Chemistry in fuming nitric acids—I. NMR spectroscopic study of PF5, HPO2F2 and P4O10 in the solvent system 44 wt.% N2O4 in 100% HNO3

³¹P and ¹⁹F NMR spectroscopy has been used to elucidate the nature of the interaction of PF₅, HPO₂F₂ and P₄O₁₀ with the solvent system 44 wt.% N₂O₄ in 100% HNO₃ (“High Density Acid”, HDA). PF₅ generates the species PF₆^?, HPO₂F₂ and HF (with some H₂PO₃F present as a minor product). HPO₂F₂ gives rise to H₂PO₃F and HF (with smaller amounts of PF₆ also present). The ³¹P NMR spectrum of P₄O₁₀ in HDA exhibits four resonances assigned to P(OH)₄⁺, H₄P₂O₇, (HPO₃)₄ and a mixture of cyclic and branched phosphoric acids, respectively.     

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.     

Some comments on the mechanism of the preparation of (Et4N)2B10H10 by thermolysis of Et4NBH4

The volatile intermediate Et₃NBH₃ was isolated during the thermolysis of Et₄NBH₄ at 185°C for 16 hr under dynamic vacuum. The rate of decomposition of Et₄NBH₄ was studied. Separate thermolyses of Et₄NBH₄ (or Et₃NBH₃) with closo B₉H₉^2?nido B₉H^?₁₂, or arachno B₉H₁₄^? did not produce B₁₀H₁₀^2? as the major product. These results are inconsistent with the “build-up” mechanism previously proposed for the thermolytic convertion of BH ₄^? to B₁₀H₁₀^2? and a new mechanism is required.     

Preparation and electron microscopy of intermediate phases in the interval Ce7O12Ce11O20

Crystals of CeO₂, grown from a flux of sodium tetraborate, were reduced in dry hydrogen to compositions in the interval CeO_1.714CeO_1.818. Selected compositions were studied using a high-resolution electron microscope. The phase CeO_1.714(Ce₇O₁₂) was confirmed to have the same unit cell as does Pr₇O₁₂ and Tb₇O₁₂. CeO_1.818(Ce₁₁O₂₀) was found to be isostructural with Tb₁₁O₂₀. Two new phases in the interval were established unequivocally. One of them, probably Ce₁₉O₃₄, is triclinic with a = 6.627, b = 11.478, c = 10.123, α = 100.9, β = 90.0, and γ = 95.5, has not previously been observed in any rare earth oxide system. Another, Ce₆₂O₁₁₂, appears to be isomorphous with Tb₆₂O₁₁₂. The two intermediate phases previously reported in this interval, Ce₉O₁₆ and Ce₁₀O₁₈, were not observed, nor was Ce₁₂O₂₂. Diffraction evidence also points to three additional phases in the interval not previously seen.     

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.     

Interactions magnétiques dans des groupements binucléaires [Fe2O7]8− au sein de Na8Fe2O7

The magnetic interaction in the structural units [Fe₂O₇]^8?, built of two corner-sharing FeO₄ tetrahedra, in Na₈Fe₂O₇ ($\text{Na}{}_2\text{O}\text{Fe}{}_2\text{O}{}_3\text{=}\text{4}\text{1}$) has been studied by magnetic susceptibility measurements (4.2–500 K). An exchange integral $\text{J}\text{K}{}_{\mathrm{<mtext>B</mtext>}}$ of ?37 K is obtained by comparison of the experimental values and the calculated ones using a Heisenberg-Dirac-Van Vleck-type Hamiltonian ? = $\text{?2J}\text{S}\text{?}{}_1\text{S}\text{?}{}_2$. The hypothesis of magnetically isolated [Fe₂O₇]^8? groups is corroborated by Mössbauer spectroscopy between 1.5 and 77 K. The susceptibility measurements of the solid solutions Na₈Fe_2?xM_xO₇ (M = Al, Ga; 0 ≤ x ≤ 0.2 for Al; 0 ≤ x ≤ 2 for Ga) leads to the same conclusion of the existence of isolated Fe³⁺Fe³⁺ pairs in Na₈Fe₂O₇. The type of substitution of Fe by Al or Ga is determined; homonuclear Fe³⁺Fe³⁺ and M³⁺M³⁺ pairs and heteronuclear Fe³⁺M³⁺ pairs are formed.     

Crystal structure and charge carrier concentration of W18O49

The electrical resistivity of the tungsten oxide, W₁₈O₄₉, is 1.75 · 10^?3 Ω cm along the needle axis. The charge carrier density, as determined by reflectivity measurements, is 1.87 · 10²² cm^?3, thereby indicating that most of the charge carriers are delocalized. Hence the smaller conductivity along the needle axis than that expected for such charge carrier concentrations must be found in the structure, which has been refined using the data collected with an automatic diffractometer. The structure consists of WO₆ and WO₇ polyhedra which are linked along edges and/or corners. However, as the linkage parallel to b takes place only by sharing corners, an anisotropy in the electrical conductivity may be expected. Another explanation for the smaller conductivity may be found in the occurrence of defects such as tunnels in the structure, which may scatter the electrons. The refinement shows that the tungsten positions, determined by Magneli (Arkiv Kemi1, 223 (1950)), are essentially correct; but the positions of the oxygens, especially two of them, differ considerably. This results in one of the tungsten atoms getting an additional coordinating oxygen, the coordination number thereby becoming seven.     

35Cl NQR in N3P3Cl4Ph2 and N3P3Cl4(NMe2)2

³⁵Cl NQR has been investigated in two cyclotriphosphazene derivatives N₃P₃Cl₄Ph₂ and N₃P₃Cl₄(NMe₂)₂. The observed frequencies are assigned to the various chlorines and the temperature variation of the NQR frequencies studied in the range from 77 K to 300 K. The results are analysed using the Bayer-Kushida-Brown approach. Torsional (librational) frequencies are found to fall in the range 10–25 cm^?1 and are found to be only slightly temperature dependent.     

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.     

Subsolidus phase relations in the systems CeO2RE2O3 (RE2O3 = C-type rare earth sesquioxide)

The systems CeO₂RE₂O₃ (RE₂O₃ = C-type rare earth sesquioxide) were studied to: (1) investigate the claims of several workers for the existence of a complete solid solution series between CeO₂ and RE₂O₃ and (2) to characterize the weak C-type X-ray diffraction peaks reported by others from samples in the single-phase fluorite solid solution region. It is shown that a complete solid solution series does not exist, and an explanation for the observations of others reporting such is tendered. It is also shown that the observation of C-type reflections in the supposed single-phase fluorite field can be attributed to the partial reduction of Ce⁴⁺ to Ce³⁺ at the firing temperature, resulting in the movement of the bulk composition into a two-phase field of the CeO₂RE₂O₃Ce₂O₃ phase diagram, rather than the formation of a domain structure due to ordering.     

Formation and transformation of Pb2SiO4

A new modification of Pb₂SiO₄ was formed by the simultaneous hydrolysis of lead and silicon alkoxides, followed by washing and drying. It has a     

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.     

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 crystal structure of La3Ru3O11: A new cubic KSbO3 derivative oxide with no metal-metal bonding

La₃Ru₃O₁₁ was prepared by the reaction of La₂O₃, RuO₂, and NaClO₃ in a KCl flux under vacuum at 950°C. The crystal structure of this new cubic KSbO₃ derivative oxide was determined from single-crystal X-ray diffraction data collected on an automated diffractometer with MoKα radiation. Principal crystallographic data: Cubic, space group Pn3; a = 9.451(2), Å; V = 844.2ų; d_X = 7.049 g cm^?3. Final discrepancy indices R = 0.036, R_w = 0.042. La₃Ru₃O₁₁ is isomorphous with Bi₃Ru₃O₁₁, but is notably different in showing no direct bonding between ruthenium atoms; the closest RuRu contact in this new oxide is 2.994(1) Å.     

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.     

Further studies of phosphine adducts of niobium(IV) and tantalum(IV) chlorides: New seven- and eight-coordinate compounds with trimethylphosphine: NbCl4(PMe3)3 and Ta2Cl8(PMe3)4

The reaction of NbCl₄(THF)₂ with an excess of PMe₃ in toluene solution afforded a 70% isolated yield of green NbCl₄(PMe₃)₃. When a slurry of TaCl₅ in toluene containing a slight excess of PMe₃ was reduced with sodium amalgam overnight, a 60% yield of orange to red (depending on crystal size) Ta₂Cl₈(PMe₃)₄ was obtained. Both compounds have been fully characterized by X-ray crystallography. NbCl₄(PMe₃)₃ forms monoclinic crystals (P2₁/c) with unit cell dimensions a = 15.061(3) Å, b = 11.677(4) Å, c = 11.583(4) Å, β = 91.71(3)°, V = 2036(2) ų, and Z = 4. It is isomorphous with its TaCl₄(PMe₃)₃ homolog, and the bond lengths and angles are very similar. Ta₂Cl₈(PMe₃)₄ forms cubic crystals (Im3) with a = 16.377(2), V = 4392(2) ų and Z = 6. It is thus isomorphous with its niobium homolog, and the internal dimensions are quite comparable. The Ta-Ta distance is 2.830(1) Å, consistent with the existence of a single bond.     

Bromine NQR study of structure and molecular torsional motion in N4P4Br8 and N3P3Br6

The bromine NQR spectrum of tetrameric bromocyclophosphazene, N₄P₄Br₈, has been studied in the temperature range from 77 to 300 K. The negative temperature coefficients of the resonance frequencies have been analysed using Bayer-Kushida-Brown equations. Torsional modes in the frequency range 10–15 cm^?1 are shown to characterise the observed motional averaging and are only slightly temperature dependent. The multiplicity and relative intensities of resonances in the trimer, N₃P₃Br₆, have been correlated with the known electron density distribution. The results for the bromo-derivatives are compared with those reported for the corresponding chloro-derivatives.     

Pressure dependence of 35Cl NQR in hexachloro- (N3P3Cl6) and octachloro- (N4P4Cl8) cyclophosphazenes

High pressure studies of ³⁵Cl NQR in the hexachlorocyclophosphazene N₃P₃Cl₆ and in the K- and T-forms of octachlorocyclophospha     

The Mn2(CO)10 catalyzed hydrogenation and hydroformylation of olefins

Mn₂(CO)₁₀ catalyze the homogeneous hydrogenation of 1- and 2-octene. In the presence of carbon monoxide and hydrogen at temperatures up to 235°, it is also a homogeneous hydroformylation catalyst. Cyclohexene yields the expected product, cyclohexylmethanol, at 235°, but at 200° the major product is cyclohexylmethyl formate.