| Abstract
| - The bis(dihydrogen) ruthenium complex RuH2(H2)2(PCy3)2 (1) and the ethylene complexRuΗ(C2Η4)[P(η3-C6H8)Cy2](PCy3) (2), obtained by addition of ethylene to 1, catalyze efficientlythe silylation of ethylene with HSiMe2SiMe2H (I) and with the series of disilanes HSiMe2(CH2)nSiMe2H (n = 2, II; n = 3, III; n = 4, IV). Reaction of I with ethylene produces themonosilanes (CH2CH)SiMe2(CH2CH3) (I.b) and (CH3CH2)SiMe2(CH2CH3) (I.c) resultingfrom the cleavage of the Si−Si bond and the functionalization of the Si−H bonds. For II−IV, three processes, hydrosilylation, dehydrogenative silylation, and cyclization, are incompetition, leading to the formation of acyclic monofunctionalized intermediates HSiMe2(CH2)nSiMe2(CHCH2) (II.f−IV.f) and HSiMe2(CH2)nSiMe2(CH2CH3) (II.g−IV.g), acyclicdifunctionalized compounds (CH2CH)SiMe2(CH2)nSiMe2(CHCH2) (II.a−IV.a), (CH2CH)SiMe2(CH2)nSiMe2(CH2CH3) (II.b−IV.b), and (CH2CH3)SiMe2(CH2)nSiMe2(CH2CH3) (II.c−IV.c), together with cyclic products [(SiMe2)(CH2)3(SiMe2)](CHCH2) (II.d−IV.d) and[(SiMe2)(CH2)3(SiMe2)](CH2CH3) (II.e−IV.e). Kinetic studies reveal a consecutive reactionpath for the formation of acyclic difunctionalized compounds via the monofunctionalizedintermediates. Saturated and unsaturated cyclic products form concurrently to monofunctionalized disilanes. The rates and the selectivity of the reactions are dramatically influencedby the chain length between the two silicon atoms, the fastest conversion and the highestconcentration of vinyl products being observed in the case of a long chain. In contrast,formation of cyclic compounds is favored for n = 2 or 3. Mechanistic studies show thatdifferent complexes are obtained, depending on the order of addition of ethylene and disilane.In the presence of the disilane II, 2 converts into a mixture of RuH2{(η2-HSiMe2)2(CH2)2}(PCy3)2 (3a) and RuH2(SiMe2(CH2)2SiMe2H){P(η3-C6H8)Cy2}(PCy3) (6). In contrast, in thepresence of ethylene, RuH2{(η2-HSiMe2)2(CH2)n}(PCy3)2 (n = 2, 3a; n = 3, 3b), leads to theformation of a new ethylene complex RuH2(C2H4)2(PCy3)2 (4). Compound 4 is ultimatelyconverted to 2 after total consumption of the liberated disilane. All these complexes areinvolved in the catalytic processes.
- The ruthenium-catalyzed silylation of ethylene with various disilanes was investigated. Kinetic and mechanistic studies showed the competition between hydrosilylation, dehydrogenative silylation, and cyclization and the involvement of several complexes in these catalytic processes.
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