skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Structure–Reactivity Studies, Characterization, and Transformation of Intermediates by Lithium Chloride in the Direct Insertion of Alkyl and Aryl Iodides to Metallic Zinc Powder

Abstract

Employment of fluorophore-tagged alkyl and aryl iodides permitted detection of persistent surface intermediates during their direct insertion to commercially available zinc powder. The sensitivity of this subensemble microscopy technique enabled structure–reactivity studies in the formation of intermediates that are present in quantities sufficiently low as to have been undetected previously by traditional ensemble analytical techniques. In these surface intermediates we transformed them using lithium chloride, which lead to the assignment of the mechanistic role of lithium chloride as changing the rate-determining step in the reaction by lowering the barrier for solubilization of these otherwise persistent surface organometallic intermediates. The temperature dependence/qualitative barrier of the direct insertion step was determined independently from the solubilization step and from the barrier for the overall reaction. Detection of these zinc surface intermediates at the single-molecule level, i.e., of individual surface organometallic species, has been achieved for the first time. Energy dispersive X-ray spectroscopy (EDS) measurements of the elemental composition of the surface of the zinc powder determined that lithium chloride does not clean the surface of the oxides; instead, pretreatment of the surface with TMSCl effects partial removal of surface oxides after the 2 h pretreatment time previously reported in the empirically optimized syntheticmore » procedure. The current limitations of this microscopy approach are also determined and discussed with respect to the addition of solid reagents during in operando imaging. Characterization of the resulting soluble fluorophore-tagged organozinc/LiCl complex by 1H NMR spectroscopy, mass spectrometry, and fluorescence spectroscopy provided insight into its solution dynamics and chemical exchange processes.« less

Authors:
 [1];  [1]; ORCiD logo [1]
  1. Univ. of California, Irvine, CA (United States). Dept. of Chemistry
Publication Date:
Research Org.:
Univ. of California, Irvine, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1342413
Alternate Identifier(s):
OSTI ID: 1372302
Grant/Contract Number:
FG02-08ER15994; CHE-1464959; CHE-082913
Resource Type:
Journal Article: Published Article
Journal Name:
Organometallics
Additional Journal Information:
Journal Volume: 36; Journal Issue: 13; Journal ID: ISSN 0276-7333
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Feng, Chao, Easter, Quinn T., and Blum, Suzanne A.. Structure–Reactivity Studies, Characterization, and Transformation of Intermediates by Lithium Chloride in the Direct Insertion of Alkyl and Aryl Iodides to Metallic Zinc Powder. United States: N. p., 2017. Web. doi:10.1021/acs.organomet.6b00910.
Feng, Chao, Easter, Quinn T., & Blum, Suzanne A.. Structure–Reactivity Studies, Characterization, and Transformation of Intermediates by Lithium Chloride in the Direct Insertion of Alkyl and Aryl Iodides to Metallic Zinc Powder. United States. doi:10.1021/acs.organomet.6b00910.
Feng, Chao, Easter, Quinn T., and Blum, Suzanne A.. Fri . "Structure–Reactivity Studies, Characterization, and Transformation of Intermediates by Lithium Chloride in the Direct Insertion of Alkyl and Aryl Iodides to Metallic Zinc Powder". United States. doi:10.1021/acs.organomet.6b00910.
@article{osti_1342413,
title = {Structure–Reactivity Studies, Characterization, and Transformation of Intermediates by Lithium Chloride in the Direct Insertion of Alkyl and Aryl Iodides to Metallic Zinc Powder},
author = {Feng, Chao and Easter, Quinn T. and Blum, Suzanne A.},
abstractNote = {Employment of fluorophore-tagged alkyl and aryl iodides permitted detection of persistent surface intermediates during their direct insertion to commercially available zinc powder. The sensitivity of this subensemble microscopy technique enabled structure–reactivity studies in the formation of intermediates that are present in quantities sufficiently low as to have been undetected previously by traditional ensemble analytical techniques. In these surface intermediates we transformed them using lithium chloride, which lead to the assignment of the mechanistic role of lithium chloride as changing the rate-determining step in the reaction by lowering the barrier for solubilization of these otherwise persistent surface organometallic intermediates. The temperature dependence/qualitative barrier of the direct insertion step was determined independently from the solubilization step and from the barrier for the overall reaction. Detection of these zinc surface intermediates at the single-molecule level, i.e., of individual surface organometallic species, has been achieved for the first time. Energy dispersive X-ray spectroscopy (EDS) measurements of the elemental composition of the surface of the zinc powder determined that lithium chloride does not clean the surface of the oxides; instead, pretreatment of the surface with TMSCl effects partial removal of surface oxides after the 2 h pretreatment time previously reported in the empirically optimized synthetic procedure. The current limitations of this microscopy approach are also determined and discussed with respect to the addition of solid reagents during in operando imaging. Characterization of the resulting soluble fluorophore-tagged organozinc/LiCl complex by 1H NMR spectroscopy, mass spectrometry, and fluorescence spectroscopy provided insight into its solution dynamics and chemical exchange processes.},
doi = {10.1021/acs.organomet.6b00910},
journal = {Organometallics},
number = 13,
volume = 36,
place = {United States},
year = {Fri Feb 03 00:00:00 EST 2017},
month = {Fri Feb 03 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1021/acs.organomet.6b00910

Citation Metrics:
Cited by: 2works
Citation information provided by
Web of Science

Save / Share:
  • Employment of fluorophore-tagged alkyl and aryl iodides permitted detection of persistent surface intermediates during their direct insertion to commercially available zinc powder. The sensitivity of this subensemble microscopy technique enabled structure–reactivity studies in the formation of intermediates that are present in quantities sufficiently low as to have been undetected previously by traditional ensemble analytical techniques. In these surface intermediates we transformed them using lithium chloride, which lead to the assignment of the mechanistic role of lithium chloride as changing the rate-determining step in the reaction by lowering the barrier for solubilization of these otherwise persistent surface organometallic intermediates. The temperaturemore » dependence/qualitative barrier of the direct insertion step was determined independently from the solubilization step and from the barrier for the overall reaction. Detection of these zinc surface intermediates at the single-molecule level, i.e., of individual surface organometallic species, has been achieved for the first time. Energy dispersive X-ray spectroscopy (EDS) measurements of the elemental composition of the surface of the zinc powder determined that lithium chloride does not clean the surface of the oxides; instead, pretreatment of the surface with TMSCl effects partial removal of surface oxides after the 2 h pretreatment time previously reported in the empirically optimized synthetic procedure. The current limitations of this microscopy approach are also determined and discussed with respect to the addition of solid reagents during in operando imaging. Characterization of the resulting soluble fluorophore-tagged organozinc/LiCl complex by 1H NMR spectroscopy, mass spectrometry, and fluorescence spectroscopy provided insight into its solution dynamics and chemical exchange processes.« less
  • The synthesis, characterization, and use of soluble polyethylene- and polystyrene-bound tin chlorides as catalysts for the reduction of alkyl halides using a suspension of sodium borohydride in toluene and a crown ether as a phase-transfer catalyst are described. These tin-containing soluble macromolecules were synthesized by anionic oligomerization of ethylene or styrene followed by electrophilic substitution of the resulting living oligomer with various organic tin halides including tin tetrachloride, n-butyltin trichloride, di-n-butyltin dichloride, and diphenyltin dichloride. The resulting oligomer-bound tin reagents were characterized by {sup 1}H and {sup 119}Sn NMR spectroscopy, and the tin content of the oligomers was analyzed bymore » ICP analysis. Typically the tin reagents were used as cocatalysts (ca. 10%) along with 10-20% of a crown ether as a phase-transfer catalyst in reductions of primary, secondary, and aryl halides using a suspension of sodium borohydride in hot toluene at 110{degree}C. Kinetic studies showed that the reaction rate was dependent on the concentration of the tin catalyst and that secondary halides reacted slightly faster than primary halides.« less
  • This paper reports the migratory insertion chemistry of indenyliridium complexes described in the companion paper. Complexes of general formula ({eta}{sup 5}-Ind)(PMe{sub 3})Ir(R)(R{prime}), where R = alkyl or aryl and R{prime} = alkyl, aryl, or hydride (4-6) react with dative ligands L such as tert-butylisocyanide and CO. These transformations lead to {eta}{sup 5} to {eta}{sup 1} isomerization of the indenyl ligand, giving octahedral iridium complexes of general formula ({eta}{sup 1}-Ind)(PMe{sub 3})(L){sub 2}Ir(R)(R{prime}) (8, 9, 11). Treatment of the methyl aryl and dimethyl {eta}{sup 1}-indenyl complexes 9a, 9d, and 9e with trimethylamine oxide removes CO, allowing the indenyl ligand to reestablish {eta}{supmore » 5}-coordination by inducing CO migratory insertion to give acyl complexes 10. Reaction of {eta}{sup 1}-indenyl aryl and methyl hydrides 6 (as well as the dihydride ({eta}{sup 5}-Ind)(PMe{sub 3})IrH{sub 2} (7)) with CO leads to reductive elimination of arene, methane, or H{sub 2} rather than migratory insertion, forming ({eta}{sup 1}-Ind)-(CO){sub 3}(PMe{sub 3})Ir (12) as the organometallic product. In contrast, treatment of methyl and aryl hydrides 6 with alkynes leads to the methyl vinyl complexes ({eta}{sup 5}-Ind)(PMe{sub 3})Ir(Me)(CR{double_prime}C(R{prime})(H)) (13) and reaction of 6a with ethylene gives the methyl ethyl complex ({eta}{sup 5}-Ind)(PMe{sub 3})Ir(Me)(Et) (14). Isotope labeling, stereochemical, and kinetic studies have been carried out on the insertion reaction of 6a with 3,3-dimethyl-1-butyne. The results of these experiments are most consistent with a mechanism involving initial reversible coordination of alkyne to the metal center (probably with concurrent {eta}{sup 5}-{eta}{sup 3} isomerization of the indenyl ligand) followed by irreversible migration of the metal-bound hydrogen to the tert-butyl-substituted carbon of the alkyne and then rapid recoordination of the indenyl group. 22 refs., 3 figs., 2 tabs.« less
  • /sup 6/Li, /sup 13/C, and /sup 15/N NMR spectroscopic studies of lithium diphenylamide in THF/hydrocarbon solutions (THF = tetrahydrofuran) detected two different species. /sup 6/Li and /sup 15/N NMR spectroscopic studies of (/sup 6/Li, /sup 15/N)lithium diphenylamide showed the species observed at low THF concentrations to be a cyclic oligomer. Structural analogies provided strong support for a dimer while colligative measurements at 0/degrees/C indicated the dimer to be di- or trisolvated. On the basis of the observed mass action effects, the species appearing at intermediate THF concentrations is assigned as a contact or solvent-separated ion-paired monomer. Lithium diphenylamide forms amore » 1:1 adduct with lithium bromide at low THF concentrations. A combination of /sup 6/Li-/sup 15/N double labeling studies and colligative measurements supports a trisolvated cyclic mixed dimer structure. Although detailed spectroscopic studies at elevated THF concentrations were precluded by high fluctionality, the similarity of the /sup 13/C chemical shifts of lithium diphenylamide in the presence and absence of lithium bromide provide indirect evidence that the mixed dimer undergoes a THF concentration dependent dissociation to the monomeric amide and free lithium bromide. 24 references, 9 figures, 2 tables.« less