1387-7003/99/$ - see front matter q1999 Elsevier Science S.A. All rights reserved. PII S1387-7003 ( 99 ) 00150-1 Friday Nov 19 01:16 PM StyleTag -- Journal: INOCHE (Inorganic Chemistry Communications) Article: 288 www.elsevier.nl/locate/inoche Inorganic Chemistry Communications 2 (1999) 581–583 Photochemically induced insertion of an olefin into the Co–Si bond; the key step for silylative coupling with vinylsubstituted organosilicon compounds Bogdan Marciniec *, Ireneusz Kownacki, Dariusz Chadyniak Faculty of Chemistry, Adam Mickiewicz University, 60-780 Poznan, Poland ˜ Received 31 August 1999 Abstract Co(SiEt 3 )(CO) 4 (I) as an example of a Co–Si complex is shown to be a catalyst for silylative coupling of olefins (vinylsilanes, styrene) with vinylsilanes and dimerization of divinylsubstituted silicon compounds(although not as effective as previously reported Ru and Rh complexes). The catalytic and stoichiometric study on the insertion of styrene into the Co–Si bond of I confirms that the mechanism involves the first known b-silyl transfer (from b-silylethylcobalt(I)) to the cobalt atom. q1999 Elsevier Science S.A. All rights reserved. Keywords: Cobalt complexes; Silylative coupling; Vinylsilanes; Organosilicon compounds Table 1 Disproportionation of vinyltrisubstituted silanes catalyzed by I R 3 Conditions Conversion Yield (%) (%) 1 2 Me 3 708C, 24 h 14 6 8 708C, 24 h a 0 – – 808C, 1.5 h 15 6 9 r.t., 48 h 10 4 6 Me 2 Ph 70 o C, 24 h 20 12 8 (EtO) 3 708C, 24 h 16 9 6 [Co]:[Si]s1:200, UV 1 h (lamp 400 W), closed system, Pyrex. a [Co]:[PPh 3 ]s1:2. Ethylene insertion into the Co–Si bond in Co(SiEt 3 )- (CO) 4 (I) was reported by Wrighton and co-workers [1,2] as the rate determining step in the catalytic cycle of olefin hydrosilylation by HSiEt 3 . The insertion of alkenes into M– Si bonds is involved in hydrosilylation and dehydrogenative silylation with hydrosilane pathways [3,4], where M is, for example, Fe [2,5], Ru [6–8], Rh [7,9,10], Ir [11,12] and Os [2]. On the other hand, the insertion of ethylene [13], styrene [14] and vinylsilane [15] into Ru–Si bonds was evidence for new catalytic reactions of olefins with vinylsi- lanes (instead of hydrosilanes as in hydrosilylation) occur- ring through the cleavage of the _C–Si bond of vinylsilane and the _C–H bond of the olefin (silyl group transfer)[14] (Eq. (1)). (1) We have recently reported that rhodium complexes (e.g. [RhH(CO)(PPh 3 ) 3 ]) also catalyze the process according to the presented equation [16]. Therefore, in order to provide evidence for the generality of this process catalyzed by transition metal complexes we * Corresponding author. Tel.: q48 61 8659651; fax: q48 61 8659568; e-mail: marcinb@main.amu.edu.pl have tested Co(SiEt 3 )(CO) 4 (I) as a precursor in the dis- proportionation of vinylsilanes and divinyl-substituted orga- nosilicon compounds and their co-disproportionation with styrene. The conversion of vinylsilanes (and styrene) as well as the yield and the selectivity of the products are presented in Tables 1 and 2. The reactions occur exclusively if the reactant is given a prior UV irradiation. Although the self- disproportionation of vinylsilanes is not so effective as in the presence of ruthenium [14,15] and rhodium [16] catalysts, no side products of the hydrogenation of vinylsilane are