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The ability of the beta-La2Mo2O9 cationic sublattice to distort as a semirigid framework of tilting [OLa3Mo) antitetrahedral units is studied through a mathematical analysis. It is proposed that the extra volume expansion, observed at the postulated Arthenius/Vogel-Tamman-Fulcher (VTF) transition, originates from such a tilting mechanism.

Chemistry of the group-4 pyrrolyl complexes bearing dianionic, tridentate ligands with reference to the chelating ligand dpma is described. Research demonstrates that transamination of dimethylamides with dihydrogen-dpma leads to protonation of two dimethylamides. Metal-pyrrolyl bonding, reactivity, and factors influencing functionality of d(sup)0 complexes are discused.

The complexes [[pyda.H].sub.2][[Co(pydc).sub.2]*[H.sub.2]O (I) and [[pyda* H].sub.2][[La.sub.2][(pydc).sub.4][([H.sub.2]O).sub.4]]*2[H.sub.2]O (II) were prepared from the complexation of a novel pyridine containing self-assembling system L[H.sub.2], ([[pyda*[H.sub.2]].sup.2+][[pydc].sup.2-]) (pyda = 2,6-pyridinediamine and pydc*[H.sub.2] = 2,6-pyridinedicarboxylic acid), with cobalt(II) and lanthanum(III) salts in 82% and 74% yields, respectively. The characterizations were performed using elemental analysis, ESI mass spectroscopy as well as [sup.1]H and [sup.13]C solution NMR spectroscopy, and X-ray crystallography. The crystal systems I and II are monoclinic and triclinic with space groups P[2.sub.1]/n and P[bar]1, respectively. Coordination number around each Co atom is six with distorted octahedral geometry, while coordination number around each La atom is nine with highly distorted tricapped trigonal prism geometry. The paramagnetic Co(II) and diamagnetic La(III) complexes show [sup.1]H NMR resonances of both anionic [[pydc].sup.2-] and cationic counter ion [[pyda*H].sup.+] in DMSO-[d.sub.6]. The complexation reactions of the complex I in aqueous solution were investigated by potentiometric pH titrations and the equilibrium constants for all major complexes formed are described. The results are presented in the form of distribution diagrams revealing the concentrations of individual complex species as a function of pH. The results revealed that at a pH range 4.0-4.5 the major complex species is [[(pyda*H)].sub.2][Co[(pydc).sub.2]]. Key words: self-assembly, X-ray crystal structure, Co(II) complex, La(III) complex, 2,6-pyridinedicarboxylic acid, 2,6-pyridinediamine, hydrogen bonding.

This article discusses recent advances related to binary and mixed hydrides that are formed by various metal groups encompassing main metals. Research describes new precursors for the design and fabrication of multilayer devices with special electrical and optical properties and transient molecules analysis.

The review presents the analysis and categorization of the localization and delocalization transition in ligand-bridged mixed-violence molecules. The transition-metal complexes with the important organic results are in the main focus of the article.

Results show that the pentacyano(L)ferrate(II) complexes behave differently in terms of stability in aqueous solution. However, they share the property of cyanide release. The stability of the different redox-active species of nitric oxide bound to the pentacyano fragment is also discussed.

The fragmentation patterns of cationic dinuclear iron chloride clusters reveal that the iron-chlorine bond strength in the iron chloride ions is dependent on structural aspects than the valency status of iron.

Research demonstrates that chiral bidentate mercury ligands can be prepared by reacting mercury cyanide and bis(trifluoromethyl)phosphane. Data indicate that yield of the compounds is quantitatively significant with 18 valence electron complexes exhibiting thermal stability.

Two approaches for the synthesis of transition-metal complexes containing bidentate trans-spanning tertiary phophine ligands, the preformed ligand startegy and the in situ ligand strategy, are described. Research reveals that the preformed ligand strategy is more successful than the other and the synthesized compounds exhibit unusual metal geometries.

Salen-group 13 ligands are derived by combining a diamine with 2 equivalents of salicyclaldehyde and are ideal for the equatorial coordination of transition metals and catalysis. The use of group 13 compounds is generally in combination with Salen-supported trnsition metal compounds.

Research discusses different methods to achieve nonmetallic properties of transition metal antimonides as exemplified by new Sb-rich compounds that contain titanium and transition metal M' = Zr, Hf, Nb, Mo. Data indicate that the metal sites of the compounds are occupied by M' and titanium atoms in a three-dimensional network of Sb atoms.

The ortho-para conversion rate of hydrogen molecules physisorbed on transition metal oxides was found to be substantially improved for selected values of the parameters. This new electron-nucleus resonant mechanism was proposed to interpret the observed accelerations of the conversion rate by an external magnetic field. The sensitivity of the magnetic field acceleration upon catalyst pretreatments may have significant practical applications in the selection and preparation of industrial catalysts.

A study was conducted to systematically investigate the occurrence of dihydrogen bonds in the complexes involving the main group elements. Structures featuring close H***H bonds in the complexes of LiH, BH3 and AlH3 with HF, H2O and NH3 were scrutinized. Structures of dimers of these complexes were also obtained to verify the existence of the dihydrogen bond. The dihydrogen bonded structures in the complexes of LiH, BH3 and AlH3 with HF, H2O and NH3 were found to be unstable. Other results are discussed.

X-ray and neutron diffraction studies of diammonium hexaaquairon(II) disulfate-d20 (FeTS) to ascertain its electron density have been undertaken. Results show that the electronic distribution around the iron atom is anisotropic because it has contributions from only two closely similar states. The structure of the 3d electron density around the iron atom agrees with data from spectroscopic measurements at very low temperatures. It has also been observed that donation occurs between the eg and t2g 3d orbitals.

The pKa values of five Fischer carbene complexes in acetonitrile have been measured. Fischer carbene complexes with one or several hydrogen atoms in the alpha-carbon are moderately acidic. Pure acetonitrile was used because the carbene complexes are stable in this solvent. Its polarity is large enough such that ion pairing does not pose a problem and pKa values up to 36 can be measured. Results show that the pKa values in pure acetonitrile are 10.2 units higher than in 50% MeCN-50% water. This is due to the weaker solvation of the hydrogen ion in pure acetonitrile.

Reactions between fullerenes and transition metal complexes and fullerenes are reviewed. These reactions generate different new compounds. The addition of metal to the olefinic C-C bonds at 6:6 ring junctions generate eta-squared-coordination complexes. Decreasing the level of fullerene creates fulleride salts while adding ligating groups to the fullerene produces a metal center connected to the fullerene. Meanwhile, solids can be formed when the fullerene and a metal complex are cocrystallized. Isolated fullerene complexes across the periodic table are reviewed.

Transition metal hydride complexes are interesting because of their value in homogeneous catalysis and of their spectroscopic properties. Examples of complexes with quantum mechanical exchange couplings are sandwich and half-sandwich trihydrides, sandwich dihydrides, and octahedral polyhydrides. These compounds do not have structural commonalities. Their similarity lies in the fact that they all have an exchange barrier for two hydrogens of approximately 40 kilo-joule per mole. Polyhydrides have a low barrier while dihydrogen compounds possess a high barrier.

Calculations on the complexes (Ag(NHCHNH))2 and (Ag(dmtp)(NO3))2 performed at RHF, DFT (B3LYP) and MP2 levels are discussed. It is shown that the hybrid RHF and DFT approaches can be applied to geometry optimization in studies of binuclear transitional metal complexes using a least a split valence basis set or quasirelativistic corrected pseudopotential basis set. The results also show good agreement with MP2 computations.

An experiment was conducted to determine the interaction of the distorted transition-metal cubic clusters [Bi4Co9(CO)16]2- and [Bi8Co14(CO)20]2- and analyze the configurations of the cluster compounds based upon a hexacapped M8 cube. A single-crystal X-ray diffraction was utilized to characterize the transition metal compounds. Results showed HOMO/LUMO region is slightly antibonding between the interstitial Co atoms and the surrounding Bi and peripheral Co Atoms but their rich electron contents contribute to the compounds' strong bonding to interstitial cobalt atoms.

An analysis was conducted regarding the formation of chain and large-ring polymeric transition metal complexes formed by the 'extended-reach' sulfur donor ligands N,N'-ethylenebis(pyrrolidine-2-thione) (EBPT) and N,N'-p-phenylenedimethylenebis(pyrrolidine-2-thione) (p-XBPT). The metal complexes were analyzed and characterized through the use of X-ray crystallography. Results showed that these metal complexes have formed chains, discrete 18-membered metallacylic rings, chains of rings and sheets of contiguous 52-membered rings.

A study was conducted on the synthesis and crystal structure determinations of Zr0.30ZrTe2 and MxZr2Te2As (M = Zr, Na) compounds. Rietveld refinements show that the sodium ions reside in the trigonal antiprismatic sites between the layers. Moreover, extended Huckel band calculations reveal that the [Zr2Te2As]1.16- layer should be a metallic conductor and that the [Zr2Te2As] layered compounds may function as electron-donating hosts.

The mechanism surrounding thermal and photochemical reactions of methylrhenium diperoxide was investigated through analysis of the formation of hydroperoxide in acetonitrile. It was found that the rates and equilibria of the MTO-H(sub 2)O(sub 2) system in CH(sub 3)CN were susceptible to the presence of water. Water was strongly indicated to have a direct involvement in the mechanism of peroxide interaction.

Broken-symmetry (BS) and single-determinant (SD) models were two effective computational approaches for the study of magnetic exchange interactions in large molecules. These density functional theory-based (DFT) models were discussed and tested effective for metal-radical interactions, metal-metal interactions mediated by inert organic bridges. The approach was also proven useful for the rationalization of magneto-structural correlations.

Variable-temperature (2-300K) SQUID susceptometry was utilized to analyze the magnetic properties of the tetranuclear complexes of TCNE, TCNQ, and TCNB. The spectral results revealed a mu4,eta(super)4-coordination of the TCNQ and TCNB. It was indicated that the Zero-field splitting field of the parameter D was directly proportional to the spin-orbit coupling constant of Ru. Furthermore, data revealed that the J and D value were strongly associated with the electronic and steric effects.

A novel method of synthesizing titanium nitride was developed through the use of the monomeric titanium(IV) azides reactive pathway. The design featured the introduction of N-donbor ligands into the coordinbation sphere to isolate monomeric derivatives. It was also confirmed that the use of amido groups and azide nitrogen moieties can be useful in preparing TiN precursors.

The pKa values for transition metal carbene complexes (CO2)5Cr=C(OMe)CH2CH3 (3-Et), (CO)5(Cr=C(OMe)CH2CH2CH3) (3-Bu) and (CO)5CR=C(OMe)CH(CH3)2 (3-Pr) in aqueous acetonitrile are reported as 12.62, 12.84 and 12.27 respectively. They are all more acidic than (CO5)Cr=C(OMe)CH3 (3-Me). In contrast to their thermodynamic acidities, 3-Et, E-Bu and 3-PR all exhibit greater rate constants than 3-Me. Other research observations are made. Kinetic reaction parameters are given together with data from spectrophotometer analysis.

Small heteronuclear coupling constants in transition metal complexes were measured through H-detected multinuclear NMR experiments. The absolute sign of the coupling constants was determined by relating the signs of the measured couplings to that of a one-bond proton-carbon coupling constant. By NMR spectroscopy, it was also realized that the conformation dependence of the scalar coupling constants affirms the rapid structural characterization of catalytically active organometallic complexes.