An Inorganic Double Helix: Hydrothermal Synthesis, Structure, and Magnetism of Chiral [(CH3)2NH2]K4[V10O10(H2O)2(OH)4(PO4)7]{middle dot}4H2O

Very complicated inorganic solids can be self-assembled from structurally simple precursors as illustrated by the hydrothermal synthesis of the vanadium phosphate, [(CH(3))(2)NH(2)]K(4)[V(10)O(10)(H(2)O)(2)(OH)(4)(PO(4))(7)].4H(2)O, 1, which contains chiral double helices formed from interpenetrating spirals of vanadium oxo pentamers bonded together by P(5+). These double helices are in turn intertwined with each other in a manner that generates unusual tunnels and cavities that are filled with (CH(3))(2)NH(2)(+) and K(+) cations, respectively. The unit cell contents of dark blue phosphate 1, which crystallizes in the enantiomorphic space group P4(3) with lattice constants a = 12.130 and c = 30.555 angstroms, are chiral; only one enantiomorph is present in a given crystal. Magnetization measurements show that 1 is paramagnetic with ten unpaired electrons per formula unit at higher temperatures and that antiferromagnetic interactions develop at lower temperatures.     

Conducting Layered Organic-inorganic Halides Containing <110>-Oriented Perovskite Sheets

Single crystals of the layered organic-inorganic perovskites, [NH(2)C(I=NH(2)](2)(CH(3)NH(3))m SnmI3m+2, were prepared by an aqueous solution growth technique. In contrast to the recently discovered family, (C(4)H(9)NH(3))(2)(CH(3)NH(3))n-1SnnI3n+1, which consists of (100)-terminated perovskite layers, structure determination reveals an unusual structural class with sets of m <110>-oriented CH(3)NH(3)SnI(3) perovskite sheets separated by iodoformamidinium cations. Whereas the m = 2 compound is semiconducting with a band gap of 0.33 +/- 0.05 electron volt, increasing m leads to more metallic character. The ability to control perovskite sheet orientation through the choice of organic cation demonstrates the flexibility provided by organic-inorganic perovskites and adds an important handle for tailoring and understanding lower dimensional transport in layered perovskites.     

Free energy and temperature dependence of electron transfer at the metal-electrolyte interface

The rate constant of the electron-transfer reaction between a gold electrode and an electroactive ferrocene group has been measured at a structurally well-defined metal-electrolyte interface at temperatures from 1 degrees to 47 degrees C and reaction free energies from -1.0 to +0.8 electron volts (eV). The ferrocene group was positioned a fixed distance from the gold surface by the self-assembly of a mixed thiol monolayer of (eta(5)C(5)H(5))Fe(eta(5)C(5)H(4))CO(2)(CH(2))(16)SH and CH(3)(CH(2))(15)SH. Rate constants from 1 per second (s(-1)) to 2 x 10(4) s(-1) in 1 molar HClO(4) are reasonably fit with a reorganization energy of 0.85 eV and a prefactor for electron tunneling of 7 x 10(4) s(-1) eV(-1). Such self-assembled monolayers can be used to systematically probe the dependence of electron-transfer rates on distance, medium, and spacer structure, and to provide an empirical basis for the construction of interfacial devices such as sensors and transducers that utilize macroscopically directional electron-transfer reactions.     

Nitric oxide reduction coupled with carbon monoxide oxidation in the presence of soluble metal catalysts

Solutions of RhCl(3).xH(2)O in ethanol and Ru(NO)(2)[P(C(6)H(5))(3)](2) in benzene catalyze the reduction of nitric oxide to nitrous oxide concomitant with the oxidation of carbon monoxide to carbon dioxide at ambient temperature and atmospheric pressure. The reaction, which is followed by gas chromatography and by the decrease in pressure of the system, proceeds to 47 percent conversion of the reactants after 63 hours.     

Dinitrogen Cleavage by a Three-Coordinate Molybdenum(III) Complex

Cleavage of the relatively inert dinitrogen (N(2)) molecule, with its extremely strong N identical withN triple bond, has represented a major challenge to the development of N(2) chemistry. This report describes the reductive cleavage of N(2) to two nitrido (N(3-)) ligands in its reaction with Mo(NRAr)(3), where R is C(CD(3))(2)CH(3) and Ar is 3,5-C(6)H(3)(CH(3))(2'), a synthetic three-coordinate molybdenum(III) complex of known structure. The formation of an intermediate complex was observed spectroscopically, and its conversion (with N identical withN bond cleavage) to the nitrido molybdenum(VI) product N identical withMo(NRAr)(3) followed first-order kinetics at 30 degrees C. It is proposed that the cleavage reaction proceeds by way of an intermediate complex in which N(2) bridges two molybdenum centers.     

Structure of a three-dimensional, microporous molybdenum phosphate with large cavities

The synthesis, single-crystal x-ray structural characterization, and sorption properties of a microporous molybdenum phosphate, (Me(4)N)(1.3)(H(3)O)(0.7)[Mo(4)O(8)(PO(4))(2)] . 2H(2)O (Me, methyl), are presented. The three-dimensional framework is built up from Mo(4)O(8)(4+) cubes and PO(4)(3-) tetrahedra that are connected in such a way that large, cation-filled voids are generated; these voids constitute 25% of the volume of the solid. Absorption isotherms for water show the completely reversible uptake of 4 to 5 percent by weight water into the micropores of this compound, which corresponds to 10 to 12 percent by volume.     

Open Framework Structures Based on Sex2- Fragments: Synthesis of (Ph4P)[M(Se6)2] (M = Ga, In, TI) in Molten (Ph4P)2Sex

Polychalcogenide compounds with open polymeric frameworks are rare, and they represent a class of compounds in which microporosity might be achieved. Microporous frameworks that are not oxide-based are now attracting interest because of the combination of catalytic and electronic properties they may simultaneously possess. Three new compounds that may be forerunners to such materials have been discovered and are reported here. The reaction of gallium (Ga), indium (In), and thallium (TI) metal with (Ph(4)P)(2)Se(5) (Ph, phenyl) and an excess of elemental selenium (Se) in a sealed, evacuated Pyrex tube at 200 degrees C yielded small red crystals of (Ph(4)P)[Ga(Se(6))(2)] (I), (Ph(4)P)[In(Se(6))(2)] (II), and (Ph(4)P)[TI(Se(6))(2)] (III), respectively. The [M(Se(6))(2)](-) (M = Ga, In, TI) ions form a two-dimensional, open framework filled with Ph(4)P(+) ions. The [M(Se(6))(2)](n)(n-) structure consists of tetrahedral M(3+) centers and bridging Se(6)(2-) ligands, leading to an extended structure in two dimensions. These layers stack perfectly one on top of the other giving rise to one-dimensional channels running down the c axis that are filled with Ph(4)P(+) cations. These cations are situated in the layers, as opposed to between the layers, and the whole structure can be viewed as a template. Compound II shows remarkable thermal stability and melts congruently at 242 degrees C. Upon cooling to room temperature it gives a glassy phase that recrystallizes upon subsequent heating to 160 degrees C.     

MAP沉淀法回收垃圾渗滤液中高浓度氨氮试验研究

以实际垃圾渗滤液为对象,采用MgSO4.7H2O和Na2HPO4.12H2O使NH3-N生成MgNH4PO4.6H2O结晶沉淀的MAP(硫酸铵镁)法去除回收垃圾渗滤液中高浓度氨氮的效能,研究了pH、反应时间、药剂配比对NH3-N去除率的影响。结果表明:MAP法回收垃圾渗滤液中NH3-N的适宜pH为8.5~9.5;过高的pH会破坏硫酸铵镁晶体结构,导致固定氨从结晶中游离,不利于氨氮的去除;在pH为8.5、反应时间为20 min、n(Mg2+)∶n(NH4+)∶n(PO43-)=1.4∶1.0∶1.4的最佳条件下,渗滤液中NH3-N的质量浓度由初始的1 671 mg/L降至30 mg/L,去除率达98.2%;同时回收的MAP可作缓释肥。     

Dianion Stabilization by (M(C5(CH3)5)2)+: Theoretical Evidence for a Localized Ring in (DDQ)2-

Organic dianions have been stabilized by (M(C(5)(CH(3))(5))(2))(+), where M is iron or cobalt. This has allowed the structural and spectroscopic characterization of these dianions. The structure of (M(C(5)(CH(3))(5))(2))(2)(+) (DDQ)(2-), where DDQ is 2,3-dichloro-5,6-dicyanobenzoquinone, has been determined by x-ray crystallography. The structure of (DDQ)(2-)is consistent with ab initio molecular orbital calculations that suggest a localizd as opposed to a delocalized (aromatic) ring structure.     

Synthesis, structure, and reactivity of an iron(V) nitride

Despite being implicated as important intermediates, iron(V) compounds have proven very challenging to isolate and characterize. Here, we report the preparation of the iron(V) nitrido complex, [PhB((t)BuIm)(3)Fe(V)≡N]BAr(F24) (PhB((t)BuIm)(3)(-) = phenyltris(3-tert-butylimidazol-2-ylidene)borato, BAr(F24) = B(3,5-(CF(3))(2)C(6)H(3))(4)(-)), by one electron oxidation of the iron(IV) nitrido precursor. Single-crystal x-ray diffraction of the iron(V) complex reveals a four-coordinate metal ion with a terminal nitrido ligand. M??bauer and electron paramagnetic resonance spectroscopic characterization, supported by electronic structure calculations, provide evidence for a d(3) iron(V) metal center in a low spin (S = 1/2) electron configuration. Low-temperature reaction of the iron(V) nitrido complex with water under reducing conditions leads to high yields of ammonia with concomitant formation of an iron(II) species.     

Ammonioborite: new borate polyion and its structure

The mineral ammonioborite is monoclinic with unit cell dimensions (in angstroms): a = 25.27, b = 9.65, and c = 11.56; beta = 94 degrees 17', and the space group is C 2/c. Analysis of the crystal structure revealed the crystallo-chemical formula (NH(4))(3)B(15)O(20)(OH)(8).4H(2)O, with four such formula units in the unit cell. The basic structural unit is the double ring consisting of one BO(4) tetrahedron and four BO(3) triangles: in ammonioborite three of these units are connected to give trimeric ions [B(15)O(20)(OH)(8)](3-).     

Shattuckite and plancheite: a crystal chemical study

The orthorhombic crystal structures of shattuckite, Cu(5)( SiO(3))(4)(OH)(2) and planchétite, Cu(8)(Si(4)0(11))(2)(OH)(4) H(2)O, have been solved. Shattuckite contains silicate chains similar to pyroxene in a complex association with copper atoms, while the closely related planchéite contains silicate chains similar to amphibole.     

Stanfieldite: a new phosphate mineral from stony-iron meteorites

A new mineral, stanfieldite, Ca(4)(Mg,Fe)(5)(PO(4))(6), has been found in the Estherville mesosiderite and several pallasites: Santa Rosalia, Albin, Finmarken, Imilac, Mount Vernon, and Newport. The atom ratio Mg:Fe of this mineral varies from 1.5 in Estherville to a constant ratio of about 15 in the pallasites. X-ray, optical, and chemical data for the mineral resemble those for the only intermediate compound in the system Mg(3)(PO(4))(2)-Ca(3)(PO(4))(2).     

Synthesis and structure of a terminal uranium nitride complex

The terminal uranium nitride linkage is a fundamental target in the study of f-orbital participation in metal-ligand multiple bonding but has previously eluded characterization in an isolable molecule. Here, we report the preparation of the terminal uranium(V) nitride complex [UN(Tren(TIPS))][Na(12-crown-4)(2)] {in which Tren(TIPS) = [N(CH(2)CH(2)NSiPr(i)(3))(3)](3-) and Pr(i) = CH(CH(3))(2)} by reaction of the uranium(III) complex [U(Tren(TIPS))] with sodium azide followed by abstraction and encapsulation of the sodium cation by the polydentate crown ether 12-crown-4. Single-crystal x-ray diffraction reveals a uranium-terminal nitride bond length of 1.825(15) angstroms (where 15 is the standard uncertainty). The structural assignment is supported by means of (15)N-isotopic labeling, electronic absorption spectroscopy, magnetometry, electronic structure calculations, elemental analyses, and liberation of ammonia after treatment with water.     

Structural aspects of reversible molecular oxygen uptake

The system IrX(CO)[P(C(6)H(5))(3)](2) in benzene solution adds mo lecular oxygen reversibly if X is chlorine and irreversibly if X is iodine. The crystal structure of the complex IrIO(2)(CO)[P(C(6)H(5))(3)](2) * CH(2)Cl(2) is reported here and compared with a previous study of the structure of IrClO(2)(CO)[P(C(6)H(5))(3)](2). The O-O bond length is 1.47 +/- 0.02 angstroms in the irreversibly oxygenated iodo-compound and 1.30 +/- 0.03 angstroms in the reversibly oxygenated chloro compound.     

A mercury-catalyzed, high-yield system for the oxidation of methane to methanol

A homogeneous system for the selective, catalytic oxidation of methane to methanol via methyl bisulfate is reported. The net reaction catalyzed by mercuric ions, Hg(II), is the oxidation of methane by concentrated sulfuric acid to produce methyl bisulfate, water, and sulfur dioxide. The reaction is efficient. At a methane conversion of 50 percent, 85 percent selectivity to methyl bisulfate ( approximately 43 percent yield; the major side product is carbon dioxide) was achieved at a molar productivity of 10(-7) mole per cubic centimeter per second and Hg(II) turnover frequency of 10(-3) per second. Separate hydrolysis of methyl bisulfate and reoxidation of the sulfur dioxide with air provides a potentially practical scheme for the oxidation of methane to methanol with molecular oxygen. The primary steps of the Hg(II)-catalyzed reaction were individually examined and the essential elements of the mechanism were identified. The Hg(II) ion reacts with methane by an electrophilic displacement mechanism to produce an observable species, CH(3)HgOSO(3)H, 1. Under the reaction conditions, 1 readily decomposes to CH(3)OSO(3)H and the reduced mercurous species, Hg(2)(2+) The catalytic cycle is completed by the reoxidation of Hg(2)(2+) with H(2)SO(4) to regenerate Hg(II) and byproducts SO(2) and H(2)O. Thallium(III), palladium(II), and the cations of platinum and gold also oxidize methane to methyl bisulfate in sulfuric acid.     

Synthesis of RNA-polyadenylic acid by isolated brain nuclei

Nuclei, isolated from mouse brain tissue at various stages of postnatal development and incubated under cell-free conditions, synthesized RNA molecules that were associated with polyadenylic acid [poly(A)]. The RNA synthesized by these nuclei was similar to the poly(A)-associated products described for intact eukaryotic cells. The brain nuclei synthesized a similar proportion of RNA-poly(A) in the presence either of Mg(2+) or of Mn(2+) with (NH(4))(2)So(4). The RNA from neonatal brain nuclei appeared to have a greater proportion of poly(A)-containing RNA than nuclear products obtained from more mature neural tissue.     

Inorganic liquid photovoltaic cell: tetravalent molybdenum in water

An inorganic liquid photovoltaic cell is described. The cell is based on the reaction 2Mo(4+) <--> Mo(5+) + Mo(3+), with pentavalent molybdenum formed in the illuminated half-cell and trivalent molybdenum formed in the dark half-cell. In the photochemical reaction pentavalent molybdenum precipitates. Consequently, the cell has the capability of storing energy.     

A synthetic nickel electrocatalyst with a turnover frequency above 100,000 s⁻¹ for H₂ production

Reduction of acids to molecular hydrogen as a means of storing energy is catalyzed by platinum, but its low abundance and high cost are problematic. Precisely controlled delivery of protons is critical in hydrogenase enzymes in nature that catalyze hydrogen (H(2)) production using earth-abundant metals (iron and nickel). Here, we report that a synthetic nickel complex, [Ni(P(Ph)(2)N(Ph))(2)](BF(4))(2), (P(Ph)(2)N(Ph) = 1,3,6-triphenyl-1-aza-3,6-diphosphacycloheptane), catalyzes the production of H(2) using protonated dimethylformamide as the proton source, with turnover frequencies of 33,000 per second (s(-1)) in dry acetonitrile and 106,000 s(-1) in the presence of 1.2 M of water, at a potential of -1.13 volt (versus the ferrocenium/ferrocene couple). The mechanistic implications of these remarkably fast catalysts point to a key role of pendant amines that function as proton relays.     

Lanthanide complexes as nuclear magnetic resonance structural probes: paramagnetic anisotropy of shift reagent adducts

Magnetic anisotropy measurements on single crystals of a series of paramagnetic 8-coordinate lanthanide shift reagent adducts of the type Ln[(CH(3))(3)CCOCHCOC(CH(3))(3)(4-CH(3)C(5)H(1)N)(2) have been made for the following lanthanides: praseodymium, neodymium, samarium, europium, terbium, dysprosium, holmium, erbium, thulium, and ytterbium. The susceptibility tensors are highly anisotropic and nonaxial. Dipolar nuclear magnetic resonance shifts evaluated from the solid-state date are in satisfactory agreement with the solution results.