Counteranion and solvent assistance in ruthenium-mediated alkyne to vinylidene isomerizations

Manuel Jiménez-Tenorio*, M. Carmen Puerta, Pedro Valerga, Manuel A. Ortuño, Gregori Ujaque, Agustí Lledós

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

29 Citations (Scopus)

Abstract

The complex [Cp*RuCl(iPr2PNHPy)] (1) reacts with 1-alkynes HCî -CR (R = COOMe, C6H4CF 3) in dichloromethane furnishing the corresponding vinylidene complexes [Cp*Ru =C =CHR(iPr2PNHPy)]Cl (R = COOMe (2a-Cl), C6H4CF3 (2b-Cl)), whereas reaction of 1 with NaBPh4 in MeOH followed by addition of HCî -CR (R = COOMe, C6H4CF3) yields the metastable π-alkyne complexes [Cp*Ru(η2-HCî -CR)( iPr2PNHPy)][BPh4] (R = COOMe (3a-BPh 4), C6H4CF3 (3b-BPh4)). The transformation of 3a-BPh4/3b-BPh4 into their respective vinylidene isomers in dichloromethane is very slow and requires hours to its completion. However, this process is accelerated by addition of LiCl in methanol solution. Reaction of 1 with HCî -CR (R = COOMe, C 6H4CF3) in MeOH goes through the intermediacy of the π-alkyne complexes [Cp*Ru(η2-HCî -CR)( iPr2PNHPy)]Cl (R = COOMe (3a-Cl), C6H 4CF3 (3b-Cl)), which rearrange to vinylidenes in minutes, i.e., much faster than their counterparts containing the [BPh4] - anion. The kinetics of these isomerizations has been studied in solution by NMR. With the help of DFT studies, these observations have been interpreted in terms of chloride- and methanol-assisted hydrogen migrations. Calculations suggest participation of a hydrido-alkynyl intermediate in the process, in which the hydrogen atom can be transferred from the metal to the β-carbon by means of species with weak basic character acting as proton shuttles.

Original languageEnglish
Pages (from-to)8919-8932
Number of pages14
JournalINORGANIC CHEMISTRY
Volume52
Issue number15
DOIs
Publication statusPublished - 5 Aug 2013

Fingerprint

Dive into the research topics of 'Counteranion and solvent assistance in ruthenium-mediated alkyne to vinylidene isomerizations'. Together they form a unique fingerprint.

Cite this