3246
Organometallics 2004, 23, 3246-3251
Insertion Reaction of Ketene into the Metal-Sulfur Bond: Synthesis and Characterization of [Cp2Ln(µ-η1:η2-OC(SEt)dCPh2)]2 (Ln ) Yb, Er, Sm, Y) and [Cp2Er(µ-η1:η2-OC(SEt)dCPhEt)]2 Chunmei Zhang,† Ruiting Liu,† Xigeng Zhou,*,†,‡ Zhenxia Chen,† Linhong Weng,† and Yanghui Lin† Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, People’s Republic of China, and State Key Laboratory of Organometallic Chemistry, Shanghai 200032, People’s Republic of China Received February 13, 2004
Treatment of [Cp2Ln(µ-SEt)]2 with PhRCdCdO gives dimeric complexes [Cp2Ln(µ-η1:η2OC(SEt)dCPhR)]2 [R ) Ph, Ln ) Yb (1), Er (2), Sm (3), Y (4); R ) Et, Ln ) Er (5)], which represent the first example of ketene insertion into a metal-sulfur bond and provide an efficient method for the synthesis of organolanthanides with a β-thiolate-substituted enolate ligand. It is found that an excess of ketene does not affect the nature of the final complexes, with only a single insertion being observed. All these complexes are characterized by elemental analysis and spectroscopic properties. The structures of complexes 1‚C6H5CH3, 2‚C6H5CH3, and 5‚THF are determined through single-crystal X-ray diffraction analysis. Introduction Thiolate complexes continue to attract considerable attention due to their relevance to biological systems1 and the fundamental interest in their structures and reactivity;2 in addition, there is a potential of applications in organosulfur chemistry,3 catalysis,4 and materials science.5 All of these features spurred the chemistry of thiolate complexes to be extensively studied. However, the use of thiolate complexes in organic transformations is still relatively unexplored as compared with complexes containing metal-hydrogen, metal-carbon, metal-nitrogen, or metal-oxygen bonds.6 To our knowledge, only a limited number of metal-sulfur bond insertions, which are thought to be a fundamental step † Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials. ‡ State Key Laboratory of Organometallic Chemistry. (1) (a) Beinert, H. Eur. J. Biochem. 2000, 267, 5657. (b) Marr, A. C.; Spencer, D. J. E.; Schro¨der, M. Coord. Chem. Rev. 2001, 219-221, 1055. (2) (a) Stephan, D. W.; Nadasdi, T. T. Coord. Chem. Rev. 1996, 147, 147. (b) Mandal, S.; Das, G.; Singh, R.; Shukla, R.; Bharadwaj, P. K. Coord. Chem. Rev. 1997, 160, 191. (c) Liaw, W. F.; Lee, J. H.; Gau, H. B.; Chen, C. H.; Lee, G. H. Inorg. Chim. Acta 2001, 322, 99. (d) Pin, C. W.; Peng, J. J.; Shiu, C. W.; Chi, Y.; Peng, S. M.; Lee, G. H. Organometallics 1998, 17, 438. (e) Ellison, J. J.; Nienstedt, A.; Shoner, S. C.; Barnhart, D.; Cowen, J. A.; Kovacs, J. A. J. Am. Chem. Soc. 1998, 120, 5691. (f) Fenwick, A. E.; Fanwick, P. E.; Rothwell, I. P. Organometallics 2003, 22, 535. (3) (a) Hossain, M. M.; Lin, H. M.; Shyu, S. G. Organometallics 2003, 22, 3262. (b) Bianchini, C.; Jimenez, M. V.; Meli, A.; Moneti, S.; Vizza, F.; Herrera, V.; Sanchez-Delgado, R. A. Organometallics 1995, 14, 2342. (c) Fandos, R.; Lanfranchi, M.; Otero, A.; Pellinghelli, M. A.; Ruiz, M. J.; Terreros, P. Organometallics 1996, 15, 4725, and references therein. (d) Bianchini, C.; Masi, D.; Meli, A.; Peruzzini, M.; Vizza, F.; Zanobini, F. Organometallics 1998, 17, 2495. (4) (a) Bayo´n, J. C.; Claver, C.; Masdeu-Bulto´, A. M. Coord. Chem. Rev. 1999, 193-195, 73. (b) Sellmann, D.; Geipel, F.; Moll. M. Angew. Chem., Int. Ed. 2000, 39, 561. (5) (a) Brewer, M.; Khasnis, D.; Buretea, M.; Berardini, M.; Emge, T. J.; Brennan, J. C. Inorg. Chem. 1994, 33, 2743, and references therein. (b) Lee, J.; Emge, T. J.; Brennan, J. G. Inorg. Chem. 1997, 36, 5064, and references therein.
for many metal-promoted functionalizations, have been studied in some detail.7 Therefore, investigations of novel metal-sulfur bond insertions are of great interest and should allow a better understanding of the mechanism and the conditions required to develop new metalpromoted organic transformations. Organolanthanide complexes with amino, alkyl (aryl), or hydrogen ligands have proven to have a remarkable reaction chemistry with unsaturated substrates such as CO, alkenes, PhNCO, and unsaturated amides, which provides many efficient methods for C-C and C-N bond formations.8-10 However, examples of lanthanide-thiolate-based transformations of unsaturated substrates are very rare.11 Recently, Shen et al. presented the insertions of phenyl isocyanate and phenyl isothiocyanate into the Ln-S bond of [(CH3C5H4)2Ln(µ-SPh)(6) (a) Consiglio, G. Chimia 2001, 55, 809. (b) Siegbahn, P. E. M. J. Am. Chem. Soc. 1993, 115, 5803. (c) Hevia, E.; Perez, J.; Riera, L.; Riera, V.; del Rio, I.; Garcia, G. S.; Miguel, D. Chem-Eur. J. 2002, 8, 4510. (d) Wycliff, C.; Samuelson, A. G.; Nethaji, M. Inorg. Chem. 1996, 35, 5427. (e) Martins, A. M.; Ascenso, J. R.; de Azevedo, C. G.; Dias, A. R.; Duarte, M. T.; da Silva, J. F.; Veiros, L. F.; Rodrigues, S. S. Organometallics 2003, 22, 4218. (f) Macgregor, S. A.; Wenger, E. Organometallics 2002, 21, 1278. (g) Cabeza, J. A.; del Rio, I.; Moreno, M.; Riera, V. Organometallics 1998, 17, 3027. (7) (a) Kuniyasu, H.; Sugoh, K.; Su, M. S.; Kurosawa, H. J. Am. Chem. Soc. 1997, 119, 4669, and references therein. (b) Jin, X. L.; Tang, K. L.; Liu, W. D.; Zeng, H.; Zhao, H. H.; Ouyang, Y. Y.; Tang, Y. Q. Polyhedron 1996, 15, 1207, and references therein. (c) Canovese, L.; Visentin, F.; Chessa, G.; Uguagliati, P.; Santo, C.; Bandoli, G.; Maini, L. Organometallics 2003, 22, 3230. (d) Tang, K. L.; Jin, X. L.; Tang, Y. Q. Rev. Heterat. Chem. 1996, 15, 83. (8) (a) Hong, S.; Kawaoka, A. M.; Marks, T. J. J. Am. Chem. Soc. 2003, 125, 15878. (b) Ryu, J. S.; Li, G. Y.; Marks, T. J. J. Am. Chem. Soc. 2003, 125, 12584. (c) Douglass, M. R.; Stern, C. L.; Marks, T. J. J. Am. Chem. Soc. 2001, 123, 10221. (d) Arredondo, V. M.; McDonald, F. E.; Marks, T. J. Organometallics 1999, 18, 1949. (e) Li, Y. W.; Marks, T. J. J. Am. Chem. Soc. 1996, 118, 9295. (f) Evans, W. J.; Seibel, C. A.; Ziller, J. W. Inorg. Chem. 1998, 37, 770. (g) Zhou, X. G.; Huang, Z. E.; Cai, R. F.; Zhang, L. B.; Zhang, L. X.; Huang, X. Y. Organometallics 1999, 18, 4128. (h) Gilbert, A. T.; Davis, B. L.; Emge, T. J.; Broene, R. D. Organometallics 1999, 18, 2125. (i) Molander, G. A.; Dowdy, E. D. J. Org. Chem. 1999, 64, 6515.
10.1021/om049882r CCC: $27.50 © 2004 American Chemical Society Publication on Web 05/07/2004
Insertion of Ketene into the Metal-Sulfur Bond Scheme 1
(THF)]2 to generate [(CH3C5H4)2Ln(µ-η2-OC(SPh)NPh)]2 (Ln ) Nd) and (CH3C5H4)2Ln[µ-η2-SC(SPh)NPh](THF) (Ln ) Nd, Sm), respectively.11a,b However, there is essentially nothing known about other unsaturated substrate insertions into Ln-S bonds. On the other hand, although the interaction of ketenes with organometallic compounds has been investigated extensively, no example of ketene insertion into the metal-sulfur bond has been reported so far.12 Recently, we initiated a study of the reactivity of organolanthanide amino complexes with ketenes both to develop a new method for the construction of support ligands in organolanthanide chemistry and to further probe the reactivity of ketenes toward organometallic complexes, where the first ketene insertion into a lanthanide-nitrogen bond and two unusual transformations of the pendent aryl group of organolanthanides are found (Scheme 1).13 To extend the range of these reactions, we turned our attention to the lanthanide-sulfur bond system. Herein we report the first insertion of ketene into the metalsulfur bond, which provides an efficient method for the synthesis of organolanthanides with β-thiolate-substituted enolate ligands. Experimental Section General Procedure. All operations involving air- and moisture-sensitive compounds were carried out under an inert atmosphere of purified argon or nitrogen using standard Schlenk techniques. All solvents were refluxed and distilled over sodium benzophenone ketyl under nitrogen immediately prior to use. Cp3Ln,14 diphenyl ketene,15 and ethylphenyl (9) (a) Evans, W. J.; Forrestal, K. J.; Ziller, J. W. J. Am. Chem. Soc. 1998, 120, 9273. (b) Ihara, E.; Yoshioka, S.; Furo, M.; Katsura, K.; Yasuda, H.; Mohri, S.; Kanehisa, N.; Kai, Y. Organometallics 2001, 20, 1752. (c) Bogaert, S.; Chenal, T.; Mortreux, A.; Nowogrocki, G.; Lehmann, C. W.; Carpentier, J. F. Organometallics 2001, 20, 199. (d) Zhou, X. G.; Zhang, L. B.; Zhu, M.; Cai, R. F.; Weng, L. H. Organometallics 2001, 20, 5700. (10) (a) Hultzsch, K. C.; Spaniol, T. P.; Okuda, J. Angew. Chem., Int. Ed. 1999, 38, 227. (b) Evans, W. J.; Meadows, J. H.; Hunter, W. E.; Atwood, J. L. Organometallics 1983, 2, 1252. (c) Haar, C. M.; Stern, C. L.; Marks, T. J. Organometallics 1996, 15, 1765. (d) Piers, W. E.; Bercaw, J. E. J. Am. Chem. Soc. 1990, 112, 9406. (e) Molander, G. A.; Hoberg, J. O. J. Am. Chem. Soc. 1992, 114, 3123. (11) (a) Shen, Q.; Li, H. R.; Yao, C. S.; Yao, Y. M.; Zhang, L. L.; Yu, K. B. Organometallics 2001, 20, 3070. (b) Li, H. R.; Yao, Y. M.; Shen, Q.; Wang, L.; Yu, K. B. J. Rare Earths 2002, 20, 370. (c) Hou, Z. M.; Zhang, Y. G.; Tezuka, H.; Xie, P.; Tardif, O.; Koizumi, T.; Yamazaki, H.; Wakatsuki, Y. J. Am. Chem. Soc. 2000, 122, 10533. (d) Nakayama, Y.; Shibahara, T.; Fukumoto, H.; Nakamura, A. Macromolecules 1996, 29, 8014. (e) Taniguchi, Y.; Maruo, M.; Takaki, K.; Fujiwara, Y. Tetrahedron Lett. 1994, 35, 7789. (12) Geoffroy, G. L.; Bassner, S. L. Adv. Organomet. Chem. 1988, 28, 1. (13) Zhang, C. M.; Liu, R. T.; Luo, J.; Zhou, X. G.; Weng, L. H.; Cai, R. F. J. Am. Chem. Soc. (revised).
Organometallics, Vol. 23, No. 13, 2004 3247 ketene16 were prepared according to the procedures described in the literature. Ethanethiol was purchased from Aldrich and used without purification. Elemental analyses for C and H were carried out on a Vario El CHN-O analyzer. Infrared spectra were obtained on a Nicolet FT-IR 360 spectrometer with samples prepared as Nujol mulls. Mass spectra were recorded on a Philips Agilent MS5973N instrument operating in EI mode. Crystalline samples of the respective complexes were rapidly introduced by the direct inlet techniques. 1H NMR data were obtained on a Bruker DMX-500 NMR spectrometer and were referenced to residual protons in THF (δ 1.72, 3.58). Synthesis of [Cp2Yb(µ-η1:η2-OC(SEt)dCPh2)]2 (1). To a 40 mL toluene solution of [Cp2Yb(µ-SEt)]2 (0.369 g, 1.01 mmol) was added Ph2CCO (0.196 g, 1.01 mmol) with a syringe at room temperature. The reaction mixture slowly turned clear. Several days later red crystals of 1‚C6H5CH3 were obtained at room temperature. Yield: 0.58 g (94.4%). Anal. Calcd for C59H58O2S2Yb2: C, 58.60; H, 4.83. Found: C, 58.45; H, 4.55. IR (Nujol, cm-1): 1578 s, 1551 s, 1490 s, 1441 s, 1261w, 1200 s, 1088 s, 1069 s, 1015 s, 972 w, 940 s, 826 w, 757 s, 734 s, 696 s, 614 s. EI-MS: m/z [fragment, relative intensity (%)]: 692 (M - CpH - Ph2CCO - Ph2C, 23), 663 (M - CpH - Ph2CCO - Ph2C Et, 8), 494 (1/2M - Cp, 12), 429 (1/2M - 2Cp, 5), 304 (Cp2Yb, 15), 239 (CpYb, 25), 167 (Ph2C + 1, 100), 66 (CpH, 90). Synthesis of [Cp2Er(µ-η1:η2-OC(SEt)dCPh2)]2 (2). Following the above procedure described for 1, reaction of [Cp2Er(µ-SEt)]2 (0.383 g, 1.06 mmol) with Ph2CCO (0.206 g, 1.06 mmol) gave 2‚C6H5CH3 as pink crystals. Yield: 0.61 g (95.5%). Anal. Calcd for C59H58O2S2Er2: C, 59.16; H, 4.88. Found: C, 59.15; H, 4.73. IR (Nujol, cm-1): 1578 s, 1553 s, 1491 s, 1441 s, 1260 w, 1204 s, 1090 s, 1071 s, 1015 s, 972 w, 941 s, 826 m, 757 s, 736 s, 698 s, 615 s. EI-MS: m/z [fragment, relative intensity (%)]: 682 (M - Ph2C - OC(SEt)CPh2 + 1, 1), 641 (M - 2Cp - OC(SEt)CPh2 - Ph + 1, 2), 256 (OC(SEt)CPh2 + 1, 8), 194 (Ph2CCO, 2), 167 (Ph2C + 1, 100), 65 (Cp, 90). Synthesis of [Cp2Sm(µ-η1:η2-OC(SEt)dCPh2)]2 (3). Following the above procedure described for 1, reaction of [Cp2Sm(µ-SEt)]2 (0.258 g, 0.75 mmol) with Ph2CCO (0.291 g, 1.50 mmol) gave 3‚C6H5CH3 as pale yellow crystals. Yield: 0.42 g (96.3%). Anal. Calcd for C59H58O2S2Sm2: C, 60.88; H, 5.02. Found: C, 60.76; H, 4.84. IR (Nujol, cm-1): 1577 s, 1551 s, 1490 s, 1441 s, 1204 s, 1092 s, 1073 s, 1013 s, 971 w, 941s, 823 m, 756 s, 735 s, 696 s, 614 s. 1H NMR (THF-d8): δ 12.49 (s, 10H, C5H5), 9.14 (s, 10H, C5H5), 7.38-7.13 (m, 25H, C6H5), 2.84-2.93 (q, 4H, CH2CH3), 2.30 (s, 3H, C6H5CH3), 1.21-1.18 (t, 6H, CH2CH3). EI-MS: m/z [fragment, relative intensity (%)]: 619 (M - 4Cp - Ph2CCO - 1, 5), 282 (SmCp2, 25), 217 (SmCp, 20), 194 (Ph2CCO, 100), 165 (Ph2C - 1, 100), 66 (CpH, 10). Synthesis of [Cp2Y(µ-η1:η2-OC(SEt)dCPh2)]2 (4). Following the above procedure described for 1, reaction of [Cp2Y(µSEt)]2 (0.280 g, 1.00 mmol) with Ph2CCO (0.194 g, 1.00 mmol) gave 4‚C6H5CH3 as white crystals. Yield: 0.50 g (96.5%). Anal. Calcd for C59H58O2S2Y2: C, 68.07; H, 5.62. Found: C, 68.29; H, 5.51. IR (Nujol, cm-1): 1578 s, 1552 s, 1491 s, 1441 s, 1259 w, 1204 s, 1090 s, 1071 s, 1015 s, 972 w, 941 m, 826 w, 768 s, 736 s, 698 s, 615 s. 1H NMR (THF-d8): δ 7.33-7.18 (m, 25H), 6.51 (s, 10H, C5H5), 6.40 (s, 10H, C5H5), 2.84-2.89 (q, 4H, CH2CH3), 2.30 (s, 3H, C6H5CH3), 1.21-1.18 (t, 6H, CH2CH3). EI-MS: m/z [fragment, relative intensity (%)]: 689 (M - Cp - Ph2CCO, 3), 627 (M - CpH - OC(SEt)CPh2, 2), 560 (M 3Cp - Ph2CCO + 1, 10), 495 (M - 4Cp - Ph2CCO + 1, 95), 433 (M - 4Cp - OC(SEt)CPh2, 8), 307 (1/2M - Ph2C - 1, 17), 219 (YCp2, 100), 194 (Ph2CCO, 35), 65 (Ph2C - 1, 95), 165 (Cp, 10). (14) Birmingham, J. M.; Wilkinson, G. J. Am. Chem. Soc. 1956, 78, 42. (15) Tailor, E. D.; Mckillop, A.; Hawks, G. H. Org. Synth. 1972, 52, 36. (16) Baigrie, L. M.; Seiklay, H. R.; Tidwell, T. T. J. Am. Chem. Soc. 1985, 107, 5391.
3248
Organometallics, Vol. 23, No. 13, 2004
Zhang et al.
Table 1. Crystal and Data Collection Parameters of Complexes 1, 2, and 5 1‚C6H5CH3 formula molecular weight cryst color cryst dimens (mm) cryst syst space group unit cell dimens a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3 ) Z Dc (g‚cm-3) µ (mm-1) F(000) radiation (λ ) 0.710730 Å) temperature (K) scan type θ range (deg) h,k,l range no. of reflns measd no. of unique reflns completeness to θ max. and min. transmn refinement method no. of data/restraints/params goodness-of-fit on F2 final R indices [I>2σ(I)] R indices (all data) largest diff peak and hole (e‚Å-3)
2‚C6H5CH3
5‚THF
C59H58O2 S2Yb2 1209.25 red 0.10 × 0.20 × 0.20 triclinic P1 h
C59H58O2 S2Er2 1197.69 pink 0.10 × 0.05 × 0.05 triclinic P1 h
C48H58O3 S2Er2 1081.58 pink 0.30 × 0.20 × 0.10 monoclinic C2/c
11.957(4) 12.337(4) 19.107(6) 74.965(4) 75.952(4) 67.469(4) 2481.6(13) 2 1.618 3.872 1200 Mo KR 293(2) ω-2θ 1.82 to 26.01 -13 e h e 14 -15 e k e 15 -23 e l e 18 11 346 9503 (Rint ) 0.0175) 97.3% (θ ) 26.01) 0.6981 and 0.5114 full-matrix least-squares on F2 9503/10/597 1.078 R1 ) 0.0300 wR2 ) 0.0667 R1 ) 0.0391 wR2 ) 0.0708 0.932 and -0.743
12.001(4) 12.354(4) 19.149(6) 74.961(4) 76.028(4) 67.442(4) 2499.9(13) 2 1.591 3.460 1192 Mo KR 298(2) ω-2θ 1.12 to 27.13 -15 e h e 15, -15 e k e 15 -24 e l e 23 12 311 10 392 (Rint ) 0.0175) 93.8% (θ ) 27.13) 0.8460 and 0.7236 full-matrix least-squares on F2 10392/10/597 0.896 R1 ) 0.0286 wR2 ) 0.0540 R1 ) 0.0481 wR2 ) 0.0577 0.941 and -0.602
10.696(4) 28.129(9) 15.256(5) 90 90.510(4) 90 4590(3) 4 1.565 3.761 2152 Mo KR 298(2) ω-2θ 1.97 to 25.01 -8 e h e 12 -33 e k e 29 -18 e l e 17 9541 4043 (Rint ) 0.0330) 99.7% (θ ) 25.01) 0.7049 and 0.3983 full-matrix least-squares on F2 4043/3/270 1.041 R1 ) 0.0385 wR2 ) 0.0869 R1 ) 0.0612 wR2 ) 0.0967 1.233 and -0.662
Synthesis of [Cp2Er(µ-η1:η2-OC(SEt)dCPhEt)]2 (5). To a solution of [Cp2Er(µ-SEt)]2 (0.412 g, 1.14 mmol) in 40 mL of a mixed solvent of toluene and THF was added PhEtCCO (0.166 g, 1.14 mmol) with a syringe at room temperature. Then the solution was concentrated and cooled at -18 °C to give 5‚THF as pink crystals. Yield: 0.579 (93.5%). Anal. Calcd for C48H58O3S2Er2: C, 53.30; H, 5.40. Found: C, 53.49; H, 5.46. IR (Nujol, cm-1): 1614 s, 1569 w, 1493 m, 1293 m, 1138 s, 1092 s, 1071 s, 1016 s, 931 s, 852 m, 769 s, 727 m, 700 s. EIMS: m/z [fragment, relative intensity(%)]: 651 (M - OC(SEt)CPhEt - PhEtC - EtH, 3), 296 (ErCp2, 7), 208 (OC(SEt)CPhEt + 1, 15), 146 (PhEtCCO, 65), 117 (PhEtC - 1, 72), 66 (CpH, 10). X-ray Data Collection, Structure Determination, and Refinement for 1‚C6H5CH3, 2‚C6H5CH3, and 5‚THF. Suitable crystals of complexes 1‚C6H5CH3, 2‚C6H5CH3, and 5‚THF were selected and sealed under argon in Lindemann glass capillaries for X-ray structural analysis. Diffraction data were collected on a Bruker SMART CCD diffractometer using graphite-monochromated Mo KR (λ ) 0.71073 Å) radiation. During the collection of the intensity data, no significant decay was observed. For 1‚C6H5CH3, frames were integrated to the maximum 2θ angle of 52.02° with the Siemens SAINT program to yield a total of 11 346 reflections, of which 9503 were independent (Rint ) 0.0175). For 2‚C6H5CH3, frames were integrated to the maximum 2θ angle of 54.26° with the Siemens SAINT program to yield a total of 12 311 reflections, of which 10 392 were independent (Rint ) 0.0175). For 5‚THF, frames were integrated to the maximum 2θ angle of 50.02° with the Siemens SAINT program to yield a total of 9541 reflections, of which 4043 were independent (Rint ) 0.0330). The final unit cell parameters were determined from the fullmatrix least-squares on F2 refinement of three-dimensional centroids of 9503 reflections for 1‚C6H5CH3, 10 392 reflections
for 2‚C6H5CH3, and 4043 reflections for 5‚THF. The intensities were corrected for Lorentz-polarization effects and empirical absorption with the SADABS program.17A summary of the crystallographic data is given in Table 1. The structure was solved by the direct method using the SHELXL-97 program.18 All non-hydrogen atoms were found from the difference Fourier syntheses. The H atoms were included in calculated positions with isotropic thermal parameters related to those of the supporting carbon atoms, but were not included in the refinement. There is one solvent molecule present per formula unit for each of three structures. All calculations were performed using the Bruker Smart program.
Results and Discussion Insertion of Ph2CdCdO into the Ln-S Bond of [Cp2Ln(µ-SEt)]2. Many unsaturated organic molecules insert into Ln-H, Ln-C, and Ln-N bonds. Despite great efforts having been devoted to the study of lanthanide thiolate complexes,19 only a few examples of such reactions with Ln-S bonds are known.11 To determine if ketene insertion would occur with the lanthanide-sulfur bond, [Cp2Ln(µ-SEt)]2 was prepared (17) Sheldrick, G. M. SADABS, A Program for Empirical Absorption Correction; Go¨ttingen: Germany, 1998. (18) Sheldrick, G. M. SHELXL-97, Program for the Refinement of the Crystal Structure; University of Go¨ttingen: Germany, 1997. (19) (a) Zhou, X. G.; Zhang, L. X.; Zhang, C. M.; Zhang, J.; Zhu, M.; Cai, R. F.; Huang, Z. E.; Huang, Z. X.; Wu, Q. J. J. Organomet. Chem. 2002, 655, 120. (b) Wu, Z. Z.; Huang, Z. E.; Cai, R. F.; Zhou, X. G.; Zheng, X.; You, X. Z.; Huang, X. Y. J. Organomet. Chem. 1996, 506, 25. (c) Poremba, P.; Noltemeyer, M.; Schmidt, H. G.; Edelmann, F. T. J. Organomet. Chem. 1995, 501, 315. (d) Zhang, L. X.; Zhou, X. G.; Huang, Z. E.; Cai, R. F.; Huang, X. Y. Polyhedron 1999, 18, 1533.
Insertion of Ketene into the Metal-Sulfur Bond
Organometallics, Vol. 23, No. 13, 2004 3249
Scheme 2
by the direct protolysis of Cp3Ln with 1 equiv of ethanethiol,20 and its reaction with Ph2CCO was examined. As illustrated in Scheme 2, the reaction of [Cp2Ln(µSEt)]2 with Ph2CCO in toluene provided the µ-η1:η2thiolate-substituted enolate-bridged complexes [Cp2Ln(µη1:η2-OC(SEt)dCPh2)]2 [Ln ) Yb (1), Er (2), Sm (3), Y (4)]. The formation of complexes 1-4 may be interpreted as one Ph2CCO molecule inserting into the Ln-S (bridging) bond of [Cp2Ln(µ-SEt)]2 (Scheme 2). In contrast to the reaction of Cp2LnNiPr2 with Ph2CdCdO, where a second Ph2CdCdO molecule can be coupled to the phenyl ring of the first Ph2CdCdO unit inserted into a Ln-N bond via a resonance effect (Scheme 1),13 we have found that the only observable complex was the single-insertion product [Cp2Sm(µ-η1: η2-OC(SEt)dCPh2)]2 in the reaction of [Cp2Sm(µ-SEt)]2 with 2 equiv of Ph2CdCdO. In addition, no insertion of the Cp-Ln bond was observed at ambient temperature in an excess amount of Ph2CCO even with a longer reaction time.9a,21 The coupling insertion of ketene into the Ln-N bond in toluene, while only monoinsertion into the Ln-S bond under similar conditions, demonstrates that the nature of the lanthanide-ligand bond may have a much greater influence on the ketene insertion. To the best of our knowledge, no previous study of thiolate complexes with ketene was reported, but there have been two reports of the reactivity of ketenes with organometallic complexes containing SH-, S2-, or dithiolate ligands such as [(CO)5WSH]-, [(CO)5W]2(µ-S)2-, and (CpMo)2(µ-S)(µ-S2CR2) (R ) H, Me),22,23 in which the more rapid reaction proceeds by the addition of the coordinated S-H bond (or bridging sulfur atoms) across the CdC bond of the ketene with no direct interaction between the ketene and the metal (Scheme 3). These differences in the selective localization might be partly attributed to the difference of the nature of the metalsulfur bond in the two cases. For [Cp2Ln(µ-SEt)]2 the lesser stability of the lanthanide-sulfur bond between “hard” rare-earth elements and the “soft” sulfur atom enhances the migratory aptitude of the thiolate ligand, while in the latter case ketene insertion into the W-S or Mo-S bond is prevented since the sulfophilic dtransition elements typically have a higher binding affinity for the sulfur atom. Therefore, ketene prefers to react with the coordinated sulfur-containing ligands of d-transition elements. Moreover, the presence of a (20) All [Cp2Ln(µ-SEt)]2 (Ln ) Yb, Er, Sm, Y) were characterized by elemental analysis and IR and mass spectroscopies. The structures of [Cp2Yb(µ-SEt)]2 and [Cp2Er(µ-SEt)]2 were also confirmed by singlecrystal X-ray diffraction analysis. (21) (a) Qian, C.; Qiu, A. Tetrahedron Lett. 1988, 29, 6931. (b) Qian, C.; Qiu, A.; Huang, Y.; Chen, W. J. Organomet. Chem. 1991, 412, 53. (22) Angelici, R. J.; Gingerich, R. G. W. Organometallics 1983, 2, 89. (23) McKenna, M.; Wright, L. L.; Miller, D. J.; Tanner, L.; Haltiwanger, R. C.; DuBois, M. R. J. Am. Chem. Soc. 1983, 105, 5329.
Figure 1. ORTEP diagram of [Cp2Yb(µ-η1:η2-OC(SEt)d CPh2)]2 (1) with the probability ellipsoids drawn at the 30% level. The toluene molecule in the crystal cell is omitted for clarity.
vacant coordination site at the bigger lanthanide metal center is also in favor of satisfying the need of precoordination of the ketene molecule preceding its insertion. Complexes 1-4 are moderately air- and moisturesensitive. Their crystalline products are readily dissolved in THF and sparingly soluble in toluene and n-hexane. All the compounds were characterized by elemental analysis and IR, 1H NMR, and mass spectroscopies, which were in good agreement with the proposed structures. Significantly, the MS data of complexes 1-4 show that the resultant OC(SEt)dCPh2 ligand is less stable and breaks readily under electron impact, thereby being more easily lost as a fragment of Ph2C or Ph2CCO first. This conforms to both the previous observations that organometallic compounds can catalyze the decarbonylation of Ph2CdCdO24 and that the ketene insertion is reversible25 and promises that ketene chemistry of lanthanide metals should be a fertile area since these reactions are not only powerful models for the transformations of ketenes but also tools for synthetic applications. The IR spectral data of 1-4 show strong absorptions at ca. 1552 cm-1, which may be assigned to the stretching vibration of the conjugated CdC bond in the newly formed enolate ligand. The 1H NMR data of 3‚C6H5CH3 and 4‚C6H5CH3 are also consistent with the presence of a noncoordinated toluene molecule in their crystal cell. The structures of complexes 1 and 2 were also confirmed by single-crystal X-ray diffraction analysis. Complex 1 is a dimeric structure (Figure 1). The structural data reveal that diphenylketene has inserted into the Yb-S bond to form a thiolate-substituted enolate anion in which the enolate oxygen and the thiolate sulfur coordinate to Yb3+. The enolate unit bridges the two Yb atoms through the oxygen atom, while the sulfur atom in the newly formed ligand chelates to just one metal to give a formal coordination number of 9 to each Yb atom. The eight atoms Yb(1), S(2), C(37), O(2), Yb(2), S(1), C(11), and O(1) form an interlinked tricyclic structure via the two bridging Yb(1)-O(1) and Yb(2)-O(2) bonds. Complex 1 has (24) Hong, P.; Sonogashira, K.; Hagihara, N. Nippon Kagaku Zasshi 1968, 89, 74. (25) (a) Hommeltoft, S. L.; Baird, M. C. J. Am. Chem. Soc. 1985, 107, 2548. (b) Hommeltoft, S. L.; Baird, M. C. Organometallics 1986, 5, 190.
3250 Organometallics, Vol. 23, No. 13, 2004
Zhang et al. Scheme 3
Table 2. Bond Lengths (Å) and Angles (deg) for Complex 1 Yb(1)-O(1) Yb(1)-O(2) Yb(1)-C(27) Yb(1)-C(28) Yb(1)-C(32) Yb(1)-C(36) Yb(1)-C(31) Yb(1)-C(35) Yb(1)-C(29) Yb(1)-C(34) Yb(1)-C(33) Yb(1)-C(30) Yb(1)-S(2) Yb(2)-O(2) Yb(2)-O(1) Yb(2)-C(9) Yb(2)-C(8) O(1)-Yb(1)-O(2) O(2)-Yb(2)-O(1) C(12)-C(11)-O(1) C(12)-C(11)-S(1)
2.293(3) 2.372(3) 2.579(5) 2.590(5) 2.612(5) 2.616(5) 2.634(5) 2.643(5) 2.648(5) 2.659(5) 2.665(5) 2.669(5) 2.890(4) 2.302(3) 2.402(3) 2.599(5) 2.602(5) 67.59(9) 66.94(9) 128.0(4) 125.3(3)
Yb(2)-C(3) Yb(2)-C(4) Yb(2)-C(2) Yb(2)-C(1) Yb(2)-C(10) Yb(2)-C(7) Yb(2)-C(5) Yb(2)-C(6) Yb(2)-S(1) S(1)-C(11) S(1)-C(25) S(2)-C(37) S(2)-C(51) O(1)-C(11) O(2)-C(37) C(11)-C(12) C(37)-C(38) O(1)-C(11)-S(1) C(38)-C(37)-O(2) C(38)-C(37)-S(2) O(2)-C(37)-S(2)
2.608(5) 2.618(6) 2.621(5) 2.625(6) 2.631(5) 2.645(5) 2.650(6) 2.657(5) 2.898(4) 1.793(5) 1.822(5) 1.794(4) 1.815(6) 1.340(5) 1.354(5) 1.340(6) 1.339(6) 106.7(3) 128.7(4) 124.2(3) 107.1(3)
normal metrical parameters in the metallocene part of the molecule (Table 2). Characteristically, complex 1 is an unsymmetrical dimer and has two distinctive metaloxygen distances. The Yb(1)-O(1) and Yb(2)-O(2) distances, 2.293(3) and 2.302(3) Å, are between those expected for a Yb3+-O single bond and a Yb3+r:O donor bond, while the Yb(1)-O(2) and Yb(2)-O(1) distances, 2.372(3) and 2.402(3) Å, respectively, fall in the 2.30(1)2.50(1) range of the Yb3+r:OR2 donating bond lengths for neutral oxygen donor ligands.26 However, there is usually a symmetrical center and the two bridging Ln-O distances are similar in other dimeric oxygenbridging organolanthanide complexes, such as [Cp2Ln(µOR)]227 and [(C5H4Me)Ln(η2-PzMe2)(µ-η1:η2-OSiMe2PzMe2)]2.28 Furthermore, the O-Yb-O angles of 67.59(9)° and 66.94(9)° are smaller than the corresponding values observed in other dinuclear oxygen-bridging complexes, 69.2(6)-78.0(4)°.29 The similar results are also observed in [Cp2Ln(µ-η1:η3-OC(Bu)NPh)]2 (Ln ) Sm, Dy, Er, Ho).9d This may be attributed to the steric effect caused by the side-on chelating coordination of Yb to the thiolate substituent. The metrical parameters of the enolate moiety in 1 are comparable with those of other metal enolates.30 (26) (a) Qian, C. T.; Wang, B.; Deng, D. L.; Hu, J. Q. Inorg. Chem. 1994, 33, 3382. (b) Zhou, X. G.; Wu, Z. Z.; Jin, Z. S. J. Organomet. Chem. 1992, 431, 289. (27) Wu, Z. Z.; Huang, Z. E.; Cai, R. F.; Xu, Z.; You, X. Z.; Huang, X. Y. Polyhedron 1995, 15, 12. (28) Zhou, X. G.; Huang, Z. E.; Cai, R. F.; Zhang, L. B.; Zhang, L. X.; Huang, X. Y. Organometallics 1999, 18, 4128. (29) (a) Ye, Z. W.; Yu, Y. F.; Wang, S. W.; Jin, X. L. J. Organomet. Chem. 1993, 448, 91. (b) Massarweh, G.; Fischer, R. D. J. Organomet. Chem. 1993, 444, 67. (c) Wu, Z. Z.; Xu, Z.; You, X. Z.; Zhou, X. G.; Huang, X. Y. J. Organomet. Chem. 1994, 483, 107. (30) (a) Evans, W. J.; Dominguez, R.; Hanusa, T. P. Organometallics 1986, 5, 1291. (b) Lappert, M. F.; Raston, C. L.; Engelhardt, L. M.; White, A. H. J. Chem. Soc., Chem. Commun. 1985, 521.
Figure 2. ORTEP diagram of [Cp2Er(µ-η1:η2-OC(SEt)d CPh2)]2 (2) with the probability ellipsoids drawn at the 30% level. The toluene molecule in the crystal cell is omitted for clarity.
Both the C-S and C-O bond distances are in the normal single-bond ranges, while the C(11)-C(12) and C(37)-C(38) distances, 1.340(6) and 1.339(6) Å, are in the observed range for the carbon-carbon double-bond distances.31 The average Yb-S distance of 2.894 Å is similar to the corresponding distance in (C5H4CH2CH2SEt)2YCl,32 when the difference in the metal ionic radii is considered.33 As shown in Figure 2, complex 2 is isostructural to complex 1 and is also an unsymmetrical dimeric structure. The thiolate-substituted enolate ligand exhibits an unusual bonding mode, which acts as both a bridging and side-on chelating group. The structural parameters of 2 (Table 3) are very similar to those for complex 1. The Er-C(Cp) distances range from 2.610(4) to 2.678(4) Å, and the average value of 2.646(7) Å is similar to those found in other nine-coordinate Cp2Er-containing lanthanide complexes, such as Cp2Er(µ,η2-HCdNCMe3)34 (2.644(8) Å) and Cp2Er(PzMe2)(THF)28 (2.63(3) Å). The Er-O and Er-S distances are comparable to the corresponding distances in complex 1, respectively, when the difference in the metal ionic radii is considered.33 Insertion of PhEtCdCdO into the Er-S Bond of [Cp2Er(µ-SEt)]2. To understand the factors affecting the insertion of ketene into the lanthanide-sulfur bond, the reactivity of organolanthanide thiolate with PhEtCd CdO was also studied. Consistent with the previous examples, [Cp2Er(µ-SEt)]2 reacted readily with PhEtCCO to form the insertion product [Cp2Er(µ-η1:η2OC(SEt)dCPhEt)]2 (5), indicating that the insertion is less affected by steric factors. In addition, it was found that a large excess of PhEtCdCdO did not affect the (31) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A. G. J. Chem. Soc., Perkin Trans. 1987, S1. (32) Schumann, H.; Herrmann, K.; Demtschuk, J.; Muhle, SH. Z. Anorg. Allg. Chem. 1999, 625, 1107. (33) Shannon, R. D. Acta Crystallogr. 1976, A32, 751. (34) Evans, W. J.; Hanusa, T. P.; Meadows, J. H.; Huner, W. E.; Atwood, J. L. Organometallics 1987, 6, 295.
Insertion of Ketene into the Metal-Sulfur Bond
Organometallics, Vol. 23, No. 13, 2004 3251
Table 3. Bond Lengths (Å) and Angles (deg) for Complex 2
Table 4. Bond Lengths (Å) and Angles (deg) for Complex 5
Er(1)-O(1) Er(1)-O(2) Er(1)-C(28) Er(1)-C(27) Er(1)-C(32) Er(1)-C(36) Er(1)-C(31) Er(1)-C(29) Er(1)-C(34) Er(1)-C(35) Er(1)-C(33) Er(1)-C(30) Er(1)-S(2) Er(2)-O(2) Er(2)-O(1) Er(2)-C(8) Er(2)-C(9)
Er(1)-O(1) Er(1)-C(2) Er(1)-C(8) Er(1)-C(3) Er(1)-C(6) Er(1)-C(9) Er(1)-C(7) Er(1)-C(1)
O(1)-Er(1)-O(2) O(2)-Er(2)-O(1) C(12)-C(11)-O(1) C(12)-C(11)-S(1)
2.304(3) 2.395(3) 2.610(4) 2.618(4) 2.628(5) 2.638(4) 2.653(4) 2.664(4) 2.669(5) 2.670(4) 2.672(5) 2.678(4) 2.898(4) 2.322(2) 2.421(3) 2.620(4) 2.624(4) 67.59(9) 66.87(9) 128.4(4) 124.9(3)
Er(2)-C(3) Er(2)-C(4) Er(2)-C(2) Er(2)-C(1) Er(2)-C(10) Er(2)-C(5) Er(2)-C(7) Er(2)-C(6) Er(2)-S(1) O(1)-C(11) O(2)-C(37) S(1)-C(11) S(1)-C(25) S(2)-C(37) C(2)-C(51) C(11)-C(12) C(37)-C(38) O(1)-C(11)-S(1) C(38)-C(37)-O(2) C(38)-C(37)-S(2) O(2)-C(37)-S(2)
2.628(5) 2.634(5) 2.636(5) 2.643(5) 2.658(4) 2.661(5) 2.662(4) 2.668(4) 2.906(4) 1.343(4) 1.347(4) 1.799(4) 1.818(4) 1.803(4) 1.823(5) 1.342(5) 1.340(5) 106.6(3) 129.2(4) 123.7(3) 107.0(3)
Figure 3. ORTEP diagram of [Cp2Er(µ-η1:η2-OC(SEt)d CPhEt)]2 (5) with the probability ellipsoids drawn at the 30% level. The THF molecule in the crystal cell is omitted for clarity.
nature of the final product, with only a single insertion being observed. Complex 5 is moderately sensitive toward moisture and air. It is soluble in THF and toluene, but less soluble in hexane. In the IR spectra of 5, the characterized absorption at ca. 2097 cm-1 for the stretch of free PhEtCdCdO is absent, but a new strong band at 1610 cm-1 is present, which may be attributable to the CdC stretch.30 Figure 3 shows the molecule structure of 5. Selected bond distances and angles are listed in Table 4. Complex 5 is a centrosymmetric dimmer, in which each erbium atom is coordinated by two η5-cyclopentadienyl groups, one chelating thiolate-substituted enolate ligand, and one bridging O atom of a second enolate ligand. The bridging Er2O2 unit is planar. The coordination number of the erbium atom is 9. The cyclopentadienyl groups on each erbium center are arranged in an eclipsed conformation. The complex has no unusual distances or angles in the Cp2Er unit. The C(13)-O(1)
O(1A)-Er(1)-O(1) C(14)-C(13)-O(1)
2.368(4) 2.631(7) 2.640(9) 2.645(7) 2.650(9) 2.651(8) 2.652(9) 2.658(7) 69.03(17) 129.5(6)
Er(1)-C(10) Er(1)-C(5) Er(1)-C(4) Er(1)-S(1) S(1)-C(13) S(1)-C(11) O(1)-C(13) C(13)-C(14) C(14)-C(13)-S(1) O(1)-C(13)-S(1)
2.658(8) 2.673(7) 2.677(7) 2.899(4) 1.804(6) 1.819(7) 1.347(7) 1.329(9) 119.4(5) 111.0(4)
distance of 1.347(7) Å is in the 1.293-1.407 Å range of C(sp2)-O distances.31 The Er-O distances in 5 are slightly shorter than the corresponding values in 2. This may be attributed to the steric effect of the bulky phenyl ring. Conclusions The present results demonstrate that lanthanocene thiolates exhibit high activity toward ketenes. The reactivity of the thiolate-bridged lanthanide complexes toward ketenes is different from those of the SH-- or S2--bridged transition metal complexes. For the former Ph2CdCdO or PhEtCdCdO inserts preferably into the lanthanide-sulfur bond via the ketene CdO, while in the latter cases only sulfur-based nucleophilic addition products across the ketene CdC bond are isolated. Moreover, in contrast to the trends of organolanthanide amino complexes Cp2LnNiPr2, where a second equivalent of ketene can be incorporated into the first insertion product, in the case of organolanthanide thiolate complexes, only the monoinsertion product was obtained. All these differences indicate that the nature of the metal-ligand bond may have a much greater influence on the ketene insertion. To the best of our knowledge, only a few scattered examples of the insertions of ketene into the metal-ligand bonds have been reported so far. The present results would seem to offer a convenient way to generate new types of enolate anionic ligands incorporating the weak bonding of thiolate in organometallic chemistry. Acknowledgment. We thank the NNSF of China, NSF of Shanghai, the Fund of the New Century Distinguished Scientist of the Education Ministry of China, and the Research Fund for the Doctoral Program of Higher Education of China for financial support. Supporting Information Available: Tables of atomic coordinates and thermal parameters, all bond distances and angles, and experimental data for all structurally characterized complexes. This material is available free of charge via the Internet at http://pubs.acs.org. OM049882R
