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Ana M. Geer Ángel L. Serrano Prof. Bas de Bruin Prof. Miguel A. Ciriano Dr. Cristina Tejel 《Angewandte Chemie (International ed. in English)》2015,54(2):472-475
Complexes with terminal phosphanido (M? PR2) functionalities are believed to be crucial intermediates in new catalytic processes involving the formation of P? P and P? C bonds. We showcase here the isolation and characterization of mononuclear phosphanide rhodium complexes ([RhTp(H)(PR2)L]) that result from the oxidative addition of secondary phosphanes, a reaction that was also explored computationally. These compounds are active catalysts for the dehydrocoupling of PHPh2 to Ph2P? PPh2. The hydrophosphination of dimethyl maleate and the unactivated olefin ethylene is also reported. Reliable evidence for the prominent role of mononuclear phosphanido rhodium species in these reactions is also provided. 相似文献
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Dr. Holger Helten Alasdair P. M. Robertson Prof. Dr. Anne Staubitz James R. Vance Dr. Mairi F. Haddow Prof. Dr. Ian Manners 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(15):4665-4680
The dehydrocoupling/dehydrogenation behavior of primary arylamine–borane adducts ArNH2 ? BH3 ( 3 a – c ; Ar= a : Ph, b : p‐MeOC6H4, c : p‐CF3C6H4) has been studied in detail both in solution at ambient temperature as well as in the solid state at ambient or elevated temperatures. The presence of a metal catalyst was found to be unnecessary for the release of H2. From reactions of 3 a , b in concentrated solutions in THF at 22 °C over 24 h cyclotriborazanes (ArNH‐BH2)3 ( 7 a , b ) were isolated as THF adducts, 7 a , b? THF, or solvent‐free 7 a , which could not be obtained via heating of 3 a – c in the melt. The μ‐(anilino)diborane [H2B(μ‐PhNH)(μ‐H)BH2] ( 4 a ) was observed in the reaction of 3 a with BH3?THF and was characterized in situ. The reaction of 3 a with PhNH2 ( 2 a ) was found to provide a new, convenient method for the preparation of dianilinoborane (PhNH)2BH ( 5 a ), which has potential generality. This observation, together with further studies of reactions of 4 a , 5 a , and 7 a , b , provided insight into the mechanism of the catalyst‐free ambient temperature dehydrocoupling of 3 a – c in solution. For example, the reaction of 4 a with 5 a yields 6 a and 7 a . It was found that borazines (ArN‐BH)3 ( 6 a – c ) are not simply formed via dehydrogenation of cyclotriborazanes 7 a – c in solution. The transformation of 7 a to 6 a is slowly induced by 5 a and proceeds via regeneration of 3 a . The adducts 3 a – c also underwent rapid dehydrocoupling in the solid state at elevated temperatures and even very slowly at ambient temperature. From aniline–borane derivative 3 c , the linear iminoborane oligomer (p‐CF3C6H4)N[BH‐NH(p‐CF3C6H4)]2 ( 11 ) was obtained. The single‐crystal X‐ray structures of 3 a – c , 5 a , 7 a , 7 b? THF, and 11 are discussed. 相似文献
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Enantiopure Narrow Bite‐Angle POP Ligands: Synthesis and Catalytic Performance in Asymmetric Hydroformylations and Hydrogenations 下载免费PDF全文
Dr. Héctor Fernández‐Pérez Dr. Jordi Benet‐Buchholz Prof. Dr. Anton Vidal‐Ferran 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15375-15384
Herein is reported the preparation of a set of narrow bite‐angle P–OP ligands the backbone of which contains a stereogenic carbon atom. The synthesis was based on a Corey–Bakshi–Shibata (CBS)‐catalyzed asymmetric reduction of phosphomides. The structure of the resulting 1,1‐P–OP ligands, which was selectively tuned through adequate combination of the configuration of the stereogenic carbon atom, its substituent, and the phosphite fragment, proved crucial for providing a rigid environment around the metal center, as evidenced by X‐ray crystallography. These new ligands enabled very good catalytic properties in the Rh‐mediated enantioselective hydrogenation and hydroformylation of challenging and model substrates (up to 99 % ee). Whereas for asymmetric hydrogenation the optimal P–OP ligand depended on the substrate, for hydroformylation, a single ligand was the highest‐performing one for almost all studied substrates: it contains an R‐configured stereogenic carbon atom between the two phosphorus ligating groups, and an S‐configured 3,3′‐diphenyl‐substituted biaryl unit. 相似文献
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Acylsilanes in Rhodium(III)‐Catalyzed Directed Aromatic C–H Alkenylations and Siloxycarbene Reactions with CC Double Bonds 下载免费PDF全文
Peter Becker Dr. Daniel L. Priebbenow Ramona Pirwerdjan Prof. Dr. Carsten Bolm 《Angewandte Chemie (International ed. in English)》2014,53(1):269-271
Acylsilanes are known to undergo a 1,2‐silicon‐to‐oxygen migration under thermal or photochemical conditions to form siloxycarbenes. However, there are few reports regarding the application of siloxycarbenes in organic synthesis and surprisingly, their reaction with C? C double or triple bonds remains virtually unexplored. To facilitate such a study, previously inaccessible aromatic acylsilanes containing an ortho‐tethered C? C double bond were identified as suitable substrates. To access these key intermediates, we developed a new synthetic method utilizing a rhodium‐catalyzed oxidative Heck‐type olefination involving the application of an acylsilane moiety as a directing group. When exposed to visible‐light irradiation, the ortho‐olefinated acylsilanes underwent a smooth intramolecular cyclization process to afford valuable indanone derivatives in quantitative yields. This result paves the way for the development of new transformations involving siloxycarbene intermediates. 相似文献
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Dudekula Sharmila Bijan Mondal Rongala Ramalakshmi Sangita Kundu Dr. Babu Varghese Prof. Sundargopal Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5074-5083
A combined experimental and quantum chemical study of Group 7 borane, trimetallic triply bridged borylene and boride complexes has been undertaken. Treatment of [{Cp*CoCl}2] (Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) with LiBH4 ? thf at ?78 °C, followed by room‐temperature reaction with three equivalents of [Mn2(CO)10] yielded a manganese hexahydridodiborate compound [{(OC)4Mn}(η6‐B2H6){Mn(CO)3}2(μ‐H)] ( 1 ) and a triply bridged borylene complex [(μ3‐BH)(Cp*Co)2(μ‐CO)(μ‐H)2MnH(CO)3] ( 2 ). In a similar fashion, [Re2(CO)10] generated [(μ3‐BH)(Cp*Co)2(μ‐CO)(μ‐H)2ReH(CO)3] ( 3 ) and [(μ3‐BH)(Cp*Co)2(μ‐CO)2(μ‐H)Co(CO)3] ( 4 ) in modest yields. In contrast, [Ru3(CO)12] under similar reaction conditions yielded a heterometallic semi‐interstitial boride cluster [(Cp*Co)(μ‐H)3Ru3(CO)9B] ( 5 ). The solid‐state X‐ray structure of compound 1 shows a significantly shorter boron–boron bond length. The detailed spectroscopic data of 1 and the unusual structural and bonding features have been described. All the complexes have been characterized by using 1H, 11B, 13C NMR spectroscopy, mass spectrometry, and X‐ray diffraction analysis. The DFT computations were used to shed light on the bonding and electronic structures of these new compounds. The study reveals a dominant B?H?Mn, a weak B?B?Mn interaction, and an enhanced B?B bonding in 1 . 相似文献
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Melanie W. Lui Nathan R. Paisley Dr. Robert McDonald Dr. Michael J. Ferguson Prof. Dr. Eric Rivard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(6):2134-2145
We report the synthesis of structurally tunable boron complexes supported by N‐heterocyclic imine ligands IPr=N?BR2 (IPr=[(HCNDipp)2C], Dipp=2,6‐iPr2C6H3, R=Cl and/or Ph) that have the ability to abstract dihydrogen from amine‐boranes, and instigate their dehydrocoupling. In one instance, mild heating of the hydrogen addition product IPr=NH?B(Ph)HCl releases H2 to regenerate the starting N‐heterocyclic iminoborane; accordingly IPr=N?B(Ph)Cl can be used as a metal‐free catalyst to promote the dehydrocoupling of MeNH2 ? BH3 to yield N‐methylaminoborane oligomers [MeNH‐BH2]x. 相似文献
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Prof. P. Veeraraghavan Ramachandran Ameya S. Kulkarni Mark A. Pfeil Jacob D. Dennis Jared D. Willits Prof. Stephen D. Heister Prof. Steven F. Son Prof. Timothée L. Pourpoint 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):16869-16872
Complexation of amines with borane converts them to hypergols or decreases their ignition delays (IDs) multifold (with white fuming nitric acid as the oxidant). With consistently low IDs, amine–boranes represent a class of compounds that can be promising alternatives to toxic hydrazine and its derivatives as propellants. A structure–hypergolicity relationship study reveals the necessary features for the low ID. 相似文献
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Egle M. Beccalli Prof. Elena Borsini Stefano Brenna Dr. Simona Galli Dr. Micol Rigamonti Gianluigi Broggini Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(5):1670-1678
The isolation of σ‐alkylpalladium Heck intermediates, possible when β‐hydride elimination is inhibited, is a rather rare event. Performing intramolecular Heck reactions on N‐allyl‐2‐halobenzylamines in the presence of [Pd(PPh3)4], we isolated and characterized a series of stable bridged palladacycles containing an iodine or bromine atom on the palladium atom. Indolyl substrates were also tested for isolation of the corresponding complexes. X‐ray crystallographic analysis of one of the indolyl derivatives revealed the presence of a five‐membered palladacycle with the metal center bearing a PPh3 ligand and an iodine atom in a cis position with respect to the nitrogen atom. The stability of the σ‐alkylpalladium complexes is probably a consequence of the strong constraint resulting from the bridged junction that hampers the cisoid conformation essential for β‐hydride elimination. Subsequently, the thus obtained bridged five‐membered palladacycles were proven to be effective precatalysts in Heck reactions as well as in cross‐coupling processes such as Suzuki and Stille reactions. 相似文献
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Enantioselective Synthesis of Spiroindenes by Enol‐Directed Rhodium(III)‐Catalyzed CH Functionalization and Spiroannulation 下载免费PDF全文
Dr. Suresh Reddy Chidipudi Dr. David J. Burns Imtiaz Khan Prof. Hon Wai Lam 《Angewandte Chemie (International ed. in English)》2015,54(47):13975-13979
Chiral cyclopentadienyl rhodium complexes promote highly enantioselective enol‐directed C(sp2)‐H functionalization and oxidative annulation with alkynes to give spiroindenes containing all‐carbon quaternary stereocenters. High selectivity between two possible directing groups, as well as control of the direction of rotation in the isomerization of an O‐bound rhodium enolate into the C‐bound isomer, appear to be critical for high enantiomeric excesses. 相似文献
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Evidence of Amine–CO2 Interactions in Two Pillared‐Layer MOFs Probed by X‐ray Crystallography 下载免费PDF全文
Xiao‐Li Hu Qi‐Han Gong Rong‐Lin Zhong Prof. Xin‐Long Wang Prof. Chao Qin Hao Wang Prof. Jing Li Kui‐Zhan Shao Prof. Zhong‐Min Su 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):7238-7244
Two pillared‐layer metal–organic frameworks (MOFs; PMOF‐55 and NH2‐PMOF‐55) based on 1,2,4‐triazole and terephthalic acid (bdc)/NH2‐bdc ligands were assembled and display framework stabilities, to a certain degree, in both acid/alkaline solutions and toward water. They exhibit high CO2 uptakes and selective CO2/N2 adsorption capacities, with CO2/N2 selectivity in the range of 24–27, as calculated by the ideal adsorbed solution theory method. More remarkably, the site and interactions between the host network and the CO2 molecules were investigated by single‐crystal X‐ray diffraction, which showed that the main interaction between the CO2 molecules and PMOF‐55 is due to multipoint supramolecular interactions of C?H???O, C???O, and O???O. Amino functional groups were shown to enhance the CO2 adsorption and identified as strong adsorption sites for CO2 by X‐ray crystallography. 相似文献
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Dr. Abdessamad Grirrane Dr. Eleuterio Álvarez Prof. Dr. Hermenegildo García Prof. Dr. Avelino Corma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(1):340-354
Cationic and neutral silver(I)–L complexes (L=Buchwald‐type biaryl phosphanes) with nitrogen co‐ligands or organosulfonate counter ions have been synthesised and characterised through their structural and spectroscopic properties. At room temperature, both cationic and neutral silver(I)–L complexes are extremely active catalysts in the promotion of the single and double A3 coupling of terminal (di)alkynes, pyrrolidine and formaldehyde. In addition, the aza‐Diels–Alder two‐ and three‐component coupling reactions of Danishefsky’s diene with an imine or amine and aldehyde are efficiently catalysed by these cationic or neutral silver(I)–L complexes. The solvent influences the catalytic performance due to limited complex solubility or solvent decomposition and reactivity. The isolation of new silver(I)–L complexes with reagents as ligands lends support to mechanistic proposals for such catalytic processes. The activity, stability and metal–distal arene interaction of these silver(I)–L catalysts have been compared with those of analogous cationic gold(I) and copper(I) complexes. 相似文献