Planarity takes over in the C(x)H(x)P(6-x) (x = 0-6) series at x = 4

In this work we examine a structural transition from non-planar three-dimensional structures to planar benzene-like structures in the C(x)H(x)P(6-x) (x = 0-6) series. The global minima of P(6), CHP(5), and C(2)H(2)P(4) species are benzvalene-like structures. The benzvalene and benzene-like structures of C(3)H(3)P(3) are close in energy with the former being slightly more stable at our best level of theory. The transition occurs at x = 4 (C(4)H(4)P(2)), where the benzene-like structures become significantly more stable than the benzvalene-like structures. We show that the pseudo Jahn-Teller effect, which is responsible for the deformation of planar P(6), CHP(5), and C(2)H(2)P(4) structures, is completely suppressed at x = 3 (benzene-like structures of C(3)H(3)P(3)). We present NICS(zz) values of all the benzene-like isomers in the series.     

Theoretical probing of deltahedral closo-auroboranes B(x)Au(x)2- (x = 5-12)

Using density functional theory calculations, here we show that a series of B(x)Au(x)2- (x = 5-12) dianions possesses structure and bonding similar to the famous deltahedral closo-borane cages, B(x)H(x)2-. Effective atomic charges on Au in B(x)Au(x)2- are very similar to those on H in B(x)H(x)2-, indicating that Au in the closo-auroboranes is indeed analogous to H in the closo-boranes. The present theoretical predictions of B(x)Au(x)2- suggest that the closo-auroborane species are viable new chemical building blocks that may be synthesized in bulk. The Au atoms in the closo-auroboranes represent highly atomically dispersed Au and may potentially exhibit novel catalytic and chemical properties.     

Dimensions of the Ozonide Anion in M([18]crown‐6)O3·x NH3 with M = K (x = 2), Rb (x = 1) and Cs (x = 8)

Reaction of alkali metal ozonides (KO₃, RbO₃ and CsO₃) with [18]crown‐6 in liquid ammonia yields compounds of the composition M([18]crown‐6)O₃·x NH₃ with M = K (x = 2), Rb (x = 1) and Cs (x = 8). The large intermolecular distance between adjacent radical anions in these compounds leads to almost ideal paramagnetic behavior according to Curie's law. Discrepancies concerning the structure of the ozonide anions in the K and Cs compound compared to a former investigation on Rb([18]crown‐6)O₃·NH₃ have been resolved by means of DFT calculations and a single‐crystal structure redetermination.     

Aminotroponiminatogermaacid halides with a ge(e)x moiety (e = s, se; x = f, cl)

Fluorination of aminotroponiminate (ATI) ligand-stabilized germylene monochloride [(t-Bu)(2)ATI]GeCl (1) with CsF gave the aminotroponiminatogermylene monofluoride [(t-Bu)(2)ATI]GeF (2). Oxidative addition reaction of compound 2 with elemental sulfur and selenium led to isolation of the corresponding germathioacid fluoride [(t-Bu)(2)ATI]Ge(S)F (3) and germaselenoacid fluoride [(t-Bu)(2)ATI]Ge(Se)F (4), respectively. Similarly, reaction of aminotroponiminatogermylene monochloride [(i-Bu)(2)ATI]GeCl (9) with elemental sulfur and selenium gave the aminotroponiminatogermathioacid chloride [(i-Bu)(2)ATI]Ge(S)Cl (11) and aminotroponiminatogermaselenoacid chloride [(i-Bu)(2)ATI]Ge(Se)Cl (12), respectively. Compound 9 has been prepared through a multistep synthetic route starting from 2-(tosyloxy)tropone 5. All compounds (2-4 and 6-12) were characterized through the multinuclear NMR spectroscopy, and single-crystal X-ray diffraction studies were performed on compounds 2, 4, and 8-12. The germaselenoacid halide complexes 4 and 12 showed doublet (-142.37 ppm) and singlet (-213.13 ppm) resonances in their (77)Se NMR spectra, respectively. Germylene monohalide complexes 2 and 9 have a germanium center in distorted trigonal pyramidal geometry, whereas a distorted tetrahedral geometry is seen around the germanium center in germaacid halide complexes 4, 11, and 12. The length of the Ge═E bond in germathioacid chloride (11) and germaselenoacid halide (4 and 12) complexes is 2.065(1) and 2.194(av) ?, respectively. Theoretical studies (based on the DFT methods) on complexes 4, 11, and 12 reveal the nature of the Ge═E multiple bond in these germaacid halide complexes with computed Wiberg bond indices (WBI) being 1.480, 1.508, and 1.541, respectively.     

TiHx(x=2,3,4)的从头计算研究

过渡金属氢化物分子与诸多催化过程密切相关[1].而过渡金属氢化物本身是一种颇有潜力的能源材料,即贮氢材料,如钛系、钒系贮氢材料在工业上已得到了广泛的应用 [2].但对于金属与氢的相互作用的机理研究的报道甚少.     

Zwei neue basische Yttrium-Nitrate: Y(OH) x (NO3)3−x ·H2O und YO x/2(NO3)3−x (x=1.5)

Summary The intermediate precipitate, resulting by thermal decomposition and stepwise hydrolysis of yttrium-nitrate, was investigated by chemical analysis, TG, IR, and X-ray powderdiagrams and was found to be a definite hydroxynitrate Y(OH)_1.5(NO₃)_1.5·H₂O. Thermal decomposition resulted in the oxynitrate YO_0.75(NO₃)_1.5, stable from 140–280°C, which was characterized in an analogous manner.

     

Hydrothermal synthesis, thermal, and magnetic data on new alkaline vanadium phosphate My(VO)9 + x(PO4)4x(HPO4)12 - 4x with M = Cs+ (y = 5.29, x = 1) and M = NH4+, Rb+ (y approximately 5, x approximately 1)

Brownish platelet crystals of My(VO)9 + x(PO4)4x(HPO4)12 - 4x (M = Cs+, NH4+ and Rb+) were prepared hydrothermally. The structure of Cs approximately 5(VO)10(PO4)4(HPO4)8 was solved from single-crystal X-ray diffraction data in the centrosymmetric monoclinic space group C2/c (No. 15) a = 21.1951(8) A, b = 12.2051(4) A, c = 20.6230(8) A, beta = 109.742(2) degrees, Z = 4 (R1(Fo) = 0.054, wR2(Fo2) = 0.123). The structure of Cs approximately 5(VO)10(PO4)4(HPO4)8 is described and compared to that of K2(VO)3(HPO4)4 previously reported by Lii. For the three compounds, thermogravimetric data and susceptibility measurements were investigated and were found to be in agreement with the structural study.     

Structural and Spectroscopic Studies of [M((x)tu)4]+ Systems (M = Cu,Ag; (x)tu = (substituted) Thiourea)

In a low‐temperature redetermination of improved precision of the structure of [Cu(tu)₄]₂(SiF₆) (‘tu’ = thiourea, SC(NH₂)₂), Cu–S range between 2.3173–2.3433(8), < > 2.336(11) Å, with S–Cu–S 92.72(3)–118.75(12)°. The first structure determination of a 1:4 adduct of a silver(I) salt with a (substituted) thiourea ligand is also reported, for silver(I) nitrate with ‘ethylenethiourea’, (‘etu’ = SC(NHCH₂)₂), as a monohydrate [Ag(etu)₄](NO₃)·H₂O, wherein Ag–S range between 2.544–2.637(2), < > 2.59(4) Å, S–Ag–S 87.88–117.57(7)°. Bands in the far‐IR spectra of these compounds are assigned to ν(MS) modes, and the frequencies are compared with those predicted by previously established correlations between ν(MS) and the M–S bond length d(MS) for copper or silver complexes with tu or etu ligands.     

Boron-induced hydrogen localization in the novel metal hydride LaNi(3)BH(x) (x = 2.5-3.0)

The crystal structure and hydrogenation properties of the intermetallic boride LaNi(3)B were investigated. The hydrogen-free compound has a novel structure with orthorhombic symmetry, space group Imma, a = 4.9698(8) A, b = 7.1337(8) A, c = 8.3001(9) A, and V = 294.26(7) A(3). Thermal gravimetrical analysis reveals a hydride phase that forms near ambient conditions within the compositional range LaNi(3)BH(2.5)(-)(3.0). Single-crystal X-ray diffraction on both the alloy and the hydride, using the same crystal, shows an expansion in the a-c plane (by up to approximately 8%) and a contraction along b (by approximately 3%), while the symmetry changes from Imma to Bmmb (Cmcm) and the unit cell doubles along a and b. The cell parameters for the composition of LaNi(3)BD(2.73(4)) are a = 10.7709(7) A, b = 16.0852(10) A, c = 7.6365(5) A, V = 1323.03(15) A(3), and space group Cmcm. Four nearly fully occupied interstitial hydrogen sites were located by neutron powder diffraction on deuterides and found to have tetrahedral, La(2)Ni(2) (D1,D2), trigonal-prismatic, La(3)Ni(3) (D3), and trigonal-bipyramidal, La(2)Ni(3) (D4), metal environments. The structure can also be described in terms of alternating quasi two-dimensional [NiD](-) slabs (Ni-D = 1.62-1.97 A) and La-B sheets for which bond-valence sums suggest the limiting formula La(3+)B(0)[Ni(3)D(3)](3)(-). The La-B planes do not accommodate deuterium; the B-D and D-D interactions appear to be repulsive. The shortest B-D and D-D contacts are 2.52(2) and 2.33(2) A, respectively.     

Composition-structure relationships in polar intermetallics: experimental and theoretical studies of LaNi(1 + x)Al(6 - x) (x = 0.44)

A new ternary aluminide, LaNi(1 + x)Al(6 - x ) (x = 0.44), has been synthesized from La, Ni, and Al in sealed silica tubes. Its structure, determined by single-crystal X-ray diffraction, is tetragonal P4/mmm (No. 123) with Z = 1 and has the lattice parameters a = 4.200(8) and c = 8.080(8) angstroms. Refinement based on Fo2 yielded R1 = 0.0197 and wR2 = 0.020 [I > 2sigmaI]. The compound adopts a structure type previously observed in SrAu2Ga5 and EuAu2Ga5. The atomic arrangement is closely related to the one in BaAl4 as well as in other rare-earth gallide compounds such as LaNi0.6Ga6, HoCoGa5, Ce4Ni2Ga20, Ce4Ni2Ga17, Ce4NiGa18, and Ce3Ni2Ga15. This structure exhibits a large open cavity which may be filled by a guest atom. Band structure calculations using density functional theory have been carried out to understand the stability of this new compound.     

Electron-precise/deficient La(5-x)Ca(x)Ge4 (3.4 < or = x < or = 3.8) and Ce(5-x)Ca(x)Ge4 (3.0 < or = x < or = 3.3): probing low-valence electron concentrations in metal-rich Gd5Si4-type germanides

We report for the first time the syntheses of electron-precise/deficient alloys, Ln5-xCaxGe4 (Ln = La, Ce; x = 3.37, 3.66, 3.82 for La; x = 3.00, 3.20, 3.26 for Ce), in the metal-rich R5Tt4 Zintl system (R = rare earth metal; Tt = Si, Ge). The new alloys extend the phase width from electron-rich to open-shell electron-deficient region in the metal-rich Zintl system and demonstrate possible occurrence of varied electron deficiencies in Zintl phases without structural changes, as a result of other existing structure-forming factors.     

Atmospheric chemistry of n-C(x)F(2)(x)(+1)CHO (x = 1, 2, 3, 4): fate of n-C(x)F(2)(x)(+1)C(O) radicals

Smog chamber/FTIR techniques were used to study the atmospheric fate of n-C(x)F(2)(x)(+1)C(O) (x = 1, 2, 3, 4) radicals in 700 Torr O(2)/N(2) diluent at 298 +/- 3 K. A competition is observed between reaction with O(2) to form n-C(x)()F(2)(x)()(+1)C(O)O(2) radicals and decomposition to form n-C(x)F(2)(x)(+1) radicals and CO. In 700 Torr O(2)/N(2) diluent at 298 +/- 3 K, the rate constant ratio, k(n-C(x)F(2)(x)(+1)C(O) + O(2) --> n-C(x)F(2)(x)(+1)C(O)O(2))/k(n-C(x)F(2)(x)(+1)C(O) --> n-C(x)F(2)(x)(+1) + CO) = (1.30 +/- 0.05) x 10(-17), (1.90 +/- 0.17) x 10(-19), (5.04 +/- 0.40) x 10(-20), and (2.67 +/- 0.42) x 10(-20) cm(3) molecule(-1) for x = 1, 2, 3, 4, respectively. In one atmosphere of air at 298 K, reaction with O(2) accounts for 99%, 50%, 21%, and 12% of the loss of n-C(x)F(2)(x)(+1)C(O) radicals for x = 1, 2, 3, 4, respectively. Results are discussed with respect to the atmospheric chemistry of n-C(x)F(2)(x)(+1)C(O) radicals and their possible role in contributing to the formation of perfluorocarboxylic acids in the environment.     

Gadolinium-based mixed-metal nitride clusterfullerenes Gd(x)Sc(3-x)N@C80 (x=1, 2).

The first gadolinium-based mixed-metal nitride clusterfullerenes Gd(x)Sc(3-x)N@C(80) (I) (1, x=2; 2, x=1) have been successfully synthesized by the reactive gas atmosphere method and isolated facilely by recycling high-performance liquid chromatography (HPLC). The sum yield of 1 and 2 is 30-40 times higher than that of Gd(3)N@C(80) (I). Moreover, an enhanced relative yield of 2 over the Sc(3)N@C(80) (I) is achieved under the optimized synthesis conditions. According to the UV/Vis/NIR spectroscopic characterization, 1 and 2 are both stable fullerenes with large optical band-gaps while 1 has higher similarity to Gd(3)N@C(80) (I) and 2 resembles Sc(3)N@C(80) (I). The vibrational structures of 1 and 2 are studied by Fourier-transform infrared (FTIR) spectroscopy as well as density functional theory (DFT) computations. In particular, the structures of the encaged Gd(x)Sc(3-x)N clusters within 1 and 2 are analyzed.     

Ab initio chemical kinetics for SiH3 reactions with Si(x)H2x+2 (x = 1-4)

Gas-phase kinetics and mechanisms of SiH(3) reactions with SiH(4), Si(2)H(6), Si(3)H(8), and Si(4)H(10), processes of relevance to a-Si thin-film deposition, have been investigated by ab initio molecular orbital and transition-state theory (TST) calculations. Geometric parameters of all the species involved in the title reactions were optimized by density functional theory at the B3LYP and BH&HLYP levels with the 6-311++G(3df,2p) basis set. The potential energy surface of each reaction was refined at the CCSD(T)/6-311++G(3df,2p) level of theory. The results show that the most favorable low energy pathways in the SiH(3) reactions with these silanes occur by H abstraction, leading to the formation of SiH(4) + Si(x)H(2x+1) (silanyl) radicals. For both Si(3)H(8) and n-Si(4)H(10) reactions, the lowest energy barrier channels take place by secondary Si-H abstraction, yielding SiH(4) + s-Si(3)H(7) and SiH(4) + s-Si(4)H(9), respectively. In the i-Si(4)H(10) reaction, tertiary Si-H abstraction has the lowest barrier producing SiH(4) + t-Si(4)H(9). In addition, direct SiH(3)-for-X substitution reactions forming Si(2)H(6) + X (X = H or silanyls) can also occur, but with significantly higher reaction barriers. A comparison of the SiH(3) reactions with the analogous CH(3) reactions with alkanes has been made. The rate constants for low-energy product channels have been calculated for the temperature range 300-2500 K by TST with Eckart tunneling corrections. These results, together with predicted heats of formation of various silanyl radicals and Si(4)H(10) isomers, have been tabulated for modeling of a-Si:H film growth by chemical vapor deposition.     

Chemical size effect on the magnetic and electrical properties in the (Tb(1-)(x)Eu(x))MnO(3) (0 < or = x < or = 1.0) system

The effect of isovalent chemical substitution of Eu3+ into the Tb3+ sites on the magnetic and electrical properties of (Tb1-xEux)MnO3 (0 相似文献   

Structure of the Na(x)Cl(x+1) (-) (x=1-4) clusters via ab initio genetic algorithm and photoelectron spectroscopy

The application of the ab initio genetic algorithm with an embedded gradient has been carried out for the elucidation of global minimum structures of a series of anionic sodium chloride clusters, Na(x)Cl(x+1) (-) (x=1-4), produced in the gas phase using electrospray ionization and studied by photoelectron spectroscopy. These are all superhalogen species with extremely high electron binding energies. The vertical electron detachment energies for Na(x)Cl(x+1) (-) were measured to be 5.6, 6.46, 6.3, and 7.0 eV, for x=1-4, respectively. Our ab initio gradient embedded genetic algorithm program detected the linear global minima for NaCl(2) (-) and Na(2)Cl(3) (-) and three-dimensional structures for the larger species. Na(3)Cl(4) (-) was found to have C(3v) symmetry, which can be viewed as a Na(4)Cl(4) cube missing a corner Na(+) cation, whereas Na(4)Cl(5) (-) was found to have C(4v) symmetry, close to a 3x3 planar structure. Excellent agreement between the theoretically calculated and the experimental spectra was observed, confirming the obtained structures and demonstrating the power of the developed genetic algorithm technique.     

Inorganic single wall nanotubes of SbPS(4-x)Se(x) (0 < or = x < or = 3) with tunable band gap

A new ternary member, SbPS4, has been added to the growing inorganic nanotube family. This material naturally forms bundles of long, single wall nanotubes.     

Syntheses and structural characterizations of the octahedral boride clusters [Rh2Ru4H(CO)16−2x (nbd) x B] (x=1,2) and gold(I) phosphine derivatives (nbd=norbornadiene)

The reaction of less than one equivalent of [Rh₂Cl₂(nbd)₂] with [Ru₄H(CO)₁₂BH]⁻, which contains a semi-interstitial boron atom, yields the heterometallic boride clustercis-[Rh₂Ru₄H(CO)₁₂(nbd)₂B] which has been characterized by spectroscopic and X-ray diffraction methods. The cluster has an octahedral core, consistent with an 86 electron count. Deprotonation yields the conjugate basecis-[Rh₂Ru₄(CO)₁₂(nbd)₂B]⁻ which has been isolated and fully characterized as the [(Ph₃P)₂N]⁺ salt. There is little structural perturbation upon going fromcis-[Rh₂Ru₄H(CO)₁₂(nbd)₂B] tocis-[Rh₂Ru₄(CO)₁₂(nbd)₂B]⁻ and neither cluster shows a tendency for the formation of thetrans skeletal isomer in contrast to the analogous carbonyl clustercis-[Rh₂Ru₄(CO)₁₆B]⁻. If the reaction of [Rh₂Cl₂(nbd)₂] with [Ru₄H(CO)₁₂BH]⁻ is allowed to proceed for 30 min and [R ₃PAuCl] (R=Ph, C₆H₁₁, 2-MeC₆H₄) is then added, the clusterscis-[Rh₂Ru₄(CO)₁₂(nbd)₂B(AuPR₃)] andcis-[Rh₂Ru₄(CO)₁₄(nbd)B(AuPR₃)] are formed in yields that are dependent upon the initial reaction period. The single crystal structures ofcis-[Rh₂Ru₄(CO)₁₂(nbd)₂B(AuPPh₃)] andcis-[Rh₂Ru₄(CO)₁₄(nbd)B(AuPPh₃)] are reported. In contrast to their all-carbonyl analoguescis-[Rh₂Ru₄(CO)₁₆B(AuPR ₃)] (R=Ph or C₆H₁₁), the nbd derivatives do not undergocis →trans skeletal isomerism.