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Different polycatenar pyrazole ligands (Ln) was used to prepare several new cis-[RhCl[(CO).sub.2](Ln)] complexes and obtain columnar liquid crystalline arrangements. The topology of the ligand plays an essential role to induce mesophase at room temperature from a nonmesogenic pyrazole only when it is symmetrically substituted with six decyloxy chains.

Research has been conducted on the silver salt metathesis. The results of the [{(HBpz (sub)3)Rh(PPh (sub)3)(mu-Cl) (sub)2} (sub)2 Ag]BF (sub)4 (Hpz= pyrazole) reaction with silver salts which produces heterotrinuclear compounds are presented.

Research has been conducted on the reactions of rhodium(I) bis(mu-hydroxo) and bis(mu-methoxo) complexes. Results indicate that these reactions produce dinuclear rhodium complexes with mixed-bridging ligands.

Research has been conducted on the electrochemical behavior of the polymetalic compounds. The preparation of the polynuclear complexes with the bridging ligands which have a N-C-X (X=N, O, S) structural donor unit and the tetranuclear rhodium and iridium aggregates undergoing consecutive and reversible one-electron oxidation is described.

A study was conducted to determine the liquid crystal and nonlinear optical properties of rhodium (I) and iridium (I) complexes containing beta-diketonate or pyrazole ligands. X-ray single-crystal diffraction analysis show that some beta-diketonate compounds have two different polymorphs at the solid state. It was also found that the color and infrared spectra of the solid forms seem to be influenced by a different intermetallic-packing arrangement in the metal centers.

The homotetranuclear rhodium and iridium complexes (M4-(mu-pyS2)2(cod)4) behaved as encapsulating agents for the thallium(I) ion through the formation of cationic pentametallic species. Subtle electronic factors seemed to determine the Tl(I) encapsulation and involved an important structural reorganization driven not only by the multiple coordination possibilities of the doubly deprotonated 2,6-dimercaptopyridine ligands but also by the existence of d8-s2-d8 bonding interactions that contributed to the stabilization of the structure.

An experiment was conducted as part of studies into the chemistry of polynuclear complexes containing anionic ligands of the N-C-X type (where X = N, O and S). The study resulted in the first tetranuclear complex with two bridging N-C-S ligands exhibiting a mu-(1:2kappaS) coordination mode. The tetranuclear complex was found to undergo a change in the mu-(1kappaN, 2kappaS) coordination mode by replacement of the ancillary ligands.

The synthetic route for the preparation of the first disklike metallomesogens based on trinuclear (pyrazolato)gold complexes is described. The compounds all show mesogenic behavior that remain stable, at room temperature, for long periods of time. The solid-state crystal structure of these complexes and the X-ray-deduced supramolecular columnar arrangement of the mesophases can have a simple and clear relationship.

Dihydrogen complexes such as iridium, rhodium, osmium and ruthenium are parts of the process of homogeneous reduction of unsaturated substrates. The homogenous reduction of the unsaturated substrates takes place through hydrogenation, hydrogen-transfer and hydrosilylation reactions. Iridium, osmium and ruthenium derivatives are the complexes which act as homogeneous catalysts in tolerable condition.

N-methyl,N-phenyl-dithiocarbamate mononuclear rhodium(I) complexes was synthesized. Said complexes were able to behave as metalloligands for the controlled formation of binuclear dithiocarbamate-bridged species of the general formula (Rh2(mu-S2CN(Me)(Ph))(COD)L2)BF4. The dithiocarbamate group was observed to have a unique bridging eta2,eta2-(S,S') coordination mode even though in the mononuclear complexes, it coordinates as an S,S'-chelate ligand.

The first polyhydrido derivatives that contain donor ligands and which exhibit quantum mechanical exchange coupling between the hydrogen nuclei of the OsH3 group were prepared and characterized. Specifically, OsH6(P(sup i)Pr3)2 was reacted with 2,2-biimidazole (H2biim) to obtain the trihydrido OsH3(Hbiim)(P(sup i)Pr3)2. The latter's quantum mechanical exchange coupling was increased via reaction with the dimers (M(mu-OMe)(COD))2 to replace the acidic proton of the (Hbiim)- ligand with the metallic M(COD) where M = Rh,Ir. This resulted in the heterobimetallic complexes (P(sup i)Pr3)2H3Os(mu-biim)M(COD).

Ab initio calculations and nuclear magnetic resonance experiments were performed to investigate intramolecular hydrogen atom exchange in the transition metal complex OsH3(BH4)(PR3)2. Specifically, the H/H rearrangements of the type H(hydride)/H(hydride), H(sub bridging)(tetrahydroborate)/H(sub terminal)(tetrahydroborate) and H(hydride)/H(tetrahydroborate) were characterized. The theoretical and experimental results showed good agreement with each other.

The mononuclear complex (MCl(H2Bzimt)(cod)), where M = Rh, Ir, cod = 1,5 cyclooctadiene, and Bzimt = benzimidazole-2-thiol, is a precursor for synthesizing homo- and hetero-tetranuclear complexes such as (MM'(mu-Bzimt)(cod)2)2, which have S-coordinated ligands. The dinuclear and trinuclear complexes appear as intermediates during the process. The impact of steric and anisotropic effects is reflected in the chemical shift values of olefinic protons. The 1H-NMR spectra is carried out by selective decoupling, NOE, and H,H-COSY experiments.

The iridium and ruthenium complexes are reacted with poly(pyrazol)borato complexes to form heterodinuclear species with Co and Ni. The reaction is performed to investigate the coordination capacity of the iridium and ruthenium anions as tridentate ligands. New heterodinuclear complexes with pyrazolate and other mononegative bridging ligands are prepared and their molecular structures reported.

Simple syntheses of dinuclear complexes are provided by protonation of the methoxo groups in M(mu-OMe)(diolefin) 2 (M = Rh, Ir) with acidic proton-bearing binucleating ligands. Py(SH)2 reacts with (Rh mu-OMe cod )2 (cod = 1,5-cyclooctadiene) to form Rh4(mu-PyS2)2(cod)4, 1. Analogous preparations also give the diolefin rhodium complexes Rh4(mu-PyS2)2(nbd)4, 2, and Rh4(mu-PyS2)2(tfbb)4, 3, (nbd = norborna-2,5-diene, tfbb = tetrafluorobenzo 5,6 bicyclo 2.2.2 octa-2,5,7-triene). 1 is a tetranuclear complex with two 2,6-pyridinethiolate groups linking four metal centers.

The reaction of the dihydrido-olefin complex OsH2(eta2-CH2=CHEt)(CO)(P(super i)Pr3)2 with H2SiPh2 produced OsF3(SiHPh2)(CO)(P(super i)Pr3)2. The complex also reacted with H2GePh2, H2GePh3, and HGEt3 to form trihydrido-germyl derivatives, and with HSnPh3 and HSn(super n)Bu3 to form trihydrido-stannyl derivatives. The orientation of the ligand around the osmium atom was similar in all three products with the resulting structure described as a severely damaged pentagonal bipyramid. All compounds were fluxional in solution with the hydrido ligands exchanging positions.

A study has been conducted to describe carbon-carbon bond formation and subsequent carbon-hydrogen bond activation in reactions mediated by transition metal compounds such as bis(triisopropylphosphine)osmium complexes. NMR spectroscopy and X-ray diffraction techniques were used to obtain the spectra for the solutions at different temperatures. The results revealed that under mild conditions, carbon-carbon reactions are followed by carbon-hydrogen activation.

The monohydride OsHCL(CO)(PiPr3)2 reacts with HCL to form dihydrogen OsCl2(eta squared-H2)(CO)(PiPr3)2. A study of reactivity between hydridoosmium compounds and alkynes shows that specific organometallic compounds can be prepared by reacting these compounds with terminal alkynes when the right number of hydrido ligands and electronic properties of starting material are chosen. New carbene derivatives are produced in the reactions between OsCl2(eta squared-H2)(CO)(PiPr3)2 and terminal alkynes. X-ray crystallography has been used to determine the structure of the carbene derivatives.

Several rhodium and iridium substrates undergo arylation with (Ag(C6F5)) or (NBu4)(Ag(C6F5)(sub 2)) to form new anionic complexes which have been isolated as benzyltriphenylphosphonium or tetrabutylammonium salts. Single-crystal X-ray diffraction study shows that the crystals are triclinic having a unit cell of dimension. The rhodium atom is in a square-pyramidal environment, with two C6F5 (cis) and two P(OPh)3 ligands in the square plane and a Ag(PPh3) moiety in the apical position. Furthermore, the complex contains a Rh-Ag bond unsupported by covalent bridges.

Synthesis of Ir(II)Pd(II)Ir(II) and Ir(III)Pd(II)Ir(III) complexes involves oxidative stepwise addition reactions of trinuclear heterobridged iridium complexes with electrophilic reagents. These syntheses involve formation of metal-metal bonds and their subsequent cleavage. X-ray studies of ((Ir(mu-pz)(mu-S(t)Bu)I2(CO)(P(OMe)3))2Pd) reveal that trans addition of iodide atoms occurs at two distinct metallic centers and X-ray data support the flexibility of the pyrazolate-2-methyl-2-propanethiolate bridges.

IrH5(PPh3)2 reacts with carboxylic acids to produce hydridoiridium complexes of the type IrH2(eta squared-O2CR)(PPh3)2. Analysis of the reactions of these compounds with acetylenedicarboxylic dimethylester and HBF4 shows the alkylene insertion into one of two Ir-H bonds of the starting complexes, leading to the formation of hydrido-vinyl complexes. X-ray analysis helps the structural elucidation of a hydrido-bridged dinuclear complex (Ir2H2(PPh3)4(mu-H)2(mu-eta squared-O2CCH))BF4.

Multinuclear NMR experiments at different temperatures are conducted to analyze the dynamic behavior of (pentamethylcyclopentadienyl)iridium complexes with pyrazole ligands. Argentotropism accounts for the observed properties of these compounds. Heteronuclear coupling constants are related to the structure and dynamic properties of the complex. Line-shape analysis is used to calculate the kinetic parameters.

A dihydrogen derivative, (OsCl(eta 2-H2)(H2bim)(P-i-Pr3)2)Cl is obtained by the reaction of 2,2'-biimidazole (H2bim) with the dihydrido-dichloro complex OsH2Cl2(P-i-Pr3)2. X-ray investigation techniques are used in the determination of the molecular structure of the derivative. When the derivative is subjected to a triclinic space group, the addition of dichloromethane molecule crystallizes the derivative. Dihydrogen ligands are present in the derivative.

New hydride-carbyne and hydride-vinylcarbyne osmium(II) complexes were synthesized and characterized, and the molecular structure of complex2 was identified by X-ray crystallography. The crystals of 2 are orthorhombic, space group P212121, with unit cell dimensions a = 8.7490(3) angstroms, b = 15.4051(5) angstroms and c = 22.4257(8) angstroms. This synthesis involved the introduction of a derivative, unlike previously synthesized hydride-carbyne rhenium complexes that were developed by the reaction of rhenium polyhydrides and alkynes.

The binuclear complexes Rh2(mu-L)(diolefin)2 L = CA2-, DHBQ2-; diolefin = cycloocta-1,5-diene (cod), norborna-1,5-diene, tetrafluoro- (5,6)bicyclo(2.2.2)octa-2,5,7-triene were synthesized from the reaction of Rh2(mu-OMe)2(diolefin)2 with chloranilic acid (H2CA) or 2,5-dihydroxy-1,4-benzoquinone (H2DHBQ). The complex Rh4(mu-CA)2(cod)4 was also obtained and upon dissolution in a solvent and crystallization gave Rh2(mu-CA)(cod)2. The complexes were characterized by X-ray diffraction techniques.

The reactivity of the octahedral compounds MH(eta2-H2BH2)(CO)(PiPr3)2, where M = Os or Ru, toward electrophiles such as HBF4, Hpz, and R*CO2H, where pz = pyrazole and R* = (S)-CH(NaphOMe)Me, (R)-CH(OMe)Ph, (R)-C(CF3)(OMe)Ph, (S)-CHOC(double bond-O)CH2CH2, is reported. Results reveal that these octahedral compounds are catalyst precursors for hydrogen transfer reactions from 2-propanol to unsaturated organic substrates. These compounds are also precursors to six-coordinated hydridocarbonylosmium and -ruthenium compounds with the triisoprpopylphosphine ligand.

Binuclear complexes of rhodium and iridium were synthesized by using anionic, small-bite bridging ligands with a structural donor unit (N-C-X). Reactions of (Rh u-bzta CO PPh3)2 (bzta = benzothiazole-2-thiolate) with MCl2(cod) (M = Pd, Pt; cod = 1, 5-cyclooctadiene) yield the diamagnetic heterobinuclear compounds (Ph3P)M(u-bzta)2RhCl(CO) where M = Pt or Pd, MCl2(PPh3)2 and (Rh u-Cl cod)2. Crystallization of the compound (Ph3P)Pt(u-bzta)2RhCl(CO) with a CH2Cl2 molecule occurs in the triclinic space group P1.

The treatment of (Rh2 u-O2CCH3 4) with corresponding (alkyloxy)benzoic acids leads to the formation of (Rh2 u-O2CC6H4-4-OCnH2n+1 4) complexes that feature an ordered rectangular columnar mesophase. The presence of four-chain alkanoato compounds in the rhodium(II) complexes causes insufficient filling in the rigid core which leads to rectangular columnar mesophase formation. However, complexes that contain twelve paraffinic chains in the rigid core have a stabilized hexagonal mesophase. Furthermore, eight-chain-containing complexes initially have a rectangular mesophase that develops to a stable hexagonal mesophase at higher temperatures.