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The reaction between Ta(OEt)(sub 5) and 1,1,3,3-tetramethyl-1,3-disiloxanediol, (HOSiMe2OSiMe2OH), produces new siloxy complexes in which the dimeric nature of Ta(OEt)(sub 5) is maintained with both bridging ethoxide and disiloxanediolato bridges. The structural and spectroscopic characterization, catalytic properties and thermal transformations of these new complexes are discussed.

The rare-earth binding properties of two hydrophobic carbamoylmethylphosphine oxide (CMPO) ligands, the normal bidentate variety, a tridentate extractant and tributyl phosphate are evaluated. The results show that as the ionic radius of the lanthanide ion decreases, a pair of the carbamoylmethylphosphine ligands is able to completely solvate a bound metal ion thereby weakening the nitrate-metal interaction.

The series of compounds (o-[CH.sub.3][SC.sub.6][H.sub.4])[CH.sub.2] [EPh.sub.3] (E = Si (1), Ge (2), Sn (3), and Pb (4)) have been synthesized and characterized by NMR spectroscopy and by single crystal X-ray diffraction. Compounds 1 and 2 are isostructural with a triclinic crystal system and P-1 space group; however, morphotropic steps occur between Ge and Sn, and Sn and Pb. While the E-S distances in 1 and 2 are 3.985 and 3.974 [Angstrom], respectively, ~100% of the sum of the respective van der Waals (vdW) radii, there is a notable distortion from tetrahedral geometry about E. Compound 3 is also triclinic with P-1 symmetry, but has two molecules in the unit cell that demonstrate a distorted tetrahedral geometry and intramolecular Sn-S distances of 3.699 and 3.829 [Angstrom], 88% and 91% of the sum of the vdW radii. Compound 4 has a Pb-S distance of 3.953 [Angstrom] (91% of E vdW radii). The structure of the Grignard coupling product [[o-(SC[H.sub.3])[C.sub.6][H.sub.6]C[H.sub.2]].sub.2] is also reported. Key words: intramolecular self-assembly, silicon, germanium, tin, lead, sulfur.

Research has been conducted on the trinuclear copper-pyrazolato complexes. The synthesis, X-ray structure determination and characterization of these complexes have been carried out and their chemical interconversions and magnetic susceptibility have been investigated and are discussed.

Research has been conducted on the N-protected amino ketones. Results indicate that the reduction of these amino ketones can be carried out stereoselectively to produce syn- and anti-amino alcohol diastereomers.

We have reinvestigated the solid state structure of 1,l'-bis- (ferrocenyldimethylsilyl) ferrocenylene, [([[eta].sup.5]-FcSi[Me.sub.2][C.sub.5][H.sub.4]).sub.2], Fe, Fc = ([[eta].sup.5] -[C.sub.5][H.sub.5])Fe([[eta].sup.5]-[C.sub.5][H.sub.4]). Using a DSC technique we observed a reversible phase transition for this compound at 169(3)K with [DELTA]H = 1.1 kJ/mol, and [DELTA]S = 6.54 J/mol K. A single crystal X-ray diffraction study has demonstrated that this phase change involves a transformation from a high temperature phase, space group P[2.sub.1]/c, Z = 2, to a triclinic low temperature phase, space group P[bar]1, Z = 4. The phase transition involves the loss of the molecular crystallographic center of symmetry and rotations about the terminal and central cyclopentadienyl ring pairs. The results are compared to those reported for ferrocene. Key words: solid state, phase transition, silyleneferrocenylene.

Research points out that the generation and trapping of alpha-lactams by nucleophiles can be carried out employing sodium hydride as a base. The reaction involves N-mesyloxyamide, sodium hydride and the nucleophile in THF. Data indicate that the reaction rate is markedly accelerated by ultrasonication

Resonant third harmonic generation and off-resonant electric field induced second harmonic generation measurements of ISQ and BSQ, two squarylium dyes, reveal the non-two-photon mechanism in these dyes to induce a negative value of the off-resonant third-order polarizability. These squaryliums, which exist as isomeric mixtures, are bond delocalized and a three-level model consisting of two distinct perturbation levels can explain their structure.

The importance of the first synthetic success in the Cu/PTCA/dien system is emphasized by the model which analyzes the data of the compound (Cu3(dien)3(PTCA)(H2O)3)(ClO4)2:2H2O. The elimination of the apically coordinated water in the compound stabilizes the chemically amounted problem. The ferromagnetic bridging geometry in the compound is also isolated.

A study was conducted to analyze the reactions of hydrazines with alpha-lactams. Nuclear magnetic resonance spectroscopy, infrared spectroscopy and X-ray structure were carried out to determine the regiochemistry of trapping of the alpha-lactam. Results indicated that monosubstituted hydrazines supporting bulky or conjugating groups reacted regiospecifically at the terminal nitrogen to generate 1-acylated-2-substituted products.

The Ph4E and Ph3E-E'R3 compounds have a packing coefficient of 0.73 and induce their individual molecular symmetry in the crystal lattice. The molecular symmetry of the compounds are not affected by the close packing of Ph4E homologues or by the introduction of a methyl group in the ortho position. The Ph3Sn-GeMe3 and Ph3Ge-SnMe3 complexes exhibit isostructural orthorhombic packing due to the presence of asymmetric Sn-Ge dumbbell. On the other hand, the hexaphenyl derivatives form unit cells with triclinic and monoclinic symmetries.

Two methods enable the preparation of the stable hexaalkyldiplumbane, (((Me3Si)3C)Me2Pb)2, with an yield of 10-20%. The trisyl group (Me3Si)3C helps stabilize Pb-Pb bonds in the system. Structural analysis of the hexaalkyldiplumbane by single-crystal X-ray studies reveals the Pb-Pb length as 2.968 Angstrom, the longest reported so for. Geometry around Pb atom exhibits significant distortion from the tetrahedral angle. Photolysis induces Pb-Pb bond cleavage, producing free radicals.

Crystal structure studies of the Me3GeSnPh3 and Ph3GeSnMe3 isomers show a difference in length of their respective Ge-Sn bonds. The shorter Ge-Sn bond of Me3GeSnPh3 is due to a closer energy match between an expanding lower energy system and contracting higher energy valence orbitals. This occurs when the heavier metal (Sn) is bonded to the electron-withdrawing (Ph) groups while the lighter metal (Ge) is bonded to the electron-donating (Me) group. The two isomers have the same conformation that is intermediate between the staggered and the eclipsed forms, similar to the Si2 and SiGe compounds which have a three-fold crystal axis.

Organotin(IV) compounds of the type (o-MeE-[C.sub.6][H.sub.4])C[H.sub.2]SnP[h.sub.3-n][Cl.sub.n] were synthesized and their properties were studied. The complexes show significant trigonal bipyramidal pentacoordination at tin due to intramolecular Sn-O and Sn-S interactions upon substitution of the phenyl groups by chloro groups.

The synthesis, isolation, characterization and unprecedented ring-opening polymerization of 1-sila-3-metallacyclobutanes of the type (eta(super 5)-C5H4Fe)(CO)2CH2SiR2 are reported. It is shown that the formation of the metallacycles results from an initial metalation of the cyclopentadienyl ring followed by a ring-closing salt elimination reaction.

A novel method for the synthesis of furanophanes is proposed which might be applicable to all dienylisobenzo furanes irrespective of how they are generated. To ascertain if chromium has a unique role, non-chromium based methods were tested for the generation of dienyl-isobenzofuran intermediates.

Research is presented of the treatment of bimetallic precursors FpCH2SiR2SiR2CH2Fp (Fp=(eta5-C5H5)Fe(CO)2) by photochemical means to create stereospecific formation of 1,3 disilacyclobutanes.