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1.
Dr. Wenlong Yang Kelsie E. Krantz Dr. Diane A. Dickie Andrew Molino Prof. Dr. David J. D. Wilson Prof. Dr. Robert J. Gilliard Jr. 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(10):3999-4003
The synthesis and reactivity study of the first isolable boraphosphaketene, cyclic(alkyl)(amino) carbene (CAAC)-borafluorene-P=C=O ( 2 ), is described. Photolysis of compound 2 results in the formation of CAAC-stabilized BP-doped phenanthryne ( 3 ) through tandem decarbonylation, monoatomic phosphide insertion, and ring-expansion. Notably, while BN-doped phenanthryne was previously discussed as a reactive intermediate which could not be isolated, the heavier BP-doped analogue exhibits remarkable solution and solid-state stability. The reactivity of 2 with stable carbenes was also explored. Addition of CAAC to 2 led to migration of the original CAAC ligand from boron to phosphorus and coordination of the added CAAC to carbon, affording compound 4 . Reaction of 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (NHC) with 2 resulted in N−C bond activation to give the unusual spiro-heterocyclic compound ( 5 ). 相似文献
2.
Julian Böhnke Prof. Dr. Holger Braunschweig Theresa Dellermann Dr. William C. Ewing Thomas Kramer Dr. Ivo Krummenacher Dr. Alfredo Vargas 《Angewandte Chemie (International ed. in English)》2015,54(15):4469-4473
The reaction of the bisboracumulene (CAAC)2B2 (CAAC=1‐(2,6‐diisopropylphenyl)‐3,3,5,5‐tetramethylpyrrolidin‐2‐ylidene) with excess tert‐butylisocyanide resulted in complexation of the isocyanide at boron. Though this compound might be formally drawn with a lone pair on boron, these electrons are highly delocalized throughout a conjugated π‐network consisting of the π‐acidic CAAC and isocyanide ligands. Heating this compound to 110 °C liberated the organic periphery of both isocyanide ligands, yielding the first example of a dicyanodiborene. Cyclic voltammetry conducted on this diborene indicated the presence of reduction waves, making this compound unique among diborenes, which are otherwise highly reducing. 相似文献
3.
Low‐Temperature N2 Binding to Two‐Coordinate L2Fe0 Enables Reductive Trapping of L2FeN2− and NH3 Generation 下载免费PDF全文
Dr. Gaël Ung Prof. Jonas C. Peters 《Angewandte Chemie (International ed. in English)》2015,54(2):532-535
The two‐coordinate [(CAAC)2Fe] complex [CAAC=cyclic (alkyl)(amino)carbene] binds dinitrogen at low temperature (T80 °C). The resulting putative three‐coordinate N2 complex, [(CAAC)2Fe(N2)], was trapped by one‐electron reduction to its corresponding anion [(CAAC)2FeN2]? at low temperature. This complex was structurally characterized and features an activated dinitrogen unit which can be silylated at the β‐nitrogen atom. The redox‐linked complexes [(CAAC)2FeI][BArF4], [(CAAC)2Fe0], and [(CAAC)2Fe?IN2]? were all found to be active for the reduction of dinitrogen to ammonia upon treatment with KC8 and HBArF4?2 Et2O at ?95 °C [up to (3.4±1.0) equivalents of ammonia per Fe center]. The N2 reduction activity is highly temperature dependent, with significant N2 reduction to NH3 only occurring below ?78 °C. This reactivity profile tracks with the low temperatures needed for N2 binding and an otherwise unavailable electron‐transfer step to generate reactive [(CAAC)2FeN2]?. 相似文献
4.
Correlations and Contrasts in Homo‐ and Heteroleptic Cyclic (Alkyl)(amino)carbene‐Containing Pt0 Complexes 下载免费PDF全文
Nicole Arnold Prof. Dr. Holger Braunschweig Dr. Peter B. Brenner Dr. Mehmet Ali Celik Dr. Rian D. Dewhurst Dr. Martin Haehnel Dr. Thomas Kramer Dr. Ivo Krummenacher Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(35):12357-12362
An improved synthetic route to homoleptic complex [Pt(CAACMe)2] (CAAC=cyclic (alkyl)(amino)carbenes) and convenient routes to new heteroleptic complexes of the form [Pt(CAACMe)(PR3)] are presented. Although the homoleptic complex was found to be inert to many reagents, oxidative addition and metal‐only Lewis pair (MOLP) formation was observed from one of the heteroleptic complexes. The spectroscopic, structural, and electrochemical properties of the zero‐valent complexes were explored in concert with density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) calculations. The homoleptic [Pt(CAAC)2] and heteroleptic [Pt(CAAC)(PR3)] complexes were found to be similar in their spectroscopic and structural properties, but their electrochemical behavior and reactivity differ greatly. The unusually strong color of the CAAC‐containing Pt0 complexes was investigated by TD‐DFT calculations and attributed to excitations into the LUMOs of the complexes, which are predominantly composed of bonding π interactions between Pt and the CAAC carbon atoms. 相似文献
5.
Prof. Dr. Holger Braunschweig Dr. William C. Ewing Dr. K. Geetharani Marius Schäfer 《Angewandte Chemie (International ed. in English)》2015,54(5):1662-1665
The first examples of adducts of cyclic alkyl(amino) carbenes (CAAC) and N‐heterocyclic carbenes (NHCs) with iminoboranes have been synthesized and isolated at low temperature (?45 °C). The adducts show short B?N bonds and planarity at boron, mimicking the structures of the isoelectronic imine functionality. When di‐tert‐butyliminoborane was reacted with 1,3‐bis(isopropyl)imidazol‐2‐ylidene (IPr), the initially formed Lewis acid–base adduct quickly rearranged to form a new carbene substituted with an aminoborane at the 4‐position. Warming the iminoborane–CAAC adduct to room temperature resulted in an intramolecular cyclization to give a bicyclic 1,2‐azaborilidine compound. 相似文献
6.
Julian Böhnke Prof. Dr. Holger Braunschweig Dr. William C. Ewing Dr. Christian Hörl Thomas Kramer Dr. Ivo Krummenacher Dr. Jan Mies Dr. Alfredo Vargas 《Angewandte Chemie (International ed. in English)》2014,53(34):9082-9085
The complexation of two equivalents of a cyclic (alkyl)(amino)carbene (CAAC) to tetrabromodiborane, followed by reduction with four equivalents of sodium naphthalide, led to the formation of the CAAC‐stabilized linear diboracumulene (CAAC)2B2. The capacity of the CAAC ligand to facilitate B2→CAAC donation of π‐electron density resulted in important differences between this species and a previously reported complex featuring a B?B triple bond stabilized by cyclic di(amino)carbenes, including a longer B? B bond and shorter B? C bonds. Frontier orbital analysis indicated sharing of valence electrons across the entire linear C‐B‐B‐C unit in (CAAC)2B2, which is supported by natural population analysis and cyclic voltammetry. 相似文献
7.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(4):1001-1006
The state‐of‐the‐art in olefin metathesis is application of N‐heterocyclic carbene (NHC)‐containing ruthenium alkylidenes for the formation of internal C=C bonds and of cyclic alkyl amino carbene (CAAC)‐containing ruthenium benzylidenes in the production of terminal olefins. A straightforward synthesis of bis(CAAC)Ru indenylidene complexes, which are highly effective in the formation of both terminal and internal C=C bonds at loadings as low as 1 ppm, is now reported. 相似文献
8.
《Angewandte Chemie (International ed. in English)》2017,56(4):981-986
The state‐of‐the‐art in olefin metathesis is application of N‐heterocyclic carbene (NHC)‐containing ruthenium alkylidenes for the formation of internal C=C bonds and of cyclic alkyl amino carbene (CAAC)‐containing ruthenium benzylidenes in the production of terminal olefins. A straightforward synthesis of bis(CAAC)Ru indenylidene complexes, which are highly effective in the formation of both terminal and internal C=C bonds at loadings as low as 1 ppm, is now reported. 相似文献
9.
Wenlong Yang Kelsie E. Krantz Lucas A. Freeman Diane A. Dickie Andrew Molino Gernot Frenking Sudip Pan David J. D. Wilson Robert J. Gilliard 《Angewandte Chemie (International ed. in English)》2020,59(10):3850-3854
N‐Heterocyclic carbene (NHC)‐ and cyclic (alkyl)(amino)carbene (CAAC)‐stabilized borafluorene radicals have been isolated and characterized by elemental analysis, single‐crystal X‐ray diffraction, UV/Vis absorption, cyclic voltammetry (CV), electron paramagnetic resonance (EPR) spectroscopy, and theoretical studies. Both the CAAC–borafluorene radical ( 2 ) and the NHC–borafluorene radical ( 4 ) have a considerable amount of spin density localized on the boron atoms (0.322 for 2 and 0.369 for 4 ). In compound 2 , the unpaired electron is also partly delocalized over the CAAC ligand carbeneC and N atoms. However, the unpaired electron in compound 4 mainly resides throughout the borafluorene π‐system, with significantly less delocalization over the NHC ligand. These results highlight the Lewis base dependent electrostructural tuning of materials‐relevant radicals. Notably, this is the first report of crystalline borafluorene radicals, and these species exhibit remarkable solid‐state and solution stability. 相似文献
10.
Dr. James T. Goettel Haopeng Gao Simon Dotzauer Prof. Dr. Holger Braunschweig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(5):1136-1143
A cyclic (alkyl)(amino)carbene (CAAC) has been shown to react with a covalent azide similar to the Staudinger reaction. The reaction of MeCAAC with trimethylsilyl azide afforded the N-silylated 2-iminopyrrolidine (MeCAAC=NSiMe3), which was fully characterized. This compound undergoes hydrolysis to afford the 2-iminopyrrolidine and trimethylsiloxane which co-crystallize as a hydrogen-bonded adduct. The N-silylated 2-iminopyrrolidine was used to transfer the novel pyrrolidine-2-iminato ligand onto both main-group and transition-metal centers. The reaction of the tetrabromodiborane bis(dimethyl sulfide) adduct with two equivalents of MeCAAC=NSiMe3 afforded the disubstituted diborane. The reaction of MeCAAC=NSiMe3 with TiCl4 and CpTiCl3 afforded MeCAAC=NTiCl3 and MeCAAC=NTiCl2Cp, respectively. 相似文献
11.
The Synthesis of B2(SIDip)2 and its Reactivity Between the Diboracumulenic and Diborynic Extremes 下载免费PDF全文
Julian Bhnke Holger Braunschweig Theresa Dellermann William C. Ewing Kai Hammond J. Oscar C. Jimenez‐Halla Thomas Kramer Jan Mies 《Angewandte Chemie (International ed. in English)》2015,54(46):13801-13805
A new compound with the formula L‐B2‐L wherein the stabilizing ligand (L) is 1,3‐bis[diisopropylphenyl]‐4,5‐dihydroimidazol‐2‐ylidene (SIDip) has been synthesized, isolated, and characterized. The π‐acidity of the SIDip ligand, intermediate between the relatively non‐acidic IDip (1,3‐bis[diisopropylphenyl]imidazol‐2‐ylidene) ligand and the much more highly acidic CAAC (1‐[2,6‐diisopropylphenyl]‐3,3,5,5‐tetramethylpyrrolidin‐2‐ylidene) ligand, gives rise to a compound with spectroscopic, electrochemical, and structural properties between those of L‐B2‐L compounds stabilized by CAAC and IDip. Reactions of all three L‐B2‐L compounds with CO demonstrate the differences caused by their respective ligands, as the π‐acidities of the CAAC and SIDip carbenes enabled the isolation of bis(boraketene) compounds (L(OC)B‐B(CO)L), which could not be isolated from reactions with B2(IDip)2. However, only B2(IDip)2 and B2(SIDip)2 could be converted into bicyclic bis(boralactone) compounds. 相似文献
12.
Synthesis and Reactivity of a CAAC–Aminoborylene Adduct: A Hetero‐Allene or an Organoboron Isoelectronic with Singlet Carbenes 下载免费PDF全文
Fatme Dahcheh Dr. David Martin Prof. Dr. Douglas W. Stephan Prof. Dr. Guy Bertrand 《Angewandte Chemie (International ed. in English)》2014,53(48):13159-13163
A one‐electron reduction of a cyclic (alkyl)(amino)carbene (CAAC)–bis(trimethylsilyl)aminodichloroborane adduct leads to a stable aminoboryl radical. A second one‐electron reduction gives rise to a CAAC–aminoborylene adduct, which features an allenic structure. However, in manner similar to that of stable electrophilic singlet carbenes, this compound activates small molecules, such as CO and H2. 相似文献
13.
Fatme Dahcheh Prof. Dr. Douglas W. Stephan Prof. Dr. Guy Bertrand 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):199-204
The reaction of a cyclic (alkyl)(amino)carbene (CAAC) with dichloro‐ and dibromobis(trimethylsilyl)aminoborane results in the formation of haloiminoborane–CAAC adducts. When the iodo analogue is used, an oxidative addition at the carbene center affords a cationic iminoboryl–CAAC adduct, featuring a boron–nitrogen triple bond. Similar salts are also obtained by halide abstraction from the chloro‐ and bromoiminoborane–CAAC adducts. The reactivity of all of these compounds towards CO2 is discussed. 相似文献
14.
Isolation of a Neutral Boron‐Containing Radical Stabilized by a Cyclic (Alkyl)(Amino)Carbene 下载免费PDF全文
Dr. Philipp Bissinger Prof. Dr. Holger Braunschweig Dr. Alexander Damme Dr. Ivo Krummenacher Dr. Ashwini K. Phukan Dr. Krzysztof Radacki Shun Sugawara 《Angewandte Chemie (International ed. in English)》2014,53(28):7360-7363
Utilizing a cyclic (alkyl)(amino)carbene (CAAC) as a ligand, neutral CAAC‐stabilized radicals containing a boryl functionality could be prepared by reduction of the corresponding haloborane adducts. The radical species with a duryl substituent was fully characterized by single‐crystal X‐ray structural analysis, EPR spectroscopy, and DFT calculations. Compared to known neutral boryl radicals, the isolated radical species showed larger spin density on the boron atom. Furthermore, the compound that was isolated is extraordinarily stable to high temperatures under inert conditions, both in solution and in the solid state. Electrochemical investigations of the radical suggest the possibility to generate a stable formal boryl anion species. 相似文献
15.
Dr. Gaël Ung Jonathan Rittle Dr. Michele Soleilhavoup Prof. Guy Bertrand Prof. Jonas C. Peters 《Angewandte Chemie (International ed. in English)》2014,53(32):8427-8431
The CAAC [CAAC=cyclic (alkyl)(amino)carbene] family of carbene ligands have shown promise in stabilizing unusually low‐coordination number transition‐metal complexes in low formal oxidation states. Here we extend this narrative by demonstrating their utility in affording access to the first examples of two‐coordinate formal Fe0 and Co0 [(CAAC)2M] complexes, prepared by reduction of their corresponding two‐coordinate cationic FeI and CoI precursors. The stability of these species arises from the strong σ‐donating and π‐accepting properties of the supporting CAAC ligands, in addition to steric protection. 相似文献
16.
Celik MA Sure R Klein S Kinjo R Bertrand G Frenking G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(18):5676-5692
Quantum chemical calculations using DFT (BP86, M05-2X) and ab initio methods (CCSD(T), SCS-MP2) have been carried out on the borylene complexes (BH)L(2) and nitrogen cation complexes (N(+))L(2) with the ligands L=CO, N(2), PPh(3), NHC(Me), CAAC, and CAAC(model). The results are compared with those obtained for the isoelectronic carbones CL(2). The geometries and bond dissociation energies of the ligands, the proton affinities, and adducts with the Lewis acids BH(3) and AuCl were calculated. The nature of the bonding has been analyzed with charge and energy partitioning methods. The calculated borylene complexes (BH)L(2) have trigonal planar coordinated boron atoms which possess rather short B-L bonds. The calculated bond dissociation energies (BDEs) of the ligands for complexes where L is a carbene (NHC or CAAC) are very large (D(e) =141.6-177.3 kcal mol(-1)) which suggest that such species might become isolated in a condensed phase. The borylene complexes (BH)(PPh(3))(2) and (BH)(CO)(2) have intermediate bond strengths (D(e) =90.1 and 92.6 kcal mol(-1)). Substituted homologues with bulky groups at boron which protect the boron atom from electrophilic attack might also be stable enough to become isolated. The BDE of (BH)(N(2))(2) is much smaller (D(e) =31.9 kcal mol(-1)), but could become observable in a low-temperature matrix. The proton affinities of the borylene complexes are very large, particularly for the bulky adducts with L=PPh(3), NHC(Me), CAAC(model) and CAAC and thus, they are superbases. All (BH)L(2) molecules bind strongly AuCl either η(1) (L=N(2), PPh(3), NHC(Me), CAAC) or η(2) (L=CO, CAAC(model)). The BDEs of H(3)B-(BH)L(2) adducts which possess a hitherto unknown boron→boron donor-acceptor bond are smaller than for the AuCl complexes. The strongest bonded BH(3) adduct that might be isolable is (BH)(PPh(3))(2)-BH(3) (D(e) =36.2 kcal mol(-1)). The analysis of the bonding situation reveals that (BH)-L(2) bonding comes mainly from the orbital interactions which has three major contributions, that is, the donation from the symmetric (σ) and antisymmetric (π(||)) combination of the ligand lone-pair orbitals into the vacant MOs of BH L→(BH)←L and the L←(BH)→L π backdonation from the boron lone-pair orbital. The nitrogen cation complexes (N(+))L(2) have strongly bent L-N-L geometries, in which the calculated bending angle varies between 113.9° (L=N(2)) and 146.9° (L=CAAC). The BDEs for (N(+))L(2) are much larger than those of the borylene complexes. The carbene ligands NHC and CAAC but also the phosphane ligands PPh(3) bind very strongly between D(e) =358.4 kcal mol(-1) (L=PPh(3)) and D(e) =412.5 kcal mol(-1) (L=CAAC(model)). The proton affinities (PA) of (N(+))L(2) are much smaller and they bind AuCl and BH(3) less strongly compared with (BH)L(2). However, the PAs (N(+))L(2) for complexes with bulky ligands L are still between 139.9 kcal mol(-1) (L=CAAC(model)) and 168.5 kcal mol(-1) (L=CAAC). The analysis of the (N(+))-L(2) bonding situation reveals that the binding interactions come mainly from the L→(N(+))←L donation while L←(N(+) )→L π backdonation is rather weak. 相似文献
17.
Jean-Charles Bruyere Dr. David Specklin Dr. Christophe Gourlaouen Dr. Rosita Lapenta Prof. Luis F. Veiros Prof. Alfonso Grassi Dr. Stefano Milione Prof. Laurent Ruhlmann Prof. Corinne Boudon Dr. Samuel Dagorne 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(34):8061-8069
The reactivity of ZnII dialkyl species ZnMe2 with a cyclic(alkyl)(amino)carbene, 1-[2,6-bis(1-methylethyl)phenyl]-3,3,5,5-tetramethyl-2-pyrrolidinylidene (CAAC, 1 ), was studied and extended to the preparation of robust CAAC-supported ZnII Lewis acidic organocations. CAAC adduct of ZnMe2 ( 2 ), formed from a 1:1 mixture of 1 and ZnMe2, is unstable at room temperature and readily undergoes a CAAC carbene insertion into the Zn−Me bond to produce the ZnX2-type species (CAAC-Me)ZnMe ( 3 ), a reactivity further supported by DFT calculations. Despite its limited stability, adduct 2 was cleanly ionized to robust two-coordinate (CAAC)ZnMe+ cation ( 5+ ) and derived into (CAAC)ZnC6F5+ ( 7+ ), both isolated as B(C6F5)4− salts, showing the ability of CAAC for the stabilization of reactive [ZnMe]+ and [ZnC6F5]+ moieties. Due to the lability of the CAAC−ZnMe2 bond, the formation of bis(CAAC) adduct (CAAC)2ZnMe+ cation ( 6+ ) was also observed and the corresponding salt [ 6 ][B(C6F5)4] was structurally characterized. As estimated from experimental and calculations data, cations 5+ and 7+ are highly Lewis acidic species and the stronger Lewis acid 7+ effectively mediates alkene, alkyne and CO2 hydrosilylation catalysis. All supporting data hints at Lewis acid type activation–functionalization processes. Despite a lower energy LUMO in 5+ and 7+ , their observed reactivity is comparable to those of N-heterocyclic carbene (NHC) analogues, in line with charge-controlled reactions for carbene-stabilized ZnII organocations. 相似文献
18.
Yajuan Liu Pengfei Gao Taiming Zhang Xianjun Zhu Mengmeng Zhang Muqing Chen Pingwu Du Guan‐Wu Wang Hengxing Ji Jinlong Yang Shangfeng Yang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(5):1493-1497
Two‐dimensional (2D) black phosphorus (BP) has a unique band structure, but it suffers from low ambient stability owing to its high reactivity to oxygen. Covalent functionalization has been demonstrated to passivate the reactive BP effectively, however the reported covalent functionalization methods are quite limited to aryl diazonium and nucleophilic additions affording P?C and P?O?C single bonds, for which the retaining of one unpaired electron in the Group 15 phosphorus atom hampers the passivation effect. Now, covalent azide functionalization of BP nanosheets (BPNSs) is reported, leading to significant enhancement of the ambient stability of BP as confirmed by UV/Vis spectroscopic studies. The most stable configuration of the azide functionalized BPNSs (f‐BPNSs) is predicted by theoretical calculations, featuring the grafting of benzoic acid moiety onto BPNSs via the unprecedented P=N double bonds formed through in situ nitrene as a reactive intermediate. 相似文献
19.
Air‐Stable (CAAC)CuCl and (CAAC)CuBH4 Complexes as Catalysts for the Hydrolytic Dehydrogenation of BH3NH3 下载免费PDF全文
Dr. Xingbang Hu Dr. Michèle Soleilhavoup Dr. Mohand Melaimi Dr. Jiaxiang Chu Prof. Guy Bertrand 《Angewandte Chemie (International ed. in English)》2015,54(20):6008-6011
The first stable copper borohydride complex [(CAAC)CuBH4] [CAAC=cyclic(alkyl)(amino)carbene] bearing a single monodentate ligand was prepared by addition of NaBH4 or BH3NH3 to the corresponding [(CAAC)CuCl] complex. Both complexes are air‐stable and promote the catalytic hydrolytic dehydrogenation of ammonia borane. The amount of hydrogen released reaches 2.8 H2/BH3NH3 with a turnover frequency of 8400 mol molcat?1 h?1 at 25 °C. In a fifteen‐cycle experiment, the catalyst was reused without any loss of efficiency. 相似文献
20.
Liu Leo Liu Levy L. Cao Jiliang Zhou Douglas W. Stephan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(1):279-283
The reactions of the cyclic alkyl amino carbene (CAAC) 1 with phosphaalkynes generate the kinetically unstable CAAC‐derived phosphirenes 4 and 5 , which undergo rearrangement/dimerization reactions to give the vinyl‐substituted diphosphenes 2 , 3 , and 6 . The P=P double bond scission of 2 or 3 is unprecedentedly effected by S8, [AuCl(tht)], or MeOTf at room temperature, which affords a dithiophosphorane 7 , a phosphepine Au complex 8 , or phosphepinium cations 9 and 10 , respectively. The cationic species feature little homoaromaticity while representing the first examples of the phosphorus‐containing analogue of the tropylium ion. 相似文献