Syntheses of Bimetallic Zwitterionic Complexes Containing

Jan 15, 2010 - Ding Luo, Yongxin Li, Sumod A. Pullarkat, Kirsty E. Cockle, and Pak-Hing Leung*. Division of Chemistry and Biological Chemistry, School...
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Organometallics 2010, 29, 893–903 DOI: 10.1021/om900958p

893

Syntheses of Bimetallic Zwitterionic Complexes Containing Stereogenic Bifunctionalized Phosphine through Stepwise Insertion and Hydration Reactions Ding Luo, Yongxin Li, Sumod A. Pullarkat, Kirsty E. Cockle, and Pak-Hing Leung* Division of Chemistry and Biological Chemistry, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore Received November 3, 2009

A class of bifunctionalized phosphine complexes bearing a stereogenic center at phosphorus have been synthesized through stepwise insertion and hydration of the two alkynyl groups of a prochiral dialkynylphosphine complex, [Ru(η6-benzene){PPh(CtCCH3)2}Cl2]. One of the two alkyne moieties of this complex inserted into the Pd-C bond of cyclopalladated benzylamine complexes to yield bimetallic complexes containing two stereogenic centers at ruthenium and phosphorus with high stereoselectivity and yield. Subsequently, the remaining free alkynyl group underwent hydration in a mixed solvent system of DCM/acetone/H2O (2:10:1), which resulted in the formation of bimetallic zwitterions bearing anionic palladium(II) and cationic ruthenium(II) centers. The carbon-carbon triple bond was converted into a ketonyl group during the hydration, and the absolute configuration at phosphorus was observed to remain unchanged in the products. All structures of the insertion and hydration products have been identified by X-ray analyses or 2D ROESY NMR studies.

Introduction Much attention has been devoted to the study of transition metal complexes bearing phosphine ligands. In this field, chiral phosphines are especially important due to their potential of being ligands not only in biologically active complexes1 but also in organic catalysts,2 including those wellknown transition metal catalyzed asymmetric processes such

as hydrogenation,2d-k hydrogen transfer reaction,2l hydrosilylation,2m,n coupling reaction,2o-r allylic alkylation,2s-u and epoxidation.2v One of methods to produce P-chiral phosphines is the use of the classical resolution technique that converts a racemic mixture into a pair of diastereoisomers through a reaction with an optically active reagent. Platinum, iron, and palladium complexes bearing chiral ligands have been applied as resolving agents.3,4 Among them, palladacycles bearing chiral nitrogen donor ligands4 were utilized most frequently since these agents were found to be extremely effective for the resolutions of both monoand bidentate phosphines. Apart from the resolution technique, P-chiral phosphines could also be obtained through asymmetric syntheses. To induce the chirality at the phosphorus atom, one of the two similar functional groups such as dialkenyl or dialkynyl groups is usually functionalized. For example, the palladium or platinum complexes containing 1-(dimethylamino)ethylnaphthalene as auxiliary

*To whom correspondence should be addressed. E-mail: pakhing@ ntu.edu.sg. Fax: þ65 6791 1961. Tel: þ65 6316 8899. (1) (a) Tiekink, E. R. T. Crit. Rev. Oncol./Hematol. 2002, 42, 225. (b) Song, Y. C.; Vittal, J. J.; Srinivasan, N.; Chan, S. H.; Leung, P. H. Tetrahedron: Asymmetry 1999, 10, 1433. (c) Papathanasiou, P.; Salem, G.; Waring, P.; Willis, A. C. J. Chem. Soc., Dalton Trans. 1997, 3435. (2) (a) Crepy, K. V. L.; Imamoto, T. Top. Curr. Chem. 2003, 229, 1. (b) Taira, S.; Crepy, K. V. L.; Imamoto, T. Chirality 2002, 14, 386. (c) Moberg, V.; Mottalib, M. A.; Sauer, D.; Poplavskaya, Y.; Craig, D. C.; Colbran, S. B.; Deeming, A. J.; Nordlander, E. Dalton Trans. 2008, 2442. (d) Kitamura, M.; Ohkuma, T.; Inoue, S.; Sayo, N.; Kumobayashi, H.; Akuragawa, S.; Otha, T.; Takaya, H.; Noyori, R. J. Am. Chem. Soc. 1988, 110, 629. (e) Miyashita, A.; Yasuda, A.; Takaya, H.; Toriumi, K.; Ito, T.; Souchi, T.; Noyori, R. J. Am. Chem. Soc. 1980, 102, 7932. (f) Noyori, R.; Okhuma, T.; Kitamura, M.; Takaya, H.; Sayo, N.; Kumobayashi, H.; Akuragawa, S. J. Am. Chem. Soc. 1987, 109, 5856. (g) Ohta, T.; Takaya, H.; Noyori, R. Inorg. Chem. 1988, 27, 566. (h) Tang, W.; Zhang, X. Chem. Rev. 2003, 103, 3029. (i) Knowles, W. S. Acc. Chem. Res. 1983, 16, 106. (j) Yamanoi, Y.; Imamoto, T. J. Org. Chem. 1999, 64, 2988. (k) Imamoto, T.; Sugita, K.; Yoshida, K. J. Am. Chem. Soc. 2005, 127, 11934. (l) Zassinovich, G.; Mestroni, G.; Gladiali, S. Chem. Rev. 1992, 92, 1051. (m) Sawamura, M.; Kuwano, R.; Ito, Y. Angew. Chem., Int. Ed. Engl. 1994, 33, 111. (n) Kuwano, R.; Uemura, T.; Ito, Y. Tetrahedron Lett. 1999, 40, 1327. (o) Chinchilla, R.; Najera, C. Chem. Rev. 2007, 107, 874. (p) Sonogashira, K.; Tohda, Y.; Nagihara, N. Tetrahedron Lett. 1975, 16, 4467. (q) Barder, T. E.; Walker, S. D.; Martinelli, J. R.; Buchwald, S. L. J. Am. Chem. Soc. 2005, 127, 4685. (r) Mikami, K.; Miyamoto, T.; Hatano, M. Chem. Commun. 2004, 2082. (s) Tsuruta, H.; Imamoto, T. Synlett 2001, 999. (t) Trost, B. M.; van Vranken, D. L. Chem. Rev. 1996, 96, 395. (u) Trost, B. M.; Crawley, M. L. Chem. Rev. 2003, 103, 2921. (v) Jorgensen, K. A. Chem. Rev. 1989, 89, 431.

(3) (a) Bader, A.; Nullmeyers, T.; Pabel, M.; Salem, G.; Willis, A. C.; Wild, S. B. Inorg. Chem. 1995, 34, 384. (b) Crisp, G. T.; Salem, G.; Wild, S. B.; Stephens, F. S. Organometallics 1989, 8, 2360. (4) (a) Wild, S. B. Coord. Chem. Rev. 1997, 166, 291. (b) Dunina, V. V.; Golovan, E. B. Tetrahedron: Asymmetry 1995, 6, 2747. (c) Dunina, V. V.; Kuz'mina, L. G.; Rubina, M. Y.; Grishin, Y. K.; Veits, Y. A.; Kazakova, E. I. Tetrahedron: Asymmetry 1999, 10, 1483. (d) Albert, J.; Cadena, J. M.; Granell, J.; Muller, G.; Panyella, D.; Sanudo, C. Eur. J. Inorg. Chem. 2000, 1283. (e) Salem, G.; Wild, S. B. Inorg. Chem. 1983, 22, 4049. (f) Otsuka, S.; Nakamura, A.; Kano, T.; Tani, K. J. Am. Chem. Soc. 1971, 93, 4301. (g) Barclay, C. E.; Deeble, G.; Doyle, R. J.; Elix, S. A.; Salem, G.; Jones, T. L.; Wild, S. B.; Willis, A. C. J. Chem. Soc., Dalton Trans. 1995, 57. (h) Tani, K.; Tashiro, H.; Yoshida, M.; Yamagata, T. J. Organomet. Chem. 1994, 469, 229. (i) Gladiali, S.; Dore, A.; Fabbri, D.; De Lucchi, O.; Manassero, M. Tetrahedron: Asymmetry 1994, 5, 511. (j) Pabel, M.; Willis, A. C.; Wild, S. B. Angew. Chem., Int. Ed. Engl. 1994, 33, 1835. (k) Pabel, M.; Willis, A. C.; Wild, S. B. Inorg. Chem. 1996, 35, 1244.

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promoted the Diels-Alder reaction between dialkenylphenylphosphine with DMPP (3,4-dimethyl-1-phenylphosphole) to incorporate one of the alkene moieties into the bicyclo[2.2.1] group, thus generating a stereogenic center at phosphorus.5 In our group’s previous works, palladium and platinum complexes promoted [4þ2]5a,5b,6 and [2þ2]7 cycloaddition, hydrophosphination,8 hydroarsination,9 and hydroamination10 have been developed for the asymmetrical synthesis of chiral phosphines. Among these reactions, the above strategy, viz., functionalization of one unsaturated carbon-carbon bond of dialkenylphenylphosphines or dialkynylphenylphosphines, was often utilized in order to generate a stereogenic phosphorus. Recently, insertions of alkynes into the Pd-C bond of palladacycles to yield “singly inserted” or “doubly inserted” products have exhibited high reactivities.11 Many palladacycle complexes with various auxiliaries such as biphenyl-2-ylamine,12 benzylamines,13 N-benzylidenaniline,14 aminotoluene,15 1-(dimethylamino)ethylnaphthalene,16 naphthylamines,17 and 8-methylquinolines18 have been used as the insertion substrates. In the present study, the alkynylphosphine group of a ruthenium complex was observed to insert into the Pd-C bond of cyclopalladated complexes of benzylamines successfully, forming bimetallic complexes with a stereogenic center at phosphorus. Such insertions involving coordinated alkynylphosphines into a (5) (a) Leung, P. H.; Selvaratnam, S.; Cheng, C. R.; Mok, K. F.; Rees, N. H.; McFarlane, W. Chem. Commun. 1997, 751. (b) Selvaratnam, S.; Mok, K. F.; Leung, P. H.; White, A. J. P.; Williams, D. J. Inorg. Chem. 1996, 35, 4798. (c) Leung, P. H. Acc. Chem. Res. 2004, 37, 169. (6) Yeo, W. C.; Chen, S. L.; Tan, G. K.; Leung, P. H. J. Organomet. Chem. 2007, 692, 2539. (7) Yeo, W. C.; Tan, G. K.; Koh, L. L.; Leung, P. H. Eur. J. Inorg. Chem. 2005, 4723. (8) (a) Yeo, W. C.; Tee, S. Y.; Tan, H. B.; Tan, G. K.; Koh, L. L.; Leung, P. H. Inorg. Chem. 2004, 43, 8102. (b) Yeo, W. C.; Tang, L. L.; Yan, B.; Tee, S. Y.; Koh, L. L.; Tan, G. E.; Leung, P. H. Organometallics 2005, 24, 5581. (c) Pullarkat, S. A.; Yi, D.; Li, Y. X.; Tan, G. K.; Leung, P. H. Inorg. Chem. 2006, 45, 7455. (d) Tang, L.; Zhang, Y.; Ding, L.; Li, Y.; Mok, K. F.; Yeo, W. C.; Leung, P. H. Tetrahedron Lett. 2007, 48, 33. (e) Yuan, M.; Pullarkat, S. A.; Ma, M.; Zhang, Y.; Huang, Y.; Li, Y.; Goel, A.; Leung, P. H. Organometallics 2009, 28, 780. (f) Yuan, M.; Pullarkat, S. A.; Yeong, C. H.; Li, Y.; Krishnan, D.; Leung, P. H. Dalton Trans. 2009, 3668. (g) Liu, F.; Pullarkat, S. A.; Li, Y.; Chen, S.; Yuan, M.; Lee, Z. Y.; Leung, P. H. Organometallics, accepted. (h) Zhang, Y.; Pullarkat, S. A.; Li, Y.; Leung, P. H. Inorg. Chem., accepted. (9) (a) Bungabong, M. L.; Tan, K. W.; Li, Y. X.; Selvaratnam, S. V.; Dongol, K. G.; Leung, P. H. Inorg. Chem. 2007, 46, 4733. (b) Liu, F.; Pullarkat, S. A.; Li, Y.; Chen, S.; Leung, P. H. Eur. J. Inorg. Chem., accepted. (10) Liu, X. M.; Mok, K. F.; Leung, P. H. Organometallics 2001, 20, 3918. (11) (a) Ryabov, A. D.; van Eldik, R.; Le Borgne, G.; Pfeffer, M. Organometallics 1993, 12, 1386. (b) Maassarani, F.; Pfeffer, M.; Le Borgne, G.; Grandjean, D. Organometallics 1986, 5, 1511. (c) Kelly, A. E.; Macgregor, S. A.; Willis, A. C.; Nelson, J. H.; Wenger, E. Inorg. Chim. Acta 2003, 352, 79. (d) Spencer, J.; Pfeffer, M.; Kyritsakas, N.; Fischer, J. Organometallics 1995, 14, 2214. (12) Albert, J.; Granell, J.; Luque, A.; Font-Bardia, M.; Solans, X. Polyhedron 2006, 25, 793. (13) (a) Vicente, J.; Saura-Llamas, I.; de Arellano, M. C. R. J. Chem. Soc., Dalton Trans. 1995, 2529. (b) Tao, W.; Silverberg, L. J.; Rheingold, A. L.; Heck, R. F. Organometallics 1989, 8, 2550. (c) Vicente, J.; Saura-Llamas, I.; Turpin, J.; de Arellano, M. C. R.; Jones, P. G. Organometallics 1999, 18, 2683. (14) Albert, J.; Granell, J.; Sales, J. J. Organomet. Chem. 1989, 379, 177. (15) Maassarani, F.; Pfeffer, M.; van Koten, G. Organometallics 1989, 8, 871. (16) G€ ul, N.; Nelson, J. H.; Willis, A. C.; Rae, A. D. Organometallics 2002, 21, 2041. (17) Maassarani, F.; Pfeffer, M.; Le Borgne, G. Organometallics 1987, 6, 2029. (18) Arlen, C.; Pfeffer, M.; Bars, O.; Grandjean, D. J. Chem. Soc., Dalton Trans. 1983, 1535.

Luo et al.

M-C bond, in particular, those reactions leading to the generation of chiral centers, have been rarely reported.19 To functionalize the remaining free phosphinoalkynyl group of the insertion products, a hydration reaction has been carried out. Hydration of alkynes is one of the simplest and most convenient ways to obtain carbonyl compounds.20 This process is normally carried out in aqueous acid but proceeds slowly.21 Many catalysts, including mercuric salt,22 ion-exchange resins containing Hg(II), Cu(I), Zn(II), or Cd(II),23 transition metal phosphomolybdates,24 heteropoly acids (HPAs),25 and zeolite catalysts containing transition metal ions,21,26 thus have been developed. Moreover, a lot of late transition metal complexes, such as Ru(II),27 Ru(III),28 Rh(III),29 Pd(II),30 Pt(II),31 Pt(IV),32 Cu(II),30b and Au(I and III),30a,33 have also been widely applied to improve the reaction rate, yield, and regioselectivity. Apart from catalytic processes on organic compounds, there are a few examples of hydration of an alkyne moiety in organometallic complexes. For example, under acidic conditions, ketonyl and acyl ruthenium complexes have been reported to be prepared through hydration of acetylide ruthenium complexes.34 (19) (a) Berenguer, J. R.; Bernechea, M.; Fornies, J.; Garcı´ a, A.; Lalinde, E.; Moreno, M. T. Inorg. Chem. 2004, 43, 8185. (b) Luo, D.; Li, Y.; Tan, K. W.; Leung, P. H. Organometallics 2009, 28, 6266. (20) (a) Hintermann, L.; Labonne, A. Synthesis 2007, 1121. (b) Alonso, F.; Beletskaya, I. P.; Yus, M. Chem. Rev. 2004, 104, 3079. (21) Izumi, Y. Catal. Today 1997, 33, 371. (22) (a) Budde, W. L.; Dessy, R. E. Tetrahedron Lett. 1963, 4, 651. (b) Budde, W. L.; Dessy, R. E. J. Am. Chem. Soc. 1963, 85, 3964. (c) Stork, G.; Borch, R. J. Am. Chem. Soc. 1964, 86, 935. (23) (a) Billimoria, J. D.; Maclagan, N. F. J. Chem. Soc. 1954, 3257. (b) Moxley, T. T., Jr.; Gates, B. C. J. Mol. Catal. 1981, 12, 389. (c) Newman, M. S. J. Am. Chem. Soc. 1953, 75, 4740. (d) Olah, G. A.; Meidar, D. Synthesis 1978, 671. (24) Moggi, P.; Albanesi, G. React. Kinet. Catal. Lett. 1991, 44, 375. (25) (a) Kozhevnikov, I. V. Chem. Rev. 1998, 98, 171. (b) Matsuo, K.; Urabe, K.; Izumi, Y. Chem. Lett. 1981, 1315. (26) Finiels, A.; Geneste, P.; Marichez, F.; Moreau, P. Catal. Lett. 1989, 2, 181. (27) (a) Alvarez, P.; Gimeno, J.; Lastra, E.; Garcı´ a-Granda, S.; Van der Maelen, J. F.; Bassetti, M. Organometallics 2001, 20, 3762. (b) Suzuki, T.; Tokunaga, M.; Wakatsuki, Y. Org. Lett. 2001, 3. (c) Trost, B. M.; Portnoy, M.; Kurihara, H. J. Am. Chem. Soc. 1997, 119, 836. (28) Halpern, J.; James, B. R.; Kemp, A. L. W. J. Am. Chem. Soc. 1961, 83, 4097. (29) (a) Blum, J.; Huminer, H.; Alper, H. J. Mol. Catal. 1992, 75, 153. (b) James, B. R.; Rempel, G. L. J. Am. Chem. Soc. 1969, 91, 863. (c) SettyFichman, M.; Sasson, Y.; Blum, J. J. Mol. Catal. A: Chem. 1997, 126, 27. (30) (a) Imi, K.; Imai, K.; Utimoto, K. Tetrahedron Lett. 1987, 28, 3127. (b) Meier, I. K.; Marsella, J. A. J. Mol. Catal. 1993, 78, 31. (c) Arcadi, A.; Cacchi, S.; Marinelli, F. Tetrahedron 1993, 49, 4955. (d) Fukuda, Y.; Shiragami, H.; Utimoto, K.; Nozaki, H. J. Org. Chem. 1991, 56, 5816. (31) (a) Hartman, J. W.; Hiscox, W. C.; Jennings, P. W. J. Org. Chem. 1993, 58, 7613. (b) Hiscox, W.; Jennings, P. W. Organometallics 1990, 9, 1997. (c) Jennings, P. W.; Hartman, J. W.; Hiscox, W. C. Inorg. Chim. Acta 1994, 222, 317. (d) Francisco, L. W.; Moreno, D. A.; Atwood, J. D. Organometallics 2001, 20, 4237. (e) Lucey, D. W.; Atwood, J. D. Organometallics 2002, 21, 2481. (32) (a) Badrieh, Y.; Kayyal, A.; Blum, J. J. Mol. Catal. 1992, 75, 161. (b) Baidossi, W.; Lahav, M.; Blum, J. J. Org. Chem. 1997, 62, 669. (c) Israelsohn, O.; Vollhardt, K. P. C.; Blum, J. J. Mol. Catal. A: Chem. 2002, 184, 1. (33) (a) Casado, R.; Contel, M.; Laguna, M.; P., R.; Sanz, S. J. Am. Chem. Soc. 2003, 125, 11925. (b) Fukuda, Y.; Utimoto, K. J. Org. Chem. 1991, 56, 3729. (c) Fukuda, Y.; Utimoto, K. Bull. Chem. Soc. Jpn. 1991, 64, 2013. (d) Jung, H. H.; Floreancig, P. E. J. Org. Chem. 2007, 72, 7359. (e) Mizushima, E.; Sato, K.; Hayashi, T.; Tanaka, M. Angew. Chem., Int. Ed. 2002, 41, 4563. (34) (a) Arikawa, Y.; Nishimura, Y.; Kawano, H.; Onishi, M. Organometallics 2003, 22, 3354. (b) Arikawa, Y.; Asayama, T.; Onishi, M. J. Organomet. Chem. 2007, 692, 194. (c) Arikawa, Y.; Nishimura, Y.; Ikeda, K.; Onishi, M. J. Am. Chem. Soc. 2004, 126, 3706. (d) Ogo, S.; Uehara, K.; Abura, T.; Watanabe, Y.; Fukuzumi, S. J. Am. Chem. Soc. 2004, 126, 16520.

Article

Organometallics, Vol. 29, No. 4, 2010 Scheme 1

However, to the best of our knowledge, there are no reports on the hydration of internal phosphinoalkynes let alone in an asymmetric synthesis scenario. In this study, the alkynyl group in the insertion products was converted into a ketonyl group through hydration in a mixed solvent system of DCM/ acetone/H2O (2:10:1). It is interesting that a stereogenic carbon was formed and the chirality at phosphorus remained unchanged during the hydration reaction.

Results and Discussion Insertion Reaction. [Ru(η6-benzene){PPh(CtCCH3)2}Cl2] (1) was prepared quantitatively through coordination of a free PPh(CtCCH3)2 ligand to ruthenium, following a literature method.19b,35 Complex 1 then underwent the insertion reaction with 0.5 equiv of the organopalladium complex 2 to give the bimetallic complex 3 (Scheme 1). When monitored by 31P{1H} NMR spectroscopy, this reaction was found to be complete in 1 day at room temperature in DCM. Due to the two newly generated stereogenic centers at ruthenium and phosphorus, complex 3 contains two diastereomerically related pairs of enantiomers.The absolute configurations of these diastereoisomers are assigned,36 as shown in Scheme 2 (the circle around the P atom represents the Ru atom). After insertion was completed, the 31P{1H} NMR spectrum of the reaction mixture showed two sharp singlets at δ 11.3 and 22.7 with a ratio of 1:1.7, which indicated the formation of complexes (RRuRP)-3/(SRuSP)-3 and (RRuSP)-3/(SRuRP)-3, respectively. Separation of the crude reaction mixture via silica gel column chromatography (acetone/DCM, 1:4) followed by precipitation using Et2O gave pure (RRuRP)-3/(SRuSP)-3 and (RRuSP)-3/(SRuRP)-3 as orange solids in yields of 23% and 54%, respectively. Recrystallization of (RRuSP)-3/(SRuRP)-3 from DCM/Et2O yielded red prisms. It is interesting that recrystallization of (RRuRP)-3/(SRuSP)-3 or the mixture of these four diastereoisomers also gave (RRuSP)-3/(SRuRP)-3 in the crystals, (35) Berenguer, J. R.; Bernechea, M.; Fornies, J.; Garcı´ a, A.; Lalinde, E. Organometallics 2004, 23, 4288. (36) (a) Stanley, K.; Baird, M. C. J. Am. Chem. Soc. 1975, 97, 6598. (b) Fernandez, S.; Pfeffer, M.; Ritleng, V.; Sirlin, C. Organometallics 1999, 18, 2390.

895

Scheme 2

attributable to the equilibrium existing between these two pairs of isomers in solution. (RRuRP)-3/(SRuSP)-3 and (RRuSP)-3/(SRuRP)-3 are stable in the solid state. However, in DCM or CHCl3 solution, these two pairs of isomers are able to interconvert at room temperature (Scheme 2). It is proposed that this conversion includes the cleavage of the chloride bridge, the reversion of the seven-membered ring (Pd-olefin-phenyl group-CN), and the formation of a new chloride bridge. When monitored by 31P{1H} NMR spectroscopy, the chemical equilibrium was attained within 10 h at room temperature, with the ratio of (RRuRP)-3/(SRuSP)-3 and (RRuSP)-3/(SRuRP)-3 being about 1:1.7 in the final equilibrium state. The insertion of complex 1 into the Pd-C bond of chiral organopalladium complex 4 was also carried out and found to be complete in 1 day at room temperature in DCM (Scheme 1). After the insertion was completed, the 31P{1H} NMR spectrum of the reaction mixture showed only two sharp singlets at δ 11.5 and 22.8 with a ratio of 1:1.1, which indicated the formation of two diastereoisomers, 5 and 6, respectively. After 5 and 6 had been isolated as orange solids in yields of 41% and 46%, respectively, the resulting pure solids of these two complexes were then recrystallized from DCM/Et2O to give the corresponding red prisms. The absolute configurations of complexes 5 and 6 have been assigned as (RRuRPSC) and (RRuSPSC) on the basis of their X-ray data [see section X-ray Structures of Complexes (RRuSP)-3/(SRuRP)-3, 5, and 6]. Furthermore, the solutions of these two complexes in CHCl3 are also optically pure {for 5, [R]D þ492.9 (c 1.0, CHCl3); for 6, [R]D þ447.5 (c 0.6, CHCl3)}, which are supported by the fact that only one set of peaks has been found in each 1H NMR spectrum in CDCl3. Unlike the interconversion between complexes (RRuRP)3/(SRuSP)-3 and (RRuSP)-3/(SRuRP)-3, no similar equilibrium could be observed in the DCM and CHCl3 solutions of complex 5 or 6, also indicating their stable configurations in solutions. The chiral carbon neighboring the NMe groups in complexes 5 and 6 is proposed to lead to this stable configuration. The methyl group on this chiral carbon is observed to occupy the equatorial position in both X-ray structures of

896

Organometallics, Vol. 29, No. 4, 2010 Scheme 3

Luo et al. Table 1. Selected Bond Lengths (A˚) and Angles (deg) of (RRuSP)-3/(SRuRP)-3 Ru(1)-P(1) Ru(1)-Cl(2) Pd(1)-Cl(3) Pd(1)-C(16) P(1)-C(10) C(7)-C(8)

5 and 6, as shown in Scheme 3a (the circle around the P atom represents the Ru atom), while Dreiding model studies suggested that the axially disposed methyl group could result in an unfavored repulsion with the methyl group on the opposite olefin moiety (Scheme 3b). Therefore, the chiral carbon in complexes 5 and 6 limits the free reversion of the seven-membered ring that leads to the formation of the axially disposed methyl group, which is responsible for the stable configurations of these two insertion products. On the other hand, it is interesting that the stereogenic center at ruthenium adopts the same R absolute configuration in complexes 5 and 6. The formation of this chirality on ruthenium is believed to be also controlled by the chiral carbon in these two complexes, which is the only asymmetric induction factor in this insertion reaction. Through Dreiding model studies, it is proposed that upon fixation of the orientation of the seven-membered ring by this chiral carbon (i.e., the structure of Scheme 3b cannot be formed), the generation of the S absolute configuration at ruthenium through a 90° rotation of the P-Ru bond is sterically unfavored due to the resulting repulsion between the R1 group and the involved Cl atom (Scheme 3c). The fact that only the products bearing the R chiral center at ruthenium, 5 and 6, were observed in the insertion reaction involving complex 4 indicated the good stereocontrol at ruthenium. However, the stereoselectivity at the stereogenic phosphorus in this process is not satisfactory, which is attributed to the similar steric effects of the active palladium species11a,d on the two equivalent alkynyl groups of complex 1 in the insertion step. X-ray Structures of Complexes (RRuSP)-3/(SRuRP)-3, 5, and 6. The X-ray crystallographic analyses confirmed the structures of complexes (RRuSP)-3/(SRuRP)-3 (Table 1 and Figure 1), 5 (Table 2 and Figure 2), and 6 (Table 3 and Figure 3). For each complex, the geometry at ruthenium exhibited the “threelegged piano-stool” disposition; the η6-benzene occupies the “stool” position, while the “legs” comprised P and Cl atoms. The angles at the ruthenium center are in the range 81.4(1)87.9(1)° for complexes (RRuSP)-3/(SRuRP)-3, 81.9(1)-87.1(1)° for complex 5, and 82.4(1)-87.5(1)° for complex 6 and are within the expected range.35,37 One of the two alkynyl groups in complex 1 has inserted into the Pd-C bond of the cyclometalated complex, forming a carbon-carbon double bond [C(16)C(17), 1.346(2) A˚ in (RRuSP)-3/(SRuRP)-3, 1.346(3) A˚ in 5, and 1.344(7) A˚ in 6], which connects to palladium and benzylamine through Pd(1)-C(16) and C(17)-C(19), respectively. The insertion process also generated a chloride bridge with a Ru(1)-Cl(2)-Pd(1) bond angle of 115.8(1)° in complexes (37) Pinto, P.; Marconi, G.; Heinemann, F. W.; Zenneck, U. Organometallics 2004, 23, 374.

P(1)-Ru(1)-Cl(1) Cl(1)-Ru(1)-Cl(2) Cl(2)-Pd(1)-N(1) Cl(3)-Pd(1)-N(1) N(1)-Pd(1)-C(16) Ru(1)-P(1)-C(10) C(7)-P(1)-C(10) C(10)-P(1)-C(16)

2.335(1) 2.404(1) 2.408(1) 2.015(2) 1.827(2) 1.187(3) 87.7(1) 87.9(1) 177.8(1) 92.3(1) 94.0(1) 113.6(1) 100.7(1) 116.2(1)

Ru(1)-Cl(1) Pd(1)-Cl(2) Pd(1)-N(1) P(1)-C(7) P(1)-C(16) C(16)-C(17) P(1)-Ru(1)-Cl(2) Cl(2)-Pd(1)-Cl(3) Cl(2)-Pd(1)-C(16) Cl(3)-Pd(1)-C(16) Ru(1)-P(1)-C(7) Ru(1)-P(1)-C(16) C(7)-P(1)-C(16) Ru(1)-Cl(2)-Pd(1)

2.408(1) 2.340(1) 2.107(2) 1.772(2) 1.816(2) 1.346(2) 81.4(1) 85.6(1) 88.2(1) 173.4(1) 109.0(1) 113.0(1) 102.8(1) 115.8(1)

Figure 1. Molecular structure of complex (SRuRP)-3. (RRuSP)-3 and (SRuRP)-3 coexist in each crystal cell with a ratio of 1:1. Table 2. Selected Bond Lengths (A˚) and Angles (deg) of 5 Ru(1)-P(1) Ru(1)-Cl(2) Pd(1)-Cl(3) Pd(1)-C(16) P(1)-C(10) C(7)-C(8) P(1)-Ru(1)-Cl(1) Cl(1)-Ru(1)-Cl(2) Cl(2)-Pd(1)-N(1) Cl(3)-Pd(1)-N(1) N(1)-Pd(1)-C(16) Ru(1)-P(1)-C(10) C(7)-P(1)-C(10) C(10)-P(1)-C(16)

2.335(1) 2.396(1) 2.433(1) 2.019(2) 1.828(2) 1.194(3) 85.0 (1) 87.1(1) 175.0(1) 91.6(1) 94.9(1) 117.1(1) 101.8(1) 102.9(1)

Ru(1)-Cl(1) Pd(1)-Cl(2) Pd(1)-N(1) P(1)-C(7) P(1)-C(16) C(16)-C(17) P(1)-Ru(1)-Cl(2) Cl(2)-Pd(1)-Cl(3) Cl(2)-Pd(1)-C(16) Cl(3)-Pd(1)-C(16) Ru(1)-P(1)-C(7) Ru(1)-P(1)-C(16) C(7)-P(1)-C(16) Ru(1)-Cl(2)-Pd(1)

2.394(1) 2.341(1) 2.118(2) 1.769(2) 1.818(2) 1.346(3) 81.9(1) 83.7(1) 89.7(1) 172.8(1) 108.9(1) 112.3(1) 113.4(1) 115.3(1)

(RRuSP)-3/(SRuRP)-3, 115.3(1)° in complex 5, and 114.8(1)° in complex 6. Moreover, the stereogenic center at ruthenium adopts the same R absolute configuration in complexes 5 and 6, while the stereogenic center at phosphorus is R in complex 5 but S in complex 6. Selected bond distances and angles for complexes (RRuSP)-3/(SRuRP)-3, 5, and 6 are given in Tables 1, 2, and 3, respectively. Hydration Reaction. The remaining free alkyne moiety in the insertion products was converted into a ketonyl group through an asymmetric hydration reaction (Scheme 4). When monitored by 31P{1H} NMR spectroscopy, the addition of water was found to be complete in 5 to 10 days in DCM/acetone/ H2O (2:10:1) at room temperature. Bimetallic zwitterionic

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Scheme 4

Figure 2. Molecular structure of complex 5. Table 3. Selected Bond Lengths (A˚) and Angles (deg) of 6 Ru(1)-P(1) Ru(1)-Cl(2) Pd(1)-Cl(3) Pd(1)-C(16) P(1)-C(10) C(7)-C(8) P(1)-Ru(1)-Cl(1) Cl(1)-Ru(1)-Cl(2) Cl(2)-Pd(1)-N(1) Cl(3)-Pd(1)-N(1) N(1)-Pd(1)-C(16) Ru(1)-P(1)-C(10) C(7)-P(1)-C(10) C(10)-P(1)-C(16)

2.322(2) 2.408(2) 2.405(2) 2.001(5) 1.817(6) 1.192(12) 86.5(1) 87.5(1) 175.1(2) 93.6(2) 93.7(2) 117.7(3) 101.4(4) 110.8(3)

Ru(1)-Cl(1) Pd(1)-Cl(2) Pd(1)-N(1) P(1)-C(7) P(1)-C(16) C(16)-C(17)

2.402(3) 2.344(2) 2.133(5) 1.758(8) 1.800(5) 1.344(7)

P(1)-Ru(1)-Cl(2) Cl(2)-Pd(1)-Cl(3) Cl(2)-Pd(1)-C(16) Cl(3)-Pd(1)-C(16) Ru(1)-P(1)-C(7) Ru(1)-P(1)-C(16) C(7)-P(1)-C(16) Ru(1)-Cl(2)-Pd(1)

82.4(1) 85.4(1) 87.4(2) 172.6(2) 108.8(3) 113.5(2) 102.8(3) 114.8(1)

Figure 3. Molecular structure of complex 6.

complexes 7 to 9 were isolated as yellow solids in yields of 34%, 30%, and 13%, respectively. The 31P{1H} NMR spectra of the hydration products in CDCl3 showed a singlet at ca. δ 50 (δ 49.8 for complex 7, δ 50.0 for complex 8, and δ 49.7 for complex 9). This hydration process was also attempted in other solvent systems such as DCM/methanol/water, DCM/MeCN/ water, or the heterogeneous solvent DCM/water. However,

these conditions resulted in a large decrease in either yield or reaction rate, or both. Furthermore, in an acidic solvent system of DCM/acetone/water (2:10:1) containing dilute HCl, complex 7 decomposed rapidly. More than 1 equiv of HCl (0.0045 M) in the reaction solution would result in the decomposition of all products. The basic solvent system, such as the mixture of DCM, acetone, and the diluted NaOH solution or the mixture of DCM/acetone/water with 1-2 equiv of Et3N, was observed to accelerate the reaction but led to the formation of some unknown compounds and resulted in lower yields. For those reactions performed in basic solvent systems, the best yield has been obtained in DCM/ acetone/water containing 2 equiv of NaOH (0.01 M), in which the hydration reaction of complex 3 was completed in 2 days and gave complex 7 in a yield of 30%. The hydration products 7 to 9 are bimetallic zwitterionic complexes, which contain a positive charge at ruthenium and a negative charge at palladium. The alkynylphosphine has been converted into a ketonylphosphine chelating to ruthenium through P and O. The absolute configurations of the optically pure complexes 8 and 9 are assigned as (RRuRPSCSC) and (SRuSPRCSC), respectively. It is noteworthy that the configuration at phosphorus remained unchanged in complexes 8 and 9 after hydration. Moreover, this process generated a stereogenic carbon at the R-position from phosphorus due to the formation of a Pd-C bond. This regioselectivity has also been observed in other reactions of alkynylphosphine and organometallic complexes such as magnesium dialkylcuprate.38 On the basis of X-ray and the 2D ROESY studies, the H atom on the stereogenic carbon is found to occupy the syn position to the phenyl group on phosphorus in all hydration products, thus leading to the S and R absolute configurations of this chiral carbon in complexes 8 and 9, respectively. To the best our knowledge, no hydrations yielding a C-chiral center at the carbon of the original triple bond have been reported. (38) (a) Kanemura, S.; Kondoh, A.; Yorimitsu, H.; Oshima, K. Org. Lett. 2007, 9, 2031. (b) Kondoh, A.; Yorimitsu, H.; Oshima, K. Org. Lett. 2007, 9, 1383. (c) Xi, Z.; Zhang, W.; Takahashi, T. Tetrahedron Lett. 2004, 45, 2427.

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Table 4. Selected Bond Lengths (A˚) and Angles (deg) of 7 Pd(1)-C(9) Pd(1)-N(1) Ru(1)-O(1) Ru(1)-Cl(2) P(1)-C(10) O(1)-C(8) C(16)-C(17) C(9)-Pd(1)-C(16) C(9)-Pd(1)-N(1) C(16)-Pd(1)-N(1) O(1)-Ru(1)-P(1) P(1)-Ru(1)-Cl(2) C(9)-P(1)-C(16) C(10)-P(1)-C(16) C(16)-P(1)-Ru(1) O(1)-C(8)-C(7) C(7)-C(8)-C(9) C(8)-C(9)-Pd(1) C(17)-C(16)-P(1) P(1)-C(16)-Pd(1) C(16)-C(17)-C(19)

. 2.145(3) 2.109(2) 2.397(1) 1.824(3) 1.260(4) 1.330(4) 76.7(1) 171.6(1) 97.3(1) 81.2(1) 88.8(1) 91.8(1) 110.1(2) 119.4(1) 117.6(3) 119.7(3) 107.2(2) 128.4(2) 94.2(1) 122.4(3)

Pd(1)-C(16) Pd(1)-Cl(1) Ru(1)-P(1) P(1)-C(9) P(1)-C(16) C(8)-C(9)

C(9)-Pd(1)-Cl(1) C(16)-Pd(1)-Cl(1) Cl(1)-Pd(1)-N(1) O(1)-Ru(1)-Cl(2) C(9)-P(1)-C(10) C(9)-P(1)-Ru(1) C(10)-P(1)-Ru(1) C(8)-O(1)-Ru(1) O(1)-C(8)-C(9) C(8)-C(9)-P(1) P(1)-C(9)-Pd(1) C(17)-C(16)-Pd(1) C(16)-C(17)-C(18) C(18)-C(17)-C(19)

Table 5. Selected Bond Lengths (A˚) and Angles (deg) of 8

2.010(3) 2.426(1) 2.306(1) 1.805(3) 1.790(3) 1.435(5)

Pd(1)-C(9) Pd(1)-N(1) Ru(1)-O(1) Ru(1)-Cl(2) P(1)-C(10) O(1)-C(8) C(16)-C(17)

95.4(1) 171.3(1) 90.9(1) 80.7(1) 111.2(2) 101.5(1) 118.6 (1) 121.1(2) 122.6(3) 111.9(2) 89.2(1) 135.6(2) 123.1(3) 114.5(3)

C(9)-Pd(1)-C(16) C(9)-Pd(1)-N(1) C(16)-Pd(1)-N(1) O(1)-Ru(1)-P(1) P(1)-Ru(1)-Cl(2) C(9)-P(1)-C(16) C(10)-P(1)-C(16) C(16)-P(1)-Ru(1) O(1)-C(8)-C(7) C(7)-C(8)-C(9) C(8)-C(9)-Pd(1) C(17)-C(16)-P(1) P(1)-C(16)-Pd(1) C(16)-C(17)-C(19)

Figure 4. Molecular structure of complex 7.

X-ray Structures of Complexes 7 and 8. Complexes 7 and 8 were recrystallized from DCM/Et2O as orange prisms, and their structures were determined by X-ray crystallography (Table 4 and Figure 4 for complex 7; Table 5 and Figure 5 for complex 8). The geometry at ruthenium exhibits the “threelegged piano-stool” disposition with the η6-benzene occupying the “stool” position. The angles at ruthenium are in the range 80.7(1)-88.8(1)° for complex 7 and 81.4(1)-86.1(1)° for complex 8. A ketonyl group has been formed during the course of the reaction and coordinated to ruthenium via O, generating the connections of O(1)-C(8) and Ru(1)-O(1) with the bond lengths of 1.260(4) and 2.109(2) A˚, respectively, in complex 7 and 1.259(2) and 2.096(1) A˚, respectively, in complex 8. The structures of the two complexes also contain a Pd(1)-C(9)-P(1)-C(16) four-membered ring bearing vertexes with relatively small angles (ca. 76° for the C-Pd-C angle and ca. 90° for C-P-C and Pd-C-P angles), thus adopting a slightly distorted planar geometry. Furthermore, the X-ray structure of the optically pure complex 8 confirms the (RRuRPSC) absolute configuration at Ru(1), P(1), and the stereogenic C(9). Selected bond distances and angles for complexes 7 and 8 are given in Tables 4 and 5, respectively.

2.141(2) 2.182(2) 2.096(1) 2.378(1) 1.825(2) 1.259(2) 1.340(2) 76.3(1) 169.9(1) 97.4(1) 81.7(1) 86.1(1) 91.1(1) 111.2(1) 119.6(1) 117.0(2) 120.8(2) 105.5(1) 130.3(1) 94.9(1) 121.2(1)

Pd(1)-C(16) Pd(1)-Cl(1) Ru(1)-P(1) P(1)-C(9) P(1)-C(16) C(8)-C(9)

C(9)-Pd(1)-Cl(1) C(16)-Pd(1)-Cl(1) Cl(1)-Pd(1)-N(1) O(1)-Ru(1)-Cl(2) C(9)-P(1)-C(10) C(9)-P(1)-Ru(1) C(10)-P(1)-Ru(1) C(8)-O(1)-Ru(1) O(1)-C(8)-C(9) C(8)-C(9)-P(1) P(1)-C(9)-Pd(1) C(17)-C(16)-Pd(1) C(16)-C(17)-C(18) C(18)-C(17)-C(19)

1.993(1) 2.425(1) 2.300(1) 1.802(2) 1.778(2) 1.434(2)

95.8 (1) 171.9(1) 90.7(1) 81.4(1) 112.4(1) 101.0(1) 117.5(1) 120.9(1) 122.2(1) 112.4(1) 89.3(1) 133.2(1) 123.4(1) 115.2(1)

Figure 5. Molecular structure of complex 8. Scheme 5

2D ROESY Studies of Complexes 8 and 9. Unfortunately, the crystal of 9 was not obtained, although various crystallization methods were attempted. However, the structure of 9 has been studied through several experiments including the 2D rotating frame nuclear Overhauser enhancement (ROESY) 1H NMR technique. Scheme 5 shows the numbering scheme of complexes 8 and 9 used in 2D ROESY NMR analysis. Selected 31P and 1H NMR data of 8 and 9 are given in Table 6. These NMR assignments are based on a series of 1 H, 31P, 1H{31P}, and 2D ROESY NMR studies of these two

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complexes. Figures 6 and 7 show the 2D 1H-1H ROESY NMR spectra of 8 and 9, respectively. On the basis of the X-ray structure of 8 and a Dreiding model study, the structure of 9 was suggested as shown in Scheme 5. These two structures are almost mirror symmetric except the disposition of substituents on C19. Me19 is in the equatorial position in complex 8, while it is in the axial Table 6. Selected 31P and 1H NMR Spectra Chemical Shift Values of 8 and 9 in CDCl3 (coupling constants in Hz are given in parentheses) 8 31

P NCHMe

50.0 s 1.45 d, (3JHH = 7.0)

CdC-Me

1.71 d (4JPH = 1.8 Hz)

OdC-Me NMe(ax) NMe(eq) PdCH NCHMe C6H6

2.35 d (4JPH = 1.6 Hz) 2.50 s 3.10 s 2.98 s 4.30 q (3JHH = 7.0) 5.97 d (3JPH = 0.9 Hz)

9 49.7 s 1.82 overlapped with peak of CdC-Me 1.82 overlapped with peak of NCHMe 2.37 d (4JPH = 1.7 Hz) 2.68 s 2.94 s 3.14 s 3.22 q (3JHH = 6.7) 6.02 d (3JPH = 0.6 Hz)

899

position in complex 9. Moreover, the absolute configurations at phosphorus in 8 and 9 are different, but due to symmetry, for both complexes, the η6-benzene moiety, rather than the PPh moiety, is closer to the NMe groups and C19. These interactions have been reflected in their 2D ROESY spectra. The 2D ROESY NMR spectrum of 8 shows obvious interactions involving NMe groups, H19 and Me19. As seen in Figure 6, Me19 interacts with both NMe groups [A, Me19-Me20(ax); B, Me19-Me20(eq)]. However, the axial H19 interacts only with the equatorial Me20(eq) [G, Me20(eq)-H19], while the interaction of H19-Me20(ax) has not been observed. These NOE interactions suggest that Me19 is in the equatorial position in complex 8. Furthermore, a NOE signal indicative of the interaction between Me19 and the neighboring phenyl proton H17 [M, Me19-H17] has also been recorded, which is consistent with the fact that Me19 is equatorially disposed. In contrast, for complex 9, similar studies confirm that the corresponding Me19 is in the axial position. Unlike the case of complex 8, the spectrum of complex 9 shows the interactions of H19-Me20(eq) (E), H19-Me20(ax)(F), and Me19-Me20(eq)(A), while there is

Figure 6. Two-dimensional 1H ROESY NMR spectrum of 8 in CDCl3. All off-diagonal peaks are of negative intensity. Selected NOE contracts: A, Me19-Me20(ax); B, Me19-Me20(eq); C, Me2-H3; D, Me20(ax)-Me20(eq); E, Me19-H19; F, Me12-H19; G, Me20(eq)-H19; H, H19-C6H6; I, Me20(eq)-C6H6; J, Me12-C6H6; K, Me12-H14; L, Me12-H6,10; M, Me19-H17; N, Me20(ax)-H17; O, H3-H6,10; P, C6H6-H6,10.

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Figure 7. Two-dimensional 1H ROESY NMR spectrum of 9 in CDCl3. All off-diagonal peaks are of negative intensity except signal O. Selected NOE contracts: A, Me19-Me20(eq); B, Me19-H19; C, Me2-H3; D, Me20(ax)-Me20(eq); E, H19-Me20(eq); F, H19-Me20(ax); G, Me20(eq)-C6H6; H, Me12-C6H6; I, H19-H17; J, Me20(ax)-H17; K, Me12-H14; L, C6H6-H6,10; M, H3-H6,10; N, Me12-H6,10.

no interaction of Me19-Me20(ax). On the other hand, H19, rather than Me19, is also observed to interact with H17, producing signal I (H19-H17). These signals clearly indicate that Me19 is axially disposed in complex 9. The 2D ROESY NMR studies also indicate that the interactions involving η6-benzene, the PPh, NMe groups, and the axial group on C19 are similar in the two complexes. The 2D ROESY NMR spectrum of complex 8 shows signals of C6H6-H19 (H) and C6H6-Me20(eq) (I), while no interactions of H6,10-H19 and H6,10-Me20(eq) have been found. This information indicates that η6-benzene, rather than PPh, is close to the NMe groups and C19 and, thus, allows the assignment of the R absolute configuration at phosphorus in complex 8. As regards complex 9, it is not clear whether signal H and N include the NOE interactions of C6H6-Me19 and H6,10-Me19, respectively, due to the overlap of Me12 and Me19 in the 1H NMR spectrum. However, signal G [C6H6-Me20(eq)] and the absence of the interaction of H6,10-Me20(eq) also suggests the relatively short distance between η6-benzene and NMe groups, which indicates the S absolute configuration at phosphorus in complex 9. Additionally, other signals in these two 2D

ROESY NMR spectra are also obvious and are summarized in the captions of Figures 6 and 7. The signals in the 2D ROESY NMR spectra of two complexes are in accordance with the interactions expected from structures in Scheme 5. Meanwhile, for complex 8, the ROESY data are also consistent with its X-ray structure. Proposed Mechanism of Hydration. With the hydration reaction of complex 3 taken as an example, the ketonyl product 7 is suggested to form through an enol intermediate, as shown in Scheme 6 (the square indicates the vacant coordination site). Addition of water across the alkynyl group generated complex 11, which is then converted into the enol intermediate 12 after the loss of one proton. The intermediate 12 subsequently underwent tautomerization to give the ketonyl complex 13, yielding a stereogenic carbon at the R-position from phosphorus. Coordination of oxygen to the ruthenium atom and the subsequent loss of one chloride anion gave complex 7. During this process, one molecule of HCl was formed, which led to the decomposition of some hydration products and thus was responsible for the moderate yield. Compared with complex 8, complex 9 is relatively unstable due to the repulsion between Me19 and Me12

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Scheme 6

(Scheme 5) resulting from the fact that Me19 is axially disposed in complex 9; thus more decomposition of complex 9 than 8 was observed under similar acidic conditions, which led to the low yield of complex 9.

Conclusions In conclusion, this study presents stepwise functionalization of the two alkyne moieties of the dialkynylphosphine complex 1 through insertion and hydration reactions. The insertion of one carbon-carbon triple bond into the Pd-C bond of cyclopalladated complexes of benzylamines generated a stereogenic center at phosphorus. The optically pure bimetallic products were isolated, and it was found that the chiral carbon in the products resulted in the exclusive formation of the R absolute configuration at ruthenium. However, the stereocontrol at phosphorus is not satisfactory. The subsequent addition of water across the remaining free alkynyl group yielded a ketonylphosphine chelating to ruthenium through phosphorus and oxygen. This ketonylphosphine also binds to palladium via the stereogenic carbon at the R-position from phosphorus, thus forming a PdC-P-C four-membered ring. Many solvent systems of this process have been scanned, and for the consideration of the reaction rate and yield, the mixed solvent system of DCM/ acetone/water (2:10:1) was utilized. Furthermore, the absolute configuration at phosphorus remained unchanged after the formation of the bifunctionalized phosphine complex through hydration. We are currently exploring enhancement of selectivity as well as other heterofunctionalization reactions in such complexes. Catalytic applications of these complexes are also being investigated.

Experimental Section Reactions involving air-sensitive compounds were performed under an inert atmosphere of argon using standard Schlenk techniques. NMR spectra were recorded at 25 °C on Bruker Avance 300, 400, and 500 spectrometers. Optical rotations were measured on the specified solution in a 0.1 dm cell at 25 °C with a Perkin-Elmer 341 polarimeter. Melting points were determined on a SRS Optimelt automated melting point system, SRS MPA 100. Elemental analysis was performed by the Elemental

Analysis Laboratory of the Division of Chemistry and Biological Chemistry at Nanyang Technological University. Complex 119b,35 and the dimeric benzylamine palladium(II) complex 539 were prepared according to literature methods. Synthesis of Complex 3. Complex 1 (0.20 g, 0.45 mmol) was stirred with cyclopalladated complex 2 (0.13 g, 0.23 mmol) in DCM (40 mL) for 1 day at room temperature. Removal of solvent gave the crude insertion products as dark red residues. Subsequent purification of the crude pruducts by silica gel column chromatography (acetone/DCM, 1:4) followed by precipitation in Et2O generated (RRuRP)-3/(SRuSP)-3 and (RRuSP)-3/(SRuRP)-3 as orange solids. Yield: (RRuRP)-3/(SRuSP)-3, 0.081 g (23%); (RRuSP)3/(SRuRP)-3, 0.175 g (54%). Recrystallization of (RRuRP)3/(SRuSP)-3 or (RRuSP)-3/(SRuRP)-3 or the mixture of the two from DCM/Et2O all gave pure (RRuSP)-3/(SRuRP)-3 as red prisms. For (RRuRP)-3/(SRuSP)-3: Mp: 215-216 °C dec. 31P{1H} NMR (CDCl3, δ): 11.3 (s). 1H NMR (CDCl3, δ): 1.59 (s, 3H, NMe); 2.21 (d, 4JPH = 3.5 Hz, 3H, PCC-Me); 2.43 (s, 3H, NMe); 2.59-2.61 (m, 4H, NCHH and CdC-Me); 3.52 (d, 2JHH = 10.8 Hz, 1H, NCHH); 5.58 (s, 6H, C6H6); 6.99-7.01 (1H), 7.12-7.17 (1H), 7.32-7.37 (1H), 7.44-7.56 (2H), 7.63-7.68 (2H), 8.81-8.88 (2H) (m, aromatics). Anal. Calcd for C27H29Cl3NPPdRu 3 0.5CH2Cl2: C, 43.8; H, 4.0; N, 1.9. Found: C, 43.9; H, 4.3; N, 1.9. For (RRuSP)3/(SRuRP)-3: Mp: 220-221 °C dec. 31P{1H} NMR (CDCl3, δ): 22.7 (s). 1H NMR (CDCl3, δ): 1.45 (d, 4JPH = 2.6 Hz, 3H, CdCMe); 2.25 (d, 4JPH = 3.4 Hz, 3H, PCC-Me); 2.69 (s, 3H, NMe); 3.01 (d, 2JHH = 10.8 Hz, 1H, NCHH); 3.11 (s, 3H, NMe); 3.94 (d, 2 JHH = 10.8 Hz, 1H, NCHH); 5.71 (s, 6H, C6H6); 7.09-7.18 (2H), 7.26-7.28 (2H), 7.43-7.52 (3H), 8.14-8.21 (2H) (m, aromatics). Anal. Calcd for C27H29Cl3NPPdRu: C, 45.5; H, 4.1; N, 2.0. Found: C, 45.1; H, 4.5; N, 1.9. Syntheses of Complexes 5 and 6. Complexes 5 and 6 were prepared following the same procedure as that reported for 3. Complex 1 (0.100 g, 0.23 mmol) was stirred with cyclopalladated complex 4 (0.067 g, 0.12 mmol) in DCM (20 mL) for 1 day at room temperature. Removal of solvent gave the crude insertion products as dark red residues. Subsequent purification of the crude pruducts by silica gel column chromatography (acetone/DCM, 1:3) followed by precipitation in Et2O generated 5 and 6 as orange solids. Yield: 5, 0.068 g (41%); 6, 0.077 g (46%). Complexes 5 and 6 were recrystallized from DCM/Et2O as red prisms, respectively. For 5: Mp: 225-226 °C dec. [R]D þ492.9 (c 1.0, CHCl3). 31P{1H} NMR (CDCl3, δ): 11.5 (s). 1H NMR (CDCl3, δ): 1,10 (d, 3JHH = 7.0 Hz, 3H, NCHMe); 1.64 (s, 3H NMe); 2.20 (d, 4JPH = 3.5 Hz, 3H, (39) Roberts, N. K.; Wild, S. B. J. Chem. Soc., Dalton Trans. 1979, 2015.

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Table 7. Crystallographic Data for Complexes (RRuSP)-3/(SRuRP)-3, 5, 6, 7, and 8 (RRuSP)-3/(SRuRP)-3

5

6

7

C28H32Cl2NOPPdRu 707.89 P2(1) monoclinic 10.2816(2) 13.3428(3) 10.4877(2) 90 108.8250(10) 90 1361.80(5) 2 273(2) 1.726 0.71073 1.492 708 -0.007(12) 0.0230 0.0489

)

)

formula C28H31Cl5NPPdRu C29H32Cl6NPPdRu C28.50H32Cl4NPPdRu C27H30Cl2NOPPdRu fw 797.23 845.70 768.79 693.86 space group P2(1)/n P2(1) P2(1)2(1)2(1) P2(1)/c cryst syst monoclinic monoclinic orthorhombic monoclinic a/A˚ 15.5945(6) 10.0546(4) 8.7910(2) 13.8455(6) b/A˚ 12.6641(5) 13.1269(5) 13.6179(4) 9.4914(4) c/A˚ 15.7896(6) 13.0716(5) 26.1332(7) 21.3557(8) R/deg 90 90 90 90 β/deg 102.418(2) 110.007(2) 90 105.924(2) γ/deg 90 90 90 90 3045.3(2) 1621.15(11) 3128.54(14) 2698.73(19) V/A˚3 Z 4 2 4 4 T/K 173(2) 173(2) 296(2) 173(2) 1.739 1.732 1.632 1.708 Dcalcd/g cm-3 λ/A˚ 0.71073 0.71073 0.71073 0.71073 1.597 1.585 1.469 1.504 μ/mm-1 F(000) 1584 840 1532 1384 Flack param -0.025(13) 0.00(5) a 0.0256 0.0200 0.0492 0.0278 R1 (obsd data) 0.0614 0.0464 0.1158 0.0695 wR2 (obsd data)b P P P P a R1 = Fo| - |Fc / |Fo|. b wR2 = { [w(Fo2 - Fc2)2]/ [w(Fo2)2]}1/2, w-1 = σ2(Fo)2 þ (aP)2 þ bP.

8

PCC-Me); 2.34 (s, 3H NMe); 2.58 (d, 4JPH = 2.8 Hz, 3H, CdCMe); 3.89 (q, 3JHH = 7.0 Hz, 1H, NCHMe); 5.55 (s, 6H, C6H6); 7.13-7.15 (2H), 7.25-7.30 (1H), 7.38-7.40 (1H), 7.49-7.54 (1H), 7.61-7.66 (2H), 8.79-8.85 (2H), (m, aromatics). Anal. Calcd for C28H31Cl3NPPdRu 3 0.5CH2Cl2: C, 44.5; H, 4.2; N, 1.9. Found: C, 44.8; H, 4.4; N, 2.2. For 6: Mp: 227-228 °C dec. [R]D þ447.5 (c 0.6, CHCl3). 31P{1H} NMR (CDCl3, δ): 22.8 (s). 1H NMR (CDCl3, δ): 1,39 (d, 3JHH = 7.0 Hz, 3H, NCHMe); 1.46 (d, 4 JPH = 2.8 Hz, 3H, CdC-Me); 2.26 (d, 4JPH = 3.5 Hz, 3H, PCCMe); 2.65 (3H), 3.16 (3H) (s, NMe); 4.28 (q, 3JHH = 7.0 Hz, 1H, NCHMe); 5.70 (s, 6H, C6H6); 7.16-7.26 (4H), 7.45-7.44 (3H), 8.19-8.25 (2H), (m, aromatics). Anal. Calcd for C28H31Cl3NPPdRu 3 0.5CH2Cl2: C, 44.5; H, 4.2; N, 1.9. Found: C, 44.8; H, 4.4; N, 2.2. Synthesis of Complex 7. Complex 3 (0.042 g, 0.058 mmol) was stirred in a mixed solvent system (DCM, 1 mL; acetone, 5 mL; H2O, 0.5 mL) for 5 days at room temperature. Removal of organic solvent through rotatory evaporation followed by extraction with DCM gave the crude product (organic layer). Subsequent purification by silica gel column chromatography (acetone/DCM, 1:4) followed by precipitation in Et2O gave 7 as a yellow solid. Yield: 0.014 g (34%). Complex 7 was recrystallized from DCM/Et2O as orange prisms. Mp: 240-241 °C dec. 31 P{1H} NMR (CDCl3, δ): 49.8 (s). 1H NMR (CDCl3, δ): 1.71 (d, 4JPH = 1.4 Hz, 3H, CdC-Me); 2.36 (d, 4JPH = 1.3 Hz, 3H, OdC-Me); 2.49 (s, 3H, NMe); 3.00-3.04 (m, 4H, PCH and NMe); 3.24 (2JHH = 11.0 Hz, 1H), 3.99 (2JHH = 11.0 Hz, 1H) (d, NCHH); 5.95 (s, 6H, C6H6); 7.15-7.23 (3H), 7.31-7.44 (4H), 7.59-7.65 (2H) (m, aromatics). Anal. Calcd for C27H30Cl2NOPPdRu 3 H2O: C, 45.6; H, 4.5; N, 2.0. Found: C, 45.6; H, 4.5; N, 2.0. Synthesis of Complex 8. Complex 8 was prepared following the same procedure as that reported for 7. Complex 5 (0.041 g, 0.057 mmol) was stirred in a mixed solvent system (DCM, 1 mL; acetone, 5 mL; H2O, 0.5 mL) for 7 days at room temperature. Removal of organic solvent through rotatory evaporation followed by extraction with DCM gave the crude product (organic layer). Subsequent purification by silica gel column chromatography (acetone/DCM, 1:4) followed by precipitation in Et2O gave 8 as a yellow solid. Yield: 0.012 g (30%). Complex 8 was recrystallized from DCM/Et2O as orange prisms. Mp: 235236 °C dec. [R]D -30.0 (c 0.5, CHCl3). 31P{1H} NMR (CDCl3, δ): 50.0 (s). 1H NMR (CDCl3, δ): 1,45 (d, 3JHH = 7.0 Hz, 3H, NCHMe); 1.71 (d, 4JPH = 1.8 Hz, 3H, CdC-Me); 2.35 (d, 4JPH = 1.6 Hz, 3H, OdC-Me); 2.50 (s, 3H, NMe); 2.98 (s, 1H, PCH); 3.10 (s, 3H, NMe); 4.30 (q, 3JHH = 7.0 Hz, 1H, NCHMe);

5.97 (d, 3JPH = 0.9 Hz, 6H, C6H6); 7.10-7.13 (1H), 7.22-7.33 (3H), 7.35-7.45 (3H), 7.55-7.62 (2H) (m, aromatics). Anal. Calcd for C28H32Cl2NOPPdRu 3 H2O: C, 46.3; H, 4.7; N, 1.9. Found: C, 46.1; H, 4.7; N, 2.0. Synthesis of Complex 9. Complex 9 was prepared following the same procedure as that reported for 7. Complex 6 (0.065 g, 0.090 mmol) was stirred in a mixed solvent system (DCM, 1.5 mL; acetone, 7.5 mL; H2O, 0.8 mL) for 10 days at room temperature. Removal of organic solvent through rotatory evaporation followed by extraction with DCM gave the crude product (organic layer). Subsequent purification by silica gel column chromatography (acetone/DCM, 1:4) followed by precipitation in Et2O gave 9 as a yellow solid. Yield: 0.008 g (13%). Mp: 236-237 °C dec. [R]D þ56.7 (c 0.6, CHCl3). 31P{1H} NMR (CDCl3, δ): 49.7 (s). 1 H NMR (CDCl3, δ): 1,81-1.83 (m, 6H, NCHMe and CdC-Me); 2.37 (d, 4JPH = 1.7 Hz, 3H, OdC-Me); 2.68 (s, 3H, NMe); 2.94 (s, 3H, NMe); 3.14 (s, 1H, PCH); 3.22 (q, 3JHH = 6.7 Hz, 1H, NCHMe); 6.02 (d, 3JPH = 0.6 Hz, 6H, C6H6); 7.03-7.04 (1H), 7.09-7.10 (1H), 7.15-7.18 (1H), 7.25-7.28 (1H), 7.347.43 (3H), 7.62-7.66 (2H) (m, aromatics). Anal. Calcd for C28H32Cl2NOPPdRu: C, 47.5; H, 4.6; N, 2.0. Found: C, 47.1; H, 4.5; N, 1.9. Attempted Hydration in an Acidic Solvent System. The acidic solvent system was prepared by mixing DCM, acetone, and the diluted HCl solution of various concentrations in a ratio of ca. 2:10:1. The following is the attempted hydration of complex 3 in the mixed solvent system containing 1 equiv of HCl. Complex 3 (0.040 g, 0.056 mmol) was stirred in a mixed solvent system (DCM, 2 mL; acetone, 10 mL; HCl solution of 0.05 M, 1.2 mL) at room temperature. No hydration product was observed after 7 days, when the peak of complex 3 disappeared in the 31P{1H} NMR spectrum of the reaction mixture. Hydration in a Basic Solvent System. The basic solvent system was prepared by mixing DCM, acetone, and the diluted NaOH solution of various concentrations in a ratio of ca. 2:10:1. The following is the attempted hydration of complex 3 in the mixed solvent system containing 2 equiv of NaOH. Complex 3 (0.042 g, 0.059 mmol) was stirred in a mixed solvent system (DCM, 2 mL; acetone, 10 mL; NaOH solution of 0.13 M, 1 mL) for 2 days at room temperature until the 31P{1H} NMR spectrum of the reaction mixture indicated that the conversion had been completed. Removal of organic solvent through rotatory evaporation followed by extraction with DCM gave the crude product (organic layer). Subsequent purification by silica gel column chromatography (acetone/DCM, 1:4) followed by precipitation in Et2O gave 7 as a yellow solid. Yield: 0.012 g (30%).

Article Crystal Structure Determination of (RRuSP)-3/(SRuRP)-3, 5, 6, 7, and 8. X-ray crystallographic data for the involved complexes are given in Table 7. Diffraction data were collected on a Bruker X8Apex diffractometer with Mo KR radiation (graphite monochromator). All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were introduced at fixed distance from carbon atoms and were assigned fixed thermal parameters.

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Acknowledgment. We are grateful to Nanyang Technological University for supporting this research and for the research scholarship to D.L. Supporting Information Available: Crystallographic data in CIF format for complexes (RRuSP)-3/(SRuRP)-3, 5, 6, 7, and 8. This material is available free of charge via the Internet at http:// pubs.acs.org.