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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(30):8916-8920
A series of phosphines featuring a persistent radical were synthesized in two steps by condensation of dialkyl‐/diarylchlorophosphines with stable cyclic (alkyl)(amino)carbenes (cAACs) followed by one‐electron reduction of the corresponding cationic intermediates. Structural, spectroscopic, and computational data indicate that the spin density in these phosphines is mainly localized on the original carbene carbon from the cAAC fragment; thus, it remains in the α‐position with respect to the central phosphorus atom. The potential of these α‐radical phosphines to serve as spin‐labeled ligands is demonstrated through the preparation of several AuI derivatives, which were also structurally characterized by single‐crystal X‐ray diffraction. 相似文献
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Joachim Heinicke Nidhi Gupta Shreeyukta Singh Anushka Surana Olaf Kühl Raj K. Bansal Konstantin Karaghiosoff Martin Vogt 《无机化学与普通化学杂志》2002,628(13):2869-2876
1H‐1, 3‐Benzazaphospholes react with M(CO)5(THF) (M = Cr, Mo, W) to give thermally and relatively air stable η1‐(1H‐1, 3‐Benzazaphosphole‐P)M(CO)5 complexes. The 1H‐ and 13C‐NMR‐data are in accordance with the preservation of the phosphaaromatic π‐system of the ligand. The strong upfield 31P coordination shift, particularly of the Mo and W complexes, forms a contrast to the downfield‐shifts of phosphine‐M(CO)5 complexes and classifies benzazaphospholes as weak donor but efficient acceptor ligands. Nickelocene reacts as organometallic species with metalation of the NH‐function. The resulting ambident 1, 3‐benzazaphospholide anions prefer a μ2‐coordination of the η5‐CpNi‐fragment at phosphorus to coordination at nitrogen or a η3‐heteroallyl‐η5‐CpNi‐semisandwich structure. This is shown by characteristic NMR data and the crystal structure analysis of a η5‐CpNi‐benzazaphospholide. The latter is a P‐bridging dimer with a planar Ni2P2 ring and trans‐configuration of the two planar heterocyclic phosphido ligands arranged perpendicular to the four‐membered ring. 相似文献
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Pyridyl‐Functionalised 3H‐1,2,3,4‐Triazaphospholes: Synthesis,Coordination Chemistry and Photophysical Properties of Low‐Coordinate Phosphorus Compounds 下载免费PDF全文
Julian A. W. Sklorz Santina Hoof Nadine Rades Dr. Nicolas De Rycke László Könczöl Dr. Dénes Szieberth Manuela Weber Dr. Jelena Wiecko Prof. Dr. László Nyulászi Prof. Dr. Muriel Hissler Prof. Dr. Christian Müller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(31):11096-11109
Novel conjugated, pyridyl‐functionalised triazaphospholes with either tBu or SiMe3 substituents at the 5‐position of the N3PC heterocycle have been prepared by a [3+2] cycloaddition reaction and compared with structurally related, triazole‐based systems. Photoexcitation of the 2‐pyridyl‐substituted triazaphosphole gives rise to a significant fluorescence emission with a quantum yield of up to 12 %. In contrast, the all‐nitrogen triazole analogue shows no emission at all. DFT calculations indicate that the 2‐pyridyl substituted systems have a more rigid and planar structure than their 3‐ and 4‐pyridyl isomers. Time‐dependent (TD) DFT calculations show that only the 2‐pyridyl‐substituted triazaphosphole exhibits similar planar geometry, with matching conformational arrangements in the lowest energy excited state and the ground state; this helps to explain the enhanced emission intensity. The chelating P,N‐hybrid ligand forms a ReI complex of the type [(N^N)Re(CO)3Br] through the coordination of nitrogen atom N2 to the metal centre rather than through the phosphorus donor. Both structural and spectroscopic data indicate substantial π‐accepting character of the triazaphosphole, which is again in contrast to that of the all‐nitrogen‐containing triazoles. The synthesis and photophysical properties of a new class of phosphorus‐containing extended π systems are described. 相似文献
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Dinuclear Rare‐Earth Metal Alkyl Complexes Supported by Indolyl Ligands in μ‐η2:η1:η1 Hapticities and their High Catalytic Activity for Isoprene 1,4‐cis‐Polymerization 下载免费PDF全文
Guangchao Zhang Yun Wei Liping Guo Prof. Dr. Xiancui Zhu Prof. Dr. Shaowu Wang Prof. Dr. Shuangliu Zhou Xiaolong Mu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2519-2526
Two series of new dinuclear rare‐earth metal alkyl complexes supported by indolyl ligands in novel μ‐η2:η1:η1 hapticities are synthesized and characterized. Treatment of [RE(CH2SiMe3)3(thf)2] with 1 equivalent of 3‐(tBuN?CH)C8H5NH ( L1 ) in THF gives the dinuclear rare‐earth metal alkyl complexes trans‐[(μ‐η2:η1:η1‐3‐{tBuNCH(CH2SiMe3)}Ind)RE(thf)(CH2SiMe3)]2 (Ind=indolyl, RE=Y, Dy, or Yb) in good yields. In the process, the indole unit of L1 is deprotonated by the metal alkyl species and the imino C?N group is transferred to the amido group by alkyl CH2SiMe3 insertion, affording a new dianionic ligand that bridges two metal alkyl units in μ‐η2:η1:η1 bonding modes, forming the dinuclear rare‐earth metal alkyl complexes. When L1 is reduced to 3‐(tBuNHCH2)C8H5NH ( L2 ), the reaction of [Yb(CH2SiMe3)3(thf)2] with 1 equivalent of L2 in THF, interestingly, generated the trans‐[(μ‐η2:η1:η1‐3‐{tBuNCH2}Ind)Yb(thf)(CH2SiMe3)]2 (major) and cis‐[(μ‐η2:η1:η1‐3‐{tBuNCH2}Ind)Yb(thf)(CH2SiMe3)]2 (minor) complexes. The catalytic activities of these dinuclear rare‐earth metal alkyl complexes for isoprene polymerization were investigated; the yttrium and dysprosium complexes exhibited high catalytic activities and high regio‐ and stereoselectivities for isoprene 1,4‐cis‐polymerization. 相似文献
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Coumaraz‐2‐on‐4‐ylidene: Ambiphilic N‐Heterocyclic Carbenes with a Tunable Electronic Structure 下载免费PDF全文
Hayoung Song Hyunho Kim Prof. Eunsung Lee 《Angewandte Chemie (International ed. in English)》2018,57(28):8603-8607
Herein, a coumaraz‐2‐on‐4‐ylidene ( 1 ) as a new example of an ambiphilic N‐heterocyclic carbene, having electronic properties that can be fine‐tuned, is reported. The N‐carbamic and aryl groups on the carbene carbon center provide exceptionally high electrophilicity and nucleophilicity simultaneously to the carbene center, as evidenced by the 77Se NMR chemical shifts of their selenoketone derivatives and the CO stretching strengths of their rhodium carbonyl complexes. Since the precursors of 1 could be synthesized from various functionalized Schiff bases in a practical and scalable manner, the electronic properties of 1 can be fine‐tuned in a quantitative and predictable way by using the Hammett σ constant of the functional groups on aryl ring. The facile electronic tuning capability of 1 may be applicable to eliciting novel properties in main‐group and transition‐metal chemistry. 相似文献
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Mark Stradiotto Prof. Dr. Kevin D. Hesp Rylan J. Lundgren 《Angewandte Chemie (International ed. in English)》2010,49(3):494-512
Zwitterionic platinum group metal complexes that feature formal charge separation between a cationic metal fragment and a negatively charged ancillary ligand combine the desirable reactivity profile of related cationic complexes with the broad solubility and solvent tolerance of neutral species. As such, zwitterionic complexes of this type have emerged as attractive candidates for a diversity of applications, most notably involving the breaking and/or forming of E? H and E? C σ bonds involving a main group element E. Important advances in ancillary ligand design are documented that have enabled the construction of platinum group metal zwitterions. Also summarized are the results of stoichiometric and catalytic investigations in which the reactivity of such zwitterions and their more traditionally employed cationic relatives in σ bond activation chemistry are compared and contrasted. 相似文献
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Metal(II) Ion Complexes with 5‐(Pyrazin‐2‐yl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione; Synthesis,Structural Characterization,Acid‐base,and Complexing Properties in Solution 下载免费PDF全文
Aleksander Kufelnicki Jolanta Jaciubek‐Rosińska Marta Sobiesiak Agata Paneth Julia Jezierska Elzbieta Budzisz 《无机化学与普通化学杂志》2017,643(16):1067-1074
The study reports the synthesis of complexes Co(HL)Cl2 ( 1 ), Ni(HL)Cl2 ( 2 ), Cu(HL)Cl2 ( 3 ), and Zn(HL)3Cl2 ( 4 ) with the title ligand, 5‐(pyrazin‐2‐yl)‐1,2,4‐triazole‐5‐thione (HL), and their characterization by elemental analyses, ESI‐MS (m/z), FT‐IR and UV/Vis spectroscopy, as well as EPR in the case of the CuII complex. The comparative analysis of IR spectra of the metal ion complexes with HL and HL alone indicated that the metal ions in 1 , 2 , and 3 are chelated by two nitrogen atoms, N(4) of pyrazine and N(5) of triazole in the thiol tautomeric form, whereas the ZnII ion in 4 is coordinated by the non‐protonated N(2) nitrogen atom of triazole in the thione form. pH potentiometry and UV/Vis spectroscopy were used to examine CoII, NiII, and ZnII complexes in 10/90 (v/v) DMSO/water solution, whereas the CuII complex was examined in 40/60 (v/v) DMSO/water solution. Monodeprotonation of the thione triazole in solution enables the formation of the L:M = 1:1 species with CoII, NiII and ZnII, the 2:1 species with CoII and ZnII, and the 3:1 species with ZnII. A distorted tetrahedral arrangement of the CuII complex was suggested on the basis of EPR and Vis/NIR spectra. 相似文献
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Feng Jia Prof. Shu Zhang Xiaokun Zhang Xiaoli Peng Haitao Zhang Prof. Yong Xiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(48):15941-15946
Control over phase stabilities during synthesis processes is of great importance for both fundamental studies and practical applications. We describe herein a facile strategy for the synthesis of Cu2Se with phase selectivity through a simple solvothermal method. In the presence and absence of SbCl3, monoclinic α‐Cu2Se and cubic β‐Cu2Se can be synthesized, respectively. The formation of α‐Cu2Se requires optimization of the Cu/Se molar ratio in the starting reagents, the reaction temperature, as well as the timing for the addition of SbCl3. Differential scanning calorimetry of the synthesized α‐Cu2Se has shown that a part of it undergoes a phase transition to β‐Cu2Se at 135 °C, and that this phase transition is irreversible on cooling to ambient temperature. Kinetic studies have revealed that in the presence of Sb species the kinetically favored β‐Cu2Se transforms to the thermodynamically favored α‐Cu2Se. In this β‐to‐α phase transition process, the distribution of Cu ions in β‐Cu2Se, as determined by the Cu/Se ratio and temperature, is likely to play a crucial role. 相似文献
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Prof. Dr. Barry M. Trost Dr. Lara C. Czabaniuk 《Angewandte Chemie (International ed. in English)》2014,53(11):2826-2851
The coordination of transition metals to organic fragments can yield complexes with fascinating and unexpected binding patterns. The study of metal‐benzyl complexes has demonstrated the feasibility of η3‐coordination, which results in a dearomatized ring. These complexes also offer insight into reaction mechanisms as proposed intermediates in catalytic cycles. In this Review we discuss the synthesis and characterization of these complexes with late transition metals and the subsequent development of catalytic benzylic functionalization methods, including asymmetric variants. 相似文献
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Yasumasa Hamada 《Chemical record (New York, N.Y.)》2014,14(2):235-250
This review describes our recent works on the diastereo‐ and enantioselective synthesis of anti‐β‐hydroxy‐α‐amino acid esters using transition‐metal–chiral‐bisphosphine catalysts. A variety of transition metals, namely ruthenium (Ru), rhodium (Rh),iridium (Ir), and nickel (Ni), in combination with chiral bisphosphines, worked well as catalysts for the direct anti‐selective asymmetric hydrogenation of α‐amino‐β‐keto ester hydrochlorides, yielding anti‐β‐hydroxy‐α‐amino acid esters via dynamic kinetic resolution (DKR) in excellent yields and diastereo‐ and enantioselectivities. The Ru‐catalyzed asymmetric hydrogenation of α‐amino‐β‐ketoesters via DKR is the first example of generating anti‐β‐hydroxy‐α‐amino acids. Complexes of iridium and axially chiral bisphosphines catalyze an efficient asymmetric hydrogenation of α‐amino‐β‐keto ester hydrochlorides via dynamic kinetic resolution. A homogeneous Ni–chiral‐bisphosphine complex also catalyzes an efficient asymmetric hydrogenation of α‐amino‐β‐keto ester hydrochlorides in an anti‐selective manner. As a related process, the asymmetric hydrogenation of the configurationally stable substituted α‐aminoketones using a Ni catalyst via DKR is also described. 相似文献
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Catalytic Asymmetric Michael Reaction of 5H‐Oxazol‐4‐Ones with α,β‐Unsaturated Acyl Imidazoles 下载免费PDF全文
Bangzhi Zhang Fengxia Han Linqing Wang Dan Li Dongxu Yang Xiaoli Yang Junxian Yang Xiaofang Li Dr. Depeng Zhao Prof. Dr. Rui Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17234-17238
The asymmetric Michael reaction between 5H‐oxazol‐4‐ones and α,β‐unsaturated acyl imidazoles is reported. A novel 2‐benzo[b]thiophenyl‐modified chiral ProPhenol species is synthesized and used as a ligand, leading to good enantioselectivities in this asymmetric conjugate addition reaction. Furthermore, the introduction of phenol additives as achiral co‐ligands is found to improve the reaction’s chemical yields, diastereoselectivities, and enantioselectivities. 相似文献
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M. Sc. Yen‐Chun Lee Dr. Kamal Kumar Prof. Dr. Herbert Waldmann 《Angewandte Chemie (International ed. in English)》2018,57(19):5212-5226
Chemical tools that enable a catalytic reaction to selectively and efficiently yield different products will allow charting of wider chemical space. In ligand‐directed divergent synthesis, a common mode of catalysis is modulated by employing different ligands for catalytic organometallic complexes to transform either common substrates or common reactive intermediates into distinct molecular scaffolds. The strategy has the potential to create important and diverse scaffolds and to unveil novel modes of catalytic transformations for wider synthetic applications. This strategy is described and recent efforts in this emerging field of catalysis, focusing on transition‐metal catalysis for the synthesis of carbo‐ and heterocyclic ring systems, are reviewed. 相似文献
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Dr. Kai E. O. Ylijoki Prof. Dr. Peter H. M. Budzelaar Prof. Dr. Jeffrey M. Stryker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(32):9894-9900
Alkyl‐substituted η5‐pentadienyl half‐sandwich complexes of cobalt have been reported to undergo [5+2] cycloaddition reactions with alkynes to provide η2,η3‐cycloheptadienyl complexes under kinetic control. DFT studies have been used to elucidate the mechanism of the cyclization reaction as well as that of the subsequent isomerization to the final η5‐cycloheptadienyl product. The initial cyclization is a stepwise process of olefin decoordination/alkyne capture, C? C bond formation, olefin arm capture, and a second C? C bond formation; the initial decoordination/capture step is rate‐limiting. Once the η2,η3‐cycloheptadienyl complex has been formed, isomerization to η5‐cycloheptadienyl again involves several steps: olefin decoordination, β‐hydride elimination, reinsertion, and olefin coordination; also here the initial decoordination step is rate limiting. Substituents strongly affect the ease of reaction. Pentadienyl substituents in the 1‐ and 5‐positions assist pentadienyl opening and hence accelerate the reaction, while substituents at the 3‐position have a strongly retarding effect on the same step. Substituents at the alkyne (2‐butyne vs. ethyne) result in much faster isomerization due to easier olefin decoordination. Paths involving triplet states do not appear to be competitive. 相似文献
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《化学:亚洲杂志》2017,12(18):2335-2342
Chirality is an essential feature of asymmetric catalysts. This review summarizes asymmetric catalysts that derive their chirality exclusively from stereogenic metal centers. Reported chiral‐at‐metal catalysts can be divided into two classes, namely, inert metal complexes, in which the metal fulfills a purely structural role, so catalysis is mediated entirely through the ligand sphere, and reactive metal complexes. The latter are particularly appealing because structural simplicity (only achiral ligands) is combined with the prospect of particularly effective asymmetric induction (direct contact of the substrate with the chiral metal center). Challenges and solutions for the design of such reactive stereogenic‐only‐at‐metal asymmetric catalysts are discussed. 相似文献