A New Ammine Dual‐Cation (Li,Mg) Borohydride: Synthesis,Structure, and Dehydrogenation Enhancement

A new ammine dual‐cation borohydride, LiMg(BH₄)₃(NH₃)₂, has been successfully synthesized simply by ball‐milling of Mg(BH₄)₂ and LiBH₄ ? NH₃. Structure analysis of the synthesized LiMg(BH₄)₃(NH₃)₂ revealed that it crystallized in the space group P6₃ (no. 173) with lattice parameters of a=b=8.0002(1) Å, c=8.4276(1) Å, α=β=90°, and γ=120° at 50 °C. A three‐dimensional architecture is built up through corner‐connecting BH₄ units. Strong N? H???H? B dihydrogen bonds exist between the NH₃ and BH₄ units, enabling LiMg(BH₄)₃(NH₃)₂ to undergo dehydrogenation at a much lower temperature. Dehydrogenation studies have revealed that the LiMg(BH₄)₃(NH₃)₂/LiBH₄ composite is able to release over 8 wt % hydrogen below 200 °C, which is comparable to that released by Mg(BH₄)₃(NH₃)₂. More importantly, it was found that release of the byproduct NH₃ in this system can be completely suppressed by adjusting the ratio of Mg(BH₄)₂ and LiBH₄ ? NH₃. This chemical control route highlights a potential method for modifying the dehydrogenation properties of other ammine borohydride systems.     

Ammonia-Borane Derived BN Fragments Trapped on Bi- and Trimetallic Titanium(III) Systems

Titanium(III) complexes containing unprecedented (NH₂BH₂NHBH₃)²⁻ and {N(BH₃)₃}³⁻ ligands have been isolated, and their structures elucidated by a combination of experimental and theoretical methods. The treatment of the trimethyl derivative [TiCp*Me₃] (Cp*=η⁵-C₅Me₅) with NH₃BH₃ (3 equiv) at room temperature gives the paramagnetic dinuclear complex [{TiCp*(NH₂BH₃)}₂(μ-NH₂BH₂NHBH₃)], which at 80 °C leads to the trinuclear hydride derivative [{TiCp*(μ-H)}₃{μ₃-N(BH₃)₃}]. The bonding modes of the anionic BN fragments in those complexes, as well as the dimethylaminoborane group trapped on the analogous trinuclear [{TiCp*(μ-H)}₃(μ₃-H)(μ₃-NMe₂BH₂)], have been studied by X-ray crystallography and density functional theory (DFT) calculations.     

Non-convertional hydrogen bonding interaction of BH3NH3 complexes: a comparative theoretical study

A new type of hydrogen bond, called a dihydrogen bond, has recently been introduced. In this bond hydrogen is donated to (hydridic) hydrogen. In this paper, ab initio HF, MP2 and DFT(B3LYP) levels of theory with different basis sets in combination with counterpoise procedure for basis set superposition error correction have been applied to BH₃NH₃ dimer and BH₃NH₃ complexes of methane, hydrogen cyanide, ammonia, water, methanol and hydrogen fluoride to understand the features of dihydrogen bond. The optimized geometric parameters and interaction energies for various isomers at different levels are estimated. The structures obtained at different computational levels are in agreement with each other. Dihydrogen bond does not occur in both BH₃NH₃⋯CH₄ and BH₃NH₃⋯NH₃ complexes. Apart from the B–H⋯H–N dihydrogen bond found in the BH₃NH₃ crystal and dimmer, the B–H⋯H–X (XC, O, F) dihydrogen bonds have been observed in the BH₃NH₃⋯HCN, BH₃NH₃⋯H₂O, BH₃NH₃⋯CH₃OH and BH₃NH₃⋯HF complexes, while the classic H bonds also exist in the last three complexes. As for the complexes in which only dihydrogen bonds appear the strength of dihydrogen bonds ranges from 17.9 to 18.9 kJ mol⁻¹ at B3LYP/6-311++g(d,p) level. Binding energies obtained from the MP2 and B3LYP optimized structures are more sensitive to basis sets than those from the HF method. Larger basis functions generally tend to produce slightly longer intermolecular distances, and the B3LYP and MP2 methods generate shorter intermolecular distances though they usually produce longer bond lengths compared with those at the HF level. The infrared spectrum frequencies, IR intensities and the vibrational frequency shifts are reported. Finally the solution phase studies on BH₃NH₃⋯HF complex are also carried out using the Onsager reaction field model with a range of dielectric constants from 2 to 80 at B3LYP/6-311++g(d,p) level.     

A theoretical approach to substituent effects: Interaction between directly bonded groups in the isoelectronic series XNH3+, XCH3, and XBH3−

Ab initio molecular orbital theory including full geometry optimization at the 4-31G level is used to examine the interactions between substitutents X(X = Li, BeH, BH₂, CH₃, NH₂, OH and F) and substrates Y(Y = NH₃⁺, CH₃, BH₃^?) in the isoelectronic series XNH₃⁺, XCH₃ and XBH₃^?. The results indicate that the interaction energies are dominated by σ-effects. NH₃⁺ is found to interact favorably with the σ-donors (e.g. Li, BeH and BH₂) and unfavorably with the σ-acceptors (e.g. F, OH, NH₂). The reverse pattern a observed for XBH₃^?. The range of interaction energies for XCH₃ is considerably smaller than for XNH₃⁺ and XBH₃^?.     

New phosphaneborane chemistry

Following a short account of pertinent literature, recent work on two classes of phosphaneboranes is summarized.H₃B(CH₃)₂PCl (1) was found to be an excellent precursor for an extended new chemistry of the H₃B(CH₃)₂P-group, which is isoelectronic with the (CH₃)₃Si-group. Boranatodimethylphosphinic acid H₃B(CH₃)₂POH, its anhydride H₃B(CH₃)₂POP(CH₃)₂BH₃, salts, complexes, esters and carboxylates have been prepared and identified through analytical and spectroscopic studies. The corresponding sulphur analogues are also available. The amide H₃B(CH₃)₂PNH₂ is formed from 1 and NH₃ as a stable crystalline product. It is easily converted into its imide H₃B(CH₃)₂PNHP(CH₃)₂BH₃ and a variety of organic derivatives. H₃B(CH₃)₂PCH₂P(CH₃)₂BH₃ has protic hydrogen atoms in the CH₂ bridge and affords a crystalline ylidic Li salt, the crystal structure of which was determined. CH₃ metallation of (CH₃)₃PBH₃ leads to similar product useful for derivatisation.The (CH₃)₃PBH₂P(CH₃)₃⁺X^? salts are starting materials for the preparation of the novel ^?CH₂(CH₃)₂PBH₂P(CH₃)₂CH₂^? ligand system. Its coordination chemistry, with examples from most groups of the Periodic Table, is reviewed, including both diamagnetic and paramagnetic species. Representative structures were determined by X-ray diffraction, and multi-nuclei NMR and magnetic data were used for further characterisation.     

Synthesis of Ammonia Borane Nanoparticles and the Diammoniate of Diborane by Direct Combination of Diborane and Ammonia

Pure nanoparticle ammonia borane (NH₃BH₃, AB) was first prepared through a solvent‐free, ambient‐temperature gas‐phase combination of B₂H₆ with NH₃. The prepared AB nanoparticle exhibits improved dehydrogenation behavior giving 13.6 wt. % H₂ at the temperature range of 80–175 °C without severe foaming. Ammonia diborane (NH₃BH₂(μ‐H)BH₃, AaDB) is proposed as the intermediate in the reaction of B₂H₆ with NH₃ based on theoretical studies. This method can also be used to prepare pure diammoniate of diborane ([H₂B(NH₃)₂][BH₄], DADB) by adjusting the ratio and concentration of B₂H₆ to NH₃.     

Past,present and future of the clathrate inclusion compounds built of cyanometallate hosts

One-, two- and three-dimensional CN-bridged metal complex structures made up of building blocks such as linear [Ag(CN)₂]^–, square planar [Ni(CN)₄]^2– or tetrahedral [Cd(CN)₄]^2–, and of the complementary ligands such as ammonia, water, unidentate amine, bidentate a,w- diaminoalkane, etc., are reviewed with an emphasis on their behaviour as hosts to afford clathrate inclusion compounds with guest molecules and as self-assemblies to form supramolecular structures with or without guests. The historical background is explained for Prussian blue and Hofmann's benzene clathrate based on their single crystal structure determinations. The strategies the author and coworkers have been applying to develop varieties of clathrate inclusion compounds from the Hofmann-type are demonstrated with the features observed for the developed structures determined by single crystal X-ray diffraction methods.Abbreviations for Ligands and Guests mma NMeH₂ - dma NMe₂H - tma NMe₃ - mea NH₂(CH₂)₂OH - en NH₂(CH₂)₂NH₂ - pn NH₂CHMeCH₂NH₂ - tn NH₂(CH₂)₃NH₂ - dabtn NH₂(CH₂)₄NH₂ - daptn NH₂(CH₂)₅NH₂ - dahxn NH₂(CH₂)₆NH₂ - dahpn NH₂(CH₂)₇NH₂ - daotn NH₂(CH₂)₈NH₂ - danon NH₂(CH₂)₉NH₂ - dadcn NH₂(CH₂)₁₀NH₂ - mtn NMeH(CH₂)₃NH₂ - dmtn NMe₂(CH₂)₃NH₂ - detn NEt₂(CH₂)₃NH₂ - temtn NMe₂(CH₂)₃NMe₂ - dien NH₂(CH₂)₂NH(CH₂)₂NH₂ - pXdam p-C₆H₄(NH₂CH₂)₂ - rnXdam m-C₆H₄(NH₂CH₂)₂ - py C₅H₅N pyridine - ampy NH₂C₅H₄N aminopyridine - Clpy CIC₅H₄N chloropyridine - Mepy MeC₅H₄N methylpyridine - dmpy Me₂C₅H₃N dimethylpyridine - bpy NC₅H₄C₅H₄N bipyridine - quin C₇H₉N quinoline - iquin iso-C₇H₉N isoquinoline - qxln C₈H₆N₂ quinoxaline - Pe C₅H₁₁-pentyl imH: C₃N₂H₄ imidazole - pyrz N(CHCH)₂N pyrazine - Mequin MeC₇H₈N methylquinoline - bppn C₁₃H₁₄N₂ 1,3-bis(4-pyridyl)propane - bpb C₁₄H₈N₂ 1,4-bis(4-pyridyl)butadiyne - N-Meim C₃N₂H₃Me N-methylimidazole - 2-MeimH C₃N₂H₃Me 2-methylimidazole - dmf HOCNMe₂ dimethylformamide - hmta C₆H₁₂N₄ hexamethylenetetramine - o-phen C₁₂H₈N₂ 1,10-phenanthroline - den HN(CH₂CH₂)₂NH piperazine - morph HN(CH₂CH₂)₂O morpholine - ten N(CH₂CH₂)₃N 1,4-diazabicyclo[2.2.2]octane - ameden NH₂(CH₂)₂N(CH₂CH₂)₂NH N-(2-aminoethyl)piperazine Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Integrated spatial electron populations in molecules: Application to simple molecules

The electron projection function P(x, z) = ∫ ρ(x, y, z) dy is used to evaluate charge transfer and covalency in two series of molecules, LiX and CH₃X (X = Li, BeH, BH₂, CH₃, NH₂, OH, and F), with wavefunctions derived from STO-3G, 4-31G, and, in some cases, 6-31* ab initio calculations. The precision of the method and comparison with Mulliken populations analysis are described. Particular attention is given to CH₃Li which by our criteria is wholly ionic.     

Metal‐Borohydride‐Modified Zr(BH4)4⋅8 NH3: Low‐Temperature Dehydrogenation Yielding Highly Pure Hydrogen

Due to its high hydrogen density (14.8 wt %) and low dehydrogenation peak temperature (130 °C), Zr(BH₄)₄ ? 8 NH₃ is considered to be one of the most promising hydrogen‐storage materials. To further decrease its dehydrogenation temperature and suppress its ammonia release, a strategy of introducing LiBH₄ and Mg(BH₄)₂ was applied to this system. Zr(BH₄)₄ ? 8 NH₃–4 LiBH₄ and Zr(BH₄)₄ ? 8 NH₃–2 Mg(BH₄)₂ composites showed main dehydrogenation peaks centered at 81 and 106 °C as well as high hydrogen purities of 99.3 and 99.8 mol % H₂, respectively. Isothermal measurements showed that 6.6 wt % (within 60 min) and 5.5 wt % (within 360 min) of hydrogen were released at 100 °C from Zr(BH₄)₄ ? 8 NH₃–4 LiBH₄ and Zr(BH₄)₄ ? 8 NH₃–2 Mg(BH₄)₂, respectively. The lower dehydrogenation temperatures and improved hydrogen purities could be attributed to the formation of the diammoniate of diborane for Zr(BH₄)₄ ? 8 NH₃–4 LiBH₄, and the partial transfer of NH₃ groups from Zr(BH₄)₄ ? 8 NH₃ to Mg(BH₄)₂ for Zr(BH₄)₄ ? 8 NH₃–2 Mg(BH₄)₂, which result in balanced numbers of BH₄ and NH₃ groups and a more active H^δ+ ??? ^?δH interaction. These advanced dehydrogenation properties make these two composites promising candidates as hydrogen‐storage materials.     

Formation and Unimolecular Dehydrogenation of Gaseous Alkaline‐earth Metal Amidoboranes M(NH2BH3)2 (M = Be – Ba): Comparative Computational Study

Formation of alkaline‐earth metal amidoboranes M(NH₂BH₃)₂ (M = Be, Mg, Ca, Sr, Ba) and unimolecular dehydrogenation reactions were computationally studied at the B3LYP/def2‐TZVPPD level of theory. Formation of M(NH₂BH₃)₂ from ammonia borane and MH₂ is exergonic, but subsequent unimolecular dehydrogenation reactions are endergonic at room temperature. In contrast to alkali metal amidoboranes, for M(NH₂BH₃)₂ the nature of M significantly affects their reactivity. Activation energies for the dehydrogenation of first and second hydrogen molecules decrease from Be to Ba. In case of Be compounds, intramolecular M ··· H–B contacts play an important role, whereas for heavier analogs such contacts are much less pronounced.     

Computation of the complexation energies of BH3NH3 and BH3PH3

Extended basis set computations on SCF and CEPA level were performed for BH₃NH₃ and BH₃PH₃ to determine the complexation energy ΔE and the equilibrium distance r(BX) between the “heavy” atoms. Our CEPA results (SCF in parentheses): ΔE(BH₃NH) = ?27(?21.3) kcal/mol, ΔE(BH₃PH₃) = ?17(?11.8) kcal/mol, r(BN) = 1.65(1.68) Å, r(BP) = 1.95(1.99) Å indicate a marked influence of electron correlation on these properties.     

Microwave spectrum,structure and dipole moment of trimethylamine-borane

The ground state rotational spectra often isotopic species of trimethylamineborane, (CH₃)₃N¹⁰BH₃, (CH₃)₃N¹¹BH₃, (CH₃)₃N¹⁰BD₃, (CH₃)₃N¹¹BD₃, (CH₃)₃N¹¹BD₂H, (CD₃)₃N¹⁰BH₃, (CD₃)₃N¹¹BH₃, (CD₃)₃N¹⁰BD₃, (CD₃)₃N¹¹BD₃ and (¹³CH₃)(¹²CH₃)₂N¹¹BH₃, have been measured and the effective moments of inertia obtained. The utilization of Kraitchman's equations leads to an r_s value of the B-H distance of 1.211±0.003 Å and a NBH angle of 105.32±0.16°. By a least squares fit of the rotational constants the following structural parameters were obtained: r(NC) = 1.495 Å, r(BN) = 1.609 Å, and ∠BNC = 110.9°. The value of the dipole moment was found to be 4.59±0.13 D. A lower limit to the barrier to internal rotation of the BH₃ group was determined to be 3.4 kcal/mole.     

Electron impact ionization of ethylene–methanol heteroclusters: Stable configurations and mechanisms in intracluster ion–molecule reactions

Reactions that proceed within mixed ethylene–methanol cluster ions were studied using an electron impact time-of-flight mass spectrometer. The ion abundance ratio, [(C₂H₄)_n(CH₃OH)_mH⁺]/[(C₂H₄)_n(CH₃OH)_m⁺], shows a propensity to increase as the ethylene/methanol mixing ratio increases, indicating that the proton is preferentially bound to a methanol molecule in the heterocluster ions. The results from isotope-labelling experiments indicate that the effective formation of a protonated heterocluster is responsible for ethylene molecules in the clusters. The observed (C₂H₄)_n(CH₃OH)_m⁺ and (C₂H₄)_n(CH₃OH)_m–1CH₃O⁺ ions are interpreted as a consequence of the ion–neutral complex and intracluster ion–molecule reaction, respectively. Experimental evidence for the stable configurations of heterocluster species is found from the distinct abundance distributions of these ions and also from the observation of fragment peaks in the mass spectra. Investigations on the relative cluster ion distribution under various conditions suggest that (C₂H₄)_n(CH₃OH)_mH⁺ ions with n + m ≤ 3 have particularly stable structures. The result is understood on the basis of ion–molecule condensation reactions, leading to the formation of fragment ions, $ {\rm CH}_2=\!=\mathop {\rm O}\limits^ + {\rm CH}_3 $ and (CH₃OH)H₃O⁺, and the effective stabilization by a polar molecule. The reaction energies of proposed mechanisms are presented for (C₂H₄)_n(CH₃OH)_mH⁺(n + m ≤ 3) using semi-empirical molecular orbital calculations.     

Calculations of nuclear electric shielding in molecules

The electric shielding tensor at nuclei in the molecules H₂O, NH₃, CH₄ and CO has been evaluated via coupled Hartree-Fock perturbation theory. The average trace of the shielding tensor is linearly dependent on atomic electronegativities in the isoelectronic series H₂O, NH₃, CH₄.     

Crystallographic report: Synthesis and biological evaluation of novel azanonaboranes as potential agents for boron neutron capture therapy

A number of (hydroxyalkylamine)‐N‐(aminoalkyl)azanonaborane(11) derivatives have been synthesized to provide azanonaboranes with different hydrophilic functional groups for use in the treatment of cancer by boron neutron capture therapy (BNCT). The exo‐diamine group of (aminoalkylamine)‐N‐(aminoalkyl)azanonaborane(11) {H₂N(CH₂)_mH₂NB₈H₁₁NH(CH₂)_mNH₂, where m = 4–6} can be substituted by amino alcohol ligands {HO(CH₂)_nNH₂, where n = 3 and 4} to give azanonaboranes containing free amino and hydroxy groups: (3‐hydroxypropylamine)‐N‐(aminobutyl)azanonaborane(11) {HO(CH₂)₃H₂NB₈H₁₁NH(CH₂)₄NH₂}, 1 ; (4‐hydroxybutylamine)‐N‐ (aminobutyl)azanonaborane(11) {HO(CH₂)₄H₂NB₈H₁₁NH(CH₂)₄NH₂}, 2 ; (3‐hydroxypropylamine)‐N‐ (aminopentyl)azanonaborane(11) {HO(CH₂)₃H₂NB₈H₁₁NH(CH₂)₅NH₂}, 3 ; (4‐hydroxypropylamine)‐N‐(aminopentyl)azanonaborane(11) {HO(CH₂)₄H₂NB₈H₁₁NH(CH₂)₅NH₂}, 4 ; (3‐hydroxypropylamine)‐N‐(aminohexyl)azanonaborane(11) {HO(CH₂)₃H₂NB₈H₁₁NH(CH₂)₆NH₂}, 5 . The in vitro toxicity test using Chinese hamster‐V79 cells showed that compounds 1 – 3 were less toxic (LD₅₀ value of ～2.3, 1.7 and 1.4 mM , respectively) than spermine and spermidine (LD₅₀ value of ～0.88 and 0.66 mM , respectively). In vivo distribution experiments of these compounds in Lewis lung carcinoma and B16 melanoma tumor‐bearing mice showed that boron can be found in tumor tissue. The compounds prepared can be considered as a new class of boron containing polyamine compounds that may be useful for boron neutron capture therapy of tumors. Copyright © 2005 John Wiley & Sons, Ltd.     

Solvothermal Synthesis and Structure of Two 2D Tin–Selenides with Long Alkyldiamine NH2(CH2) n NH2 (n = 8, 10)

Reactions of NH₂(CH₂) _n NH₂ (n = 8,10) with elemental Sn and Se in a H₂O/CH₃OH mixture at 150°C afford two compounds (NH₃(CH₂)₈NH₃)Sn₃Se₇ (1) and (NH₃(CH₂)₈NH₃)Sn₃Se₇ (2). The crystal structures were determined by single crystal X-ray diffraction at room temperature. Both compounds exhibit the same anionic structure—a 6³ netted plane composed of [Sn₃Se₇]^2– subunits. The distance between the centers of crystal 1 layers is 7.5 Å, somewhat shorter than the distance (8.5 Å) in crystal 2.     

Calcium–Amidoborane–Ammine Complexes: Thermal Decomposition of Model Systems

Hydrocarbon‐soluble model systems for the calcium–amidoborane–ammine complex Ca(NH₂BH₃)₂ ? (NH₃)₂ were prepared and structurally characterized. The following complexes were obtained by the reaction of RNH₂BH₃ (R=H, Me, iPr, DIPP; DIPP=2,6‐diisopropylphenyl) with Ca(DIPP‐nacnac)(NH₂) ? (NH₃)₂ (DIPP‐nacnac=DIPP? NC(Me)CHC(Me)N? DIPP): Ca(DIPP‐nacnac)(NH₂BH₃) ? (NH₃)₂, Ca(DIPP‐nacnac)(NH₂BH₃) ? (NH₃)₃, Ca(DIPP‐nacnac)[NH(Me)BH₃] ? (NH₃)₂, Ca(DIPP‐nacnac)[NH(iPr)BH₃] ? (NH₃)₂, and Ca(DIPP‐nacnac)[NH(DIPP)BH₃] ? NH₃. The crystal structure of Ca(DIPP‐nacnac)(NH₂BH₃) ? (NH₃)₃ showed a NH₂BH₃^? unit that was fully embedded in a network of BH???HN interactions (range: 1.97(4)–2.39(4) Å) that were mainly found between NH₃ ligands and BH₃ groups. In addition, there were N? H???C interactions between NH₃ ligands and the central carbon atom in the ligand. Solutions of these calcium–amidoborane–ammine complexes in benzene were heated stepwise to 60 °C and thermally decomposed. The following main conclusions can be drawn: 1) Competing protonation of the DIPP‐nacnac anion by NH₃ was observed; 2) The NH₃ ligands were bound loosely to the Ca²⁺ ions and were partially eliminated upon heating. Crystal structures of [Ca(DIPP‐nacnac)(NH₂BH₃) ? (NH₃)]_∞, Ca(DIPP‐nacnac)(NH₂BH₃) ? (NH₃) ? (THF), and [Ca(DIPP‐nacnac){NH(iPr)BH₃}]₂ were obtained. 3) Independent of the nature of the substituent R in NH(R)BH₃, the formation of H₂ was observed at around 50 °C. 4) In all cases, the complex [Ca(DIPP‐nacnac)(NH₂)]₂ was formed as a major product of thermal decomposition, and its dimeric nature was confirmed by single‐crystal analysis. We proposed that thermal decomposition of calcium–amidoborane–ammine complexes goes through an intermediate calcium–hydride–ammine complex which eliminates hydrogen and [Ca(DIPP‐nacnac)(NH₂)]₂. It is likely that the formation of metal amides is also an important reaction pathway for the decomposition of metal–amidoborane–ammine complexes in the solid state.     

Synthesis, Characterization of Mixed Ligand Palladium(II) Complexes of Triphenylphosphine and Anilines and their Enzyme Inhibition Studies against β-glucuronidase. The Crystal Structure of trans-dichloro-(m-chloroaniline)(triphenylphosphine)palladium(II)

A number of palladium(II) complexes with Ph₃P and aromatic amines as ligands having the general formula [(Ph₃P)Pd(Ph₃P)(NH₂R)Cl₂] {where R = Ph (1), m-ClC₆H₄ (2), p-ClC₆H₅ (3)} and [Pd(CH₃NHPh)Cl₂] (4), have been synthesized and characterized by elemental analysis, IR, ¹H and ¹³C NMR. The X-ray crystal structure of [(Ph₃P)Pd(m-ClC₆H₄NH₂)Cl₂] · CH₂ Cl₂ (2) shows a distorted square planar environment around the Pd(II) ion with the P–Pd–N and Cl(1)–Pd–Cl(2) bond angles of 174.88(5)° and 176.77(2)° respectively. The complexes were screened for enzyme inhibition activity against β-glucuronidase and found to be active.     

Chemistry of oxovanadium(IV) bound to tetradentate ONNO donors: Influence of axial coordination on the V-O(1)bond

Chelating behaviour of some tetradenate ONNO donors derived fromq - aminobenzoylhydrazide and some diketones toward oxo-vanadium(IV) ion is reported. The donors react with oxometal cation depending on the pH of the reaction medium. The product containing the neutral keto and the binegative enol form of the donors have the formulae [VO(H₂L)(SO₄)] (at pH 3.0)(┘1) and [VO(L)(H₂O)] (at pH 6.0)(┘2) respectively [H₂L = (2-NH₂)C₆H₄CONH: C(R) (CH₂)_mC(R): NNH CO C₆H₄(2−NH₂); H₂L = H₂DA(R= CH₃,m = 0), H₂BA(R = C₆H₅,m = 0), H₂AA(R = CH₃,m = 2)]. Both (┘1) and (┘2) react with a neutral monodentate donor B(B = pyridine, aniline etc.) yielding mixed-ligand complexes [VO(L)(B)]. Influence of the axial coordination on the V-O₍₁₎ bond is discussed and a monomeric distorted octahedral donor environment for the oxovanadium(IV) ion has been suggested     

Synthesis and Dehydrogenation of Organic Salts of a Five-Membered B/N Anionic Chain,a Novel Ionic Liquid

We have synthesized the tetrabutylammonium ([Bu₄N]⁺), tetraethylammonium ([Et₄N]⁺), guanidinium ([C(NH₂)₃]⁺), and methylguanidinium ([C(N₃H₅CH₃)]⁺) salts of the [BH₃(NH₂BH₂)₂H]⁻ anion, a five-membered B/N anionic chain, in high yields by the metathesis reactions of Na[BH₃(NH₂BH₂)₂H] with the corresponding halides and characterized them by NMR (¹¹B, ¹¹B{¹H}, ¹H, ¹H{¹¹B}, ¹³C), IR, elemental analysis, TGA-DSC, and TGA-MS. These complexes behave like ionic liquids (ILs), in which the melting point of the [Bu₄N][BH₃(NH₂BH₂)₂H] is the lowest (−51 °C). The dehydrogenation of these ILs have been studied through the thermal decomposition and catalytic hydrolysis in aqueous solution using the noble or non-noble metals or their salts as catalysts, and the results indicate that these ILs of five-membered B/N anionic chain are promising hydrogen storage materials.