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1.
A Two‐Coordinate Cobalt(II) Imido Complex with NHC Ligation: Synthesis,Structure, and Reactivity
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Jingzhen Du Linbo Wang Prof. Dr. Meihua Xie Prof. Dr. Liang Deng 《Angewandte Chemie (International ed. in English)》2015,54(43):12640-12644
The synthesis, structural characterization, and reactivity of the first two‐coordinate cobalt complex featuring a metal–element multiple bond [(IPr)Co(NDmp)] ( 4 ; IPr=1,3‐bis(2′,6′‐diisopropylphenyl)imidazole‐2‐ylidene; Dmp=2,6‐dimesitylphenyl) is reported. Complex 4 was prepared from the reaction of [(IPr)Co(η2‐vtms)2] (vtms=vinyltrimethylsilane) with DmpN3. An X‐ray diffraction study revealed its linear C? Co? N core and a short Co? N distance (1.691(6) Å). Spectroscopic characterization and calculation studies indicated the high‐spin nature of 4 and the multiple‐bond character of the Co? N bond. Complex 4 effected group‐transfer reactions to CO and ethylene to form isocyanide and imine, respectively. It also facilitated E? H (E=C, Si) σ‐bond activation of terminal alkyne and hydrosilanes to produce the corresponding cobalt(II) alkynyl and cobalt(II) hydride complexes as 1,2‐addition products. 相似文献
2.
Chemoselective Amination of Propargylic C(sp3)H Bonds by Cobalt(II)‐Based Metalloradical Catalysis
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Prof. Dr. Hongjian Lu Dr. Chaoqun Li Dr. Huiling Jiang Christopher L. Lizardi Prof. Dr. X. Peter Zhang 《Angewandte Chemie (International ed. in English)》2014,53(27):7028-7032
Highly chemoselective intramolecular amination of propargylic C(sp3)? H bonds has been demonstrated for N‐bishomopropargylic sulfamoyl azides through cobalt(II)‐based metalloradical catalysis. Supported by D2h‐symmetric amidoporphyrin ligand 3,5‐DitBu‐IbuPhyrin, the cobalt(II)‐catalyzed C? H amination proceeds effectively under neutral and nonoxidative conditions without the need of any additives, and generates N2 as the only byproduct. The metalloradical amination is suitable for both secondary and tertiary propargylic C? H substrates with an unusually high degree of functional‐group tolerance, thus providing a direct method for high‐yielding synthesis of functionalized propargylamine derivatives. 相似文献
3.
Lin‐Bao Zhang Dr. Xin‐Qi Hao Shou‐Kun Zhang Zhan‐Jiang Liu Xin‐Xiang Zheng Dr. Jun‐Fang Gong Dr. Jun‐Long Niu Prof. Mao‐Ping Song 《Angewandte Chemie (International ed. in English)》2015,54(1):272-275
The cobalt‐catalyzed alkoxylation of C(sp2)? H bonds in aromatic and olefinic carboxamides has been developed. The reaction proceeded under mild conditions in the presence of Co(OAc)2?4H2O as the catalyst and tolerates a wide range of both alcohols and benzamide substrates, including even olefinic carboxamides. In addition, this reaction is the first example of the direct alkoxylation of alkenes through C? H bond activation. 相似文献
4.
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
5.
Sier Sang Tobias Unruh Dr. Serhiy Demeshko Dr. Luis I. Domenianni Nicolaas P. van Leest Dr. Philipp Marquetand Dr. Felix Schneck Dr. Christian Würtele Felix J. de Zwart Prof. Dr. Bas de Bruin Prof. Dr. Dr. h.c. Leticia González Prof. Dr. Peter Vöhringer Prof. Dr. Sven Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):16978-16989
Outer-sphere radical hydrogenation of olefins proceeds via stepwise hydrogen atom transfer (HAT) from transition metal hydride species to the substrate. Typical catalysts exhibit M−H bonds that are either too weak to efficiently activate H2 or too strong to reduce unactivated olefins. This contribution evaluates an alternative approach, that starts from a square-planar cobalt(II) hydride complex. Photoactivation results in Co−H bond homolysis. The three-coordinate cobalt(I) photoproduct binds H2 to give a dihydrogen complex, which is a strong hydrogen atom donor, enabling the stepwise hydrogenation of both styrenes and unactivated aliphatic olefins with H2 via HAT. 相似文献
6.
Jonghoon Choi Yunho Lee 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(21):7012-7016
A three‐coordinate low‐spin cobalt(I) complex generated using a pincer ligand is presented. Since an empty orbital is sterically exposed at the site trans to the N donor of an acridane moiety, the cobalt(I) center accepts the coordination of various donors such as H2 and PhSiH3 revealing σ‐complex formation. At this low‐spin cobalt(I) site, homolysis of H–H and Si?H bonds preferentially occurs via bimolecular hydrogen atom transfer instead of two‐electron oxidative addition. When the resulting CoII–H species was exposed to N2, H2 evolution readily occurs at ambient conditions. These results suggest single‐electron processes are favored at the structurally rigidified cobalt center. 相似文献
7.
A Cobalt(I) Pincer Complex with an η2‐Caryl−H Agostic Bond: Facile C−H Bond Cleavage through Deprotonation,Radical Abstraction,and Oxidative Addition
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Sathiyamoorthy Murugesan Dr. Berthold Stöger Dr. Ernst Pittenauer Prof. Dr. Günter Allmaier Prof. Dr. Luis F. Veiros Prof. Dr. Karl Kirchner 《Angewandte Chemie (International ed. in English)》2016,55(9):3045-3048
The synthesis and reactivity of a CoI pincer complex [Co(?3P,CH,P‐P(CH)PNMe‐iPr)(CO)2]+ featuring an η2‐ Caryl?H agostic bond is described. This complex was obtained by protonation of the CoI complex [Co(PCPNMe‐iPr)(CO)2]. The CoIII hydride complex [Co(PCPNMe‐iPr)(CNtBu)2(H)]+ was obtained upon protonation of [Co(PCPNMe‐iPr)(CNtBu)2]. Three ways to cleave the agostic C?H bond are presented. First, owing to the acidity of the agostic proton, treatment with pyridine results in facile deprotonation (C?H bond cleavage) and reformation of [Co(PCPNMe‐iPr)(CO)2]. Second, C?H bond cleavage is achieved upon exposure of [Co(?3P,CH,P‐P(CH)PNMe‐iPr)(CO)2]+ to oxygen or TEMPO to yield the paramagnetic CoII PCP complex [Co(PCPNMe‐iPr)(CO)2]+. Finally, replacement of one CO ligand in [Co(?3P,CH,P‐P(CH)PNMe‐iPr)(CO)2]+ by CNtBu promotes the rapid oxidative addition of the agostic η2‐Caryl?H bond to give two isomeric hydride complexes of the type [Co(PCPNMe‐iPr)(CNtBu)(CO)(H)]+. 相似文献
8.
Activation of CH Bonds through Oxidant‐Free Photoredox Catalysis: Cross‐Coupling Hydrogen‐Evolution Transformation of Isochromans and β‐Keto Esters
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Ming Xiang Dr. Qing‐Yuan Meng Jia‐Xin Li Yi‐Wen Zheng Chen Ye Dr. Zhi‐Jun Li Dr. Bin Chen Prof. Dr. Chen‐Ho Tung Prof. Dr. Li‐Zhu Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18080-18084
The direct and controlled activation of a C(sp3)?H bond adjacent to an O atom is of particular synthetic value for the conventional derivatization of ethers or alcohols. In general, stoichiometric amounts of an oxidant are required to remove an electron and a hydrogen atom of the ether for subsequent transformations. Herein, we demonstrate that the activation of a C?H bond next to an O atom could be achieved under oxidant‐free conditions through photoredox‐neutral catalysis. By using a commercial dyad photosensitizer (Acr+‐Mes ClO4?, 9‐mesityl‐10‐methylacridinium perchlorate) and an easily available cobaloxime complex (Co(dmgBF2)2?2 MeCN, dmg=dimethylglyoxime), the nucleophilic addition of β‐keto esters to oxonium species, which is rarely observed in photocatalysis, leads to the corresponding coupling products and H2 in moderate to good yields under visible‐light irradiation. Mechanistic studies suggest that both isochroman and the cobaloxime complex quench the electron‐transfer state of this dyad photosensitizer and that benzylic C?H bond cleavage is probably the rate‐determining step of this cross‐coupling hydrogen‐evolution transformation. 相似文献
9.
Self‐assembly properties of Salamo‐type trinuclear Cu(II) and Co(II) complexes based on the regulation of H+/OHˉ
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A novel naphthalenediol‐based bis(salamo)‐type tetraoxime compound (H4L) was designed and synthesized. Two new supramolecular complexes, [Cu3(L)(μ‐OAc)2] and [Co3(L)(μ‐OAc)2(MeOH)2]·4CHCl3 were synthesized by the reaction of H4L with Cu(II) acetate dihydrate and Co(II) acetate dihydrate, respectively, and were characterized by elemental analyses and X‐ray crystallography. In the Cu(II) complex, Cu1 and Cu2 atoms located in the N2O2 sites, and are both penta‐coordinated, and Cu3 atom is also penta‐coordinated by five oxygen atoms. All the three Cu(II) atoms have geometries of slightly distorted tetragonal pyramid. In the Co(II) complex, Co1 and Co3 atoms located in the N2O2 sites, and are both penta‐coordinated with geometries of slightly distorted triangular bipyramid and distorted tetragonal pyramid, respectively, while Co2 atom is hexa‐coordinated by six oxygen atoms with a geometry of slightly distorted octahedron. These self‐assembling complexes form different dimensional supramolecular structures through inter‐ and intra‐molecular hydrogen bonds. The coordination bond cleavages of the two complexes have occurred upon the addition of the H+, and have reformed again via the neutralization effect of the OH?. The changes of the two complexes response to the H+/OH? have observed in the UV–Vis and 1H NMR spectra. 相似文献
10.
Spectroscopic Capture and Reactivity of a Low‐Spin Cobalt(IV)‐Oxo Complex Stabilized by Binding Redox‐Inactive Metal Ions
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Seungwoo Hong Florian F. Pfaff Eunji Kwon Yong Wang Mi‐Sook Seo Eckhard Bill Dr. Kallol Ray Prof. Dr. Wonwoo Nam 《Angewandte Chemie (International ed. in English)》2014,53(39):10403-10407
High‐valent cobalt‐oxo intermediates are proposed as reactive intermediates in a number of cobalt‐complex‐mediated oxidation reactions. Herein we report the spectroscopic capture of low‐spin (S=1/2) CoIV‐oxo species in the presence of redox‐inactive metal ions, such as Sc3+, Ce3+, Y3+, and Zn2+, and the investigation of their reactivity in C? H bond activation and sulfoxidation reactions. Theoretical calculations predict that the binding of Lewis acidic metal ions to the cobalt‐oxo core increases the electrophilicity of the oxygen atom, resulting in the redox tautomerism of a highly unstable [(TAML)CoIII(O.)]2? species to a more stable [(TAML)CoIV(O)(Mn+)] core. The present report supports the proposed role of the redox‐inactive metal ions in facilitating the formation of high‐valent metal–oxo cores as a necessary step for oxygen evolution in chemistry and biology. 相似文献
11.
Nanostructured Cobalt(II) Tetracarboxyphthalocyanine Complex Supported Within the MWCNT Frameworks: Electron Transport and Charge Storage Capabilities
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Sherilee Pillay Jeseelan Pillay Paul M. Ejikeme Katlego Makgopa Kenneth I. Ozoemena 《Electroanalysis》2015,27(7):1707-1718
The electrochemical redox properties of a surface‐confined thin solid film of nanostructured cobalt(II) tetracarboxyphthalocyanine integrated with multiwalled carbon nanotube (nanoCoTCPc/MWCNT) have been investigated. This novel nanoCoTCPc/MWCNT material was characterized using SEM, TEM, zeta analysis and electrochemical methods. The nanoCoTCPc/MWCNT nanohybrid material exhibited an extra‐ordinarily high conductivity (15 mS cm?1), which is more than an order of magnitude greater than that of the MWCNT‐SO3H (527 µS cm?1) and three orders of a magnitude greater than the nanoCoTCPc (4.33 µS cm?1). The heterogeneous electron transfer rate constant decreases as follows: nanoCoTCPc/MWCNT (kapp≈19.73×10?3 cm s?1)>MWCNT‐SO3H (kapp≈11.63×10?3 cm s?1)>nanoCoTCPc (kapp≈1.09×10?3 cm s?1). The energy‐storage capability was typical of pseudocapacitive behaviour; at a current density of 10 µA cm?2, the pseudocapacitance decreases as nanoCoTCPc/MWCNT (3.71×10?4 F cm?2)>nanoCoTCPc (2.57×10?4 F cm?2)>MWCNT‐SO3H (2.28×10?4 F cm?2). The new nanoCoTCPc/MWCNT nanohybrid material promises to serve as a potential material for the fabrication of thin film electrocatalysts or energy‐storage devices. 相似文献
12.
Minghui Zhou Marianne Lankelma Dr. Ir. Jarl Ivar van der Vlugt Prof. Dr. Bas de Bruin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):11166-11172
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
13.
Yi-Hao Chen Shih-Ji Chen Jia-Qi Li Zhenqiang Wu Gene-Hsiang Lee Yi-Hung Liu Wei-Ting Cheng Chen-Yu Yeh Chi-How Peng 《Journal of polymer science. Part A, Polymer chemistry》2020,58(1):101-113
A series of cobalt(II) phenoxy-imine complexes (CoII(FI)2) have been synthesized to mediate the radical polymerization of vinyl acetate (VAc) and methyl acrylate (MA) to evaluate the influence of chelating atoms and configuration to the control of polymerization. The VAc polymerizations showed the properties of controlled/living radical polymerization (C/LRP) with complexes 1a and 3a , but the catalytic chain transfer (CCT) behaviors with complexes 2a , 1b , 2b , and 3b . The control of VAc polymerization mediated by complex 1a could be improved by decreasing the reaction temperature to approach the molecular weights that not only linearly increased with conversions but also matched the theoretical values and relatively narrow molecular weight distributions. The catalytic chain transfer polymerizations (CCTP) mediated by complexes 2a , 1b , 2b , and 3b were characterized by Mayo plots and the polymer chain end double bonds were observed by 1H NMR spectra. The tendency toward C/LRP or CCTP in VAc polymerization mediated by CoII(FI)2 could be determined by the ligand structure. Cobalt complex coordinated by the ligand with more steric hindered and less electron-donating substituents favored the controlled/living radical polymerization. In contrast, the efficiency of CCT process could be enhanced by less steric hindered, more electron-donating ligands. The controlled/living radical polymerization of MA, however, could not be achieved by the mediation of these cobalt(II) phenoxy-imine complexes. Associated with the results of polymerization mediated by other cobalt complexes, this study implied that the configuration and spin state of cobalt complexes were more critical than the chelating atoms to the control behavior of radical polymerization. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 101–113 相似文献
14.
A monomeric complex [Co(Im)2(O2CMe)2] (1) and a novel aquabridged dimeric complex [Co2(μ‐H2O)(μ‐CMe)2(Im)4‐(O2CMe)2] (2) (Im = imidazole) have been synthesized and characterized. Complexes 1 and 2 coexisted in solution. Pure forms of either complex can be obtained from the same solution by controlling the crystallization conditions. All two complexes possess a carboxylate‐Im‐cobalt(II) triad system analogous to the carboxylate‐histidine‐metal triad systems that have been found in many zinc enzymes and cobalt(II)‐substituted enzymes. In 2, two Co2+ ions are connected by a water molecule in a bridging fashion with Co°Co [0.3687(1) nm], Co—OH2 [0.2159(3) nm], and Co‐OH2‐Co [117.2(3)°], in which the water molecule is further stabilized by two intramolecular hydrogen bonds with the oxygens of the terminal monodentate acetate groups with the distance of O…0 [0.2609(7) nm]. The terminal monodentate acetate groups display quite abnormal geometry due to the strong “pulling effect” on the carboxylates by intermolecular and intramolecular hydrogen bonds. Complex 2 showed weak antiferromagnetic coupling at low temperature with g = 2.22 and J = ?1.60 cm?1. 相似文献
15.
《中国化学会会志》2017,64(7):833-842
In the present work, the cobalt(II ) synergist complex with isobutyric acid (HLI ) and 5‐hydroxy‐4‐octanone oxime (HBI ), which were the corresponding short‐chain analogs of active synergistic mixture of Versatic10 (HL ) and Lix63 (5,8‐diethyl‐7‐hydroxy‐6‐dodecanoneoxime, HB ), was prepared and studied by X‐ray single‐crystal diffraction. The crystal structure of the cobalt(II ) synergistic complex showed that the composition of the complex was Co(HBI )2(LI )2 with a cis‐form octahedron geometry structure. Both intra and intermolecular hydrogen bonding between the uncoordinated carbonyl oxygen atom of the deprotonated monodentate anionic ligand LI and the hydrogen atom of the α‐hydroxy or the oxime hydroxyl group of HBI were observed in the crystal lattice. In order to bridge the gap between the solid‐state structure of the cobalt(II ) synergist complex and the solution structure of the extracted cobalt(II ) complex with the actual synergistic mixture containing Versatic10 and Lix63 in the nonpolar organic phase, both the cobalt(II ) synergistic complex and the extracted cobalt(II ) complex were further investigated by Fourier transform infrared spectroscopy (FT‐IR ) and electrospray ionization mass spectrometry (ESI‐MS ). The results indicated that the extracted cobalt(II ) complex in the nonpolar organic phase might possess a similar coordination structure as that of the cobalt(II ) synergist complex. 相似文献
16.
Daisuke Takeuchi Yoshihiko Sakaguchi Kohtaro Osakada 《Journal of polymer science. Part A, Polymer chemistry》2002,40(24):4530-4537
Co2(CO)8 catalyzes the ring‐opening copolymerization of propylene oxide with CO to afford the polyester in the presence of various amine cocatalysts. The 1H and 13C{1H} NMR spectra of the polyester, obtained by the Co2(CO)8–3‐hydroxypyridine catalyst, show the following structure ? [CH2? CH(CH3)? O? CO]n? . The Co2(CO)8–phenol catalyst gives the polyester, which contains the partial structural unit formed through the ring‐opening copolymerization of tetrahydrofuran with CO. The bidentate amines, such as bipyridine and N,N,N′,N′‐tetramethylethylenediamine, enhance the Co complex‐catalyzed copolymerization, which produces the polyester with a regulated structure. Acylcobalt complexes, (RCO)Co(CO)n (R = Me or CH2Ph), prepared in situ, do not catalyze the copolymerization even in the presence of pyridine. This suggests that the chain growth involves the intermolecular nucleophilic addition of the OH group of the intermediate complex to the acyl–cobalt bond, forming an ester bond rather than the insertion of propylene oxide into the acyl–cobalt bond. Co2(CO)8? Ru3(CO)12 mixtures also bring about the copolymerization of propylene oxide with CO. The molar ratio of Ru to Co affects the yield, molecular weight, and structure of the produced copolymer. The catalysis is ascribed to the Ru? Co mixed‐metal cluster formed in the reaction mixture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4530–4537, 2002 相似文献
17.
Yao Zhang Jie Li Guoyu Ren Baofu Qin Haixia Ma 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(6):485-490
Azole compounds have attracted commercial interest due to their high bactericidal and plant‐growth‐regulating activities. Uniconazole [or 1‐(4‐chlorophenyl)‐4,4‐dimethyl‐2‐(1H‐1,2,4‐triazol‐1‐yl)pent‐1‐en‐3‐ol] is a highly active 1,2,4‐triazole fungicide and plant‐growth regulator with low toxicity. The pharmacological and toxicological properties of many drugs are modified by the formation of their metal complexes. Therefore, there is much interest in exploiting the coordination chemistry of triazole pesticides and their potential application in agriculture. However, reports of complexes of uniconazole are rare. A new cobalt(II) complex of uniconazole, namely dichloridotetrakis[1‐(4‐chlorophenyl)‐4,4‐dimethyl‐2‐(1H‐1,2,4‐triazol‐1‐yl‐κN4)pent‐1‐en‐3‐ol]cobalt(II), [CoCl2(C15H18ClN3O)4], was synthesized and structurally characterized by element analysis, IR spectrometry and X‐ray single‐crystal diffraction. The crystal structural analysis shows that the CoII atom is located on the inversion centre and is coordinated by four uniconazole and two chloride ligands, forming a distorted octahedral geometry. The hydroxy groups of an uniconazole ligands of adjacent molecules form hydrogen bonds with the axial chloride ligands, resulting in one‐dimensional chains parallel to the a axis. The complex was analysed for its antifungal activity by the mycelial growth rate method. It was revealed that the antifungal effect of the title complex is more pronounced than the effect of fungicide uniconazole for Botryosphaeria ribis, Wheat gibberellic and Grape anthracnose. 相似文献
18.
Dr. Kartik Chandra Mondal Dr. Sudipta Roy Dr. Susmita De Dr. Pattiyil Parameswaran Dr. Birger Dittrich Dr. Fabian Ehret Prof. Dr. Wolfgang Kaim Prof. Dr. Herbert W. Roesky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(37):11646-11649
Compound (Me2‐cAAC:)2Co0 ( 2 ; Me2‐cAAC:=cyclic (alkyl) amino carbene; :C(CH2)(CMe2)2N‐2,6‐iPr2C6H3) was synthesized by the reduction of the precursor (Me2‐cAAC:)2CoICl ( 1 ) with KC8 in THF. The cyclic voltammogram of 1 exhibited one‐electron reduction, which suggests that synthesis of a bent 2‐metallaallene ( 2 ) from 1 should be possible. Compound 2 contains one cobalt atom in the formal oxidation state zero, which is stabilized by two Me2‐cAAC: ligands. Bond lengths from X‐ray diffraction are 1.871(2) and 1.877(2) Å with a C‐Co‐C bond angle of 170.12(8)°. The EPR spectrum of 2 exhibited a broad resonance attributed to the unique quasi‐linear structure, which favors near degeneracy and gives rise to very rapid relaxation conditions. The cAAC?Co bond in 2 can be considered as a typical Dewar–Chatt–Duncanson type of bonding, which in turn retains 2.5 electron pairs on the Co atom as nonbonding electrons. 相似文献
19.
Dihydrogen Catalysis of the Reversible Formation and Cleavage of CH and NH Bonds of Aminopyridinate Ligands Bound to (η5‐C5Me5)IrIII
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Dr. Ana Zamorano Dr. Nuria Rendón Dr. Joaquín López‐Serrano Dr. José E. V. Valpuesta Dr. Eleuterio Álvarez Prof. Dr. Ernesto Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2576-2587
This study focuses on a series of cationic complexes of iridium that contain aminopyridinate (Ap) ligands bound to an (η5‐C5Me5)IrIII fragment. The new complexes have the chemical composition [Ir(Ap)(η5‐C5Me5)]+, exist in the form of two isomers ( 1+ and 2+ ) and were isolated as salts of the BArF? anion (BArF=B[3,5‐(CF3)2C6H3]4). Four Ap ligands that differ in the nature of their bulky aryl substituents at the amido nitrogen atom and pyridinic ring were employed. In the presence of H2, the electrophilicity of the IrIII centre of these complexes allows for a reversible prototropic rearrangement that changes the nature and coordination mode of the aminopyridinate ligand between the well‐known κ2‐N,N′‐bidentate binding in 1+ and the unprecedented κ‐N,η3‐pseudo‐allyl‐coordination mode in isomers 2+ through activation of a benzylic C?H bond and formal proton transfer to the amido nitrogen atom. Experimental and computational studies evidence that the overall rearrangement, which entails reversible formation and cleavage of H?H, C?H and N?H bonds, is catalysed by dihydrogen under homogeneous conditions. 相似文献
20.
Microtubing‐Reactor‐Assisted Aliphatic C−H Functionalization with HCl as a Hydrogen‐Atom‐Transfer Catalyst Precursor in Conjunction with an Organic Photoredox Catalyst
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Dr. Hong‐Ping Deng Quan Zhou Dr. Jie Wu 《Angewandte Chemie (International ed. in English)》2018,57(39):12661-12665
Chlorine radical, which is classically generated by the homolysis of Cl2 under UV irradiation, can abstract a hydrogen atom from an unactivated C(sp3)?H bond. We herein demonstrate the use of HCl as an effective hydrogen‐atom‐transfer catalyst precursor activated by an organic acridinium photoredox catalyst under visible‐light irradiation for C?H alkylation and allylation. The key to success relied on the utilization of microtubing reactors to maintain the volatile HCl catalyst. This photomediated chlorine‐based C?H activation protocol is effective for a variety of unactivated C(sp3)?H bond patterns, even with primary C(sp3)?H bonds, as in ethane. The merit of this strategy is illustrated by rapid access to several pharmaceutical drugs from abundant unfunctionalized alkane feedstocks. 相似文献