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1.
Ab Initio Molecular Dynamics Study of Hydrogen Cleavage by a Lewis Base [tBu3P] and a Lewis Acid [B(C6F5)3] at the Mesoscopic Level—Dynamics in the Solute–Solvent Molecular Clusters
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With the help of state‐of‐the‐art ab initio molecular dynamics methods, we investigated the reaction pathway of the {tBu3P + H2 + B(C6F5)3} system at the mesoscopic level. It is shown that: i) the onset of H2 activation is at much larger boron???phosphorus distances than previously thought; ii) the system evolves to the product in a roaming‐like fashion because of quasi‐periodic nuclear motion along the asymmetric normal mode of P???H?H???B fragment; iii) transient configurations of a certain type are present despite structural interference from the solvent; iv) transient‐state configurations with sub‐picosecond lifetime have potentially interesting infrared activity in the organic solvent (toluene) as well as in the gas phase. The presented results should be helpful for future experimental and theoretical studies of frustrated Lewis pair (FLP) activity. 相似文献
2.
Dr. Bao‐Hua Xu Raul Alfonso Adler Yanez Hiroshi Nakatsuka Prof. Dr. Masato Kitamura Dr. Gerald Kehr Prof. Dr. Gerhard Erker 《化学:亚洲杂志》2012,7(6):1347-1356
The frustrated Lewis pair (FLP) Mes2PCH2CH2B(C6F5)2 ( 1 ) reacts with an enolizable conjugated ynone by 1,4‐addition involving enolate tautomerization to give an eight‐membered zwitterionic heterocycle. The conjugated endione PhCO‐CH?CH‐COPh reacts with the intermolecular FLP tBu3P/B(C6F5)3 by a simple 1,4‐addition to an enone subunit. The same substrate undergoes a more complex reaction with the FLP 1 that involves internal acetal formation to give a heterobicyclic zwitterionic product. FLP 1 reacts with dimethyl maleate by selective overall addition to the C?C double bond to give a six‐membered heterocycle. It adds analogously to the triple bond of an acetylenic ester to give a similarly structured six‐membered heterocycle. The intermolecular FLP P(o‐tolyl)3/B(C6F5)3 reacts analogously with acetylenic ester by trans‐addition to the carbon–carbon triple bond. An excess of the intermolecular FLP tBu3P/B(C6F5)3, which contains a more nucleophilic phosphane, reacts differently with acetylenic ester examples, namely by O? C(alkyl) bond cleavage to give the {R‐CO2[B(C6F5)3]2?}[alkyl‐PtBu3+] salts. Simple aryl or alkyl esters react analogously by using the borane‐stabilized carboxylates as good leaving groups. All essential products were characterized by X‐ray diffraction. 相似文献
3.
The phosphine tBu2PC?CH ( 1 ) was reacted with B(C6F5) to give the zwitterionic species tBu2P(H)C?CB(C6F5)3 ( 2 ). The analogous species tBu2P(Me)C?CB(C6F5)3 ( 3 ), tBu2P(H)C?CB(Cl)(C6F5)2 ( 4 ), tBu2P(H)C?CB(H)(C6F5)2 ( 5 ), and tBu2P(Me)C?CB(H)(C6F5) 2 ( 6 ) were also prepared. The salt [tBu2P(H)C?CB(C6F5)2(THF)][B(C6F5)4] ( 7 ) was prepared through abstraction of hydride by [Ph3C][B(C6F5)4]. Species 5 reacted with the imine tBuN?CHPh to give the borane–amine adduct tBu2PC?CB[tBuN(H)CH2Ph](C6F5)2 ( 8 ). The related phosphine Mes2PC?CH ( 9 ; Mes=C6H2Me3) was used to prepare [tBu3PH][Mes2PC?CB(C6F5)3] ( 10 ) and generate Mes2PC?CB(C6F5)2. The adduct Mes2PC?CB(NCMe)(C6F5)2 ( 11 ) was isolated. Reaction of Mes2PC?CB(C6F5)2 with H2 gave the zwitterionic product (C6F5)2(H)BC(H)?C[P(H)Mes2][(C6F5)2BC?CP(H)Mes2] ( 12 ). Reaction of tBu2PC?CB(C6F5)2, a phosphine–borane generated in situ from 5 , with 1‐hexene gave the species [tBu2PC?CB(C6F5)2](CH2CHnBu)[tBu2PC?CB(C6F5)2] ( 13 ) and subsequent reaction with methanol or hexene resulted in the formation of [tBu2P(H)C?CB(C6F5)2](CH2CHnBu)[tBu2PC?CB(C6F5)2](OMe) ( 14 ) or the macrocycle {[tBu2PC?CB(C6F5)2](CH2CH2nBu)}2 ( 15 ), respectively. In a related fashion, the reaction of 13 with THF afforded the macrocycle [tBu2PC?CB(C6F5)2](CH2CHnBu)[tBu2PC?CB(C6F5)2][O(CH2)4] ( 16 ), although treatment of tBu2PC?CB(C6F5)2 with THF lead to the formation of {[tBu2PC?CB(C6F5)2][O(CH2)4]}2 ( 17 ). In a related example, the reaction of Mes2PC?CB(C6F5)2 with PhC?CH gave {[Mes2PC?CB(C6F5)2](CH?CPh)}2 ( 18 ). Compound 5 reacted with AlX3 (X=Cl, Br) to give addition to the alkynyl unit, affording (C6F5)2BC(H)?C[P(H)tBu2](AlX3) (X=Cl 19 , Br 20 ). In a similar fashion, 5 reacted with [Zn(C6F5)2] ? C7H8, [Al(C6F5)3] ? C7H8, or HB(C6F5)2 to give (C6F5)3BC(H)?C[P(H)tBu2][Zn(C6F5)] ( 21 ), (C6F5)3BC(H)?C[P(H)tBu2][Al(C6F5)2] ( 22 ), or [(C6F5)2B]2HC?CH[P(H)tBu2] ( 23 ), respectively. The implications of this reactivity are discussed. 相似文献
4.
Why Does the Intramolecular Trimethylene‐Bridged Frustrated Lewis Pair Mes2PCH2CH2CH2B(C6F5)2 Not Activate Dihydrogen?
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Thomas Özgün Dr. Ke‐Yin Ye Dr. Gerald Kehr Prof. Dr. Gerhard Erker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5988-5995
The methyl labelled C3‐bridged frustrated phosphane borane Lewis pair (P/B FLP) 2 b was prepared by treatment of Mes2PCl with a methallyl Grignard reagent followed by anti‐Markovnikov hydroboration with Piers’ borane [HB(C6F5)2)]. The FLP 2 b is inactive toward dihydrogen under typical ambient conditions, in contrast to the C2‐ and C4‐bridged FLP analogues. Dynamic NMR spectroscopy showed that this was not due to kinetically hindered P???B dissociation of 2 b . DFT calculations showed that the hydrogen‐splitting reaction of the parent compound 2 a is markedly endergonic. The PH+/BH? H2‐splitting product of 2 b was indirectly synthesized by a sequence of H+/H? addition. It lost H2 at ambient conditions and confirmed the result of the DFT analysis. 相似文献
5.
Damir Barisic David Schneider Ccilia Maichle‐Mssmer Reiner Anwander 《Angewandte Chemie (International ed. in English)》2019,58(5):1515-1518
The half‐open rare‐earth‐metal aluminabenzene complexes [(1‐Me‐3,5‐tBu2‐C5H3Al)(μ‐Me)Ln(2,4‐dtbp)] (Ln=Y, Lu) are accessible via a salt metathesis reaction employing Ln(AlMe4)3 and K(2,4‐dtbp). Treatment of the yttrium complex with B(C6F5)3 and tBuCCH gives access to the pentafluorophenylalane complex [{1‐(C6F5)‐3,5‐tBu2‐C5H3Al}{μ‐C6F5}Y{2,4‐dtbp}] and the mixed vinyl acetylide complex [(2,4‐dtbp)Y(μ‐η1:η3‐2,4‐tBu2‐C5H4)(μ‐CCtBu)AlMe2], respectively. 相似文献
6.
Estefanía Gioria Dr. Juan del Pozo Dr. Jesús M. Martínez‐Ilarduya Prof. Dr. Pablo Espinet 《Angewandte Chemie (International ed. in English)》2016,55(42):13276-13280
A Pd complex, cis‐[Pd(C6F5)2(THF)2] ( 1 ), is proposed as a useful touchstone for direct and simple experimental measurement of the relative ability of ancillary ligands to induce C?C coupling. Interestingly, 1 is also a good alternative to other precatalysts used to produce Pd0L. Complex 1 ranks the coupling ability of some popular ligands in the order PtBu3>o‐TolPEWO‐F≈tBuXPhos>P(C6F5)3≈PhPEWO‐F>P(o‐Tol)3≈THF≈tBuBrettPhos?Xantphos≈PhPEWO‐H?PPh3 according to their initial coupling rates, whereas their efficiency, depending on competitive hydrolysis, is ranked tBuXPhos≈PtBu3≈o‐TolPEWO‐F>PhPEWO‐F>P(C6F5)3?tBuBrettPhos>THF≈P(o‐Tol)3>Xantphos>PhPEWO‐H?PPh3. This “meter” also detects some other possible virtues or complications of ligands such as tBuXPhos or tBuBrettPhos. 相似文献
7.
Boron Lewis Acid‐Catalyzed Hydroboration of Alkenes with Pinacolborane: BArF3 Does What B(C6F5)3 Cannot Do!
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Dr. Qin Yin Dr. Hendrik F. T. Klare Prof. Dr. Martin Oestreich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(39):13840-13844
The transition‐metal‐free hydroboration of various alkenes with pinacolborane (HBpin) initiated by tris[3,5‐bis(trifluoromethyl)phenyl]borane (BArF3) is reported. The choice of the boron Lewis acid is crucial as the more prominent boron Lewis acid tris(pentafluorophenyl)borane (B(C6F5)3) is reluctant to react. Unlike B(C6F5)3, BArF3 is found to engage in substituent redistribution with HBpin, resulting in the formation of ArFBpin and the electron‐deficient diboranes [H2BArF]2 and [(ArF)(H)B(μ‐H)2BArF2]. These in situ‐generated hydroboranes undergo regioselective hydroboration of styrene derivatives as well as aliphatic alkenes with cis diastereoselectivity. Another ligand metathesis of these adducts with HBpin subsequently affords the corresponding HBpin‐derived anti‐Markovnikov adducts. The reactive hydroboranes are regenerated in this step, thereby closing the catalytic cycle. 相似文献
8.
Estefanía Gioria Juan delPozo Jesús M. Martínez‐Ilarduya Pablo Espinet 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(42):13470-13474
A Pd complex, cis‐[Pd(C6F5)2(THF)2] ( 1 ), is proposed as a useful touchstone for direct and simple experimental measurement of the relative ability of ancillary ligands to induce C−C coupling. Interestingly, 1 is also a good alternative to other precatalysts used to produce Pd0L. Complex 1 ranks the coupling ability of some popular ligands in the order PtBu3>o‐TolPEWO‐F≈tBuXPhos>P(C6F5)3≈PhPEWO‐F>P(o‐Tol)3≈THF≈tBuBrettPhos≫Xantphos≈PhPEWO‐H≫PPh3 according to their initial coupling rates, whereas their efficiency, depending on competitive hydrolysis, is ranked tBuXPhos≈PtBu3≈o‐TolPEWO‐F>PhPEWO‐F>P(C6F5)3≫tBuBrettPhos>THF≈P(o‐Tol)3>Xantphos>PhPEWO‐H≫PPh3. This “meter” also detects some other possible virtues or complications of ligands such as tBuXPhos or tBuBrettPhos. 相似文献
9.
Helmut Goesmann Eberhard Matern Jolanta Olkowska‐Oetzel Jerzy Pikies Gerhard Fritz 《无机化学与普通化学杂志》2001,627(6):1181-1184
Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XXIII. Reactions of tBu2P–P=P(Me)tBu2 with (Et3P)2NiCl2 and [{η2‐C2H4}Ni(PEt3)2] tBu2P–P=P(Me)tBu2 ( 1 ) forms with (Et3P)2NiCl2 ( 2 ) and Na(Nph) the [μ‐(1,3 : 2,3‐η‐tBu2P4tBu2){Ni(PEt3)Cl}2] ( 3 ) as main product. Using Na/Hg instead as reducing agent the Ni0 compounds [{η2‐tBu2P–P}Ni(PEt3)2] ( 4 ), [{η2‐tBu2P–P=P–PtBu2}Ni(PEt3)2] ( 5 ) and [(Et3P)Ni(μ‐PtBu2)]2 ( 6 ) with four‐membered Ni2P2 ring result. [{η2‐C2H4}Ni(PEt3)2] yields with 1 also 4 . The compounds were characterized by 1H and 31P{1H} NMR investigations and 3 also by a single crystal X‐ray analysis. It crystallizes triclinic in the space group P 1 with a = 1129.4(2), b = 1256.8(3), c = 1569.5(3) pm, α = 72.44(3)°, β = 70.52(3)° and γ = 74.20(3)°. 相似文献
10.
Stephen J. Geier Meghan A. Dureen Eva Y. Ouyang Douglas W. Stephan Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(3):988-993
By employing strategies based on frustrated Lewis pair chemistry, new routes to phosphino‐phosphonium cations and zwitterions have been developed. B(C6F5)3 is shown to react with H2 and P2tBu4 to effect heterolytic hydrogen activation yielding the phosphino‐phosphonium borate salt [(tBu2P)PHtBu2] [HB(C6F5)3] ( 1 ). Alternatively, alkenylphosphino‐phosphonium borate zwitterions are accessible by reaction of B(C6F5)3 and PhC?CH with P2Ph4, P4Cy4, or P5Ph5 affording the species [(Ph2P)P(Ph)2C(Ph)?C(H)B(C6F5)3] ( 2 ), [(P3Cy3)P(Cy)C(Ph)?C(H)B(C6F5)3] ( 3 ), and [(P4Ph4)P(Ph)C(Ph)?C(H)B(C6F5)3] ( 4 ). A related phosphino‐phosphonium borate species—[(Ph4P4)P(Ph)C6F4B(F)(C6F5)2] ( 5 ) is also isolated from the thermolysis of B(C6F5)3 and P5Ph5. 相似文献
11.
A Highly Reactive Geminal P/B Frustrated Lewis Pair: Expanding the Scope to C−X (X=Cl,Br) Bond Activation
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Kamil Samigullin Isabelle Georg Dr. Michael Bolte Dr. Hans‐Wolfram Lerner Prof. Dr. Matthias Wagner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3478-3484
The geminal frustrated Lewis pair tBu2PCH2B(Fxyl)2 ( 1 ; Fxyl=3,5‐(CF3)2C6H3) is accessible in 65 % yield from tBu2PCH2Li and (Fxyl)2BF. According to NMR spectroscopy and X‐ray crystallography, 1 is monomeric both in solution and in the solid state. The intramolecular P ??? B distance of 2.900(5) Å and the full planarity of the borane site exclude any significant P/B interaction. Compound 1 readily activates a broad variety of substrates including H2, EtMe2SiH, CO2/CS2, Ph2CO, and H3CCN. Terminal alkynes react with heterolysis of the C?H bond. Haloboranes give cyclic adducts with strong P?BX3 and weak R3B?X bonds. Unprecedented transformations leading to zwitterionic XP/BCX3 adducts occur on treatment of 1 with CCl4 or CBr4 in Et2O. In less polar solvents (C6H6, n‐pentane), XP/BCX3 adduct formation is accompanied by the generation of significant amounts of XP/BX adducts. FLP 1 catalyzes the hydrogenation of PhCH=NtBu and the hydrosilylation of Ph2CO with EtMe2SiH. 相似文献
12.
Papri Bhattacharya Zachariah M. Heiden Geoffrey M. Chambers Samantha I. Johnson R. Morris Bullock Michael T. Mock 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(34):11744-11750
Catalysts for the oxidation of NH3 are critical for the utilization of NH3 as a large‐scale energy carrier. Molecular catalysts capable of oxidizing NH3 to N2 are rare. This report describes the use of [Cp*Ru(PtBu2NPh2)(15NH3)][BArF4], (PtBu2NPh2=1,5‐di(phenylaza)‐3,7‐di(tert‐butylphospha)cyclooctane; ArF=3,5‐(CF3)2C6H3), to catalytically oxidize NH3 to dinitrogen under ambient conditions. The cleavage of six N?H bonds and the formation of an N≡N bond was achieved by coupling H+ and e? transfers as net hydrogen atom abstraction (HAA) steps using the 2,4,6‐tri‐tert‐butylphenoxyl radical (tBu3ArO.) as the H atom acceptor. Employing an excess of tBu3ArO. under 1 atm of NH3 gas at 23 °C resulted in up to ten turnovers. Nitrogen isotopic (15N) labeling studies provide initial mechanistic information suggesting a monometallic pathway during the N???N bond‐forming step in the catalytic cycle. 相似文献
13.
Reactions of [{M(μ‐Cl)(coe)2}2] (M = Rh, Ir; coe = cis‐cyclooctene) with the secondary phosphane tBu2PH under various molar ratios were investigated. Probably, for kinetic reasons, the reaction behavior of the rhodium species differed from that of the iridium analogue in some instances. During these studies complexes [MCl(tBu2PH)3] [M = Rh ( 1 ), Ir ( 2 )] were isolated, and solution variable‐temperature 31P{1H} NMR studies revealed that these complexes show a conformational rigidity on the NMR time scale. Spectra recorded in the temperature range from 173 to 373 K indicated in each case only one rotamer containing three chemically nonequivalent phosphanes due to the restricted rotation of these ligands about the M–P bonds and the tert‐butyl substituents around the P–C(tBu) bonds, respectively. Compound 1 showed in solution already at room temperature in several solvents a dissociation of a phosphane ligand affording the known complex [{Rh(μ‐Cl)(tBu2PH)2}2] beside the free phosphane. In contrast to these findings, the iridium analogue 2 remained completely unchanged under similar conditions and exhibited, therefore, some kinetic inertness. For a better understanding of the NMR spectroscopic investigations, the molecular structure of 1 in the solid state was confirmed by X‐ray crystallography. 相似文献
14.
Dimethylamine‐tris(pentafluoroethyl)borane (C2F5)3B · NHMe2 ( 1 ) has been obtained from C2F5I, Br2BNMe2 and tris(diethylamino)phosphane in sulfolane. Alkylation using CH3I/KOH yielded the trimethylamine‐tris(pentafluoroethyl)borane (C2F5)3B · NMe3 ( 2 ). Compound 2 reacts with NEt3×3HF at 200—204 °C under replacement of the trimethylamine ligand to form the novel fluoro‐tris(pentafluoroethyl)borate anion [(C2F5)3BF]— ( 3 ) in good yield. Side products are the hydroxy‐tris(pentafluoroethyl)borate [(C2F5)3BOH]— ( 4 ) and the hydrido‐tris(pentafluoroethyl)borate [(C2F5)3BH]— ( 5 ). 相似文献
15.
Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XVII [1] [Co(g5‐Me5C5)(g3‐tBu2PPCH–CH3)] from [Co(g5‐Me5C5)(g2‐C2H4)2] and tBu2P–P=P(Me)tBu2 [Co(η5‐Me5C5)(η3‐tBu2PPCH–CH3)] 1 is formed in the reaction of [Co(η5‐Me5C5)(η2‐C2H4)2] 2 with tBu2P–P 4 (generated from tBu2P–P=P(Me)tBu2 3 ) by elimination of one C2H4 ligand and coupling of the phosphinophosphinidene with the second one. The structure of 1 is proven by 31P, 13C, 1H NMR spectra and the X‐ray structure analysis. Within the ligand tBu2P1P2C1H–CH3 in 1 , the angle P1–P2–C1 amounts to 90°. The Co, P1, P2, C1 atoms in 1 look like a „butterfly”︁. The reaction of 2 with a mixture of tBu2P–P=P(Me)tBu2 3 and tBu–C?P 5 yields [Co(η5‐Me5C5){η4‐(tBuCP)2}] 6 and 1 . While 6 is spontaneously formed, 1 appears only after complete consumption of 5 . 相似文献
16.
Chao Chen Florian Eweiner Birgit Wibbeling Roland Frhlich Shunsuke Senda Yasuhiro Ohki Kazuyuki Tatsumi Stefan Grimme Gerald Kehr Gerhard Erker 《化学:亚洲杂志》2010,5(10):2199-2208
The zirconocene complex [{(C6F5)2B‐(CH2)3‐Cp}(Cp‐PtBu2)ZrCl2] ( 6 ; Cp=cyclo‐C5H4) was prepared by hydroboration of [(allyl‐Cp)(Cp‐PtBu2)ZrCl2] ( 5 ) with HB(C6F5)2 (“Piers’ borane”). It represents a frustrated Lewis pair (FLP) in which both the Lewis acid and the Lewis base were attached at the metallocene framework. Its reaction with 1‐pentyne did not result in the 1,2‐addition of or deprotonation reaction by the FLP, but rather in the 1,1‐carboboration of the triple bond, thereby obtaining a Z/E mixture (1.2:1) of the respective organometallic substituted alkenes 7 . The analogous reaction of 1‐pentyne with the phosphorous‐free system [{(C6F5)2B‐(CH2)3‐Cp)}CpZrCl2] ( 9 ) gave the respective 1,1‐carboboration products ( Z‐10 / E‐10 ≈1.3:1). 相似文献
17.
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
18.
Pablo Ríos Hugo Fouilloux Dr. Pietro Vidossich Dr. Josefina Díez Prof. Dr. Agustí Lledós Dr. Salvador Conejero 《Angewandte Chemie (International ed. in English)》2018,57(12):3217-3221
The platinum complex [Pt(ItBuiPr′)(ItBuiPr)][BArF] interacts with tertiary silanes to form stable (<0 °C) mononuclear PtII σ‐SiH complexes [Pt(ItBuiPr′)(ItBuiPr)(η1‐HSiR3)][BArF]. These compounds have been fully characterized, including X‐ray diffraction methods, as the first examples for platinum. DFT calculations (including electronic topological analysis) support the interpretation of the coordination as an unusual η1‐SiH. However, the energies required for achieving a η2‐SiH mode are rather low, and is consistent with the propensity of these derivatives to undergo Si?H cleavage leading to the more stable silyl species [Pt(SiR3)(ItBuiPr)2][BArF] at room temperature. 相似文献
19.
Three Lewis acid–base adducts t‐Bu3Ga–EPh3 (E = P 1 , As 2 , Sb 3 ) were synthesized by reactions of Ph3E and t‐Bu3Ga and characterized by heteronuclear NMR (1H, 13C (31P)) and IR spectroscopy, elemental analysis and single crystal X‐ray diffraction. Their structural parameters are discussed and compared to similar t‐Bu3Ga adducts. The strength of the donor‐acceptor interactions within 1 – 3 was investigated in solution by temperature‐dependent 1H NMR spectroscopy and by quantum chemical calculations. 相似文献
20.
Dr. Christoph Helling Lars J. C. van der Zee Jelle Hofman Felix J. de Zwart Dr. Simon Mathew Dr. Martin Nieger Assoc. Prof. Dr. J. Chris Slootweg 《Angewandte Chemie (International ed. in English)》2023,62(48):e202313397
Herein, we present the formation of transient radical ion pairs (RIPs) by single-electron transfer (SET) in phosphine−quinone systems and explore their potential for the activation of C−H bonds. PMes3 (Mes=2,4,6-Me3C6H2) reacts with DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) with formation of the P−O bonded zwitterionic adduct Mes3P−DDQ ( 1 ), while the reaction with the sterically more crowded PTip3 (Tip=2,4,6-iPr3C6H2) afforded C−H bond activation product Tip2P(H)(2-[CMe2(DDQ)]-4,6-iPr2-C6H2) ( 2 ). UV/Vis and EPR spectroscopic studies showed that the latter reaction proceeds via initial SET, forming RIP [PTip3]⋅+[DDQ]⋅−, and subsequent homolytic C−H bond activation, which was supported by DFT calculations. The isolation of analogous products, Tip2P(H)(2-[CMe2{TCQ−B(C6F5)3}]-4,6-iPr2-C6H2) ( 4 , TCQ=tetrachloro-1,4-benzoquinone) and Tip2P(H)(2-[CMe2{oQtBu−B(C6F5)3}]-4,6-iPr2-C6H2) ( 8 , oQtBu=3,5-di-tert-butyl-1,2-benzoquinone), from reactions of PTip3 with Lewis-acid activated quinones, TCQ−B(C6F5)3 and oQtBu−B(C6F5)3, respectively, further supports the proposed radical mechanism. As such, this study presents key mechanistic insights into the homolytic C−H bond activation by the synergistic action of radical ion pairs. 相似文献