Organolanthanides in the catalysis of the hydrosilylation of olefins and ketones

Reactivity of Lanthanide and Yttrium Hydrides and Hydrocarbyls toward Organosilicon Hydrides and Related Compounds

“…Reactivity of Lanthanide and Yttrium Hydrocarbyls toward Organosilicon and Organoelement Hydrides. Recently, we described the synthesis of lutetium hydride {(C 5 H 5 ) 2 Lu(μ-H)(THF)} 2 upon treatment of (C 5 H 5 ) 2 LuC 6 H 4 Me-4(THF) with PhMeSiH 2 in benzene at ambient temperature . Here, we have found that a similar reaction readily proceeds with various unsolvated dimeric hydrocarbyls 1 − 5 .…”

“…On the other hand, in this paper we have shown that bis(cyclopentadienyl)lanthanide hydrocarbyls containing C 5 H 5 , t BuC 5 H 4 , Me 3 SiC 5 H 4 , and even C 5 Me 5 ligands react readily with silanes to form the products of nucleophilic substitution at silicon and the corresponding lanthanide hydrides (pathway c and eq 1). ,,, This reaction is a very convenient route for the synthesis of the corresponding lanthanide hydrides, which are difficult to prepare. In regard to reaction conditions, both {Cp 2 Ln(μ-H)} 2 and {Cp 2 LnH(THF)}, where Cp = C 5 H 5 , t BuC 5 H 4 , or Me 3 SiC 5 H 4 , were prepared in a high yield.…”

“…In regard to reaction conditions, both {Cp 2 Ln(μ-H)} 2 and {Cp 2 LnH(THF)}, where Cp = C 5 H 5 , t BuC 5 H 4 , or Me 3 SiC 5 H 4 , were prepared in a high yield. A similar reaction is suggested to be a key stage of the catalytic cycle of olefin hydrosilylation catalyzed by organolanthanides. − ,15a,− In contrast, complexes with permethylcyclopentadienyl ligands (C 5 Me 5 ) 2 LnCH(SiMe 3 ) 2 react with silanes in a different manner to form the corresponding compounds with Ln−Si bonds. 8a,15b However, Tilley et al recently showed that this reaction is not a single-step process. 8b The compound with Ln−Si bonding is formed by the reaction of silane with the hydride (C 5 Me 5 ) 2 LnH, which is generated by the hydrogenolysis of the former lanthanide hydrocarbyl with traces of H 2 .…”

“…On the contrary, structure B corresponds to the transfer of the silyl group to the metal atom, leading to the formation of a compound with Ln−Si bonding and the corresponding hydrocarbon (pathway b). This structure corresponds to the transition state of σ-bond metathesis, which was studied earlier for early transition metal complexes and silanes (as well as H 2 or hydrocarbons). − As this duality evoked some discussion, − , we have performed MO calculations for the alternative reaction pathways involving transformations of several simple molecules. The calculations indicate a silyl group transfer to the metal atom, i.e., formation of methane and the corresponding compound with Ln−Si bonding, is preferred over the hydride transfer (like eq 1) found in the reaction of (C 5 H 5 ) 2 YMe with SiH 4 in the gas phase.…”

“…This method involves reaction of the corresponding lanthanide hydrocarbyls with silanes (eq 1, Cp = C 5 H 5 , Cp‘, Cp‘‘) or with organohydrides of some nontransition metals This reaction was suggested by this group , and Marks to be a key stage of the catalytic cycle of olefin hydrosilylation catalyzed by organolanthanides.…”