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排序方式: 共有117条查询结果,搜索用时 93 毫秒
91.
van der Vlugt JI Pidko EA Vogt D Lutz M Spek AL Meetsma A 《Inorganic chemistry》2008,47(11):4442-4444
The versatile coordination behavior of the PNP ligands 1A (2,6-bis[(di-tert-butylphosphino)methyl]pyridine) and 1B (2,6-bis[(diphenylphosphino)methyl]pyridine) to CuI is described, whereby a hemilabile interaction of the pyridine N-donor atom to the copper center resulted in a rare T-shaped complex with 1A, while with 1B also a tetracoordinated species could be isolated. Theoretical calculations support the weak interaction of the pyridine N donor in 1A with the Cu center. 相似文献
92.
A straightforward synthesis toward the preparation of the rigid pyrazolate ligand L(H) featuring bipyridyl side-arms is described, starting from 2,2'-bipyridyl-N-oxide as the sole organic building block. In this context, optimized procedures for the synthesis of the organic intermediates 6-acetyl-2,2'-bipyridine 1 and 6-methylcarboxy-2,2'-bipyridine 2 are reported. The new ligand comprises two proximate terpyridine-like binding sites and is shown to form discrete [2 x 2]-grid complexes with CoII, MnII, and CuII in a highly selective self-assembly process, even in the presence of excess metal precursor. The thus obtained complexes [Co4L4][Na(NO3)4](NO3) (3), [Mn4L4](PF6)4 (4), and [Cu4L4](ClO4)4 (5) are fully characterized, including X-ray crystallographic analyses, and their magnetic properties are discussed. All three complexes show weak to moderate antiferromagnetic coupling between the four nuclei. The stability of the grid structures proved very high, as dissociation or exchange between metal ions in solution was not observed in a set of competition experiments. 相似文献
93.
Nicolaas P. van Leest Prof. Dr. Jarl Ivar van der Vlugt Prof. Dr. Bas de Bruin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):371-378
The cobalt species PPh4[CoIII(TAMLred)] is a competent and stable catalyst for the sulfimidation of (aryl)(alkyl)-substituted sulfides with iminoiodinanes, reaching turnover numbers up to 900 and turnover frequencies of 640 min−1 under mild and aerobic conditions. The sulfimidation proceeds in a highly chemoselective manner, even in the presence of alkenes or weak C−H bonds, as supported by inter- and intramolecular competition experiments. Functionalization of the sulfide substituent with various electron-donating and electron-withdrawing arenes and several alkyl, benzyl and vinyl fragments is tolerated, with up to quantitative product yields. Sulfimidation of phenyl allyl sulfide led to [2,3]-sigmatropic rearrangement of the initially formed sulfimide species to afford the corresponding N-allyl-S-phenyl-thiohydroxylamines as attractive products. Mechanistic studies suggest that the actual nitrene transfer to the sulfide proceeds via (previously characterized) electrophilic nitrene radical intermediates that afford the sulfimide products via electronically asynchronous transition states, in which SET from the sulfide to the nitrene radical complex precedes N−S bond formation in a single concerted process. 相似文献
94.
Mutulis F Gogoll A Mutule I Yahorava S Yahorau A Liepinsh E Wikberg JE 《Molecules (Basel, Switzerland)》2008,13(8):1846-1863
Two molecules of indole derivative, e.g. indole-5-carboxylic acid, reacted with one molecule of thiol, e.g. 1,2-ethanedithiol, in the presence of trifluoroacetic acid to yield adducts such as 3-[2-(2-amino-5-carboxyphenyl)-1-(2-mercaptoethylthio)ethyl]-1Hindole-5-carboxylic acid. Parallel formation of dimers, such as 2,3-dihydro-1H,1'H-2,3'-biindole-5,5'-dicarboxylic acid and trimers, such as 3,3'-[2-(2-amino-5-carboxyphenyl) ethane-1,1-diyl]bis(1H-indole-5-carboxylic acid) of the indole derivatives was also observed. Reaction of a mixture of indole and indole-5-carboxylic acid with 2-phenylethanethiol proceeded in a regioselective way, affording 3-[2-(2-aminophenyl)-1-(phenethylthio)ethyl]-1H-indole-5-carboxylic acid. An additional product of this reaction was 3-[2-(2-aminophenyl)-1-(phenethylthio)ethyl]-2,3-dihydro-1H,1'H-2,3'-biindole-5'-carboxylic acid, which upon standing in DMSO-d6 solution gave 3-[2-(2-aminophenyl)-1-(phenethylthio)ethyl]-1H,1'H-2,3'-biindole-5'-carboxylic acid. Structures of all compounds were elucidated by NMR, and a mechanism for their formation was suggested. 相似文献
95.
Prof. Dr. Jarl Ivar van der Vlugt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(11):2651-2662
Controlled ligand-based redox-activity and chemical non-innocence are rapidly gaining importance for selective (catalytic) processes. This Concept aims to provide an overview of the progress regarding ligand-to-substrate single-electron transfer as a relatively new mode of operation to exploit ligand-centered reactivity and catalysis based thereon. 相似文献
96.
97.
Minghui Zhou Marianne Lankelma Jarl Ivar van der Vlugt Bas de Bruin 《Angewandte Chemie (International ed. in English)》2020,59(27):11073-11079
The metalloradical activation of o‐aryl aldehydes with tosylhydrazide and a cobalt(II) porphyrin catalyst produces cobalt(III)‐carbene radical intermediates, providing a new and powerful strategy for the synthesis of medium‐sized ring structures. Herein we make use of the intrinsic radical‐type reactivity of cobalt(III)‐carbene radical intermediates in the [CoII(TPP)]‐catalyzed (TPP=tetraphenylporphyrin) synthesis of two types of 8‐membered ring compounds; novel dibenzocyclooctenes and unprecedented monobenzocyclooctadienes. The method was successfully applied to afford a variety of 8‐membered ring compounds in good yields and with excellent substituent tolerance. Density functional theory (DFT) calculations and experimental results suggest that the reactions proceed via hydrogen atom transfer from the bis‐allylic/benzallylic C?H bond to the carbene radical, followed by two divergent processes for ring‐closure to the two different types of 8‐membered ring products. While the dibenzocyclooctenes are most likely formed by dissociation of o‐quinodimethanes (o‐QDMs) which undergo a non‐catalyzed 8π‐cyclization, DFT calculations suggest that ring‐closure to the monobenzocyclooctadienes involves a radical‐rebound step in the coordination sphere of cobalt. The latter mechanism implies that unprecedented enantioselective ring‐closure reactions to chiral monobenzocyclooctadienes should be possible, as was confirmed for reactions mediated by a chiral cobalt‐porphyrin catalyst. 相似文献
98.
Well‐Defined Dinuclear Gold Complexes for Preorganization‐Induced Selective Dual Gold Catalysis
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Vincent Vreeken Dr. Daniël L. J. Broere Anne C. H. Jans Marianne Lankelma Prof. Dr. Joost N. H. Reek Dr. Maxime A. Siegler Dr. Jarl Ivar van der Vlugt 《Angewandte Chemie (International ed. in English)》2016,55(34):10042-10046
The synthesis, reactivity, and potential of well‐defined dinuclear gold complexes as precursors for dual gold catalysis are explored. Using the preorganizing abilities of the ditopic PNHPiPr ( LH ) ligand, dinuclear AuI–AuI complex 1 and mixed‐valent AuI–AuIII complex 2 provide access to structurally characterized chlorido‐bridged cationic species 3 and 4 upon halide abstraction. For 2 , this transformation involves unprecedented two‐electron oxidation of the redox‐active ligand, generating a highly rigidified environment for the Au2 core. Facile reaction with phenylacetylene affords the σ,π‐activated phenylacetylide complex 5 . When applied in the dual gold heterocycloaddition of a urea‐functionalized alkyne, well‐defined precatalyst 3 provides high regioselectivities for the anti‐Markovnikov product, even at low catalyst loadings, and outperforms common mononuclear AuI systems. This proof‐of‐concept demonstrates the benefit of preorganization of two gold centers to enforce selective non‐classical σ,π‐activation with bifunctional substrates. 相似文献
99.
100.
CH Activation of Benzene by a Photoactivated NiII(azide): Formation of a Transient Nickel Nitrido Complex
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Vincent Vreeken Dr. Maxime A. Siegler Prof. Dr. Bas de Bruin Prof. Dr. Joost N. H. Reek Dr. Martin Lutz Dr. Ir. Jarl Ivar van der Vlugt 《Angewandte Chemie (International ed. in English)》2015,54(24):7055-7059
Photochemical activation of nickel‐azido complex 2 [Ni(N3)(PNP)] (PNHP=2,2′‐di(isopropylphosphino)‐4,4′‐ditolylamine) in neat benzene produces diamagnetic complex 3 [Ni(Ph)(PNPNH)], which is crystallographically characterized. DFT calculations support photoinitiated N2‐loss of the azido complex to generate a rare, transient NiIV nitrido species, which bears significant nitridyl radical character. Subsequent trapping of this nitrido through insertion into the Ni? P bond generates a coordinatively unsaturated NiII imidophosphorane P?N donor. This species shows unprecedented reactivity toward 1,2‐addition of a C? H bond of benzene to form 3 . The structurally characterized chlorido complex 4 [Ni(Cl)(PNPNH)] is generated by reaction of 3 with HCl or by direct photolysis of 2 in chlorobenzene. This is the first report of aromatic C? H bond activation by a trapped transient nitrido species of a late transition metal. 相似文献