共查询到20条相似文献,搜索用时 10 毫秒
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Rosie Magnall Gbor Balzs Erli Lu Floriana Tuna Ashley J. Wooles Manfred Scheer Stephen T. Liddle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(30):10321-10325
The chemistry of 2‐phosphaethynolate is burgeoning, but there remains much to learn about this ligand, for example its reduction chemistry is scarce as this promotes P‐C‐O fragmentations or couplings. Here, we report that reduction of [U(TrenTIPS)(OCP)] (TrenTIPS=N(CH2CH2NSiPri3)3) with KC8/2,2,2‐cryptand gives [{U(TrenTIPS)}2{μ‐η2(OP):η2(CP)‐OCP}][K(2,2,2‐cryptand)]. The coordination mode of this trapped 2‐phosphaethynolate is unique, and derives from an unprecedented highly reduced and highly bent form of this ligand with the most acute P‐C‐O angle in any complex to date (P‐C‐O ? ≈127°). The characterisation data support a mixed‐valence diuranium(III/IV) formulation, where backbonding from uranium gives a highly reduced form of the P‐C‐O unit that is perhaps best described as a uranium‐stabilised OCP2?. radical dianion. Quantum chemical calculations reveal that this gives unprecedented carbene character to the P‐C‐O unit, which engages in a weak donor–acceptor interaction with one of the uranium ions. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(4):1085-1089
Naphthalene and acenaphthene with peri 2‐py and BMes2 (py=pyridyl, Mes=mesityl) substituents have been found to undergo facile phototransformation, cleavage of a C−C bond of naphthalene, and formation of 2‐py‐bound benzoborepins as the major products. Mechanistic pathways of this photoreaction have been established by examination of both excited and ground states by using CASSCF and CASPT2 methods in DFT and time‐dependent DFT calculations. The mesityl to py‐naphthyl charge‐transfer transition and the mesityl migration from the boron atom to the naphthyl moiety drive this unprecedented C−C bond cleavage and boron‐insertion reaction. 相似文献
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Linus Appel Jennifer Leduc Christopher L. Webster Joseph W. Ziller William J. Evans Sanjay Mathur 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(7):2237-2241
Four air‐stable, volatile uranium heteroarylalkenolates have been synthesized and characterized by three synthetic approaches and their gas phase deposition to uranium oxide films has been examined. 相似文献
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Nikki J. Wolford Dumitru‐Claudiu Sergentu William W. Brennessel Jochen Autschbach Michael L. Neidig 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(30):10372-10376
The synthesis and characterization of sterically unencumbered homoleptic organouranium aryl complexes containing U?C σ‐bonds has been of interest to the chemical community for over 70 years. Reported herein are the first structurally characterized, sterically unencumbered homoleptic uranium (IV) aryl‐ate species of the form [U(Ar)6]2? (Ar=Ph, p‐tolyl, p‐Cl‐Ph). Magnetic circular dichroism (MCD) spectroscopy and computational studies provide insight into electronic structure and bonding interactions in the U?C σ‐bond across this series of complexes. Overall, these studies solve a decades‐long challenge in synthetic uranium chemistry, enabling new insight into electronic structure and bonding in organouranium complexes. 相似文献
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Mark D. Straub Jennifer Leduc Michael Frank Aida Raauf Trevor D. Lohrey Stefan G. Minasian Sanjay Mathur John Arnold 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5805-5809
Homoleptic uranium(IV) amidate complexes have been synthesized and applied as single‐source molecular precursors for the chemical vapor deposition of UO2 thin films. These precursors decompose by alkene elimination to give highly crystalline phase‐pure UO2 films with an unusual branched heterostructure. 相似文献
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Jianzhong Chen Zhenfeng Zhang Delong Liu Wanbin Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(29):8584-8587
A chemoselective C−O bond cleavage of the ester alkyl side‐chain of α‐acyloxy ketones was realized for the first time by a highly efficient palladium‐catalyzed hydrogenolysis (S/C=6000, the highest catalytic efficiency by far). Furthermore, a kinetic resolution of α‐acyloxy ketones was first developed by enantioselective hydrogenolysis with good yields and up to 99 % ee. 相似文献
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The determination of the two species of uranium(VI and IV) present in 6 uranium ores was studied in relation to the chemical and mineralogical composition, humidity, and pH of the samples taken over from the mine. X‐ray diffraction studies, performed on the uranium ores in powder form allowed to establish their mineralogical composition. Thechemical analysis pointed out the presence, besides the two uranium species, of some microelements able to influence the UVI/UIV ratio in minerals and to leach out UVI as uranyl ions from the corresponding minerals. 相似文献
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Erli Lu Oliver J. Cooper Jonathan McMaster Floriana Tuna Eric J. L. McInnes William Lewis Alexander J. Blake Stephen T. Liddle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(26):6814-6818
We report the uranium(VI) carbene imido oxo complex [U(BIPMTMS)(NMes)(O)(DMAP)2] ( 5 , BIPMTMS=C(PPh2NSiMe3)2; Mes=2,4,6‐Me3C6H2; DMAP=4‐(dimethylamino)pyridine) which exhibits the unprecedented arrangement of three formal multiply bonded ligands to one metal center where the coordinated heteroatoms derive from different element groups. This complex was prepared by incorporation of carbene, imido, and then oxo groups at the uranium center by salt elimination, protonolysis, and two‐electron oxidation, respectively. The oxo and imido groups adopt axial positions in a T‐shaped motif with respect to the carbene, which is consistent with an inverse trans‐influence. Complex 5 reacts with tert‐butylisocyanate at the imido rather than carbene group to afford the uranyl(VI) carbene complex [U(BIPMTMS)(O)2(DMAP)2] ( 6 ). 相似文献
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Radmila Faizova Dr. Farzaneh Fadaei-Tirani Prof. Dr. Rizlan Bernier-Latmani Prof. Dr. Marinella Mazzanti 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(17):6822-6825
Reduction of uranyl(VI) to UV and to UIV is important in uranium environmental migration and remediation processes. The anaerobic reduction of a uranyl UVI complex supported by a picolinate ligand in both organic and aqueous media is presented. The [UVIO2(dpaea)] complex is readily converted into the cis-boroxide UIV species via diborane-mediated reductive functionalization in organic media. Remarkably, in aqueous media the uranyl(VI) complex is rapidly converted, by Na2S2O4, a reductant relevant for chemical remediation processes, into the stable uranyl(V) analogue, which is then slowly reduced to yield a water-insoluble trinuclear UIV oxo-hydroxo cluster. This report provides the first example of direct conversion of a uranyl(VI) compound into a well-defined molecular UIV species in aqueous conditions. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(47):15235-15239
We report herein that 4‐alkyl‐1,4‐dihydropyridines (alkyl‐DHPs) can directly reach an electronically excited state upon light absorption and trigger the generation of C(sp3)‐centered radicals without the need for an external photocatalyst. Selective excitation with a violet‐light‐emitting diode turns alkyl‐DHPs into strong reducing agents that can activate reagents through single‐electron transfer manifolds while undergoing homolytic cleavage to generate radicals. We used this photochemical dual‐reactivity profile to trigger radical‐based carbon–carbon bond‐forming processes, including nickel‐catalyzed cross‐coupling reactions. 相似文献
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Christopher J. Hoerger Frank W. Heinemann Elisa Louyriac Massimo Rigo Laurent Maron Hansjrg Grützmacher Matthias Driess Karsten Meyer 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(6):1693-1697
Reaction of the trivalent uranium complex [((Ad,MeArO)3N)U(DME)] with one molar equiv [Na(OCAs)(dioxane)3], in the presence of 2.2.2‐crypt, yields [Na(2.2.2‐crypt)][{((Ad,MeArO)3N)UIV(THF)}(μ‐O){((Ad,MeArO)3N)UIV(CAs)}] ( 1 ), the first example of a coordinated η1‐cyaarside ligand (CAs?). Formation of the terminal CAs? is promoted by the highly reducing, oxophilic UIII precursor [((Ad,MeArO)3N)U(DME)] and proceeds through reductive C?O bond cleavage of the bound arsaethynolate anion, OCAs?. If two equiv of OCAs? react with the UIII precursor, the binuclear, μ‐oxo‐bridged U2IV/IV complex [Na(2.2.2‐crypt)]2[{((Ad,MeArO)3N)UIV}2(μ‐O)(μ‐AsCAs)] ( 2 ), comprising the hitherto unknown μ:η1,η1‐coordinated (AsCAs)2? ligand, is isolated. The mechanistic pathway to 2 involves the decarbonylation of a dimeric intermediate formed in the reaction of 1 with OCAs?. An alternative pathway to complex 2 is by conversion of 1 via addition of one further equiv of OCAs?. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(4):1117-1120
General reductive silylation of the UO22+ cation occurs readily in a one‐pot, two‐step stoichiometric reaction at room temperature to form uranium(IV) siloxides. Addition of two equivalents of an alkylating reagent to UO2X2(L)2 (X=Cl, Br, I, OTf; L=triphenylphosphine oxide, 2,2′‐bipyridyl) followed by two equivalents of a silyl (pseudo)halide, R3Si‐X (R=aryl, alkyl, H; X=Cl, Br, I, OTf, SPh), cleanly affords (R3SiO)2UX2(L)2 in high yields. Support is included for the key step in the process, reduction of UVI to UV. This procedure is applicable to a wide range of commercially available uranyl salts, silyl halides, and alkylating reagents. Under this protocol, one equivalent of SiCl4 or two equivalents of Me2SiCl2 results in direct conversion of the uranyl to uranium(IV) tetrachloride. Full spectroscopic and structural characterization of the siloxide products is reported. 相似文献