C–H Activation DOI: 10.1002/anie.200603582 ANewCatalyticRoutefortheActivationof sp-Hybridized Carbon–Hydrogen Bonds** BogdanMarciniec,*BeataDudziec,and IreneuszKownacki In the last two decades we have developed a new type of transition-metal (TM)-catalyzed reaction of vinyl-substituted organosilicon compounds with olefins, known as a silylative coupling (SC, or trans-silylation; Scheme 1), that is comple- mentarytometathesis.Thisreactionoccursbycleavageofthe = C  Hbondofanolefinandthe = C  Sibondofavinylsilane, incontrasttocross-metathesis,whichusesthesamesubstrates andalsogivesthesameproducts(exceptthe gem-isomer),by cleavage of the C =C bond. Various TM complexes (i.e. Ru, Rh, Ir, and Co) containing an MHandMSi bond initially, or one generated in situ, catalyze this process. [1,2] ) ThemechanismforSCcatalyzedbyrutheniumcomplexes elucidated by Wakatsuki [3] andbyus [4] involves insertion of a vinylsilaneintotheMHbondand b-Sitransfertothemetal, with elimination of ethylene, to generate MSi species, then insertionofthealkeneintotheMSibondand b-Htransferto the metal, with elimination of a substituted vinylsilane as product, and regeneration of the catalyst. TheSCprocessunderoptimumconditionshasbecomean excellent synthetic tool for the regio- and stereoselective synthesis of functionalized vinylsilicon compounds such as (E)-N-(silyl)vinylcarbazole, [5a] amides, [5b] 1-silyl-1-(boryl)- ethenes, [5c] functionalized cyclosiloxanes, cyclosilazanes, [5d] and silsesquioxanes [5e] as well as macromolecular organo- silicon compounds containing (E)-1,2-bis(silyl)fragments. [6] These compounds can be used as synthetic reagents for organicsynthesisandasmaterialsprecursorsandaredifficult to prepare by other TM-catalyzed reactions such as cross- metathesis. The trans-silylation reaction has recently been extended to other metalloids such as boron [7] and germa- nium. [8] The catalytic addition of the = C  H bond in aromatic ketones, esters, and amines to vinylsilanes has been reported by Murai etal. to yield compounds of the type ArCH 2 CH 2 SiR 3 . [9a,b] These authors have also reported a [Ru 3 (CO) 12 ]-catalyzed coupling (silylation) of 3-acetylthio- phene with trimethylvinylsilane that gives 3-acetyl-2-(trime- thylsilyl)thiophene (64%, toluene, 20 h, 115 8C), [9c] and Park et al. have reported a rhodium-catalyzed silylation of benzyl alcohol with trimethylvinylsilane that yields a siloxy deriva- tive(93%,toluene,2h,200 8C). [9d] Ethylene was produced in both reactions as a secondary product. In view of all the results cited above it is worth emphasizing that the vinyl- silicon compounds function as a silylating agent and a hydrogen acceptor. Hereinwepresentanewcatalyticreactionthatinvolvesa coupling of terminal alkynes with vinylsilanes of the general formula H 2 C =CHSiR 3 (where SiR 3 is SiMe 2 Ph, Si(OEt) 3 , SiMe(OSiMe 3 ) 2 , and SiMe 2 (OSiMe 3 ) as well as divinyltetra- methyldisiloxane and divinyltetramethyldisilazane), which, byanalogy,canbeconsideredasilylativecouplingofalkynes and which proceeds in the presence of complexes containing [Ru] H and/or [Ru] Si bonds, such as [RuHCl(CO)(PCy 3 ) 2 ] (I, Cy = cyclohexyl), [RuHCl(CO)(iPr 3 ) 2 ](II), [RuH(CO)- (MeCN) 2 (PCy 3 ) 2 ][BF 4 ](III), [Ru(SiMe 3 )Cl(CO)(PPh 3 ) 2 ] (IV), [10] and [RuHCl(CO)(PPh 3 ) 3 ](V), and leads to the evolution of ethylene and formation of the silyl-substituted derivatives (Scheme2). Interestingly, the hexacoordinate complex V appears to be inactive in this reaction. Substituted alkynylsilanes are commonly used as alkyny- lating agents in the synthesis of organic and natural prod- Scheme 1. Silylative coupling of olefins with vinylsilanes. Scheme 2. Coupling of terminal alkynes with vinylsilanes. [*] Prof.Dr. B. Marciniec, B. Dudziec, Dr. I. Kownacki Department of Organometallic Chemistry Faculty of Chemistry, Adam Mickiewicz University Grunwaldzka 6, 60-780 Poznan (Poland) Fax:(+ 48)618-291-508 E-mail: Bogdan.Marciniec@amu.edu.pl [**] Financial support from the Ministry of Science and Higher Education (Poland) (grants 3T09A 145 26 and PBZ-KBN 118/T09/ 17) is gratefully acknowledged. Supporting Information for this article is available on the WWW under http://www.angewandte.org or from the author. Communications 8180 # 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. Int. Ed. 2006, 45, 8180 –8184