共查询到20条相似文献,搜索用时 46 毫秒
1.
Electrocatalytic Dihydrogen Production with a Robust Mesoionic Pyridylcarbene Cobalt Catalyst 下载免费PDF全文
Margarethe van der Meer Estelle Glais Dr. Inke Siewert Prof. Dr. Biprajit Sarkar 《Angewandte Chemie (International ed. in English)》2015,54(46):13792-13795
A CoIII complex with a mesoionic pyridylcarbene ligand is presented. This complex is an efficient electrocatalyst for H2 production at very low overpotential and high turnovers when using a (glassy carbon) GC electrode. The corresponding triazole complexes display no catalytic activity whatsoever under identical conditions. The remarkable robustness of the Co? C(carbene) bond towards acids is likely responsible for the high efficiency of this catalyst. The present results thus open new avenues for carbene‐based ligands for generating functional models for hydrogenases. 相似文献
2.
Olefin Cyclopropanation by Radical Carbene Transfer Reactions Promoted by Cobalt(II)/Porphyrinates: Active‐Metal‐Template Synthesis of [2]Rotaxanes 下载免费PDF全文
Arthur F. P. Alcântara Liniquer A. Fontana Vitor H. Rigolin Yuri F. S. Andrade Dr. Marcos A. Ribeiro Prof. Wdeson P. Barros Prof. Catia Ornelas Prof. Jackson D. Megiatto Jr. 《Angewandte Chemie (International ed. in English)》2018,57(29):8979-8983
A CoII/porphyrinate‐based macrocycle in the presence of a 3,5‐diphenylpyridine axial ligand functions as an endotopic ligand to direct the assembly of [2]rotaxanes from diazo and styrene half‐threads, by radical‐carbene‐transfer reactions, in excellent 95 % yield. The method reported herein applies the active‐metal‐template strategy to include radical‐type activation of ligands by the metal‐template ion during the organometallic process which ultimately yields the mechanical bond. A careful quantitative analysis of the product distribution afforded from the rotaxane self‐assembly reaction shows that the CoII/porphyrinate subunit is still active after formation of the mechanical bond and, upon coordination of an additional diazo half‐thread derivative, promotes a novel intercomponent C?H insertion reaction to yield a new rotaxane‐like species. This unexpected intercomponent C?H insertion illustrates the distinct reactivity brought to the CoII/porphyrinate catalyst by the mechanical bond. 相似文献
3.
Rivada-Wheelaghan O Ortuño MA Díez J Lledós A Conejero S 《Angewandte Chemie (International ed. in English)》2012,51(16):3936-3939
Small change matters: T-shaped Pt(II) complexes with less flexible substituents, than, for example, isopropyl or tert-butyl groups, on N-heterocyclic carbene (NHC) ligands allow for C-H bond activation reactions of aromatic compounds (see scheme; BAr(f)(4)(-) =tetrakis[(3,5-trifluoromethyl)phenyl]borate; F yellow, Pt red). NHC substituents that are not highly branched prevent agostic interactions and reduce the barriers to achieve the C-H bond cleavage. 相似文献
4.
Chase A. Salazar Joseph J. Gair Kaylin N. Flesch Ilia A. Guzei Jared C. Lewis Shannon S. Stahl 《Angewandte Chemie (International ed. in English)》2020,59(27):10873-10877
Mono‐N‐protected amino acids (MPAAs) are increasingly common ligands in Pd‐catalyzed C?H functionalization reactions. Previous studies have shown how these ligands accelerate catalytic turnover by facilitating the C?H activation step. Here, it is shown that MPAA ligands exhibit a second property commonly associated with ligand‐accelerated catalysis: the ability to support catalytic turnover at substoichiometric ligand‐to‐metal ratios. This catalytic role of the MPAA ligand is characterized in stoichiometric C?H activation and catalytic C?H functionalization reactions. Palladacycle formation with substrates bearing carboxylate and pyridine directing groups exhibit a 50–100‐fold increase in rate when only 0.05 equivalents of MPAA are present relative to PdII. These and other mechanistic data indicate that facile exchange between MPAAs and anionic ligands coordinated to PdII enables a single MPAA to support C?H activation at multiple PdII centers. 相似文献
5.
Jason Vachon Steen Brian Schougaard 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(10):m382-m384
The title compound, [Ni(C8H12BN4)(C13H18BN6)] or Bp′Tp′NiII, where Bp′ is (3,5‐dimethylpyrazol‐1‐yl)dihydro(pyrazol‐1‐yl)borate and Tp′ is bis(3,5‐dimethylpyrazol‐1‐yl)hydro(pyrazol‐1‐yl)borate, contains a divalent NiII centre bound by the chelating N atoms of the polysubstituted pyrazolylborate ligands. It is shown to lack a strong agostic B—H...Ni interaction, implying that the sixth coordination site is unoccupied in the solid state. This square‐pyramidal complex is the only known crystal structure where the NiII centre is pentacoordinated while bonded exclusively to pyrazolyl units. This is of interest with respect to electrochemical and catalytic properties. 相似文献
6.
F. Mark Chadwick Basile F. E. Curchod Rosario Scopelliti Farzaneh FadaeiTirani Euro Solari Kay Severin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(6):1778-1781
Azoimidazolium dyes were used as precursors for mesoionic carbene ligands (Azo‐MICs). The properties of these ligands were examined by synthesizing RhI, AuI, and PdII complexes. Experimental (NMR, IR) and theoretical investigations show that Azo‐MICs are potent σ‐donor ligands. Yet, they feature a small singlet–triplet gap and very low‐lying LUMO levels. The unique electronic properties of Azo‐MICs allow for reversible one‐electron reductions of the metal complexes, as evidenced by cyclic voltammetry. 相似文献
7.
Xiu‐Li Wang Nai‐Li Chen Guo‐Cheng Liu Jing‐Jing Huang Jian Luan Yun Qu 《无机化学与普通化学杂志》2014,640(2):476-482
Three coordination compounds with dimensions from 0D to 2D, namely, [Co(bppdca)2(HL1)2] ( 1 ) [Co(bppdca)(L2)(H2O)] · 2H2O ( 2 ) and [Co(bppdca)(L3)] · 3H2O ( 3 ) [bppdca = N,N′‐bis(pyridine‐3‐yl)pyridine‐2,6‐dicarboxamide, H2L1 = 2,5‐pyridinedicarboxylic acid, H2L2 = 4,4′‐oxybisbenzoic acid, H2L3 = 2‐carboxymethylsulfanyl nicotinic acid] were hydrothermally synthesized and structurally characterized. Single crystal X‐ray diffraction analysis reveals that complex 1 is a discrete 0D complex, in which the bppdca ligand and the H2L1 act as the terminal groups to coordinate with the CoII ions. In coordination polymer 2 , two bppdca ligands coordinate in anti configuration with two CoII ions to generate a 28‐membered Co2(bppdca)2 loop, which is further extended into 1D ladder‐like double chain by pairs of L2 ligands. In 3 , the CoII ions are linked by bppdca ligands to generate 1D wave‐like chain, which is further connected by the L3 to form a 2D network. Finally, the coordination compounds 1 – 3 are extended into 3D supramolecular frameworks through the hydrogen bonding interactions. The CoII ions and the bppdca ligands in the title coordination compounds exhibit different coordination characters and conformations. The effect of organic dicarboxylates with different rigidity and length on the structures of CoII coordination compounds was investigated. In addition, the fluorescence and electrochemical behaviors of coordination compounds 1 – 3 were reported. 相似文献
8.
Ligand Transformations and Efficient Proton/Water Reduction with Cobalt Catalysts Based on Pentadentate Pyridine‐Rich Environments 下载免费PDF全文
Debashis Basu Dr. Shivnath Mazumder Xuetao Shi Habib Baydoun Dr. Jens Niklas Dr. Oleg Poluektov Prof. H. Bernhard Schlegel Prof. Cláudio N. Verani 《Angewandte Chemie (International ed. in English)》2015,54(7):2105-2110
A series of cobalt complexes with pentadentate pyridine‐rich ligands is studied. An initial CoII amine complex 1 is prone to aerial oxidation yielding a CoIII imine complex 2 that is further converted into an amide complex 4 in presence of adventitious water. Introduction of an N‐methyl protecting group to the ligand inhibits this oxidation and gives rise to the CoII species 5 . Both the CoIII 4 and CoII 5 show electrocatalytic H2 generation in weakly acidic media as well as in water. Mechanisms of catalysis seem to involve the protonation of a CoII? H species generated in situ. 相似文献
9.
Xuechao Yan Haiying Wang Shuai Guo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(47):17063-17067
The study of palladium(IV) species has great implications for PdII/PdIV‐mediated catalysis. However, most of the PdIV complexes rapidly decompose under ambient conditions, which makes the isolation, characterization and further reactivity study very challenging. The reported ancillary ligand platforms to stabilize PdIV species are dominated by chelating N‐donors such as bipyridines. In this work, we present two PdIV complexes with scarcely used C‐donors as the supporting platform. The anionic aryl donor and MIC (MIC=mesoionic carbene) are combined in a [CC′C]‐type pincer framework to access a series of ambient‐stable PdIV tris(halido) complexes. Their synthesis, solid‐state structures, stability, and reactivity are presented. To the best of our knowledge, the work presented herein reports the first isolated PdIV–MIC as well as the first PdIV carbene‐based aryl pincer. 相似文献
10.
Oxidation State Dependent Coordination Modes: Accessing an Amidate‐Supported Nickel(I) δ‐bis(C−H) Agostic Complex 下载免费PDF全文
D. Dawson Beattie Eric G. Bowes Marcus W. Drover Prof. Dr. Jennifer A. Love Prof. Dr. Laurel L. Schafer 《Angewandte Chemie (International ed. in English)》2016,55(42):13290-13295
Amidate‐supported two‐ and three‐coordinate NiI complexes were synthesized by reduction of the corresponding NiII precursors. A dramatic change in binding mode is observed upon reduction from NiII to NiI. The NiI derivatives include an unprecedented NiI bis(C?H) agostic complex and a two‐coordinate NiI complex. 相似文献
11.
Redox‐Induced Spin‐State Switching and Mixed Valency in Quinonoid‐Bridged Dicobalt Complexes 下载免费PDF全文
David Schweinfurth Yvonne Rechkemmer Stephan Hohloch Naina Deibel Irina Peremykin Jan Fiedler Raphael Marx Dr. Petr Neugebauer Prof. Dr. Joris van Slageren Prof. Dr. Biprajit Sarkar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(12):3475-3486
The complexes [{(tmpa)CoII}2(μ‐L1)2?]2+ ( 12+ ) and [{(tmpa)CoII}2(μ‐L2)2?]2+ ( 22+ ), with tmpa=tris(2‐pyridylmethyl)amine, H2L1=2,5‐di‐[2‐(methoxy)‐anilino]‐1,4‐benzoquinone, and H2L2=2,5‐di‐[2‐(trifluoromethyl)‐anilino]‐1,4‐benzoquinone, were synthesized and characterized. Structural analysis of 22+ revealed a distorted octahedral coordination around the cobalt centers, and cobalt–ligand bond lengths that match with high‐spin CoII centers. Superconducting quantum interference device (SQUID) magnetometric studies on 12+ and 22+ are consistent with the presence of two weakly exchange‐coupled high‐spin cobalt(II) ions, for which the nature of the coupling appears to depend on the substituents on the bridging ligand, being antiferromagnetic for 12+ and ferromagnetic for 22+ . Both complexes exhibit several one‐electron redox steps, and these were investigated with cyclic voltammetry and UV/Vis/near‐IR spectroelectrochemistry. For 12+ , it was possible to chemically isolate the pure forms of both the one‐electron oxidized mixed‐valent 13+ and the two‐electron oxidized isovalent 14+ forms, and characterize them structurally as well as magnetically. This series thus provided an opportunity to investigate the effect of reversible electron transfers on the total spin‐state of the molecule. In contrast to 22+ , for 14+ the metal–ligand distances and the distances within the quinonoid ligand point to the existence of two low‐spin CoIII centers, thus showing the innocence of the quintessential non‐innocent ligands L. Magnetic data corroborate these observations by showing the decrease of the magnetic moment by roughly half (neglecting spin exchange effects) on oxidizing the molecules with one electron, and the disappearance of a paramagnetic response upon two‐electron oxidation, which confirms the change in spin state associated with the electron‐transfer steps. 相似文献
12.
RuII,OsII, and IrIII Complexes with Chelating Pyridyl–Mesoionic Carbene Ligands: Structural Characterization and Applications in Transfer Hydrogenation Catalysis 下载免费PDF全文
Aljoša Bolje Dr. Stephan Hohloch Margarethe van der Meer Janez Košmrlj Prof. Dr. Biprajit Sarkar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(18):6756-6764
Chelating ligands with one pyridine donor and one mesoionic carbene donor are fast establishing themselves as privileged ligands in homogeneous catalysis. The synthesis of several new IrIII–Cp*‐ and OsII–Cym complexes (Cp*=pentamethylcyclopentadienyl, Cym=p‐cymene=4‐isopropyl‐toluene) derived from chelating pyridyltriazolylidenes where the additional pyridine donor was incorporated via the azide part of the triazole is presented. Furthermore, different 4‐substituted phenylacetylene building blocks have been used to introduce electronic fine‐tuning in the ligands. The ligands thus can be generally described as 4‐(4‐R‐phenyl)‐3‐methyl‐1‐(pyridin‐2‐yl)‐1H‐1,2,3‐triazol‐5‐ylidene (with R being H (L1), Me (L2), OMe (L3), CN (L4), CF3 (L5), Br (L6) or NO2 (L7)). The corresponding complexes (Ir‐ 1 to Ir‐ 7 and Os‐ 1 to Os‐ 7 ) were characterized by standard spectroscopic methods, and the expected three‐legged, piano‐stool type coordination was unambiguously confirmed by X‐ray diffraction analysis of selected compounds. Together with RuII analogues previously reported by us, a total of 21 complexes were tested as (pre)catalysts for the transfer hydrogenation of carbonyl groups, showing a remarkable reactivity even at very low catalyst loadings. The electronic effects of the ligands as well as different substrates were investigated. Some mechanistic elucidations are also presented. 相似文献
13.
Mihaela‐Diana Şerb Manfred Speldrich Prof. Dr. Heiko Lueken Prof. Dr. Ulli Englert 《无机化学与普通化学杂志》2011,637(5):536-542
The crystal structures of two new isomorphous transition metal squarato complexes [MII(C4O4)(dmso)2(OH2)2] [MII = CoII (3d7), MnII (3d5); dmso = dimethylsulfoxide] and their magnetic properties are reported. The compounds feature two symmetrically independent chains, in which 1,3‐bridging squarato ligands connect cations in distorted octahedral surroundings of pseudo‐symmetry D4h. From an equimolar solution of CoCl2 · 6H2O and MnCl2 · 2H2O a mixed‐metal coordination polymer crystallizes; it represents a solid solution and adopts the same structure as the corresponding monometallic compounds. The results of the diffraction experiment unambiguously proof the presence of both CoII and MnII cations in either independent site albeit no precise ratio between the metal cations involved may be deduced from these findings. The difference in the magnetic properties between CoII and MnII cations in the given ligand field has allowed us to establish their ratio in the solid solution more reliably than by X‐ray diffraction: Accounting for ligand field potential and spin‐orbit coupling of CoII and regarding MnII as a pure spin system, the calculations yielded a fraction of 73 % CoII in the mixed‐metal polymer. With respect to superexchange effects only weak antiferromagnetic interactions have been detected for the three coordination polymers. 相似文献
14.
Aniket Chowdhury Prodip Howlader Prof. Dr. Partha Sarathi Mukherjee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1424-1434
A new triphenylamine‐based organometallic PtII luminogen ( 1 ) and its analogous organic compound ( 2 ) are reported. The molecules are decorated with aldehyde functionality to improve their photophysical properties by utilising donor–acceptor interactions. The single crystal X‐ray structure analysis of PtII analogue 1 revealed that the neighbouring molecules were loosely organised by weak intermolecular C?H???π interactions. Because of the twisted nature of the triphenylamine backbone the compounds showed aggregation‐induced emission enhancement in THF/water mixture. Due to their loose crystal packing, upon application of external stimuli these luminogens exhibited mechano‐fluorochromic behaviour. The crystalline forms of the compounds displayed a more superior emission efficiency than the grinded samples. Moreover, the compounds showed crystallization‐induced emission enhancement (CIEE) and exhibited chemodosimetric response towards cysteine under physiological condition. 相似文献
15.
A Cobalt(I) Pincer Complex with an η2‐Caryl−H Agostic Bond: Facile C−H Bond Cleavage through Deprotonation,Radical Abstraction,and Oxidative Addition 下载免费PDF全文
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
16.
Dr. Graham N. Newton Dr. Kiyotaka Mitsumoto Rong‐Jia Wei Fumichika Iijima Dr. Takuya Shiga Prof. Dr. Hiroyuki Nishikawa Prof. Dr. Hiroki Oshio 《Angewandte Chemie (International ed. in English)》2014,53(11):2941-2944
A bulky bidentate ligand was used to stabilize a macrocyclic [FeIII8CoII6] cluster. Tuning the basicity of the ligand by derivatization with one or two methoxy groups led to the isolation of a homologous [FeIII8CoII6] species and a [FeIII6FeII2CoIII2CoII2] complex, respectively. Lowering the reaction temperatures allowed isolation of [FeIII6FeII2CoIII2CoII2] clusters with all three ligands. Temperature‐dependent absorption data and corresponding experiments with iron/nickel systems indicated that the iron/cobalt self‐assembly process was directed by the occurrence of solution‐state electron‐transfer‐coupled spin transition (ETCST) and its influence on reaction intermediate lability. 相似文献
17.
Strong Direct Magnetic Coupling in a Dinuclear CoII Tetrazine Radical Single‐Molecule Magnet 下载免费PDF全文
Toby J. Woods Dr. Maria Fernanda Ballesteros‐Rivas Sergei M. Ostrovsky Andrew V. Palii Oleg S. Reu Sophia I. Klokishner Dr. Kim R. Dunbar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(29):10302-10305
The ligand‐centered radical complex [(CoTPMA)2‐μ‐bmtz.?](O3SCF3)3 ? CH3CN (bmtz=3,6‐bis(2′‐pyrimidyl)‐1,2,4,5‐tetrazine, TPMA=tris‐(2‐pyridylmethyl)amine) has been synthesized from the neutral bmtz precursor. Single‐crystal X‐ray diffraction studies have confirmed the presence of the ligand‐centered radical. The CoII complex exhibits slow paramagnetic relaxation in an applied DC field with a barrier to spin reversal of 39 K. This behavior is a result of strong antiferromagnetic metal–radical coupling combined with positive axial and strong rhombic anisotropic contributions from the CoII ions. 相似文献
18.
《化学:亚洲杂志》2017,12(1):145-158
Two classes of cationic palladium(II) acetylide complexes containing pincer‐type ligands, 2,2′:6′,2′′‐terpyridine (terpy) and 2,6‐bis(1‐butylimidazol‐2‐ylidenyl)pyridine (C^N^C), were prepared and structurally characterized. Replacing terpy with the strongly σ‐donating C^N^C ligand with two N‐heterocyclic carbene (NHC) units results in the PdII acetylide complexes displaying phosphorescence at room temperature and stronger intermolecular interactions in the solid state. X‐ray crystal structures of [Pd(terpy)(C≡CPh)]PF6 ( 1 ) and [Pd(C^N^C)(C≡CPh)]PF6 ( 7 ) reveal that the complex cations are arranged in a one‐dimensional stacking structure with pair‐like PdII⋅⋅⋅PdII contacts of 3.349 Å for 1 and 3.292 Å for 7 . Density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) calculations were used to examine the electronic properties. Comparative studies of the [Pt(L)(C≡CPh)]+ analogs by 1H NMR spectroscopy shed insight on the intermolecular interactions of these PdII acetylide complexes. The strong Pd−Ccarbene bonds render 7 and its derivative sufficiently stable for investigation of photo‐cytotoxicity under cellular conditions. 相似文献
19.
Barbara Modec 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(4):340-343
Single crystals of a triclinic polymorphic form of mer‐μ‐oxalato‐bis[chloridotripyridinecobalt(II)] pyridine disolvate, [Co2(C2O4)Cl2(C5H5N)6]·2C5H5N, have been prepared by solvothermal methods. The structure and geometric parameters strongly resemble those of the previously reported monoclinic polymorph [Bolte (2006). Acta Cryst. E 62 , m597–m598]. In both polymorphic forms, the dinuclear complex molecules are located on a crystallographic centre of inversion, with the CoII cations in a distorted octahedral environment consisting of a chloride ligand, three pyridine ligands and a chelating bis‐bidentate oxalate ligand. This last serves as a bridging ligand between two CoII cations. The polymorphs differ in the mutual orientation of their pyridine ligands in the dinuclear molecules and in their intermolecular connectivity. In the triclinic polymorph, C—H...O, C—H...Cl, C—H...π and π–π interactions link the dinuclear molecules into a three‐dimensional structure. Pyridine solvent molecules are attached to this structure via weak interactions. 相似文献
20.
Heterometallic Fe2II–UV and Ni2II–UV Exchange‐Coupled Single‐Molecule Magnets: Effect of the 3 d Ion on the Magnetic Properties 下载免费PDF全文
Lucile Chatelain Dr. Jacques Pécaut Dr. Floriana Tuna Dr. Marinella Mazzanti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18038-18042
Uranium‐based compounds have been put forward as ideal candidates for the design of single‐molecule magnets (SMMs) with improved properties, but to date, only two examples of exchange‐coupled 3d–5f SMM containing uranium have been reported and both are based on the MnII ion. Here we have synthesized the first examples of exchange‐coupled uranium SMMs based on FeII and NiII. The SMM behavior of these complexes containing a quasi linear {M?O?U?O?M} core arises from intramolecular Fe?U and Ni?U exchange interactions combined with the high Ising anisotropy of the uranyl(V) moiety. The measured values of the relaxation barrier (53.9±0.9 K in the UFe2 complex and of 27.4±0.5 K in the UNi2 complex) show clearly the dependency on the spin value of the transition metal, providing important new information for the future design of improved uranium‐based SMMs. 相似文献