A new monoclinic phase in the Fe2O3TiO2 system. I. Structure determination and Mössbauer spectroscopy

Single crystals with compositions within the Fe₂O₃TiO₂ system were grown from a flux containing various amounts of the basic oxides. Apart from the known pseudobrookite (Fe₂TiO₅) and rutile (TiO₂) structures, a new monoclinic polytype of Fe₂TiO₅ was found, which was isostructural with V₃O₅. The structure was determined by X-ray analysis and Mössbauer spectroscopy contributed data on hyperfine parameters and the magnetic ordering temperature.     

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 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.     

Stereochemical nonrigidity of the square complex (PPh3)2Pt(HgGePh3)(GePh3)

³¹P, ¹⁹⁵Pt and ¹⁹⁹Hg NMR spectra of complex (PPh₃)₂Pt(HgGePh₃)(GePh₃) (I) have been studied. The spectra at temperatures below ?40°C prove that (I) is a cis-isomer with the square-planar coordination of the Pt atom. The reversibility of temperature dependences of spectra, insensitivity of line shape to the solvent, concentration and presence of free phosphine establish the fluxional behaviour of (I). The activation parameters of the intramolecular rearrangement which is realized, most probably, through a digonal twist, are: Δ^≠₂₉₈ = 51.5 ± 2.9 kJ/mol, ΔH^≠ = 59.3 ± 2.9 kJ/mol, ΔS^≠ = 26.2 ± 9.7 J/mol. K.     

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.     

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.     

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.     

Synthesis and structural characteristics of fac-ReCl3[P(OEt)3]3 a route to the phosphite complexes

Reaction of the oxo-complex ReOCl₃(PPh₃)₂ with an excess of triethylphosphite yields a deoxygenated rhenium phosphite complex fac-ReC1₃[P(OEt)₃]₃; its structure was confirmed by ¹H NMR and IR spectroscopy.     

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 production of Cr(NH3)6 from the acid catalysed hydrolysis of Cr(NH3)5(NCO)

The rate of the reaction

has been investigated at 40–65°C with [HClO₄] varying from 0.04 to 0.6 M (μ = 0.6 M, NaClO₄). The observed rate law has the form: -d[Cr(NH₃)₅(NCO)²⁺]/dt = k_obs[Cr(NH₃)₅(NCO)²⁺] where k_obs = a[H+]²{1 + b[H⁺]²} and ^?1 at 55.0°C, a = 0.36 M^?1 s^?2 and b = 6.9 × 10^?3 M^?1 s^?1. The rate of loss of Cr(NH₃)₅(NCO)²⁺ increases with increasing acidity to a limiting value (at [H⁺] ～ 0.5 M) but the yield of Cr(NH₃)₆³⁺ decreases with increasing [H⁺] and increases with increasing temperature. In the kinetic studies the maximum yield of Cr(NH₃)₆³⁺ was 35% but a synthetic procedure has been developed to give a 60% yield.     

Mechanism of formation of (η-C5H5)2NbH3 from the reaction of (η-C5H5)2NbCl2 with hydridoaluminate reducing agents

The mechanism of the transformation of (η⁵-C₅H₅)₂NbCl₂ to (η⁵-C₅H₅)₂NbH₃ by hydridoaluminate reducing agents has been investigated. Results suggest disproportionation of a niobium(IV) hydrite, leading to the trihydride product and a niobium(III) hydridoaluminate, (η⁵-C₅H₅)₂NbH₂AlR₂, which in turn is converted to the trihydride on hydrolysis. (η⁵-C₅H₅)₂NbH₂AlH₂ has been isolated; deuterium labelling shows that hydrogens exchange between ring and metal-bridging positions in this molecule.     

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 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.     

Analytical reactions of substituted cyanoferrates : I. Na3[Fe(CN)5(NH3)]

The reagent pentacyanoamminoferrate (PCAF) in its aqueous reactions with some common cations and anions produces colored species in solution. It has been observed that the reactions of Fe³⁺, Fe²⁺, Co²⁺, VO²⁺, Mo⁶⁺, S₂O₃²⁻, and NO₂⁻ are sensitive enough to permit their colorimetric determinations. In addition, the reagent has been found useful in the simultaneous trace analysis of Fe³⁺ and VO²⁺ present in the same solution.A comparative study has been made of the reactions of PCAF and the other unsubstituted cyanoferrates(II) and (III).     

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.     

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 synthesis and decarbonylation of (η5-C5H5)Mo(Co)2(COCH3)E(C6H5)3, where E is arsenic or antimony

The synthesis of the title compounds by reaction of (η⁵-C₅H₅)Mo(CO)₃CH₃ with excess As(C₆H₅)₃ or Sb(C₆H₅)₃ in CH₃CN is described. Thermal decarbonylation results in the preferential ejection of As(C₆H₅)₃ or Sb(C₆H₅)₃ from the new acetyl complexes, which accounts for the failure of previous attempts to synthesise the acetyl complexes. Photolytic decarbonylations lead to new-alkyl complexes (η⁵-C₅H₅)Mo(CO)₂(CH₃)E(C₆H₅)₃. IR and NMR data for the new complexes are tabulated.