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Structure and reactivity of alkynyl ruthenium alkylidenes.

ABSTRACT: The isolation and structural characterization of alkynyl Ru-alkylidene species has been elusive owing to their rapid metallotropic shift and fast turnover. The enyne ring-closing metathesis and relay metathesis provides the platform to form a variety of alkynyl Ru-alkylidene species possessing a sterically and electronically different substituent on the carbenic carbon, which allowed their regio-controlled trapping and structural characterization.

SUBMITTER: Yun SY

PROVIDER: S-EPMC2636511 | biostudies-literature | 2009 Jan

REPOSITORIES: biostudies-literature

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Structure and reactivity of alkynyl ruthenium alkylidenes.

Yun Sang Young SY Kim Mansuk M Lee Daesung D Wink Donald J DJ

Journal of the American Chemical Society 20090101 1

The isolation and structural characterization of alkynyl Ru-alkylidene species has been elusive owing to their rapid metallotropic shift and fast turnover. The enyne ring-closing metathesis and relay metathesis provides the platform to form a variety of alkynyl Ru-alkylidene species possessing a sterically and electronically different substituent on the carbenic carbon, which allowed their regio-controlled trapping and structural characterization. ...[more]

PMID: 19093858

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Project description:Iron-catalyzed cross-coupling reactions using alkynyl nucleophiles represent an attractive approach for the incorporation of alkynyl moieties into organic molecules. In the present study, a multitechnique approach combining inorganic spectroscopic methods, inorganic synthesis, and reaction studies is applied to iron-SciOPP catalyzed alkynyl-alkyl cross-couplings, providing the first detailed insight into the effects of variation from sp2- to sp-hybridized nucleophiles on iron speciation and reactivity. Reaction studies demonstrate that reaction of FeBr2(SciOPP) with 1 equiv (triisopropylsilyl)ethynylmagnesium bromide (TIPS-CC-MgBr) leads to a distribution of mono-, bis-, and tris-alkynylated iron(II)-SciOPP species due to rapid alkynyl ligand redistribution. While solvents such as THF promote these complex redistribution pathways, nonpolar solvents such as toluene enable increased stabilization of these iron species and further enabled assessment of their reactivity with electrophile. While the tris-alkynylated iron(II)-SciOPP species was found to be unreactive with the cycloheptyl bromide electrophile over the average turnover time of catalysis, the in situ formed neutral mono- and bis-alkynylated iron(II)-SciOPP complexes are consumed upon reaction with the electrophile with concomitant generation of cross-coupled product at catalytically relevant rates, indicating the ability of one or both of these species to react selectively with the electrophile. The nature of the reaction solvent and Grignard reagent addition rate were found to have broader implications in overall reaction selectivity, reaction rate, and accessibility of off-cycle iron(I)-SciOPP species. Additionally, the effects of steric substitution of the alkynyl Grignard reagent on catalytic performance were investigated. Fundamental insight into iron speciation and reactivity with alkynyl nucleophiles reported herein provides an essential foundation for the continued development of this important class of reactions.

Dataset Information

Structure and reactivity of alkynyl ruthenium alkylidenes.

Publications

Structure and reactivity of alkynyl ruthenium alkylidenes.

Similar Datasets

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