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     

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 35Cl NQR spectra and structure of pentafluorophenyltetrachlorophosphorane C6F5PCl4

The low temperature structure of C₆F₅PCl₄ was confirmed by ³⁵Cl NQR measurements as ψ-trigonal bipyramidal, with the C₆F₅ group axial. Discrepancies were found with previously reported data, possible causes of these are discussed.     

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.     

Synthesis and molecular structure of [Au3Ru4(μ3-H)(CO)12(PPh3)3]

The title compound can be prepared in good yield by heating either [Ru₄(μ-H)₄(CO)₁₂] or [Au₂Ru₄(μ₃-H)₂(CO)₁₂(PPh₃)₂] with [AuMe(PPh₃)] in toluene. The related compound [Au₃Ru₄(μ₃-H)(μ-dppm)(CO)₁₂(PPh₃)] has also been prepared. Both trigoldtetraruthenium clusters undergo dynamic behaviour in solution, involving intramolecular rearrangement of the metal core, as revealed by variable temperature NMR studies. The crystal structure of [Au₃Ru₄(μ₃-H)(CO)₁₂(PPh₃)₃] has been established by an X-ray diffraction study. The metal atom core comprises a trigonal bipyramidal AuRu₄ unit with two AuRu₂ faces capped by gold atoms.     

Electrical conductivity of Th3P4-type EnLn2S4

Electrical conductivity measurements of Th₃P₄-type EuLn₂S₄ (Ln = LaGd) compounds have been made as functions of temperature and sulfur vapor pressure. These compounds are all p-type semiconductors, and their conductivities at room temperature have almost the same values for the specimens from EuLa₂S₄ to EuNd₂S₄ but increase on going from EnNd₂S₄ to EuGd₂S₄. In addition, the conductivity of EuGd₂S₄ is sensitive to sulfur vapor pressure and obeys the relationship . The mechanism of electrical transport in these compounds is discussed.     

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.     

The molecular structure of benzoylmethylidynetricobalt nonacarbonyl,C6H5C(O)CCo3(CO)9

The molecular structure of benzoylmethylidynetricobalt nonacarbonyl, C₆H₅C(O)CCo₃(CO)₉, has been determined by single crystal X-ray crystallography. The sample crystallized from heptane forms as monoclinic prisms of spae group P2₁/c, with a = 8.836(2), b = 14.097(10), c = 16.514(3), β = 103.37(6) and z = 2. The final R value was 0.053. The structure is regular and normal but does not aid in explaining the interesting properties of this cluster.     

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.     

Closest packing in dense oxides: The structure of a polymorph of Co3(AsO4)2

Crystals of Co₃(AsO₄)₂ were grown from the melt of a mixture of Co₂As₂O₇ and As₂O₅. The crystals are isostructural with Mg₃(AsO₄)₂ and are tetragonal with a = 6.858(2), c = 18.872(5) Å, Z = 6, and space group $\text{I}\text{4}\text{2d}$. A total of 1048 independent reflections were measured by diffractometer and used in the full-matrix refinement to a final R value of 0.069. The structure contains two distinct AsO₄ groups. Two of the cobalt ions are octahedrally coordinated and a third occupies a $\text{4}$ site with four short and four long CoO distances. The crystal structure of Co₃ (AsO₄)₂ is not based on the continuous three-dimensional closest packing of oxygen atoms. Nevertheless the number of oxygen atoms per cubic centimeter is 5.4 × 10²², which falls in the range of values for hexagonal and cubic closest packed structures. A better measure of the degree to which closest packing is achieved by a structure is suggested. It is based on an analysis of the polyhedra of oxygen atoms which surround each of the oxygen atoms in a structure and their relation to the polyhedra in ideally closest packed structures. In order to facilitate the analysis, polytopes of 11- and 12-vertex polyhedra were studied. A new decahexahedral 11-vertex polyhedron was found.     

WCl6/LiAlH4 Promoted transformation of imines into secondary and tertiary amines

The reaction of WCl₆/LiAlH₄ with imines, R′NCHR, gave tertiary amines, R′N(CH₂R)₂, and secondary amines, R′NHCHRCH₂R. Isotope labeling experiments revealed that the reaction involved two types of azatungstenacyclobutanes, $\text{WNR′CHRC}$HR and $\text{WCHRNR′C}$HR, produced from the reaction of an alkylidene tungsten intermediate with the imine CN double bond. Formation of these metallacyclobutanes is highly dependent on the solvent used.     

Protonation of cluster molecules: Bridging hydrogen sites in tetrahedral,octahedral and capped square pyramidal clusters: Be4H8, Be4H8

Main group structural models for tetrahedral and octahedral transition metal clusters containing bridging hydrogens are developed using the MNDO quantu     

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.     

Synthesis of π-(arene)metallocarboranes containing iron and ruthenium. Crystal structure of 3,1,2-(η6-1,3,5-(CH3)3C6H3)FeC2B9H11

The reaction of bis(arene)iron(II) salts (arene = mesitylene or hexamethylbenzene) or benzenedichlororuthenium(II) dimer with Tl[3,1,2-TlC₂B₉H₁₁] in THF produces neutral, air-stable π-(arene)(Fe, Ru)C₂B₉H₁₁ complexes in low or moderate yields. The metallocarboranes are formal analogues of [π-(arene)Fe, Ru)ⁿ⁺(C₅H₅)] species, and a single crystal X-ray structure of the title compound has established the closo sandwich geometry expected for the molecule on the basis of electron counting rules. The carborane cage was found to be disordered in the crystal but the essential features of the molecular geometry were not obscured. The mesitylene is symmetrically bound to the iron, and the Fe-arene (centroid) distance of 1.60 Å is similar to that found in the previously-characterized [(CH₃)₆C₆]Fe^I(C₅H₅) complex, despite the difference in the metal electronic configurations (d⁶ vs d⁷) and the change from the B₉C₂H₁₁^2? cage to C₅H₅^?. Crystals of 3,1,2-(η⁶-1,3,5-(CH₃)₃C₆H₃)FeC₂B₉H₁₁ are orthorhombic, space group Pn2₁a, with a = 12.638(4), b = 12.432(4), c = 9.686(3) Å.     

The crystal structure of Lu3S4: A new population wave structure

The monosulfide of lutetium loses lutetium preferentially upon vaporization in vacuo at 1750°C, and the quenched samples exhibit a new structure which is formed by an ordering of metal vacancies on the rock-salt type lattice.     

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.     

The molybdenum-molybdenum triple bond—XVII. Syntheses,spectroscopic and structural characterizations of Mo4F4(O—t-Bu)8 and Mo2F2(O—t-Bu)4(PMe3)2 (MoMo)

Hydrocarbon solutions of Mo₂(O—t-Bu)₆ and PF₃ (2 equiv) yield Mo₄F₄(O—t-Bu)₈, I, and PF₂(O—t-Bu). Compound I contains a bisphenoid of molybdenum atoms with two short MoMo distances, 2.26 Å, and four long MoMo distances, 3.75 Å, corresponding to localized MoMo triple bonding and non-bonding distances, respectively. The tetranuclear compound may be viewed as a dimer, [Mo₂(μ₂-F)₂(O-t-Bu)₄]₂, and addition of PMe₃ to hydrocarbon solutions of I yields Mo₂F₂(O—t-Bu)₄(PMe₃)₂, II, which contains an unbridged MoMo triple bond of distance 2.27 Å. Each molybdenum atom is coordinated to two oxygen atoms, one fluorine atom and the phosphorus atom of the PMe₃ ligand in a roughly square planar manner. The overall central Mo₂O₄F₂P₂ skeleton has C₂ symmetry and NMR studies (¹H, ¹⁹F and ³¹P) are consistent with the maintenance of this type of structure in solution. Infrared and electronic absorption spectral data are reported. These are the first compounds containing fluorine ligands attached to the (MoMo)⁶⁺ unit.     

Crystal structure of Fe2P2O7

Fe₂P₂O₇ crystallizes in the $\text{C}\text{1}$ space group with lattice parameters a = 6.649(2)Å, b = 8.484(2)Å, c = 4.488(1)Å, α = 90.04°, β = 103.89(3)°, γ = 92.82(3)°, and ?_cal = 3.86 g/cc. It is essentially isostructural with β-Zn₂P₂O₇. As in the Zn compound, the bridging oxygen atom in the P₂O₇ group shows a high anisotropic thermal motion. It appears that the P-O-P bond angle is linear as a result of extensive π bonding with the p orbitals on the bridging oxygen atom. The high thermal motion is vibration of the atom into cavities in the structure.     

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.