CpCo(I)- and CpRu(II)Cl-catalyzed [2+2+2] cycloadditions of siladiynes and alkynes: A combined experimental and theoretical study

Benzo-2-silaindanes (3a-g) and benzo-2,3-tetralines (4a-g) were synthesized by CpCo(CO)2 and Cp*Ru(cod)Cl catalyzed cyclotrimerization of siladiynes (1-2a,b) with alkynes R1C≡CR2 (R1, R2 = H, CO2Me, Ph, Ts). X-ray analyses of 3f and 4g confirmed the formation of silicon-carbon heterocycles (silacycl...

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Published in:	Journal of organometallic chemistry Vol. 905; p. 121006
Main Authors:	Amakasu, Toru, Sato, Keisuke, Ohta, Yusuke, Kitazawa, Genki, Sato, Hidefumi, Oumiya, Kouta, Kawakami, Yoshiteru, Takeuchi, Takae, Kabe, Yoshio
Format:	Journal Article
Language:	English
Published:	Elsevier B.V 01-01-2020
Subjects:	[2+2+2] cycloaddition CpCo(I)-catalyst CpRu(II)Cl-Catalyst Heterocoupling Silacycles Siladiynes CpCo(I)-catalyst Heterocoupling Siladiynes Silacycles CpRu(II)Cl-Catalyst [2+2+2] cycloaddition
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Summary:	Benzo-2-silaindanes (3a-g) and benzo-2,3-tetralines (4a-g) were synthesized by CpCo(CO)2 and CpRu(cod)Cl catalyzed cyclotrimerization of siladiynes (1-2a,b) with alkynes R1C≡CR2 (R1, R2 = H, CO2Me, Ph, Ts). X-ray analyses of 3f and 4g confirmed the formation of silicon-carbon heterocycles (silacycles). The different reactivity of alkynes depend on Co- and Ru-catalysts suggesting the different mechanism. Stoichiometric NMR studies as well as DFT calculations revealed that heterolytic coupling occurs between the siladiyne and alkyne followed by an internal [4+2] cycloaddition for CpCo(I)-catalyzed reactions, whereas CpRu(II)Cl-catalyzed reactions proceeded via homolytic coupling of siladiynes to afford a ruthenacyclopentatriene followed by insertion of the alkynes. Minimum energy crossing point (MECP) calculations for the former heterocoupling reaction disclosed different two-state reaction compared to known two-state one. The latter intermediate was characterized in NMR experiments as the first reported complex of a ruthenacyclopentatriene formed from terminal diyne. [Display omitted] •Silacycles were synthesized by both CpCo(CO)2- and CpRu(cod)Cl-catalyzed cyclotrimerization of siladiynes with alkynes.•Stoichiometric NMR studies as well as DFT calculations for CpCo(I)-catalyzed reactions revealed that heterocoupling occurs between the siladiyne and alkyne.•NMR studies disclosed that CpRu(II)Cl-catalyzed reactions proceeded through homocoupling ruthenacyclopentatriene intermediate.
ISSN:	0022-328X 1872-8561
DOI:	10.1016/j.jorganchem.2019.121006