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
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.