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Bergman HM, Beattie DD, Handford RC, Rossomme E, Suslick BA, Head-Gordon M, Cundari TR, Liu Y, Tilley TD. Copper(III) Metallacyclopentadienes via Zirconocene Transfer and Reductive Elimination to an Isolable Phenanthrocyclobutadiene. J Am Chem Soc 2022; 144:9853-9858. [PMID: 35604847 DOI: 10.1021/jacs.2c02581] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Despite the widespread use of copper catalysis for the formation of C-C bonds, debate about the mechanism persists. Reductive elimination from Cu(III) is often invoked as a key step, yet examples of its direct observation from isolable complexes remain limited to only a few examples. Here, we demonstrate that incorporation of bulky mesityl (Mes) groups into the α-positions of a phenanthrene-appended zirconacyclopentadiene, Cp2Zr(2,5-Mes2-phenanthro[9,10]C4), enables efficient oxidative transmetalation to the corresponding, formal Cu(III) metallacyclopentadiene dimer. The dimer was quantitatively converted to a structurally analogous anionic monomer [nBu4N]{Cl2Cu(2,5-Mes2-phenanthro[9,10]C4)} upon treatment with [nBu4N][Cl]. Both metallacycles undergo quantitative reductive elimination upon heating to generate phenanthrocyclobutadiene and a Cu(I) species. Due to the steric protection provided by the mesityl groups, this cyclobutadiene was isolated and thoroughly characterized to reveal antiaromaticity comparable to that of free cyclobutadiene, which imbues it with a small highest occupied molecular orbital-lowest unoccupied molecular orbital energy gap of 1.85 eV and accessible reduced and oxidized electronic states.
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Affiliation(s)
- Harrison M Bergman
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - D Dawson Beattie
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Rex C Handford
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Elliot Rossomme
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.,Kenneth S. Pitzer Center for Theoretical Chemistry, University of California, Berkeley, California 94720, United States.,Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Benjamin A Suslick
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Martin Head-Gordon
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.,Kenneth S. Pitzer Center for Theoretical Chemistry, University of California, Berkeley, California 94720, United States.,Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Thomas R Cundari
- Department of Chemistry, Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Denton, Texas 76203, United States
| | - Yi Liu
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - T Don Tilley
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
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de Urzedo APFM, Diniz MER, Nascentes CC, Catharino RR, Eberlin MN, Augusti R. Photolytic degradation of the insecticide thiamethoxam in aqueous medium monitored by direct infusion electrospray ionization mass spectrometry. J Mass Spectrom 2007; 42:1319-25. [PMID: 17902104 DOI: 10.1002/jms.1204] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Photodegradation of the insecticide thiamethoxam (1), 3-[(2-chloro-5-thiazolyl)methyl]tetrahydro-5-methyl-N-nitro-4H-1,3,5-oxadiazin-4-imine, in an aqueous medium was monitored by electrospray ionization mass spectrometry in the positive ion mode, ESI(+)-MS. An aqueous solution of (1) was incessantly exposed to a UV radiation source and aliquots were taken after reaction times of 1, 2, 3, and 4 h. Analysis by GC/NCI-MS revealed that (1) was continuously degraded under these experimental conditions. However, the total organic carbon (TOC) content remained practically constant during the exposition period, thereby indicating that 1 was not mineralized but continuously converted into other compounds. ESI(+)-MS monitoring revealed that whereas the intensity of the ions of m/z 292/294 ([1 + H](+)) constantly decreased, there was the emergence of other ions of m/z 247/249, 197, 168, and 116 whose intensities simultaneously increased. Their structures were proposed on the basis of: (1) the data of their ESI(+)-MS/MS; (2) their high resolution m/z values; and (3) a plausible reactivity of the thiamethoxam molecule exposed to UV radiation in aqueous solution. Finally, these data allowed us to suggest a reaction route for the photodegradation of 1 in an aqueous medium.
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Affiliation(s)
- Ana P F M de Urzedo
- Department of Chemistry, Federal University of Minas Gerais, Belo Horizonte, MG 31270-901, Brazil
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Abstract
In this experiment, a series of thermal reactions of 4,4'-disubstituted 2,2'-bis(phenylethynyl)biphenyls with 2,3,4,5-tetraphenylcyclopenta-2,4-dienone were carried out under neat conditions and in diphenyl ether at temperatures between 260 and 270 degrees C to give rise to 9,10,11,12,13,14-hexaphenylcycloocta[l]phenanthrenes as the adducts in 12-23% yields. We traced these results to the intramolecular [2 + 2] thermal cyclization of 2,2'-bis(phenylethynyl)biphenyls to form 1,2-diphenylcyclobuta[l]phenanthrenes, which were further trapped as bridged-ketone Diels-Alder adducts, followed by thermal decarbonylative ring opening, which gave rise to the products.
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Affiliation(s)
- Chung-Chieh Lee
- Department of Chemistry and Institute of Polymer Science and Engineering, National Taiwan University, 1 Section 4, Roosevelt Road, Taipei 106, Taiwan
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