Pentaborate Anions Research Articles

Hydrolysis mechanism of the cyclohexaborate anion: Unraveling the intricacies.

is a highly polymerized borate anion of three six-membered rings. Limited research on the hydrolysis mechanism under neutral solution conditions exists. Calculations based on density functional theory show that undergoes five steps of hydrolysis to form H3BO3 and . At the same time, there are a small number of borate ions with different degrees of polymerization during the hydrolysis process, such as triborate, tetraborate, and pentaborate anions. The structure of the borate anion and the coordination environment of the bridging oxygen atoms control the hydrolysis process. Finally, this work explains that in existing experimental studies, the reason for the low content in solution environments with low total boron concentrations is that it depolymerizes into other types of borate ions and clarifies the borate species. The conversion relationship provides a basis for identifying the possibility of various borate ions existing in the solution. This work also provides a certain degree of theoretical support for the cause of the "dilution to salt" phenomenon.

Crown ether complexes as a possible template for hybrid organic–inorganic borates

Abstract Crystals of the first new organo–inorganic hybrid borate based on potassium crown ether complex, [K(C12H24O6)B5O6(OH)4](H2O) (1), have been produced from aqueous solutions and characterized by single-crystal X-ray diffraction. 1 crystalizes is orthorhombic system, Pnma, a = 10.1684(3) Å, b = 11.6289(3) Å, c = 21.2247(6) Å, V = 2509.76(12) Å3, R obs = 0.059. The structure of 1 consists of molecular [K(C12H24O6)B5O6(OH)4]0 complexes, common for crown ether complexes but yet not among borates, with a very rare monodentate coordination of the common pentaborate anion(1-). The molecular complexes are linked into weak chains via hydrogen bonding to outer-sphere water molecules. Hirshfeld surfaces analysis and complexity measurement of 1 were performed. Perspectives of borate structures containing crown ether complexes as templates are briefly outlined.

Oxidoborates Templated by Cationic Nickel(II) Complexes and Self-Assembled from B(OH)3

Several oxidoborates, self-assembled from B(OH)3 and templated by cationic Ni(II) coordination compounds, were synthesized by crystallization from aqueous solution. These include the ionic compounds trans-[Ni(NH3)4(H2O)2][B4O5(OH)4].H2O (1), s-[Ni(dien)2][B5O6(OH)4]2 (dien = N-(2-aminoethyl)-1,2-ethanediamine (2), trans-[Ni(dmen)2(H2O)2] [B5O6(OH)4]2.2H2O (dmen = N,N-dimethyl-1,2-diaminoethane) (3), [Ni(HEen)2][B5O6(OH)4]2 (HEen = N-(2-hydroxyethyl)-1,2-diaminoethane) (4), [Ni(AEN)][B5O6(OH)4].H2O (AEN = 1-(3-azapropyl) -2,4-dimethyl-1,5,8-triazaocta-2,4-dienato(1-)) (5), trans-[Ni(dach)2(H2O)2][Ni(dach)2] [B7O9(OH)5]2.4H2O (dach = 1,2-diaminocyclohexane) (6), and the neutral species trans-[Ni(en)(H2O)2{B6O7(OH)6}].H2O (7) (en = 1,2-diaminoethane), and [Ni(dmen)(H2O){B6O7(OH)6}].5H2O (8). Compounds 1–8 were characterized by single-crystal XRD studies and by IR spectroscopy and 2, 4–7 were also characterized by thermal (TGA/DSC) methods and powder XDR studies. The solid-state structures of all compounds show extensive stabilizing H-bond interactions, important for their formation, and also display a range of gross structural features: 1 has an insular tetraborate(2-) anion, 2–5 have insular pentaborate(1-) anions, 6 has an insular heptaborate(2-) anion (‘O+’ isomer), whilst 7 and 8 have hexaborate(2-) anions directly coordinated to their Ni(II) centers, as bidentate or tridentate ligands, respectively. The Ni(II) centers are either octahedral (1–4, 7, 8) or square-planar (5), and compound 6 has both octahedral and square-planar metal geometries present within the structure as a double salt. Magnetic susceptibility measurements were undertaken on all compounds.

Hydrolysis mechanism of double six–membered ring pentaborate anion

DFT-based calculations show that B5O6(OH)4- forms B5O5(OH)6− intermediate during the first step of hydrolysis. Then, the hydrolysis pathways are divided to principal and secondary reactions. In the principal reaction, hydrolysis occurs at the bridge position between the six-membered ring and branch BO3 units to form B(OH)3 and B3O3(OH)4−. B3O3(OH)4− hydrolyzes in dilute solution to B(OH)3 and B(OH)4−. In the secondary reaction, hydrolysis of B5O5(OH)6− occurs at the bridge position in the ring to form a “network-chain” structure B5O4(OH)8−. Then, hydrolysis occurs at the bridge atoms, each BO3 unit is converted to B(OH)3, and BO4 unit is finally converted to B(OH)4−.

Synthesis and XRD study of an C2-linked bis(quaternary ammonium) pentaborate: [Me3NCH2CH2NMe3][B5O6(OH)4

The synthesis and characterization of a C2 (ethane) linked bis(trimethylammonium) pentaborate salt, [Me3NCH2CH2NMe3][B5O6(OH)4]2 (1), is reported . Compound 1 has been characterized by 1H, 11B, and 13C NMR Spectroscopy, IR spectroscopy, thermal (TGA/DSC) analysis, and single-crystal X-ray diffraction. There are two independent crystallographic pentaborate(1-) anions in the solid-state structure and these link by H-bonds at β-sites into a centrosymmetric tetrameric chain. These chains are crossed-linked by R22(8) H-bond motifs to α-sites of neighboring pentaborate tetrameric units. The [Me3NCH2CH2NMe3]2+ cations are located between these tetrameric pentaborate(1-) units.

Copper(2+) complexes of hydroxyoxidopolyborates: Synthesis and characterization of [Cu(MeNHCH2CH2NMeH)2(H2O)2][B5O6(OH)4]2.2B(OH)3

The pentaborate(1-) salt, [Cu(dmen)2(H2O)2][B5O6(OH)4]2.2B(OH)3(dmen = N,N′-dimethylethylenediamine, MeHNCH2CH2NHMe), has been synthesized in 48% yield as a crystalline product by reaction of B(OH)3 with [Cu(dmen)2](OH)2]2 (10:1 ratio) in aqueous solution. Single-crystal XRD analysis confirms its ionic structure with one interstitial B(OH)3 per pentaborate(1-) unit. The pentaborate(1-) anions and B(OH)3 molecules are involved in a supramolecular giant H-bonded lattice with B(OH)3 units serving as ‘spacers’ to help accommodate the relatively large [Cu(dmen)2(H2O)2]2+ cations.

The Solid State Structure of [TMEDAH2][B5O6(OH)4

The solid state structure of the pentaborate anion templated by a doubly protonated TMEDA cation is reported. The structure is typical of this family of ligands, featuring extensive hydrogen bonding. Spectroscopic characterisation is also reported.

Synthesis and characterization of polyborates templated by cationic copper(II) complexes: Structural (XRD), spectroscopic, thermal (TGA/DSC) and magnetic properties

Several polyborate containing species templated by cationic copper(II) coordination compounds have been synthesized. The ionic species [Cu(en)2][B5O6(OH)4]2·2H2O (en=1,2-diaminoethane) (1), [Cu(dmen)2(H2O)][B5O6(OH)4]2·3H2O (dmen=N,N-dimethyl-1,2-diaminoethane) (2), [Cu(pn)2{B5O6(OH)4}][B5O6(OH)4]·4H2O (pn=1,2-diaminopropane) (3), [Cu(dach)2(H2O)2][Cu(dach)2][B7O9(OH)5]2·4H2O (dach=1,2-diaminocyclohexane) (4), and the neutral species [Cu(dmen){B6O7(OH)6}]·4H2O (5) and [Cu(tmeda){B6O7(OH)6}]·6H2O (tmeda=N,N,N′,N′-tetramethyl-1,2-diaminoethane) (6) have been synthesized in aqueous solution and characterized by spectroscopic and thermal (TGA/DSC) methods. The previously prepared compound [Cu(en)2][B4O5(OH)4]2·2B(OH)3 (7) has also been prepared by an alternative route. Compounds 1–6 have been further characterized by single-crystal XRD studies. The new compounds show extensive H-bond interactions and display a range of structural features: 1–3 have isolated pentaborate(1-) anions whilst 4 possesses an isolated heptaborate(2-) anion. In addition, 3 has a pentaborate(1-) and 5 and 6 have hexaborate(2-) anions directly coordinated to their copper(II) centers, in mondentate and tridentate manners, respectively. The copper(II) centers show a variety of coordination numbers and geometries: square-planar (1, 7), octahedral (4) and square-based pyramidal (2, 3, 5, 6). Thermal studies (TGA/DSC) and magnetic susceptibility measurements have been undertaken on all compounds.

Hydrogen-bonded assemblies of two organically templated borates: syntheses and crystal structures of [(1,10-phen)(H3BO3)2] and [2-EtpyH][(B5O6(OH)4

Abstract Two new organically templated borates, [(1,10-phen)(H3BO3)2] (1) and [2-EtpyH][(B5O6(OH)4] (2), were synthesized under mild solvothermal conditions and characterized by single-crystal X-ray diffraction, FT-IR, elemental analyses and thermogravimetry. Complex 1 is a co-crystal component in which B(OH)3 molecules form crinkled tapes via hydrogen bonds, which in turn are packed in a two-dimensional framework with 1,10-phen molecules sandwiched between the framework of crinkled chains. The structure of complex 2 is composed of 2-ethylpyridinium cations [2-EtpyH]+ and pentaborate anions [B5O6(OH)4]– which are linked together with hydrogen bonds to form a three-dimensional supramolecular framework. The templating [2-EtpyH]+ cations are situated in the cavities arising from the supramolecular pentaborate framework and interact also with the inorganic framework through hydrogen bonds.

Synthesis, spectroscopic and thermal characterization of non-metal cation (nmc) pentaborates salts containing 2-amino-5-nitropyridine and 2-amino-6-methylpyridine as cation

ABSTRACT The pyridine derivatives, 2-amino-5-nitropyridine and 2-amino-6-methylpyridine (6-aminopicolin), were used that for synthesis of two new non-metal cation (NMC)s pentaborate structures. The NMCs pentaborate molecules were characterized using 11B-NMR, elemental analysis, BET, FT-IR, P-XRD and melting points technics. The thermal properties had been investigated by TGA/DTA/DTG methods. 2-amino-5-nitropyridine and 2-amino-6-methyl pyridine (NMC)s pentaborates showed different thermal stabilities among each other, but degradation of the dehydration of the following organic both NMC pentaborate structure as part away and decomposition products of B2O3 occurs by having glassy structure. The trigonal (BO3) and tetragonal (BO4-) moities were determined in 11B NMR spectrums. According to P-XRD methods each of the compound structures are crystalline form. The peaks of pentaborate anion [B5O6(OH)4]- were seemed in FT-IR spectra. Lastly, the hydrogen storage properties were studied of these molecules. The estimated molecular formulas of the complexes are as follows: 2-amino-5-nitropyridine pentaborate: [C5H5N3O2][B5O6(OH)4]3H2O 2-amino-6-methylpyridine pentaborate: C6H8N2][B5O6(OH)4]2H2O Keywords: Boron; Non-metal cation borate structure; Pentaborate; P-XRD; Thermal investigation; 11B-NMR DOI: 10.17350/HJSE19030000014 Full Text:

A new decaoxidooctaborate(2-) anion, [B8O10(OH)6](2-): synthesis and characterization of [Co(en)3][B5O6(OH)4][B8O10(OH)6)]·5H2O (en = 1,2-diaminoethane).

The synthesis and X-ray diffraction structure of [Co(en)3][B5O6(OH)4][B8O10(OH)6]·5H2O (1) are reported. Compound 1 arises through a selective-templating process from a Dynamic Combinatorial Library of polyborate anions. Compound 1 contains two different polyborate species, with [B8O10(OH)6](2-) being particularly novel. It is comprised of fused tetraborate and pentaborate anions with a 4-coordinate B atom and a 3-coordinate O atom in common.

Hydrogen bonded anion ribbons, networks and clusters and sulfur–anion interactions in novel radical cation salts of BEDT-TTF with sulfamate, pentaborate and bromide

The novel radical cation salt (BEDT-TTF)3(sulfamate)2·2H2O (BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene) is semiconducting with donor stacks comprised of pairs of partially oxidized molecules and a single more highly oxidized molecule which is twisted out of the stack by ca. 30°. Hydrogen bonded pairs of sulfamate ions are linked into parallel ribbons by further hydrogen bonding between sulfamates and bridging water molecules. In contrast, the BEDT-TTF salt with pentaborate contains infinite layers formed of a network of hydrogen bonded pentaborate anions. Two new bromide salts of BEDT-TTF are reported, one is a semiconducting 1 : 1 salt in which the bromide is integrated among the BEDT-TTF donors, while the other contain a square of four bromide ions linked together by hydrogen bonding to a centrally located H5O2(+) cation for every five BEDT-TTF molecules.

An Organically Templated Copper Pentaborate with Infinite Metallo‐chains: [Cu(C3N2H4)4][Cu(CH3COO)2(C3N2H4)2(H2O)2][B5O6(OH)4]2

AbstractA novel organically templated copper pentaborate, [Cu(C3N2H4)4][Cu(CH3COO)2(C3N2H4)2(H2O)2]‐ [B5O6(OH)4]2, was synthesized by hydrothermal reaction and characterized by elemental analysis, single‐crystal X‐ray diffraction, FT‐IR spectroscopy, Raman spectroscopy and TGA. The crystal structure of this compound consists of two copper‐centered polyhedra and two discrete [B5O6(OH)4]− pentaborate anions, which are linked together through intensive hydrogen bonding interactions, forming a 3D framework with large channels along c axis. The discrete pentaborate anions form infinite layers by hydrogen bonds. Moreover, the two crystallographically different octahedral coppers are connected by common oxygen atom to form an infinite chain.

Synthesis, characterization, and thermal properties of benzylammonium pentaborate [C6H5CH2NH3][B5O6(OH)4

[C6H5CH2NH3][B5O6(OH)4] was obtained as colourless crystals in high yield from a MeOH/ H2O (1:1) solution of benzylamine and boric acid (1:5). A single-crystal X-ray study confirmed that the solid-state structure was comprised of a supramolecular H-bonded pentaborate anion lattice, templated by the benzylammonium cations which occupy positions within the lattice cavities. Each pentaborate anion formed 4 H-bonds to 4 neighbouring pentaborate anions at α,α,α,β acceptor sites. Additionally, each cation H-bonds to 3 pentaborate anions. Crystals were monoclinic, P21/c, with a = 9.3511(2) Å, b = 14.5157(4) Å, c = 10.4670(2) Å, β = 90.778(2)°, T = 120 K, V = 1420.64(6) Å3, and Z = 4. TGA/DSC analysis showed that [C6H5CH2NH3][B5O6(OH)4] thermally decomposed in air at 800 °C to 2.5B2O3, via a low-temperature (200–250 °C) dehydration step to a condensed pentaborate.

Structural (XRD) and thermal (DSC, TGA) and BET analysis of materials derived from non-metal cation pentaborate salts

The synthesis, structural characterization (XRD), and thermal properties of nine non-metal cation (NMC) pentaborate anion salts, [NMC][B(5)O(6)(OH)(4)] (1a-1i) is described (NMC = [NH(3)CMe(2)(CH(2)OH)](+) (a), [O(CH(2)CH(2))(2)NH(2)](+) (b), [NH(3)CMe(CH(2)OH)(2)](+) (c), [2-(2-CH(2)CH(2)OH)PyH](+) (d), [(CH(2))(4)NH(CH(2)CH(2)OH)](+) (e), [(CH(2))(5)NH(CH(2)CH(2)OH)](+) (f), [2-MeImid](+) (g), [Me(3)NCMe(2)(CH(2)OH)](+) (h), [O(CH(2)CH(2))(2)NMe(2)](+) (i). Single-crystal X-ray diffraction studies on all compounds show that they contain isolated pentaborate anions, H-bonded together in a supramolecular array, with the cations occupying the cavities within the network. Compound 1c was obtained as a partial hydrate (0.16H(2)O). TGA and DSC analysis (in air, 25-1000 degrees C) indicate that compounds 1a-1i thermally decompose via a 2 stage process to B(2)O(3). The first stage (<250 degrees C) is dehydration to condensed polymeric pentaborates {approximate composition: [NMC][B(5)O(8)] (2a-2i)}. Five condensed pentaborates (2a-c, 2e, 2g) were synthesised and characterized by powder XRD and BET analysis. These condensed pentaborates were amorphous. The isolated pentaborates intumesced at approximately 600 degrees C (occupying approximately 10 times their original volume), and then contracted back to black glassy B(2)O(3) solids at 1000 degrees C. The intumescent materials (3a), (3b), (3e), (3g), and a final B(2)O(3) sample (4b) were synthesised and isolated and their porosities determined. BET surface area analysis on the isolated pentaborates (1a-c, 1e, 1g), the condensed pentaborates (2a-c, 2e, 2g), intumesced materials (3a, 3b, 3e, 3g), and B(2)O(3) (4b) showed that they were all 'non-porous' (<1.59 m(2) g(-1)).

A 11B NMR study of zwitterionic and cationic monoborate complexes with cationic 1,2-diol ligands

The interaction of B(OH) 3 with [R 3N{CH 2CH(OH)CH 2OH}] [OH] (R 3 = Me 3, Me 2Et, MeEt 2, Me 2Bz, Me 2{CH 2CH 2OH}) in a 1:2, 1:1, and 5:1 ratio in aqueous solution has been studied by 11B NMR spectroscopy and the equilibrium species present have been identified. The cationic bischelate [R 3N{CH 2CH(O)CH 2O} 2B] + dominates the 2:1 ratio solutions, zwitterionic monochelate species, [R 3N{CH 2CH(O)CH 2O}B(OH ) 2], dominate the 1:1 solutions and the pentaborate anion, [B 5O 6(OH) 4] −, dominates the 1:5 solutions. Borate solutions derived from [NMe 4][OH] and [Me 3NCH 2CH 2OH][OH] have also been studied by 11B NMR. Spectra of these borate solutions are essentially the same as those observed for borate solutions with alkali metal cations, and structure directing effects (towards the anion) are not observed in borate systems.

Supramolecular structures containing ‘isolated’ pentaborate anions and non-metal cations: Crystal structures of [Me 3NCH 2CH 2OH][B 5O 6(OH) 4] and [4-MepyH, 4-Mepy][B 5O 6(OH) 4

The solid-state structures of two non-metal pentaborates [Me 3NCH 2CH 2OH][B 5O 6(OH) 4] ( 1) and [4-MepyH, 4-Mepy][B 5O 6(OH) 4] ( 2) have been determined by single-crystal X-ray diffraction methods. Structures 1 and 2 both contain supramolecular pentaborate frameworks held together by extensive H-bond interactions. The framework of 1 exists essentially as planes of pentaborate anions linked via three pairwise ‘planar’ β → α interactions, with a fourth β → β interaction crosslinking the planes. The framework of 2 is very similar except that one of the three pairwise linkages within the plane is replaced by pairwise ‘step-like’ bifurcated H-bonds to both α sites of a neighboring anion. The cations in 1 and the cations and neutral 4-Mepy ligands in 2 are present in the framework cavities and channels, with additional H-bond interactions existing between cations and anions.

Poly[propane-1,3-diammonium hydroxydeca-μ2-oxo-pentaborate

The title compound, {C3H12N2 2+·B5O8(OH)2−} n , has been synthesized under mild solvothermal conditions in the presence of 1,3-diaminopropane acting as a template. The structure consists of two-dimensional polymeric sheets constructed from [B5O8(OH)]2− pentaborate anions. Adjacent borate sheets are linked by O—H...O hydrogen bonds to form a three-dimensional framework with channels running along one direction. The propane-1,3-diammonium cations lie within the channels, interacting with the framework through N—H...O hydrogen bonds.

Poly[ethylenediammonium hydroxydeca-μ2-oxo-pentaborate

The title compound, {C2H10N2 2+·B5O8(OH)2−} n , has been hydrothermally synthesized. The structure consists of two-dimensional polymeric sheets constructed from [B5O8(OH)]2− pentaborate anions. Adjacent borate sheets are linked by O—H...O hydrogen bonds into a three-dimensional framework with channels running along one direction. The ethylenediammonium cations lie on centres of inversion within the channels, interacting with the framework through N—H...O hydrogen bonds.

Syntheses and crystal structures of two new organically templated borates

Two new organically templated borates, [H 3N(C 6H 10)NH 3][B 4O 5(OH) 4] (1) and [H 3N(C 6H 10)NH 3][B 5O 8(OH)] (2) have been synthesized in the presence of trans-1,4-diaminocyclohexane acting as a structure-directing agent under mild solvothermal conditions. The structures were determined by single crystal X-ray diffraction and further characterized by FTIR, elemental analysis and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic system, space group C2/ c (No. 15), a = 9.1325 ( 3 ) Å , b = 11.4869 ( 3 ) Å , c = 12.2756 ( 5 ) Å , β=105.258(6)°, V = 1242.37 ( 7 ) Å 3 , Z = 4 . The structure contains supramolecular hydrogen-bonded network formed by isolated [B 4O 5(OH) 4] 2− polyanions. 2 is monoclinic, space group P2( 1)/ n (No. 14), a = 6.5176 ( 2 ) Å , b = 16.8861 ( 5 ) Å , c = 11.1522 ( 7 ) Å , β=91.897(6)°, V = 1226.70 ( 9 ) Å 3 , Z = 4 . The structure consists of layers of 3,9-membered boron rings constructed from pentaborate anion groups [B 5O 8(OH)] 2−. The adjacent borate layers are further linked with each other by hydrogen bond to form a 3D supramolecular network. It is the first example of layered borates templated by an organic amine.