The crystal structure of Ca3Cu3(PO4)4

Single crystals of Ca₃Cu₃(PO₄)₄ synthesized hydrothermally at 420°C and 55 kpsi (3.8 kbar) were found to occur in the space group $\text{P2}{}_1\text{a}$ (No. 14) with a = = 17.619(2), b = 4.8995(4), c = 8.917(1)Å, β = 124.08(1)°, and Z = 2. Full-matrix least-squares refinement of the structure using diffractometer data converged to a final anisotropic R = 0.037 (R_w = 0.046). The two calcium atoms are in six- and nine-coordination and the two copper-containing polyhedra (four- and five-coordinated) are similar to those previously found in Cu₃(PO₄)₂.     

The crystal structure of Tl0.84V5Se8 and magnetic bulk properties

While the antiferromagnetic binary compound V₅Se₈ (Y. Kitaoka and H. Yasuoka, J. Phys. Soc. Jpn.48, 1460, 1980) of which the measured magnetic susceptibility above 27 K cannot be fitted to a Curie-Weiss law and a Curie-Weiss law with a term for the temperature-independent paramagnetism, the ternary compound Tl_0.84V₅Se₈ exhibits paramagnetism. The measured susceptibility fits the equation $\text{χ = χ}{}_0\text{+}\text{C}\text{(T ? θ)}$. In comparison to Tl_0.96V₅S₈ (W. Bensch, E. Amberger, and J. Abart, in press) with shorter VV distances than in Tl_0.84V₅Se₈, the magnetic moment attributed to V(3) in the selenide is markedly higher.     

The crystal and magnetic structures of Sr2YRuO6

Time-of-flight powder neutron diffraction data have been used to refine the crystal structure of the ordered, distorted perovskite Sr₂YRuO₆. Yttrium and ruthenium are octahedrally coordinated in this material with average MO bond lengths of 2.202 and 1.955 Å, respectively. Constant wavelength neutron diffraction data show that Sr₂YRuO₆ is a Type I antiferromagnet at 4.2 K with an ordered magnetic moment of 1.85 μ_B per Ru⁵⁺ ion. The Néel temperature of Sr₂YRuO₆ was determined to be 26 K. The data suggest that the 4d³ electrons in this material are localized rather than itinerant.     

Microdomain texture and oxygen excess in the calcium-lanthanum ferrite: Ca2LaFe3O8

The analysis by TEM and electron diffraction of the anion-deficient perovskite Ca₂LaFe₃O₈ confirms the model previously proposed by J. C. Grenier et al. (Mater. Res. Bull.11, 1219 (1976)) with a structure intermediate between perovskite and brownmillerite. The unit cell parameters are ～√2a_c, 3a_c, √2a_c (where a_c is the cubic perovskite unit cell parameter). However, the unit cell is sometimes doubled along the b axis. When the sample is treated in air at temperatures around 1400°C, an oxidation process is observed and the unit cell becomes cubic (a_c = 3.848(3) Å). Nevertheless, electron diffraction investigations suggest the existence of a much more complex situation in which three-dimensional microdomains intergrow within one crystal. Each of these microdomains appears to have a structure clearly related to the low-temperature sample, but the superstructure is randomly found along each of the three cubic subcell directions (i.e., the unit cell √2a_c, √2a_c, 3a_c alternates randomly with 3a_c, √2a_c, √2a, and with √2a_c, 3a_c, √2a_c). High-resolution electron microscopy allows one to ascertain this microdomain texture of the real crystal.     

The crystal and molecular structure of Rh2(CH3CO2)4[HCON(CH3)]2—effect of ligands on metalmetal bonding

The structure of Rh₂(CH₃CO₂)₄(DMF)₂ {DMF = HCON(CH₃)₂} has been determined by single crystal X-ray methods. The compound crystallizes with eight formula units in a cell of dimensions: a = 29.438(7) Å, b = 7.978(2) Å, c = 20.279(5) Å, β = 113.20(4)°, V = 4377.5 ų, space group C2/c. The structure has been refined by full-matrix least-squares method to a final R = 0.030 for the 4156 observed data. Two Rh(II) atoms are linked by four acetate groups forming a dimeric unit, where the RhRh distance is 2.383(1) Å. The coordination sphere about each Rh atom is completed by a DMF molecule; the average RhO(DMF) distance is 2.296(3) Å.     

The direct electrochemical synthesis and crystal structure of salts of [M4(SC6H5)10]2− anions (M = Zn,Cd)

The salts [(C₂H₅)₃NH]₂[M₄(SC₆H₅)₁₀] (M = Zn, Cd) can be prepared by the electrochemical oxidation of the metal in an acetonitrile solution of triethylamine and benzenethiol. An X-ray crystal structure determination shows that the anion consists of a tetrahedron of metal atoms, each carrying a terminal -SC₆H₅ ligand, and connected to the three other metal atoms by bridging > SC₆H₅ groups. The results are compared with those for similar compounds reported in the literature.     

The influence of the steric properties of the ligands PR2Ph and L on the formation and properties of the complexes Mo(η6-PhPR2)(L)(PPh2CH2CH2PPh2), R = Et,L = PPhEt2 and R = Ph,L = PPh3, PR′3, CO,CNR, N2, H2

The reduction of MoCl₄(DPPE) (DPPE = PPh₂CH₂CH₂PPh₂) with Mg or Na/Hg in the presence of 2 PPhR₂ under Ar results in the formation of the new complexes Mo(η⁶-PhPR₂)(PPhR₂)(DPPE) when R is Ph (Ia) or Et(II). No η⁶-PhPR₂ complex is obtained when R is Me because this small ligand forms strong MoP σ-bonds; nor is one obtained for R = Cy because of too much steric crowding. The limits for η⁶-complexation can be quantified in terms of cone angle sums.Complex Ia is very similar to Mo(η⁶-PhPMePh)(PMePh₂)₃ (IIIa) in that both react at similar rates with a variety of small ligands L = PMePh₂, PMe₂Ph, PMe₃, P(OMe)₃, N₂, CO, CNBu^t and H₂ via dissociation of a labile σ-bonded ligand. Several other less crowded η⁶-arylphosphinemolybdenum complexes including II do not have labile ligands at 25°C. The new complexes Mo(η⁶-PhPPh₂)(L)(DPPE) have been characterized by ³¹P and ¹H NMR, IR and gas uptake measurements, Ia has a higher affinity for H₂ than IIIa possibly because Mo(η⁶-PhPPh₂)(H)₂(DPPE) adopts a non-fluxional trans-configuration. The ³¹P chemical shift of the σ-bonded ligand in 8 derivatives of Ia and 12 of IIIa correlate with the sum of the cone angles of the three σ-bonded ligands in each complex.     

Synthesis of 1,2-ethanediylbis(diphenyl-phosphonium)-PH,P′H′ hexachloromolybdate(III) I and nonachlorodimolybdate(III) II. The crystal structure of (dppeH2)3[MoCl6]2·12h2O

Two compounds of the formulae (dppeH₂)₃[MOCl₆]₂ ·12H₂O I and (dppeH₂)₃[Mo₂Cl₉]₂II are described. For compound I, which proved to be active in olefin epoxidation, the crystal structure was determined. The rose-pink crystals are triclinic, space group P$\text{1}$ with a = 13.715(9), b₃ = 14.686(7), c = 12.512(7) Å, α = 109.56(4), β = 97,98(4) and γ = 91.27(5)°, V = 2345 Å, D_m = 1.42 and D_c = 1.44 gcm^?3, Z = 1. Block-diagonal least squares refinement of the structure has led to a final value of the conventional R factor of 0.049 for the 3914 independent reflections with I > 3σ(I). Bond distances are in the range: MoCl 2.439(2)–2.469(2) Å, and PC 1.771(9)–1.806(8) Å.     

X-ray photoelectron emission studies of mixed selenides AgGaSe2 and Ag9GaSe6

Auger and direct electron specta from crystalline AgGaSe₂ and Ag₉GaSe₆ have been studied with X-ray photoelectron spectroscopy. It is shown that the AgM₅N_4,5N_4,5 and M₄N_4,5N_4,5 Auger spectra are more sensitive to the chemical environment than the Ag 3d direct photoelectron spectra. Furthermore the Auger parameter as defined by Wagner is used in order to characterize the chemical state of these compounds. Last, the XPS spectra of the valence-band region are investigated and chalcogen s and p and noble-metal d bands are clearly identified. The electronic structure of these two selenides does not seem to be determined predominantly by the crystal structure. As a whole, the spectral features are discussed in connection with the character of the chemical bonding and the physical properties of these compounds.     

The effects of titanium or chromium doping on the crystal structure of V2O3

The crystal structures of five samples of (Ti_xV_1?x)₂O₃ (0.011 ≤ x ≤ 0.077) and seven samples of (Cr_xV_1?x)₂O₃ (both metallic and insulating phases, 0 ≤ x ≤ 0.05) were determined from X-ray diffraction data collected from single crystals. These compounds are isomorphous with α-alumina. The cell dimensions change such that the a axes increase and the c axes decrease with increasing Ti or Cr. In the CrV₂O₃ system, from 0 to 1.25% Cr doping, changes in structure parallel those observed in the TiV₂O₃ system. These changes are consistent with a slight weakening of the bonding metal-metal interactions in the basal plane, leading to an increase in the metal-metal distances coupled with changes which maintain constant metal-oxygen distances. A discontinuity appears at about 1.25% Cr as the transition from metal to insulating behavior occurs with increasing Cr content. No change in crystal symmetry accompanies this transformation. It appears that the metal-metal bonding interactions are retained even in the insulating phase of Cr-doped V₂O₃. A comparison of the structural variation in the Cr- and Ti-doped systems suggests that the change from metallic to insulating behavior cannot be a structure effect. These changes are, however, consistent with the band model proposed by others for these systems.     

Preparation and properties of vanadyl(IV) hypophosphite,VO(PO2H2)2·H2O

The preparation of VO(PO₂H₂)₂·H₂O was possible by direct reduction of V₂O₅ with hypophosphorous acid or by interaction of VOSO₄ and H₃PO₂ solutions, and subsequent crystallization. The compound was characterized by IR, electronic and ESR spectroscopy and X-ray powder diffractometry. Magnetic susceptibilities were measured in the temperature range between 100 and 300 K. The thermal decomposition was also investigated in detail, showing a very complex sequence of degradation steps which finally generate a polymeric V(III) phosphite.     

Intercalation phases of TiS2, 2HNbS2, and 1TTaS2 with ethylenediamine and trimethylenediamine: A crystal chemical and thermogravimetric study

The title compounds were prepared and chemicaly analyzed. Their crystal structures were determined from rotating crystal photographs. 1T-, 2H-, and two different 3R-polymorphs were observed. The thermogravimetric analysis, revealing two to four distinct steps for the phases derived from TiS₂ and 2HNbS₂, and only one to two smeared-out steps for those derived from 1TTaS₂, proves the coexistence of strongly and weakly bound intercalate molecules. The first ones cannot be thermally deintercalated without chemical decomposition. The results are discussed within the framework of an ionic bonding model.     

Preparation,crystal structure,and properties of the mixed-valence compound Nb3Se5Cl7

The new compound Nb₃Se₅Cl₇ was prepared by heating 2NbSe₂Cl₂ + 1NbCl₄ at 530°C for 2–3 weeks. The compound is monoclinic with a = 7.599, b = 12.675, c = 8.051Å; β = 106.27°; space group $\text{P2}{}_1\text{m}$. The corresponding bromide, Nb₃Se₅Br₇ (obtained by decomposition of NbSe₂Br₂ under NbSeBr₃), is isotypic with a = 7.621, b = 12.833, c = 8.069Å; β = 106.21°. from the crystal structure and XPS spectra it follows that Nb₃Se₅Cl₇ can be formulated as: [Nb⁴⁺₂Nb⁵⁺₁(Se₂)^2?₂Se^2?₁Cl^?₇]. The structure consists of chains of composition [Nb⁴⁺₂(Se₂)^2?₂Cl^?₅], to which side chains [Nb⁵⁺Se^2?Cl^?₂] are attached. The Nb⁴⁺ atoms form pairs (NbNb = 2.94 Å) which explains that Nb₃Se₅Cl₇ is a diamagnetic semiconductor with a band gap (1.59 eV at 5°K, 1.49 eV at 300°K) very similar to that of NbSe₂Cl₂.     

Neutral complexes of Ga2X4 (X = Cl,Br) containing GaGa bonds: The crystal and molecular structure of Ga2Cl4 · 2Pyridine

The complexes Ga₂X₄ · 2L (L = pyridine, 3-methylpyridine, 4-methylpyridine, morpholine, 1,4-thioxane, 1,4-dithiane, tetrahydropyran, tetrahydrofuran, tetrahydrothiophene and dimethylsulphide) have been prepared. Vibrational spectra indicate that they all contain GaGa bonds and this is confirmed for Ga₂Cl₄ · 2pyridine by a crystal structure determination which shows it to be isostructural with the bromide analogue. We were unable to synthesize complexes of stoichiometry Ga₂X₄ · 4L which had previously been reported.     

Some studies on the solid solutions in the systems Sr2Nb2O7Eu2Nb2O7 and Sr2Ta2O7Eu2Ta2O7

Preparation of new solid solutions containing divalent europium have been tried in the systems Eu₂Nb₂O₇Sr₂Nb₂O₇ and Eu₂Ta₂O₇Sr₂Ta₂O₇. These solid solutions described as Eu_2xSr_2(1?x)M₂O₇ (M = Nb and Ta) exist in a pure orthorhombic phase in a limited region of x from 0 to about 0.5. The compounds with compositions close to Eu₂M₂O₇ exist but techniques have not been found to prepare them in pure form.     

The preparation of cis- and trans-[PtH(C6Cl5)(PEt3)2 and a study of the “hydride-donor capacity” of the complexes trans- [PtH(C6X5(PEt3)2] (X = F and Cl)

The preparations of cis- and trans-[PtH(C₆Cl₅)(PEt₃)₂] by thermal decomposition of cis- and trans-[Pt(OCHO)(C₆Cl₅)(PEt₃)₂], respectively, are reported. Also described are cis- and trans-[Pt(SnCl₃)(C₆Cl₅)(PEt₃)₂], obtained by treating SnCl₂ with cis- and trans-[PtCl(C₆,Cl₅)(PEt₃)₂], respectively. It is shown that while trans- [PtH(C₆Cl₅)(PEt₃)₂] does not form hydride-bridged complexes in the presence of trans-(PtH(MeOH)(PEt₃)₂]⁺, the corresponding complex trans-[PtH(C₆)(PEt₃)₂] reacts with the same solvento complex, in methanol, giving labile [(PEt₃)₂HPt(-μH)Pt(C₆F₅)(PEt₃)₂]⁺.     

The preparation and X-ray crystal structure of W3(μCN)3(NO)3(CO)9

The nitrosation of Na[W(CO)₅CN] using amyl nitrite and sulphuric acid in a two phase water— diethyl ether system gives the trinuclear compound W₃(μCN)₃(NO)₃(CO)₉. A single crystal X-ray diffraction study showed that the compound contains a nine-membered ring of three tungsten atoms and three bridging cyanide groups. The terminal carbonyl and nitrosyl ligands were not distinguishable.     

Direct synthesis and NMR spectra of [(C6H5)2PCH2]2CuB5H8: Comments on the solution structure of 2,3-μ-metallopentaboranes

The species [(C₆H₅)₂PCH₂]₂CuB₅H₈ has been prepared directly from [(C₆H₅)₂PCH₂]₂CuI and K[B₅H₈]. NMR spectra unequivocally indicate that the species has a static structure in solution and an argument is presented that all 2,3-,μ-metallopentaboranes have similarly static solution structures.     

Vibrational and luminescence spectra of a new binuclear uranyl complex [(C2H5)4N]2[UO2F(NO3)2]2

The preparation, vibrational and luminescence spectra of the title compound are described. The complex has bidentate nitrate groups and bridging fluoride ions. The spectra are assigned in detail and interpreted as showing couplings between the uranyl antisymmetric stretching modes and between the nitrate modes within the dimer, the coupling energy being 17 cm^? in the former case. There is no clear evidence for electronic coupling involving the uranyl groups.     

The crystal structure of a sodium molybdenum oxide,Na6Mo10O33, containing cross-linked chains of octahedra and square pyramids

Na₆Mo₁₀O₃₃ crystallizes in the triclinic system with unit-cell dimensions a = 8.049(4), b = 12.180(6), c = 7.576(4) Å, α = 99.96(9), β = 100.74(1), γ = 109.88(10)°, and space group $\text{P}\text{1}$ with z = 1. The structure was solved using Patterson and Fourier methods. Of the 3045 unique reflections measured by counter techniques 2758 with I ≥ 3σ(I) were used in the least-squares refinement of the model to a conventional R of 0.030 (R_w = 0.034). The structure of Na₆Mo₁₀O₃₃ consists of two different types of chains of molybdenum-oxygen polyhedra linked to one another approximately at right angles. One chain of edge- and corner-shared distorted MoO₆ octahedra is approximately parallel to [001] and the second chain, consisting of corner-shared pairs of octahedra edge-shared to pairs of edge-shared MoO₅ square pyramids (inverted with respect to one another), is approximately parallel to [100]. These linked chains form an infinite three-dimensional network in the interstices of which the sodium atoms are located. One of the chains of the Na₆Mo₁₀O₃₃ structure is the same as that found in Ag₆Mo₁₀O₃₃; the second chain, however, does not occur in Ag₆Mo₁₀O₃₃.