1-octene hydrosilylation catalyzed by lanthanide and yttrium hydrides and hydrocarbyls: A mechanistic study and the role of catalyst association

Citation
Az. Voskoboynikov et al., 1-octene hydrosilylation catalyzed by lanthanide and yttrium hydrides and hydrocarbyls: A mechanistic study and the role of catalyst association, ORGANOMETAL, 20(13), 2001, pp. 2794-2801
Citations number
64
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
ORGANOMETALLICS
ISSN journal
02767333 → ACNP
Volume
20
Issue
13
Year of publication
2001
Pages
2794 - 2801
Database
ISI
SICI code
0276-7333(20010625)20:13<2794:1HCBLA>2.0.ZU;2-7
Abstract
Dimeric lanthanide (Tb, Yb, Lu) and yttrium hydrides, {Cp ' (2)Ln(mu -H)}(2 ), where Cp ' = t-BUC5H4, and hydrocarbyls {Cp ' (2)Ln(mu -Me)}(2), as well as compounds with different bridging, Cp ' (2)Ln(mu -H)(mu -Me)LnCp ' (2), are efficient and selective catalysts of 1-octene hydrosilylation. Binucle ar complexes with Ln(mu -H)(2)Ln and Ln(mu -H)(mu -Alkyl)Ln bridging fragme nts were found to be the key intermediates in 1-octene hydrosilylation cata lyzed by both the hydrides {Cp ' ,Ln(mu -H)}(2) (Ln = Y, Tb, Yb, Lu) and th e mixed compounds Cp ' (2)Ln(mu -H)(mu -Me)LnCp '2 (Ln = Y, Lu) in benzene at 75 degrees. Therefore, in this case, the dissociation of the starting di meric organolanthanide into monomeric species is not required for the catal ytic reaction to proceed. Under the conditions employed, the rate law for t he hydrosilylation of 1-octene with PhMeSiH2 is V-HS similar to [lanthanide ](1)[olefin](1)[silane](0), suggesting rapid hydride transfer from silane t o Ln and the rate-limiting addition of Ln-H to olefin. The hydrosilylation of 1-octene with n-Bu2SiH2 is accompanied by olefin dimerization. In the pr esence of Ph3SiH, Ph2MeSiH, PhMe2SiH, Et3SiH, and Et3GeH, only the dimeriza tion of 1-octene was observed. Alternatively, the lanthanide and yttrium hy drocarbyls {Cp ' (2)Ln(mu -Me)}(2) (Ln = Y, Tb, Yb, Lu) exhibit higher cata lytic activity even at room temperature.The initial rate of the 1-octene hy drosilylation with PhMeSiH2 was found to be V-0 similar to [lanthanide](1/2 )[olefin](1)[silane](0). In this case, the hydrosilylation seems to involve the formation of highly active monomeric species Cp ' (2)LnH. After severa l minutes, the hydrosilylation rate sharply decreased because of associatio n of the catalyst.