Crystal structure of oxo(diperoxo)bipyridylmolybdenum(VI)

Yellow oxo(diperoxo)bipyridylmolybdenum(VI), C₁₀H₈MoN₂O₅, M_r = 332.1 crystallizes in the monoclinic space group P2₁/n, a = 6.261(3), b = 12.726(1) c = 13.752(3)A, β = 91.84(2)°, V = 1095.2(5)A³, Z = 4, D_c = 2.014(1) g/cm³, MoKα(λ = 0.7107A), μ = 11.8 cm^?1, T = 22(1)°C, R = 0.034, ωR = 0.040, number of reflections in least squares (F₀ > 2σ(F₀)) = 1125. The molybdenum coordination (distorted trigonal bipyramidal) is as in the corresponding chromium complex, C₁₀H₈CrN₂O₅ which has closely similar bond angles but is not isomorphous. The difference in MoN_apex and MoN_eq bond distances (2.312(5) and 2.199(5)A) is similar to that in the CrN_apex and CrN_eq distances (2.23(2) and 2.11(2)A). The MO distances for each peroxo ligand (ave. 1.910(2) and 1.950(2)A) are significantly different and slightly longer than those in the chromium complex as is the OO distance of 1.459(6)A. The latter is indicative of greater negative charge on the O₂ ligands, approaching that of O^2?₂ in the molybdenum complex.     

Vibro-conformational behaviour and normal coordinate analysis of fluorocarbonyl isocyanate,FC(O)NCO

Vibrational data of vapour, liquid and matrix-isolated fluorocarbonyl isocyanate, FC(O)NCO, were investigated. A subsequent normal coordinate analysis was performed for the A′ species of the predominant planar cis conformer (CO double bond cis with respect to the vicinal NC double bond). The following internal force constants were derived: f_CO= 12.88 mdyn Å⁻¹, f_CF=6.20 mdyn Å⁻¹ and F_CN= 4.42 mdyn Å⁻¹.     

The crystal and molecular structure of ortho-terphenylenemercury dimer, (C18H12Hg)2

C₃₆H₂₄Hg₂, hexabenzo[b,d,f,i,k,m][1,8] dimercuracyclotetradecene, M_r = 857.768, monoclinic, P2₁/n, a 17.315(3), b 16.576(2), c 10.545(6) Å, β 114.60(4)°, U 2751.65 ų, Z = 4, D_m 2.055, D_x 2.071 g cm⁻³, λ(Mo-K_α) 0.71069 Å, μ 107.51 cm⁻¹, F(000) = 1600, T 293 K; Final R = 0.041 for 4290 observed reflections with I > 3σ(I). The two CHgC angles are 175.5(3) and 175.6(4)°; average CHg distance, 2.088(13) Å.     

Crystal and molecular structure of 9-methyl-9-phenyl-9,10-dihydro-9-sila-3-azaanthrone

The crystal and molecular structure of 9-methyl-9-phenyl-9,10-dihydro-9-sila-3-azaanthrone has been determined from three-dimensional X-ray diffraction data. The title compound crystals are monoclinic, space group P2₁/b, a = 12.818(2), b = 16.508(2), c = 7.694(1) Å,γ = 105°, 34′(2), Z = 4 and D_cal = 1.278 g cm^?3. The structure was determined by direct methods and refined by full-matrix least-squares calculations in the block-diagonal anisotropic approximation for non-hydrogen atoms to R = 0.043 for 2190 independent reflections, registered at room temperature. This is the first crystal structure determination of a Si-dihydroanthracene derivative with two heterocycles and a planar carbon atom in the C10-position. The tricyclic fragment takes up a planar configuration, the silicon atom having a tetrahedral surrounding, with an endocyclic angle of 103.7(1)° and average bond length SiC, 1.862(1) Å. The CO, 1.220(2) Å, bond length in the carbonylic group exactly corresponds with the double bond length. Average distance NC is 1.335(3) Å, angle CNC, 116.5(2)°.     

Standard enthalpies of formation of bis(β-diketonate)cobalt(II) complexes: The mean (CoO) bond-dissociation enthalpies

The standard enthalpies of formation, at 298 K, of the 1-phenyl-1,3-butanedione (HBZAC) and 1,1,1-trifluoro-2,4-pentanedione (HTFAC) crystalline complexes of cobalt(II) were determined by precise solution—reaction calorimetry: ΔH⁰_f{Co(BZAC)₂,cr} = −632±6.0 kJ mol⁻¹ ΔH⁰_f{Co(TFAC)₂,cr} = −2140±10 kJ mol⁻¹. The average molar bond-dissociation enthalpies, <D>(CoO) were derived.     

Single crystal EPR study of Mn(II)-doped cis-catena-μ-sulphato-aquotris(imidazole)cadmium(II): Mn(II) in imidazole ligated low symmetry site

EPR of Mn(II)-doped single crystals of cis-catena-μ-sulphato-aquotris(imidazole)cadmium(II) has been studied in the temperature range 300-90 K. Mn(II) replaces Cd(II) substitutionally giving rise to two magnetically inequivalent sites. The large magnitude and high asymmetry component of the D-tensor is in accordance with the low symmetry of the substitutional site. Due to the non-first order nature of the spectrum all the work had to be carried out at Q-band frequency. Forbidden transitions corresponding to Δm_I = ± 1 and ±2 are observed for a number of orientations and their positions have been calculated by perturbation theory taking into account the second order admixtures due to cross terms in D and hyperfine coupling constant A. The spin—Hamiltonian parameters at 300 K are A = −83.5, D = −790.0, E = −80.4 (all in units of 10⁻⁴ cm⁻¹) and g = 2.0014.     

The crystal structure of eulytite Na3Bi5(PO4)6

The crystal structure of Na₃Bi₅(PO₄)₆ was solved using the single-crystal X-ray diffraction technique. The structural refinement has led to a reliability factor of R₁=0.0257 (wR₂=0.0533) for 428 independent reflections. This compound was found to crystallize in the cubic system (space group I4̄3d) with eulytite structure and the lattice parameters: a=10.097 (4) Å, V=1029.38 ų, Z=2, D_calc.=5.43 g cm⁻³ (D_exp.=5.32(5) g cm⁻³). The structure is characterized by the existence of one single general position (48a) for oxygen anions and two distinguished positions (16c) occupied by Na⁺ and Bi³⁺ cations, respectively. The site occupation factors are equal to 3/8 and 5/8 for sodium and bismuth, respectively. Although all PO distances are identical (1.529(4) Å), the OPO angles ranging from 108.06 (15) to 112.32 (31)°, show that [PO₄]³⁻ are rather distorted. Both sodium and bismuth cations are located in octahedral sites with corresponding mean distances of NaO and BiO equal to 2.428 and 2.386 Å, respectively. As expected from the close values of the ionic radii of Na⁺ and Bi³⁺, these distances lie in the same range.     

Polysilane derivatives of the transition metals II. The crystal and molecular structure of [tris(trimethylsilyl)silyl]pentacarbonylmanganese, (Me3Si)3SiMn(CO)5

The crystal and molecular structures of [tris(trimethylsilyl)silyl]pentacarbonylmanganese, (Me₃Si)₃SiMn(CO)₅, have been determined from three-dimensional X-ray data obtained by counter methods. The compound crystallizes in space group P$\text{1}$ of the triclinic system, with two molecules in a unit cell of dimensions: a = 9.002(2), b = 9.655(2), c = 15.639(3) Å, α = 83.66(1), β = 105.65(1), γ = 114.61(1)°.The observed and calculated densities are 1.20 (±0.03) and 1.23 g-cm^?3 respectively. Full-matrix least-squares refinement of the structure has led to a final value of the conventional R factor of 0.059 for the 818 independent reflections having F² > 3σ(F²).The coordination geometry about the manganese atom is approximately octahedral and, about the silicon atom bonded to the manganese atom, tetrahedral.The relative orientations of carbonyl and trimethylsilyl groups, when viewed down the MnSi bond, appear consistent with minimization of energy due to nonbonded interactions.Two of the equatorial carbonyl groups are displaced out of the equatorial plane towards the silicon ligand by 6°. The SiMn bond is 2.564(6) Å long and has no multiple character.     

Formation and molecular structure of permethylyttrocene methyl tetrahydrofuranate

The reaction of Cp^*₂YCl·THF with MeLi in THF at −80°C gives the monomeric Cp^*₂YMe·THF (1), which has been characterized by spectroscopy, elemental analyses and a single crystal X-ray diffraction study. Complex 1 crystallizes in the orthorhombic space group Pnam with lattice parameters a 17.881(4), b 8.621(2), c 15.095(3) Å, Z = 4, and D_calc 1.274 g cm⁻³. Least-squares refinement using 1056 independent observed reflections and 117 parameters gave a final R value of 0.071. The YC(σ) bond distance is 2.44(2) Å. IR and NMR spectra indicate an agostic interaction between the metal center and one of the CH bonds of the methyl ligand, but this could not be confirmed by the X-ray structure determination owing to disorder.     

X-ray photoelectron spectroscopy study of (Ca1−xLax)MnO2.97 (0.1 ≦ x ≦ 0.4)

The X-ray photoelectron spectroscopy (XPS) of perovskite-type (Ca_1−xLa_x)MnO_2.97 (0.1 ≦ x ≦ 0.4) was measured at room temperature. From the absolute values of the binding energy difference (ΔBE) of Ca2pO1s, La3dO1s, and Mn2pO1s, both the chemical bonding of MnO and CaO become more covalent, and that of LaO becomes more ionic with increasing x. The electron transfer of the MnOMn path is dominant, and the electrical properties are strongly influenced by the decrease of the electron transfer of the MnO(Ca,La)OMn path.     

Ab initio calculation of the 31P NMR shielding tensor for the series POaFb−(2a+b−5), a+b=4 and for HPO42−

Ab initio coupled Hartree-Fock perturbation theory (CHFPT) calculations on PO₄³⁻, PO₃F²⁻, PO₂F₂⁻, PF₃O, PF₄⁺ and HPO₄²⁻ using large polarized Gaussian bases satisfactorily reproduce experimental trends in ³¹P magnetic shielding anisotropies.Accurate evaluation of the shielding tensor for HPO₄²⁻ requires the inclusion of the H atom. Along the series PO_a F_b^{−(2a+b−5)} the calculated isotropic shielding shows a “sagging” pattern, i.e. the shielding is smallest for the intermediate member of the series PO₃F²⁻. The shielding for this species is, however, a strong function of the P-F and P-O distances. PO₃F²⁻ and HPO₄²⁻ are calculated to be similar in both average shielding and shielding anisotropy.     

Infrared and Raman spectra in the region below 1800 cm−1 of some amino acid chelates of the type cis-[(NH3)2Pt(amac)](NO3), where amacthe anions of glycine,l-alanine,l-aminobutyric acid,l-valine and l-norvaline

The IR and Raman spectra of a series of complexes of the general formula cis-[(NH₃)₂Pt(amac)](NO₃), where amac = the chelated anions, glycinate (gly), l-alaninate (ala), l-2-aminobutyrate (2-aba), l-valinate (val) and l-norvalinate (nval) have been recorded in the 1800-250 cm⁻¹ (IR) and 1800-100 cm⁻¹ (Raman) regions. Several characteristic bands have been identified or empirically assigned, based mainly on deuteration experiments and previous similar studies. The difference in ν^a_COO − ν^s_COO for the carboxylate group increases with increasing length of the aliphatic side chain of the amino acids, i.e. gly < ala < 2-aba < val < nval, indicative of the more covalent character of the PtO bond, the stability of the corresponding chelates being the opposite. If the tentative assignment of the νPtO bond made is correct, the above suggestion is confirmed by the variation of this frequency, which decreases in the above order.     

Crystal and molecular structure of [η5-C5(CH3)5]Co(O2C6H4), a cobalt(o-catecholate) complex

[η⁵-C₅(CH₃)₅]Co(O₂C₆H₄) crystallizes in the orthorhombic space group Pnma with a 12.942(4), b 12.902(4), c 8.543(3) Å, V 1426(1) ų, and Z = 4. Least-squares refinement of 1688 independent observed reflections, F(_obs) ? 2.5σ(F_obs), gives R_F 3.79 and R_wF 3.72%. The cyclopentadienyl ring contains two short (1.412(3) Å) and three longer (〈av〉 1.430(4) Å) CC bond lenghts, consistent with a slight preference for diolefin bonding. The O₂C₆H₄ fragment is best described as a catecholate with a CO bond distance of 1.338(3), and a CoO distance of 1.837(2) Å.     

Reaction of alkenes with trans-MeOIr(CO)(PPh3)2. Crystal and molecular structure of the pentacoordinate alkoxy-alkene iridium(I) complex,MeOIr(CO)(PPh3)2(TCNE)

The reaction of trans-MeOIr(CO)(PPh₃)₂ with TCNE (tetracyanoethylene) gives rise to the stable adduct MeOIr(CO)(PPh₃)₂(TCNE), the structure of which has been determined via a single-crystal X-ray diffraction study. This complex crystallizes in the centrosymmetric orthorhombic space group Pbca (D¹⁵_2h; No. 61) with a 17.806(4), b 20.769(4), c 20.589(6) Å, V 7614(3) ų and Z = 8. Diffraction data (Mo-K_α, 2θ = 5–45°) were collected on a Syntex P2₁ automated four-circle diffractometer and the structure was solved and refined to R_F 6.2% for 3502 data with |F₀| > 3σ(|F₀|) (R_F 4.3% for those 2775 data with |F₀| > 6 σ(|F₀|)). The central iridium atom has a distorted trigonal bipyramidal coordination geometry in which the methoxy group (Ir-OMe 2.057(8) Å) and carbonyl ligand (Ir-CO 1.897(14) Å) occupy axial sites with ∠MeOIrCO 174.7(4)°. The two triphenylphosphine ligands occupy equatorial sites (IrP(1) 2.399(3), IrP(2) 2.390(3) Å, ∠P(1)IrP(2) 110.32(11)° and the TCNE ligand is linked in an η² “face-on” fashion with the olefinic bond parallel to the equatorial coordination plane (IrC(4) 2.176(10), IrC(7) 2.160(12) Å) and lengthened substantially from its value in the free olefin (C(4)C(7) 1.539(17) Å).     

Studies of alkylmetal alkoxides of aluminium,gallium and indium : IV. The molecular structure of dimethylaluminium t-butoxide dimer by gas phase electron diffraction

The electron diffraction data for gaseous dimethylaluminium t-butoxide dimer are consistent with a molecular model of effective D_2h symmetry. The Al₂O₂ ring is planar and the three valencies of the O atoms are lying in a plane. The t-butyl groups undergo nonhindered or slightly hindered internal rotation. The most important bond distances and valence angles are: AlO = 1.864(6), AlC = 1.962(15), OC = 1.419(12), CC = 1.533(5) Å, ∠AlOAl = 98.1(0.7), ∠CAlC = 121.7(1.7) and ∠OCC = 110.4(0.5)°.     

The crystal structure of barium manganese(II) iron(III) fluoride BaMnFeF7

The crystal structure of the monoclinic compound BaMnFeF₇ has been determined: a = 553.2(1), b = 1098.0(2), c = 918.3(1) pm, β = 94.67(1)°, V = 555.9(3) × 10^?24 cm³, Z = 4. All atoms are in general positions of space group $\text{P2}{}_1\text{c}$, weighted R = 0.031, using 1771 independent single-crystal reflections with I > 2σ(I). The structure consists of edge-sharing dinuclear Mn₂F^6?₁₀ units (MnMn = 322.2 pm), linked via corners by intermediate FeF₆ octahedra, at which two cis ligands remain unbridged. The average distances in the distorted octahedra are MnF = 211.6 pm and FeF = 192.7 pm. The barium atoms are irregularly 12-coordinated with a mean distance BaF = 290.5 pm. The structure is discussed in relation to the trigonal weberite Na₂MnFeF₇ and others.     

The crystal and molecular structure of bis{μ[(tri-fluoromethyl)selono]manganese tetracarbonyl}

The crystal structure of [(CF₃Se)Mn(CO)₄]₂ has been determined by single crystal X-ray diffraction. The crystals are monoclinic, P2₁/c, a = 6.32, b = 15.35, c = 9.75 Å, β = 108.9°, Z = 2. The molecule possesses a crystallographic centre of symmetry, and is based on a planr [MnSe]₂ unit with four almost equal MnSe bonds (2.50 Å). The principal bonds length and angles are MnMn 3.74, SeSe 3.31 Å ; SeMnSe 83.1°, MnSeMn 96.9°; MnC (mean) 1.83, CO (mean) 1.16, SeC 1.97, CF (mean) 1.31 Å     

Derivative analysis of Raman spectra of liquid water in the OH (D) stretching region

Second derivative analysis of Raman spectra of H₂O, D₂O and HOD in liquid phase at room temperature for parallel and perpendicular polarized modes in the OH and OD stretching regions is reported. Five components obtained at approximately 3215, 3375, 3455, 3535 and 3640 cm⁻¹ for the second derivative plots of Raman spectra of liquid water are explained as due to the presence of three types of associated water species with (i) both OH bonds involved in moderately strong hydrogen bonds (SS), (ii) both OH bonds involved in weak hydrogen bonds (WW), and (iii) one OH bond involved in strong and one in weak hydrogen bonds (SW) respectively. The derivative plots obtained for Raman spectra of D₂O and HOD also contain features expected to be present on the basis of this model.     

Pentacoordinate iron(III) porphyrin carboxylates: Synthesis,physicochemical characteristics and x-ray crystal structure of acetato(5, 10, 15, 20-tetraparatolylporphyrinato) iron(III)

Carboxylatoiron(III) porphyrins have been synthesised by the action of carboxylic acids on the [(por)Fe]₂O dimers. ¹H NMR and ESR data of the isolated products are in accordance with pentacoordinate high spin 5/2 ferric complexes, the iron atom being displaced out of the plane of the porphyrin ligand. IR spectra show ν(CO) and ν(CO) bands separated by 356–409 cm^?1. The magnitude of this separation suggests coordination between the metal centre and the carboxylate group via one oxygen atom. Magnetic susceptibility measurements from 5 to 120 K lead to the value of μ = 5.88 B.M.. The X-ray structure of acetato (5, 10, 15, 20-tetra p-tolyporphyrinato) iron(III) confirms the above deductions. (tp MePP) Fe(CO₂CH₃). 0.5 CH₃COOH crystallises in the I2/c space group with unit cell parameters a = 24.464(8), b = 9.332(3), c = 37.174(4) Å, β = 90.49(2)°, V = 8485 ų, D_c = 1.27 g · cm^?3 and Z = 8. The crystal structure was refined to a conventional R(F) = 0.0584 and R_w(F) = 0.0653 for 5132 unique reflections with F₀ > 3σ(F₀). The iron atom is pentacoordinated by the four nitrogen atoms and one oxygen atom of the acetate group. It lies at 0.520(1) Å out of the porphinato plane and 0.485(1) Å out of the four nitrogen plane. The FeO bond length is 1.898(4) Å.