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1.
A Heteroleptic Ferrous Complex with Mesoionic Bis(1,2,3‐triazol‐5‐ylidene) Ligands: Taming the MLCT Excited State of Iron(II) 下载免费PDF全文
Dr. Yizhu Liu Dr. Kasper S. Kjær Dr. Lisa A. Fredin Dr. Pavel Chábera Tobias Harlang Dr. Sophie E. Canton Prof. Sven Lidin Dr. Jianxin Zhang Prof. Reiner Lomoth Dr. Karl‐Erik Bergquist Prof. Petter Persson Prof. Kenneth Wärnmark Prof. Villy Sundström 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(9):3628-3639
Strongly σ‐donating N‐heterocyclic carbenes (NHCs) have revived research interest in the catalytic chemistry of iron, and are now also starting to bring the photochemistry and photophysics of this abundant element into a new era. In this work, a heteroleptic FeII complex ( 1 ) was synthesized based on sequentially furnishing the FeII center with the benchmark 2,2′‐bipyridine (bpy) ligand and the more strongly σ‐donating mesoionic ligand, 4,4′‐bis(1,2,3‐triazol‐5‐ylidene) (btz). Complex 1 was comprehensively characterized by electrochemistry, static and ultrafast spectroscopy, and quantum chemical calculations and compared to [Fe(bpy)3](PF6)2 and (TBA)2[Fe(bpy)(CN)4]. Heteroleptic complex 1 extends the absorption spectrum towards longer wavelengths compared to a previously synthesized homoleptic FeII NHC complex. The combination of the mesoionic nature of btz and the heteroleptic structure effectively destabilizes the metal‐centered (MC) states relative to the triplet metal‐to‐ligand charge transfer (3MLCT) state in 1 , rendering it a lifetime of 13 ps, the longest to date of a photochemically stable FeII complex. Deactivation of the 3MLCT state is proposed to proceed via the 3MC state that strongly couples with the singlet ground state. 相似文献
2.
A Heteroleptic Push–Pull Substituted Iron(II) Bis(tridentate) Complex with Low‐Energy Charge‐Transfer States 下载免费PDF全文
Andreas K. C. Mengel Dr. Christoph Förster Dr. Aaron Breivogel Katharina Mack Julian R. Ochsmann Dr. Frédéric Laquai Dr. Vadim Ksenofontov Prof. Dr. Katja Heinze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):704-714
A heteroleptic iron(II) complex [Fe(dcpp)(ddpd)]2+ with a strongly electron‐withdrawing ligand (dcpp, 2,6‐bis(2‐carboxypyridyl)pyridine) and a strongly electron‐donating tridentate tripyridine ligand (ddpd, N,N′‐dimethyl‐N,N′‐dipyridine‐2‐yl‐pyridine‐2,6‐diamine) is reported. Both ligands form six‐membered chelate rings with the iron center, inducing a strong ligand field. This results in a high‐energy, high‐spin state (5T2, (t2g)4(eg*)2) and a low‐spin ground state (1A1, (t2g)6(eg*)0). The intermediate triplet spin state (3T1, (t2g)5(eg*)1) is suggested to be between these states on the basis of the rapid dynamics after photoexcitation. The low‐energy π* orbitals of dcpp allow low‐energy MLCT absorption plus additional low‐energy LL′CT absorptions from ddpd to dcpp. The directional charge‐transfer character is probed by electrochemical and optical analyses, Mößbauer spectroscopy, and EPR spectroscopy of the adjacent redox states [Fe(dcpp)(ddpd)]3+ and [Fe(dcpp)(ddpd)]+, augmented by density functional calculations. The combined effect of push–pull substitution and the strong ligand field paves the way for long‐lived charge‐transfer states in iron(II) complexes. 相似文献
3.
Cover Picture: Coordination Chemistry of N‐Heterocyclic Nitrenium‐Based Ligands (Chem. Eur. J. 19/2015) 下载免费PDF全文
Dr. Yuri Tulchinsky Dr. Sebastian Kozuch Dr. Prasenjit Saha Assaf Mauda Dr. Gennady Nisnevich Dr. Mark Botoshansky Dr. Linda J. W. Shimon Prof. Mark Gandelman 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):6965-6965
4.
Back Cover: Di‐ and Trinuclear Gold Complexes of Diphenylphosphinoethyl‐Functionalised Imidazolium Salts and their N‐Heterocyclic Carbenes: Synthesis and Photophysical Properties (Chem. Eur. J. 2/2015) 下载免费PDF全文
Sebastian Bestgen Dr. Michael T. Gamer Dr. Sergei Lebedkin Prof. Dr. Manfred M. Kappes Prof. Dr. Peter W. Roesky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):916-916
5.
Elevated Catalytic Activity of Ruthenium(II)–Porphyrin‐Catalyzed Carbene/Nitrene Transfer and Insertion Reactions with N‐Heterocyclic Carbene Ligands 下载免费PDF全文
Ka‐Ho Chan Dr. Xiangguo Guan Dr. Vanessa Kar‐Yan Lo Prof. Dr. Chi‐Ming Che 《Angewandte Chemie (International ed. in English)》2014,53(11):2982-2987
Bis(NHC)ruthenium(II)–porphyrin complexes were designed, synthesized, and characterized. Owing to the strong donor strength of axial NHC ligands in stabilizing the trans M?CRR′/M?NR moiety, these complexes showed unprecedently high catalytic activity towards alkene cyclopropanation, carbene C? H, N? H, S? H, and O? H insertion, alkene aziridination, and nitrene C? H insertion with turnover frequencies up to 1950 min?1. The use of chiral [Ru(D4‐Por)(BIMe)2] ( 1 g ) as a catalyst led to highly enantioselective carbene/nitrene transfer and insertion reactions with up to 98 % ee. Carbene modification of the N terminus of peptides at 37 °C was possible. DFT calculations revealed that the trans axial NHC ligand facilitates the decomposition of diazo compounds by stabilizing the metal–carbene reaction intermediate. 相似文献
6.
Inside Back Cover: RuII,OsII, and IrIII Complexes with Chelating Pyridyl–Mesoionic Carbene Ligands: Structural Characterization and Applications in Transfer Hydrogenation Catalysis (Chem. Eur. J. 18/2015) 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):6963-6963
7.
Reactions of the oxorhenium(V) complexes [ReOX3(PPh3)2] (X = Cl, Br) with the N‐heterocyclic carbene (NHC) 1,3,4‐triphenyl‐1,2,4‐triazol‐5‐ylidene (LPh) under mild conditions and in the presence of MeOH or water give [ReOX2(Y)(PPh3)(LPh)] complexes (X = Cl, Br; Y = OMe, OH). Attempted reactions of the carbene precursor 5‐methoxy‐1,3,4‐triphenyl‐4,5‐dihydro‐1H‐1,2,4‐triazole ( 1 ) with [ReOCl3(PPh3)2] or [NBu4][ReOCl4] in boiling xylene resulted in protonation of the intermediately formed carbene and decomposition products such as [HLPh][ReOCl4(OPPh3)], [HLPh][ReOCl4(OH2)] or [HLPh][ReO4] were isolated. The neutral [ReOX2(Y)(PPh3)(HLPh)] complexes are purple, airstable solids. The bulky NHC ligands coordinate monodentate and in cis‐position to PPh3. The relatively long Re–C bond lengths of approximate 2.1Å indicate metal‐carbon single bonds. 相似文献
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9.
Cover Picture: Catalytic Asymmetric Hydroalkenylation of Vinylarenes: Electronic Effects of Substrates and Chiral N‐Heterocyclic Carbene Ligands (Angew. Chem. Int. Ed. 15/2015) 下载免费PDF全文
Prof. Dr. Chun‐Yu Ho Chun‐Wa Chan Lisi He 《Angewandte Chemie (International ed. in English)》2015,54(15):4403-4403
10.
Inside Cover: Efficient Biomimetic Hydroxylation Catalysis with a Bis(pyrazolyl)imidazolylmethane Copper Peroxide Complex (Chem. Eur. J. 49/2015) 下载免费PDF全文
Dr. Claudia Wilfer Patricia Liebhäuser Dr. Alexander Hoffmann Hannes Erdmann Oleg Grossmann Leander Runtsch Eva Paffenholz Rahel Schepper Regina Dick Prof. Dr. Matthias Bauer Maximilian Dürr Prof. Dr. Ivana Ivanović‐Burmazović Prof. Dr. Sonja Herres‐Pawlis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(49):17522-17522
11.
Dr. María Rodríguez‐Castillo Gustavo Lugo‐Preciado Dr. Danielle Laurencin Dr. Frederik Tielens Dr. Arie van der Lee Dr. Sébastien Clément Dr. Yannick Guari Dr. José M. López‐de‐Luzuriaga Dr. Miguel Monge Dr. Françoise Remacle Dr. Sébastien Richeter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10680-10680
12.
[ReNCl2(PPh3)2] and [ReNCl2(PMe2Ph)3] react with the N‐heterocyclic carbene (NHC) 1,3,4‐triphenyl‐1,2,4‐triazol‐5‐ylidene (HLPh) under formation of the stable rhenium(V) nitrido complex [ReNCl(HLPh)(LPh)], which contains one of the two NHC ligands with an additional orthometallation. The rhenium atom in the product is five‐coordinate with a distorted square‐pyramidal coordination sphere. The position trans to the nitrido ligand is blocked by one phenyl ring of the monodentate HLPh ligand. The Re–C(carbene) bond lengths of 2.072(6) and 2.074(6) Å are comparably long and indicate mainly σ‐bonding between the NHC ligand and the electron deficient d2 metal atom. The chloro ligand in [ReNCl(HLPh)(LPh)] is labile and can be replaced by ligands such as pseudohalides or monoanionic thiolates such as diphenyldithiophosphinate (Ph2PS2?) or pyridine‐2‐thiolate (pyS?). X‐ray structure analyses of [ReN(CN)(HLPh)(LPh)] and [ReN(pyS)(HLPh)(LPh)] show that the bonding situation of the NHC ligands (Re–C(carbene) distances between 2.086(3) and 2.130(3) Å) in the product is not significantly influenced by the ligand exchange. The potentially bidentate pyS? ligand is solely coordinated via its thiolato functionality. Hydrogen atoms of each one of the phenyl rings come close to the unoccupied sixth coordination positions of the rhenium atoms in the solid state structures of all complexes. Re–H distances between 2.620 and 2.712Å do not allow to discuss bonding, but with respect to the strong trans labilising influence of “N3?”, weak interactions are indicated. 相似文献
13.
Inside Back Cover: Univalent Gallium Complexes of Simple and ansa‐Arene Ligands: Effects on the Polymerization of Isobutylene (Chem. Eur. J. 1/2015) 下载免费PDF全文
Martin R. Lichtenthaler Steffen Maurer Robert J. Mangan Florian Stahl Florian Mönkemeyer Julian Hamann Prof. Dr. Ingo Krossing 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):471-471
14.
New hybrid ligands are reported that combine two types of popular donor groups within a single linear scaffold, viz., a central pyrazolate bridge and two appended bis(N‐heterocyclic carbene) units; the ligand strands thus provide two potentially tridentate {NCC} compartments. The pyrazole/tetraimidazolium proligands, [H5L1](PF6)4 and [H5L2](PF6)4 , were synthesized via multi‐step protocols, and the NH prototropy of [H5L1](PF6)4 was examined by variable temperature (VT) NMR spectroscopy, giving solvent dependent activation parameters (ΔH? = 27.6 kJ · mol–1, ΔS? = –125 J · mol–1 · K–1 in [D3]MeCN; ΔH? = 40.4 kJ · mol–1, ΔS? = –86.9 J · mol–1 · K–1 in [D6]DMSO) that are in the range typical for pyrazoles. Reaction of the proligands with Ag2O gave hexametallic complexes [Ag6(L1)2](PF6)4 and [Ag6(L2)2](PF6)4 that involve all six potential donor atoms of the ligands, viz. the four CNHC and two Npz donors, in metal coordination. X‐ray crystallography revealed a chair‐like central {Ag6} deck in both complexes but different arrangements of the ligand strands, which goes along with significantly different AgI ··· AgI distances that indicate more pronounced argentophilic interactions in case of [Ag6(L1)2]4 +. 相似文献
15.
Inside Back Cover: A Reversible Proton Relay Process Mediated by Hydrogen‐Bonding Interactions in [FeFe]Hydrogenase Modeling (Chem. Eur. J. 31/2015) 下载免费PDF全文
Kai‐Ti Chu Dr. Yu‐Chiao Liu Yi‐Lan Huang Cheng‐Huey Hsu Dr. Gene‐Hsiang Lee Prof. Dr. Ming‐Hsi Chiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(31):11255-11255
16.
Back Cover: Ultrafast Photoinduced Charge Separation in Wide‐Band‐Capturing Self‐Assembled Supramolecular Bis(donor styryl)BODIPY–Fullerene Conjugates (Chem. Eur. J. 45/2015) 下载免费PDF全文
Shuai Shao Habtom B. Gobeze Prof. Dr. Paul A. Karr Prof. Dr. Francis D'Souza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):16284-16284
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18.
Edwin Alvarado Anna C. Badaj Timothy G. Larocque Prof. Dr. Gino G. Lavoie 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(38):12112-12121
Gold(I) complexes of 1‐[1‐(2,6‐dimethylphenylimino)alkyl]‐3‐(mesityl)imidazol‐2‐ylidene (C^ImineR), 1,3‐dimesitylimidazol‐2‐ylidene (IMes) and of the corresponding thione derivatives (S^ImineR and IMesS) were prepared and structurally characterised. The solid‐state structure of the C^ImineR and S^ImineR gold(I) complexes showed monodentate coordination of the ligand and a dangling imine group that could bind reversibly to the metal centre to stabilise otherwise unstable catalytic intermediates. Interestingly, reaction of C^IminetBu with [AuCl(SMe2)] led to the formation of [(C^IminetBu)AuCl], which rearranges upon crystallisation into the unusual complex cation [(C^IminetBu)2Au]+, with AuCl2? as the counterion. The activity of the gold complexes in the hydroamination of phenylacetylene with substituted anilines was tested and compared to control catalyst systems. The best catalytic performance was obtained with [(C^IminetBu)AuCl], with the exclusive formation of the Markovnikov addition product in excellent yield (>95 %) regardless of the substituents on aniline. 相似文献
19.
The phenylimidorhenium(V) complexes [Re(NPh)X3(PPh3)2] (X = Cl, Br) react with the N‐heterocyclic carbene (NHC) 1,3‐diethyl‐4,5‐dimethylimidazole‐2‐ylidene (LEt) under formation of the stable rhenium(V) complex cations [Re(NPh)X(LEt)4]2+ (X = Cl, Br), which can be isolated as their chloride or [PF6]? salts. The compounds are remarkably stable against air, moisture and ligand exchange. The hydroxo species [Re(NPh)(OH)(LEt)4]2+ is formed when moist solvents are used during the synthesis. The rhenium atoms in all three complexes are coordinated in a distorted octahedral fashion with the four NHC ligands in equatorial planes of the molecules. The Re–C(carbene) bond lengths between 2.171(8) and 2.221(3) Å indicate mainly σ‐bonding between the NHC ligand and the electron deficient d2 metal atoms. Attempts to prepare analogous phenylimido complexes from [Re(NPh)Cl3(PPh3)2] and 1,3‐diisopropyl‐4,5‐dimethylimidazole‐2‐ylidene (Li?Pr) led to a cleavage of the rhenium‐nitrogen multiple bond and the formation of the dioxo complex [ReO2(Li?Pr)4]+. 相似文献
20.
Palladium‐Catalyzed Direct C2‐Arylation of an N‐Heterocyclic Carbene: An Atom‐Economic Route to Mesoionic Carbene Ligands 下载免费PDF全文
Dr. Rajendra S. Ghadwal Sven O. Reichmann Dr. Regine Herbst‐Irmer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(11):4247-4251
Blocking the C2 position of an imidazole‐derived classical N‐heterocyclic carbene (NHC) with an aryl group is an essential strategy to establish a route to mesoionic carbenes (MICs), which coordinate to the metal via the C4 (or C5) carbon atom. An efficient catalytic route to MIC precursors by direct arylation of an NHC is reported. Treatment of 1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene (IPr) with an aryl iodide (RC6H4I) in the presence of 0.5 mol % of [Pd2(dba)3] (dba=dibenzylideneacetone) precatalyst affords the C2‐arylated imidazolium salts {IPr(C6H4R)}I (R=H, 4‐Me, 2‐Me, 4‐OMe, 4‐COOMe) in excellent (up to 92 %) yields. Treatment of {IPr(C6H5)}I with CuI and KN(SiMe3)2 exclusively affords the MIC–copper complex [(IPrPh)CuI]. 相似文献