Chain-Selective and Regioselective Ethylene and Styrene Dimerization Reactions Catalyzed by a Well-Defined Cationic Ruthenium-Hydride Complex: New Insights on the Styrene Dimerization Mechanism

Authors

Do W. Lee, Marquette UniversityFollow
Chae S. Yi, Marquette UniversityFollow

Document Type

Article

Language

eng

Format of Original

5 p.

Publication Date

8-9-2010

Publisher

American Chemical Society

Source Publication

Organometallics

Source ISSN

0276-7333

Original Item ID

DOI: 10.1021/om100468q

Abstract

The cationic ruthenium hydride complex [(η⁶-C₆H₆)(PCy₃)(CO)RuH]⁺BF₄⁻ was found to be a highly regioselective catalyst for the ethylene dimerization reaction to give 2-butene products (TOF = 1910 h⁻¹, >95% selectivity for 2-butenes). The dimerization of styrene exclusively produced the head-to-tail dimer (E)-PhCH(CH₃)CH═CHPh at an initial turnover rate of 2300 h⁻¹. A rapid and extensive H/D exchange between the vinyl hydrogens of styrene-d₈ and 4-methoxystyrene was observed within 10 min without forming the dimer products at room temperature. The inverse deuterium isotope effect of k_H/k_D = 0.77 ± 0.10 was measured from the first-order plots on the dimerization reaction of styrene and styrene-d₈ in chlorobenzene at 70 °C. The pronounced carbon isotope effect on both vinyl carbons of styrene as measured by using Singleton’s method (¹³C(recovered)/¹³C(virgin) at C₁ = 1.096 and C₂ = 1.042) indicates that the C−C bond formation is the rate-limiting step for the dimerization reaction. The Eyring plot of the dimerization of styrene in the temperature range of 50−90 °C led to ΔH^⧧ = 3.3(6) kcal/mol and ΔS^⧧ = −35.5(7) eu. An electrophilic addition mechanism has been proposed for the dimerization of styrene.

Comments

Accepted version. Organometallics, Vol. 29, No. 15 (August 2010): 3413-3417. DOI. © 2010 American Chemical Society. Used with permission.

Recommended Citation

Lee, Do W. and Yi, Chae S., "Chain-Selective and Regioselective Ethylene and Styrene Dimerization Reactions Catalyzed by a Well-Defined Cationic Ruthenium-Hydride Complex: New Insights on the Styrene Dimerization Mechanism" (2010). Chemistry Faculty Research and Publications. 408.
https://epublications.marquette.edu/chem_fac/408