Lead tetrakis(imidazolyl)borate solids: anion exchange, solvent intercalation, and self assembly of an organic anion

The coordination polymer Pb[B(Im)(4)](NO(3))(xH(2)O), constructed by using sodium tetrakis(imidazolyl)borate and lead(II) nitrate solutions, is a layered material with the metal centers facing the interlayer spacing. As in naturally occurring layered minerals, this compound can readily undergo anion exchange and reversible intercalation of solvent water in the solid state with retention of crystallinity. We observed changes in solvent intercalation by (207)Pb solid state NMR (SSNMR) and thermogravimetric analysis (TGA). Stoichiometric exchange of (15)N nitrate for nitrate and iodide for nitrate is monitored by (15)N and (207)Pb SSNMR, and single crystals of the iodide-exchanged material Pb[B(Im)(4)]I were isolated. While the iodide compound can be obtained through facile exchange from the nitrate parent compound, the organic anion benzoate is placed in the interlayer spacing for nitrate under self-assembly conditions and forms an alternating monolayer in Pb[B(Im)(4)](C(6)H(5)COO)(0.5H(2)O). The ion exchange versus self-assembly behavior correlates with the structural differences in the three compounds. In both Pb[B(Im)(4)]I and Pb[B(Im)(4)](C(6)H(5)COO)(0.5H(2)O), the lead sites act as Lewis acids for the iodide and benzoate, respectively.     

Transition metal complexes of hydrotris(imidazolyl)borate anion

The preparation and characterization of the ligand potassium hydrotris(imidazolyl)borate and some of its complexes with transition metals is reported. These complexes have apparently an octahedral structure except the Cu(II) complex which seems to have a square planar geometry. The values of the ligand field parameters 10Dq, B and β have been evaluated for most of these complexes.     

Construction of a functional layered solid using the tetrakis(imidazolyl)borate coordinating anion

The coordination polymer Pb[B(Im)(4)](NO(3)), constructed by using tetrakis(imidazolyl)borate and lead(II) nitrate solutions, is a layered material with the metal centers facing the interlayer spacing. As in naturally occurring layered minerals, this compound can readily undergo anion exchange in the solid state with retention of crystallinity. We examined stoichiometric exchange of (15)N-nitrate for nitrate and iodide for nitrate by (15)N and (207)Pb SSNMR and confirmed retention of crystallinity by IR and powder XRD diffraction.     

Liquid membrane electrodes based on quaternary ammonium tetrakis(m-trifluoromethylphenyl)borates

Electrodes based on the appropriate salts give linear responses for 10^-1–10^-4 M tetramethylammonium and tetraethylammonium ions, with some selectivity against alkali metal ions. Use as indicator electrodes in titrations with tetraphenylborate solutions is outlined.     

Two-dimensional assembly of tetrahedral chalcogenide clusters with tetrakis(imidazolyl)borate ligands

A new two-dimensional inorganic-organic hybrid solid, formulated as Cd(17)S(4)(SPh)(25)B(im)(4) (SPh = benzenethiolate, im = imidazolate), has been synthesized under solvothermal conditions. The structure features a 6(3) network with 17-nuclear cadmium clusters linked by B(im)(4)(-) ligands. The compound is a semiconductor with the band gap of 2.66 eV and displays a green luminescence upon excitation at 390 nm.     

A multinuclear NMR study in the solid state and in solution of thallium(I) tris-(pyrazol-1-yl)borates (thallium scorpionates)

The ¹H, ¹³C and ¹⁵N NMR spectroscopic properties of six thallium tris-(pyrazol-1-yl)borates, including a tetrakis derivative, were determined. The results in solution were necessary to understand those, more complicated, in the solid state. A collection of ²⁰⁵Tl-¹⁵N and ²⁰⁵Tl-¹³C couplings was measured in the latter state. Among those, a very large coupling constant (between 194 and 282 Hz) has been measured on the carbon at the position 4 of the pyrazole ring in several compounds and particularly for the cyclobutyl derivative [Tl(Tp^Cbu)]. It has been assigned to a direct interaction of the 4-C-H ? Tl type and related to the X-ray structures, when available.     

Crystal structure and magnetic properties of hybrid materials self-assembled from the tetrakis(isothiocyanate)cobaltate(II) anion and trisubstituted benzyltriphenylphosphinium

A new hybrid material [BiF4BrBzTPP]₂[Co(NCS)₄] (1) (BiF4BrBzTPP⁺ = 2,6-bisfluoro-4-bromobenzyl-triphenylphosphinium, NCS^? = isothiocyanate) is synthesized and characterized by elemental analyses, IR, UV spectra, ESI-MS, molar conductivity, single crystal X-ray diffraction and magnetic susceptibility measurements. Compound 1 crystallizes in the monoclinic space group C2/c with a = 15.272(2) Å, b = 24.779(3) Å, c = 14.482(2) Å, β = 101.037(2)°, V = 5378.9(12) ų, Z = 4. The compound comprises two cations and one anion which exhibits a distorted tetrahedral coordination geometry. The short F...F, C...Br, and N...Br interactions and C-H...S hydrogen bonds consolidate the stacking of the molecules. Magnetic susceptibility measurements in the temperature range 2–300 K show that 1 exhibits weak antiferromagnetic coupling behavior.     

Diamagnetic group 6 tetrakis(di-tert-butylketimido)metal(IV) complexes

The addition of 4 equiv of LiN=C-t-Bu(2) to CrCl(3), MoCl(5), and WCl(6) in diethyl ether produced the complexes M(N=C-t-Bu(2))(4) (M = Cr, Mo, W). Single-crystal X-ray diffraction studies revealed that the molecules have flattened tetrahedral geometries with virtual D(2d) symmetry in the solid state. (1)H and (13)C NMR spectra indicated that the complexes are diamagnetic, and a qualitative MO analysis showed that the orthogonal π-donor and -acceptor orbitals of the ketimide ligand cooperatively split the d(xy) and d(z2) orbitals sufficiently to allow spin pairing in the d(xy) orbital. A more sophisticated quantum-mechanical analysis of Cr(N=C-t-Bu(2))(4) using density functional/molecular mechanics methods confirmed the qualitative analysis by showing that the singlet state is 27 kcal/mol more stable than the triplet state.     

Crystal structure of tetrakis(triphenylphosphine)palladium(0)

Crystal structure of widely employed precatalyst [Pd(Ph₃P)₄] is reported. It crystallizes in P-3 space group [a = 19.0828(8) and c = 26.4423(18) Å] with six molecules per unit cell. It is demonstrated that the phase purity of this important compound can now be routinely controlled via powder X-ray diffraction analysis.     

Tetrakis(methylimidazole) and tetrakis(methylimidazolium) calix[4]arenes: competitive anion binding and deprotonation

Neutral tetrakis(methylimidazole) (1) and the novel cationic tetrakis(methylimidazolium) (2) calixarenes have been prepared and their solid-state and solution behaviour examined. The neutral imidazole forms a mono-zwitterion at elevated temperature, a feature that has been observed both in solution and in the solid-state. The cationic imidazolium exhibits a range of hydrogen bond interactions with anions, with the titration curves upon binding to basic anions suggesting sequential binding to both the upper and lower rims.     

Separtation of metal tetrakis(p-tolyl)porphine complexes by reversed-phase high-performance liquid chromatography

Summary The feasibility of reversed-phase high-performance liquid chromatography for the separation of several metal complexes ofmeso-tetrakis(p-tolyl)porphine (TTP) is described. A combination of an octadecyl-bonded stationary phase with a non-aqueous polar mobile phase, such as an acetone-acetonitrile mixture, has proved effective for the separation. Thus, the TTP complexes of Mg, VO, Ni, Cu, Zn, and Pd and also TTP free acid were successfully separated in about 10min on a Li-Chrosorb RP-18 column (7m, 250×4mm i.d.) with a 7030 (vol/vol) mixture of acetone and acetonitrile at a flow-rate of 1 mlmin^–1.     

The crystal structure of Thorium(IV)tetrakis(trifluoroacetylacetonate)

The crystal structure of the compound thorium(IV)tetrakis(trifluoro-acetylacetonate) was determined by means of a threedimensional X-ray analysis. The space group is C2/c and the cell dimensions are a = 25,05 Å, b = 6.43 Å, c = 21.3 Å, β = 125.4°, with Z = 4. The thorium atom is coordinated by 8 oxygen atoms in the form of an 1111 (D₄–422) antiprism. The mean of the Th–O distances is 2.39 Å with a standard deviation ± 0.04 Å. The trifluoroacetylacetonate rings are approximately planar, except for the CH₃ and CF₃ groups which show significant deviations. The Th–O bonds form angles of approximately 72° and 50° with the theoretical 8 -axis of the antiprism. The structure is stabilized by VAN DER WAALS contacts between neighbouring molecules. The refinement of the atomic positions, the anisotropic temperature parameter of thorium and isotropic temperature parameters of all the other atoms by the least squares method, has given a reliability index of 0.148.     

Crystal structure and triboluminescence of tetraethylammonium tetrakis(thenoyltrifluoroacetonato)europium

An atomic structure of complex Et₄N[Eu(ТТA)₄] (TTA is the thenoyltrifluoroacetonate anion, Et₄N⁺ is the tetraethylammonium cation) possessing strong luminescence and triboluminescence was determined by X-ray crystallography. The crystal system of centrosymmetric crystals is monoclinic: a = 10.2495(1) Å, b = 20.2162(3) Å, c = 23.5788(3) Å, β = 102.551(1)°, space group P2₁/c, Z = 4, d _calc = 1.625 g cm^–3. The crystals of the compound have an isle structure, which comprises individual complex anions [Eu(TTA)₄]^– and tetraethylammonium cations Et₄N⁺. The structural aspects of a possible model for the formation of triboluminescent properties were considered, the role of cleavage planes and disordering was discussed.     

Synthesis of tetrakis(triethylsiloxy)titanium and tetrakis(triethylsiloxy)tin

Summary By the metathetic reaction of sodium triethylsiloxide with titanium tetrachloride and with tin tetrachloride, tetrakis(triethylsiloxy)titanium and tetrakis(triethylsiloxy)tin were synthesized.     

Formation of superoxide anion on aerial oxidation of Cu(II)-porphyrinogen in the synthesis of tetrakis(cyclohexyl)porphyrinogenCu(III) anion

Tetraethylammonium-tetrakis(cyclohexyl)porphyrinogenCu(II) (1) is spontaneously oxidized by aerial oxygen to the corresponding Cu(III) (2) species, producing 1 equiv of O2(-). Steric crowding of the peripheral hydrogens in 1 prevented any direct Cu-O2 bond formation in the oxidation process, which suggests an outer-sphere electron transfer reaction.     

Dirubidium hexaaquacobalt(II) tetrakis(hydrogen phthalate) tetrahydrate and coordination modes of the hydrogen phthalate anion

The title compound, Rb₂[Co(H₂O)₆](C₈H₅O₄)₄·4H₂O, consists of nearly regular octahedral [Co(H₂O)₆]²⁺ cations with the Co^II cations on the inversion centre (special position 2a), Rb⁺ cations, hydrogen phthalate (Hpht⁻) anions and disordered water molecules. The Rb⁺ cation is surrounded by nine O atoms from Hpht⁻ anions and water molecules, with a strongly deformed pentagonal–bipyramidal geometry and one apex split into three positions. The crystal packing is governed by numerous hydrogen bonds involving all water molecules and Hpht⁻ anions. In this way, layers parallel to the ab plane are formed, with the aromatic rings of the Hpht⁻ anions esentially directed along the c axis. While Hpht⁻ anions form the outer part of the layers, disordered water molecules and Rb⁺ cations alternate with [Co(H₂O)₆]²⁺ cations in the inner parts. The only interactions between the layers are van der Waals forces between the atoms of the aromatic rings. A search of the Cambridge Structural Database for coordination modes and types of hydrogen‐bonding interaction of the Hpht⁻ anion showed that, when uncoordinated Hpht⁻ anions are present, compounds with intermolecular hydrogen bonds are more numerous than compounds with intramolecular hydrogen bonds. For coordinated Hpht⁻ anions, chelating and bridging anions are almost equally common, while monodentate anions are relatively scarce. The same coordination modes appear for Hpht⁻ anions with or without intramolecular hydrogen bonds, although intramolecular hydrogen bonds are less common.