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Synthesis, Structure and Reactivity of Neutral Hydrogen-Substituted 5082 Organometallics 2009, 28, 5082–5089 DOI: 10.1021/om900348m Synthesis, Structure, and Reactivity of Neutral Hydrogen-Substituted Ruthenium Silylene and Germylene Complexes Paul G. Hayes,† Rory Waterman,‡ Paul B. Glaser,§ and T. Don Tilley* Department of Chemistry, University of California, Berkeley, California 94720-1460. †Current address: Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada, T1K 3M4. ‡ Current address: Department of Chemistry, University of Vermont, Burlington, Vermont 05405. §Current address: General Electric Global Research, Niskayuna, NY 12309. Received May 3, 2009 i Reaction of Cp*( Pr2MeP)RuCl (1) with 0.5 equiv of Mg(CH2Ph)2(THF)2 afforded the benzyl i 3 complex Cp*( Pr2MeP)Ru(η -CH2Ph) (2). Complex 2 readily reacted with primary silanes H3SiR F i F (R = trip, dmp, Mes ; trip = 2,4,6- Pr3-C6H2, dmp = 2,6-Mes2-C6H3,Mes = 2,4,6-(CF3)3-C6H2) i to liberate toluene and afford hydrogen-substituted silylene complexes Cp*( Pr2MeP)(H)RudSiH(R) [R = trip, 3;dmp,4;MesF, 5]. Complexes 3-5 exhibit characteristic SiH 1H NMR resonances downfield 2 of 8 ppm and very small JSiH coupling constants (8-10 Hz). The solid state structures of complexes 3 and 5 feature short Ru-Si distances of 2.205(1) and 2.1806(9) A˚, respectively, and planar silicon centers. In i addition, the silylene complex Cp*( Pr2MeP)(H)RudSiPh(trip) (6) and the unusual, chlorine-substituted i species Cp*( Pr2MeP)(H)RudSiCl(R) [R = trip, 7;dmp,8] were prepared. Hydrogen-substituted i ruthenium germylene complex Cp*( Pr2MeP)(H)RudGeH(trip) (9) was prepared similarly by reaction of 2 with tripGeH3. Complex 9 is the first structurally characterized ruthernium germylene complex and ˚ has a remarkably short Ru-Ge distance of 2.2821(6) A. Complex 9 adds H2OacrossitsRudGe bond to i give Cp*( Pr2MeP)(H)2RuGeH(OH)(trip) (10). i Introduction hydrogen-substituted ruthenium complex [Cp*( Pr3P)(H)2- RudSiHPh 3 Et2O][B(C6F5)4], which efficiently catalyzes the d 0 5 Transition metal silylene complexes (LnM SiRR ) that hydrosilylation of alkenes. Key characteristics of this reac- formally possess a metal-silicon double bond represent tion include the requirement for primary silane substrates, a unsaturated silicon compounds featuring chemical and phy- compatibility with highly substituted alkenes, exclusive anti- 1 sical properties of fundamental interest. These complexes Markovnikov regiochemistry, and cis stereochemistry for offer interesting comparisons to the better known carbene the Si-H addition. These features are inconsistent with the complexes and have been proposed to play important roles well-known Chalk-Harrod6 and Lewis acid7 mechanisms as intermediates in a variety of catalytic reactions such as the for alkene hydrosilylation, and mechanistic5,8 and theore- 2 synthesis of methylchlorosilanes by the Direct Process, the tical9 investigations are consistent with a catalytic cycle 3 redistribution of substituents at silicon, and the transfer of that features the direct addition of an Si-H bond to 4 silylene fragments to an unsaturated carbon-carbon bond. the alkene. In this cycle, a silylene unit is transferred It was not until recently, however, that direct evidence for from RSiH3 to the metal center (silylene extrusion) via participation of a metal silylene complex in a catalytic two Si-Hbondactivations,anSi-H oxidative transformation was obtained. This catalysis involves the addition followed by an R-hydrogen migration to afford *To whom correspondence may be addressed. Tel: 510-642-8939. E-mail: [email protected]. (5) Glaser, P. B.; Tilley, T. D. J. Am. Chem. Soc. 2003, 125, 13640– (1) Waterman, R.; Hayes, P. G.; Tilley, T. D. Acc. Chem. Res. 2007, 13641. 40, 712–719. (6) (a) Chalk, A. J.; Harrod, J. F. J. Am. Chem. Soc. 1965, 87,16–21. (2) (a) Lewis, K. M., Rethwisch, D. G., Eds. Catalyzed Direct (b) Seitz, F.; Wrighton, M. S. Angew. Chem., Int. Ed. 1988, 27, 289–291. (c) Reactions of Silicon; Elsevier: Amsterdam, 1993. (b) Pachaly, B.; Weis, J. Duckett, S. B.; Perutz, R. N. Organometallics 1992, 11,90–98. (d) Sakaki, In Organosilicon Chemistry III: From Molecules to Materials, Munich S.; Sumimato, M.; Fukuhara, M.; Sugimoto, M.; Fujimoto, H.; Matsuzaki, S. Silicon Days; 1996; Wiley & Sons: New York, 1998; p 478. (c) Brook, M. A. Organometallics 2002, 21, 3788–3802. Silicon in Organic, Organometallic and Polymer Chemistry; Wiley: New (7) (a) Rubin, M.; Schwier, T.; Gevorgyan, N. J. Org. Chem. 2002, 67, York, 2000; p 381. (d) Lewis, L. N. In Chemistry of Organosilicon 1936–1940. (b) Song, Y. S.; Yoo, B. R.; Lee, G. H.; Jung, I. N. Organome- Compounds; Rappoport, Z., Apeloig, Y., Eds.; Wiley: Chichester, UK, tallics 1999, 18, 3109–3115. (c) Lambert, J. B.; Zhao, Y.; Wu, H. W. J. Org. 1998; Pt 2, p 1581. Chem. 1999, 64, 2729–2736. (d) Schmeltzer, J. M.; Porter, L. A.; Stewart, M. (3) (a) Curtis, M. D.; Epstein, P. S. Adv. Organomet. Chem. 1981, 19, P.; Buriak, J. M. Langmuir 2002, 18, 2971–2974. 213–255. (b) Kumada, M. J. J. Organomet. Chem. 1975, 100, 127–138. (8) Hayes, P. G.; Beddie, C.; Hall, M. B.; Waterman, R.; Tilley, T. D. (4) Some recent examples include: (a) Franz, A. K.; Woerpel, K. A. J. J. Am. Chem. Soc. 2006, 128, 428–429. Am. Chem. Soc. 1999, 121, 949–957. (b) Palmer, W. S.; Woerpel, K. A. (9) (a) Beddie, C.; Hall, M. B. J. Am. Chem. Soc. 2004, 126, 13564– Organometallics 2001, 20, 3691–3697. (c) Cirakovic, J.; Driver, T. G.; 13565. (b) Beddie, C.; Hall, M. B. J. Phys. Chem. A 2006, 110, 1416. (c) Woerpel, K. A. J. Am. Chem. Soc. 2002, 124, 9370–9371. Bohme,€ U. J. Organomet. Chem. 2006, 691, 4400–4410. pubs.acs.org/Organometallics Published on Web 08/07/2009 r 2009 American Chemical Society Article Organometallics, Vol. 28, No. 17, 2009 5083 Scheme 1 i [Cp*( Pr3P)(H)2RudSiHR][B(C6F5)4]. Direct addition of Chart 1 2 0 the sp Si-Hbondtoanalkene(e.g.,CH2dCHR )then i gives a disubstituted silylene complex, [Cp*( Pr3P)(H)2- 0 RudSi(CH2CH2R )(R)][B(C6F5)4]. Migration of hydrogen from the metal center to silicon and reductive elimination of the new silane molecule complete the catalytic cycle (Scheme 1).5,8-10 i Although the related osmium complex [Cp*( Pr3P)(H)2- i OsdSiH(trip)][B(C6F5)4] (trip = 2,4,6- Pr3C6H2) is not cat- to further probe structure, bonding, and reactivity of alytically active toward the hydrosilylation of alkenes, stoi- MdSiH(R) and related MdGeH(R) neutral complexes, a chiometric alkene insertion into the Si-H bond is series of ruthenium complexes have been prepared via ex- exceedingly rapid, even at -78 °C.5 Interestingly, neutral trusion reactions promoted by the benzyl complex Cp*- i η3 analogues of this osmium silylene complex, conveniently ( Pr2MeP)Ru( -CH2Ph) (2). i prepared via reaction of Cp*( Pr3P)OsCH2Ph with primary silanes, do not react with alkenes even at elevated tempera- Results and Discussion tures.8 Computational studies indicate that the much lower reactivity of these Cp*(iPr P)(H)OsdSiH(R) complexes to- Synthesis of the Ruthenium Benzyl Complex Cp*- 3 i η3 ward alkenes is related to their higher degree of covalent ( Pr2MeP)Ru( -CH2Ph)(2). The initial objective of this double-bond character and a small localization of positive study was to develop a general silane activation process 11h charge onto silicon (second resonance structure of Chart 1).8 leading to silylene-hydride complexes. In this regard, allyl 8,11g Nonetheless, neutral, hydrogen-substituted silylene com- and benzyl complexes may serve as convenient starting η3 η1 plexes are expected to display a rich reaction chemistry that materials because facile -to- transformations of the is distinct from that of cationic analogues.5,8,11 In an attempt ligand provide an empty coordination site that may be used for activation of an Si-H bond. Subsequent C-H reductive elimination then produces an unsaturated M-SiHRR0 inter- – (10) Brunner, H. Angew. Chem., Int. Ed. 2004, 43, 2749 2750. mediate, which can undergo R-migration to provide the final (11) (a) Sakaba, H.; Hirata, T.; Kabuto, C.; Kabuto, K. Organome- tallics 2006, 25, 5145–5150. (b) Watanabe, T.; Hashimoto, H.; Tobita, H. J. silylene complex. This process was envisioned as a general Am. Chem. Soc. 2007, 129, 11338–11339. (c) Watanabe, T.; Hashimoto, H.; route to neutral ruthenium silylene complexes (Scheme 2). Tobita, H. J. Am. Chem. Soc. 2006, 128, 2176–2177. (d) Ochiai, M.; i Unlike the osmium analogue Cp*( Pr3P)OsBr, reaction of Hashimoto, H.; Tobita, H. Angew. Chem., Int. Ed. 2007, 46, 8192–8194. i (e) Simmons, R. S.; Gallucci, J. C.; Tessier, C. A.; Youngs, W. J. J. Cp*( Pr3P)RuCl with standard benzylating reagents (including Organomet. Chem. 2002, 654, 224–228. (f) Watanabe, T.; Hashimoto, H.; Mg(CH2Ph)2(THF)2,PhCH2MgCl, and KCH2Ph) did not Angew. Chem., Int. Ed. 43 – i Tobita, H. 2004, , 218 221. (g) Mork, B. V.; afford the desired benzyl complex Cp*( Pr3P)RuCH2Ph. Upon Tilley, T. D.; Schultz, A. J.; Cowan, J. A. J. Am. Chem. Soc. 2004, 126, 10428–10440. (h) Feldman, J. D.; Peters, J. D.; Tilley, T. D. J. Am. Chem. combining the reactants in benzene-d6 solution, there was an Soc. 2002, 21, 4065–4075. (i) Glaser, P. B.; Tilley, T. D. Organometallics immediate change in color from dark purple to orange with 2004, 23, 5799–5812. (j) Rankin, M. A.; MacLean, D. F.; Schatte, G.; concomitant disappearance of 1Hand31P NMR signals attrib- McDonald, R.; Stradiotto, M. J. Am. Chem. Soc. 2007, 129, 15855–15864. uted to the starting materials. The observation of 1 equiv of (k) Ochiai, M.; Hashimoto, H.; Tobita, H.
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