Koten, Chemistry 14 (2000) 1431. P.M. Boorman, G.F. Fait, G.K.W. Freeman, Polyhedron 8 (1989) 1762. K.E. Janak, J.M. Tanski, D.G. Churchill, G. Parkin, J. Am. Chem. Soc. 124 (2002) 4182. J.-F. Capon, P. Schollhammar, F.Y. Petillon, J. Talarmin, K.W. Muir, Organometallics 18 (1999) 2055. G.H. Spies, R.J. Angelici, Organometallics 6 (1987) 429. P.A. Vecchi, A. Ellern, R.J. Angelici, Organometallics 24 (2005) 2168. S.K. Bej, S.K. Maiky, U.T. Turager, Energ. Fuel. 18 (2004) 1227. G. McKinley, P.A. Vecchi, A. Ellern, R.J. Angelici, J. Chem. Soc., Dalton Trans. (2004) 788. R. Prins, V.H.J. DeBeer, G.A. Somorjai, Catal. Rev. 31 (1989) 1. P. Grange, Catal. Rev. 21 (1980) 135. M.D. Curtis, Appl. Organomet. Chem. 6 (2004) 429. P. Frediani, A. Salvini, S. Finocchiaro, J. Organomet. Chem. 584 (1999) 265. P.G. Jessop, B.R. James, Inorg. Chim. Acta 280 (1998) 75. J.G. Planas, M. Hirano, S. Komiya, Chem. Lett. 27 (1998) 123. R.Y. Shin, L.Y. Goh, Acc. Chem. Res. 39 (2006) 301. J.W. Hachgenei, R.J. Angelici, Angew. Chem., Ind. Ed. Engl. 26 (2003) 909. M. El-khateeb, K. Damer, H. Görls, W. Weigand, J. Organomet. Chem. 692 (2007) 2227. M. El-khateeb, Transition Met. Chem. 26 (2001) 267. M. El-khateeb, M. Al-Noaimi, Z. Al-Amawi, A. Roller, S. Shova, Inorg. Chim. Acta 361 (2008) 2957. M.I. Bruce, N.J. Windsor, Aust. J. Chem. 30 (1977) 1601. H. Strehlow, W. Knoche, H. Schneider, B. Bunsenges, Phys. Chem. 77 (1973) 760.
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Synthesis of cyclopentadienyl ruthenium complexes containing 5-membered N-heterocyclic thiolates Deeb Taher a, Mousa Al-Noaimi b, Sahar Mohammad c, John F. Corrigan d, Daniel G. MacDonald d, Mohammad El-khateeb c,* a
Department of Chemistry, Tafila Technical University, Tafila, Jordan Chemistry Department, Faculty of Science, The Hashemite University, Zarqa, Jordan Chemistry Department, Jordan University of Science and Technology, Irbid 22110, Jordan d Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7 b c
a r t i c l e
i n f o
Article history: Received 12 January 2010 Received in revised form 2 May 2010 Accepted 12 May 2010 Available online 20 May 2010 Keywords: Ruthenium Heterocyclic-thiolates 5-Memberd N-containing heterocycles Structure Chelates Sulfur Complexes
a b s t r a c t Mononuclear ruthenium–thiolate complexes of structural type CpRu(PPh3)2SR (1) [R = 2-imidazolyl (a), 1-methylimidazolyl (b), 5-methyl-1,3,5-thiadiazolyl (c) and 5-methyl-4H-1,2,4-triazolyl (d)] are accessible from the reaction of CpRu(PPh3)2Cl with the corresponding thiolate anions. Reaction of CpRu(PPh3)2Cl with the heterocyclic-thiolate anions in the presence of the bisphosphine ligands affords CpRu(P–P)SR [P–P = bis(diphenylphosphino)methane; dppm (2), bis(diphenylphosphino)ethane; dppe (3)]. If CO gas was bubbled through a THF solution of 1b, the complex CpRu(PPh3)(CO)S(C4N2H5) (4b) is produced. These ruthenium–heterocyclic thiolate complexes have been characterized by elemental analysis, spectroscopy (IR, 1H, 31P{1H} NMR and MS) and cyclic voltammetry for some samples. The solid-state structures of 3a and 3b are determined by single-crystal X-ray structure analysis. Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction Transition metal complexes containing sulfur-ligands have attracted much attention due to their central roles in biological systems [1–4] and catalysis [5–7]. Of particular interest are the ruthenium–sulfur complexes which are known to exhibit good catalytic activity toward hydrodesulfurization process [8–17]. Several ruthenium thiolates have been synthesized to model the active sites of metal-sulfide catalysts of the hydrodesulfurization process [18–21]. The interaction of thiophene or its analogues with ruthenium has been investigated as models for the hydrodesulfurization of crude oil [13,14,22]. In our lab, we studied the interaction of heterocyclic thiolates with ruthenium [23–25]. The reaction of CpRu(PPh3)2Cl with 2-pyridine thiolate or 2-pyrimidine thiolate produced the complexes CpRu(PPh3)(j2S,N-SR) (R = C5H4N, C5H3N2) where the heterocyclic thiolato ligand is bonded to Ru in a chelating manner through both S and N atoms [23]. On the other hand, the same Ru-species reacted with heterocyclic-thiolate anions (RS = 2-mercaptobenzimidazolyl, 2-mercaptobenzoxazolyl
* Corresponding author. Tel.: +962 2 7201000; fax: +962 2 7201071. E-mail address: [email protected] (M. El-khateeb). 0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2010.05.022
and 2-mercaptobenzthiazolyl, thiophene, or furan-thiolates) to give CpRu(PPh3)2(jS-SR) where the thiolate is bonded to Ru in a monodentate fashion [24]. Treatment of CpRu(PPh3)(j2S,N-SR) or CpRu(PPh3)2(jS-SR) with CO or NOBF4 gave the mixed carbonylphosphine complexes CpRu(PPh3)(CO)(jS-SR) or the nitrosyl salts [CpRu(PPh3)(NO)(jS-HSR)]+ [23,24]. The bis(phosphine)-complexes CpRu(P–P)(jS-SR) {P–P = Ph2PCH2CH2PPh2 (dppe), Ph2PCH2PPh2 (dppm) were prepared by the reaction of CpRu(PPh3)2Cl, thiolato anions and P–P ligands [23–25]. As part of investigation dealing with the study of heterocyclic thiolate complexes of ruthenium, we report herein the synthesis and structural characterization of ruthenium complexes with Ncontaining five-membered ring thiolates. These thiolates act as monodentate ligands.
2. Experimental 2.1. Materials All reactions and manipulations were carried out in an inert atmosphere of dinitrogen using standard Schlenk techniques. Solvents were purified by distillation (dichloromethane: P2O5; n-hexane, toluene, tetrahydrofuran: sodium/benzophenone).
D. Taher et al. / Inorganica Chimica Acta 363 (2010) 4134–4139
2.2. Synthesis of CpRu(PPh3)2SR (1) Heterocyclic thiol (1.0 mmol) was dissolved in 50 mL of THF and cooled to 78 °C. Methyllithium (1.6 M in diethylether, 0.70 mL, 1.12 mmol) was dropwise added. The cooling bath was removed after 10 min and the reaction mixture was stirred for 15 min at room temperature. CpRu(PPh3)2Cl (0.50 g, 0.68 mmol) was added and the resulting mixture was refluxed for 4 h. The volatiles were removed under vacuum and the remaining solid was dissolved in toluene (10.0 mL) and filtered over celite to ensure removal of LiCl, the supernatant was taken and concentrated under vacuum to about 4.0 mL, then 30.0 mL of cooled hexane was added, an orange-yellow precipitate was formed which was collected by removing the mother liquor and washed several times with cooled hexane and dried in vacuum. 2.2.1. CpRu(PPh3)2S(C3N2H3) (1a) Yield = 60% (0.30 g, 0.41 mmol). M.p.: 119–120 °C. EI-MS: m/z (rel. int. %) 790 (10) [M+], 691 (25) [M+C3N2H3S], 528 (48) [M+PPh3], 429 (35) [M+C3N2H3PPh3]. 1H NMR (C6D6): d 2.30 (bs, 1H, NH), 4.68 (s, 5H, Cp), 6.29 (bs, 1H, C3N2H3), 6.95 (m, 18H, PPh3), 7.31 (bs, 1H, C3N2H3), 7.64 (m, 12H, PPh3). 31P NMR (C6D6): d 42.51. Anal. Calc. for C44H38N2P2RuSTHF (%): C, 66.88; H, 5.38; S, 3.72; N, 3.25. Found: C, 65.73; H, 4.98; S, 3.15; N, 3.01%. 2.2.2. CpRu(PPh3)2S(C4N2H5) (1b) Yield = 73% (0.40 g, 0.50 mmol). M.p.: 93–95 °C. EI-MS: m/z (rel. int. %) 805 (6) [M+], 691 (36) [M+C4N2H5S], 542 (56) [M+PPh3]. 1 H NMR (C6D6): d 2.91 (s, 3H, CH3), 4.20 (s, 5H, Cp), 5.47 (bs, 1H, C3N2H2), 5.83 (bs, 1H, C4N2H3), 6.92 (m, 18H, PPh3), 7.63 (m, 12H, PPh3). 1H NMR (C6D6): d: 42.14. Anal. Calc. for C45H40N2P2RuS (%): C, 67.23; H, 5.02; S, 3.99; N, 3.48. Found: C, 67.15; H, 4.91; S, 3.50; N, 3.00%. 2.2.3. CpRu(PPh3)2S(C3N2SH3) (1c) Yield = 80% (0.45 g, 0.54 mmol). M.p.: 123–125 °C. EI-MS: m/z (rel. int. %) 691 (38) (M+C3N2H3S2), 429 (63) (M+C3N2H3S2PPh3). 1 H NMR (C6D6): d 2.14 (s, 3H, CH3), 4.73 (s, 5H, Cp), 6.92 (m, 18H, PPh3), 7.63 (m, 12H, PPh3). 31P NMR (, C6D6): d 42.09. Anal. Calc. for C44H38N2P2RuS2 (%): C, 64.30; H, 4.66; S, 7.80; N, 3.41. Found: C, 63.61; H, 4.52; S, 7.75; N, 3.28%. 2.2.4. CpRu(PPh3)2S(C3N3H4) (1d) Yield = 85% (0.46 g, 0.58 mmol). M.p.: 138–140 °C. EI-MS: m/z (rel. int. %) 691 (45) [M+C3N3H4S], 429 (56) [M+C3N3H4SPPh3]. 1 H NMR (C6D6): d 2.74 (s, 3H, CH3), 4.77 (s, 5H, Cp), 6.94 (m, 18H, PPh3), 7.45 (m, 6H, PPh3), 7.50 (s, 1H, C2N3H). 31P NMR (C6D6): d 42.34. Anal. Calc. for C44H39N3P2RuS (%): C, 65.66; H, 4.88; S, 3.98; N, 5.22. Found: C, 65.11; H, 4.63; S, 3.26; N, 5.01%. 2.3. Synthesis of CpRu(dppm)SR (2), CpRu(dppe)SR (3) Heterocyclic thiols (1.0 mmol) was dissolved in THF (50 mL) and cooled to 78 °C. Methyllithium (1.6 in diethylether, 0.70 mL, 1.12 mmol) was added dropwise. The cooling bath was removed after 10 min and the reaction was stirred for a further 15 min at room temperature. CpRu(PPh3)2Cl (0.50 g, 0.68 mmol) and bis(diphenylphosphino)methane or bis(diphenylphosphino)ethane (0.68 mmol) were added and the resulting mixture was refluxed for 4 h. The volatiles were removed under vacuum and the remaining solid was dissolved in toluene (10.0 mL). The resulting solution was filtered over celite to ensure removal of LiCl. The supernatant was taken and concentrated under vacuum to about 4.0 mL then 30.0 mL of cooled hexane was added, a light yellow precipitate was formed which was collected by removing the mother liquor and recrystallized from THF/hexane.
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2.3.1. CpRu(dppm)S(C3N2H3) (2a) Yield = 87% (0.38 g, 0.59 mmol). M.p.: 144–145 °C. EI-MS: m/z (rel. int. %) 651 (93) [M+], 551 (100) [M+C3N2H3S]. 1H NMR (C6D6): d 4.30 (m, 1H, Ph2PCH2), 4.66 (m, 1H, Ph2PCH2), 5.12 (s, 5H, Cp), 5.81 (bs, 1H, NH), 6.99 (m, 12H, PPh2), 7.14 (bs, 1H, C3N2H3), 7.31 (bs, 1H, C3N2H3), 7.51 (m, 8H, PPh3). 31P NMR (C6D6): d 13.00. Anal. Calc. for C33H30N2P2RuSTHF (%): C, 61.48; H, 5.44; S, 4.44; N, 3.88. Found: C, 61.03; H, 4.98; S, 4.02; N, 3.13%. 2.3.2. CpRu(dppm)S(C4N2H5) (2b) Yield 80% (0.36 g, 0.54 mmol). M.p.: 213–215 °C. EI-MS: m/z (rel. int. %) 665 (90) [M+], 551 (93) [M+C4N2H5S]. 1H NMR (C6D6): d 3.02 (s, 3H, CH3), 4.52 (m, 1H, Ph2PCH2), 4.80 (m, 1H, Ph2PCH2), 5.30 (s, 5H, Cp), 6.90 (m, 12H, PPh2), 6.99 (bs, 1H, C3N2H2), 7.01 (bs, 1H, C3N2H2), 7.57 (m, 8H, PPh2). 31P NMR (C6D6): d 15.23. Anal. Calc. for C34H32N2P2RuS (%): C, 61.53; H, 4.86; S, 4.22; N, 4.83. Found: C, 60.52; H, 4.08; S, 3.90; N, 4.15%. 2.3.3. CpRu(dppm)S(C3N2SH3) (2c) Yield = 60% (0.28 g, 0.41 mmol). M.p.: 173–175 °C. EI-MS: m/z (rel. int. %) 682 (98) [M+], 550 (100) [M+C3N2H3S2]. 1H NMR (C6D6): d 2.06 (s, 3H, CH3), 4.38 (m, 1H, Ph2PCH2), 4.54 (m, 1H, Ph2PCH2), 5.05 (s, 5H, Cp), 6.82 (m, 12H, PPh2), 7.53 (m, 8H, PPh2). 31P NMR (C6D6): d 15.01. Anal. Calc. for C33H30N2P2RuS2 (%): C, 58.14; H, 4.44; S, 9.41; N, 4.11%. Found: C, 57.15; H, 3.92; S, 8.62; N, 3.78%. 2.3.4. CpRu(dppm)S(C3N3H4) (2d) Yield = 65% (0.29 g, 0.44 mmol). M.p.: 163–165 °C. EI-MS: m/z (rel. int. %) 666 (88) [M+], 551 (95) [M+C3N3H4S]. 1H NMR (C6D6): d 3.05 (s, 1H, CH3), 4.44 (m, 1H, Ph2PCH2), 4.69 (m, 1H, Ph2PCH2), 5.23 (s, 5H, Cp), 6.89 (m, 12H, PPh2), 7.37 (s, 1H, C2N3H), 7.55 (m, 8H, PPh3). 31P NMR (C6D6): d 15.84. Anal. Calc. for C33H31N3P2RuS (%): C, 59.63; H, 4.70; S, 4.82; N, 6.32. Found: C, 58.70; H, 4.23; S, 4.23; N, 6.01%. 2.3.5. CpRu(dppe)S(C3N2H3) (3a) Yield = 90% (0.41 g, 0.61 mmol). M.p.: 133–135 °C. EI-MS: m/z (rel. int. %) 665 (95) [M+], 565 (100) [M+C3N2H3S]. 1H NMR (C6D6): d 1.95 (m, 2H, PPh2CH2), 2.49 (m, 2H, PPh2CH2), 4.96 (s, 5H, Cp), 5.36 (bs, 1H, NH), 6.95 (m, 12H, PPh2), 7.06 (bs, 1H, C3N2H3), 7.08 (bs, 1H, C3N2H3), 7.77 (m, 8H, PPh2). 31P NMR (C6D6): d 81.51. Anal. Calc. for C34H32N2P2RuS: C, 61.53; H, 4.86; S, 4.83; N, 4.22. Found: C, 60.91; H, 4.18; S, 4.22; N, 3.91%. 2.3.6. CpRu(dppe)S(C4N2H5) (3b) Yield = 80% (0.37 g, 0.54 mmol). M.p.: 128–130 °C. EI-MS: m/z (rel. int. %) 679 (99) [M+], 565 (100) [M+C4N2H5S]. 1H NMR (C6D6): d 2.02 (m, 2H, PPh2CH2), 2.36 (m, 2H, PPh2CH2), 2.93 (s, 3H, CH3), 5.20 (s, 5H, Cp), 5.48 (bs, 1H, C3N2H2), 5.80 (bs, 1H, C3N2H2), 7.01 (m, 12H, PPh2), 7.67 (m, 8H, PPh2). 31P NMR (C6D6): d 80.80. Anal. Calc. for C35H34N2P2RuS (%): C, 62.03; H, 5.06; S, 4.73; N, 4.13. Found: C, 61.69; H, 5.60; S, 4.36; N, 3.90%. 2.3.7. CpRu(dppe)S(C3N2SH3) (3c) Yield = 85% (0.40 g, 0.58 mmol). M.p.: 124–125 °C. EI-MS: m/z (rel. int. %) 565 (100) [M+C3N2H3S2]. 1H NMR (C6D6): d 1.98 (m, 2H, PPh2CH2), 2.16 (s, 3H, CH3), 2.48 (m, 2H, PPh2CH2), 4.99 (s, 5H, Cp), 6.94 (m, 12H, PPh2), 7.75 (m, 8H, PPh2). 31P NMR (C6D6): d 80.79. Anal. Calc. for C34H32N2P2RuS2THF (%): C, 59.44; H, 5.25; S, 8.35; N, 3.65% Found: C, 58.51; H, 5.05; S, 7.65; N, 3.49%. 2.3.8. CpRu(dppe)S(C3N3H4) (3d) Yield = 85% (0.39 g, 0.58 mmol). M.p.: 158–160 °C. EI-MS: m/z (rel. int. %) 679 (98) [M+], (100) [M+C3N2H4S]. 1H NMR (acetoned6): d 2.54 (m, 2H, PPh2CH2), 2.59 (m, 2H, PPh2CH2), 4.99 (s, 5H, Cp), 7.27 (m, 12H, PPh2), 7.50 (s, 1H, C2N3H), 7.79 (m, 8H, PPh2). 1H
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NMR (C6D6): d 81.37. Anal. Calc. for C34H33N3P2RuS: C, 60.17; H, 4.90; S, 4.72; N, 6.19% Found: C, 59.38; H, 4.81; S, 4.12; N, 5.92%.
2.4. Synthesis of CpRu(PPh3)(CO)S(C4N2H5) (4b) CO gas was bubbled through a THF solution (30 mL) of complex 1b (0.40 g, 0.50 mmol) for 30 min at room temperature. The mixture was stirred under CO-atmosphere for 3 h. The solution was concentrated under vacuum to about 4.0 mL then 30.0 mL of cooled hexane was added, a yellow precipitate was formed which was collected by removing the mother liquor and washed several Table 1 Crystal data and structure refinement for 3a and 3b.
CCDC number Chemical formula Molecular weight Crystal system Space group Unit cell dimension a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Dcalc (g cm3) F(0 0 0) Crystal size (mm) Reflections measured Unique reflections Data/restraints/parameters Goodness-of-fit (GOF) on F2 R1a, wR2a [I P 2r(I)] R1a, wR2a Maximum and minimum peak in final Fourier map (e Å3) a
3a
3b
728102 C34H32N2P2RuS 663.69 orthorhombic Pna2(1)
728101 C36H36Cl2N2P2RuS 762.64 triclinic P1
20.7860(10) 14.5939(7) 9.5541(4) Å 90 90 90 2898.2(2) 4 1.521 1360 0.30 0.18 0.10 12 255 5452 5452/1/361 0.909 0.0628, 0.1391 0.1220, 0.1758 0.858, 1.317
9.2741(3) 10.6145(3) 18.3048(7) 96.983(2) 101.6070(10) 106.760(2) 1658.82(10) 2 1.527 780 0.28 0.18 0.15 33 137 9702 9702/0/393 0.972 0.0585, 0.1247 0.1219, 0.1520 1.138, 1.686
2.5. Instrumentation FT-IR spectra were recorded with a Perkin–Elmer FT-IR 1000 spectrometer (KBr disks or CH2Cl2 solution). NMR spectra were recorded on a Bruker Avance 400 MHz spectrometer, operating in the fourier-transform mode. 1H NMR spectra were recorded at 400 MHz (relative to C6D6, d 7.16, acetone-d6, 2.05). 31P{1H} NMR spectra were recorded at 161.2 MHz in C6D6 with P(OMe)3 as external standard (d 139.0, relative to 85% H3PO4). Mass spectra were performed on a Finnigan MAT 8200 instrument. Melting points were determined using analytically pure samples, sealed off in nitrogen-purged capillaries on a Gallenkamp MFB 595 010 melting point apparatus. Microanalyses were performed by the Institute of Organic and Macromolecular Chemistry, FSU-Jena, Jena, Germany. CpRu(PPh3)2Cl was prepared by published procedures [26]. All other chemicals were purchased from commercial suppliers and were used as received. Cyclic voltammetric studies were performed in dichloromethane using a BAS 100 electrochemical workstation. Three electrodes were utilized in this system, gold working electrode; platinum flag counter electrode, and a silver wire pseudo-reference electrode. For ease of comparison, all potentials are converted to the ferrocene–ferrocenium couple as a reference (E0 = 0.00 V, DE = 125 mV) [27–29]. The cell temperature was maintained at 25.0 ± 0.1 °C. Tetrabutylammonium tetrafluoroborate was used as the supporting electrolyte. 2.6. Crystallography X-ray structural analyses were carried out on an Enraf-Nonius Kappa CCD single-crystal X-ray diffractometer. Table 1 summarizes
x ¼ 1=r2 ðF 2o Þ þ ð0:0598PÞ2 where P ¼ ðF 2o þ 2F 2c Þ=3.
Ru Ph3P
times with cooled n-hexane and dried in vacuum. Yield = 60% (0.17 g, 0.30 mmol). M.p.: 181–183 °C. 1H NMR (C6D6): d 3.02 (s, 3H, CH3), 4.92 (s, 5H, Cp), 6.45 (d, 1H, JH–H = 2 Hz, C4N2H5), 6.90 (m, 9H, PPh3), 7.21 (d, 1H, JH–H = 2 Hz, C4N2H5), 7.57 (m, 6H, PPh3). 31P NMR (C6D6): d 57.36. IR (CH2Cl2): 1950 cm1. Anal. Calc. for C28H25N2OPRuS (%): C, 59.04.53; H, 4.42; S, 5.63; N, 4.92. Found: C, 58.88; H, 4.32; S, 5.23; N, 4.85%.
Cl
+
+
Ru
RSLi Ph3P
SR
PPh3
LiCl
PPh3
(1) CO
P-P
Ru Ph2P
SR
+
PPh3
Ru Ph3P
PPh2
PPh3
4b
N N H
+
CO
P-P = dppm (2), dppe (3)
RS =
SR
NMe S (a)
N
S
(b) Me
N
N S
Scheme 1. Synthesis of complexes.
N S (c)
N N Me
S (d)
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the structural data of 3a and 3b. Data were corrected for Lorentz and polarization effects. The SHELXTL (G.M. Sheldrick, Madison, WI) program package was used to solve (direct methods) and refine the structures. All non-hydrogen atoms, with the exception of disordered carbon centers, were refined with anisotropic thermal parameters. Hydrogen atoms were included as riding on their respective carbon atoms. 3. Results and discussion 3.1. Synthesis The heterocyclic-thiolato complexes, CpRu(PPh3)2SR (1) [R = imidazolyl: C3N2H3 (a), 1-methylimidazolyl: C4N2H5 (b), 5methyl-1,3,5-thiadiazolyl: C3N2SH3 (c) and 5-methyl-4H-1,2,4triazolyl C3N3H4 (d)] are accessible in a two-step synthesis protocol: selective metallation of the heterocyclic thiol by using excess of MeLi, followed by the reaction of the generated heterocyclic anion with Ru-chloride (Scheme 1). The work-up includes removal of LiCl, accomplished by dissolving the complexes in toluene and filtration over celite. Complexes 1a–d can be precipitated from toluene solution by slow addition of n-hexane. In the presence of the bisphospine-ligands (dppm, dppe), the same reaction (CpRu(PPh3)2Cl + LiSR) gives the chelate complexes CpRu(dppm)SR (2) and CpRu(dppe)SR, (3) (Scheme 1). If CO gas is bubbled through a THF solution of 1b, the complex CpRu(PPh3)(CO)S(C4N2H5); 4b is produced in which a CO group replaced one PPh3 ligand (Scheme 1). The thiolato complexes 1–3 and 4b are air-stable solids but airsensitive in solution. They are yellow solids, isolated in 60–87% yield and are soluble in polar organic solvents. These complexes were characterized by elemental analysis and spectroscopy (IR, 1 H, 31P{1H} NMR and MS). The solid-state structures of 3a and 3b by X-ray diffraction are determined. The 1H NMR spectra of the thiolate complexes show a singlet in the ranges of 4.68–4.77, 4.96–5.20, 5.05–5.30 ppm and at 4.92 ppm characteristic for the Cp-ring protons of 1, 2, 3 and 4b, respectively. These ranges are consistent with the ranges observed for the alkyl or aryl thiolate complexes CpRu(L)(L’)SR (L = L0 = PPh3, ½ dppe, ½ dppm, L = PPh3, L0 = CO) [24,25,30–32]. The spectra of these complexes exhibit well-resolved resonance signals with the expected coupling pattern for each of the heterocyclic groups present in these compounds. Their 31P NMR spectra show a singlet in the ranges of 42.09–42.51, 13.00–15.84, 80.79–81.37 and at 57.36 ppm for complexes 1, 2, 3 and 4b, respectively. These ranges of the 31P NMR data are also similar to those found for the corresponding thiolates CpRu(L)(L0 )SR, thiocarboxylates [24,25,30–32] CpRu(L)(L0 )SCOR [33] and thiocarbonates CpRu(L)(L0 )SCO2R [34]. The IR spectrum of 4b displays a strong band at 1946 cm1 for the terminal carbonyl group bonded to ruthenium. This value is comparable to those reported for analogues ruthenium alkyl or aryl-thiolates [24,25,30–32]. The TOF-MS spectra of 1–3 and 4b show the molecular ion peak for most complexes. For compounds 1c, 1d and 2c, TOF-MS spectra show the highest peak as (M+SR). The base peak for complex 1 is found to be [CpRu(PPh3)2]+, for 2 is [CpRu(dppm)]+ and for 3 is [CpRu(dppe)]+. Further ions by loss of the phosphine groups are also observed. 3.2. Crystal structures The X-ray structures of 3a and 3b were determined by singlecrystal X-ray structure analysis. Single-crystals of these complexes could be obtained by slow vapor diffusion of n-pentane into a dichloromethane solution containing 3a and 3b at 25 °C. The structures of 3a and 3b are presented in Figs. 1 and 2, respectively. Se-
lected bond distances and angles of these complexes are summarized in Table 2. The structures of 3a and 3b consist of a simple complex formed by coordination of the 2-mercapto-1-imidazolyl or 2-mercapto-1-methylimidazolyl (3b) ligand to the CpRu(dppe) fragment. These complexes have a three-legged piano stool structure with the thiolate ligand and the two P-atoms of the dppe-ligand are the legs while the Cp ring (bonded to ruthenium in an g5 fashion) as its base. In both structures 3a and 3b, the planar five-membered ring is attached to the Ru-center by the sulfur atom with a Ru–S bond lengths of 2.416(2) and 2.4153(10) Å for 3a and 3b, respectively. These bond distances are similar for those
Fig. 1. X-ray structure of CpRu(dppe)S(C3N2H3) (3a).
Fig. 2. X-ray structure of CpRu(dppe)S(C4N2H5) (3b).
Table 2 Selected bond length (Å) and bond angle (°) for compounds 3a and 3b. 3a Ru(1)–C(33) Ru(1)–C(29) Ru(1)–C(30) Ru(1)–C(32) Ru(1)–C(31) Ru(1)–S(1) Ru(1)–P(1) Ru(1)–P(2) S(1)–C(25) P(1)–Ru(1)–S(1) P(2)–Ru(1)–S(1) P(1)–Ru(1)–P(2) Ru(1)–S(1)–C(25)
3b 2.195(10) 2.224(9) 2.235(10) 2.260(9) 2.276(8) 2.416(2) 2.260(2) 2.274(3) 1.761(9) 87.40(9) 87.82(9) 82.68(9) 109.6(3)
Ru(1)–C(1) Ru(1)–C(2) Ru(1)–C(3) Ru(1)–C(4) Ru(1)–C(5) Ru(1)–S(1) Ru(1)–P(1) Ru(1)–P(2) S(1)–C(32) P(1)–Ru(1)–S(1) P(2)–Ru(1)–S(1) P(2)–Ru(1)–P(1) Ru(1)–S(1)–C(32)
2.237(4) 2.231(4) 2.198(4) 2.209(4) 2.231(4) 2.4153(10) 2.2692(11) 2.2644(11) 1.747(4) 87.32(4) 85.27(4) 83.98(4) 111.64(14)
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Table 3 Cyclic voltammetry data of CpRu(PPh3)2SR complexes.a Compound CpRu(PPh3)2Cl CpRu(dppm)Cl CpRu(dppe)Cl 1c 1d 2c 2d 3c 3d
b Eox p (V)
0.028 0.164 0.161 0.189 0.102 0.221
Ered (V) p
DE (mV)
E1/2 (V)c
0.334 0.06 0.251 0.311 0.312 0.313
360 340 110 362 104 90 122 210 108
0.10 [36] 0.03 [36] 0.05 [36] 0.153 0.112 0.206 0.25 0.207 0.239
a Solvent dichloromethane, supporting electrolyte Bu4NBF4 (0.10 M), scan rate (0.1 V s1), gold disk working electrode, Pt-wire auxiliary electrode, reference electrode Ag at 25 °C. b The cathodic peak maximum. red c E1=2 ðVÞ ¼ ðEox p þ Ep Þ=2.
reported of the known Ru(II) thiolato complexes [23–25,30–32]. The Ru–P bond lengths in 3a (2.260(2), 2.274(3) Å) and in 3b (2.2692(11), 2.2644(11) Å) are close to the corresponding values of CpRu(dppe)SCOCO2Et (2.2772(6), 2.2527(6) Å) [35]. Angles around Ru-center are consistent with the usual distorted octahedral coordination usually found in these complexes. The bite angles [P–Ru–P] of the dppe-ligand are 82.68(9)° for (3a) and 83.98(4)° for (3b). The other two angles of the three-legged structure of 3a are P1–Ru–S = 87.40(9)° and P2–Ru–S = 87.82(9)°, and for compound 3b P1–Ru–S 87.40(9)° and P2–Ru–S = 87.82(9)°. These data are similar to those found in CpRu(dppe)SX (X = R, COR, CO2R) complexes indicating a distorted octahedral geometry around the Rucenter [24,25,30–35]. 3.3. Electrochemistry The electron-transfer behavior of the complexes in dichloromethane solution was examined by cyclic voltammetry and the corresponding results are summarized in Table 3. As a representa-
tive example, the cyclic voltammogram for complex 3c is shown in Fig. 3. Our concern here is the quasi-reversible single oxidation wave lies between 0.112 to 0.25 V. This wave is assigned to Ru(III/II) and was obtained from an average of anodic and cathodic peak potentials. On the CV timescale, complexes 1(c, d), 2(c, d) and 3(c, d) displayed chemically quasi-reversible oxidation processes at rate of 100 mV s1. The one electron nature of this oxidation has been verified by comparing its current height (ip) with that of the standard ferrocen/ferrocenium couple under identical experimental conditions. The redox potentials (E1/2) are independent of the various scan rates, supporting quasi-reversibility. Complexes 1(c, d), 2(c, d) and 3(c, d) also displayed one chemically irreversible oxidation process suggesting instability of the more highly oxidized state. However, the shift for Ru(III/II) couples is affected with the electron-donor capability of the corresponding ligands. For these complexes, the formal potentials decreased in the order dppm < dppe < (PPh3)2, although the total difference in oxidation potential spanning is relatively small (60 mV). These complexes are easily oxidized relative to the parent [CpRuL2Cl] analogue. The small cathodic shift for Ru(III/II) couples in the [CpRuL2SR] complexes can be explained by the difference in the electron density at the metal center influenced by the nature of the heterocyclic group. 4. Supplementary material CCDC 728102 and 728101 contain the supplementary crystallographic data for 3a and 3b. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Acknowledgement The financial support from the Deanship of Scientific Research, JUST (Grant No. 123/2007) is greatly acknowledged. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23]
Fig. 3. Cyclic voltammogram of 3c in a dichloromethane solution in the presence of Bu4NBF4 (0.10 M) as supporting electrolyte at 25 °C under nitrogen at a scan rate of 100 mV s1, positive going potential scan, potentials are referenced to the Cp2Fe/ Cp2Fe+ couple (Cp2Fe = (g5-C5H5)2Fe) as internal standard.
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