First synthesis and structural determination of a monomeric, unsolvated lithium amide, LiNH(2)

Dibenzoazepine hydrazine is a building block for N-alkene hybrid ligands: exploratory syntheses of complexes of Cu, Fe, and Li

The new hydrazine 5H-dibenzo[b,f]azepin-5-amine (2) reacts with P- and Si-electrophiles via deprotonation to afford P(III)-, P(V)-, and TMS-hydrazides 3-8 and with carbonyl electrophiles via acid-free condensation to the N-substituted hydrazones 9-12 that are potential N-alkene ligands. While β-ketohydrazone 9 and α-dihydrazone 10 react with [Mes(Cu)]4, [Cu(NCCCH3)4]2PF6, and FeCl2(THF)1.5 to afford complexes devoid of alkene interaction, [Cu(OTf)]2·C6H6 reacts with the α-keto hydrazone 11 or with N,N dimethyl-hydrazone 12 to form the neutral dimeric Cu(I) complex 18 with bridging Cu(I)-alkene interactions or the tetrahedral cationic complex 19 in which 12 binds as a bidentate hydrazone-alkene ligand, respectively. The surprising stability of the alkene coordination in complexes 18 and 19 prevents substitutions with, e.g., PPh3.

Ab initio study of spectroscopic properties and anharmonic force fields of MNH2 (M = Li, Na, K)

The spectroscopic properties and anharmonic force fields of NaNH₂ are studied in present work by DFT (B3P86 and B3PW91) and MP2 methods in combination with 6-311++G(2d, 2p) and 6-311++G(3df, 2pd) basis sets. The calculated equilibrium geometry, ground state rotational constants and centrifugal distortion constants of NaNH₂ at B3P86/6-311++G(3df, 2pd) theoretical level agree very well with the corresponding experimental values. Noteworthy, some spectroscopic constants and anharmonic force fields of NaNH₂, which have not been experimentally measured, are firstly predicted. In addition, the spectroscopic properties of KNH₂ are also predicted at the B3P86/6-311++G(3df, 2pd) level of theory. The influences of metal atoms on the equilibrium geometry, anharmonic constants, rotational constants, centrifugal distortion constants of MNH₂ (M = Li, Na, K) are analyzed intuitively. One can find that the metal atoms affect the rotational constants, part of centrifugal distortion constants (D_K, D_JK, H_K, and H_KJ), M-N bond length and some anharmonic constants of MNH₂.

Ab initio study of spectroscopic properties at anharmonic force fields of LiNH2

This work presents a systematic investigation of the spectroscopic properties at anharmonic force fields of ground electronic state ([Formula: see text]) of LiNH₂, which are calculated using second-order Møller-Plesset perturbation theory (MP2) and density functional theory (DFT) with hybrid GGA and meta-hybrid GGA (M06-2X) exchange-correlation functional. Two high angular momentum basis sets of 6-311+g (2d, p) and 6-311++g (3df, 2pd) are used. The equilibrium geometries, ground-state rotational constants, harmonic frequencies, and quartic and sextic centrifugal distortion constants of LiNH₂ are calculated and compared with corresponding experimental or theoretical data. The predicted accuracy of the calculated constants has been confirmed by analyzing the deviations with respect to experiment. In addition, the anharmonic constants, vibration-rotation interaction constants, force constants, and Coriolis coupling constants of LiNH₂ are firstly obtained. The infrared spectrum is predicted and together with the first prediction on the higher-order anharmonic constants contributes to a better understanding of the vibrational and rotational characteristics of LiNH₂, thus revealing its internal structure. Graphical abstract The IR spectra and the magnified IR spectra at 3500 cm^-1 in harmonic approximations of LiNH₂ using B3P86, M06-2X and MP2 methods combining with 6-311++g(3df,2pd).

Anharmonic Frequencies and Spectroscopic Constants of OAlOH and AlOH: Strong Bonding but Unhindered Motion

The astrophysical buildup of premineral nanocrystals from atoms to the smallest network-covalent solids will require observations of various small molecules containing the most common elements in minerals including aluminum and oxygen. The present work utilizes high-level quantum chemical quartic force field (QFF) approaches to produce anharmonic vibrational frequencies and spectroscopic constants for such species. The computed B_eff for the astrochemically known AlOH molecule at 15780.5 MHz is a mere 40 MHz above the experimental value implying that the B_eff for OAlOH at 5580.9 MHz is similarly accurate. The additional 7.31 D dipole moment in OAlOH implies that this molecule is a viable target for interstellar observation. Unlike the other anharmonic vibrational frequencies reported in this work, the Al-O-H bending frequencies in both AlOH and OAlOH are poorly described in the present QFF results. However, this failing actually highlights the fact that these bends are exceptionally floppy yet with counterintuitive exceedingly strong bonding. The Al-O bond energies are 128.2 and 107.2 kcal/mol, respective of AlOH and OAlOH, while the barriers to linearity are meager 16.6 and 380.7 cm^-1 (0.1 and 1.1 kcal/mol).

Additives in protic–hydridic hydrogen storage compounds: a molecular study

Listed model compounds having best dehydrogenation properties where ΔE_avg is the average hydrogen removal energy for the complete dehydrogenation.

Lithium amide (LiNH2) under pressure

Static high pressure lithium amide (LiNH(2)) crystal structures are predicted using evolutionary structure search methodologies and intuitive approaches. In the process, we explore the relationship of the structure and properties of solid LiNH(2) to its molecular monomer and dimer, as well as its valence-isoelectronic crystalline phases of methane, water, and ammonia all under pressure. A NaNH(2) (Fddd) structure type is found to be competitive for the ground state of LiNH(2) above 6 GPa with the P = 1 atm I4[overline] phase. Three novel phases emerge at 11 (P4[overline]2(1)m), 13 (P4(2)/ncm), and 46 GPa (P2(1)2(1)2(1)), still containing molecular amide anions, which begin to form N-H···N hydrogen bonds. The P2(1)2(1)2(1) phase remains stable over a wide pressure range. This phase and another Pmc2(1) structure found at 280 GPa have infinite ···(H)N···H···N(H)···H polymeric zigzag chains comprising symmetric N···H···N hydrogen bonds with one NH bond kept out of the chain, an interesting general feature found in many of our high pressure (>280 GPa) LiNH(2) structures, with analogies in high pressure H(2)O-ices. All the predicted low enthalpy LiNH(2) phases are calculated to be enthalpically stable with respect to their elements but resist metallization with increasing pressure up to several TPa. The possibility of Li sublattice melting in the intermediate pressure range structures is raised.

Density functional theory study on (LiNH2)n (n=1-5) clusters

Geometrical structures and relative stabilities of (LiNH(2))(n) (n = 1-5) clusters were studied using density functional theory (DFT) at the B3LYP/6-31G* and B3LYP/6-31++G* levels. The electronic structures, vibrational properties, N-H bond dissociation energies (BDE), thermodynamic properties, bond properties and ionization potentials were analyzed for the most stable isomers. The calculated results show that the Li-N and Li-Li bonds can be formed more easily than those of the Li-H or N-H bonds in the clusters, in which NH(2) is bound to the framework of Li atomic clusters with fused rings. The average binding energies for each LiNH(2) unit increase gradually from 142 kJ mol(-1) up to about 180 kJ mol(-1) with increasing n. Natural bond orbital (NBO) analysis suggests that the bonds between Li and NH(2) are of strong ionicity. Three-center-two-electron Li-N-Li bonding exists in the (LiNH(2))(2) dimer. The N-H BDE values indicate that the change in N-H BDE values from the monomer a1 to the singlet-state clusters is small. The N-H bonds in singlet state clusters are stable, while the N-H bonds in triplet clusters dissociate easily. A study of their thermodynamic properties suggests that monomer a1 forms clusters (b1, c1, d2 and e1) easily at low temperature, and clusters with fewer numbers of rings tend to transfer to ones with more rings at low temperature. E(g), E(HOMO) and E(av) decrease gradually, and become constant. Ring-like (LiNH(2))(3,4) clusters possess higher ionization energy (VIE) and E(g), but lower values of E(HOMO). Ring-like (LiNH(2))(3,4) clusters are more stable than other types. A comparison of structures and spectra between clusters and crystal showed that the NH(2) moiety in clusters has a structure and spectral features similar to those of the crystal.

The structural properties of amides and imides as hydrogen storage materials

We discuss crystal structure of amides and imides, which are focusing on promising hydrogen storage materials. They are ionic crystal with anion of (NH2)– or (NH)2– and cation of Li+, Na+, Mg2+, Ca2+, and so forth. We also discuss reaction mechanisms on hydrogen ab/desorption of amide/imide hydrogen storage materials.

Synthesis, structures, and kinetics of mixed-donor amido-amino-siloxo ligands from symmetrical diamidosilyl ether ligands via a retro-brook rearrangement

Deprotonation of the new (R = propyl, 3,5-Me(2)Ph) and previously prepared (R = 2,4,6-Me(3)Ph, 2,6-(i)Pr(2)Ph, 3,5-(CF(3))(2)Ph) symmetrical diamidosilyl ether ligand precursors {[RNHSiMe(2)](2)O} with 2 equiv of nBuLi in THF resulted in a new class of mixed-donor amido-amino-siloxo ligands of the form {RNLiSiMe(2)N(R)SiMe(2)OLi} (R= propyl (1c), 3,5-Me(2)Ph (2c), 2,4,6-Me(3)Ph (3c), 2,6-(i)Pr(2)Ph (4c), 3,5-(CF(3))(2)Ph (5c)) in one-step and high yield via a retro-Brook-type rearrangement mechanism. Ligands 1c, 3c, and 4c have been structurally characterized in the presence and absence of THF/ether donor solvents and exhibited a range of aggregated structures with ring-laddering, ring-stacking, and cubane motifs; higher-nuclearity clusters for base-free systems were observed for 1c and 4c. 1H, (7)Li, and selected (13)C{(1)H} NMR spectra in THF-d(8) and toluene-d(8) are described; the (7)Li data are indicative of intramolecular fluxional behavior as a function of temperature but do not shed light on the nuclearity of the salts in solution. Reaction kinetics were investigated by variable-temperature 1H NMR spectroscopy and showed that the rate of rearrangement reactions increases with decreasing steric hindrance and with increasing electron-donating ability of the R substituents, with tau(1/2) values ranging from 5.7 x 10(1) to 1.5 x 10(8) s for 2c and 5c, respectively.

Competition between Metal-Amido and Metal-Imido Chemistries in the Alkaline Earth Series: An Experimental and Theoretical Study of BaNH

The pure rotational spectrum of BaNH in its X(1)Sigma(+) ground electronic state has been recorded using millimeter/submillimeter direct absorption methods; data for the deuterium and barium 137 isotopomers have been measured as well. The molecules were produced by the reaction of ammonia or ND(3) and barium vapor in the presence of a dc discharge. Transitions arising from the ground vibrational state and the excited vibrational bending (01(1)0) and heavy atom stretching (100) modes were measured. The rotational spectrum indicates a linear structure, with B(0)(BaNH) = 7984.549 MHz and B(0)(BaND) = 7060.446 MHz. An r(m)((1)) structure has been determined, yielding r(BaN) = 2.077 +/- 0.002 Angstroms and r(NH) = 1.0116 +/- 0.0006 Angstroms. Density functional calculations using an extensive Slater-type basis set with inclusion of scalar relativistic effects gives geometrical parameters and vibrational frequencies for BaNH in excellent agreement with those determined by experiment. The molecular orbital and natural bond order analyses of the BaNH wave function show Ba-N pi bonds formed by electron donation from the formally filled N 2p orbitals of the imido group to the empty Ba 5d orbitals. The multiple bonding between Ba and N stabilizes the linear geometry and, along with the relative ease of oxidation of the Ba atom, favors formation of the metal-imido species over that of the metal-amido species that have been found from similar studies with Mg, Ca, and Sr atoms in this group.