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The mono(acetylacetonato) complexes [MCl(O,O'-acac) ([[eta].sup.6]-arene)] (M = Ru, Os, arene = [C.sub.6][H.sub.6], 1,3,5-[C.sub.6][H.sub.3][Me.sub.3], [C.sub.6][Me.sub.6]; M = Os, arene = 1,2-[C.sub.6][H.sub.3][Me.sub.2], 1,2,3-[C.sub.6][H.sub.3] [Me.sub.3]), which are formed from [[M[Cl.sub.2] ([[eta.sup.6]-arene)].sub.2] and thallium or sodium acetylacetonate, react with thallium acetylacetonate to give bis(acetylacetonato) complexes [M(O,O'-acac)([[eta].sup.1]-acac)([[eta].sup.6]-arene)]. The [[eta].sup.1]-acac ligand is bound through the [gamma]-carbon atom for M = Ru, Os, arene = [C.sub.6][H.sub.6]; M = Os, arene = 1,2-[C.sub.6][H.sub.4][Me.sub.2], 1,2,3-[C.sub.6][H.sub.3][Me.sub.3] and through a keto-oxygen atom for M = Ru, Os, arene = 1,3,5-[C.sub.6] [H.sub.3][Me.sub.3], [C.sub.6][Me.sub.6], the difference being attributed to a combination of steric and electronic effects. Cationic ruthenium(II) derivatives [Ru(L)(O,O'-acac)([[eta].sup.6]-arene]+ (arene = [C.sub.6][H.sub.6], 1,3,5-[C.sub.6][H.sub.3][Me.sub.3], [C.sub.6][Me.sub.6]; L = DMSO, MeCN, py, P[Ph.sub.3]) and [Ru(CO) (O,O-acac)([[eta].sup.6]-arene]+ (arene = 1,3,5-[C.sub.6][H.sub.3] [Me.sub.3],[C.sub.6][Me.sub.6]), and neutral osmium(II) [[eta].sup.1]-acetato derivatives [Os([[eta].sup.1]-OAc) (O,O'-acac) ([eta].sup.6]-arene)] (arene = [C.sub.6][H.sub.6], 1,2-[C.sub.6] [H.sub.4][Me.sub.2], 1,2,3-[C.sub.6][H.sub.3][Me.sub.3], 1,3, 5-[C.sub.6][H.sub.3][Me.sub.3], [C.sub.6][Me.sub.6]) are also described. The molecular structures of the following complexes have been determined by X-ray crystallography: [Os(O,O'-acac) ([[eta].sup.1]-C-acac)([[eta].sup.6]-1,2-[C.sub.6][H.sub.4] [Me.sub.2])], triclinic, space group P [bar]1 (No. 2), a = 9.922(2), b = 9.974(2), and c = 11.001(2) [Angstrom], [alpha] = 68.33(1), [beta] = 64.18(1), and [gamma] = 62.38(1)[degrees], V = 849.0(3) [Angstrom], Z = 2; [Os(O,O'-acac)([[eta].sup.1]-O-acac)([[eta].sup.6]-1,3, 5-[C.sub.6][H.sub.3][Me.sub.3])], monoclinic, space group C2/c (No. 15), a = 16.032(4), b = 11.989(3), and c = [2.sub.1].562(7) [Angstrom], [beta]= 108.91(2)[degrees], V = 3921(2) [Angstrom], Z = 8; [Os([[eta].sup.1]-OAc)(O,O'-acac)([[eta].sup.6]-[C.sub.6][H.sub.6])], triclinic, space group P [bar]1 (No. 2), a = 8.368(4), b = 8.402(4), and c = 11.008(4) [Angstrom], [alpha] = 71.68(3), [beta] = 69.35(3), and [gamma] = 69.77(3)[degrees], V = 663.0(6) [[Angstom].sup.3] Z = 2. Key words: arene-ruthenium, arene-osmium, acetylacetone, crystal structures.

Research has been conducted on the mer-M(H) (sub)3 (NO)L (sub)2 (M = Ru, Os) molecules. The characterization of these molecules has been carried out.

MO2 dioxide molecules are important products of an experiment where laser-ablated rhenium, osmium and ruthenium atoms reacted with O2 in excess neon and argon during condensation.

Research has been conducted on the reaction of cis-[M(bpy) (sub)2 Cl (sub)2] and Os(II) with triazine. The formation of dinuclear complexes as a result of this reaction is described.

Research has been conducted on the Ru(II) and Os(II) complexes with a polyphosphine/cumulene spacer. The synthesis, redox characteristics, electronic interactions and X-ray photoelectron spectroscopic study are described.

The article discusses a new approach to the synthesis of mixed-metal ligand-bridged nuclear complexes. The technique to form rigidly linked [ML (sub)2-(rigid spacer)-M'L (sub)2] compounds is described.

Research was conducted to examine the inner-sphere cluster formation by (Ru(NH3)5H2O)3+ or (Os(NH3)5H2O)3+ in combination with (M(CN)6)4- (M = Fe, Ru, or Os). The electrochemical behavior of the multinuclear centers in close proximity was also investigated. Results demonstrate that when acid is present to eliminate the adverse effect of internal proton transfer, the rate increase is only a factor of 1.5 or so while in the case of protonated anion about cation, the rate increase is a factor of 3.3. Findings provide insight into the stabilization of (M(CN)6)4- relative to (M(CN)6)3- by (M'(NH3)5)3+ and the stabilization by (M(CN)6)4- of (M'(NH3)5)3+ relative to (M'(NH3)5)2+.

A study was conducted to explore the design and construction of a molecular level electronic set, a set of molecular-level systems capable of performing functions which mimic those of macroscopic components in electronic devices. Nine rodlike compounds of nanometric dimension of the general formula [M(bpy)3-(ph)(sub n)-M'(bpy)3]4+ (M = M' = Ru(II); M = M' = Os(II); M = Ru(II), M' = Os(II); bpy = 2,2'-bipyridine; ph = 1,4-phenylene; n = 3,5,7; the central phenylene unit bears two alkyl chains for solubility reasons). Experimental methods, results and conclusions are discussed.

The relationship of energy-transfer rates and spectroscopic character in the double-complex salts (M(bpy)3)2(Cr(CN)6)Cl.8H2O, where M2+ = Ru2+, Os2+; bpy = 2.12'-bipyridine, has been investigated. The results showed that the luminescence from 3CT state of (M(bpy)3)2+ is partially quenched by (Cr(CN)6)3- at 77 degrees Kelvin and room temperature. The quenching is attributed to intermolecular excitation energy transfer from 3CT state of (M(bpy)3)2+ to the 2Eg state of (Cr(CN)6)3-.

The reduction-oxidation properties of some ruthenium and osmium complexes were investigated to determine the unusual coordination mode of thiosemicarbazone ligand. Thiosemicarbazones of benzaldehyde and two para substituted benzaldehydes were used to synthesize ruthenium and osmium compounds as well as characterize their structure. Empirical results showed that steric bulk of triphenylphosphine is not a factor in the observed unusual coordination mode of the benzaldehyde thiosemicarbazone ligands.

A study was conducted relating to the investigation of the degree and mechanism of electronic interaction between two redox active metal centers linked by a redox-active bridging ligand of well-defined structure. Specifically, this experiment reports the investigation into the effects of electronic interactions in homo- and heteronuclear ruthenium and osmium bisbipyridyl fragments bridged by O,N-coordination to 1,4-dihydroxy-2,5-bis(pyrazol-1'-yl)benzene (p-L).

A study was conducted on the electrochemistry at very positive potentials in liquid SO2 of RuII and OsII dendritic polynuclear complexes and of several of their lower-nuclearity analogues. The experiments resulted in the observation of several metal- and ligand-centered oxidations which were previously inaccessible. The findings also suggest that the redox properties can also be employed as a powerful tool for the chemical characterization of large and highly charged supermolecules.

A model was developed to analyze and define the properties of an energy transfer from luminescent porous silicon (p-Si) to adsorbed osmium(II) and ruthenium(II) polypyridyl complex compounds. The complex's surface adsorption on p-Si wafers quenched the emission. Facile energy transfer shifts from the surface to Ru(II) and Os(II) complexes. Such transfer is faster and more efficient for Os(II) than for Ru(II).

The protonation of corresponding monocationic hydrides yielded the dicationic dihydrogen complexes (Os(H2)(PR3)2(bpy)(CO))2+ (PR3 = PPh3, PMePh2), (Os(H2)(PPh3)2(phen)(CO))2+ and (Ru(H2)(PPh3)2(bpy)(CO))2+. The H2 ligand is strongly bound to the metal center, without any exchange with D2 over a number of weeks. The complex (Os(H2)(PR3)2(bpy)(CO))2+ is very stable in solution at room temperature, while the ruthenium analogue (Ru(H2)(PPh3)2(bpy)(CO))2+ is relatively stable at temperatures below 245 K, although it decomposes in solution at room temperature.

The investigation and synthesization of a series of new Ru(II) complexes containing the carboxylatopyridine ligand moiety were conducted using single-crystal X-ray diffraction, nuclear magnetic resonance, electrospray mass spectrometry, cyclic voltammetry, absorption and emission spectroscopy. Results reveal a general correlation of the electrochemical properties and the number of carboxylate groups per complex.

The electrochemistry of a series of complexes with one or more Cp*Ru+, CpRu+ or CpOs+ fragments (Cp=cyclopentadienyl; Cp*=pentamethylcyclopentadienyl) attached to an oligothiophene pi-system, was investigated. Oxidation of the complexes occurred on the uncomplexed thiophene rings while reduction occurred on the metal. The bound thiophene ring was transformed into a (Cp/Cp*M(thiophene))+ unit and removed from conjugation with the remaining uncomplexed rings.

Two-dimensional NMR spectroscopy was employed to investigate the kinetics of coupled two electron/halide transfer reactions between (Cp2MX)+ and Cp2M where M = Ru,Os and X = Cl,Br in CD3CN at 298 K. The results demonstrated a strong dependence of the exchange rate on the identity of the halide atom on the order of I > Br > Cl and Ru > Os. In addition, the reactant state free energy ordering was found to be Cl < Br < I.

The synthesis and characterization of bimetallic complexes (tpy)(M)(tpp)(RuCl3) (PF6) and (tpy)(M)(tpp)Ru(tpp) (PF6)4, where tpy = 2,2':6',2'-terpyridine; tpp = 2,34,5,6-tetrakis(2-pyridyl)pyrazine; M = RuII or OsII, are presented. The scheme involves a building block approach starting at the tpy end of the molecule, with the components being added in a sequential series of synthetic steps. The complex systems were found to possess long-lived excited states at room temperature with lifetimes of ca. 100 ns.

Single-crystal X-ray studies help determine the structure of Rb3Os2Br9, a confacial diosmium nonahalide. The internal geometry of this 10 d-electron system agrees with the sigma character of metal-metal interactions. A comparison of SCF-X(alpha)-SW calculations for (Os2Br9)(2-) and (Ru2Br9)(3-) supports high metal-metal interactions in Rb species. Optical spectroscopic studies of (Os2Br9)(3-) and (Ru2Br9)(3-) reveal that both include an electron-exchange term to the order of 8000 per cm.

Phenylene spacers connect the Ru(tpy)(sub 2)(super 2+) complex, where tpy is 2,2':6', 2'-terpyridine, and Os(tpy)(sub 2)(super 2+) binding blocks to produce rigid rod-like Ru(II)/Os(II) terpyridine-type complexes. The two building units exhibit slightly different absorption spectra in the dinuclear compounds. Electrochemical measurements of redox potentials reveal metal-metal and ligand-ligand interactions. Time-resolved luminescence spectroscopic analysis of energy transfer reactions shows that electron exchange through the phenylene linker facilitates energy transfer from the Ru-unit to the Os-unit.

Luminescence and UV absorption of specific dinuclear complexes comprise osmium(II) and ruthenium(II)terpyridine type chromophores. The Ru yields Os energy transfer step exothermically, which corresponded with an exchange-type mechanism. A rigid biocyclometalating ligand bridged the two metal centers in the dinuclear complex.

Studies of polynuclear Os(II)/Ru(II) polypyridine complex luminescence behavior reveals a decanuclear complex with six Os2+ and four Ru2+ metal ions. In compounds possessing both components, only the Os-based luminescence is seen in the 850 - 1000 nm spectral region. The intercomponent energy transfer in the polynuclear metal complexes may lead to supramolecular structures with controlled energy migration patterns.

The homobimetallic Os(II) complexes of the type (((bpy)2Os)2(BL))4+, where bpy = 2-2'-bipyridine and BL = bridging ligand, were synthesized and characterized. The polyazine compounds 2, 3-bis(2-pyridyl)quinoxaline, 2,3-bis(2-pyridyl)pyrazine and 2, 3-bis(2-pyridyl)benzoquinoxaline were used as bridging ligands in the synthesis. Spectroscopic and electrochemical analyses show that adding a second metal center to the (Os(bpy)2(BLT))2+ parent specie would result in the shifting of the metal-to-ligand charge-transfer absorption maxima to lower energies and a decrease in the bridging-ligand-based reduction potential.

A study was done on the syntheses, absorption spectra, luminescence properties and electrochemical behavior of supramolecular Ru and/or Os complexes of tris(bipyridine) bridging ligands. All the complexes display very intense, ligand centered absorption bands in the UV region and moderately intense metal-to-ligand charge-transfer bands in the visible. Luminescence data show that electronic energy transfer takes place from the Ru-based to the Os-based components.

The synthesis, electrochemistry and absorption spectra of the complexes (bpy)2M(dpt-cy'-dpt)M(bpy)2(super 4+) and (bpy)2M(dpt-cy')2+ (M = Ru2+, Os2+; bpy = 2,2'-bipyridine; dpt-cy'-dpt = trans-1,4-cyclohexanebis(N4- 3,5-bis(2-pyridyl)-1,2,4-triazole)amide; dpt-cy' = N4-cyclohexane-3,5-bis(2- pyridyl)-1,2,4-triazole) were reported. The potential applicability of the synthesized compounds as multielectron transfer catalysts can be attributed to the weak interaction of the metal units across the cyclohexyl-bridged spacer.

Ruthenium and osmium complexes containing tetra-2-pyridyl-1,4-pyrazine (tppz) ligands were prepared and characterized using electrochemical measurements and fast atom bombardment massspectrometry. The tppz ligands effectively functioned as bridges in forming dimetallic and trimetallic complexes. Results showed that the monometallic complexes were luminescent at both room and very low temperatures. In addition,varying metal-based oxidation potentials in the metal centers of dimetallic andtrimetallic complexes indicated the occurrence of metal to metal interactions along the tppz bridge.

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.

The compound (Ru2 chp4 2 pyz)(BF4)2 was prepared from the product of Ru2(chp)4Cl and Ag(CH3CN)4BF4 in dichloromethane dissolved in pyrazine. The compound (Ru2 chp4 py)(BF4).hexane.py was prepared from an analogous manner with pyrizine added to (Ru2 chp4 CH3CN)(BF4). Two diruthenium(II,III) tetrakis(mu-6-chloro-2-hydroxy)pyridinate units with Ru-Ru bond distances of 2.267(1) Angstrom and one axially bridging pyz molecule with Ru(1)-N(pyz) distances of 2.275(5) Angstrom constitute the first compound. Both compounds exhibited similar magnetic behavior and Curie-Weiss behavior.

The addition of either catechol, 3, 5-di-tert-butylcatecholate or tetrachlorocatechol to Os(bipyridine)Cl3 in the presence of base forms the corresponding bis(catecholato)(bpy)Os(IV) compounds. The spectral and electrochemical measurements show that the charge distribution of the derived quinone complex resembles that of either Ru or Os series. Complexes at the extreme sides of the five-membered redox series feature localized electronic structures while those at the center exhibit different charge distributions.

The reaction of M(TPrPC)(CO), where M = Os and Ru, with the free-base porphycene in diethylene glycol monomethyl ether or decalin produced the osmium and ruthenium porphycene complexes M(TPrPC)(CO). A single strong C-triple bond-O stretching band in the IR spectrum was found at 1893 cm(super -1) for Os(TPrPC)(CO) and at 1937 cm(super -1) for Ru(TPrPC)(CO). The study revealed that the porphycene can coordinate with the osmium and ruthenium ions despite its smaller cavity than that of porphyrin. Furthermore, the Ru and Os porphycene complexes were similar to their porphyrin analogues.

The synthesis and structural characterization by NMR and X-ray analysis of various mononuclear, homodinuclear, and heterodinuclear complexes are described, along with the study of their absorption, electrochemical, and near-IR emission properties.

An unparalleled chemical transformation of 2-(2',6'-dimethylphenylazo)-4-methylphenol was observed upon its reaction with [M(PPh3)3X2] (M=Ru, Os; X=Cl, Br) whereby one methyl group from the phenyl ring of the arylazo fragment migrates to the metal center through oxidation to carbon mono-oxide.

A series of osmium polypyridyl complexes having various ground-state reduction potentials are synthesized and used to sensitize nanoporous titanium dioxide electrodes to solar illumination, the responses of which are compared with the behavior of their ruthenium analogues. The osmium complexes appear to be promising candidates for further optimization in operating photoelectrochemical cells for solar energy conversion applications.

The energy transfer in a rodlike dinuclear complex, (ttp)Ru(tpy-ph-bco-ph-tpy)Os(ttp)4+ (RuOs) was found to be unaffected both by temperature and state of the solvent. In this species, the coordination environment of both metals is composed of tpy-type tridentate ligands and the spacer is a ph-bco-ph fragment. The complex has a rigid, linear geometry and the metal-to-metal distance is fixed at 2.4 nm.

High-valent nitrido and amido complexes of ruthenium, osmium and chromium were investigated by electrospray tandem mass spectrometry. The results showed the molecular ion as the base peak with a minimal degree of fragmentation. The collision-induced dissociation of these complexes have been explained in terms of the intrinsic metal-ligand bond strengths.

The addition of a bromonium ion reagent to metal carbonyl cluster compounds readily afforded triruthenium and triosmium dodecacarbonyl ions. Structural characterization of these compounds indicated that the ruthenium derivative can be considered as an organometallic analogue of the bromonium ion of ethylene, while the osmium cation can be considered as the corresponding ion of cyclopropane.

The coordination chemistry of ruthenium and osmium thiolate complexes supports the integrity of the trigonal (M(SR)3)1+,0 cores. Trigonal bipyramidal structures, with the CH3CN and a thiolate ligand at the axial positions, characterize the compounds (M(SR)4(CH3CN)), where M = Ru or Os and RS = S-2,3,5,6-Me4C6H and S-2,4,6-i-Pr3C6H2. When reacted with HBF4 or HPF6 in CH3CN, these compounds give (M(SR)3(CH3CN)2(BF4)). A representative member has been characterized by single crystal X-ray analysis.

It has been possible to react laser-ablated osmium and ruthenium atoms with nitrogen molecules to create the diatomic and triatomic nitrides MN and NMN and many dinitrogen complexes. Osmium inserts into the dinitrogen bond on annealing in the cold matrix.

The synthesis and characterization of iron(II), ruthenium(II) and osmium(II) carbonyl derivatives of (1-methylimidazole)(5,10,15,20-tetraphenylporphyrinate) were conducted using single-crystal X-ray diffraction methods. This permits a comparative study of the six CO complexes that can be made from TPP, Fe/Ru/Os, 1-methylimidazole and pyridine. Results suggest an rms error between theory and experiment of 0.20 MHz for values that range from (+)1.0 to (1)0.40 MHz.