Equatorial Oxygen Atoms Research Articles

Perfluororganochalkogensäuren in hohen Oxidationsstufen

Perfluoroorganochalcogenic Acids in Higher Oxidation StatesPentafluoroethylseleninic acid is oxidized by KMnO4 in slightly alkaline aqueous solution to give K[C2F5SeO3]. With HClO4 the salt is converted into the free acid. Neutralisation of C2F5SeO3H with NaOH, Ag2O, NH3 + H2O provides the corresponding salts. The ethyl ester is made from Ag[C2F5SeO3] and C2H5I. Oxidation of C6F5TeC6F5 with concd. HNO3 yields C6F5Te(OH)ONO2 which on controlled hydrolyses gives (C6F5)2Te(OH)2. Strong acids like HClO4 or H2SO4 form mixed anhydrides like (C6F5)2Te(OH)ClO4 or (C6F5)2Te(OH)OS(O)2OTe(OH)(C6F5)2. For the latter compound a cyclic or noncyclic polycondensate form cannot be ruled out. Acidic 35% H2O2 solution oxidizes (C6F5)2Te(OH)2 at 40°C (48 h) to give (C6F5)2TeO2. This anhydride dissolves only in CF3SO3H forming (C6F5)2Te(OSO2CF3)4. It is soluble in CH3CN and reacts in solution with water to yield (C6F5)2Te(OH)2(OSO2CF3)2. Oxidation of C6F5TeTeC6F5 with concd. HNO3 provides oligomeric [C6F5Te(O)OH]x which still contains some HNO3. A single‐crystal X‐ray structure determination carried out on [(C6H5)4As][C2F5SeO3] shows convincingly that the central selenium atom is coordinated by three equivalent oxygen atoms with d(Se‐O) = 1.614(3) Å, proving that Se has the oxidation state VI.

Crown ether complexation of scandium(III). Formation and spectroscopic characterisation of ScCl2+–oxacrown species and crystal structures of two scandium dibenzocrowns

The reaction systems ScCl3–SbCl5–MeCN–crown ether(L), where L = 6,7,9,10,17,18,20,21 -octa-hydrodibenzo[b,k][1,4,7,10,13,16] hexaoxacyclooctadecine (dibenzo-18-crown-6), 6,7,9,10,12,13,20,21,23,24,26,27 -dodecahydrodibenzo [b,n][1,4,7,10,13,16,19,22] octaoxacyclotetracosine (dibenzo-24-crown-8) and 6,7,9,10,12,13,15,16,23,24,26,27,29,30,32,33-hexadecahydrodibenzo [b,q][1,4,7,10,13,16,19,22,25,28] decaoxacyclotriacontine (dibenzo-30-crown-10), have been investigated. Halide abstraction generates the ScCl2+ cation in situ which can be stabilised by macrocyclic complexation with the appropriate cyclic ether. The compound [ScCl2(dibenzo-18-crown-6)][SbCl6] was isolated as a white solid and characterised as the hexachloroantimonate (V) salt from microanalytical and spectroscopic (IR, 1H and 13C NMR) data. Entrapment of a trans-ScCl2 unit within the ring cavity involving five-co-ordination of the ring oxygen atoms is seen as the most likely arrangement. Removal of a further chloride ion from this compound, effected by the addition of SbCl5(three equivalents), provides [ScCl(dibenzo-18-crown-6)(MeCN)][SbCl6]2 as established by microanalytical and spectroscopic data, and similar cavity entrapment of a trans-ScCl(MeCN) unit has been discussed. Solution studies, as monitored by 1H NMR spectroscopy, indicate that complete removal of chloride ion from [ScCl(dibenzo-18-crown-6)(MeCN)][SbCl6]2 can be effected but only with a heavy excess (10 equivalents) of SbCl5. The compound [ScCl2(dibenzo-24-crown-8)(H2O)][SbCl6]·2MeCN 1 was isolated as red crystals and structurally characterised by X-ray diffraction studies. Crystals are monoclinic, space group P21/n, Z= 4 and R 0.0638. The structure consists of [ScCl2(dibenzo-24-crown-8)(H2O)]+ cations and [SbCl6]– anions with two solvent (MeCN) molecules trapped in the lattice. For the cation the ScIII co-ordination geometry is essentially pentagonal bipyramidal involving two axial chlorine atoms [Sc–Cl 2.387(4) and 2.397(4)A, Cl–Sc–Cl 173.8(2)°] and five equatorial oxygen atoms comprising four from the crown ether with Sc–O distances in the range 2.184(7)–2.297(7)(mean 2.25 A) and one from a co-ordinated water molecule [Sc–Owater 2.130(8)A]. The threaded ScCl2+ unit is located within the ring cavity but in an ‘off-centre’ position. Intracavity hydrogen bonding of the type Sc–OH2⋯ Oring is present with Owater⋯ Oring 2.65 and 2.75 A. The compound [ScCl2(dibenzo-30-crown-10)(H2O)2][SbCl6]· MeCN·H2O 2 was isolated as yellow needle crystals and characterised crystallographically as the hexachloroantimonate (V) salt. Crystals are triclinic, space group P, Z= 2 and R= 0.0639. There are two solvent molecules (MeCN and H2O) trapped in the lattice. In the [ScCl2(dibenzo-30-crown-10)(H2O)2]+ cations the ScIII ion is seven-co-ordinate, involving bonds to three oxygens from the crown ether, two chlorine atoms and two water molecules, and shows distorted pentagonal-bipyramidal geometry. The trans-ScCl2 unit [Sc–Cl 2.411 (3) and 2.419(3)A, Cl–Sc–Cl 169.3(2)°] is located in an annexe section of the ring with Sc–Oring bond distances ranging between 2.208(8) and 2.280(8)(mean 2.25 A), Sc–Owater 2.148(9) and 2.160(8)A. Both of the co-ordinated water molecules are involved in a complex pattern of intracavity hydrogen bonding of the type Sc–OH2⋯ Oring with one molecule forming three Owater⋯ Oring close contracts in the range 2.83–2.98 A and the other forming four such contracts in the range 2.75–3.00 A.

Structures of active conformations of Gi alpha 1 and the mechanism of GTP hydrolysis

Mechanisms of guanosine triphosphate (GTP) hydrolysis by members of the G protein alpha subunit-p21ras superfamily of guanosine triphosphatases have been studied extensively but have not been well understood. High-resolution x-ray structures of the GTP gamma S and GDP.AlF4- complexes formed by the G protein Gi alpha 1 demonstrate specific roles in transition-state stabilization for two highly conserved residues. Glutamine204 (Gln61 in p21ras) stabilizes and orients the hydrolytic water in the trigonal-bipyramidal transition state. Arginine 178 stabilizes the negative charge at the equatorial oxygen atoms of the pentacoordinate phosphate intermediate. Conserved only in the G alpha family, this residue may account for the higher hydrolytic rate of G alpha proteins relative to those of the p21ras family members. The fold of Gi alpha 1 differs from that of the homologous Gt alpha subunit in the conformation of a helix-loop sequence located in the alpha-helical domain that is characteristic of these proteins; this site may participate in effector binding. The amino-terminal 33 residues are disordered in GTP gamma S-Gi alpha 1, suggesting a mechanism that may promote release of the beta gamma subunit complex when the alpha subunit is activated by GTP.

Speciation of uranyl sorbed at multiple binding sites on montmorillonite

We have investigated the structures of U (VI) complexes as uranyl moieties sorbed onto a reference montmorillonite, SAz-1, using X-ray absorption fine structure spectroscopy (XAFS). The uranyl-loaded clays were prepared from aqueous solutions of uranyl nitrate in the pH range from 3.0 to 3.5. The U concentrations on the clay ranged from 1.7 to 34.6% of the reported cation exchange capacity (CEC = 1.2 meq/g) of the clay. For all samples, XAFS results indicate that there are two axial oxygen atoms at 1.78–1.80 Å, as expected for the uranyl moiety. The average numbers and distances of equatorial oxygen atoms about uranyl sorbed on the clay vary significantly as a function of surface coverage. At high coverage (34.6% CEC), the average number and distance of equatorial oxygen atoms are near those found for the fully hydrated uranyl species in aqueous solution. However, there are fewer equatorial oxygen atoms at a shorter average distance about uranyl sorbed at low coverage (1.7% CEC). At moderate coverage (7.3% CEC), the average number and distance of equatorial oxygen atoms are intermediate between those at higher and lower coverage. These changes suggest that sorbing U is reacting with at least three different sites on the clay as U concentration increases. The existence of multiple surface sites and sorption complexes which are structurally distinct from solution species need to be considered for rigorous modeling of sorption processes.

Positional and thermal disorder in the trigonal bipyramid of magnetoplumbite structure type SrGa12O19

Abstract The crystal structure of SrGa12019 has been refined at 473 K, 298 K and 160 K to R-values of 0.025, 0.023 and 0.030, respectively. The temperature dependence of the Debye-Waller factors shows that five-fold coordinated Ga3+ is randomly displaced from the center of its trigonal bipyramidal coordination polyhedron along positive and negative directions of the c-axis. The magnitude of displacement increases with the temperature. Although the Madelung part of lattice energy favours central location, this is prevented by repulsion of the three equatorial oxygen atoms.

Crystal structures of rat acid phosphatase complexed with the transition-state analogs vanadate and molybdate. Implications for the reaction mechanism.

The three-dimensional structures of complexes of recombinant rat prostatic acid phosphatase with the transition-state analogs vanadate and molybdate were determined to 0.3-nm resolution using protein crystallographic methods. The overall structure of the enzyme remains unchanged upon binding of the metal oxyanions; only local conformational differences in the positions of some side chains at the active site were found. The metal oxyanions bind in an identical fashion at the active site with trigonal bipyramidal coordination geometry. The metal ion is within coordination distance of the His12 side chain which is located at one of the axial positions. The three equatorial oxygen atoms interact with the conserved residues Arg11, Arg15, Arg79 and His257. Within hydrogen-bonding distance of the axial oxygen atom is the side chain of the conserved residue Asp258. The implications of these results for the catalytic mechanism of acid phosphatase are discussed.

Crystal and molecular structure of anhydrous copper(II) perchlorate

The structure of the pale blue-green Cu(ClO4)2 obtained by sublimation has been determined from single-crystal X-ray diffraction data. The structure was refined in the monoclinic space group P21/c, Z= 2, a= 4.584(1), b= 8.326(2), c= 8.015(1)A and β= 114.21(1)°R= 0.044 for 894 observed reflections. The copper has a distorted-octahedral environment with four equatorial oxygen atoms at short distances [1.96(1)A] and two long Cu–O axial interactions [2.46(1)A]. Perchlorate groups are bridging bidentate, and can be regarded as pseudo-tridentate, leading to a three-dimensional polymeric network of infinite cross-linked chains interacting through long Cu–O contacts.

Preparation, structure and catecholase-mimetic activity of two mononuclear ferrocenecarboxylate copper(II) complexes

The complexes trans-bis(ferrocenecarboxylato)bis(pyridine)copper(II) ( 2) and trans-bis(ferrocenecarboxylato)-bis(imidazole)copper( II) ( 3) have been prepared from the reaction of tetrakis(ferrocenecarboxylato)bis(tetra-hydrofuran)dicopper( II) ( 1) and the appropriate base. trans-Bis(ferrocenecarboxylato)bis(pyridine)copper(II) crystallizes as two isomers — one in which the carboxylate group coordinates in a chelating mode ( 2a) and one in which the carboxylate group coordinates as a monodentate ligand ( 2b). Complex , 2a crystallizes in the monoclinic space group P2 1/ c with a=14.761(5), b=5.922(2), c=15.913(6) Å, β=102.69(3)°, V=1357.1(8) Å, Z=2. The structure is compressed rhombic octahedral with four equatorial carboxylate oxygen atoms and two axial pyridine nitrogen atoms. The two CuO distances differ by approximately 0.2 Å suggesting that the carboxylate function bonds in an approximate chelating mode. Complexes 2b and 3both crystallize in the triclinic space group P1 with a=5.986(2), b=8.038(2), c=15.512(3) Å, α=104.42(2), β=93.11(2), γ=99.95(2)°, V=708.1(3) Å, Z=1, and a=7.475(3), b=9.296(3), c=10.090(3) Å, α=111.05(2), β=92.38(4), γ=101.69(3)°, V=635.7(4) Å 3, Z=1 for 2b and 3, respectively. The structures of 2b and 3 are best described as square planar with a CuN 2O 2 core having remote, weakly interacting, carboxylate oxygen atoms from the carboxylate groups at 2.53 and 2.76 Å from the copper atom for 2b and 3, respectively. The catalytic activities of 1, 2 and 3 toward the aerobic oxidation of catechol to o-quinone were determined. The activity of 2 is similar to that of 1 but much greater than that of 3. These differences are described in terms of the proposed requirement that two proximate metal atoms are involved in the catalytic process and the possible dimerization of 2 and not 3.

Stereoselective acetalization of 1,3-alkanediols controlled by intramolecular van der Waals attractive interactions and its application to an enantiodifferentiating transformation of .sigma.-symmetric 1,3,5-pentanetriols

Acetalization reactions of racemic bis(trimethylsilyl) ethers (R 1 R 2 CHCH(OTMS)CH(R 3 )CH 2 OTMS) with racemic menthone, under thermodynamically controlled conditions, stereoselectively give spiroacetal 2 (in which the substituent R 1 R 2 CH- is attached to the carbon adjacent to the axial oxygen atom with respect to the menthane ring) in preference to the diastereomeric spiroacetal 3 (in which the substituent is attached to the carbon adjacent to the equatorial oxygen atom)

Orientation and bonding of benzoic acid, phthalic anhydride and pyromellitic dianhydride on Cu(110)

The interaction of the polyimide precursor pyromellitic dianhydride (PMDA), and the related compounds benzoic acid and phthalic anhydride, with Cu(110) has been studied by high resolution electron energy loss spectroscopy (HREELS). For benzoic acid, deprotonation of the carboxylic acid group occurs on adsorption leading to the formation of a surface benzoate species (C 6H 5COO-). Bonding to the surface occurs through a carboxylate linkage via two equivalent oxygen atoms. The HREEL spectrum is characterised by an intense dipole active band, the symmetric OCO stretching vibration, at ∼ 1420 cm −1. The plane of the carboxylate group is aligned perpendicular to the surface as is the plane of the benzene ring. A similar species is found following exposure of Cu(110) to phthalic anhydride. The carboxylate linkage results from disruption of the anhydride ring with loss of the CO character (C 6H 4COO-). In the case of the dianhydride species PMDA, only one of the anhydride units is used in bonding to the surface; the second unit points away from the surface and is characterised by the symmetric anhydride stretch at 1255 cm −1 and weak OO stretching vibrations at ∼ 1850 cm −1. In both cases, changes in the intensity of some of the bands compared with benzoic acid suggest that the carboxylate group is tilted away from the surface normal due to an interaction between one of the carbons of the aromatic ring and the copper surface. This implies that the plane of the aromatic ring is now twisted out of the plane of the carboxylate group and, although still perpendicular to the surface, the axis is tilted to allow one of the β-carbon atoms to interact with the surface. In all cases, off-specular measurements at a primary electron energy of ∼ 8 eV are dominated by the intense CH stretching vibration. Measurements of the intensity of this mode, in the surface benzoate species, as a function of incident electron energy suggest that excitation of this mode occurs via a resonance scattering mechanism.

Cell-permeable non-hydrolyzable cAMP derivatives as tools for analysis of signaling pathways controlling gene regulation in Dictyostelium.

A novel class of cAMP derivatives were tested for binding to surface cAMP receptors (CAR), protein kinase A (PKA), and cAMP-phosphodiesterase (PDE) and for induction of three classes of cAMP regulated genes in Dictyostelium discoideum. These derivatives carry sulfur substitutions for either the axial (Sp) or equatorial (Rp) exocyclic oxygen atoms, while further modifications were introduced to provide specificity for binding to either CAR or PKA, and/or to increase lipophilicity and render the derivatives membrane-permeable. All derivatives bind weakly to PDE and are almost not degraded during incubation with Dictyostelium cells. One cAMP derivative, 6-thioethyl-purineriboside 3',5'-monophosphorothioate, Sp-isomer (Sp-6SEtcPuMPS), fulfills the criteria for selective activation of PKA in vivo. The compound enters Dictyostelium cells and reaches an intracellular concentration of 1 microM, sufficient to activate PKA, at an extracellular concentration of 30 microM, which is insufficient to activate CAR. Expression of cAMP-regulated prespore and prestalk genes and the aggregative PDE gene are effectively induced by CAR agonists and very poorly by PKA agonists. Even Sp-6SEtcPuMPS is ineffective to induce gene expression. These data not only indicate that surface cAMP receptors are the first targets for cAMP-induced gene expression, but argue against direct induction of expression of these genes by cAMP-induced PKA activation.

Crystal structure and magnetic properties of Cu(hfa)2NITPrn, a one-dimensional ferromagnet

A linear chain compound formed by copper(II) and a nitronyl nitroxide radical of formula Cu(hfa)2NITPrn, where hfa = hexafluoroacetylacetonate and NITPrn= 1-oxido-3-oxo-2-n-propyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidaz-ol-3-ium-1-yl has been synthesized. It crystallizes in the triclinic P1 space group with a= 10.071(3)A, b= 10.460(1)A, c= 16.003(2)A, α= 95.54(1)°, β= 78.58(2)°, γ= 63.27(2)°, and Z = 2. The Cu(hfa)2 moieties are bridged by the radicals which are coordinated to two metal ions through the two equivalent oxygen atoms on which the unpaired electron is equally delocalized. The product of magnetic susceptibility and temperature, χT, increases on lowering temperature and diverges as T tends to zero, as expected for an infinite chain of ferromagnetic coupled spins and a coupling constant between the metal and the radical J=–32.1(2) cm –1 has been estimated using the hamiltonian H=JS1·S2. The one-dimensional character has been confirmed also by single-crystal electron paramagnetic resonance spectra, but at low temperature the effects of weak inter-chain interactions are detected. The low-temperature magnetic behaviour of the title compound is compared with those of two other analogous derivatives comprising the methyl- and isopropyl-substituted radicals and the results confirm the hypothesis that the inter-chain dipolar interactions are mainly responsible for the deviation from one-dimensional behaviour.

Crystal and molecular structure and magnetic properties of a new µ-oxalato binuclear copper(II) complex containing mepirizole

The crystal and molecular structure of the new µ-oxalato binuclear copper(II) complex [(mpym)(H2O)(NO3)Cu(C2O4)Cu(NO3)(H2O)(mpym)]·2H2O 1[mpym = mepirizole = 4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6-methylpyrimidine] has been determined by X-ray diffraction methods. It consists of discrete binuclear entities where the copper atoms lie in a strongly elongated octahedral environment, surrounded by two nitrogen atoms (one from each ring of a mepirizole molecule) and two oxygen atoms of the bridging oxalato group in the equatorial plane and oxygen atoms of water molecules and nitrate ions in the axial positions. The binuclear entities are not centrosymmetric and the difference in the ligand environments of the copper(II) ions induces and energy separation between the two magnetic orbitals large enough to weaken the antiferromagnetic interaction (J=–142 cm–1) by approximately 60 cm–1 compared to that of symmetrical µ-oxalato binuclear copper(II) compounds. ESR, vibrational and electronic spectra are consistent with the above results.

Oxidation of a potassium monolayer on Ru(001) studied with photoemission, NEXAFS and vibrational EELS

The interaction of oxygen with a monolayer of potassium on a Ru(001) surface has been investigated with photoemission and NEXAFS. O 1s core-level data exhibit for low exposures of oxygen a single peak at 531.8 eV. This indicates together with the earlier observation of KO bond formation by EELS that a single K x O y species with equivalent oxygen atoms is formed. NEXAFS data indicate a partially filled O π* orbital and a strongly shifted σ-resonance. Photoemission, vibrational and Auger data suggest an ionic species which is close to potassium Superoxide with the OO bond oriented parallel to the surface.

Structural Characterization of the Pseudoenantiomeric cis‐Dioxo Osmium(VI) Esters of Chiral Diols with Cinchona Alkaloid Ligands

Starting point for the development of structure/activity correlations for the asymmetric dihydroxylation of olefins with OsO4 in the presence of chiral amines could be the structures of an osmate ester and its pseudoenantiomer. The esters were obtained from two related trans-disubstituted olefins, OsO4 and the isomeric alkaloids 1 and 2 (R′ = p-C1C6H4CO. aryl = 4-(6-methoxyquinolyl)). Particularly remarkable are the cis-dioxo coordination and the spatial proximity of the equatorial diolate oxygen atom and CO2 group of the chlorobenzoyl moiety.

Crystal structure of hexa(3,5-dicarboxypyridine)potassium tetrabromoaurate(III)

The title complex has been prepared, and characterized by X-ray crystallography. The crystals are rhombohedral, space groupR32, witha=20.954(5),c=9.753(1) A,Z=3, andR F =0.070 for 680 observed MoKα reflections. The structure consists of a packing of hexa(3,5-dicarboxypyridine) potassium cations and tetrabromoaurate(III) anions. The potassium atom is surrounded by equivalent oxygen atoms to form a KO6 octahedron with a very short K-O distance of 2.56(1) A. The AuBr 4 − group exhibits orientational disorder with a mean bond length of 2.38(1) A. Two symmetric strong hydrogen bonds (linear O⋯H⋯O and bent N⋯H⋯N) are found in the crystal structure. The nearly planar organic ligands are interlinked by hydrogen bonds to form parallel sheets which approximately correspond to the (003) family of planes. The potassium atoms lying in between these sheets connect them into a three-dimensional network.

Synthesis, structure, and solution behavior of [Na · 15-crown-5][Mn(CO) 5

The complex [Na · 15-crown05][Mn(CO) 5] was synthesized by the reaction of freshly prepared Na[Mn(CO) 5] with 15-crown-5 in toluene. The formation of two liquid layers indicative of a liquid clathrate was noted immediately. The pale green air-sensitive crystals of the complex belong to the monoclinic space group P2 1/c with a 7.880(2), b 19.157(8), c 13.549(4) Å, β 101.78(2)°, and D c 1.45 g cm −3 for Z = 4 formula units. The structure in the solid state is that of a dimer which resides on a crystallographic center of inversion. The [Mn(CO) 5] − units are bridged together by sodium cations. The latter are coordinated to one equatorial carbonyl oxygen atom, one axial carbonyl oxygen atom, and the five oxygen atoms of the crown ether. The two Na…O(carbonyl) contacts are 2.409 and 2.555 Å, and the sodium ion lies 0.88 Å out of the plane of the crown ether oxygen atoms.

UV-visible and raman spectroscopic studies of the hydrolysis of the uranyl(VI) ion in neutral and basic solutions at 25°C, 0,1 MPa

The hydrothermal reaction of UO3, WO3, and CsIO4 leads to the formation of Cs6[(UO2)4(W5O21)(OH)2(H2O)2] and UO2(IO3)2(H2O). Cs6[(UO2)4(W5O21)(OH)2(H2O)2] is the first example of a hydrothermally synthesized uranyl tungstate. It's structure has been determined by single-crystal X-ray diffraction. Crystallographic data: tetragonal, space group I4 cm, a=15.959(2)Å, c=14.215(1)Å, Z=4, MoKα, λ=0.71073Å, R(F)=2.84% for 135 parameters with 2300 reflections with I>2σ(I). The structure is comprised of two-dimensional ∞2[(UO2)4(W5O21)(OH)2(H2O)2]6- anionic layers that are separated by Cs+ cations. The coordination polyhedra found in the novel layers consist of UO7 pentagonal bipyramids, WO6 distorted octahedra, and WO5 square pyramids. The UO7 polyhedra are formed from the binding of five equatorial oxygen atoms around a central uranyl, UO22+, unit. Both bridging and terminal oxo ligands are employed in forming the WO5 square pyramidal units, while oxo, hydroxo, and aqua ligands are found in the WO6 distorted octahedra. In the layers, four (UO2)O5 polyhedra corner share with equatorial oxygen atoms to form a U4O24 tetramer entity with a square site in the center; a tungsten atom populates the center of each of these sites to form a U4WO25 pentamer unit. The pentamer units that result are connected in two dimensions by edge-shared dimers of WO6 octahedra to form the two-dimensional ∞2[(UO2)4(W5O21)(OH)2(H2O)2]6– layers. The lack of inversion symmetry in Cs6[(UO2)4(W5O21)(OH)2(H2O)2] can be directly contributed to the WO5 square pyramids found in the pentamer units. In the structure, all of these polar polyhedra align their terminal oxygens in the same orientation, along the c axis, thus resulting in a polar compound.

Model fluorogenic ligand-actinide and lanthanide coordination chemistry. Formation and crystal and molecular structure of [(i-C 3H 7O) 2P(O)CH(CH 2C 6H 4NO 2-p)C(O)N(C 2H 5) 2]UO 2(NO 3) 2

The ligands (i-C 3H 7O) 2P(O)CH(CH 2C 6H 4NO 2-p)C(O)N(C 2H 5) 2 ( 1), (i-C 3H 7O) 2P(O)CH(CH 2C 6H 4NH 2-p)C(O)N(C 2H 5) 2 ( 2) and (i-C 3H 7O) 2P(O)CH(CH 2C 6H 4N(CH 3) 2-p)C(O)N(C 2H 5) 2 ( 3) have been prepared and characterized by spectroscopic methods. Coordination chemistry of the ligands with UO 2(NO 3) 2·6H 2O, La(NO 3) 3·6H 2O and Er(NO 3) 3· 5H 2O has been surveyed and the complexes La(NO 3) 3·( 1) 2, Er(NO 3) 3·( 1) 2·H 2O, UO 2(NO 3) 2·( 1) and UO 2(NO 3) 2·( 2) have been isolated and characterized. A single crystal X-ray diffraction analysis of UO 2(NO 3) 2[(i-C 3H 7O) 2P(O)CH(CH 2C 6H 4NO 2-P)C(O)N(C 2H 5) 2] has been completed at 25 °C. The complex crystallized in the triclinic space groupP 1̄ with a = 9.524(2), b = 10.111(2), c = 17.692(2)Å, α = 70.27(1), β = 72.48(2), γ = 70.01(2)°, Z = 2, V = 1473.5Å 3, and Dx(calc.) = 1.82 g/cm 3. The structure was solved by using heavy atom techniques and least- squares refinement converged at RF = 5.4%, RwF = 6.6% on 2936 independent reflections with I> 2σ(I). The molecular structure was found to have a linear UO 22+ ion bonded to six equatorial oxygen atoms contributed by two bidentate nitrate ions and a bidentate carbamoylmethylphosphonate ligand. Important bond distances include UO(uranyl) avg. 1.73(1)Å, UO(P) 2.40(1)Å, UO(C) 2.39(1)Å, PO 1.49(1)Åand CO 1.28(2)Å.

Solid-state cadmium-113 solution NMR, shielding tensor components, and crystal and molecular structures of (bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl] oxide)bis(nitrato-O,O')cadmium(II), and (bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]aminebis(nitrato-O,O')cadmium(II)

The /sup 113/Cd NMR spectra have been observed for the title compounds, A and B, respectively, in methanol solution and in the solid state by magic-angle cross-polarization (MAS/CP) techniques. In solution A and B each give a single line at -96.3 and -95.2 ppM (deshielded relative to the 0.1 M Cd(ClO/sub 4/)/sub 2/ in D/sub 2/O standard), respectively, with half-widths at half peak heights of 7.1 and 1.5 ppM, respectively. In the solid state both compounds give a single line at -106 ppM with a half-width at half peak height of 6 and 3 ppM, respectively. Essentially the same species is present both in the solution and in the solid state. The components of the chemical shift tensor were calculated from the spinning side bands for both A and B and were found to be -170, -175, +31 and -169, -170, +12 ppM in a well-defined orientation to the pseudo-fivefold molecular axis. The crystal structures of A and B are made up of discrete molecules separated by ordinary van der Waals distances. The B molecules contain fairly regular pentagonal-bipyramidal Cd/sup 2 +/ with one equatorial and two axial nitrogen donors from the ligand and four equatorial oxygen donors from asymmetricmore » bidentate nitrate groups. The structure of A is made up of two different molecules, A and A', both of which have very distorted pentagonal bipyramidal Cd/sup 2 +/ with two axial nitrogens and one equatorial oxygen from the ligand and four equatorial oxygen atoms from symmetrical bidentate nitrate groups. X-ray data for the crystal structure of the two compounds are presented. 44 references, 5 figures, 3 tables.« less