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1.
Sébastien Perdriau Mu‐Chieh Chang Dr. Edwin Otten Prof. Dr. Hero J. Heeres Prof. Dr. Johannes G. de Vries 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15434-15442
The [Ru(CO)H(PNN)] pincer complex based on a dearomatised PNN ligand (PNN: 2‐di‐tert‐butylphosphinomethyl‐6‐diethylaminomethylpyridine) was examined for its ability to isomerise alkenes. The isomerisation reaction proceeded under mild conditions after activation of the complex with alcohols. Variable‐temperature (VT) NMR experiments to investigate the role of the alcohol in the mechanism lend credence to the hypothesis that the first step involves the formation of a rearomatised alkoxide complex. In this complex, the hemilabile diethylamino side‐arm can dissociate, allowing alkene binding cis to the hydride, enabling insertion of the alkene into the metal–hydride bond, whereas in the parent complex only trans binding is possible. During this study, a new uncommon Ru0 coordination complex was also characterised. The scope of the alkene isomerisation reaction was examined. 相似文献
2.
Dr. Robert Langer Ido Fuchs Dr. Matthias Vogt Dr. Ekambaram Balaraman Dr. Yael Diskin‐Posner Dr. Linda J. W. Shimon Yehoshoa Ben‐David Prof. Dr. David Milstein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(10):3407-3414
The synthesis and reactivity of ruthenium complexes containing the tetradentate phenanthroline‐based phosphine ligand 2,9‐bis((di‐tert‐butylphosphino)methyl)‐1,10‐phenanthroline (PPhenP) is described. The hydrido chloro complex [RuHCl(PPhenP)] ( 2 ) undergoes facile dearomatization upon deprotonation of the benzylic position, to give [RuH(PPhenP‐H)] ( 4 ). Addition of dihydrogen to 4 causes rearomatization of the phenanthroline moiety to trans‐[Ru(H)2(PPhenP)] ( 5 ), followed by hydrogenation of an aromatic heterocycle in the ligand backbone, to give a new dearomatized and deconjugated complex [RuH(PPhenP*‐H)] ( 6 ). These aromatization/deconjugation steps of the coordinated ligand were demonstrated to be reversible and operative in the dehydrogenation of primary alcohols without the need for a hydrogen acceptor. This aromatization/deconjugation sequence constitutes an unprecedented mode of a stepwise cooperation between the metal center and the coordinated ligand. 相似文献
3.
Intramolecular CH/OH Bond Cleavage with Water and Alcohol Using a Phosphine‐Free Ruthenium Carbene NCN Pincer Complex
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Demyan E. Prokopchuk Brian T. H. Tsui Dr. Alan J. Lough Prof. Dr. Robert H. Morris 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):16960-16968
Transition metal complexes that exhibit metal–ligand cooperative reactivity could be suitable candidates for applications in water splitting. Ideally, the ligands around the metal should not contain oxidizable donor atoms, such as phosphines. With this goal in mind, we report new phosphine‐free ruthenium NCN pincer complexes with a central N‐heterocyclic carbene donor and methylpyridyl N‐donors. Reaction with base generates a neutral, dearomatized alkoxo–amido complex, which has been structurally and spectroscopically characterized. The tert‐butoxide ligand facilitates regioselective, intramolecular proton transfer through a C?H/O?H bond cleavage process occurring at room temperature. Kinetic and thermodynamic data have been obtained by VT NMR experiments; DFT calculations support the observed behavior. Isolation and structural characterization of a doubly dearomatized phosphine complex also strongly supports our mechanistic proposal. The alkoxo–amido complex reacts with water to form a dearomatized ruthenium hydroxide complex, a first step towards phosphine‐free metal–ligand cooperative water splitting. 相似文献
4.
Metal–Ligand Cooperation on a Diruthenium Platform: Selective Imine Formation through Acceptorless Dehydrogenative Coupling of Alcohols with Amines
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Biswajit Saha S. M. Wahidur Rahaman Prosenjit Daw Gargi Sengupta Prof. Jitendra K. Bera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6542-6551
Metal?metal singly‐bonded diruthenium complexes, bridged by naphthyridine‐functionalized N‐heterocyclic carbene (NHC) ligands featuring a hydroxy appendage on the naphthyridine unit, are obtained in a single‐pot reaction of [Ru2(CH3COO)2(CO)4] with 1‐benzyl‐3‐(5,7‐dimethyl‐1,8‐naphthyrid‐2‐yl)imidazolium bromide (BIN ? HBr) or 1‐isopropyl‐3‐(5,7‐dimethyl‐1,8‐naphthyrid‐2‐yl)imidazolium bromide (PIN ? HBr), TlBF4, and substituted benzaldehyde containing an electron‐withdrawing group. The modified NHC‐naphthyridine‐hydroxy ligand spans the diruthenium unit in which the NHC carbon and hydroxy oxygen occupy the axial sites. All the synthesized compounds catalyze acceptorless dehydrogenation of alcohols to the corresponding aldehydes in the presence of a catalytic amount of weak base 1,4‐diazabicyclo[2.2.2]octane (DABCO). Further, acceptorless dehydrogenative coupling (ADHC) of the alcohol with amines affords the corresponding imine as the sole product. The substrate scope is examined with 1 (BIN, p‐nitrobenzaldehyde). A similar complex [Ru2(CO)4(CH3COO)(3‐PhBIN)][Br], that is devoid of a hydroxy arm, is significantly less effective for the same reaction. Neutral complex 1 a , obtained by deprotonation of the hydroxy arm in 1 , is found to be active for the ADHC of alcohols and amines under base‐free conditions. A combination of control experiments, deuterium labeling, kinetic Hammett studies, and DFT calculations support metal–hydroxyl/hydroxide and metal–metal cooperation for alcohol activation and dehydrogenation. The bridging acetate plays a crucial role in allowing β‐hydride elimination to occur. The ligand architecture on the diruthenium core causes rapid aldehyde extrusion from the metal coordination sphere, which is responsible for exclusive imine formation. 相似文献
5.
Ben-Ari E Leitus G Shimon LJ Milstein D 《Journal of the American Chemical Society》2006,128(48):15390-15391
Unusual reactions are reported, in which the aromatic PNP ligand (PNP = 2,6-bis-(di-tert-butylphosphinomethyl)pyridine) acts in concert with the metal in the activation of H2 and benzene, via facile aromatization/dearomatization processes of the ligand. A new, dearomatized electron-rich (PNP*)Ir(I) complex 2 (PNP* = deprotonated PNP) activates benzene to form the aromatic (PNP)Ir(I)Ph 4, which upon treatment with CO undergoes a surprising oxidation process to form (PNP*)Ir(III)(H)CO 6, involving proton migration from the ligand "arm" to the metal, with concomitant dearomatization. 4 undergoes stereoselective activation of H2 to exclusively form the trans-dihydride 7, rather than the expected cis-dihydride complex. Our evidence, including D-labeling, suggests the possibility that the Ir(I)-Ph complex is transformed to the dearomatized Ir(III)(Ph)(H) (independently prepared at low temperature), which may be the actual intermediate undergoing H2 activation. 相似文献
6.
Selective Hydrogen Generation from Formic Acid with Well‐Defined Complexes of Ruthenium and Phosphorus–Nitrogen PN3‐Pincer Ligand
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Dr. Yupeng Pan Dr. Cheng‐Ling Pan Yufan Zhang Dr. Huaifeng Li Dr. Shixiong Min Dr. Xunmun Guo Dr. Bin Zheng Dr. Hailong Chen Addison Anders Prof. Zhiping Lai Prof. Junrong Zheng Prof. Kuo‐Wei Huang 《化学:亚洲杂志》2016,11(9):1357-1360
An unsymmetrically protonated PN3‐pincer complex in which ruthenium is coordinated by one nitrogen and two phosphorus atoms was employed for the selective generation of hydrogen from formic acid. Mechanistic studies suggest that the imine arm participates in the formic acid activation/deprotonation step. A long life time of 150 h with a turnover number over 1 million was achieved. 相似文献
7.
A Metal–Ligand Cooperative Pathway for Intermolecular Oxa‐Michael Additions to Unsaturated Nitriles
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Sébastien Perdriau Douwe S. Zijlstra Prof. Dr. Hero J. Heeres Prof. Dr. Johannes G. de Vries Dr. Edwin Otten 《Angewandte Chemie (International ed. in English)》2015,54(14):4236-4240
An unprecedented catalytic pathway for oxa‐Michael addition reactions of alcohols to unsaturated nitriles has been revealed using a PNN pincer ruthenium catalyst with a dearomatized pyridine backbone. The isolation of a catalytically competent Ru–dieneamido complex from the reaction between the Ru catalyst and pentenenitrile in combination with DFT calculations supports a mechanism in which activation of the nitrile through metal–ligand cooperativity is a key step. The nitrile‐derived Ru‐N moiety is sufficiently Brønsted basic to activate the alcohol and initiate conjugate addition of the alkoxide to the α,β‐unsaturated fragment. This reaction proceeds in a concerted manner and involves a six‐membered transition state. These features allow the reaction to proceed at ambient temperature in the absence of external base. 相似文献
8.
Concurrent Stabilization of π‐Donor and π‐Acceptor Ligands in Aromatized and Dearomatized Pincer [(PNN)Re(CO)(O)2] Complexes
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Michael G. Mazzotta Dr. Kothanda Rama Pichaandi Dr. Phillip E. Fanwick Prof. Dr. Mahdi M. Abu‐Omar 《Angewandte Chemie (International ed. in English)》2014,53(32):8320-8322
Aromatized cationic [(PNN)Re(π acid)(O)2]+ ( 1 ) and dearomatized neutral [(PNN*)Re(π acid)(O)2] ( 2 ) complexes (where π acid=CO ( a ), tBuNC ( b ), or (2,6‐Me2)PhNC ( c )), possessing both π‐donor and π‐acceptor ligands, have been synthesized and fully characterized. Reaction of [(PNN)Re(O)2]+ ( 4 ) with lithiumhexamethyldisilazide (LiHMDS) yield the dearomatized [(PNN*)Re(O)2] ( 3 ). Complexes 1 and 2 are prepared from the reaction of 4 and 3 , respectively, with CO or isocyanides. Single‐crystal X‐ray structures of 1 a and 1 b show the expected trans‐dioxo structure, in which the oxo ligands occupy the axial positions and the π‐acidic ligand occupies the equatorial plane in an overall octahedral geometry about the rhenium(V) center. DFT studies revealed the stability of complexes 1 and 2 arises from a π‐backbonding interaction between the dxy orbital of rhenium, the π orbital of the oxo ligands, and the π* orbital of CO/isocyanide. 相似文献
9.
Barry M. Trost Subham Mahapatra Martin Hansen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(20):6130-6134
A new mode of activation of an imine via a rare aza‐substituted π‐allyl complex is described. Palladium‐catalyzed C(sp3) H activation of the N‐allyl imine and the subsequent nucleophilic attack by the α‐alkyl cyanoester produced the 1‐aza‐1,3‐diene as the sole regioisomer. In contrast, nucleophilic attack by the α‐aryl cyanoester exclusively delivered the 2‐aza‐1,3‐diene, which was employed in an inverse‐electron‐demand Diels–Alder reaction for heterobiaryl synthesis. 相似文献
10.
Weiqing Mao Yaya Wang Dr. Li Xiang Prof. Dr. Qian Peng Dr. Xuebing Leng Prof. Dr. Yaofeng Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(44):10304-10308
Reaction of a scandium phosphoniomethylidene with carbon monoxide provides the first scandium phosphonioketene ( 1 ). X-ray diffraction analysis shows that the complex has a very short Sc−C bond (2.138(2) Å), and DFT calculations indicate that this unusual short bond length is due to the significant contribution of ionic coulomb interaction between carbon and scandium and the η2-O,C coordination fashion. Complex 1 is thermally stable, albeit shows high reactivity towards a series of unsaturated substrates, including carbon dioxide, ketone, imine, nitrile and isocyanide. In the reaction with tert-butyl isocyanide, not only an insertion of tert-butyl isocyanide into the Sc−C bond occur, but also a C−H activation on the phenyl ring. DFT calculations show that the reactivity of 1 operated by nucleophilic properties, and therefore the reaction mechanism favors the nucleophilic attack to isocyanide as a rate-determining step, followed by the stepwise C−H activation through an interesting C−H deprotonation. 相似文献
11.
Palladium‐Catalyzed CH Activation of N‐Allyl Imines: Regioselective Allylic Alkylations to Deliver Substituted Aza‐1,3‐Dienes
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Prof. Dr. Barry M. Trost Dr. Subham Mahapatra Dr. Martin Hansen 《Angewandte Chemie (International ed. in English)》2015,54(20):6032-6036
A new mode of activation of an imine via a rare aza‐substituted π‐allyl complex is described. Palladium‐catalyzed C(sp3)? H activation of the N‐allyl imine and the subsequent nucleophilic attack by the α‐alkyl cyanoester produced the 1‐aza‐1,3‐diene as the sole regioisomer. In contrast, nucleophilic attack by the α‐aryl cyanoester exclusively delivered the 2‐aza‐1,3‐diene, which was employed in an inverse‐electron‐demand Diels–Alder reaction for heterobiaryl synthesis. 相似文献
12.
Dr. Robert Langer Dr. Mark A. Iron Dr. Leonid Konstantinovski Dr. Yael Diskin‐Posner Dr. Gregory Leitus Yehoshoa Ben‐David Prof. Dr. David Milstein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(23):7196-7209
The new, structurally characterized hydrido carbonyl tetrahydridoborate iron pincer complex [(iPr‐PNP)Fe(H)(CO)(η1‐BH4)] ( 1 ) catalyzes the base‐free hydrogenation of ketones to their corresponding alcohols employing only 4.1 atm hydrogen pressure. Turnover numbers up to 1980 at complete conversion of ketone were reached with this system. Treatment of 1 with aniline (as a BH3 scavenger) resulted in a mixture of trans‐[(iPr‐PNP)Fe(H)2(CO)] ( 4 a ) and cis‐[(iPr‐PNP)Fe(H)2(CO)] ( 4 b ). The dihydrido complexes 4 a and 4 b do not react with acetophenone or benzaldehyde, indicating that these complexes are not intermediates in the catalytic reduction of ketones. NMR studies indicate that the tetrahydridoborate ligand in 1 dissociates prior to ketone reduction. DFT calculations show that the mechanism of the iron‐catalyzed hydrogenation of ketones involves alcohol‐assisted aromatization of the dearomatized complex [(iPr‐PNP*)Fe(H)(CO)] ( 7 ) to initially give the Fe0 complex [(iPr‐PNP)Fe(CO)] ( 21 ) and subsequently [(iPr‐PNP)Fe(CO)(EtOH)] ( 38 ). Concerted coordination of acetophenone and dual hydrogen‐atom transfer from the PNP arm and the coordinated ethanol to, respectively, the carbonyl carbon and oxygen atoms, leads to the dearomatized complex [(iPr‐PNP*)Fe(CO)(EtO)(MeCH(OH)Ph)] ( 32 ). The catalyst is regenerated by release of 1‐phenylethanol, followed by dihydrogen coordination and proton transfer to the coordinated ethoxide ligand. 相似文献
13.
Efficient synthesis of amides directly from esters and amines is achieved under mild, neutral conditions with the liberation of molecular hydrogen. Both primary and secondary amines can be utilized. This unprecedented, general, environmentally benign reaction is homogeneously catalyzed under neutral conditions by a dearomatized ruthenium-pincer PNN complex and proceeds in toluene under an inert atmosphere with a high turnover number (up to 1000). PNP analogues do not catalyze this transformation, underlining the crucial importance of the amine arm of the pincer ligand. A mechanism is proposed involving metal-ligand cooperation via aromatization-dearomatization of the pyridine moiety and hemilability of the amine arm. 相似文献
14.
Iron Dicarbonyl Complexes Featuring Bipyridine‐Based PNN Pincer Ligands with Short Interpyridine CC Bond Lengths: Innocent or Non‐Innocent Ligand?
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Dr. Thomas Zell Dr. Petr Milko Kathlyn L. Fillman Dr. Yael Diskin‐Posner Dr. Tatyana Bendikov Dr. Mark A. Iron Dr. Gregory Leitus Yehoshoa Ben‐David Prof. Michael L. Neidig Prof. David Milstein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(15):4403-4413
15.
Cristina Tejel Dr. M. Pilar del Río Dr. Miguel A. Ciriano Prof. Dr. Eduard J. Reijerse Dr. František Hartl Prof. Stanislav Záliš Dr. Dennis G. H. Hetterscheid Dr. Nearchos Tsichlis i Spithas Bas de Bruin Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(44):11878-11889
Treatment of [Ir(bpa)(cod)]+ complex [ 1 ]+ with a strong base (e.g., tBuO?) led to unexpected double deprotonation to form the anionic [Ir(bpa?2H)(cod)]? species [ 3 ]?, via the mono‐deprotonated neutral amido complex [Ir(bpa?H)(cod)] as an isolable intermediate. A certain degree of aromaticity of the obtained metal–chelate ring may explain the favourable double deprotonation. The rhodium analogue [ 4 ]? was prepared in situ. The new species [M(bpa?2H)(cod)]? (M=Rh, Ir) are best described as two‐electron reduced analogues of the cationic imine complexes [MI(cod)(Py‐CH2‐N?CH‐Py)]+. One‐electron oxidation of [ 3 ]? and [ 4 ]? produced the ligand radical complexes [ 3 ]. and [ 4 ].. Oxygenation of [ 3 ]? with O2 gave the neutral carboxamido complex [Ir(cod)(py‐CH2‐N‐CO‐py)] via the ligand radical complex [ 3 ]. as a detectable intermediate. 相似文献
16.
Christian M. Hoidn Thomas M. Maier Karolina Trabitsch Jan J. Weigand Robert Wolf 《Angewandte Chemie (International ed. in English)》2019,58(52):18931-18936
The activation of white phosphorus (P4) by transition‐metal complexes has been studied for several decades, but the functionalization and release of the resulting (organo)phosphorus ligands has rarely been achieved. Herein we describe the formation of rare diphosphan‐1‐ide anions from a P5 ligand by treatment with cyanide. Cobalt diorganopentaphosphido complexes have been synthesized by a stepwise reaction sequence involving a low‐valent diimine cobalt complex, white phosphorus, and diorganochlorophosphanes. The reactions of the complexes with tetraalkylammonium or potassium cyanide afford a cyclotriphosphido cobaltate anion 5 and 1‐cyanodiphosphan‐1‐ide anions [R2PPCN]? ( 6‐R ). The molecular structure of a related product 7 suggests a novel reaction mechanism, where coordination of the cyanide anion to the cobalt center induces a ligand rearrangement. This is followed by nucleophilic attack of a second cyanide anion at a phosphorus atom and release of the P2 fragment. 相似文献
17.
Carlos A. Blanco 《国际化学动力学杂志》2000,32(3):178-183
Decomplexation rates of chromium(III) chelates of dicarbonylic and tricarbonylic ligands in aqueous solution have been evaluated. Results show an extreme nonlability of these metal complexes that does not depend on the chelating ligand structure. A more extensive analysis including structurally similar complexes of first‐row transition metal ions [Ni(II), Co(II), and Cu(II)] shows decomplexation rate values at least 104 times higher than the rate constants of previously mentioned chromium metal complexes. Correlations between the decomplexation rate constants and the deprotonation capability of the enol tautomer suggest that the decomplexation rates of a structurally similar 1:1 chelate of quoted metal ions may be predicted from the ligand dissociation constant. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 178–183, 2000 相似文献
18.
A new air‐stable Pd(II) complex containing a sulfonamide–Schiff base ligand has been synthesized, characterized and investigated as a catalyst for the Suzuki–Miyaura reactions of aryl halides with arylboronic acids. Theoretical calculations (B3LYP) and spectroscopic evidence suggest that the sulfonamide–Schiff base coordinates to the Pd centre through sulfonamide nitrogen (? SO2NH2) rather than imine (? CH?N). The complex shows excellent cross‐coupling activity with aryl bromides in water at room temperature and aryl chlorides in isopropanol at 60°C. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
19.
Non‐Pincer‐Type Mononuclear Scandium Alkylidene Complexes: Synthesis,Bonding, and Reactivity
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Chen Wang Dr. Jiliang Zhou Xuefei Zhao Prof. Dr. Laurent Maron Dr. Xuebing Leng Prof. Dr. Yaofeng Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1258-1261
The first non‐pincer‐type mononuclear scandium alkylidene complexes were synthesized and structurally characterized. These complexes exhibited short Sc?C bond lengths and even one of the shortest reported to date (2.1134(18) Å). The multiple character of the Sc?C bond was highlighted by a DFT calculation. This was confirmed by experimental reactivity study where the complex underwent [2+1] cycloaddition with elemental selenium and [2+2] cycloaddition with imine. DFT calculation also revealed a strong nucleophilic behavior of the alkylidene complex that was experimentally demonstrated by the C?H bond activation of phenylacetylene. 相似文献
20.
Hao Guo Lie‐Wei Zhang Hao Zhou Wei Meng Yu‐Fei Ao De‐Xian Wang Qi‐Qiang Wang 《Angewandte Chemie (International ed. in English)》2020,59(7):2623-2627
An artificial system of substrate‐induced dimerization assembly of chiral macrocycle catalysts enables a highly cooperative hydrogen‐bonding activation network for efficient enantioselective transformation. These macrocycles contain two thiourea and two chiral diamine moieties and dimerize with sulfate to form a sandwich‐like assembly. The macrocycles then adopt an extended conformation and reciprocally complement the hydrogen‐bonding interaction sites. Inspired by the guest‐induced dynamic assembly, these macrocycles catalyze the decarboxylative Mannich reaction of cyclic aldimines containing a sulfamate heading group. The imine substrate can be activated toward nucleophilic attack of β‐ketoacid by a cooperative hydrogen‐bonding network enabled by sulfamate‐induced dimerization assembly of the macrocycle catalysts. Highly efficient (>95 % yield in most cases) and enantioselective (up to 97.5:2.5 er) transformation of a variety of substrates using only 5 mol % macrocycle was achieved. 相似文献