Seesaw Geometry Research Articles

Unraveling Strong Supramolecular Assembly of a Novel Pyrene Based Hg(II)‐complex: Insights from Hirshfeld Surface, FMO and Molecular Electrostatic Potential (MEP) Analyses

AbstractA rare pyrene‐based coordination compound of Hg(II) [Hg(L)2] (1) (where, HL=2‐((Pyren‐1‐ylmethylene)amino)benzenethiol) was synthesized and characterized by single crystal X‐ray diffraction (SC‐XRD) analysis. Crystallographic analysis revealed that complex 1 has seesaw geometry with HL coordinated as a bidentate ligand to a metal ion. The role of weak forces like π⋅⋅⋅π and CH⋅⋅⋅π interactions in influencing the self‐assembly process appears to be of importance. The electronic structure of the complex was predicted using DFT calculations with mixed basis set. DFT calculated structural parameters are in good agreement with the experimentally obtained parameters from XRD. Molecular reactivity and stability of the complex has been assessed through frontier molecular orbital analysis. Evaluation of molecular electrostatic potential (MEP) displays the electrophilic and nucleophilic reactivity sites. The Hirshfeld surface analysis clearly indicates C−H⋅⋅⋅π interactions and π⋅⋅⋅π stacking interactions are responsible to extend the supramolecular network of the complex. Analyses of the Finger print plots suggest that H⋅⋅⋅H and H⋅⋅⋅C contacts are major interactions for stabilizing the molecular crystal.

Synthesis of a potassium capped terminal cobalt-oxido complex.

An unusual example of a potassium capped terminal cobalt-oxido complex has been isolated and crystallographically characterized. The synthesis of [tBu,TolDHP]CoOK proceeds from a previously reported parent compound, [tBu,TolDHP]CoOH, via deprotonation with KOtBu. Structural and electronic characterization suggest a weakly coupled dimer in a distinct seesaw geometry with a Co(III) oxidation state and a non-innocent radical ligand.

Germanium and Tin Precursors for Chalcogenide Materials Containing N-Alkoxy Thioamide Ligands.

This study describes the synthesis of germanium and tin complexes Ge(mdpaS)2 (1), Ge(edpaS)2 (2), Ge(bdpaS)2 (3), Ge(empaS)2 (4), Sn(mdpaS)2 (5), Sn(edpaS)2 (6), Sn(bdpaS)2 (7), and Sn(empaS)2 (8) (mdpaSH = (Z)-N-methoxy-2,2-dimethylpropanimidothioic acid; edpaSH = (Z)-N-ethoxy-2,2-dimethylpropanimidothioic acid; bdpaSH = (Z)-N-(tert-butoxy)-2,2-dimethylpropanimidothioic acid; empaSH = (Z)-N-ethoxy-2-methylpropanimidothioic acid), using newly designed N-alkoxy thioamide ligands as precursors for metal chalcogenide materials. All complexes were characterized using various analytical techniques, and the single-crystal structures of complexes 5 and 7 revealed a distorted seesaw geometry in the monomeric SnL2 form. Thermogravimetric (TG) curves showed differences between Ge compounds, which exhibited single-step weight losses, and Sn compounds, which exhibited multistep weight losses. As a result, we suggest that the synthesized complexes 1-8 are potential precursors for group IV metal chalcogenide materials.

Pressure Induced Alteration and Stabilization of Intermolecular Stacking in Square-planar Osmium tetracarbonyl.

Osmium carbonyls are well known to form stable 18-electron complexes like Os(CO)5 , Os2 (CO)9 and Os3 (CO)12 having both bridging and terminal carbonyls. For osmium tetra-carbonyl, Os(CO)4 solid-state packing significantly alters the ground-state structure. The gas-phase stable see-saw geometry converts to a square-planar structure in solid state. Highly efficient intermolecular stacking between Os(CO)4 units assists this transformation. Each Os(CO)4 molecule is stacked in a staggered orientation with respect to each other. Pressure induces a [Xe]4f14 5d6 6s2 (S=2)→[Xe]4f14 5d8 (S=0) electronic transition in osmium stabilize a square planar osmium tetra-carbonyl. Under the influence of isotropic pressure, the molecules not only come closer to each other but their relative orientations also get significantly altered. Calculations show that at P=1 GPa and above, the eclipsed orientation for the intermolecular stacking gets preferred over the staggered form. The staggered→eclipsed intermolecular stacking orientation under pressure is shown to be controlled by London dispersion interactions.

Embellished photosensitive Schottky barrier diode functionality of Ni(II)/Pb(II)-Salen complex with SCN− spacers: Insights from experimental and theoretical rationalization

This research article explores the synthesizing, structural characterizing, and photosensitive Schottky diode behaviour (PSBD) of one new hetero-nuclear Ni(II)/Pb(II)-Salen complex, [Ni2(L)Pb(μ-1,3-SCN)2(H2O)]2. The complex utilizes various analytical methods for characterization purposes, including single-crystal X-ray diffraction (SCXRD). Crystals have formed in the monoclinic space group P21/n within the compound. The complex asymmetric unit contains a deprotonated ligand (L2−), two Ni(II), one Pb(II), two SCN− ions, and Ni(II) metal coordination by H2O molecule. The crystallographic structure has octahedral and see-saw geometries around the Ni(II) and Pb(II) metal ions. The crystal structure reveals remarkable supramolecular interactions, with significant S⋯H contacts (13 %) evident from the Hirshfeld surface (HS) and 2-D fingerprint plots. The calculated optical band gap (3.14 eV) and UV–Visible measurement support the semiconductor behaviour. In addition, the compound shows electrical conductivity and photosensitivity (dark & light), suggesting potential applications in optoelectronic devices. The complex transports charge through space via a hopping process. The extensive experimental investigations indicate that exposure to visible light increases electrical conductivity compared to dark conditions, popularly known as PSBD behaviour. The complex conductivity function substantiates the DFT-based DOS, PDOS, and OPDOS plot analysis. Therefore, the heteronuclear complex has been successfully used in thin-film active devices despite technological challenges.

Influence of proline and hydroxyproline as antimicrobial and anticancer peptide components on the silver(I) ion activity: structural and biological evaluation with a new theoretical and experimental SAR approach.

Silver(I) complexes with proline and hydroxyproline were synthesized and structurally characterized and crystal structure analysis shows that the formulas of the compounds are {[Ag2(Pro)2(NO3)]NO3}n (AgPro) (Pro = L-proline) and {[Ag2(Hyp)2(NO3)]NO3}n (AgHyp) (Hyp = trans-4-hydroxy-L-proline). Both complexes crystallize in the monoclinic lattice with space group P21 with a carboxylate bidentate-bridging coordination mode of the organic ligands Pro and Hyp (with NH2+ and COO- groups in zwitterionic form). Both complexes have a distorted seesaw (C2v) geometry around one silver(I) ion with τ4 values of 58% (AgPro) and 51% (AgHyp). Moreover, the results of spectral and thermal analyses correlate with the structural ones. 1H and 13C NMR spectra confirm the complexes species' presence in the DMSO biological testing medium and their stability in the time range of the bioassays. In addition, molar conductivity measurements indicate complexes' behaviour like 1 : 1 electrolytes. Both complexes showed higher or the same antibacterial activity against Bacillus cereus, Pseudomonas aeruginosa and Staphylococcus aureus as AgNO3 (MIC = 0.063 mM) and higher than silver(I) sulfadiazine (AgSD) (MIC > 0.5 mM) against Pseudomonas aeruginosa. In addition, complex AgPro exerted a strong cytotoxic effect against the tested MDA-MB-231 and Jurkat cancer cell lines (IC50 values equal to 3.7 and 3.0 μM, respectively) compared with AgNO3 (IC50 = 6.1 (5.7) μM) and even significantly higher selectivity than cisplatin (cisPt) against MDA-MB-231 cancer cell lines (SI = 3.05 (AgPro); 1.16 (cisPt), SI - selectivity index). The binding constants and the number of binding sites (n) of AgPro and AgHyp complexes with bovine serum albumin (BSA) were determined at four different temperatures, and the zeta potential of BSA in the presence of silver(I) complexes was also measured. The in ovo method shows the safety of the topical and intravenous application of AgPro and AgHyp. Moreover, the complexes' bioavailability was verified by lipophilicity evaluation from the experimental and theoretical points of view.

4,4-Bis(isopropylthio)-1,1-diphenyl-2-azabuta-1,3-diene Adducts with Cadmium(II), Mercury(II) and Copper(I) Iodides: Crystal, Molecular and Electronic Structures of d10 Transition Metal Chelate Complexes

The thioether-functionalized 2-azabutadiene (iPrS)2C=C(H)-N=CPh2 L ligates to CdI2 and HgI2 to form the chelate compounds [CdI2{(iPrS)2C=C(H)-N=CPh2] (1) and [HgI2(iPrS)2C=C(H)-N=CPh2] (2). Their crystal structures were solved via X-ray diffraction. Both crystallize in the non-centrosymmetric space groups: monoclinic P21 (1) and orthorhombic P212121 (2), respectively. The closed-shell d10 metal centers are four-coordinated (two iodides and S and N coordinating atoms from the ligand L) in both complexes. The geometrical indexes τ indicate that a highly distorted trigonal pyramidal is adopted for 1 and a seesaw geometry for 2. The comparative nature of metal–ligand bonds is discussed on the basis of metric parameters and of QT-AIM (quantum theory of atoms in molecules) calculations. L was also treated with CuI to obtain the dinuclear species [LCu(μ2-I2)CuL] (3), in which the two Cu(I) centers are linked by a short metal–metal bond. The geometric and electronic properties of 3 are compared with those of 1 and 2.

Sigma-Hole and Lone-Pair-Hole Site-Based Interactions of Seesaw Tetravalent Chalcogen-Bearing Molecules with Lewis Bases.

For the first time, sigma (σ)- and lone-pair (lp)-hole site-based interactions of SF4 and SeF4 molecules in seesaw geometry with NH3 and FH Lewis bases were herein comparatively investigated. The obtained findings from the electrostatic potential analysis outlined the emergence of sundry holes on the molecular entity of the SF4 and SeF4 molecules, dubbed the σ- and lp-holes. The energetic viewpoint announced splendid negative binding energy values for σ-hole site-based interactions succeeded by lp-hole analogues, which were found to be -9.21 and -0.50 kcal/mol, respectively, for SeF4···NH3 complex as a case study. Conspicuously, a proper concurrence between the strength of chalcogen σ-hole site-based interactions and the chalcogen's atomic size was obtained, whereas a reverse pattern was proclaimed for the lp-hole counterparts. Further, a higher preference for the YF4···NH3 complexes with elevated negative binding energy was promulgated over the YF4···FH ones, indicating the eminent role of Lewis basicity. The indications of the quantum theory of atoms in molecules generally asserted the closed-shell nature of all the considered interactions. The observation of symmetry-adapted perturbation theory revealed the substantial contributing role of the electrostatic forces beyond the occurrence of σ-hole site-based interactions. In comparison, the dispersion forces were specified to govern the lp-hole counterparts. Such emerging findings would be a gate for the fruitful forthcoming applications of chalcogen bonding interactions in crystal engineering and biological systems.

1-D MOF [Ag2(C10H10N3O3S)2(C4H8N)2]n: photocatalytic treatment, crystallographic evaluation, ADMET parameters, CT-DNA and anticancer activity

Newly synthesized dinuclear crystalline polymer, the silver complex of bidentate Sulfamethoxazole (Ag-SMX) in the presence of secondary ligand pyrrolidine has been characterized by elemental, spectral (1H-NMR spectra, FT-IR spectra, UV–Vis spectra.), powder XRD, and single-crystal X-ray diffraction (single-crystal) analysis. The synthesis molecular structure of the dinuclear [Ag2(C10H10N3O3S)2(C4H8N)2]n complex reveals a one-dimensional polymeric chain with seesaw geometry (τ4 = 0.71): two silvers interlink each other by argentophilic interaction with Ag1…Ag2 separation distance of 3.0047(6) Å. The Hirshfeld surfaces (HS) and 2D fingerprint plots were used to examine the interconnects in the crystal packing. Molecule properties including MEP, MPA, HOMO-LUMO energy, and global reactivity descriptor parameters were computed to understand the molecule’s stability. From ADMET parameters, human Intestinal Absorbance data revealed that the compound has the potential to be well absorbed, and also Ag-smx complex cannot cross the blood-brain barrier (BBB). The capacity of the silver complex to interact with CtDNA was investigated using absorption spectroscopy and viscosity tests. The interaction between CT-DNA reveals that the Ag-SMX complex exhibits the strongest binding affinity among all known sulfonamide derivatives and their metal complexes. The silver complex has higher inhibitory action than the free SMX ligand, according to data from a panel of gram (+ve) and gram (-ve) organisms’ minimum inhibitory concentrations. In vitro cytotoxicity investigation revealed that the IC50 value for Ag-SMX is 57.12 g/mL and for SMX is 100.90 g/mL against human lung cancer cell line (A549). This study revealed that, when compared to SMX free-ligand, Ag-SMX is the most effective in terms of cytotoxicity toward the human lung cancer cell line (A549 cell line). In under 120 min, the synthesized Ag-smx complex showed exceptional photo-degradation characteristics against methylene blue (MB) (10 ppm) in visible light radiation. Communicated by Ramaswamy H. Sarma

Cation-/Ligand-Induced Solvent-Assisted Transformations of Zn(II) and Cu(II) Complexes Featuring Single-Pocket Multidentate Chelating Members

A new family of single-pocket metal complexes bearing O,N,O-tridentate and O,N-bidentate chelating members {Cu, 1b (P21/n); Ni, 1c (C2/c); Mn, 1d (I2/a); Cu, 2b; and Ni, 2c (both P21/c)}, starting from synthesized and fully characterized Zn(II) (1a; I2/a) and Cu(II) (2a; C2) precursors, were conveniently prepared via cation-induced solvent-assisted and ligand-induced solvent-assisted transformations. Herein, we show multistep solvent-assisted transformations from cis-1a → trans-1b → cis-1c → cis-1d, as well as all-trans 2a → 2b → 2c. All processes are one-way irreversible, as substantiated by thermodynamic aspects (enthalpies based on Gibbs free energies) derived from density functional theory calculations. On the other hand, complex 2a′ (C2/c; a polymorphic form of 2a) was obtained through a routine synthetic procedure. The compounds have been established by various spectroscopic techniques (infrared, UV–vis, ESI-MS, 1H, and 13C NMR), elemental analysis, and X-ray crystallography. Single-crystal X-ray studies reveal that complexes 1a–d exhibit a pseudo-octahedral geometry around each metal center, with 2a displaying a four-coordinate seesaw geometry Cu(II) sphere (Addison parameter; τ = 0.42), while 2a′ (τ = 0.00), 2b (τ = 0.00), and 2c (τ = 0.00) possess a perfect square-planar configuration around each metal center. Furthermore, distortion is stabilized by the presence of peripheral O-donor atoms from the bulky −OMe group, and by virtue of its size, increased bond lengths and angles are accommodated. Ligand substitution induced coordination geometry transformation from quasi-square-planar 2a to perfect square-planar 2b. Assessment of the metric parameter shows that the distances between the two Cu–Omethoxy are all largely positive due to Jahn–Teller distortion, indicating an unprecedented tetragonal bipyramidal geometry in 1b.

Structural and Hirshfeld Surface Analysis of Thallium(I) and Indium(III) Complexes of a Soft Scorpionate Ligand

Two complexes containing a soft sulfur-substituted tris(pyrazolyl)hydroborate ligand, namely [TlI(TmtBu)]2∙2H2O and [InIII(TmtBu)2](InCl4), where TmtBu is the tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl)hydroborate anion, have been characterized. The {TlS}2 core of the former has the shape of a diamond. Each S atom of the TmtBu anion coordinates differently: one S is connected to one Tl atom, one bridges both Tl atoms, while the third S atom connects solely to the second Tl atom. The S4 donor set defines a seesaw geometry. The independent H2O molecule forms O–H···S and localized O–H···π(pyrazolyl) contacts. Flattened octahedral geometries defined by S6 donor sets are noted for the two independent cations in [InIII(TmtBu)2](InCl4). In the crystal of [TlI(TmtBu)]2∙2H2O, pyrazolyl-C–H···O(water) interactions connect the dimeric units into a linear supramolecular chain, chains pack without directional interactions between them. In the crystal of [InIII(TmtBu)2](InCl4), alternating rows of independent cations are interspersed by anions. The primary points of contact within a three-dimensional architecture are of the type In–Cl···π(pyrazolyl) and C–H···Cl. The assessment of the molecular packing was complemented by considering the calculated Hirshfeld surfaces and two-dimensional fingerprint plots (overall and delineated into individual contacts).

Evaluation of tin nitride (Sn3N4) via atomic layer deposition using novel volatile Sn precursors.

Novel Sn precursors, Sn(tbip)2, Sn(tbtp)2, and Sn(tbta)2, were synthesized and characterized using various analytical techniques and density functional theory calculations. These precursors contained cyclic amine ligands derived from iminopyrrolidine. X-ray crystallography revealed the formation of monomeric SnL2 with distorted seesaw geometry. Thermogravimetric analysis demonstrated the exceptional volatility of all complexes. Sn(tbtp)2 showed the lowest residual weight of 2.7% at 265 °C. Sn3N4 thin films were successfully synthesized using Sn(tbtp)2 as the Sn precursor and NH3 plasma. The precursor exhibited ideal characteristics for atomic layer deposition, with a saturated growth per cycle value of 1.9 Å cy-1 and no need for incubation when the film was deposited at 150-225 °C. The indirect optical bandgap of the Sn3N4 film was approximately 1-1.2 eV, as determined through ultraviolet-visible spectroscopy. Therefore, this study suggests that the Sn3N4 thin films prepared using the newly synthesized Sn precursor are suitable for application in thin-film photovoltaic devices.

Synthesis, structural characterization and evaluation of anticancer activity of polymeric silver(I) complexes based on niflumic acid/naproxen and picoline derivatives

Two polymeric mixed-ligand silver(I) complexes, [Ag(µ-nif)(4-pic)]n (1) and [Ag4(µ-nap)4(2-pic)2]n (2), where Hnif: niflumic acid, Hnap: naproxen, 4-pic: 4-picoline and 2-pic: 2-picoline, were synthesized and characterized by single-crystal X-ray diffraction, FT-IR and 1H NMR spectroscopies, elemental and thermal analysis techniques. In 1, nif ligand behaves as a µ3-N,O,O' bridge connecting three silver(I) ions and each silver(I) ion exhibits a seesaw geometry. In 2, nap ligands act as a µ-carboxylato-(O,O') bridge between two silver(I) ions and µ3-carboxylato-(O,O,O') bridge linking three silver(I) ions. Each silver(I) ion occurs in trigonal geometry. To uncover the anticancer properties of the complexes, first, their cytotoxic abilities were tested against three cancer cell lines, HT-29 (human colorectal adenocarcinoma), A-549 (human lung carcinoma), and MDA-MB-453 (human breast adenocarcinoma), and normal 3T3-L1 (mouse fibroblast) cell line by XTT tests. Afterwards, the anticancer mechanism of the complexes was tried to be elucidated through the flow cytometry analyzes. XTT assay results showed that the complexes exhibited the highest cytotoxic activity and selectivity on HT-29 cells among all the cell lines. Flow cytometry analyses revealed that both complexes induced the apoptosis through the mitochondrial membrane depolarization and activation of the caspase cascade in HT-29 cells.

Germanium Antimony Bonding in Ba4Ge2Sb2Te10 with Low Thermal Conductivity.

A new quaternary telluride, Ba4Ge2Sb2Te10, was synthesized at high temperature via the reaction of elements. A single-crystal X-ray diffraction study shows that the title compound crystallizes in its own structure type in the monoclinic P21/c space group having cell dimensions of a = 13.984(3) Å, b = 13.472(3) Å, c = 13.569(3) Å, and β = 90.16(3)° with four formula units per unit cell (Z = 4). The pseudo-one-dimensional crystal structure of Ba4Ge2Sb2Te10 consists of infinite 1∞[Ge2Sb2Te10]8- stripes, which are separated by Ba2+ cations. Each of the Ge(1) atoms is covalently bonded to four Te atoms, whereas the Ge(2) atom is covalently bonded with one Sb(2) and three Te atoms in a distorted tetrahedral geometry. The title compound is the first example of a chalcogenide that shows Ge-Sb bonding. The Sb(1) atom is present at the center of the seesaw geometry of four Te atoms. In contrast, the Sb(2) atom forms a seesaw geometry by coordinating with one Ge(2) and three Te atoms. Condensation of these Ge and Sb centered polyhedral units lead to the formation of 1∞[Ge2Sb2Te10]8- stripes. The temperature-dependent resistivity study suggests the semimetallic/degenerate semiconducting nature of polycrystalline Ba4Ge2Sb2Te10. The positive sign of Seebeck coefficient values indicates that the predominant charge carriers are holes in Ba4Ge2Sb2Te10. An extremely low lattice thermal conductivity of ∼0.34 W/mK at 773 K was observed for polycrystalline Ba4Ge2Sb2Te10, which is presumably due to the lattice anharmonicity induced by the stereochemically active 5s2 lone pair of Sb. The electronic structure of Ba4Ge2Sb2Te10 and the bonding of atom pairs in the structure have been analyzed by means of ELF analysis and crystal orbital Hamilton population (COHP) analysis.

Distorted Copper(II) Complex with Unusually Short CF···Cu Distances.

We find a Cu(II)-(L-CF3)2 complex (L-CF3 = 2,2,2-trifluoro-N-[2-(pyridin-2-yl)propan-2-yl]acetamide) with a distorted "seesaw" geometry. It has the shortest crystallographic CF···Cu distances yet reported, to the best of our knowledge (<2.6 Å), for which computational and experimental data indicate a secondary bonding interaction. A comparison with a CCl3 version and one without ligand backbone gem-dimethyl groups suggests a steric origin for the distorted geometry, resulting from the specific ligand interactions.

Synthesis and structures of a family of hybrid donor N2P2 beta-diketiminate zinc complexes

Monoanionic mixed N2P2 donor beta-diketiminate (BDI) ligands with phosphine pendant arms, 2-(4-tolyl)-bis(2-diisopropylphosphinophenyl)propenediimine (abbreviated as Tol-BDI(DIPPP)2H), were prepared and metallated with zinc(II) iodide. Three ligand variations have been synthesized by incorporating different substituents (methyl or methoxy) on the linker phenyl rings at positions 4 and 6. In the 4-methyl zinc complex [Tol-BDI(DIPPMeP)2ZnI] and 4-methoxy zinc complex [Tol-BDI(DIPPMeOP)2ZnI], the metal is bound to all four donors on the ligand, rendering a distorted square pyramidal geometry around the zinc metal with τ5 values of 0.25 and 0.29, respectively. However, the crystal structure of the 4,6-dimethyl zinc complex [Tol-BDI(DIPPMe2P)2ZnI] shows a four-coordinate zinc with only one phosphine bound to the metal, resulting in a distorted seesaw geometry around the metal. While X-ray crystallography shows no interactions between the metal center and the unbound phosphine, solution characterization reveals a symmetrical complex with both phosphines bound to the metal center in all three zinc complexes.

Synthesis, crystal structure and in vitro anticancer studies of bis(dibenzyldithiocarbamato)Zn(II)

Bis(dibenzyldithiocarbamato)Zn(II), [Zn(dbzdtc)2], was synthesized and characterized by spectroscopic techniques, elemental analysis and single crystal X-ray crystallography. The compound is crystallized in a monoclinic space group P21/n with Zn(II) located on crystallographic twofold symmetry and coordinated to two molecules of dibenzyl dithiocarbamato anions to form a rare four-coordinate mononuclear Zn(II) complex in a see-saw geometry. The cytotoxicity of the complex was evaluated by MTT assay against breast cancer cells (MCF-7) and human embryonic kidney cells (HEK293). The results showed that the complex is active against MCF-7 breast cancer cells with IC50 value of 6.41 and 4.423 μΜ against HEK293 cell line.

Hydrothermal synthesis, crystal structures, and X-ray photoelectron spectroscopy of lead tellurium(IV) and tellurium(VI) oxycompounds: Ba3PbTe6O16 and Na2Pb9(μ6-O)2(Te2O10)2.

An exploratory study of the lead-tellurium-oxygen phase space led to two new compounds, Ba3PbTe6O16 (BPTO) and Na2Pb9(μ6-O)2(Te2O10)2 (NPTO), which were synthesized under hydrothermal conditions at 550 °C and 210 °C, respectively, and characterized by single-crystal X-ray diffraction, infrared and X-ray photoelectron spectroscopy. BPTO adopts a layer structure. The Te4+ cation in BPTO is bonded to four oxygen atoms at about 2.0 Å with two more oxygens at about 3.0 Å. The seesaw-shaped TeO4 units share corners to form 2D layers containing six-membered rings and the Ba2+ and Pb2+ cations are situated in the interlayer region. The structure of NPTO contains dimers of edge-sharing Te6+O6 octahedra, which are connected through five-coordinate Pb2+ cations. A unique six-coordinate O atom is at the center of the octahedron formed by five Pb2+ and one Na+ cations. BPTO is one of the few metal tellurites which were synthesized under supercritical hydrothermal reaction conditions. The Pb2+ cation in NPTO shows pronounced stereochemical effects of the lone electron pair. In contrast, BPTO shows no stereochemical evidence of the inert pair.

Super bulky Bismuth(III) imidazole selones

Treatment of BiBr3 with super bulky [(IPaul)Se] (L1) ([(IPaul)Se] = 1,3-bis(2,4-methyl-6-diphenyl phenyl)imidazole selone) or IPr*Se (L2) (IPr*Se = 1,3-bis(2,6-diphenylmethylphenyl)imidazole selone) in toluene afforded the dinuclear complex [(L1)BiBr2(µ-Br)]2 (1) and mononuclear complex [(L2)BiBr3] (2), whose structures have been determined by an X-ray crystallographic study. The complexes were characterized by a combination of 1H NMR and 13C{1H} NMR spectroscopy. The thermal stability of 1 and 2 was compared using TGA. The steric controlled super bulky ligand systems allow for the first structural isolation of a novel super bulky dinuclear complex 1 with edge shared octahedral geometry and mononuclear super bulky complex 2 with mono capped seesaw geometry. The sterically more crowded complex 2 showed the long Bi-Se bond distance (3.192(3) Å) compared to 1 (2.902(5) Å).

Structural and spectroscopic characterization of an Fe(VI) bis(imido) complex.

High-valent iron species are key intermediates in oxidative biological processes, but hexavalent complexes apart from the ferrate ion are exceedingly rare. Here, we report the synthesis and structural and spectroscopic characterization of a stable Fe(VI) complex (3) prepared by facile one-electron oxidation of an Fe(V) bis(imido) (2). Single-crystal x-ray diffraction of 2 and 3 revealed four-coordinate Fe centers with an unusual "seesaw" geometry. 57Fe Mössbauer, x-ray photoelectron, x-ray absorption, and electron-nuclear double resonance (ENDOR) spectroscopies, supported by electronic structure calculations, support a low-spin (S = 1/2) d3 Fe(V) configuration in 2 and a diamagnetic (S = 0) d2 Fe(VI) configuration in 3 Their shared seesaw geometry is electronically dictated by a balance of Fe-imido σ- and π-bonding interactions.