Phase stability,elastic, anisotropic and thermodynamic properties of HoT2Al20 (T = Ti,V, Cr) intermetallic cage compounds

The structural stability, elastic properties, anisotropy, dynamics stability and thermodynamics properties were explored for pure Al and HoT₂Al₂₀ intermetallics from the first-principles method. The formation enthalpy and phonon frequencies indicate that these HoT₂Al₂₀ intermetallics maintain structural stability. The elastic constants C_ijs and moduli B, G, E and H_v indicate these intermetallics possess higher hardness and the better resistance to deformation. The values of Poisson’s ratio and B/G demonstrate that HoT₂Al₂₀ intermetallics are brittle materials. The anisotropic constants and anisotropic acoustic velocities confirm that HoT₂Al₂₀ intermetallics exhibit anisotropic properties. Importantly, the calculated thermal quantities demonstrate that these new HoT₂Al₂₀ intermetallics possess the better thermodynamic properties at high temperature.     

New coordination polymers based on a novel polynitrile ligand: Synthesis,structure and magnetic properties of the series [M(tcnoetOH)2(4,4′-bpy)(H2O)2] (tcnoetOH− = [(NC)2CC(OCH2CH2OH)C(CN)2]−; M = Fe,Co and Ni)

A novel polynitrile anionic ligand, tcnoetOH^?(=[(NC)₂CC(OCH₂CH₂OH)C(CN)₂]^?), has been synthesized by a one-pot reaction from a cyclic acetal and malononitrile. This ligand has been successfully used to prepare, with 4,4′-bpy as co-ligand, a novel series of coordination polymers formulated as [M(tcnoetOH)₂(4,4′-bpy)(H₂O)₂] with M(II) = Fe (1), Co (2) and Ni (3). These isostructural compounds present a linear chain structure consisting of octahedrally coordinated metal ions bridged by trans 4,4′-bpy ligands. The coordination sphere of the metal ions is completed with two terminal tcnoetOH^? ligand and two water molecules. The magnetic properties indicate that the three compounds are paramagnetic, as expected from the long 4,4′-bpy bridge connecting the metal atoms. Their magnetic properties have been fitted with a model of isolated ions including a zero field splitting for the Fe(II) and Ni(II) derivatives.     

MCl2 (M=Hg,Cd, Zn,Mn) catalysed hydrochlorination of acetylene – a Density Functional Theory study

A Density Functional Theory method has been employed in this research to conduct an in-depth study of the correlation between the conversion of acetylene to vinyl chloride catalysed by MCl₂ (M=Hg, Cd, Zn, Mn) and the electron affinity. From the analysis of the adsorption energy and energy profile of acetylene hydrochlorination reaction, combined with Fukui indices and outer-shell Mulliken population change alongside reaction pathway, it can be concluded that, the outermost electron migration is the main factor affecting the catalytic property of MCl₂ (M=Hg, Cd, Zn, Mn) catalyst. The Mulliken population change of the central atom M²⁺ (M=Hg, Cd, Zn) share similar tendency along the reaction pathway, the only difference is Hg²⁺ gained more electrons than the other two when acetylene got absorbed, and that proved that Hg(II) got better electron withdrawing, which is a main motivator of better catalytic properties in acetylene hydrochlorination reaction.     

A B3LYP and MP2(full) theoretical investigation into the cooperativity effect between dihydrogen-bonding and H–M∙∙∙π (M = Li, Na, K) interactions among HF, MH with the π-electron donor C2H2, C2H4 or C6H6

The DFT-B3LYP/6-311++G(3df,2p) and MP2(full)/6-311++G(3df,2p) calculations were carried out on the binary complex formed by HM (M?=?Li, Na, K) and HF or the π-electron donor (C₂H₂, C₂H₄, C₆H₆), as well as the ternary system FH???HM???C₂H₂/C₂H₄/C₆H₆. The cooperativity effect between the dihydrogen-bonding and H–M???π interactions was investigated. The result shows that the equilibrium distances R _H???H and R _M???π in the ternary complex decrease and both the H???H and H–M???π interactions are strengthened when compared to the corresponding binary complex. The cooperativity effect of the dihydrogen bond on the H–M???π interaction is more pronounced than that of the M???π bond on the H???H interaction. Furthermore, the values of cooperativity effect follow the order of FH???HNa???π?>?FH???HLi???π?>?FH???HK???π and FH???HM???C₆H₆?>?FH???HM???C₂H₄?>?FH???HM???C₂H₂. The nature of the cooperativity effect was revealed by the analyses of the charge of the hydrogen atoms in H???H moiety, atom in molecule (AIM) and electron density shifts methods.

Syntheses and michael additions to vinylidene diphosphine complexes of type [M(CO)4{(Ph2P)2CCH2}] (MCr,Mo or W)

Treatment of [M(CO)₄Ph₂PCHPPh₂]⁻ with CH₃- OCH₂Cl at 20 °C gave the methoxymethyl derivations [M(CO)₄{Ph₂PCH(CH₂OCH₃)PPh₂}] (MCr or W), but a similar treatment at 80 °C gave derivatives of a vinylidene diphosphine [M(CO)₄(Ph₂P)₂C CH₂]. Treatment of [M(CO)₄Ph₂PCHPPh₂]⁻with CH₃CHClOCH₃ at 20 or 80 °C gave only [M(CO)₄- (Ph₂P)₂CHCH(CH₃)OCH₃] (MCr or W). The vinylidene diphosphine complexes [M(CO)₄(Ph₂P)2- CCH₂] (MCr, Mo or W) were even more easily prepared by treating [M(CO)₆] with (Ph₂P)₂CCH₂ (vdpp) in hot solvents such as CH₃OCH₂CH₂OCH₂- CH₂OCH₃.Treatment of [W(CO)₄vdpp] with LiBuⁿ followed by methanol gave [W(CO)₄(Ph₂P)₂CHCH₂Buⁿ] (1c), i.e. conjugate addition to the CCH₂ occurs. 1c was also made by treating [W(CO)₄(Ph₂P)₂CH]⁻ with n-pentyl-iodide. Similarly LiMe was added to [W(CO)₄(Ph₂P)₂CCH₂]. Treatment of [M(CO)₄- vdpp] with NaCH(COOEt)₂ gave [M(CO)₄(Ph₂- P)₂CHCH₂CH(COOEt)₂] (MW or Mo). Pyrrolidine added to the CCH₂ bonds of [M(CO)₄vddp] to give [M(CO)₄(Ph₂P)₂CHCH₂NC₄H₈]. ³¹p and ¹H NMR and IR data are given.     

Synthesis of heterodinuclear FeRu(CO)6(R-DAB(6e))(R-DABRNC(H)C(H)NR) Part XV. Comparison of the reactivities of heterodinuclear FeRu(CO)6(R-DAB(6e)) and homodinuclear analogues M2(CO)6(R-DAB(6e)) (M = Fe,Ru). Single-crystal x-ray structures of FeRu(CO)6(i-Pr-DAB(6e)) and FeRu(CO)5(i-Pr-DAB(4e))(C3H4)

The reactions of Fe(CO)₃(R-DAB; R¹, H(4e)) (1a: R = i-Pr, R¹ = H; 1b: R = t-Bu, R¹ = H; 1c: R = c-Hex, R¹ = H; 1e: R = p-Tol, R¹ = H; 1f: R = i-Pr, R¹ = Me) with Ru₃(CO)₁₂ and of Ru(CO)₃(R-DAB; R¹, H(4e)) (2a: R = i-Pr, R¹ = H; 2d: R = CH(i-Pr)₂, R¹ = H) with Fe₂(CO)₉ in refluxing heptane both afforded FeRu(CO)₆(R-DAB; R¹, H(6e)) (3) in yields between 50 and 65%.The coordination mode of the ligand has been studied by a single crystal X-ray structure determination of FeRu(CO)₆(i-Pr-DAB(6e)) (3a). Crystals of 3a are monoclinic, space group P2₁/a, with four molecules in a unit cell of dimensions: a = 22.436(3), b = 8.136(3), c = 10.266(1) Å and β = 99.57(1)°. The structure was refined to R = 0.049 and R_w = 0.052 using 3045 reflections above the 2.5σ(I) level. The molecule contains an FeRu bond of 2.6602(9) Å, three terminally bonded carbonyls to Fe, three terminally bonded carbonyls to Ru and bridging 6e donating i-Pr-DAB ligand. The i-Pr-DAB ligand is coordinated to Ru via N(1) and N(2) occupying an apical and equatorial site respectively (RuN(1) = 2.138(4) RuN(2) = 2.102(3) Å). The C(2)N(2) moiety of the ligand is η²-coordinated to Fe with C(2) in an apical and N(2) in an equatorial site (FeC(2) = 2.070(5) and FeN(2) = 1.942(3) Å).The ¹H and ¹³C NMR data indicate that in all FeRu(CO)₆(R-DAB(6e)) complexes (3a to 3f) exclusively η²-CN coordination to the Fe atom and not to the Ru atom is present irrespective of whether 3 was prepared by reaction of Fe(CO)₃(R-DAB(4e)) (1) with Ru₃(CO)₁₂ or by reaction of Ru(CO)₃(R-DAB(4e)) (2) with Fe₂(CO)₉. In the case of FeRu(CO)₆(i-Pr-DAB; Me, H(6e)) (3f) the NMR data show that only the complex with the C(Me)N moiety of the ligand σ-N coordinated to the Ru atom and the C(H)N moiety η²-coordinated to the Fe atom was formed. Variable temperature NMR experiments up to 140 °C showed that the α-diimine ligand in 3a is stereochemically rigid bonded.FeRu(CO)₆(R-DAB(6e)) (3a and 3e) reacted with allene to give FeRu(CO)₅(R-DAB(4e))(C₃H₄) (4a and 4e). A single crystal X-ray structure determination of FeRu(CO)₅(i-Pr-DAB(4e))(C₃H₄) (4a) was performed. Crystals of 4a are triclinic, space group P1, with two molecules in a unit cell of dimensions: a = 9.7882(7), b = 12.2609(9), c = 8.3343(7) Å, α = 99.77(1)°, β = 91.47(1)° and γ = 86.00(1)°. The structure was refined to R = 0.028 and R_w = 0.043 using 4598 reflections above the 2σ(I) level. The molecule contains an FeRu bond of 2.7405(7) Å and three terminally bonded carbonyls to iron. Two carbonyls are terminally bonded to the Ru atom together with a chelating 4e donating i-Pr-DAB ligand [RuN = 2.110(1) (mean)]. The allene ligand is coordinated in an η³-allylic fashion to the Fe atom while the central carbon of the allene moiety is σ-bonded to the Ru atom (FeC(14) = 2.166(3), FeC(15) = 1.970(2), FeC(16) = 2.127(3) and RuC(15) = 2.075(2) Å). The ¹H and ¹³C NMR data show that in solution the coordination modes of the R-DAB and the allene ligands are the same as in the solid state.Thermolysis reactions of 3a with R-DAB or carbodiimides gave decomposition and did not afford C(imine)C(reactant) coupling products. Thermolysis reactions of 3a with M₃(CO)₁₂ (M = Ru, Os) and Me₃NO gave decomposition. When the reaction of 3a with Me₃NO was performed in the presence of dimethylacetylenedicarboxylate (DMADC) the known complex FeRu(CO)₄(i-Pr-DAB(8e))(DMADC) (5a) was formed in low yield. In 5a the R-DAB ligand is in the 8e coordination mode with both the imine bonds η²-coordinated to iron. The acetylene ligand is coordinated in a bridging fashion, parallel with the FeRu bond.     

Distribution of micro- (Fe,Zn, Cu,and Mn) and risk (Al,As, Cr,Ni, Pb,and Cd) elements in the organs of Rumex alpinus L. in the Alps and Krkonoše Mountains

Plant and Soil - Rumex alpinus is a native plant in the mountains of Europe whose distribution has partly been affected by its utilization as a vegetable and medicinal herb. The distribution of...     

The effect of deleting residue C269 in the β12-β13 loop of protein phosphatase 2A (PP2A)catalytic subunit on the interaction between PP2A and metal ions, especially Mn(2+)

Protein phosphatase 2A (PP2A) is one of the most important Ser/Thr phosphatases in eukaryotic cells. The enzymatic core of PP2A (PP2A(D)) consists of a scaffold subunit (A subunit) and a catalytic subunit (C subunit). When residue Cys269 in the β12-β13 loop of the PP2A C subunit was deleted (ΔC269), the activity and the intrinsic fluorescence intensity of PP2A(D) decreased. Specify the effects of some metal ions on PP2A(D) were also changed. Mn(2+) in particular was an efficient activator of ΔC269 and altered the intrinsic fluorescence spectrum of ΔC269. Remarkably, after pre-treatment of ΔC269 with Mn(2+), the effects of other metal ions showed the same trends as they had on the WT. Molecular dynamics (MD) simulations showed that deletion of Cys269 decreased the polarity of the β12-β13 loop of PP2A Cα. We conclude that deletion of residue Cys269 alters the conformation and activity of PP2A(D) and influences the interaction between PP2A and various metal ions, notably Mn(2+).     

DFT study on the reactions of ClO–/BrO– with RCl (R = CH3, C2H5, and C3H7) in gas phase

Gas-phase reactions of ClO^–/BrO^– with RCl (R = CH₃, C₂H₅, and C₃H₇) have been investigated in detail using the popular DFT functional BHandHLYP/aug-cc-pVDZ level of theory. As a result, our findings strongly suggest that the type of reaction is firstly initiated by a typical S_N2 fashion. Subsequently, two competitive substitution steps, named as S_N2-induced substitution and S_N2-induced elimination, respectively, would proceed before the initial S_N2 product ion-dipole complex separates, in which the former exhibits less reactivity than the latter. Those are consistent with relevant experimental results. Moreover, we have also explored reactivity difference for the title reactions in term of some factors derived from methyl group, p-π electronic conjugation, ionization energy (IE), as well as molecular orbital (MO) analysis.

Synthesis of [{Os3(CO)10(μ2-H)}2{μ2,μ2-NC6H4C6H4N}] and [{Os3(CO)9(μ2-H)PPh3}2{μ2,μ2-NC6H4C6H4N}]: Carbon–carbon bond formation promoted by organorhodium species

Synthesis and characterization of linked cluster [{Os₃(CO)₁₀(μ₂-H)}₂{μ₂,μ₂-NC₆H₄C₆H₄N}] (1) from the reaction of [Os₃Rh(μ-H)₃(CO)₁₂] with aniline in the presence of an excess amount of 4-vinyl phenol in refluxing heptane is reported. A similar reaction with [Os₃(CO)₁₀(NCMe)₂] as starting material gave a known compound, [Os₃(CO)₁₀(μ₂-H)(μ₂-HNC₆H₅)] (2). The treatment of complexes 1 and 2 with Wilkinson’s catalyst in refluxing heptane respectively, yielded [{Os₃(CO)₉(μ₂-H)PPh₃}₂{μ₂,μ₂-NC₆H₄C₆H₄N}] (3). An interesting and unexpected C–C coupling of phenyl-amido ligands was observed in complexes 1 and 3, which is believed to be catalysed by the organometallic rhodium species. The newly synthesized compounds 1 and 3 were fully characterized by IR, ¹H NMR spectroscopy, mass spectroscopy, elemental analysis, and X-ray crystallography. Both structures 1 and 3 comprise two triangles of osmium atoms. The two triangular osmium metal cores are linked by a bi-amido ligand via the two nitrogen atoms N(1) and N(1)* and N(1) and N(2), at their equatorial sites. The electronic absorption spectra of complexes 1, 2, and 3 display both low energy absorption, dπ (Os) → π* (amido) metal-to-ligand charge-transfer (MLCT) transition, and π → π* intra-ligand electronic transitions of the amido and bi-amido ligands.     

Core-dependent and ligand-dependent relativistic corrections to the nuclear magnetic shieldings in MH4−n Y n (n = 0–4; M = Si,Ge, Sn,and Y = H,F, Cl,Br, I) model compounds

The spatial geometry and local environment of hydroxyl groups of the cis-vacant (cv) crystal polymorph of dioctahedral 2:1 phyllosilicates are studied by computational methods, doing especial emphasis on the hydrogen bonds and electrostatic interactions of the hydroxyl groups with the neighbor atoms. Different types of phyllosilicates are explored: with only tetrahedral charge, with only octahedral charge, with simultaneous octahedral and tetrahedral substitution, and with different interlayer cation (IC). The effect of these interactions on the spectroscopic properties of these hydroxyl groups is also studied. All results are compared with the trans-vacant (tv) crystal forms of these minerals. Frequency differences between cv and tv polymorphs are smaller than those due to the local environments of these OH groups. This means that the changes in the interactions of the different local environments of each OH group are greater than the cv/tv differences.