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A study was undertaken to analyze the dinitrogen complex of zirconium [P2N2]Zr(mu-eta2-N2)Zr[P2N2] wherein P2N2 = PhP(CH2SiMe2NSiMe2CH2)2PPh reacted with 1-4 atm of H2 in toluene solution to form the [P2N2]Zr(mu-eta2-N2H)(mu-H)Zr[P2N2] (2) having an N-H bond and a bridging hydride. Results of the neutron studies and density functional theory revealed that the dinuclear dihydrogen complex, [P2N2]Zr(mu-eta2-N2)(mu-eta2-H2)Zr[P2N2], was an artifact of the X-ray analysis while solution 2 was identical to the solid-state structure.

A study was conducted to analyze the properties of crystalline N-methylacetamide (NMA). The spectra of the isotopic derivatives of NMA were obtained at six temperatures in the range 20-150 K using a filter difference spectrometer. Experimental results indicated that the temperature dependence of the intensities of the librations of the methyl groups in NMA supported no indication for a possible methyl-methyl coupling.

Nuclear magnetic resonance (NMR) spectra were recorded to examine the fluxionality of the bis(dihydrogen) complex RuH2(H2)2(PCy3)2 (1). Results indicated that 1 remained fluxional at all temperatures but the presence of CDCl3 necessary for its solubilization induces its transformation into RuHCl(H2)2(PCy3)2 and RuH2Cl2(PCy3)2 (4). A fluxional process was shown by 4 attributed to the interconversion between two symmetrical isomers. The fluxionality of the dihydrogen-hydride system was faster compared to results obtained by NMR studies of dihydrogen ligands.

A study was conducted to analyze the structure and energetics of chloroform binding sites in NaY zeolite using vibrational spectroscopy and energy-minimization computations. The binding sites were also examined by the Monte Carlo packing procedure. A closed-cycle He refrigerator was utilized to obtain the inelastic neutron scattering spectrum. Experimental results indicated that the H atoms of chloroform molecules influence hydrogen bonding with the framework oxygens.

Vibrational data, including IR, Raman and inelastic neutron scattering, was used to report the complex trans-W(CO)sub3(PCysub3)sub2(etasuper2-Hsub2) (1) and its HD and Dsub2 isotopomers. This supported the established etasuper2-bonding mode for the Hsub2 ligand. The calculated equilibrium isotope effect (EIE) was compared to experimental data for the binding of Hsub2 or Dsub2 to Cr(CO)sub3(PCysub3)sub2.

Reduction of MoCl5 in THF under suitable conditions with diphosphine ligands gives bis(dinitrogen)molybdenum complexes. 1H NMR spectroscopy of the 16-electron complexes obtained from the reaction between ethylacetate and the bis(dinitrogen) molybdenum complexes show an agostic Mo...H-C interaction between molybdenum and an ortho aryl hydrogen atom. IR, NMR and neutron scattering spectroscopies reveal the existence of eta2-H2 coordination in the adducts, formed between the 16-electron complexes and small molecules such as H2, N2 and SO2, with normal H-H distance. The normal H-H distance reveals the existence of a flat reaction coordinate for H2 cleavage.

Different techniques help in the preparation of various transition metal dihydrogen complexes Cr(CO)(3)(PR3)(2) (eta (super 2)-H(2)) (R=cy, Pr(super i)). X-ray crystallography and several other techniques are used for the characterization of these complexes. Cr(CO)(3) (PPr(3) (super i)(2) CH(2)) is the most unstable separable H(2) complex which has the shortest ligated H-H bond.

An economical source of hydrogen forms a metal hydride under wild conditions when the hydrogen is split heterolytically. The splitting is categorized by the presence of molecular H2 to be Bronsted-acidic. Coordinated H2 is known to quickly dissociate, disallowing the intracellular molecular rearrangement in d octahedra. Hydrogen binds with five-coordinate substructures, varying in equilibrium constants. The varying lengths of the bonding H2 are caused by a reduction in the strength of the sigma bond. The reducing power of the bonding fragments also vary.

The raction coordinate for hydrogen activation by transition metal centers is studied. The synthesis and characterization of derivatives of Mo(Co)(R2PC2H4PR2)2 and their reactions with H2, N2 and SO2 are also investigated. Results reveal that the reaction lacks an elongated H-H bond length with a dihydride tautomer despite the nearness of H2 to the cleavage. This finding indicate that the reaction coordinate for the oxidative addition of H2 is flat until the relatively precipitous cleavage of the H2.

The barrier to rotation of the complexes (MH(eta2-H2)PP3)1+, where M = Fe or Ru and which are crystallized as BPh4 salts, is investigated to derive evidence for the intensity of the back-bonding interaction. Results show that Ru's binding strength for the dihydrogen ligand is not consistent with its expected order in the periodic table. This is the result of the better back-donation properties of the Fe center as compared to Ru.

We report fully coupled quantum six-dimensional (6D) calculations of the translation-rotation (T-R) energy levels of CH4 molecule inside the small dodecahedral (512) and large tetracaidecahedral (51262) cages of the structure I clathrate hydrate. The quantum dynamics of the three translational and three rotational degrees of freedom of CH4 are treated rigorously, while the guest molecule and the host cavities are taken to be rigid. The matrix of the full 6D T-R Hamiltonian is diagonalized in the product basis of contracted translational and angular basis functions, generated by solving two reduced-dimension (3D) eigenvalue problems. A pairwise additive CH4-cage 6D potential energy surface (PES) is employed, constructed using the anisotropic CH4[Single_Bond]H2O pair potential which was utilized previously in the molecular dynamics simulations of methane hydrate. Our calculations elucidate the key features of the T-R energy level structure of the nanoconfined CH4. The rotational levels of methane exhibit an elaborate pattern of splittings caused by the angular anisotropy of the environment; the splitting patterns are identical for both types of cages. Translationally excited T-R states in the small cage are assigned in terms of the quantum numbers n and l of the 3D isotropic harmonic oscillator and those in the large cage using the Cartesian quantum numbers. Extensive comparison is made with the data from the inelastic neutron scattering studies of methane hydrate, allowing an assessment of the accuracy of the 6D PES employed. [ABSTRACT FROM AUTHOR]

The inelastic neutron scattering data on the rotational and vibrational transitions of the dihydrogen ligand in Tp(super Me2)RhH2(eta2-H2) provided information on its coordinated dihydrogen rotational barrier. The determined barrier for the rotation of the H2 ligand was 0.56(2) kcal/mol with the H-H distance of 0.94 angstroms. The values reflected the stability of the dihydrogen complex arising from the strong and weak M-H and H-H interactions, respectively, which lowered the H2 rotational barrier.

A novel approach for targeting zeolite-like metal-organic frameworks (ZMOFs) that utilizes metal-organic cubes and are regarded as double four-membered rings (d4Rs) and are composite building units (BUs) in traditional inorganic zeolites are reported. The implimentation of the new method is demonstrated by two ZMOFs with ACO and AST zeolite-like topologies constructed from d4R BUs exclusively held together by hydrogen bonds.

Zeolite-like metal-organic frameworks (ZMOFs) are anionic, have exchangeable extra-framework cations, and are constructed with a variety of organic linkers. Direct contact of the sorbed hydrogen with the exchangeable cations is not possible in the explored systems, as they retain their form as aqua complexes.

Hydrogen-sorption studies are carried out for the catenation isomer pairs of PCN-6 and PCN-6'. The analysis of isosteric heats of adsorption has shown that catenated PCN-6 and noncatenated PCN-6' have similar hydrogen-adsorption enthalpies at low coverage.

Single crystal neutron diffraction data for a sample of enolized 3,4-diacetyl-2,5-hexanedione at five temperature between 20 and 298 K was collected to characterize the temperature-dependent behavior of the short, strong, intramolecular hydrogen bond. The results obtained from the topological analysis of short intermolecular C-H...O contacts revealed significant closed-shell interaction that influenced the crystal structure, while the hydrogen bond is found to have both covalent and electrostatic character.

Study is conducted to show that a porous hybrid inorganic/organic material, Na[Ni.sub.3](OH)[(SIP).sub.2] [SIP=5-sulfoisophthalate] (1) strongly binds molecular hydrogen at coordinatively unsaturated metal sites. A combination of [H.sub.2] sorption isotherms, temperature programmed desorption, and inelastic neutron scattering spectroscopy show the existence of a significant number of such strong binding sites in (1) along with other sites where hydrogen is more weakly physisorbed.

The hindered rotor transitions of H2 adsorbed in the chemically related and prototypical porous metal-organic frameworks IRMOF-1, IRMOF-8, IRMOF-11, and MOF-177 are studied. The sites on the organic link have lower binding energies, but a much greater capacity for increases in H2 loading, which demonstrates their importance for hydrogen uptake by these materials.