- Synthesis, electronic structure and reactivity of bis(imino)pyridine iron carbene complexes: Evidence for a carbene radical
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The reactivity of the disubstituted diazoalkane, N2CPh 2 with a family of bis(imino)pyridine iron dinitrogen complexes was examined. For the most sterically protected member of the series, ( iPrPDI)Fe(N2)2 (iPrPDI = 2,6-(2,6-iPr2C6H3NCMe) 2C5H3N), an S = 1 iron diazoalkane complex was obtained and structurally characterized. Reducing the size of the 2,6-aryl substituents to ethyl or methyl groups resulted in isolation of bis(imino)pyridine iron carbene complexes. Magnetic measurements established S = 1 ground states, demonstrating rare examples of iron carbenes in a weak ligand field. Electronic structure determination using metrical parameters from X-ray diffraction as well as Moessbauer, XAS and computational data established high-spin iron(ii) compounds engaged in antiferromagnetic coupling with redox-active bis(imino)pyridine and carbene radicals. The Royal Society of Chemistry 2014.
- Russell, Sarah K.,Hoyt, Jordan M.,Bart, Suzanne C.,Milsmann, Carsten,Stieber, S. Chantal E.,Semproni, Scott P.,Debeer, Serena,Chirik, Paul J.
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p. 1168 - 1174
(2014/03/21)
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- Oxo/Imido heterometathesis reactions catalyzed by a silica-supported tantalum imido complex
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Grafting Ta(=NtBu)(CH2CMe2Ph)3 onto the surface of silica partially dehydroxylated at 300°C leads to the formation of the surface imido complex (≡SiO)2Ta(=N tBu)(CH2CMe2Ph) as a major species, which was characterized with EXAFS, 13C CP/MAS NMR, diffuse reflectance FTIR, elemental analyses, and chemical reactivity. The obtained material acts as an efficient heterogeneous catalyst for various oxo/imido heterometathesis transformations: imidation of ketones and DMF with N-sulfinylamines and condensation of N-sulfinylamines into sulfurdiimines and phenyl isocyanate into diphenylcarbodiimide.
- Zhizhko, Pavel A.,Zhizhin, Anton A.,Belyakova, Olga A.,Zubavichus, Yan V.,Kolyagin, Yuriy G.,Zarubin, Dmitry N.,Ustynyuk, Nikolai A.
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supporting information
p. 3611 - 3617
(2013/07/26)
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- Amination reactions of aryl halides with nitrogen-containing reagents mediated by palladium/imidazolium salt systems
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Nucleophilic N-heterocyclic carbenes have been conveniently used as catalyst modifiers in amination reactions involving aryl chlorides, aryl bromides, and aryl iodides with various nitrogen-containing substrates. The scope of a coupling process using a Pd(0) or Pd(II) source and an imidazolium salt in the presence of a base, KOtBu or NaOH, was tested using various substrates. The Pd2(dba)3/IPr·HCl (1, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) system presents the highest activity with respect to electron-neutral and electron-rich aryl chlorides. The ligand is also effective for the synthesis of benzophenone imines, which can be easily converted to the corresponding primary amines by acid hydrolysis. Less reactive indoles were converted to N-aryl-substituted indoles using as supporting ligand the more donating SIPr·HCl (5, SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene). The Pd(OAc)2/SIPr·HCl/NaOH system is efficient for the N-arylation of diverse indoles with aryl bromides. The general protocol developed has been applied successfully to the synthesis of a key intermediate in the synthesis of an important new antibiotic. Mechanistically, palladium-to-ligand ratio studies strongly support an active species bearing one nucleophilic carbene ligand.
- Grasa,Viciu,Huang,Nolan
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p. 7729 - 7737
(2007/10/03)
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