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New borosulfates were obtained by reaction of B2O3 in oleum or concentrated H2SO4 at temperatures between 300 and 360 °C. They are the first examples of borosulfates with directly connected boron polyhedra, that is, ditetrahedral B2O7 or layers of trigonal-planar BO3 units. Cs2B2S3O13 [P21/c, Z = 4, a = 14.765(3), b = 6.710(1), c = 12.528(3) A, β = 104.60(3)°] contains layers of corner-sharing BO4 and SO4 tetrahedra. The BO4 tetrahedra form dimers. SO4 tetrahedra connect four B2O7 dimers to rings containing 10 tetrahedra, which are condensed to a layer. A third SO4 tetrahedron connects two BO4 tetrahedra of the B2O7 unit. The layers are stacked in the [100] direction. One Cs+ cation is located within the layer of tetrahedra, the second one between the layers. In Rb4B2S4O17 or Rb4[B2O(SO4)4] [Pnna, Z = 4, a = 8.0415(9), b = 10.6466(11), c = 20.425(2) A], there are isolated [B2O(SO4)4] units which consist of a central B2O7 unit. Besides one B–O–B bridge, two SO4 tetrahedra connect the BO4 tetrahedra. Additionally, each BO4 tetrahedron has a terminal SO4 unit. In the structure of A3HB4S2O14 or A3H(SO4)2(B2O3)2 [P63/m, Z = 2, A = Cs: a = 6.5648(2), c = 19.5669(5) A; A = Rb: a = 6.502(6), c = 19.023(14) A], the SO4 tetrahedra are isolated. Boron forms planar layers of corner-sharing trigonal-planar BO3 units. There are two different types of BO3 units in a ratio of 3:1. The first type forms six-membered boroxol rings, B3O3, which are connected to the layers by the second type of BO3 units. The layers are separated by isolated SO42– tetrahedra and Cs+ cations. The “missing” proton could not be localized but was assumed to achieve electroneutrality and was confirmed by IR spectroscopy. Planar layers of B2O3 with trigonal-planar BO3 units and boroxol rings are supposed to exist as structure elements in vitreous boron oxide.

ConspectusBoronyl (BO) is a monovalent σ radical with a robust B≡O triple bond. Although BO/BO– are isovalent to CN/CN– and CO, the chemistry of boronyl has remained relatively unknown until recently, whereas CN/CN– and CO are well-known inorganic ligands. Further analogy may be established for BO versus H or Au ligands, which are all monovalent σ radicals. This Account intends to provide an overview of research activities over the past few years that are relevant to the development of boronyl chemistry, in particular, in size-selected gaseous clusters containing BO. The systems covered herein include transition metal boronyl clusters, carbon boronyl clusters, boron oxide clusters and boron boronyl complexes, the boronyl boroxine, and the first synthetic Pt–BO bulk compound. In these boronyl clusters and compounds, the BO groups show remarkable structural and chemical integrity as a ligand.Among transition metal boronyls, gold monoboronyl clusters Aun(BO)− and Aun(BO) (n = 1–3) have been characterized, an...

The new title modification of B25C4Mg1.42 is synthesized from powders of magnesium, boron oxide, carbon black, and magnesium perchlorate by magnesiothermic self-propagating high-temperature synthesis.

Well-crystallized icosahedral B6O grains with diameters ranging from 100 nm to 1.3 μm are prepared from mixtures of boron and ball milled B2O3 powders (h-BN capsule, 2 GPa, 1400 °C, 6 h).

Na3B5O8S was prepared from the reaction of sodium sulphide with boron oxide and sodium carbonate at 500 °C in a graphitized silica tube. It is the first oxothioborate that could be synthesized and characterized by single-crystal X-ray diffraction. Na3B5O8S crystallizes in the monoclinic space group P21/c with a=11.390(2) A , b=6.249(1) A , c=10.934(2) A and β=93.94(2)°. In the structure, polymeric [B5O8S3−]n anions form two-dimensionally infinite layers containing groups of two spirocyclically connected six-membered B3O3 rings with one exocyclic sulphur atom bonded to one of them. Two of the five boron atoms are in tetrahedral BO4 coordination ( BO=1.433–1.504 A ) and three have trigonal planar BO3 or BO2S coordination ( BO=1.353–1.393 A , BS=1.813 A ). The three types of sodium cations between the layers are coordinated by 7 O, 4S+2O and 1S+6O atoms.

The Beckmann rearrangement of cyclohexanone oxime to caprolactam has been studied over a range of aluminas modified by the addition of chloride, phosphate, sulphate, sodium or boron oxide. The catalysts were characterized by temperature-programmed desorption of ammonia and carbon dioxide and by pyridine adsorption monitored by infrared spectroscopy. Conversion of the oxime declined with time-on-stream for all catalysts studied, but selectivity to caprolactam remained constant during the first five hours of operation. In this period a relationship was observed between the selectivity to cap- rolactam and the surface concentration of intermediate strength acid sites, wherein the selectivity increased as the surface concentration of these sites increased. The boron oxide modified alumina presented the largest concentration of intermediate strength acid sites, and the low level of coke formation on this material was associated with the total absence of surface basicity. A mechanism for the rear- rangement reaction on the modified aluminas is presented.

A novel method is described for the preparation of diborane froin aluminum, ethyl chloride, boron oxide and hydrogen via three steps: deoxyalkylation of boron oxide, hydrogenation of triethylboron and liberation of diborane. The triethylboron was prepared froin aluwiinunt, ethyl chloride and boron oxide directly at 85-110°C in 88% yield, with aluminum trichloride as by-product in 95% yield. In the presence of triethylamine and a hydrogen pressure of 130 kg/cin2, the triethylboron was hydrogenated at 200°C for 2 hours to produce borane-triethylamine complex in 92% yield. The borane-triethylaaniine complex was treated again at 80°C with the aluriiinuin trichloride collected from the first step to liberate diborane in 94% yield. The overall reaction yield was 76%.

Boron oxide catalysts supported on alumina have been prepared with boria loadings in the range 0–20 wt.-%. These materials were characterized by B.E.T. surface area measurements, X-ray diffraction and temperature-programmed desorption of ammonia and were used as catalysts for the Beckmann rearrangement of cyclohexanone oxime to caprolactam by passing the oxime vapour through a reactor containing the catalysts at 300°C. The surface areas of the samples decreased as the boria loading was increased, and all catalysts tested for the rearrangement reaction diminished in activity with time-onstream. There was a direct relationship between the amount of coke which formed on the surface and the loss in catalytic activity. This loss was least for the highest boron oxide loading tested, and this catalyst also featured the least amount of coke formation. Selectivity to caprolactam was associated with the presence of surface acidic sites of intermediate strength. A correlation was observed between the concentration of these surface sites and the selectivity to caprolactam.

Sintering of silicon carbide reinforced molybdenum disilicide-Composites using boron oxide as an additive was performed. The addition of boron oxide to the composites was found to be beneficial. It reduced the processing temperature, resulted in smaller grain sizes, and increased the flexural strength of the composites. Formation of glassy boundary phase was also found.

Potassium borosilicate glasses were prepared in families having the general formula of RK2O·B2O3·NSiO2, where R is the ratio of potassium oxide to boron oxide and N is the ratio of silicon dioxide to boron oxide. The glasses were prepared for values of R ranging from 0 to 7.0 in the families N= 0.5, 1.0, 2.0, and 4.0. 29Si MAS-NMR measurements were performed on these glasses to determine the short-range order around the silicon atom. A model of proportional sharing of the added potassium oxide between the silicate and the borate groups was suggested. This model was tested against other suggested models where proportional sharing begins after a minimum amount of potassium oxide, R0, and was observed to provide a better fit to the 29Si chemical shifts obtained. As was observed in the 29Si MAS-NMR studies of the RLi2O·B2O3·NSiO2 glasses, the proportional sharing model with R0= 0 is in stark disagreement with that proposed by the 11B NMR studies of the alkali borosilicate glasses. This problem is as yet not understood. Since K2CO3 was used as the starting material for K2O, it was observed that at large R values, R > RCO2, where RCO2= 2.3 for N= 1, RCO2= 4.0 for N= 2, and RCO2= 5.0 for N= 4, CO2 was retained in the melt in the fashion similar to that observed for other high-alkali borate and silicate glasses. The N= 0.5 family did not exhibit retention at the compositions studied. 29Si MAS-NMR could be used to determine where CO2 retention began in composition and the proportion of K2O/K2CO3 in the melt (glass).

A density functional theory and wave function theory investigation on the geometrical and electronic structures of B5O4(0/-) clusters has been performed in this work. B5O4(-) anion proves to possess a perfect tetrahedral ground state of T(d) B(BO)4(-) ((1)A1) analogous to BH4(-) with four equivalent -BO terminals around the B center, while B5O4 neutral favors a slightly off-planed C(s) B(BO)4 ((2)A') which contains three -BO terminals and one -O- bridge. An intramolecular BO radical transfer occurs from T(d) B(BO)4(-) to C(s) B(BO)4 when one electron is detached from the anion. The one-electron detachment energies of the anion and characteristic stretching vibrational frequencies of -B=O groups at about 2000 cm(-1) have been calculated to facilitate future experimental characterization of these clusters.

Alcohols, Formate esters, Formylation, MicrowaveConversion of alcohols into the corresponding formateesters has been received great attention and numbers ofsynthetic methods have been developed. For examples,formate esters have been prepared by the reaction ofalcohols with formic acid in the presence of a number ofreaction promoters such as boron oxide

To rationally design and explore a potential energy source based on the highly exothermic oxidation of boron, density functional theory (DFT) was used to characterize small boron clusters with 0-3 oxygen atoms and a total of up to ten atoms. The structures, vibrational frequencies, and stabilities were calculated for each of these clusters. A quantum molecular dynamics procedure was used to locate the global minimum for each species, which proved to be crucial given the unintuitive structure of many of the most stable isomers. Additionally, due to the plane-wave, periodic DFT code used in this study a straightforward comparison of these clusters to the bulk boron and B2O3 structures was possible despite the great structural and energetic differences between the two forms. Through evaluation of previous computational and experimental work, the relevant low-energy structures of all but one of the pure boron clusters can be assigned with great certainty. Nearly all of the boron oxide clusters are described here for the first time, but there are strong indications that the DFT procedure chosen is particularly well suited for the task. Insight into the trends in boron and boron oxide cluster stabilities, as well as the ultimate limits of growth for each, are also provided. The work reported herein provides crucial information towards understanding the oxidation of boron at a molecular level.

Usage of non-centrosymmetric boron oxide derivative crystals as nonlinear elements may be a key solution of pressing problem of obtaining powerful radiation at shorter wavelengths via frequency multiplication of solid state laser radiations. It is shown that Pb 2 B 5 O 9 Br and some other members of hilgardite-like borohalogenides demonstrate in powder form, high non-linear optical activity in the SHG experiments. An attempt is made using the Philips–Van Vechten–Levine–Xue bond theory to calculate second-order nonlinear coefficients for isostructural to mineral hilhardite noncentrosymmetric crystals M 2 B 5 O 9 X with M = Pb , Sr, Ba, Eu, Ca and X = Cl , Br. Theoretically obtained values of nonlinear optical coefficients d i j k only partly correlate with the results of SHG measurements. In particular, the experiments distinctively show sharp increase of nonlinear activity along the series Ca 3 triangles, though this factor is yet unable to explain enormously high SHG output from Pb 2 B 5 O 9 Br.

The state-of-the-art in boron chemistry, the characteristic features of boron compounds and crystalline phases based on them, the chemical bonds in these compounds and their electronic structures are considered. The physical principles of X-ray spectroscopy and the results it provided on the chemical structures of boron compounds and the nature of chemical bonds in them are discussed. Data for X-ray photoelectron and ultraviolet photoelectron spectroscopies for various elemental boron modifications, boron oxide phases, borides, nitrides, halides, derivatives of boron hydrides and carboranes, as well as metalloboranes are compared. The bibliography includes 247 references.

In this work we report about a new oxoborate β -ZnB 4 O 7 synthesized under high-pressure/high-temperature conditions from zinc oxide ZnO and boron oxide B 2 O 3 with a walker-type multianvil apparatus at 10.5 GPa and 1100 °C. Single crystal X-ray structure determination of β -ZnB 4 O 7 revealed: Cmcm , a =1085.0(1) pm, b =648.9(1) pm, c =517.3(1) pm, Z =4, R 1 =0.0182, wR 2 =0.0478 (all data). The compound exhibits a new structure type which is built up from linked tetrahedral BO 4 -groups (□) forming a network. The most prominent feature of the tetrahedral network is that there is an oxygen, which is coordinated to three borons. The network exhibits channels formed from four- and six-membered rings running along [001]. The Zn 2+ -cations are positioned in the large six-ring channels, whereas the channels built up by four membered rings remain empty. According to the conception of fundamental building blocks β -ZnB 4 O 7 can be classified with the notation 8□:〈3□〉=〈6□〉=〈3□〉. The relation of the crystal structure of the high-pressure phase β -ZnB 4 O 7 to the normal-pressure phase α -ZnB 4 O 7 is discussed. Furthermore we report about temperature-resolved in situ powder diffraction measurements and IR-spectroscopic investigations on β -ZnB 4 O 7 .

The frictional properties of sintered TiN-TiB2 and Ti(CN)-TiB2 ceramics were investigated in air at temperatures up to 1073 K. Friction coefficients as low as 0.1 to 0.2 can be obtained at 973 to 1073 K because oxidation of TiB2 produces a lubricating, glassy phase of boron oxide on the sliding surfaces.

B2O3–Al2O3, B2O3–MgO, B2O3–La2O3, and B2O3–P2O5 are selective catalysts for the partial oxidation of ethane. Among these catalysts, B2O3(30wt%)-added Al2O3 showed the highest catalytic activity in the formations of acetaldehyde (yield 1.03%) and ethylene (14.6%). Acetaldehyde is formed not via ethylene but directly from ethane. The formations of ethylene and acetaldehyde occur on different active sites.

Coupling of the allyl ethers (I) with the CH acidic compounds (II) and (V) in the presence of an equimolar quantity of boron oxide as activator and catalytic amounts of Pd(PPh3)4 leads to the formation of the allylated products (III) and (IV), or (VI).