共查询到20条相似文献,搜索用时 31 毫秒
1.
Heather C. Johnson Andrew S. Weller 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(35):10311-10315
{Rh(xantphos)}‐based phosphido dimers form by P C activation of xantphos (4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene) in the presence of amine–boranes. These dimers are active dehydrocoupling catalysts, forming polymeric [H2BNMeH]n from H3B⋅NMeH2 and dimeric [H2BNMe2]2 from H3B⋅NMe2H at low catalyst loadings (0.1 mol %). Mechanistic investigations support a dimeric active species, suggesting that bimetallic catalysis may be possible in amine–borane dehydropolymerization. 相似文献
2.
Stevens CJ Dallanegra R Chaplin AB Weller AS Macgregor SA Ward B McKay D Alcaraz G Sabo-Etienne S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(10):3011-3020
The IrIII fragment {Ir(PCy3)2(H)2}+ has been used to probe the role of the metal centre in the catalytic dehydrocoupling of H3B?NMe2H ( A ) to ultimately give dimeric aminoborane [H2BNMe2]2 ( D ). Addition of A to [Ir(PCy3)2(H)2(H2)2][BArF4] ( 1 ; ArF=(C6H3(CF3)2), gives the amine‐borane complex [Ir(PCy3)2(H)2(H3B?NMe2H)][BArF4] ( 2 a ), which slowly dehydrogenates to afford the aminoborane complex [Ir(PCy3)2(H)2(H2B? NMe2)][BArF4] ( 3 ). DFT calculations have been used to probe the mechanism of dehydrogenation and show a pathway featuring sequential BH activation/H2 loss/NH activation. Addition of D to 1 results in retrodimerisation of D to afford 3 . DFT calculations indicate that this involves metal trapping of the monomer–dimer equilibrium, 2 H2BNMe2 ? [H2BNMe2]2. Ruthenium and rhodium analogues also promote this reaction. Addition of MeCN to 3 affords [Ir(PCy3)2(H)2(NCMe)2][BArF4] ( 6 ) liberating H2B? NMe2 ( B ), which then dimerises to give D . This is shown to be a second‐order process. It also allows on‐ and off‐metal coupling processes to be probed. Addition of MeCN to 3 followed by A gives D with no amine‐borane intermediates observed. Addition of A to 3 results in the formation of significant amounts of oligomeric H3B?NMe2BH2?NMe2H ( C ), which ultimately was converted to D . These results indicate that the metal is involved in both the dehydrogenation of A , to give B , and the oligomerisation reaction to afford C . A mechanism is suggested for this latter process. The reactivity of oligomer C with the Ir complexes is also reported. Addition of excess C to 1 promotes its transformation into D , with 3 observed as the final organometallic product, suggesting a B? N bond cleavage mechanism. Complex 6 does not react with C , but in combination with B oligomer C is consumed to eventually give D , suggesting an additional role for free aminoborane in the formation of D from C . 相似文献
3.
M. Sc. Christoph Schiwek Dr. Jenni Meiners M. Sc. Moritz Förster Dr. Christian Würtele Dr. Martin Diefenbach Prof. Dr. Max C. Holthausen Prof. Dr. Sven Schneider 《Angewandte Chemie (International ed. in English)》2015,54(50):15271-15275
The iridium dihydride [Ir(H)2(HPNP)]+ (PNP=N(CH2CH2PtBu2)2) reacts with O2 to give the unusual, square‐planar iridium(III) hydroxide [Ir(OH)(PNP)]+ and water. Regeneration of the dihydride with H2 closes a quasi‐catalytic synthetic oxygen‐reduction reaction (ORR) cycle that can be run several times. Experimental and computational examinations are in agreement with an oxygenation mechanism via rate‐limiting O2 coordination followed by H‐transfer at a single metal site, facilitated by the cooperating pincer ligand. Hence, the four electrons required for the ORR are stored within the two covalent M? H bonds of a mononuclear metal complex. 相似文献
4.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(13):3753-3756
The first single‐component N‐heterocyclic silylene borane 1 (LSi‐R‐BMes2; L=PhC(Nt Bu)2; R=1,12‐xanthendiyl spacer; Mes=2,4,6‐Me3C6H2), acting as a frustrated Lewis pair (FLP) in small‐molecule activation, can be synthesized in 65 % yields. Its HOMO is largely localized at the silicon(II) atom and the LUMO has mainly boron 2p character. In small‐molecule activation 1 allows access to the intramolecular silanone–borane 3 featuring a Si=O→B interaction through reaction with O2, N2O, or CO2, and formation of silanethione borane 4 from reaction with S8. The SiII center in 1 undergoes immediate hydrogenation if exposed to H2 at 1 atm pressure in benzene, affording the silane borane 5‐H2 , L(H2)Si‐R‐BMes2. Remarkably, no H2 activation occurs if the single silylene LSiPh and Mes3B intermolecularly separated are exposed to dihydrogen. Unexpectedly, the pre‐organized Si–B separation in 1 enables a metal‐free dehydrogenation of H2O to give the silanone–borane 3 as reactive intermediate. 相似文献
5.
《Angewandte Chemie (International ed. in English)》2017,56(13):3699-3702
The first single‐component N‐heterocyclic silylene borane 1 (LSi‐R‐BMes2; L=PhC(Nt Bu)2; R=1,12‐xanthendiyl spacer; Mes=2,4,6‐Me3C6H2), acting as a frustrated Lewis pair (FLP) in small‐molecule activation, can be synthesized in 65 % yields. Its HOMO is largely localized at the silicon(II) atom and the LUMO has mainly boron 2p character. In small‐molecule activation 1 allows access to the intramolecular silanone–borane 3 featuring a Si=O→B interaction through reaction with O2, N2O, or CO2, and formation of silanethione borane 4 from reaction with S8. The SiII center in 1 undergoes immediate hydrogenation if exposed to H2 at 1 atm pressure in benzene, affording the silane borane 5‐H2 , L(H2)Si‐R‐BMes2. Remarkably, no H2 activation occurs if the single silylene LSiPh and Mes3B intermolecularly separated are exposed to dihydrogen. Unexpectedly, the pre‐organized Si–B separation in 1 enables a metal‐free dehydrogenation of H2O to give the silanone–borane 3 as reactive intermediate. 相似文献
6.
Prof. Dr. Holger Braunschweig Katharina Kraft Thomas Kupfer Eva Siedler 《无机化学与普通化学杂志》2010,636(15):2565-2567
The hydride complex K[(η5‐C5H5)Mn(CO)2H] reacted with a range of dihalo(organyl)boranes X2BR (X = Cl, Br; R = tBu,Mes, Ferrocenyl) to give the corresponding borane complexes[(η5‐C5H5)Mn(CO)2(HB(X)R)]., The presence of a hydride in bridging position between manganese and boron was deduced from 11B decoupled 1H NMR spectra. Additionally, the structure of the tert‐butyl borane complex was confirmed by single‐crystal X‐ray diffraction. 相似文献
7.
The Simplest Amino‐borane H2B=NH2 Trapped on a Rhodium Dimer: Pre‐Catalysts for Amine–Borane Dehydropolymerization
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Amit Kumar Nicholas A. Beattie Dr. Sebastian D. Pike Prof. Stuart A. Macgregor Prof. Andrew S. Weller 《Angewandte Chemie (International ed. in English)》2016,55(23):6651-6656
The μ‐amino–borane complexes [Rh2(LR)2(μ‐H)(μ‐H2B=NHR′)][BArF4] (LR=R2P(CH2)3PR2; R=Ph, iPr; R′=H, Me) form by addition of H3B?NMeR′H2 to [Rh(LR)(η6‐C6H5F)][BArF4]. DFT calculations demonstrate that the amino–borane interacts with the Rh centers through strong Rh‐H and Rh‐B interactions. Mechanistic investigations show that these dimers can form by a boronium‐mediated route, and are pre‐catalysts for amine‐borane dehydropolymerization, suggesting a possible role for bimetallic motifs in catalysis. 相似文献
8.
Dr. Lei Zhang Takumi Oishi Liuzhou Gao Shiyu Hu Linlin Yang Prof. Dr. Wei Li Shengjun Wu Prof. Dr. Rong Shang Prof. Dr. Yohsuke Yamamoto Prof. Dr. Shuhua Li Prof. Dr. Wei Wang Prof. Dr. Guxiang Zeng 《Chemphyschem》2020,21(23):2573-2578
A new efficient metal-based frustrated Lewis pair constructed by (PtBu3)2Pt and B(C6F5)3 was designed through density functional theory calculations for the catalytic dehydrogenation of ammonia borane (AB). The reaction was composed by the successive dehydrogenation of AB and H2 liberation, which occurs through the cooperative functions of the Pt(0) center and the B(C6F5)3 moiety. Two equivalents of H2 were predicted to be liberated from each AB molecule. The generation of the second H2 is the rate-determining step, with a Gibbs energy barrier and reaction energy of 27.4 and 12.8 kcal/mol, respectively. 相似文献
9.
Nikolaus Gorgas Berthold Stger Luis F. Veiros Karl Kirchner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(39):14012-14017
Herein, we report on the first synthesis and structural characterization of the iron based aminoborane complexes [Fe(PNP)(H)(η2:η2‐H2B=NR2)]+ (R=H, Me). These species are formed upon protonation of the borohydride complex [Fe(PNP)(H)(η2‐BH4)] by ammonium salts [NH2R2]+ (R=H, Me). For R=Me, the reaction proceeds via the cationic dinuclear intermediate [{Fe(PNP)(H)}2(μ2,η2:η2‐BH4)]+. A mechanism for the reaction is proposed based on DFT calculations that also indicate the final aminoborane complex as the thermodynamic product. All complexes were characterized by NMR spectroscopy, HRMS, and X‐ray crystallography. 相似文献
10.
Richard Böser Lars Denker Dr. René Frank 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(45):10575-10579
Benzyl-substituted boronates and borates are widely employed as mild sources in radical or anionic transfer reactions of benzyl entities. In this process the B−C bond to the benzyl moiety is essentially ruptured. In contrast, reactions with retention of the B−C bond are poorly investigated although several other reactive sites in benzyl–boron systems are clearly inherent. In this respect, the novel reactivity of the representative borane adduct IiPr−BH2Bn [IiPr=:C{N(iPr)CH}2, Bn=CH2C6H5] is demonstrated. Dihalogenation of the BH2 entity is observed with BCl3 and BBr3, whereas BI3 either affords IiPr−BHI2 or proceeds with borylation of the aromatic phenyl ring to give a hydride-bridged bisborylated species. The photochemical mono- and dihalogenation of the benzylic CH2 group was demonstrated with elemental bromine Br2. The brominated product IiPr−BBr2−CHBr−C6H5 was borylated at the benzylic carbon atom in an umpolung event with BI3 to afford the zwitterion IiPr−BI−CH(BI3)−C6H5. 相似文献
11.
PC‐Activated Bimetallic Rhodium Xantphos Complexes: Formation and Catalytic Dehydrocoupling of Amine–Boranes
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Heather C. Johnson Prof. Andrew S. Weller 《Angewandte Chemie (International ed. in English)》2015,54(35):10173-10177
{Rh(xantphos)}‐based phosphido dimers form by P? C activation of xantphos (4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene) in the presence of amine–boranes. These dimers are active dehydrocoupling catalysts, forming polymeric [H2BNMeH]n from H3B?NMeH2 and dimeric [H2BNMe2]2 from H3B?NMe2H at low catalyst loadings (0.1 mol %). Mechanistic investigations support a dimeric active species, suggesting that bimetallic catalysis may be possible in amine–borane dehydropolymerization. 相似文献
12.
Frédéric Pelletier Dr. Diana Ciuculescu Jean‐Gabriel Mattei Dr. Pierre Lecante Dr. Marie‐José Casanove Dr. Nader Yaacoub Dr. Jean‐Marc Greneche Dr. Carolin Schmitz‐Antoniak Prof. Catherine Amiens 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(19):6021-6026
The effectiveness of amine–borane as reducing agent for the synthesis of iron nanoparticles has been investigated. Large (2–4 nm) Fe nanoparticles were obtained from [Fe{N(SiMe3)2}2]. Inclusion of boron in the nanoparticles is clearly evidenced by extended X‐ray absorption fine structure spectroscopy and Mössbauer spectrometry. Furthermore, the reactivity of amine–borane and amino–borane complexes in the presence of pure Fe nanoparticles has been investigated. Dihydrogen evolution was observed in both cases, which suggests the potential of Fe nanoparticles to promote the release of dihydrogen from amine–borane and amino–borane moieties. 相似文献
13.
An Ethylene‐Bridged Phosphane/Borane Frustrated Lewis Pair Featuring the ‐B(Fxyl)2 Lewis Acid Component
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Long Wang Kamil Samigullin Prof. Dr. Matthias Wagner Dr. Alison C. McQuilken Prof. Dr. Timothy H. Warren Dr. Constantin G. Daniliuc Dr. Gerald Kehr Prof. Dr. Gerhard Erker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):11015-11021
Hydroboration of dimesitylvinylphosphane with bis[3,5‐bis(trifluoromethyl)phenyl]borane [HB(Fxyl)2] gave the intramolecular ethylene‐bridged P/B frustrated Lewis pair (FLP) Mes2PCH2CH2B(Fxyl)2. The new compound underwent a variety of typical FLP reactions such as P/B‐addition to the carbonyl group of p‐chloro‐benzaldehyde. Cooperative N,N‐addition to nitric oxide gave the respective persistent P/B FLPNO. radical, which readily reacted with 1,4‐cyclohexadiene by H‐atom abstraction to yield the corresponding P/B FLPNOH product. The B(Fxyl)2‐containing FLP reacted as a template for the HB(C6F5)2 reduction of carbon monoxide to the formyl stage to give the respective FLP(η2‐formylborane) product. Most products were characterized by single‐crystal X‐ray crystal structure analysis. 相似文献
14.
Dr. Annie L. Colebatch Prof. Dr. Andrew S. Weller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1379-1390
The dehydropolymerization of amine–boranes, exemplified as H2RB⋅NR′H2, to produce polyaminoboranes (HRBNR′H)n that are inorganic analogues of polyolefins with alternating main-chain B−N units, is an area with significant potential, stemming from both fundamental (mechanism, catalyst development, main-group hetero-cross-coupling) and technological (new polymeric materials) opportunities. This Concept article outlines recent advances in the field, covering catalyst development and performance, current mechanistic models, and alternative non-catalytic routes for polymer production. The substrate scope, polymer properties and applications of these exciting materials are also outlined. Challenges and opportunities in the field are suggested, as a way of providing focus for future investigations. 相似文献
15.
Dr. Daniel Bůžek Dr. Karel Škoch Soňa Ondrušová Dr. Matouš Kloda Dr. Dmytro Bavol Andrii Mahun Dr. Libor Kobera Dr. Kamil Lang Dr. Michael G. S. Londesborough Dr. Jan Demel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(67):e202201885
The unprecedented co-thermolysis of decaborane(14) (nido-B10H14) and toluene results in a novel porous material (that we have named “activated borane”) containing micropores between 1.0 and 1.5 nm in diameter and a specific surface area of 774 m2 g−1 (Ar, 87 K) that is thermally stable up to 1000 °C. Solid state 1H, 11B and 13C MAS NMR, UV-vis and IR spectroscopies suggest an amorphous structure of borane clusters interconnected by toluene moieties in a ratio of about three toluene molecules for every borane cluster. In addition, the structure contains Lewis-acidic tri-coordinated boron sites giving it some unique properties. Activated borane displays high sorption capacity for pollutants such as sulfamethoxazole, tramadol, diclofenac and bisphenol A that exceed the capacity of commercially-available activated carbon. The consistency in properties for each batch made, and the ease of its synthesis, make activated borane a promising porous material worthy of broad attention. 相似文献
16.
A Germylene/Borane Lewis Pair and the Remarkable C=O Bond Cleavage Reaction toward Isocyanate and Ketone Molecules
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jiancheng Li Bin Li Rui Liu Liuyin Jiang Prof. Dr. Hongping Zhu Prof. Dr. Herbert W. Roesky Sayan Dutta Dr. Debasis Koley Prof. Weiping Liu Qingsong Ye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14499-14503
A germylene/borane Lewis pair ( 2 ) was prepared from a 1,1‐carboboration of amidinato phenylethynylgermylene ( 1 ) by B(C6F5)3. Compound 2 reacted with iPrNCO and (4‐MeOC6H4)C(O)Me, respectively, with cleavage of the C=O double bond. In the first instance, O and iPrNC insert separately into the Ge?B bond to yield a GeBC2O‐heterocycle ( 3 ) and a GeBC3‐heterocycle ( 4 ). In the second case (4‐MeOC6H4)(Me)C inserts into the Ge?N bond of 2 while O is incorporated in the Ge?B bond to form a Ge‐centered spiroheterocycle ( 5 ). The reaction of 2 with tBuNC to give 6 , which has almost the same structure as 4 , proved the formation of the isonitrile during transformation from 2 and iPrNCO to 3 and 4 . The kinetic study of the reaction of 2 and iPrNCO gave evidence of proceeding through a GeBC3O‐heterocycle intermediate. In addition, a DFT study was performed to elucidate the reaction mechanism. 相似文献
17.
Phosphoramidate‐Supported Cp*IrIII Aminoborane H2B=NR2 Complexes: Synthesis,Structure, and Solution Dynamics
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Marcus W. Drover Eric G. Bowes Prof. Dr. Laurel L. Schafer Prof. Dr. Jennifer A. Love Prof. Dr. Andrew S. Weller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(20):6793-6797
Reaction of aminoboranes H2B=NR2 (R=iPr or Cy) with the cationic Cp*IrIII phosphoramidate complex [IrCp*{κ2‐N,O‐Xyl(N)P(O)(OEt)2}][BArF4] generates the aminoborane complexes [IrCp*(H){κ1‐N‐η2‐HB‐Xyl(N)P(OBHNR2)(OEt)2}][BArF4] (R=iPr or Cy) in which coordination of a P=O bond with boron weakens the B=N multiple bond. For these complexes, solution‐ and solid‐state, as well as DFT computational techniques, have been employed to substantiate B?N bond rotation of the coordinated aminoborane. 相似文献
18.
Platinum Complexes of a Borane‐Appended Analogue of 1,1′‐Bis(diphenylphosphino)ferrocene: Flexible Borane Coordination Modes and in situ Vinylborane Formation
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bradley E. Cowie Prof. David J. H. Emslie 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):16899-16912
A bis(phosphine)borane ambiphilic ligand, [Fe(η5‐C5H4PPh2)(η5‐C5H4PtBu{C6H4(BPh2)‐ortho})] (FcPPB), in which the borane occupies a terminal position, was prepared. Reaction of FcPPB with tris(norbornene)platinum(0) provided [Pt(FcPPB)] ( 1 ) in which the arylborane is η3BCC‐coordinated. Subsequent reaction with CO and CNXyl (Xyl=2,6‐dimethylphenyl) afforded [PtL(FcPPB)] {L=CO ( 2 ) and CNXyl ( 3 )} featuring η2BC‐ and η1B‐arylborane coordination modes, respectively. Reaction of 1 or 2 with H2 yielded [PtH(μ‐H)(FcPPB)] in which the borane is bound to a hydride ligand on platinum. Addition of PhC2H to [Pt(FcPPB)] afforded [Pt(C2Ph)(μ‐H)(FcPPB)] ( 5 ), which rapidly converted to [Pt(FcPPB′)] ( 6 ; FcPPB′=[Fe(η5‐C5H4PPh2)(η5‐C5H4PtBu{C6H4(BPh‐CPh=CHPh‐Z)‐ortho}]) in which the newly formed vinylborane is η3BCC‐coordinated. Unlike arylborane complex 1 , vinylborane complex 6 does not react with CO, CNXyl, H2 or HC2Ph at room temperature. 相似文献
19.
Borane Adducts of Hydrazoic Acid and Organic Azides: Intermediates for the Formation of Aminoboranes
Kevin Blsing Jonas Bresien Ren Labbow Dirk Michalik Axel Schulz Max Thomas Alexander Villinger 《Angewandte Chemie (International ed. in English)》2019,58(20):6540-6544
The reaction of HN3 with the strong Lewis acid B(C6F5)3 led to the formation of a very labile HN3?B(C6F5)3 adduct, which decomposed to an aminoborane, H(C6F5)NB(C6F5)2, above ?20 °C with release of molecular nitrogen and simultaneous migration of a C6F5 group from boron to the nitrogen atom. The intermediary formation of azide–borane adducts with B(C6F5)3 was also demonstrated for a series of organic azides, RN3 (R=Me3Si, Ph, 3,5‐(CF3)2C6H3), which also underwent Staudinger‐like decomposition along with C6F5 group migration. In accord with experiment, computations revealed rather small barriers towards nitrogen release for these highly labile azide adducts for all organic substituents except R=Me3Si (m.p. 120 °C, Tdec=189 °C). Hydrolysis of the aminoboranes provided C6F5‐substituted amines, HN(R)(C6F5), in good yields. 相似文献
20.
Dr. Masahiro Kamitani Balazs Pinter Dr. Chun‐Hsing Chen Dr. Maren Pink Prof. Dr. Daniel J. Mindiola 《Angewandte Chemie (International ed. in English)》2014,53(41):10913-10915
The dimethyl aryloxide complexes [(PNP)M(CH3)2(OAr)] (M=Zr or Hf; PNP?=N[2‐P(CHMe2)2‐4‐methylphenyl]2); Ar=2,6‐iPr2C6H3), which were readily prepared from [(PNP)M(CH3)3] by alcoholysis with HOAr, undergo photolytically induced α‐hydrogen abstraction to cleanly produce complexes [(PNP)M=CH2(OAr)] with terminal methylidene ligands. These unique systems have been fully characterized, including the determination of a solid‐state structure in the case of M=Zr. 相似文献