Chemical Stabilization and Electrochemical Destabilization of the Iron Keggin Ion in Water.

The iron Keggin ion is identified as a structural building block in both magnetite and ferrihydrite, two important iron oxide phases in nature and in technology. Discrete molecular forms of the iron Keggin ion that can be both manipulated in water and chemically converted to the related metal oxides are important for understanding growth mechanisms, in particular, nonclassical nucleation in which cluster building units are preserved in the aggregation and condensation processes. Here we describe two iron Keggin ion structures, formulated as [BiFeOFeO(OH)(CFCOO)(HO)] (Kegg-1) and [BiFeOFeO(OH)(CFCOO)] (Kegg-2).

High surface area and Z' in a thermally stable 8-fold polycatenated hydrogen-bonded framework.

1,3,5-Tris(4-carboxyphenyl)benzene assembles into an intricate 8-fold polycatenated assembly of (6,3) hexagonal nets formed through hydrogen bonds and π-stacking. One polymorph features 56 independent molecules in the asymmetric unit, the largest Z' reported to date. The framework is permanently porous, with a BET surface area of 1095 m(2) g(-1) and readily adsorbs N2, H2 and CO2.

3-(1,3-Di-phenyl-propan-2-yl)-4-methyl-6-phenyl-isoxazolo[3,4-d]pyridazin-7(6H)-one.

In the title compound, C27H23N3O2, the geminal benzyl groups branching out from the methine adjacent to the isoxazole group are both syn-oriented to the methyl group of the pyridazinone moiety, as reflected by C-C distances of 3.812 (2) and 4.369 (2) Å between the methyl carbon and the nearest ring carbon of each benzyl group.

Semiquinone-bridged bisdithiazolyl radicals as neutral radical conductors.

Semiquinone-bridged bisdithiazolyls 3 represent a new class of resonance-stabilized neutral radical for use in the design of single-component conductive materials. As such, they display electrochemical cell potentials lower than those of related pyridine-bridged bisdithiazolyls, a finding which heralds a reduced on-site Coulomb repulsion U. Crystallographic characterization of the chloro-substituted derivative 3a and its acetonitrile solvate 3a·MeCN, both of which crystallize in the polar orthorhombic space group Pna2(1), revealed the importance of intermolecular oxygen-to-sulfur (CO···SN) interactions in generating rigid, tightly packed radical π-stacks, including the structural motif found for 3a·MeCN in which radicals in neighboring π-stacks are locked into slipped-ribbon-like arrays.

Ferrocene-based trimethylsilyl chalcogenide reagents for the assembly of functionalized metal-chalcogen architectures.

The ferrocene-based trimethylsilyl chalcogenide reagents [FcC(O)OCH(2)CH(2)ESiMe(3)] (2, E=S, 3 E=Se, Fc=[Fe(η(5)-C(5)H(5))(η(5)-C(5)H(4))]) and [FcC(O)NHCH(2)CH(2) SSiMe(3)] (8b) have been synthesized. The reagents were reacted with solubilized transition-metal acetates to yield functionalized complexes and clusters, including the spherical nanocluster [Ag(14)S{SCH(2)CH(2)O(O)CFc)}(12)(PPh(3))(6)] (11, PPh(3) =triphenylphosphine). The complexes were characterized by NMR spectroscopy and X-ray crystallography.

Series of comparable dinuclear group 4 neo-pentoxide precursors for production of pH dependent group 4 nanoceramic morphologies.

A series of similarly structured Group 4 alkoxides was used to explore the cation effect on the final ceramic nanomaterials generated under different pH solvothermal (SOLVO) conditions. The synthesis of [Ti(μ-ONep)(ONep)(3)](2) (1, ONep = OCH(2)C(CH(3))(3)) and {[H][(μ-ONep)(3)M(2)(ONep)(5)(OBu(t))]} where M = Zr (2) and Hf (3, OBu(t) = OC(CH(3))(3)) were realized from the reaction of M(OBu(t))(4) (M = Ti, Zr, Hf) and H-ONep. Crystallization of 1 from py led to the isolation of [Ti(μ-ONep)(ONep)(3)](2)(μ-py) (1a) whereas the dissolution of 2 or 3 in py yielded {(μ(3)-O)(μ(3)-OBu(t))[(μ-ONep)M(ONep)(2)](3)} M = Zr (2a) and Hf (3a).

Self-assembly of alkali-uranyl-peroxide clusters.

The hexavalent uranium specie, uranyl triperoxide, UO(2)(O(2))(3)(4-), has been shown recently to behave like high oxidation-state d(0) transition-metals, self-assembling into polyoxometalate-like clusters that contain up to 60 uranyl cations bridged by peroxide ligands. There has been much less focus on synthesis and structural characterization of salts of the monomeric UO(2)(O(2))(3)(4-) building block of these clusters. However, these could serve as water-soluble uranyl precursors for both clusters and materials, and also be used as simple models to study aqueous behavior by experiment and modeling.

Comparisons of Pu(IV) and Ce(IV) diphosphonates.

The hydrothermal reaction of PuO(2) with CH(2)(PO(3)H(2))(2) results in the formation of alpha-Pu[CH(2)(PO(3))(2)](H(2)O), beta-Pu[CH(2)(PO(3))(2)](H(2)O) (1), gamma-Pu[CH(2)(PO(3))(2)](H(2)O) (2), and Pu[CH(2)(PO(3))(2)](H(2)O).H(2)O (3) as crystalline compounds with blue, green, red, and very pale peach coloration, respectively. In all cases single crystal X-ray diffraction studies reveals Pu(4+) coordinated by [CH(2)(PO(3))(2)](4-) and water to yield PuO(7) units.

Homo- and heterometallic complexes of tetra-(di-substituted hydroxybenzyl)-N,N'-ethylenediamine derivatives.

The coordination behavior of a series of group 4 metal alkoxides [M(OR)(4)] modified by a set of novel substituted hydroxybenzyl ethylene diamine (H(4)-ED-L(4)) ligands {[tetra(3,5-di-t-butyl-2-hydroxybenzyl)-N,N'-ethylenediamine] termed H(4)-ED-DBP(4) (1), [tetra(3,5-di-t-amyl-2-hydroxybenzyl)-N,N'-ethylenediamine] termed H(4)-ED-DAP(4) (1a), and [tetra(3,5-dichloro-2-hydroxybenzyl)-N,N'-ethylenediamine] termed H(4)-ED-DCP(4) (2)} was elucidated. The reaction of 1 or 1a with the M(OR)(4) precursor led to the isolation of the structural similar species M(ED-L(4)) where L = DBP, M = Ti (3), Zr (4), Hf (5); L = DAP, M = Zr (4a), Hf (5a). In contrast, the reaction of 2 with the M(OR)(4) precursors yielded Ti(ED-DCP(4)) (6), (py)(2)Zr(ED-DCP(4)) (7), and (HOBu(t))Hf(ED-DCP(4)) (8) where py = pyridine and HOBu(t) = HOC(CH(3))(3).

Antimony oxide hydroxide ethanedisulfonate: a cationic layered metal oxide for Lewis acid applications.

We have discovered a rare example of a cationically charged inorganic material. The layered structure is an example outside the extensively studied isostructural set of anionic clays/layered double hydroxides and our previously reported lead fluoride nitrate. For the present compound, the antimony oxide hydroxide layers are positively charged and are templated by anionic alkylenedisulfonate.

Toluene-sandwiched trinuclear copper(I) and silver(I) triazolates and phosphine adducts of dinuclear copper(I) and silver(I) triazolates.

Cu (I) and Ag (I) complexes of the fluorinated triazolate ligand [3,5-(C3F7)2Tz](-) have been synthesized using the corresponding metal(I) oxides and the triazole. They form pi-acid/base adducts with toluene, leading to [Tol][M3][Tol] ([Tol]=toluene; [M3]={[3,5-(C3F7)2Tz]Cu}3 or {[3,5-(C3F7)2Tz]Ag}3) type structures. Packing diagrams show the presence of extended chains of the type {[Tol][M3][Tol]}infinity, but the intertoluene ring distances are too long for significant pi-arene/pi-arene contacts.

A unique heterobimetallic benzyl calciate--an organometallic mixed-metal species involving a heavy alkaline-earth metal.

A co-complexation reaction utilizing homometallic benzylcalcium and benzyllithium affords a rare example of a heterobimetallic benzyl calciate.

Pseudotetrahedral polyhalocubanes: synthesis, structures, and parity violating energy differences.

All possible pseudotetrahedral, stable polyhalocubanes were prepared, and their structures were proven by NMR spectroscopy and X-ray crystallography. Parity violating energy differences (DeltaEpv) and vibrational frequency shifts were computed. The DeltaEpv values are predicted to be one to two orders of magnitude smaller than those for the corresponding polyhalomethanes.

Synthesis, structural and spectroscopic characterization, catalytic properties, and thermal transformations of new cyclic di- and trisiloxanediolato tantalum complexes.

The reaction between Ta(OEt)5 and 1,1,3,3-tetramethyl-1,3-disiloxanediol, (HOSiMe2OSiMe2OH), leads to new siloxy complexes in which the dimeric nature of Ta(OEt)5 is maintained with both bridging ethoxide and disiloxanediolato bridges. With equal amounts of the reagents, two terminal OEt groups are replaced to form [Ta(OEt)2]2(mu-OEt)2(mu-OSiMe2OSiMe2O)2, 1, whereas with an excess of diol, the remaining terminal OEt groups are also replaced but with a trisiloxanediolato unit to form [Ta(OSiMe2OSiMe2OSiMe2O)]2(mu-OEt)2(mu-OSiMe2OSiMe2O)2, 2. Complexes 1 and 2 catalyze the transformation of HOSiMe2OSiMe2OH to polysiloxanes.

A chiral, heterometallic metal-organic framework derived from a tris(chelate) coordination complex.

A novel tris(chelate) metalloligand has been used to synthesize a chiral, heterometallic metal-organic framework that is robust to solvent removal and shows selective uptake of nitroaromatic compounds.

Synthesis and structural characterization of carborane-containing neutral, self-assembled Pt-metallacycles.

[structure: see text] We have combined carborane chemistry with the newly developed directional bonding strategy to synthesize neutral macrocycles. The m- and p-carborane dicarboxylates were utilized as the donor linkers in conjunction with 1,8-bis[trans-Pt(PEt3)2NO3]anthracene 3, 2,9-bis[trans-Pt(PEt3)2NO3]phenanthrene 5, and cis-Pt(PEt3)2(NO3)2 unit 6. Three new platinum-based macrocycles, 4, 7, and 8, were thus synthesized.

A non-natural dinucleotide containing an isomeric L-related deoxynucleoside: dinucleotide inhibitors of anti-HIV integrase activity.

The first X-ray crystal structure of a non-natural dinucleotide, 5'-O-phosphoryl-1'-deoxy-2'-isoadenylyl-(3' --> 5')-cytidine 6.5-hydrate (pIsodApC), C19H26N8O13P2 x 6.5H2O, belonging to a family of dinucleotides that contain an isomeric nucleoside component, is described.

Form III of 2,2',4,4',6,6'-hexanitroazobenzene (HNAB-III).

The crystal structure of form III of the title compound, HNAB [systematic name: bis(2,4,6-trinitrophenyl)diazene], C12H4N8O12, has finally been solved as a pseudo-merohedral twin (monoclinic space group P2(1), rather than the orthorhombic space group C222(1) suggested by diffraction symmetry) using a dual space recycling method. The significant differences in the room-temperature densities of the three crystalline forms allow examination of molecular differences due to packing arrangements. An interesting relationship with the stilbene analog, HNS, is discussed.

Electrochemical, spectroscopic, and structural evidence for the mild hydrolysis of tetracyanoethylene, TCNE, to form the 2,3,3-tricyanoacrylamidate ligand: isolation of an unexpected quadruply-bonded polymeric material [Mo2(O2CCMe3)3((NC)2CC(CN)CONH)]infinity.

Under strictly anhydrous conditions, no reaction occurs between Mo(2)(O(2)CCMe(3))(4) and tetracyanoethylene, TCNE, at room temperature, but after addition of 1 equiv of water, a reaction proceeds to form [Mo(2)(O(2)CCMe(3))(3)((NC)(2)CC(CN)CONH)], 1. The compound contains a quadruple-bonded Mo(2) unit and the 2,3,3-tricyanoacrylamidate anion as a ligand (TC3A), a very unusual hydrolyzed form of TCNE. Two different solid-state structures were obtained after crystallization of 1.

A synthetic strategy for the preparation of cyclic peptide mimetics based on SET-promoted photocyclization processes.

A novel method for the synthesis of cyclic peptide analogues has been developed. The general approach relies on the use of SET-promoted photocyclization reactions of peptides that contain N-terminal phthalimides as light absorbing electron acceptor moieties and C-terminal alpha-amidosilane or alpha-amidocarboxylate centers. Prototypical substrates are prepared by coupling preformed peptides with the acid chloride of N-phthalimidoglycine.

Pseudotetrahedral polyhaloadamantanes as chirality probes: synthesis, separation, and absolute configuration.

Pseudotetrahedral, conformationally as well as configurationally stable 1-bromo-3-chloro-5-fluoro- (4) and 1-bromo-3-chloro-5-fluoro-7-iodoadamantane (5) (and some related compounds) were prepared by our recently devised phase-transfer catalytic halogenation protocol; the optical antipodes of 4 were separated by HPLC on chiral phase in ee > 99%, and the absolute configurations were assigned by matching observed and computed circular dichroism spectra. Structure 5 is the first chiral aliphatic hydrocarbon containing all stable (nonradioactive) halogens; its structure was proven by NMR spectroscopy and by X-ray crystal data. We emphasize that the combination of experiment and theory is very powerful in assigning absolute configurations even for molecules without typical chromophors, with small values for the optical rotation, and without an atom at the stereogenic center.

Using NIST Crystal Data Within Siemens Software for Four-Circle and SMART CCD Diffractometers.

NIST Crystal Data developed at The National Institute for Standards and Technology has been incorporated with Siemens single crystal software for data collection on four-circle and two-dimensional CCD diffractometers. Why this database is useful in the process of single crystal structure determination, and how the database is searched, are described. Ideas for future access to this and other databases are presented.