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Organometallics 2010, 29, 6488–6492 DOI: 10.1021/om100835r
Organometallic Macrocyclic Chemistry. 8.1 An Unusual Metallacycle Derived from Phosphine-Alkynyl Thioether Coupling Anthony F. Hill,*,† Barbara Niess,‡ Madeleine Schultz,†,§ Andrew J. P. White,‡ and David J. Williams‡ †
Research School of Chemistry, Institute of Advanced Studies, Australian National University, Canberra, Australian Capital Territory, Australia, and ‡Imperial College of Science, Technology and Medicine, South Kensington, London SW7 2AY, United Kingdom. §Present address: Faculty of Science and Technology, Queensland University of Technology, Brisbane, Queensland, Australia. Received August 26, 2010
The R,ω-diyne 4,7,10-trithiatrideca-2,11-diyne reacts with [RuCl2(PPh3)3] and KPF6 to form the phosphonio-substituted metallatricyclic salt [RuCl(PPh3){κ4C,S,S0 ,S00 -S(CtCMe)C2H4SC2H4SC(PPh3)CMe}]PF6 arising from the activation of one alkynyl group toward nucleophilic attack by extraneous phosphine. Polythiamacrocycles are generally prepared via condensation of R,ω-dithiols with organic dihalocarbons.2 This approach is attended by the formation of polymers or limited control over macrocycle size distribution; however, these hurdles may be overcome through the use of high-dilution techniques or, more conveniently, by employing cesium salts as templating agents (Scheme 1).3 We considered whether the multitude of alkyne coupling transformations that may be mediated by various transition metals might offer an alternative template approach to polythiamacrocycles if applied to a polythioether with alkynyl termini. Toward this end we have investigated the reactions of 4,7,10-trithiatrideca-2,11-diyne (1) with various latetransition-metal complexes that have a proven track record in alkyne activation (Scheme 2).4 Wilkinson’s catalyst, [RhCl(PPh3)3], which has been shown to form metallacyclopentadienes via alkyne coupling,5 was found to react with 1 via a complex sequence of C-S bond cleavage/formation steps to provide the alkynyl complex [RhCl(CtCMe)(κ3S,S0 ,S00 SCMedCHSC2H4SCHdCH2)(PPh3)] (2).4a The zerovalent *To whom correspondence should be addressed. E-mail: a.hill@ anu.edu.au. (1) For part 7, see ref 4c. (2) Parker, D. Macrocycle Synthesis. A Practical Approach; Oxford University Press: London, 1996. (3) (a) Butler, J.; Kellogg, R. M. J. Org. Chem. 1981, 46, 4481. (b) Cooper, S. R. Acc. Chem. Res. 1988, 21, 141. (c) Cooper, S. R.; Rawle, S. C. Struct. Bonding (Berlin) 1990, 72, 1. (4) (a) Caldwell, L. M.; Edwards, A. J.; Hill, A. F.; Neumann, H.; Schultz, M. Organometallics 2003, 22, 2531. (b) Hill, A. F.; Rae, A. D.; Schultz, M.; Willis, A. C. Organometallics 2004, 23, 81. (c) Hill, A. F.; Schultz, M.; Willis, A. C. Organometallics 2005, 24, 2027. (5) (a) Scheller, A.; Winter, W.; M€ uller, E. Justus Liebigs Ann. Chem. 1976, 1448. (b) Bianchini, C.; Masi, D.; Meli, A.; Peruzzini, M.; Vacca, A.; Laschi, F.; Zanello, P. Organometallics 1991, 10, 636. (c) M€uller, J.; Akhnoukh, T.; Gaede, P. E.; Guo, A.-L.; Moran, P.; Qiao, K. J. Organomet. Chem. 1997, 541, 207. (d) Rourke, J. P.; Batsanov, A. S.; Howard, J. A. K.; Marder, T. B. Chem. Commun. 2001, 2626. (6) Cavit, B. E.; Grundy, K. R.; Roper, W. R. J. Chem. Soc., Chem. Commun. 1972, 60. (7) (a) Alcock, N. W.; Hill, A. F.; Melling, R. P.; Thompsett, A. R. Organometallics 1993, 12, 641. (b) Hill, A. F.; Rae, A. D.; Schultz, M.; Willis, A. C. Organometallics 2007, 26, 1325. (c) Dewhurst, R. D.; Hill, A. F.; Rae, A. D.; Willis, A. C. Organometallics 2005, 24, 4703. (d) Hill, A. F.; Schultz, M.; Willis, A. C. Organometallics 2004, 23, 5729. pubs.acs.org/Organometallics
Published on Web 11/01/2010
Scheme 1. Polythiamacrocycle Synthesis2,3
group 8 complex [Ru(CO)2(PPh3)3] (3a)6 under comparatively forcing conditions reacts with internal alkynes or diynes to provide alkyne, ruthenacyclopentadiene, indenone, cyclobutadiene, or cyclopentadienone complexes7 but with terminal alkynes affords simple C-H oxidative addition products.8 The chelate-assisted reaction of 3a with 1, however, proceeds under remarkably mild (ambient) conditions to afford the σ(S)η5-cyclopentadienone complex 4a. A similar osmium complex, 4b, may be formed from [Os(CO)2(PPh3)3] (3b), and in the case of [Os(CO)(CS)(PPh3)3] (3c), it is the thiocarbonyl ligand that is selectively incorporated into the resulting cyclopentadienethione ligand of 4c.4c The enhanced proclivity of thiocarbonyl ligands9 toward migratory insertion has been explored computationally,10 and this feature underpins the pioneering discovery of the first metallaarenes which arose via alkynethiocarbonyl coupling.11 Complex 4c has been shown to react with dimethyl acetylenedicarboxylate (DMAD) to afford (in two (8) (a) Ang, W. H.; Cordiner, R. L.; Hill, A. F.; Perry, T. L.; Wagler, J. Organometallics 2009, 28, 5568. (b) Cordiner, R. L.; Hill, A. F.; Wagler, J. Organometallics 2009, 28, 4880. (c) Bartlett, M. J.; Hill, A. F.; Smith, M. K. Organometallics 2005, 24, 5795. (d) Dewhurst, R. D.; Hill, A. F.; Smith, M. K. Angew. Chem., Int. Ed. 2004, 43, 476. (9) For reviews on thiocarbonyl ligands see: (a) Petz, W. Coord. Chem. Rev. 2008, 252, 1689. (b) Broadhurst, P. V. Polyhedron 1985, 4, 1801. (c) Butler, I. S. Pure Appl. Chem. 1988, 60, 1241. (d) Butler, I. S. Acc. Chem. Res. 1977, 10, 359. (10) Green, J. C.; Hector, A. L.; Hill, A. F.; Lin, S.; Wilton-Ely, J. D. E. T. Organometallics 2008, 27, 5548. (11) (a) Elliott, G. P.; Roper, W. R.; Waters, J. M. J. Chem. Soc., Chem. Commun. 1982, 811. (b) Wright, L. J. Dalton Trans. 2006, 182. r 2010 American Chemical Society
Article
Organometallics, Vol. 29, No. 23, 2010 Scheme 2.
a
a
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Scheme 3. Mechanistic Proposal for the Formation of [7]þ from the Reaction of 1 with 6
L = PPh3; DMAD = dimethyl acetylenedicarboxylate.
steps from 1) a polycyclic tetrathiamacrocycle (5) of considerable structural complexity.4c Each of these precursors provided electron-rich (d8) metal centers, and accordingly, we have now turned our attention to less electron rich metal centers (d6) and report herein the unusual reaction of 1 with [RuCl2(PPh3)3] (6), the product (7) of which is consistent with the coordinative activation of 1 toward nucleophilic attack.
Results and Discussion The manifold of possible reactions that may arise from the activation of alkynes by divalent ruthenium is quite overwhelming and not especially predictable, even for the simplest of alkynes.12 Surprisingly, rather limited information is available concerning the reactivity of [RuCl2(PPh3)3] (6)13 toward simple internal alkynes. Studies have primarily focused on catalytic transformations,14 and in many cases it is not clear that 6 is the actual catalyst: e.g., hydrogenation, hydrosilylation, and hydroboration processes almost certainly involve initial formation of [RuHCl(PPh3)3],15 while terminal (12) Recent reviews discussing ruthenium mediated alkyne transformations include: (a) Lozano-Vila, A. M.; Monsaert, S.; Bajek, A.; Verpoort, F. Chem. Rev. 2010, 110, 4865. (b) Denes, F.; Perez-Luna, A.; Chemla, F. Chem. Rev. 2010, 110, 2366. (c) Tam, W.; Goodreid, J.; Cockburn, N. Curr. Org. Synth. 2009, 6, 219. (d) Boeda, F.; Clavier, H.; Nolan, S. P. Chem. Commun. 2008, 2726. (e) Tobita, H.; Yamahira, N.; Ohta, K.; Komuro, T.; Okazaki, M. Pure Appl. Chem. 2008, 80, 1155. (f ) Liu, R.-S. Synlett 2008, 801. (13) Stephenson, T. A.; Wilkinson, G. J. Inorg. Nucl. Chem. 1966, 28, 945. (14) Selected examples of alkyne functionalisation mediated by 6: (a) Paris, S. I. M.; Lemke, F. R. Inorg. Chem. Commun. 2005, 8, 425. (b) Litvin, E. F.; Freidlin, A. Kh.; Karimov, K. K. Izv. Akad. Nauk SSSR, Ser. Khim. 1972, 1853. (c) Inoue, Y.; Imaizumi, S. J. Mol. Catal. 1988, 49, L19. (d) Ma, D.; Lu, X. J. Chem. Soc., Chem. Commun. 1989, 890. (e) Mueller, P.; Godoy, J. Helv. Chim. Acta 1981, 64, 2531. (15) Hallman, P. S.; Evans, D.; Osborn, J. A.; Wilkinson, G. Chem. Commun. 1967, 305.
alkynes are prone to rearrangement to vinylidenes or allenylidenes,16 a common course for alkynes coordinated to octahedral d6 centers. The reactions of 6 with alkynyl chalcoethers are limited to the reaction with PhCtCSeiPr, which also provides the vinylidene complex [RuCl2{dCdC(SeiPr)Ph}(PPh3)2]17 via intraligand chalcogenolate migration in a manner reminiscent of the reaction of [RuCl(PMe3)2(η-C5H5)] with MeSCtCSMe, which affords [Ru{dCdC(SMe)2}(PMe3)2(η-C5H5)]PF6.18 Heating a mixture of 6 and 1 in tetrahydrofuran under reflux followed by anion metathesis with KPF6 at room temperature affords, after workup, the salt [7]PF6, which on the basis of mass spectrometric and elemental analytical data has a cation [7]þ of composition “RuCl(PPh3)2(1)”. However, spectroscopic data indicate that it does not possess the simple “RuCl(PPh3)2” connectivity, on the basis of two vastly different phosphorus environments (CD2Cl2: δP 33.0 d, -18.6 d) and, most notably, a coupling (4.5 Hz) that was too small for 2JPP across a cis or trans PA-Ru-PB junction. Spectroscopic data for the complex [7]þ were found to be consistent with its formulation as the metallabicycle [RuCl(PPh3){κ4C,S,S0 ,S00 -S(CtCMe)C2H4SC2H4SC(PPh3)CMe}]þ (Scheme 3). This was subsequently confirmed by a crystallographic analysis of the chloroform solvate (16) (a) Wakatsuki, Y.; Yamazaki, H.; Kumegawa, N.; Satoh, T.; Satoh, J. Y. J. Am. Chem. Soc. 1991, 113, 9604. (b) Wakatsuki, Y.; Koga, N.; Yamazaki, H.; Morokuma, K. J. Am. Chem. Soc. 1994, 116, 8105. (c) Shaffer, E. A.; Chen, C.-L.; Beatty, A. M.; Valente, E. J.; Schanz, H.-J. J. Organomet. Chem. 2007, 692, 5221. (d) Touchard, D.; Guesmi, S.; Bouchaib, M.; Haquette, P.; Daridor, A.; Dixneuf, P. H. Organometallics 1996, 15, 2579. (e) Schanz, H.-J.; Jafarpour, L.; Stevens, E. D.; Nolan, S. P. Organometallics 1999, 18, 5187. (f ) Harlow, K. J.; Hill, A. F.; Wilton-Ely, J. D. E. T. J. Chem. Soc., Dalton Trans. 1999, 285. (17) Hill, A. F.; Hulkes, A. G.; White, A. J. P.; Williams, D. J. Organometallics 2000, 19, 371. (18) Miller, D. C.; Angelici, R. J. Organometallics 1991, 10, 89.
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Hill et al. Table 1. Selected Bond Lengths (A˚) and Angles (deg) for 7þ Ru-Cl Ru-S(2) Ru-P(1) S(1)-C(3) S(2)-C(5) S(3)-C(7) P(2)-C(3) C(2)-C(3) C(6)-C(7) C(9)-C(10)
Figure 1. Molecular structure of the cation [7]þ in a crystal of [7]PF6 3 CHCl3 (hydrogen atoms omitted, phenyl rings simplified). For an ORTEP representation see Figure S1 in the Supporting Information.
[7]PF 6 3 CHCl 3 , the results of which are summarized in Figure 1 (vide infra). The complexity of the 1H NMR spectrum of [7]PF6 3 CD2Cl2 reflects the chirality of the complex with each proton of the metallacycle, with the exception of the two methyl groups, residing in a unique chemical environment. In the 13C{1H} NMR spectrum, two methyl resonances are observed at δC 4.7 and 21.5 and the four resonances for the S(CH2CH2)2 unit are observed at δC 30.3, 30.4, 33.0, and 33.6, while the two phosphine environments are indicated by a doubling of the characteristic four-signal pattern, further confirmed in the 31 1 P{ H} NMR spectrum (vide supra). This leaves the resonances at δC 66.0, 96.3, 125.5, and 136.4 (d, 1JPC = 40.1 Hz) to be assigned to the two alkynyl carbon nuclei and those for the RuCC(P)S metallacycle, respectively. The molecular geometry of the cation [7]þ (Table 1) is depicted in Figure 1, from which it is apparent that the coordination at ruthenium is approximately octahedral. The four-membered Ru-C(2)-C(3)-S(1) metallacycle naturally requires a smaller angle at ruthenium (69.95(15)°); however, the remaining angles between cis-disposed ligand donor atoms lie within the range 83.79(6)-107.51(5)°, the largest of these being that between the outer thioether donors, S(1) and S(3). The C10S3 chain of the chelate provides a wealth of comparative geometric data for thioethers bearing sp, sp2 and sp3 carbon substituents, and accordingly the C-S bond lengths show a progressive lengthening as the carbon coordination number (i.e., p character) increases, the shortest being S(3)-C(8) (1.693(8) A˚) and the longest being those to alkyl substituents (1.821(6)-1.836(6) A˚). Although it might be attractive to also attribute the variation of the three Ru-S bond lengths (2.3434(14)-2.4500(14) A˚) to the nature of the thioether substituents, this is precluded by the disparity in the nature of the respective trans ligands. Specifically, the longest Ru-S separation is that trans to C(2), which would be expected to display a hybrid of alkylidene and alkenyl character, two ligand types with which a strong trans influence is typically associated. The key structural element of interest is the RuC(2)-C(3)-S(1) metallacycle, for which some degree of electronic delocalization along the P(2)-C(3)-C(2)-Ru linkage might be presumed, on the basis of a superficial consideration
Cl-Ru-S(1) Cl-Ru-S(3) Cl-Ru-C(2) S(1)-Ru-S(3) S(1)-Ru-C(2) S(2)-Ru-P(1) S(3)-Ru-P(1) P(1)-Ru-C(2) C(5)-S(2)-C(6) C(1)-C(2)-C(3) Ru-C(2)-C(1)
2.4363(14) 2.3680(14) 2.3434(14) 1.802(5) 1.821(6) 1.832(7) 1.772(5) 1.365(7) 1.504(10) 1.451(13) 166.01(5) 83.79(6) 97.81(15) 107.51(5) 69.95(15) 177.64(5) 91.98(5) 94.88(15) 100.2(3) 124.2(5) 130.3(4)
Ru-S(1) Ru-S(3) Ru-C(2) S(1)-C(4) S(2)-C(6) S(3)-C(8) C(1)-C(2) C(4)-C(5) C(8)-C(9) Cl-Ru-S(2) Cl-Ru-P(1) S(1)-Ru-S(2) S(1)-Ru-P(1) S(2)-Ru-S(3) S(2)-Ru-C(2) S(3)-Ru-C(2) C(3)-S(1)-C(4) C(7)-S(3)-C(8) Ru-C(2)-C(3)
2.3249(13) 2.4500(14) 2.025(5) 1.836(6) 1.836(6) 1.693(8) 1.502(7) 1.508(9) 1.195(11) 84.31(6) 96.17(5) 88.27(5) 91.73(5) 85.77(5) 87.34(15) 172.74(15) 101.4(3) 99.0(3) 105.0(4)
of the resonance forms indicated in Scheme 3 (7aþT7bþ). Although the β-phosphonio MCC(PR3)S metallacycle connectivity is unprecedented, numerous examples of β-phosphonioalkenyl ligands have been identified19-22 and the vast (19) (a) Ogata, K.; Seta, J.; Yamamoto, Y.; Kuge, K.; Tatsumi, K. Inorg. Chim. Acta 2007, 360, 3296. (b) Kolobova, N. E.; Ivanov, L. L.; Zhvanko, O. S.; Chechulina, I. N.; Batsanov, A. S.; Struchkov, Y. T. J. Organomet. Chem. 1982, 238, 223. (c) Malisch, W.; Blau, H.; Schubert, U. Chem. Ber. 1983, 116, 690. (d) Cadierno, V.; Gamasa, M. P.; Gimeno, J.; Gonzalez-Bernardo, C.; Perez-Carreno, E.; Garcia-Granda, S. Organometallics 2001, 20, 5177. (e) Ogata, K.; Seta, J.; Yamamoto, Y.; Kuge, K.; Tatsumi, K. Inorg. Chim. Acta 2007, 360, 3296. (f ) Yamamoto, Y.; Ogata, K.; Kuge, K.; Tatsumi, K. Inorg. Chem. Commun. 2002, 5, 862. (g) Malisch, W.; Blau, H.; Blank, K.; Kruger, C.; Liu, L. K. J. Organomet. Chem. 1985, 296, C32. (h) Nishimura, Y.; Arikawa, Y.; Inoue, T.; Onishi, M. Dalton Trans. 2005, 930. (i) Hoffman, D. M.; Huffman, J. C.; Lappas, D.; Wierda, D. A. Organometallics 1993, 12, 4312. ( j) Jeffery, J. C.; Jelliss, P. A.; Psillakis, E.; Rudd, G. E. A.; Stone, F. G. A. J. Organomet. Chem. 1998, 562, 17. (k) Arikawa, Y.; Asayama, T.; Tanaka, C.; Tashita, S.; Tsuji, M.; Ikeda, K.; Umakoshi, K.; Onishi, M. Organometallics 2008, 27, 1227. (l) Falvello, L. R.; Llusar, R.; Margalejo, M. E.; Navarro, R.; Urriolabeitia, E. P. Organometallics 2003, 22, 1132. (m) Braun, T.; Blocker, B.; Schorlemer, V.; Neumann, B.; Stammler, A.; Stammler, H.-G. Dalton Trans. 2002, 2213. (n) Cadierno, V.; Gamasa, M. P.; Gimeno, J.; Borge, J.; Garcia-Granda, S. Organometallics 1997, 16, 3178. (o) Jung, J.-H.; Hoffman, D. M.; Lee, T. R. J. Organomet. Chem. 2000, 599, 112. (p) Lappas, D.; Hoffman, D. M.; Folting, K.; Huffman, J. C. Angew. Chem., Int. Ed. 1988, 27, 587. (q) Hoffman, D. M.; Huffman, J. C.; Lappas, D.; Wierda, D. A. Organometallics 1993, 12, 4312. (r) Fairhurst, S. A.; Hughes, D. L.; Marjani, K.; Richards, R. L. J. Chem. Soc., Dalton Trans. 1998, 1899. (s) Rogers, R. D.; Alt, H. G.; Maisel, H. E. J. Organomet. Chem. 1990, 381, 233. (t) Chin, C. S.; Lee, M.; Oh, M.; Won, G.; Kim, K.; Park, Y. J. Organometallics 2000, 19, 1572. (u) Shih, K.-Y.; Tylicki, R. M.; Wu, W.; Fanwick, P. E.; Walton, R. A. Inorg. Chim. Acta 1995, 229, 105. (20) (a) Casey, C. P.; Nash, J. R.; Yi, C. S.; Selmeczy, A. D.; Chung, S.; Powell, D. R.; Hayashi, R. K. J. Am. Chem. Soc. 1998, 120, 722. (b) Cheng, Y.-C.; Chen, Y.-K.; Huang, T. M.; Yu, C.-I.; Lee, G.-H.; Wang, Y.; Chen, J.-T. Organometallics 1998, 17, 2953. (21) (a) Kalb, W. C.; Demidowicz, Z.; Speckman, D. M.; Knobler, C.; Teller, R. G.; Hawthorne, M. F. Inorg. Chem. 1982, 21, 4027. (b) Gong, L.; Lin, Y.; He, G.; Zhang, H.; Wang, H.; Wen, T. B.; Xia, H. Organometallics 2008, 27, 309. (c) Gong, L.; Wu, L.; Lin, Y.; Zang, H.; Yang, F.; Wen, T. B.; Xia, H. Dalton Trans. 2007, 4122. (d) Gong, L.; Lin, Y.; Wen, T. B.; Xia, H. Organometallics 2009, 28, 1101. (e) Lin, Y.; Gong, L.; Xu, H.; He, H.; Wen, T. B.; Xia, H. Organometallics 2009, 28, 1524. (f ) Gong, L.; Chen, Z.; Lin, Y.; He, X.; Wen, T. B.; Xu, X.; Xia, H. Chem. Eur. J. 2009, 15, 6258. (22) (a) Zhang, H.; Feng, L.; Gong, L.; Wu, L.; He, G.; Wen, T. B.; Yang, F.; Xia, H. Organometallics 2007, 26, 2705. (b) Xia, H.; He, G.; Zhang, H.; Wen, T. B.; Sung, H. H. Y.; Williams, I. D.; Jia, G. J. Am. Chem. Soc. 2004, 126, 6862. (c) Zhang, H.; Xia, H.; He, G.; Wen, T. B.; Gong, L.; Jia, G. Angew. Chem., Int. Ed. 2006, 45, 2920. (d) Gong, L.; Lin, Y.; Wen, T. B.; Zhang, H.; Zeng, B.; Xia, H. Organometallics 2008, 27, 2584. (e) Zhang, H.; Wu, L.; Lin, R.; Zhao, Q.; He, G.; Yang, F.; Wen, B. T.; Xia, H. Chem. Eur. J. 2009, 15, 3546.
Article Scheme 4. Synthesis of Four- and Six-Membered Metallacyclic β-Phosphoniovinyl Complexes20,22
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chelate anchoring of an alkynyl group proximal to the metal to facilitate activation toward nucleophilic attack by phosphine is also implicit in the formation of osma- and ruthena-arenes from the reaction of 6 with 1,4-pentadiyn-3-ol (Scheme 4).22 A mechanism for the formation of [7]þ is suggested in Scheme 3. This involves initial loss of a phosphine ligand and coordination of 1 through up to three of the thioether donors. Notably, the reaction of 6 with the tridentate trithiamacrocycle 1,4,7-trithiacyclononane ([9]aneS3) affords the neutral complex [RuCl2(PPh3)([9]aneS3)], while the same complex with 1,4,8, 11-tetrathiacyclotetradecane ([14]aneS4) affords the salt [RuCl(PPh3)([14]aneS4)]Cl,23 suggesting that multiple thioether donors support ruthenium halide ionization. Coordinative activation of one alkynyl group toward nucleophilic attack would most likely be favored by a cationic ruthenium center; however, the denticity of the polythioether chain during this step remains open to conjecture, given that η3-C,C0 ,S coordination of the alkynyl thioether would most likely be attended by considerable strain. However, this in itself could provide an activating influence and herein lies a possible analogy with η3-propargyl coordination discussed above. Concluding Remarks. The reaction of [RuCl2(PPh3)3] with 1 takes a course quite different from those previously observed for the complexes [RhCl(PPh3)3]4a and [M(CO)(CA)(PPh3)3] (M = Ru, Os; A = O,4b S4c). In considering possible transition-metal alkyne coupling reagents, the possibility of other types of alkyne activation need to be considered. Nevertheless, the multiple functionality of 1 (and possible variants) promises an increasing diversity of unusual organosulfur ligands.
Experimental Section
majority arise from nucleophilic attack upon an alkyne that is activated by coordination to a transition metal. Perhaps the most directly comparable benchmark would be the cationic complex [RuCl(PPh3)(η6-cymene)(CHdCPhPPh3)]þ described by Yamamoto et al.19f Within this complex, the Ru-C, C-C and C-P bond lengths of 2.052, 1.344, and 1.800 A˚ correlate well with the corresponding values of 2.025(5), 1.365(7) and 1.772(5) A˚ observed for [7]þ, suggesting that any ring strain that may exist in this metallacycle is not manifest in geometric responses. Most of the known β-phosphoniovinyl complexes are acyclic,19 though four,20 five21 and six22 membered metallacycles have been isolated. Of these, the four- and six-membered metallacycles are most relevant here in terms of both structural features and the mechanism of their formation. Four-membered β-phosphonio metallacyclobutenes have been shown by Casey20a and Chen20b to arise via nucleophilic attack at cationic allenyl (propargyl) complexes of rhenium and iridium (Scheme 4). For the rhenium example η3 coordination of the allenyl ligand in the precursor was established, while for the iridium example, it is implicit by virtue of the precursor [Ir(CHdCdCH2)Cl(OTf )(CO)(PPh3)2] possessing a labile triflato ligand trans to the allenyl. The possibility of
General Considerations. All manipulations were carried out under a dry and oxygen-free nitrogen atmosphere using standard Schlenk, vacuum-line, and inert-atmosphere drybox (argon) techniques, with dried and degassed solvents which were distilled from either calcium hydride (CH2Cl2) or sodiumpotassium alloy and benzophenone (ethers and paraffins). NMR spectra were obtained at 25 °C on a Varian Gemini 300BB spectrometer (1H at 299.95 MHz and 13C at 75.428 MHz, referenced to solvent; 31P at 121.42 MHz, referenced to external H3PO4). Elemental microanalysis was performed by the microanalytical service of the Australian National University. Electrospray (ESI) mass spectrometry was performed by the Research School of Chemistry mass spectrometry service. Typically a sample was dissolved in dichloromethane and then diluted with methanol or acetonitrile. The complex [RuCl2(PPh3)3]13 was prepared according to the indicated published procedure. The thioether 4,7,10-trithiatrideca-2,11-diyne (1) has been discussed previously;4 however, preparative details have not yet appeared. Accordingly, details are provided in Scheme 5. All other reagents were used as received from commercial sources. Synthesis of 4,7,10-Tetrathiatrideca-1,12-diyne. 2-Mercaptoethyl sulfide (7.72 g, 50 mmol) was dissolved in THF (100 mL), and the solution was cooled in an ice bath. To this solution was added DBU (15.2 g, 100 mmol), and the mixture was stirred for 30 min. This solution was transferred to a dropping funnel, through which it was added dropwise to a solution of propargyl bromide (14.9 g, 80 wt % solution in toluene, Aldrich, 100 mmol) in THF (20 mL) at 0 °C. Upon completion of the addition, the reaction mixture was stirred for a further 2 h. The reaction mixture was (23) (a) Alcock, N. W.; Cannadine, J. C.; Clark, G. R.; Hill, A. F. J. Chem. Soc., Dalton Trans. 1993, 1131. (b) Hill, A. F.; Alcock, N. W.; Cannadine, J. C.; Clark, G. R. J. Organomet. Chem. 1992, 426, C40.
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Organometallics, Vol. 29, No. 23, 2010 Scheme 5. Synthesis of 1
then filtered through diatomaceous earth and the residue further extracted with diethyl ether (3 50 mL). The solvent was removed from the combined filtrates to give an orange-brown oil. The crude oil was purified by column chromatography (silica gel, petroleum ether/diethyl ether 20:1) to give a colorless oil that solidified on standing and was then dried under high vacuum. Yield: 9.92 g (86%, 43.1 mmol). NMR (CDCl3, 300 MHz): 1H, δH 2.28 (t, 2 H, CtCH, 4J = 2.6), 2.79-2.96 (m, 8 H, SCH2CH2S), 3.30 (d, 4 H, CH2CtC, 4J = 2.6 Hz); 13C{1H}, δC 19.3 (CH2CtC), 31.5, 31.6 (SCH2CH2S), 71.7, 79.7 (CtC). IR (CHCl3): ν (cm-1) 3313, 2914, 2118 νCtC. EI-MS: m/z (%) 191 (74) [M - C3H3]þ, 131 (76) [M C3H3 - SC2H4]þ, 99 (100) [M - C3H3 - SC2H4 - S]þ. Anal. Calcd for C10H14S3: C, 52.13; H, 6.12. Found: C, 52.25; H, 6.20. Preparation of 4,7,10-Trithiatrideca-2,11-diyne (1). A mixture of 4,7,10-tetrathiatrideca-1,12-diyne (12.50 g, 54.3 mmol), freshly ground potassium hydroxide (12.20 g, 217 mmol), and tetrahydrofuran (50 mL) were placed in a round-bottom flask. The mixture was stirred at room temperature for 3 days. The reaction mixture was diluted with diethyl ether (30 mL) and then poured into water. The aqueous layer was extracted with diethyl ether (2 100 mL). The combined organic extracts were dried over Na2SO4, and the solvent was removed in vacuo to give a brown solid. This residue was extracted with hot hexane. After removal of the hexane from the filtered extracts the remaining solid was recrystallized from hexane twice to provide a white solid. Yield: 9.12 g (73%, 39.7 mmol). NMR (CDCl3, 300 MHz): 1H, δH 1.69 (s, 6 H, CH3), 2.54-2.69 (m, 8 H, SCH2CH2S); 13C{1H}, δC 5.1 (CH3), 31.6, 35.0 (SCH2CH2), 66.2 (SCtC), 91.0 (CtCMe). IR (CHCl3): ν (cm-1) 2917, 2850, 2024 νCtC, 1425. EI-MS: m/z (%) 229 (23)
Hill et al. [M - H]þ, 174 (100) [M - C3H3 - CH3]þ. Anal. Calcd for C10H14S3: C, 52.13; H, 6.12. Found: C, 52.16; H, 6.26. Synthesis of [RuCl(PPh3){K4C,S,S0 ,S00 -S(CtCMe)C2H4SC2H4SC(PPh3)CMe}]PF6 ([7]PF6). A mixture of [RuCl2(PPh3)3] (6; 0.500 g, 0.52 mmol) and 4,7,10-trithiatrideca-2,11-diyne (1; 0.120 g, 0.52 mmol) in tetrahydrofuran (20 mL) was heated with stirring at 50 °C for 6 h. After it was cooled to room temperature, the reaction mixture was then filtered through diatomaceous earth and the solvent removed under reduced pressure to provide a brown oil. The oil was dissolved in dichloromethane and the solution treated with a solution of KPF6 (0.29 g, 1.56 mmol) in a H2O/EtOH mixture (1 mL/20 mL). The solvent was slowly removed under reduced pressure to a total volume of ca. 20 mL, resulting in the formation of a brown precipitate. The precipitate was isolated by filtration, washed with ethanol, and then recrystallized from a mixture of dichloromethane and ethanol to provide orange crystals. Yield: 0.38 g (71%, 0.37 mmol). NMR (CD2Cl2, 25 °C): 1H, δH 2.34, 2.45 (s 2, 3 H 2, CH3), 1.81, 3.18, 3.22, 3.58, 3.63 (m 5, 8 H, SCH2), 7.16-7.40, 7.51, 7.75-7.90 (m 3, 30 H, C6H5); 13C{1H}, δC 4.7 (CtCCH3), 21.5 (PCdCCH3), 30.3, 30.4, 33.03, 33.6 (SCH2), 66.0 (SCtC), 96.3 (SCtC), 120.0 (d, 1 JPC = 87.1, C1(CPC6H5)]), 125.5 (Ru-C), 128.3, 138.5, 134.1, 134.6 (d 4, C2,3,5,6(C6H5)), 130.0, 135.1 (s 2, C4(PC6H5)), 136.4 (d, 1JPC = 40.1 Hz, PCS); 31P{1H}, δP 33.0 d, -18.6 d, (4JPP = 4.5 Hz), -144.4 (h, 1JPF = 712 Hz, PF6). IR (Nujol): ν (cm-1) 1585, 1460, 1377. FAB-MS (nitrobenzyl alcohol): m/z (%) 891(10) [7]þ. ESI-MS (MeCN): m/z (%) 891 (23) [7]þ, 631 (17) [7 - PPh3]þ. Anal. Calcd for C46H44ClF6P3RuS3: C, 53.31; H, 4.28. Found: C, 53.68; H, 3.98. Crystals suitable for diffractometry were obtained by layering ethanol above a saturated solution of [7]PF6 in chloroform. Crystal data for [7]PF6 3 CHCl3: [C46H44ClP2RuS3](PF6) 3 CHCl3, Mw = 1155.79, monoclinic, C2/c (No. 15), a = 49.935(2) A˚, b = 10.8784(6) A˚, c = 19.599(2) A˚, β = 110.932(5)°, V = 9943.9(12) A˚3, Z = 8, Dc = 1.544 Mg m-3, μ(Cu KR)= 7.100 mm-1, T = 293 K, yellow blocks, Siemens P4 rotating anode diffractometer; 7331 independent measured reflections (Rint = 0.0857), F2 refinement, R1(obs) = 0.0554, wR2(all) = 0.1492, 5893 independent observed absorption-corrected reflections (|Fo| > 4σ(|Fo|), 2θmax = 120°), 604 parameters. CCDC 790596. Supporting Information Available: A CIF file giving crystallographic data for [7]PF6 3 CHCl3 (CCDC 790596) and an ORTEP representation of the molecular geometry of [7]þ (Figure S1). This material is available free of charge via the Internet at http://pubs.acs.org.
