F:Highly flammable;646-04-8Relevant articles and documents
Mechanism of alkene isomerization by bifunctional ruthenium catalyst: A theoretical study
Tao, Jingcong,Sun, Fengshen,Fang, Tao
, p. 1 - 6 (2012)
The molecular mechanism of the isomerization of 1-pentene to form (E)-2-pentene catalyzed by the bifunctional ruthenium catalyst has been investigated using density functional theory calculations. The reaction is likely to proceed through the following steps: 1) the β-H elimination to generate the ruthenium hydride intermediate; 2) the reductive elimination of the hydride intermediate to generate the nitrogen-protonated allyl intermediate; 3) the transportation of the hydrogen by the dihedral rotation with Ru-P bond acting as axis; 4) the oxidative addition to afford another hydride complex; 5) the reductive elimination of the hydride intermediate to form the C 2-C3 π-coordinated agostic intermediate; 6) the coordination of the nitrogen to the ruthenium center to give the final product. The rate-determining step is the oxidative addition step (the process of the hydrogen moves to ruthenium center from the nitrogen atom) with the free energy of 31.2 kcal/mol in the acetone solvent. And the N-heterocyclic ligand in the catalyst mainly functions in the two aspects: affords an important internal-basic center (nitrogen atom) and works as a transporter of hydrogen. Our results would be helpful for experimentalists to design more effective bifunctional catalysts for isomerization of a variety of heterofunctionalized alkene derivatives.
Designing and synthesis of phosphine derivatives of Ru3(CO)12 – Studies on catalytic isomerization of 1-alkenes
Pandya, Chayan,Panicker, Rakesh R.,Senjaliya, Parth,Hareendran, M.K. Hima,Anju,Sarkar, Sibasis,Bhat, Haamid,Jha, Prakash C.,Rao, Koya Prabhakara,Smith, Gregory S.,Sivaramakrishna, Akella
, (2021/01/12)
A comparative investigation on the isomerization reactions of 1-alkenes to their corresponding 2-alkenes catalyzed Ru3(CO)12 (1), Ru3(CO)9(PEt3)3 (2) and Ru3(CO)10(dppe) (3), (where dppe = 1,2-bis(diphenylphosphino)ethane) is described. Both the complexes of types 2 and 3 were characterized by all analytical and spectroscopic data. The molecular structure of 2 was confirmed by single-crystal X-ray analysis. It is observed that the nature of phosphine ligands plays an important role in the isomerization of 1-alkenes. When the chelated diphosphine is used, the internal isomerization reaction by [Ru3(CO)10(dppe)] (3) is completed relatively in less time compared to other derivatives. As per the DFT calculations, the observed reaction rate for the alkene isomerization may be explained based on the relative stability of 1, 2, and 3. The CO abstraction step is highly feasible in 3, the least stable among the three, thus the reaction occurs at the highest rate. Due to the increased relative stability from 2 to 1, the reaction requires more time at elevated temperatures and the rate decreases as a consequence.
C-F activation reactions at germylium ions: Dehydrofluorination of fluoralkanes
Braun, Thomas,Mei?ner, Gisa,Rachor, Simon G.,Talavera, Maria
supporting information, p. 4452 - 4455 (2020/05/13)
Reactions of the trityl cations with germanes afford the germylium ions [R3Ge][B(C6F5)4] (1a: R = Et, 1b: R = Ph, 1c: R = nBu). These compounds react with germane or fluorogermane to give polynuclear species, which are sources of the mononuclear ions, The latter convert with phosphines to yield the [R3Ge-PR3]+ (4a: R = Et, 4b: R = Ph) cations. Catalytic dehydrofluorination reactions were observed for the C-F bond activation of fluoroalkanes when using germanes as hydrogen source.
Bimolecular Coupling as a Vector for Decomposition of Fast-Initiating Olefin Metathesis Catalysts
Bailey, Gwendolyn A.,Foscato, Marco,Higman, Carolyn S.,Day, Craig S.,Jensen, Vidar R.,Fogg, Deryn E.
supporting information, p. 6931 - 6944 (2018/05/14)
The correlation between rapid initiation and rapid decomposition in olefin metathesis is probed for a series of fast-initiating, phosphine-free Ru catalysts: the Hoveyda catalyst HII, RuCl2(L)(=CHC6H4-o-OiPr); the Grela catalyst nG (a derivative of HII with a nitro group para to OiPr); the Piers catalyst PII, [RuCl2(L)(=CHPCy3)]OTf; the third-generation Grubbs catalyst GIII, RuCl2(L)(py)2(=CHPh); and dianiline catalyst DA, RuCl2(L)(o-dianiline)(=CHPh), in all of which L = H2IMes = N,N′-bis(mesityl)imidazolin-2-ylidene. Prior studies of ethylene metathesis have established that various Ru metathesis catalysts can decompose by β-elimination of propene from the metallacyclobutane intermediate RuCl2(H2IMes)(κ2-C3H6), Ru-2. The present work demonstrates that in metathesis of terminal olefins, β-elimination yields only ca. 25-40% propenes for HII, nG, PII, or DA, and none for GIII. The discrepancy is attributed to competing decomposition via bimolecular coupling of methylidene intermediate RuCl2(H2IMes)(=CH2), Ru-1. Direct evidence for methylidene coupling is presented, via the controlled decomposition of transiently stabilized adducts of Ru-1, RuCl2(H2IMes)Ln(=CH2) (Ln = pyn′; n′ = 1, 2, or o-dianiline). These adducts were synthesized by treating in situ-generated metallacyclobutane Ru-2 with pyridine or o-dianiline, and were isolated by precipitating at low temperature (-116 or -78 °C, respectively). On warming, both undergo methylidene coupling, liberating ethylene and forming RuCl2(H2IMes)Ln. A mechanism is proposed based on kinetic studies and molecular-level computational analysis. Bimolecular coupling emerges as an important contributor to the instability of Ru-1, and a potentially major pathway for decomposition of fast-initiating, phosphine-free metathesis catalysts.
