Pb3+ radiation defects in Ca9Pb(PO4)6(OH)2 hydroxyapatite nanoparticles studied by high-field (W-band) EPR and ENDOR

W-band pulsed EPR and ENDOR investigations of X-ray irradiated nanoparticles of synthetic hydroxyapatite Ca(9)Pb(PO(4))(6)(OH)(2) are performed. It is shown that in the investigated species lead ions probably replace the Ca(1) position in the hydroxyapatite structure.     

9,10-Anthracene dicarboxylate bridged complexes with M2 quadruply bonded dimetal units: [[M2(O2CtBu)3]2(mu-9,10-An(CO2)2)], where M = Mo or W

From the reactions between [M2(O2CtBu)4] and 9,10-anthracenedicarboxylic acid in toluene, the dicarboxylate bridged complexes [[M2(O2CtBu)3]2(mu-9,10An(CO2)2)], have been obtained as microcrystalline yellow (M = Mo) and red (M = W) powders. The powders are soluble in THF forming intense red (M = Mo) and green (M = W) solutions. The electronic absorption spectra in 2-MeTHF have been recorded as a function of temperature (2-298 K) and show a small bathochromic shift on cooling. The electronic structures have been investigated by molecular orbital calculations employing density functional theory on the model compounds [(HCO2)3M2]2(mu-9,10-An(CO2)2) where the M4 unit is constrained to lie in a plane. These reveal a minimum energy, gas-phase structure wherein the plane of the anthracene is twisted by ca. 54 degrees with respect to its 9,10-carboxylate units for both Mo and W. The results of these calculations are correlated with the electronic absorption spectral data and the electrochemical measurements (CV and DPV) of the first and second oxidation waves. The EPR spectra of the radical cations formed by single-electron oxidation with [Cp2Fe](+)[PF6]- in a THF-CH2Cl2 solvent mixture show that the complexes are valence trapped at ambient temperature on the EPR timescale. These results are discussed in the light of recent studies of dicarboxylate-linked MM quadruple bonds.     

Crystal structure of K4MnMo4O15 — A parent compound of a new isostructural series of complex oxides K4M2+Mo4O15 (M2+ = Mn, Mg, Co, Cd)

The structure of K₄MnMo₄O₁₅ was solved from single-crystal X-ray diffraction data (a = 10372, c = 8.160 Å, Z = 2, space group P-3, 2152 reflections, R = 0.039). The structure is of new, glaserite-like, type. A characteristic and original feature of the structure is a Mn(II)O₆ octahedron with six MoO₄ tetrahedra attached to it by their vertices; the octahedron is linked with a MoO₆ octahedron by a common face. The MoO₄ tetrahedra bridge the octahedral dimers with each other, forming lacy layers with potassium atoms lying between the layers. K₄M²⁺Mo₄O₁₅ (M²⁺= Mg, Co, Cd) phases, which have similar structures, have been synthesized and characterized.     

Synthesis and crystal structure of new complex oxides K10M2+Mo7O27 (M2+ = Mg, Mn, Co)

New compounds, K₁₀M²⁺ Mo₇O₂₇ (M²⁺ = Mg, Mn, Co), have been synthesized and characterized. The compounds have an original structure, as established for the first two phases (orthorhombic, space group Pnm2₁, Z = 2, a = 18353 and 18.402, b = 7.889 and 7.931, c = 10.566 and 10.604 å, R = 0.0345 and 0.0609, respectively). A specific feature of the structure is isolated clusters consisting of face-sharing MoO₆ and M²⁺O₆ octahedra, each of the latter having six MoO4 tetrahedra attached to it by vertices. The general pseudohexagonal motif of the structure of the phases is similar to that of glaserites.     

XANES study of oxycarbonates Hg1−xMxSr4Cu2(CO3)O6+δ (M=Mo,Cr)

X-ray absorption measurements have been made on CuL₃ and OK edges for two transition metal substituted Hg based oxycarbonates Hg_0.5Mo_0.5Sr₄Cu₂(CO₃)O_6+δ and Hg_0.4Cr_0.6Sr₄Cu₂(CO₃)O_6+δ. Despite a much lower T_c (37 K) the Cr sample has a much higher diamagnetic fraction than the Mo sample (T_c∼74 K). CuL₃ and OK edge spectra clearly indicate the presence of substantial number of doping holes in both the samples characteristic of their superconducting properties. But interestingly, the density of holes (DOH) are almost the same for the two samples. If the DOH correlated with the T_c solely, one would expect it be nearly double in Mo sample than the Cr one. Thus the present study presents a strong evidence for the dependence of DOH upon diamagnetic fraction over and above its dependence upon their transition temperature in the cuprate perovskites. Also the results of resistivity and susceptibility studies made earlier on these samples have been mentioned briefly.     

Photochemical reactions of M(CO)6 (M = Cr,Mo, W) with Ph2P(S)P(S)Ph2

New complexes {M(CO)₄[Ph₂P(S)P(S)Ph₂]} (M = Cr, Mo and W), (1a)–(3a), [(1a), M = Cr; (2a), M = Mo; (3a), M = W] and {M₂(CO)₁₀[-Ph₂P(S)P(S)Ph₂]} (M = Cr, Mo, W), [(1b)–(3b) [(1b), M = Cr; (2b), M = Mo; (3b), M = W]] have been prepared by the photochemical reaction of M(CO)₆ with Ph₂P(S)P(S)Ph₂ and characterized by elemental analyses, f.t.-i.r. and ³¹P-(¹H)-n.m.r. spectroscopy and by FAB-mass spectrometry. The spectra suggest cis-chelate bidentate coordination of the ligand in {M(CO)₄[Ph₂P(S)P(S)Ph₂]} and cis-bridging bidentate coordination of the ligand between two metals in (M = Cr, Mo and W).     

Synthesis of the New Silanediyldiphosphinite tBu2Si(OPPh2)2 and its Reactions with the Norbornadiene Complexes C7H8M(CO)4 (M = Cr,Mo, W). Crystal Structures of cis-M(CO)4[tBu2Si(OPPh2)2] (M = Cr,Mo)

Silanediyldiphosphinite tBu₂Si(OPPh₂)₂ 1 has been synthesised. 1 reacts with the norbornadiene complexes C₇H₈M(CO)₄ (M = Cr, Mo, W) to give six-membered chelate rings of the type cis-M(CO)₄[tBu₂Si(OPPh₂)₂] 2–4 . The crystal structures of the chromium and molybdenum complexes cis-Cr(CO)₄[tBu₂Si(OPPh₂)₂] 2 and cis-Mo(CO)₄[tBu₂Si(OPPh₂)₂] 3 have been determined. Both complexes crystallise in the triclinic system (space group P1 ) with unit cell parameters: ( 2 ) a = 1 093(3) pm, b = 1 477(5) pm and c = 1 542(5) pm; α = 108.4(2)°, b? = 103.87(11)° and b? = 104.57(10)°; U = 2.143(12) nm³; Z = 2; ( 3 ) a = 1 097.8(2) pm, b = 1 483.7(2) pm and c = 1 554.3(2) pm; α = 108.10(1)°, b? = 103.956(6)° and γ = 104.213(7)°; U = 2.1899(6) nm³; Z = 2. Both 2 and 3 consist of discrete, slightly distorted, octahedral monomers in which the six-membered chelate rings are essentially planar. In contrast, the conformations of the chelate rings found in crystal structures of analogous complexes vary from twist-boat to “chaise longue”.     

Cyclic molecular materials based on [M2O2S2]2+ cores (M = Mo or W)

The purpose of this article is to illustrate how conventional precursors can serve, when used with a drop of imagination, to the synthesis of sophisticated inorganic rings and wheels. The self-condensation of the [M2O2S2]2+ fragments under acido-basic process produces, in the presence or absence of guest species, linear enchainment restricted to discrete cyclic entities. This approach was revealed to be a highly fruitful strategy for developing an extended family of compounds, differing in their nuclearity, size and shape, and the nature of the encapsulated guest molecule. Indeed, the resulting cycles delimit a cationic open cavity, which can be filled by neutral polar molecules such as aquo ligands or anionic molecules such as phosphates, polycarboxylates and even metalates. The flexibility of the rings is at the origin of interesting host-guest properties: the deformation (symmetry) and the adaptation (nuclearity) of the inorganic cycle are directly related to the size and the coordination requirements of the encapsulated substrate. The versatility of the metal coordination, octahedral or square pyramidal, confers dynamic properties to the ring. In the solid state, molecular rings assemble in striking 3-D networks based on direct cation-anion connections. Alkali cations are arranged in pillars or layers for anchoring the anionic rings.     

The first structurally confirmed paddlewheel compound with an M(2)(7+) core: [Os(2)(hpp)(4)Cl(2)](PF(6))

Oxidation of Os(2)(hpp)(4)Cl(2), 1 (hpp = the anion of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine), with (FeCp(2))PF(6) produces air-stable [Os(2)(hpp)(4)Cl(2)]PF(6), 2. This is the first structurally confirmed metal-metal bonded paddlewheel compound having an M(2)(7+) core. The Os-Os distances for two crystalline forms, 2.2acetone and 2.hexane, are 2.3309(4) and 2.3290(6) A, respectively. EPR, (1)H NMR, and magnetization data indicate that 2 has an unpaired electron and an exceptionally low g value of 0.791 +/- 0.037. An electrochemical study shows that there is a quasireversible wave corresponding to a more highly oxidized species with an unprecedented Os(2)(8+) core.     

SiO2负载的Pt-M(M=Cr,Mo,W)配合物双功能催化剂

过渡金属异双核金属有机化合物的研究是一个活跃的领域,人们期望从中制取对极性小分子(如CO,CO2等)具有双功能活化的催化剂.周期表前区过渡金属或稀土元素(如Ti,Zr,Mo,La,Ce等)作为添加组分可明显地增加SiO2负载的铑催化剂催化CO氢化反应的活性和含氧化合物的选择性[1].虽然一些异双核金属氢基羰基化合物已被合成和表征[2],但是关于SiO2负载的异双核金属配合物催化剂的研究还未见文献报道.我们合成、表征了(PPh3)HPt(μ-PPh2)(μ-CO)M(CO)4(M=Cr,Mo,W)异双核配合物[3](I).本文研究了SiO2负载的该配合物催化剂对CO氢化反应和对丙烯氢甲酰化反应的两种催化功能.     

Investigation of the synthesis, activation, and isosteric heats of CO2 adsorption of the isostructural series of metal-organic frameworks M3(BTC)2 (M = Cr, Fe, Ni, Cu, Mo, Ru)

The synthesis, activation, and heats of CO(2) adsorption for the known members of the M(3)(BTC)(2) (HKUST-1) isostructural series (M = Cr, Fe, Ni, Zn, Ni, Cu, Mo) were investigated to gain insight into the impact of CO(2)-metal interactions for CO(2) storage/separation applications. With the use of modified syntheses and activation procedures, improved BET surface areas were obtained for M = Ni, Mo, and Ru. The zero-coverage isosteric heats of CO(2) adsorption were measured for the Cu, Cr, Ni, Mo, and Ru analogues and gave values consistent with those reported for MOFs containing coordinatively unsaturated metal sites, but lower than for amine functionalized materials. Notably, the Ni and Ru congeners exhibited the highest CO(2) affinities in the studied series. These behaviors were attributed to the presence of residual guest molecules in the case of Ni(3)(BTC)(2)(Me(2)NH)(2)(H(2)O) and the increased charge of the dimetal secondary building unit in [Ru(3)(BTC)(2)][BTC](0.5).     

EPR STUDY ON THE ELECTRON TRANSFER OF IRON COMPLEXES WITH MO_XS_(4_X)~2 (M = Mo,W;x=0 -2) LIGANDS

<正> In recent years, the chemistry of high-valent molybdenum compounds containing sulfur has gained momentum, probably due to its importance in various metallo-biomolecules which are responsible for vital functions like electron transfer and redox reactions. The relevance of thiomolybdates, MoO_xS_(4-x) ~(2-)(x=1—2),and particularly of MoS_4~(2-) to biologi     

Two novel vanadium tellurites covalently bonded with metal-organic complex moieties: M(phen)V(2)TeO(8) (M = Cu, Ni)

Two novel two-dimensional organic-inorganic hybrid vanadium tellurites M(phen)V(2)TeO(8) (M = Cu (1), Ni (2)) have been hydrothermally synthesized and characterized by the elemental analyses, IR spectra, EPR spectrum, XPS spectra, TG analyses, and single-crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic system, space group P2(1)/c, with a = 9.2193(18) A, b = 7.9853(16) A, c = 21.401(4) A, beta = 97.54(3) degrees, and Z = 4. Compound 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 9.2163(18) A, b = 7.9897(16) A, c = 21.386(4) A, beta = 97.52(3) degrees, and Z = 4. Compounds 1 and 2 are isostructural, and both exhibit interesting two-dimensional networks with [V(2)TeO(8)]( infinity ) double-chain-like ribbons bridged by metal-organic complex moieties [M(phen)](2+) (M = Cu and Ni). Furthermore, the three-dimensional supramolecular architectures of compounds 1 and 2 are formed by pi-pi stacking interactions of phen groups between adjacent layers.     

Electronic Structure of TiAl-2M(M=V,Nb,Ta,Cr,Mo,W,Mn) Alloy

1INTRODUCTIONTitaniumaluminidesbasedonY-TiAlarereceivingconsiderableattentionaspo-tentialcandidatesformaterialsinhightemperatureaerospaceapplication.Theirlowdensity,hightemperaturescreepresistance,highoxidationresistanceandstrengthmakesthemexcellentpotentialenginematerials.Howevertheirlowductilityandlowfracturetoughnessatroom'temperaturesaremajorhindrancestotheirpracticaluti-lization.TheTiAlalloymayhaveanelongationabout2%t'},furtherimprovementisnecessarybeforethesematerialscouldbeusedin…     

In situ FT-IR study on CO2 hydrogenation over SiO2-supported PtM (M = Cr, Mo, W) complex catalysts

The in situ FT-IR spectra were used to study the CO₂ hydrogenation reaction over the SiO₂-supported heterobinuclear metal complex catalysts, PtM (M=Cr, Mo, W). The bands, which correspond to the formate species absorbed on the catalysts, were observed. During the hydrogenation reactions, the adsorbed linear and bridging CO was not observed. The experimental results suggest that for the CO₂ and CO hydrogenation reaction over the same catalysts, their catalytic active intermediate species and the reaction mechanisms should be different.     

Coordination of Phenylsulfinate PhSO2— to Mo3MS44+ Clusters (M = Ni,Pd)

Reaction of heterometal cuboidal clusters [Mo₃(MCl)S₄(H₂O)₉]³⁺ (M = Ni, Pd) with PhSO₂Na in aqueous HCl leads to the substitution at Ni or Pd to give the [Mo₃(M(PhSO₂))(H₂O)_9—xCl_x]^(3—x)+species, isolated as supramolecular adducts with cucurbituril (Cuc) [Mo₃(Ni(PhSO₂))S₄Cl_1.17(H₂O)_7.83][Mo₃(Ni(PhSO₂))S₄Cl_2.22(H₂O)_6.78]Cl_2.61 · Cuc · 15H₂O ( 1 ) and [Mo₃(Pd(PhSO₂))S₄Cl_1.12(H₂O)_7.88][Mo₃(Pd(PhSO₂))S₄Cl_2.29(H₂O)_6.71]Cl_2.59 · Cuc · 11H₂O ( 2 ), respectively. Crystal structure of 1 and 2 was determined, revealing that the PhSO₂ is coordinated via its sulfur atom (Ni — S 2.182 Å, Pd — S 2.305 Å). The structure of these isostructural compounds is built from triple aggregates {(cluster)(Cuc)(cluster)} united into zigzag chains via hydrogen bonds between coordinated PhSO₂ and H₂O ligands.     

Substitution chemistry of MM quadruply bonded complexes (M = Mo or W) supported by the anion of 2-hydroxy-6-methylpyridine

The compounds M(2)(mhp)(4), where M = Mo or W and mhp is the anion formed from deprotonation of 2-hydroxy-6-methylpyridine, are shown to react with carboxylic acids RCOOH to give an equilibrium mixture of products M(2)(O(2)CR)(n)(mhp)(4-n) where R = 2-thienyl and phenyl. The equilibrium can be moved in favor of M(2)(O(2)CR)(4) by the addition of excess acid or by the favorable crystallization of these products. The latter provides a facile synthesis of the W(2)(O(2)CR)(4) compound where R = 9-anthracene. Reactions involving 2,4,6-triisopropyl benzoic acid, TiPBH, yield M(2)(TiPB)(2)(mhp)(2) compounds as thermodynamic products. Reactions involving Me(3)OBF(4) (1 and 2 equiv.) yield the complexes Mo(2)(mhp)(3)(CH(3)CN)(2)BF(4) and Mo(2)(mhp)(2)(CH(3)CN)(4)(BF(4))(2), respectively. The latter compound has been structurally characterized and shown to have mirror symmetry with two cis mhp ligands: MoMo = 2.1242(5) A, Mo-O = 2.035(2) A, Mo-N(mhp) = 2.161(2) A, and Mo-N(CH(3)CN) = 2.160(3) and 2.170(3) A. Reactions involving Mo(2)(mhp)(3)(CH(3)CN)(2)(2+) and Mo(2)(mhp)(2)(CH(3)CN)(4)(2+) with (n)Bu(4)NO(2)CMe (1 and 2 equiv.) yield the complexes Mo(2)(mhp)(3)(O(2)CMe) and Mo(2)(mhp)(2)(O(2)CMe)(2) which are shown to be kinetically labile to ligand scrambling. Reactions between Mo(2)(mhp)(3)(CH(3)CN)(2)(+)BF(4)(-) (2 equiv.) and [(n)Bu(4)N(+)](2)[O(2)C-X-CO(2)](2-) yielded dimers of dimers [Mo(2)(mhp)(3)](2)(micro-O(2)C-X-CO(2)] where X = nothing, 2,5- or 3,4-thienyl and 1,4-C(6)H(4). Reactions between Mo(2)(mhp)(2)(CH(3)CN)(4)(2+)(BF(4)(-))(2) and tetra-n-butylammonium oxalate and terephthalate yield compounds [Mo(mhp)(2)bridge](n) which by MALDI-TOF MS are proposed to be a mixture of molecular squares (n = 4) and triangles (n = 3) along with minor products of [Mo(2)(mhp)(3)](2)(bridge) and Mo(2)(mhp)(4) that arise from ligand scrambling.