The first terminal manganese phosphinidene complex was quantitatively synthesized from a terminal alkylborylene complex. Its structure and bonding, as well as the reaction mechanism, were investigated through a combination of experimental and computational studies. 相似文献
Reaction of [U(TrenTIPS)(THF)][BPh4] ( 1 ; TrenTIPS=N{CH2CH2NSi(iPr)3}3) with NaPH2 afforded the novel f‐block terminal parent phosphide complex [U(TrenTIPS)(PH2)] ( 2 ; U–P=2.883(2) Å). Treatment of 2 with one equivalent of KCH2C6H5 and two equivalents of benzo‐15‐crown‐5 ether (B15C5) afforded the unprecedented metal‐stabilized terminal parent phosphinidene complex [U(TrenTIPS)(PH)][K(B15C5)2] ( 4 ; U?P=2.613(2) Å). DFT calculations reveal a polarized‐covalent U?P bond with a Mayer bond order of 1.92. 相似文献
The synthesis, electronic structure, and reactivity of a uranium metallacyclopropene were comprehensively studied. Addition of diphenylacetylene (PhC≡CPh) to the uranium phosphinidene metallocene [η5-1,2,4-(Me3C)3C5H2]2U=P-2,4,6-tBu3C6H2 ( 1 ) yields the stable uranium metallacyclopropene, [η5-1,2,4-(Me3C)3C5H2]2U[η2-C2Ph2] ( 2 ). Based on density functional theory (DFT) results the 5f orbital contributions to the bonding within the metallacyclopropene U-(η2-C=C) moiety increases significantly compared to the related ThIV compound [η5-1,2,4-(Me3C)3C5H2]2Th[η2-C2Ph2], which also results in more covalent bonds between the [η5-1,2,4-(Me3C)3C5H2]2U2+ and [η2-C2Ph2]2− fragments. Although the thorium and uranium complexes are structurally closely related, different reaction patterns are therefore observed. For example, 2 reacts as a masked synthon for the low-valent uranium(II) metallocene [η5-1,2,4-(Me3C)3C5H2]2UII when reacted with Ph2E2 (E=S, Se), alkynes and a variety of hetero-unsaturated molecules such as imines, ketazine, bipy, nitriles, organic azides, and azo derivatives. In contrast, five-membered metallaheterocycles are accessible when 2 is treated with isothiocyanate, aldehydes, and ketones. 相似文献
Reduction of the uranium(III) metallocene [(η5‐C5iPr5)2UI] ( 1 ) with potassium graphite produces the “second‐generation” uranocene [(η5‐C5iPr5)2U] ( 2 ), which contains uranium in the formal divalent oxidation state. The geometry of 2 is that of a perfectly linear bis(cyclopentadienyl) sandwich complex, with the ground‐state valence electron configuration of uranium(II) revealed by electronic spectroscopy and density functional theory to be 5f3 6d1. Appreciable covalent contributions to the metal‐ligand bonds were determined from a computational study of 2 , including participation from the uranium 5f and 6d orbitals. Whereas three unpaired electrons in 2 occupy orbitals with essentially pure 5f character, the fourth electron resides in an orbital defined by strong 7s‐6d mixing. 相似文献
A soft embrace for U : Replacement of C5Me5 by the soft PNP pincer ligand is a successful strategy to promote new reactivities and support new structures for the actinide series (see picture, py–O=pyridine‐N‐oxide). The specific electronic and steric properties of the PNP ligand enable access to previously unreported structures not available for the C5Me5 ligand set and support not only low‐valent uranium but also the high‐valent uranium(VI) ion.
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
Uranium diazomethanediide complexes can be prepared and their synthesis, structure and reactivity were explored. Reaction of the uranium imido compound [η5-1,2,4-(Me3Si)3C5H2]2U=N(p-tolyl)(dmap) ( 1 ) or [η5-1,3-(Me3C)2C5H3]2U=N(p-tolyl)(dmap) ( 4 ) with Me3SiCHN2 cleanly yields the first isocyanoimido metal complexes [η5-1,2,4-(Me3Si)3C5H2]2U(=NNC)(μ-CNN=)U(dmap)[η5-1,2,4-(Me3Si)3C5H2]2 ( 2 ) and {[η5-1,3-(Me3C)2C5H3]2U[μ-(=NNC)]}6 ( 5 ), respectively. Both compounds exhibit remarkable thermal stability and were fully characterized. According to density functional theory (DFT) studies the bonding between the Cp2U2+ and [NNC]2− moieties is strongly polarized with a significant 5 f orbital contribution, which is also reflected in the reactivity of these complexes. For example, complex 5 acts as a nucleophile toward alkylsilyl halides and engages in a [2+2] cycloaddition with CS2, but no reaction occurs in the presence of internal alkynes. 相似文献
The reaction of the base‐free terminal thorium imido complex [{η5‐1,2,4‐(Me3C)3C5H2}2Th?N(p‐tolyl)] ( 1 ) with p‐azidotoluene yielded irreversibly the tetraazametallacyclopentene [{η5‐1,2,4‐(Me3C)3C5H2}2Th{N(p‐tolyl)N?N? N(p‐tolyl)}] ( 2 ), whereas the bridging imido complex [{[η5‐1,2,4‐(Me3C)3C5H2]Th(N3)2}2{μ‐N(p‐tolyl)}2][(n‐C4H9)4N]2 ( 3 ) was isolated from the reaction of 1 with [(n‐C4H9)4N]N3. Unexpectedly, upon the treatment of 1 with 9‐diazofluorene, the NN bond was cleaved, an N atom was transferred, and the η2‐diazenido iminato complex [{η5‐1,2,4‐(Me3C)3C5H2}2Th{η2‐[N?N(p‐tolyl)]}{N?(9‐C13H8)}] ( 4 ) was formed. In contrast, the reaction of 1 with Me3SiCHN2 gave the nitrilimido complex [{η5‐1,2,4‐(Me3C)3C5H2}2Th{NH(p‐tolyl)}{N2CSiMe3}] ( 5 ), which slowly converted into [{η5‐1,2,4‐(Me3C)3C5H2}{η5:κ‐N‐1,2‐(Me3C)2‐4‐CMe2(CH2NN?CHSiMe3)C5H2}Th{NH(p‐tolyl)}] ( 6 ) by intramolecular C? H bond activation. The experimental results are complemented by density functional theory (DFT) studies. 相似文献
This contribution focuses on complex [Mo2(H)2(μ-AdDipp2)2] ( 1 ) and tetrahydrofuran and pyridine adducts [Mo2(H)2(μ-AdDipp2)2(L)2] ( 1⋅thf and 1⋅py ), which contain a trans-(H)Mo≣Mo(H) core (AdDipp2=HC(NDipp2)2; Dipp=2,6-iPr2C6H3). Computational studies provide insights into the coordination and electronic characteristics of the central trans-Mo2H2 unit of 1 , with four-coordinate, fourteen-electron Mo atoms and ϵ-agostic interactions with Dipp methyl groups. Small size C- and N-donors give rise to related complexes 1⋅L but only one molecule of P-donors, for example, PMe3, can bind to 1 , causing one of the hydrides to form a three-centered, two-electron (3c-2e) Mo-H→Mo bond ( 2⋅PMe3 ). A DFT analysis of the terminal and bridging hydride coordination to the Mo≣Mo bond is also reported, along with reactivity studies of the Mo−H bonds of these complexes. Reactions investigated include oxidation of 1⋅thf by silver triflimidate, AgNTf2, to afford a monohydride [Mo2(μ-H)(μ-NTf2)(μ-AdDipp2)2] ( 4 ), with an O,O’-bridging triflimidate ligand. 相似文献
A standing iceberg illustrates how the soft PNP pincer ligand challenges the metallocene dominance (ship) in actinide chemistry, as described by J. L. Kiplinger and co‐workers in their Communication on page 3681 ff. Replacement of C5Me5 by the PNP ligand is a successful strategy for the promotion of new reactivities and to support new actinide structures. The specific electronic and steric properties of the PNP ligand enable access to structures not available for the C5Me5 ligand set and as yet unreported for uranium. (We thank Mr. Anthony Mancinco for the design of the graphic.)
Three novel aspects emerge for the reaction of [5]metacyclophane ( 1 ) with the (intermediate) phenylphosphinidene complex 2 to give the 7-phosphanorbornadiene 3 . It is the first 1,4-addition of a phosphinidene complex to an unsaturated system, the first addition of a phosphinidene complex to a benzene ring, and the first [4+1] cycloaddition to an aromatic compound. 相似文献
The hydrogen transfer reaction mechanism of the complex of a singlet thiol phosphinidene and a polar molecule hydrogen fluoride (HSP- - - HF) has been investigated at the B3LYP/6-311+G (d,p) level in order to better understand the reactivity of singlet phosphinidene. The results show that the relevant reaction, including step 1 [HSP- - -HF(1) → TS1 (2) → HSPH(F) (3)] and step 2 [HSPH(F) (3) → TS2 (4) → H2SPF (5)], are very different from the reactions of hydroxyl phosphinidene with hydrogen fluoride. Furthermore, theoretical studies on the thermodynamic and kinetic properties of the reaction have been carried out over the temperature range of 200–1200 K using the DFT/B3LYP method, the general statistical thermodynamics, and Eyring transition state theory with Wigner correction, which is used to examine the temperature effects the reaction channel. It is concluded that step 1 has both thermodynamic and kinetic advantages over step 2, and the high temperature is favorable to step 2. Moreover, the order of lgK and lgk for the steps are consistent with the order of their exoergic energies ΔE and barrier height, but the differences of lgK and lgk for the steps decrease with the temperature increases. 相似文献
The formation of actinide–transition metal heterobimetallics mediated by a terminal actinide imido complex was comprehensively studied. The reaction of the thorium imido complex [(η5‐C5Me5)2Th=N(mesityl)(DMAP)] ( 3 ), prepared from [(η5‐C5Me5)2ThMe2] ( 1 ) and mesitylNH2 or [(η5‐C5Me5)2Th(NHmesityl)2] ( 2 ) in the presence of 4‐(dimethylamino)pyridine (DMAP), with copper(I) halides gave the first thorium–copper heterobimetallic compounds [(η5‐C5Me5)2Th(X){N(mesityl)Cu(DMAP)}] (X=Cl ( 4 ), Br ( 5 ), I ( 6 )). Complexes 4 – 6 feature an unusual geometry with a short Th?Cu distance, which DFT studies attribute to a weak donor–acceptor bond from the Cu+ atom to the electropositive Th4+ atom. They are reactive species, as was shown by their reaction with the dimethyl complex [(η5‐C5Me5)2ThMe2] ( 1 ). Furthermore, a comparison between Th and early transition metals confirmed that Th4+ exhibits distinctively different reactivity from d‐transition metals. 相似文献
The synthesis of mixed tethered alkyl uranium metallocenes has been investigated by examining the reactivity of the bis(tethered alkyl) metallocene [(η5‐C5Me4SiMe2CH2‐κC)2U] ( 1 ) with substrates that react with only one of the U? C linkages. The effect of these mixed tether coordination environments on the reactivity of the remaining U? C bond has been studied by using CO insertion chemistry. One equivalent of azidoadamantane (AdN3) reacts with 1 to yield the mixed tethered alkyl triazenido complex [(η5‐C5Me4SiMe2CH2‐κC)U(η5‐C5Me4SiMe2‐CH2NNN‐Ad‐κ2N1,3)]. Similarly, a single equivalent of CS2 reacts with 1 to form the mixed tethered alkyl dithiocarboxylate complex [(η5‐C5Me4SiMe2CH2‐κC)U(η5‐C5Me4SiMe2‐ CH2C(S)2‐κ2S,S′)], a reaction that constitutes the first example of CS2 insertion into a U4+? C bond. Complex 1 reacts with one equivalent of pyridine N‐oxide by C? H bond activation of the pyridine ring to form a mixed tethered alkyl cyclometalated pyridine N‐oxide complex [(η5‐C5Me4SiMe2CH2‐κC)(η5‐C5Me4SiMe3)U(C6H4NO‐κ2C,O)]. The remaining (η5‐C5Me4SiMe2CH2‐κC)2? ligand in each of these mixed tethered species show reactivity towards CO and tethered enolate ligands form by insertion. Subsequent rearrangement have been identified in [(η5‐C5Me4SiMe3)U(C5H4NO‐κ2C,O)(η5‐C5Me4SiMe2C(?CH2)O‐κO)] and [(η5‐C5Me4SiMe2CH2NNN‐Ad‐κ2N1,3)U(η5‐C5Me4SiMe2C(?CH2)O‐κO)]. 相似文献
A novel type of uranium‐containing microspheres with an urchin‐like hierarchical nano/microstructure has been successfully synthesized by a facile template‐free hydrothermal method with uranyl nitrate hexahydrate, urea, and glycerol as the uranium source, precipitating agent, and shape‐controlling agent, respectively. The as‐synthesized microspheres were usually a few micrometers in size and porous inside, and their shells were composed of nanoscale rod‐shaped crystals. The growth mechanism of the hydrothermal reaction was studied, revealing that temperature, ratios of reactants, solution pH, and reaction time were all critical for the growth. The mechanism study also revealed that an intermediate compound of 3 UO3?NH3?5 H2O was first formed and then gradually converted into the final hydrothermal product. These uranium‐containing microspheres were excellent precursors to synthesize porous uranium oxide microspheres. With a suitable calcination temperature, very uniform microspheres of uranium oxides (UO2+x, U3O8, and UO3) were successfully synthesized. 相似文献
Two mononuclear uranyl complexes, [UO2L1] ( 1 ) and [UO2L2] ⋅ 0.5 CH3CN ⋅ 0.25 CH3OH ( 2 ), have been synthesized from two multidentate N3O4 donor ligands, N,N′-bis(5-methoxysalicylidene)diethylenetriamine (H2L1) and N,N′-bis(3-methoxysalicylidene)diethylenetriamine (H2L2), respectively, and have been structurally characterized. Both complexes 1 and 2 showed a reversible UVI/UV couple at −1.571 and −1.519 V, respectively, in cyclic voltammetry. The reduction potential of the UVI/UV couple shifted towards more positive potential on addition of Li+, Na+, K+, and Ag+ metal ions to acetonitrile solutions of complex 2 , and the resulting potential was correlated with the Lewis acidity of the metal ions and was also justified by theoretical DFT calculations. No such shift in reduction potential was observed for complex 1 . All four bimetallic products, [UO2L2Li0.5](ClO4)0.5 ( 3 ), [UO2L2Na(ClO4)]2 ( 4 ), [UO2L2Ag(NO3)(H2O)] ( 5 ), and [(UO2L2)2K(H2O)2]PF6 ( 6 ), formed on addition of the Li+, Na+, Ag+, and K+ metal ions, respectively, to acetonitrile solutions of complex 2 , were isolated in the solid state and structurally characterized by single-crystal X-ray diffraction. In all the species, the inner N3O2 donor set of the ligand encompasses the equatorial plane of the uranyl ion and the outer open compartment with O2O′2 donor sites hosts the second metal ion. 相似文献