Hole or electron doping of phases prepared by topochemical reactions (e.g. anion deintercalation or anion‐exchange) is extremely challenging as these low‐temperature conversion reactions are typically very sensitive to the electron counts of precursor phases. Herein we report the successful hole and electron doping of the transition‐metal oxyhydride LaSr3NiRuO4H4 by first preparing precursors in the range LaxSr4?xNiRuO8 0.5<x<1.4 and then converting into the corresponding LaxSr4?xNiRuO4H4 phases. This is particularly noteworthy as the (Ni/Ru)H2 sheets in the LaxSr4?xNiRuO4H4 phases are structurally analogous to the CuO2 sheets in cuprate superconductors and hole doping (Ni1+/2+, Ru2+) or electron doping (Ni2+, Ru1+/2+) yields materials with partial occupancy in Ni/Ru –H 1s bands which are analogous to the partially occupied Cu –O 2p bands present in the CuO2 sheets of doped superconducting cuprates. 相似文献
A series of strontium vanadium oxide–hydride phases prepared by utilizing a low‐temperature synthesis strategy in which oxide ions in Srn+1VnO3n+1 (n=∞, 1, 2) phases are topochemically replaced by hydride ions to form SrVO2H, Sr2VO3H, and Sr3V2O5H2, respectively. These new phases contain sheets or chains of apex‐linked V3+O4 squares stacked with SrH layers/chains, such that the n=∞ member, SrVO2H, can be considered to be analogous to “infinite‐layer” phases, such as Sr1?xCaxCuO2 (the parent phase of the high‐Tc cuprate superconductors), but with a d2 electron count. All three oxide–hydride phases exhibit strong antiferromagnetic coupling, with SrVO2H exhibiting an antiferromagnetic ordering temperature, TN>300 K. The strong antiferromagnetic couplings are surprising given they appear to arise from π‐type magnetic exchange. 相似文献
Bismetallocenes [Cp2LuReCp2] and [Cp*2LaReCp2] (Cp=cyclopentadienyl; Cp*=pentamethylcyclopentadienyl) were prepared using different synthetic strategies. Salt metathesis—performed in aromatic hydrocarbons to avoid degradation pathways caused by THF—were identified as an attractive alternative to alkane elimination. Although alkane elimination is more attractive in the sense of its less elaborate workup, the rate of the reaction shows a strong dependence on the ionic radius of Ln3+ (Ln=lanthanide) within a given ligand set. Steric hindrance can cause a dramatic decrease in the reaction rate of alkane elimination. In this case, salt metathesis should be considered the better alternative. Covalent bonding interactions between the Ln and transition‐metal (TM) cations has been quantified on the basis of the delocalization index. Its magnitude lies within the range characteristic for bonds between transition metals. Secondary interactions were identified between carbon atoms of the Cp ligand of the transition metal and the Ln cation. Model calculations clearly indicated that the size of these interactions depends on the capability of the TM atom to act as an electron donor (i.e., a Lewis base). The consequences can even be derived from structural details. The observed clear dependency of the Lu?Ru and interfragment Lu?C bonding on the THF coordination of the Lu atom points to a tunable Lewis acidity at the Ln site, which provides a method of significantly influencing the structure and the interfragment bonding. 相似文献
Despite many exploratory studies over the past several decades, the presently known transition metals that form homoleptic transition‐metal hydride complexes are limited to the Groups 7–12. Here we present evidence for the formation of Mg3CrH8, containing the first Group 6 hydride complex [CrH7]5?. Our theoretical calculations reveal that pentagonal‐bipyramidal H coordination allows the formation of σ‐bonds between H and Cr. The results are strongly supported by neutron diffraction and IR spectroscopic measurements. Given that the Group 3–5 elements favor ionic/metallic bonding with H, along with the current results, the true boundary for the formation of homoleptic transition‐metal hydride complexes should be between Group 5 and 6. As the H coordination number generally tends to increase with decreasing atomic number of transition metals, the revised boundary suggests high potential for further discovery of hydrogen‐rich materials that are of both technological and fundamental interest. 相似文献
In the past decade, transition‐metal‐catalyzed C–H activations have been very popular in the research field of organometallic chemistry, and have been considered as efficient and convenient strategies to afford complex natural products, functional advanced materials, fluorescent compounds, and pharmaceutical compounds. In this account, we begin with a brief introduction to the development of transition‐metal‐catalyzed C–H activation, especially the development of transition‐metal‐catalyzed chelation‐assisted C–H activation. Then, a more detailed discussion is directed towards our recent studies on the transition‐metal‐catalyzed chelation‐assisted oxidative C–H/C–H functionalization of aromatic substrates bearing directing functional groups. 相似文献
Two unique organic–inorganic hybrid polyoxometalates constructed from Preyssler‐type [Na(H2O)P5W30O110]14? ({P5W30}) subunits and TM/Ln–carboxylate–Ln connectors (TM=transition metal, Ln=lanthanide), KNa7[{Sm6Mn(μ‐H2O)2(OCH2COO)7(H2O)18}{Na(H2O)P5W30O110}] ? 22 H2O ( 1 ) and K4[{Sm4Cu2(gly)2(ox)(H2O)24}{NaP5W30O110}]Cl2 ? 25 H2O ( 2 ; gly=glycine, ox=oxalate) have been hydrothermally synthesized and characterized by elemental analyses, IR spectra, UV/Vis‐NIR spectra, thermogravimetric analyses, power X‐ray diffraction, and single‐crystal X‐ray diffraction. Compound 1 displays one interesting 3D framework built by three types of subunits, {P5W30}, [Sm2Mn(μ‐H2O)2(OCH2COO)2(H2O)5]4+, and [Sm4(OCH2COO)5 (H2O)13]2+, whereas 2 also manifests the other intriguing 3D architecture created by three types of subunits, {P5W30}, [SmCu(gly)(H2O)8]4+, and [Sm2(ox)(H2O)8]4+. To our knowledge, 1 and 2 are the first 3D frameworks that contain {P5W30} units and TM/Ln–carboxylate–Ln connectors. The fluorescent properties of 1 and 2 have been investigated. 相似文献
1,4‐Cyclohexadiene derivatives are easily accessed via transition‐metal cycloadditions of 1,3‐dienes with alkynes. The mild reaction conditions of several transition‐metal‐catalysed reactions allows the incorporation of various functional groups to access functionalised 1,4‐cyclohexadienes. The control of the regiochemistry in the intermolecular cobalt‐catalysed Diels–Alder reaction is realised utilising different ligand designs. The functionalised 1,4‐cyclohexadiene derivatives are valuable building blocks in follow‐up transformations. Finally, the oxidation of the 1,4‐cyclohexadienes can be accomplished under mild conditions to generate the corresponding arene derivatives. 相似文献
The synthesis of a metal–organic framework (UiO‐67) functionalised simultaneously with two different transition metal complexes (Ir and Pd or Rh) through a one‐pot procedure is reported for the first time. This has been achieved by an iterative modification of the synthesis parameters combined with characterisation of the resulting materials using different techniques, including X‐ray absorption spectroscopy (XAS). The method also allows the first synthesis of UiO‐67 with a very wide range of loadings (from 4 to 43 mol %) of an iridium complex ([IrCp*(bpydc)(Cl)Cl]2?; bpydc=2,2′‐bipyridine‐5,5′‐dicarboxylate, Cp*=pentamethylcyclopentadienyl) through a pre‐functionalisation methodology. 相似文献
Metallacyclic complex [(Me2N)3Ta(η2‐CH2SiMe2NSiMe3)] ( 3 ) undergoes C?H activation in its reaction with H3SiPh to afford a Ta/μ‐alkylidene/hydride complex, [(Me2N)2{(Me3Si)2N}Ta(μ‐H)2(μ‐C‐η2‐CHSiMe2NSiMe3)Ta(NMe2)2] ( 4 ). Deuterium‐labeling studies with [D3]SiPh show H–D exchange between the Ta?D ?Ta unit and all methyl groups in [(Me2N)2{(Me3Si)2N}Ta(μ‐D)2(μ‐C‐η2‐CHSiMe2NSiMe3)Ta(NMe2)2] ([D2]‐ 4 ) to give the partially deuterated complex [Dn]‐ 4 . In addition, 4 undergoes β‐H abstraction between a hydride and an NMe2 ligand and forms a new complex [(Me2N){(Me3Si)2N}Ta(μ‐H)(μ‐N‐η2‐C,N‐CH2NMe)(μ‐C‐η2‐C,N‐CHSiMe2NSiMe3)Ta(NMe2)2] ( 5 ) with a cyclometalated, η2‐imine ligand. These results indicate that there are two simultaneous processes in [Dn]‐ 4 : 1) H–D exchange through σ‐bond metathesis, and 2) H?D elimination through β‐H abstraction (to give [Dn]‐ 5 ). Both 4 and 5 have been characterized by single‐crystal X‐ray diffraction studies. 相似文献
The orthogonal coordinative properties of tetrapyrrole macrocycles and nitrile ligands have been used in a multistep procedure towards interfacial d‐f hetero‐bimetallic nanoarchitectures based on a free‐base porphyrin derivative functionalized with meso‐cyanobiphenylene substituents. Molecular‐level scanning tunneling microscopy studies reveal that the porphyrin module alone self‐assembles on Ag(111) in a close‐packed layer with a square unit cell. Upon co‐deposition of Gd atoms, a square‐planar motif is formed that reflects the fourfold coordination of CN ligands to the rare‐earth centers. The resulting nanoporous network morphology is retained following exposure to a beam of Co atoms, which induces selective porphyrin metalation and ultimately yields a gridlike 2D metallosupramolecular architecture. 相似文献
Monodisperse metal clusters provide a unique platform for investigating magnetic exchange within molecular magnets. Herein, the core–shell structure of the monodisperse molecule magnet of [Gd52Ni56(IDA)48(OH)154(H2O)38]@SiO2 ( 1 a @SiO2) was prepared by encapsulating one high‐nuclearity lanthanide–transition‐metal compound of [Gd52Ni56(IDA)48(OH)154(H2O)38]?(NO3)18?164 H2O ( 1 ) (IDA=iminodiacetate) into one silica nanosphere through a facile one‐pot microemulsion method. 1 a @SiO2 was characterized using transmission electron microscopy, N2 adsorption–desorption isotherms, and inductively coupled plasma‐atomic emission spectrometry. Magnetic investigation of 1 and 1 a revealed J1=0.25 cm?1, J2=?0.060 cm?1, J3=?0.22 cm?1, J4=?8.63 cm?1, g=1.95, and zJ=?2.0×10?3 cm?1 for 1 , and J1=0.26 cm?1, J2=?0.065 cm?1, J3=?0.23 cm?1, J4=?8.40 cm?1g=1.99, and zJ=0.000 cm?1 for 1 a @SiO2. The zJ=0 in 1 a @SiO2 suggests that weak antiferromagnetic coupling between the compounds is shielded by silica nanospheres. 相似文献
A facile wet route was applied to prepare a series of chalcogenide semiconductor nanocrystals (see figure) in controllable shapes and sizes, while a general bottom‐up approach was adopted to transform these cyclohexane‐soluble monodisperse nanocrystals into water‐soluble colloidal spheres.
Reactions of M+(H2O)n (M=V, Cr, Mn, Fe, Co, Ni, Cu, Zn; n≤40) with NO were studied by Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometry. Uptake of NO was observed for M=Cr, Fe, Co, Ni, Zn. The number of NO molecules taken up depends on the metal ion. For iron and zinc, NO uptake is followed by elimination of HNO and formation of the hydrated metal hydroxide, with strong size dependence. For manganese, only small HMnOH+(H2O)n?1 species, which are formed under the influence of room‐temperature black‐body radiation, react with NO. Here NO uptake competes with HNO formation, both being primary reactions. The results illustrate that, in the presence of water, transition‐metal ions are able to undergo quite particular and diverse reactions with NO. HNO is presumably formed through recombination of a proton and 3NO? for M=Fe, Zn, preferentially for n=15–20. For manganese, the hydride in HMnOH+(H2O)n?1 is involved in HNO formation, preferentially for n≤4. The strong size dependence of the HNO formation efficiency illustrates that each molecule counts in the reactions of small ionic water clusters. 相似文献
Polycrystalline intercalated TiMxH2−nx(PO4)2· yC3H7NH2·wH2O compounds with transition metal (TM) ions (Mn+ = Co2+, Ni2+, Fe3+ or Cr3+) have been prepared by means of an indirect route and characterised using X-ray diffraction, scanning electron microscopy, chemical and thermal analysis, X-ray absorption and magnetic measurements. These novel pillared layered materials, which were obtained from the monoclinic (P21/c space group) α-Ti(HPO4)2·H2O phase, lose its crystallinity after intercalation. However all the TM ions are octahedrally surrounded by 6 oxygen atoms, although the X-ray absorption spectra evidence a clear dependence on the temperature. Surprisingly, all the materials behave as paramagnetic down to 1.5 K, but they exhibit different colours, what means that they are optically active (Co2+: violet; Ni2+: pale green; Fe3+: yellow; Cr3+: dark green). 相似文献