Os Complexes Research Articles

A New Tris(diphenylstannylene)triosmium Carbonyl Cluster Complex and Its Reactions with Pt(PBut3)2and Pt(PPh3)4

The reaction of Os3(CO)12 with Ph3SnH yielded the bimetallic Os−Sn cluster complexes Os3(CO)11(SnPh3)(μ-H) (16) and Os3(CO)9(μ-SnPh2)3 (17) in 20 and 21% yields, respectively. Compound 16 consists of an Os3 triangle with a terminal SnPh3 group on one of the Os atoms and a bridging hydrido ligand across one of the Os−Os bonds. Compound 17 consists of a central Os3 triangle with SnPh2 groups bridging each of the three Os−Os bonds. Pt(PBut3)2 reacts with compound 17 to afford Os3(CO)9[Pt(PBut3)](μ-SnPh2)3 (18), a Pt(PBut3) adduct of 17, in 29% yield by adding a Pt(PBut3) group across one of the Os−Sn bonds. The osmium and tin atoms lie in a plane, while the Pt(PBut3) group is displaced slightly out of that plane. Pt(PPh3)4 reacts with 17 to give the cluster complex Os3(CO)9[Pt(Ph)(PPh3)2](μ-SnPh2)2(μ3-SnPh) (19) in 21% yield by insertion of a Pt(PPh3)2 into one of the Sn−C bonds to one of the phenyl groups. The osmium and tin atoms are coplanar, and there is a Pt(Ph)(PPh3)2 group terminally bonded to one of ...

Theoretical studies on vibrational spectra of some mixed carbonyl-halide complexes of Osmium(II)

The vibrational spectra of Os(CO)62+ and some of its mixed carbonyl-halide complexes, cis-Os(CO)2X42−, fac-Os(CO)3X3− and Os(CO)5X+ (X=F, Cl, Br and I), have been systematically investigated by ab initio RHF and density functional B3LYP methods with LanL2DZ and SDD basis sets. The calculated vibrational frequencies of complexes Os(CO)62+, cis-Os(CO)2X42− and fac-Os(CO)3X3− are evaluated via comparison with the experimental values. In infrared frequency region, the C–O stretching vibrational frequencies calculated at B3LYP level with two basis sets are in good agreement with the observed values with deviations less than 5%. In the far-infrared region, the B3LYP/SDD method achieved the best results with deviations less than 9% for Os–X stretching and less than 8% for Os–C stretching vibrational frequencies. The vibrational frequencies for Os(CO)5X+ that have not been experimentally reported were predicted.

Fluorimetric determinations of nucleic acids using iron, osmium and samarium complexes of 4,7-diphenyl-1,10-phenanthroline

New sensitive, reliable and reproducible fluorimetric methods for determining microgram amounts of nucleic acids based on their reactions with Fe(II), Os(III) or Sm(III) complexes of 4,7-diphenyl-1,10-phenanthroline are proposed. Two complementary single stranded synthetic DNA sequences based on calf thymus as well as their hybridized double stranded were used. Nucleic acids were found to react instantaneously at room temperature in Tris–Cl buffer pH 7, with the investigated complexes resulting in decreasing their fluorescence emission. Two fluorescence peaks around 388 and 567 nm were obtained for the three complexes using excitation λ max of 280 nm and were used for this investigation. Linear calibration graphs in the range 1–6 μg/ml were obtained. Detection limits of 0.35–0.98 μg/ml were obtained. Using the calibration graphs for the synthetic dsDNA, relative standard deviations of 2.0–5.0% were obtained for analyzing DNA in the extraction products from calf thymus and human blood. Corresponding Recovery% of 80–114 were obtained. Student's t-values at 95% confidence level showed insignificant difference between the real and measured values. Results obtained by these methods were compared with the ethidium bromide method using the F-test and satisfactory results were obtained. The association constants and number of binding sites of synthetic ssDNA and dsDNA with the three complexes were estimated using Rosenthanl graphic method. The interaction mechanism was discussed and an intercalation mechanism was suggested for the binding reaction between nucleic acids and the three complexes.

An Osmabenzofuran from Reaction between Os(PhC⋮CPh)(CS)(PPh3)2 and Methyl Propiolate and the C-Protonation of this Compound to Form a Tethered Osmabenzene

Reaction between the diphenylacetylene complex Os(PhC⋮CPh)(CS)(PPh3)2 (1) and two molecules of HC⋮CCO2Me leads to a very stable, blue, osmabicylic complex with osmium at a bridgehead position. One way to consider this complex is as a metalla-aromatic molecule, viz., the osmabenzofuran Os[C7H2O(OMe-7)(CO2Me-4)(Ph-1)(Ph-2)](CS)(PPh3)2 (2). The bicyclic ring system is remarkably robust, and heating this compound in ethanol at reflux with aqueous HCl effects only a transesterification of the ester function in the six-membered ring (at the 4-position), forming Os[C7H2O(OMe-7)(CO2Et-4)(Ph-1)(Ph-2)](CS)(PPh3)2 (3). Reaction of Os[C7H2O(OMe-7)(CO2Me-4)(Ph-1)(Ph-2)](CS)(PPh3)2 (2) with pyridinium tribromide effects bromination in the five-membered ring of the osmabenzofuran at the 6-position to form Os[C7HO(OMe-7)(Br-6)(CO2Me-4)(Ph-1)(Ph-2)](CS)(PPh3)2 (4). Crystal structure determinations of 2, 3, and 4 confirm the osmabicyclic structure of each compound. Treatment of complex 2 with anhydrous trifluoroacetic acid...

Multisite Effects on Intervalence Charge Transfer in a Clusterlike Trinuclear Assembly Containing Ruthenium and Osmium

The intervalence charge transfer (IVCT) properties of the mixed-valence forms of the diastereoisomers of the dinuclear [[Ru(bpy)2](mu-HAT)[M(bpy)2]]5+ (M = Ru or Os) complexes and the trinuclear heterochiral [[Ru(bpy)2]2[Os(bpy)2](mu-HAT)]n+ (n = 7, 8; HAT = 1,4,5,8,9,12-hexaazatriphenylene; bpy = 2,2'-bipyridine) species display a marked dependence on the nuclearity and extent of oxidation of the assemblies, while small differences are also observed for the diastereoisomers of the same complex in the dinuclear cases. The mixed-valence heterochiral [[Ru(bpy)2]2[Os(bpy)2](mu-HAT)]n+ (n = 7, 8) forms exhibit IVCT properties that are intermediate between those of the diastereoisomeric forms of the localized hetero-dinuclear complex [[Ru(bpy)2](mu-HAT)[Os(bpy)2]]5+ and the borderline localized-to-delocalized homo-trinuclear complex [[Ru(bpy)2]3(mu-HAT)]n+ (n = 7, 8). The near-infrared (NIR) spectrum of the +7 mixed-valence species exhibits both interconfigurational (IC) and IVCT transitions which are quantitatively similar to those in [[Ru(bpy)2](mu-HAT)[Os(bpy)2]]5+ and are indicative of the localized mixed-valence formulation [[Ru(II)(bpy)2]2[Os(III)(bpy)2](mu-HAT)]7+. The +8 state exhibits a new band attributable to an IVCT transition in the near-infrared region.

Metal–metal bonding in molecular actinide compounds: electronic structure of [M2X8]2−(M = U, Np, Pu; X = Cl, Br, I) complexes and comparison with d-block analogues

Density functional and multiconfigurational (ab initio) calculations have been performed on [M(2)X(8)](2-) (X = Cl, Br, I) complexes of 4d (Mo, Tc, Ru), 5d (W, Re, Os), and 5f (U, Np, Pu) metals in order to investigate general trends, similarities and differences in the electronic structure and metal-metal bonding between f-block and d-block elements. Multiple metal-metal bonds consisting of a combination of sigma and pi interactions have been found in all species investigated, with delta-like interactions also occurring in the complexes of Tc, Re, Np, Ru, Os, and Pu. The molecular orbital analysis indicates that these metal-metal interactions possess predominantly d(z2) (sigma), d(xz) and d(yz) (pi), or d(xy) and d(x2-y2) (delta) character in the d-block species, and f(z3) (sigma), f(z2x) and f(z2y) (pi), or f(xyz) and f(z) (delta) character in the actinide systems. In the latter, all three (sigma, pi, delta) types of interaction exhibit bonding character, irrespective of whether the molecular symmetry is D(4h) or D(4d). By contrast, although the nature and properties of the sigma and pi bonds are largely similar for the D(4h) and D(4d) forms of the d-block complexes, the two most relevant metal-metal delta-like orbitals occur as a bonding and antibonding combination in D(4h) symmetry but as a nonbonding level in D(4d) symmetry. Multiconfigurational calculations have been performed on a subset of the actinide complexes, and show that a single electronic configuration plays a dominant role and corresponds to the lowest-energy configuration obtained using density functional theory.

Stereoselectivity in the formation of tris-diimine complexes of Fe(ii), Ru(ii), and Os(ii) with a C2-symmetric chiral derivative of 2,2′-bipyridine

A C2-symmetric enantiopure 4,5-bis(pinene)-2,2'-bipyridine ligand (-)-L was used to investigate the diastereoselectivity in the formation of [ML3]2+ coordination species (M = Fe(II), Ru(II), Os(II), Zn(II), Cd(II), Cu(II), Ni(II)), and [ML2Cl2] (M = Ru(II), Os(II)). The X-ray structures of the [ML3]2+ complexes were determined for Delta-[FeL3](PF6)2, Delta-[RuL3](PF6)2, Lambda-[RuL3](PF6)2, Delta-[OsL3](PF6)2, and Lambda-[OsL3](TfO)2. All of these compounds were also characterized by NMR, CD and UV/VIS absorption spectroscopy. The [FeL3]2+ diastereoisomers were studied in equilibrated solutions at various temperatures and in several solvents. The [RuL3]2+ complexes, which are thermally stable up to 200 degrees C, were photochemically equilibrated.

The influence of bridging ligand electronic structure on the photophysical properties of noble metal diimine and triimine light harvesting systems

This manuscript discusses the photophysical behavior of transition metal complexes of Ru(II) and Os(II) employed in development of light harvesting arrays of chromophores. Particular emphasis is placed on the relationship between the photophysical behavior of complexes having metal-to-ligand charge transfer (MLCT) excited states and the electronic characteristics of bridging ligands used in preparing oligometallic complexes. Examples are presented that discuss intramolecular energy migration in complexes having two distinct MLCT chromophores with bridging ligands that only very weakly couple the two chromophores. In addition, systems having bridging ligands with localized triplet excited states lower in energy than the MLCT state of the metal center to which they are attached are discussed. These systems very often have excited states localized on the bridging ligand with excited state lifetimes on the order of tens of microseconds. Finally, systems having Fe(II) metal centers, with very low energy MLCT states, are discussed. In complexes also containing bridging ligands with low energy triplet states, energy partitioning between the Fe center MLCT state (or Fe localized ligand field states) and the ligand triplet state is observed; the two states relax to the ground state via parallel pathways, but the Fe(II) center does not serve as an absolute excitation energy sink.

Preparation of Half-Sandwich Osmium-Allyl Complexes by Consecutive C−C Bond Formation and C−H Bond Activation Reactions

The vinylidene complex Os(η5-C5H5)Cl(CCHPh)(PiPr3) (1) reacts with MeMgCl to give the osmaindene (2), which isomerizes into the exo-allyl compound Os(η5-C5H5)(η3-CH2CHCHPh)(PiPr3) (3) in refluxing toluene. Treatment of 3 with HBF4·OEt2 leads to the endo-d4-allyl derivative [OsH(η5-C5H5){η3-CH2CHCHPh}(PiPr3)]BF4 (4), which can be also obtained by addition of HBF4·OEt2 to 2. Complex 4 contains the terminal CHPh group of the allyl cisoid disposed to the phosphine. In dichloromethane at 40 °C, it isomerizes into an endo-allyl isomer 5 with the terminal CHPh group cisoid disposed to the hydride. Complex 1 also reacts with EtMgCl. The reaction affords (6), which in toluene at 70 °C is converted into the exo-allyl complex Os(η5-C5H5){η3-CH(CH3)CHCHPh}(PiPr3) (7). Treatment of 7 with HBF4·OEt2 leads to an equilibrium mixture of exo-d4-allyl derivatives of formula [OsH(η5-C5H5){η3-CH(CH3)CHCHPh}(PiPr3)]BF4 (8 and 9). The addition of HBF4·OEt2 to 6 gives an endo-d4-allyl isomer, 10, which is transformed into the equilibrium mixture of 8 and 9 after 7 days in dichloromethane at 40 °C. Treatment of 1 with PhMgCl gives rise to (11), which reacts with HBF4·OEt2 in the presence of acetonitrile to afford stilbene and the solvento complex [Os(η5-C5H5)(CH3CN)2(PiPr3)]BF4 (12). The X-ray structures of 3, 5, and 8 are also reported.

Experimental and Computational Studies of Nucleophilic Attack, Tautomerization, and Hydride Migration in Benzoheterocycle Triosmium Clusters

The reactions of Os3(CO)9(μ3-η2-(L-H))(μ-H) (L = benzothiazole (7), benzoxazole (8)) with H-/H+ are reported, We observe only nucleophilic attack at the 2-position followed by protonation at the metal core to yield the 48e μ-amido−aryl complexes Os3(CO)9(μ3-η2-(L-H))(μ-H)2 (L = benzothiazole (9), benzoxazole (10)). The solid-state structure of 9 is reported. On thermolysis these complexes tautomerize to the corresponding μ-alkylidene−imino complexes 11 (L = benzothiazole) and 12 (L = benzoxazole) with equilibrium constants of 11/9 = 1.6 and 12/10 = 3.1. The tautomerization takes place with first-order rate constants of (6.42 ± 0.6) × 10-5 and (1.28 ± 0.1) × 10-4 s-1 for 9 → 11 and 10 → 12, respectively. Substitution of a methyl group at the 2-position in the case of 7 changes the site of hydride attack to the 4-position and results in the formation of the σ−π-vinyl complex Os3(CO)9(μ3-η3-(2-CH3)C7H5NS)(μ-H) (9‘). The complexes Os3(CO)9(μ3-η2-(L-2H))(μ-H)2 (L = tetrahydroquinoline (3), indoline (4)) also t...

Oxidations catalyzed by osmium compounds. Part 1: Efficient alkane oxidation with peroxides catalyzed by an olefin carbonyl osmium(0) complex

A carbonyl osmium(0) complex with π-coordinated olefin, (2,3-η-1,4-diphenylbut-2-en-1,4-dione)undecacarbonyl triangulotriosmium ( 1), efficiently catalyzes oxygenation of alkanes (cyclohexane, cyclooctane, n-heptane, isooctane, etc.) with hydrogen peroxide, as well as with tert-butyl hydroperoxide and meta-chloroperoxybenzoic acid in acetonitrile solution. Alkanes are oxidized to corresponding alcohols, ketones (aldehydes) and alkyl hydroperoxides. Thus, heating cyclooctane with the 1–H 2O 2 combination at 70 °C gave products with turnover number as high as 2400 after 6 h. The maximum obtained yield of all products was equal to 20% based on cyclohexane and 30% based on H 2O 2. The oxidation of linear and branched alkanes exhibits very low regio- and bond-selectivity parameters and this testifies that the reaction proceeds via attack of hydroxyl radicals on C–H bonds of the alkane. The oxygenation products were not formed when the reaction was carried out under argon atmosphere and it can be thus concluded that the oxygenation occurs via the reaction between alkyl radicals and atmospheric oxygen. In summary, the Os(0) complex is much more powerful generator of hydroxyl radicals than any soluble derivative of iron (which is an analogue of osmium in the Periodic System).

Electrochemical characterisation of an Os (II) conjugated polymer in aqueous electrolytes

The electrochemical behaviour of an Os (II) complex of the structurally well-defined conjugated polymer alternating regioregularly alkylated thiophene and 2,2′-bipyridine units (P4Os) has been elucidated in aqueous solution. In typical aqueous electrolyte systems, the cyclic voltammogram of the resulting P4Os film exhibits a one-electron reversible process corresponding to the Os 3+/2+ redox system. However, the observance of this reversible couple did depend upon the concentration of the supporting electrolyte. It was found that the Os 3+ form did form ion-pairs with an anion from the electrolyte solution. Preliminary investigations into the homogeneous charge transport dynamics associated with this redox couple have been undertaken. The technique of cyclic voltammetry, and hence the Randles–Sevick expression, in conjunction with platinum microelectrodes have been employed to determine the D CT C value.

Computational Studies of the Energetics and Reaction Pathways of Molecular Transformations of Benzoheterocycles on Triosmium Clusters

Density functional theory (DFT) calculations have been performed on the series of complexes Os3(CO)10-n(μm-η2-(L-H))(μ-H) (L = benzoxazole (1), benzothiazole (2), quinoline (3), indoline (4), 1,2,3,4-tetrahydroquinoline (5); for 1−5, n = 0; m = 2; for 1‘−3‘, n = 1, m = 3) and on the precursors to these complexes, Os3(CO)10(CH3CN)2 and Os3(CO)12. The optimized geometry of the coordinately unsaturated 44e system Os3(CO)10 is used as a reference point for evaluating the relative binding energies of the heterocycles and the acetonitrile and carbonyl ligands. A discussion of how the intramolecular trans/cis isomerization of Os3(CO)10(CH3CN)2 relates to the reactivity of this complex with the heterocyclic ligand is presented. The relative binding energies of the benzoheterocycles provide insight into the relative stability of the intermediates involved in the subsequent formation of the μ3-nonacarbonyl derivatives Os3(CO)9(μ3-η2-(L-2H))(μ-H)2 (L = indoline (4‘), 1,2,3,4-tetrahydroquinoline (5‘)) from their μ-de...

Sensitization of Nanocrystalline TiO2 with Black Absorbers Based on Os and Ru Polypyridine Complexes

New metal complexes of the type [M(H3tcterpy)LY]+ (where M = Os(II) or Ru(II), L = substituted or unsubstituted bipyridine or pyridylquinoline, and Y = Cl-, I-, or SCN-) have been designed, synthesized, and characterized in view of their application for dye-sensitized solar cells (DSSCs). The Os dyes show a very broad absorption, and correspondingly, the DSSCs show an unprecedented spectral response in the NIR, with an onset at 1100 nm, reaching values of about 50% at 900 nm. The integrated photocurrent of some of such Os dyes is similar to that of the well-known [Ru(Htcterpy)(NCS)3](TBA) and superior to that of the [Ru(Hdcbpy)2(NCS)2](TBA)2 sensitizer. The Ru dyes show absorption and DSSC spectral response between those of the red and black dyes. Their advantage is their potential superior stability due to the reversible oxidative electrochemistry.

Interplay between Intra‐ and Interligand Charge Transfer with Variation of the Axial N‐Heterocyclic Ligand in Osmium(II) Pyridylpyrazolate Complexes: Extensive Color Tuning by Phosphorescent Solvatochromism

The rational design and syntheses of a new series of Os(II) complexes with formula [Os(fppz)(2)(CO)(L)] (1: L=4-dimethylaminopyridine; 2: L = pyridine; 3: L = 4,4'-bipyridine; 4: L = pyridazine; 5: L = 4-cyanopyridine), bearing two (2-pyridyl)pyrazolate ligands (fppz) together with one carbonyl and one N-heterocyclic ligand at the axial positions are reported. Single-crystal X-ray diffraction studies of, for example, 2 reveal a distorted octahedral geometry in which both fppz ligands reside in the equatorial plane with a trans configuration and adopt a bent arrangement at the metal center with a dihedral angle of approximately 23 degrees , while the carbonyl and pyridine ligands are located at the axial positions. Variation of the axial N-heterocyclic ligand leads to remarkable changes in the photophysical properties as the energy gap and hence the phosphorescence peak wavelength can be tuned. For complexes 1 and 2 the solvent-polarity-independent phosphorescence originates from a combination of intraligand (3)pi-pi* ((3)ILCT) and metal-to-ligand charge transfer transitions ((3)MLCT). In sharp contrast, as supported by cyclic voltammetry measurements and theoretical calculations, complexes 3--5 exhibit mainly ligand-to-ligand charge transfer (LLCT) transitions, resulting in a large dipolar change. The phosphorescence of complexes 3--5 thus exhibits a strong dependence on the polarity of the solvent, being shifted for example, from 560 (in C(6)H(12)) to 665 nm (in CH(3)CN) and from 603 (in C(6)H(12)) to 710 nm (in CH(3)CN) for complexes 3 and 5, respectively. The results clearly demonstrate that a simple, straightforward derivatization of the axial N-heterocyclic ligand drastically alters the excitation properties per se from intraligand charge transfer (ILCT) to LLCT transitions. The latter exhibit remarkable LLCT phosphorescence solvatochromism so that a broad range of color tunability can be achieved.

Eilatin Complexes of Ruthenium and Osmium. Synthesis, Electrochemical Behavior, and Near-IR Luminescence

The synthesis and characterization of new Ru(II) and Os(II) complexes of the ligand eilatin (1) are described. The new complexes [Ru(bpy)(eil)(2)](2+) (2), [Ru(eil)(3)](2+) (3), and [Os(eil)(3)](2+) (4) (bpy = 2,2'-bipyridine; eil = eilatin) were synthesized and characterized by NMR, fast atom bombardment mass spectrometry, and elemental analysis. In the series of complexes [Ru(bpy)(x)(eil)(y)()](2+) (x + y = 3), the effect of sequential substitution of eil for bpy on the electrochemical and photophysical properties was examined. The absorption spectra of the complexes exhibit several bpy- and eil-associated pi-pi and metal-to-ligand charge-transfer (MLCT) transitions in the visible region (400-600 nm), whose energy and relative intensity depend on the number of ligands bound to the metal center (x and y). On going from [Ru(bpy)(2)(eil)](2+) (5) to 2 to 3, the d(pi)(Ru) --> pi(eil) MLCT transition undergoes a red shift from 583 to 591 to 599 nm, respectively. Electrochemical measurements performed in dimethyl sulfoxide reveal several ligand-based reduction processes, where each eil ligand can accept up to two electrons at potentials that are significantly anodically shifted (by ca. 1 V) with respect to the bpy ligands. The complexes exhibit near-IR emission (900-1100 nm) of typical (3)MLCT character, both at room temperature and at 77 K. Along the series 5, 2, and 3, upon substitution of eil for bpy, the emission maxima undergo a blue shift and the quantum yields and lifetimes increase. The radiative and nonradiative processes that contribute to deactivation of the excited level are discussed in detail.

The Cyclopentadienyl-Osmium Moiety as Template for the Formation of a Dihydronaphthylphosphine by Coupling between Phenylacetylene and an α-Alkenylphosphine

Complex Os(η5-C5H5)(C⋮CPh){[η2-CH2C(CH3)]PiPr2} (1) reacts with HBF4·OEt2 to give the π-alkyne derivative [Os(η5-C5H5)(η2-HC⋮CPh){[η2-CH2C(CH3)]PiPr2}]BF4 (2), which is transformed to [Os(η5-C5H5)(1,2-dihydro-2-methylnaphth-2-yldiisopropylphosphine)]BF4 (3) as a result of the coupling of the alkyne with the isopropenyl substituent of the starting phosphine. The tridentate coordination mode of the dihydronaphthylphosphine in 3 is proved by X-ray diffraction analysis.

Synthesis, Structure, and Transformation of Novel Osmium Azine and Ylide Complexes

Three novel triosmium complexes with unusual coordination characteristics are reported. Treatment of the hydridotriosmium cluster (mu-H)2Os3(CO)10 with CNNPPh3 in CH2Cl2 gave complexes (mu-H)Os3(CO)(10)(mu2-eta2-C(H)NNPPh3) (1) and (mu-H)Os3(CO)10(mu2-eta1-CHPPh3) (2). Complex 1 represents the first example of the existence of a coordinated phosphinazine ligand. An in-situ 1H NMR study showed that the reaction of (mu-H)2Os3(CO)10 with CNNPPh3 produced complex 1 as the initial product in 100% conversion. The latter is not stable in solution and slowly eliminates nitrogen to form an unusual ylide complex 2 in quantitative yield. The thermolysis of 2 in refluxing toluene afforded (mu-H)3Os3(CO)9(mu3-eta1-CCO2CH2Ph) (3) as a colorless compound. Complexes 1-3 were characterized by spectroscopic methods and single-crystal X-ray diffraction analysis. The interesting feature of structure 3 is the presence of a mu3-alkylidyne ligand where the symmetrically triply bridged CCO2CH2Ph fragment lies perpendicular to and above the triosmium triangle.

Bis-chelated-arylazoimidazole-1,10-phenanthroline–osmium(II) complexes. Structure, spectra and electrochemistry

[Os(phen)(RaaiR′) 2](PF 6) 2 [phen = 1,10-phenanthroline, RaaiR′ = 1-alkyl-2-(arylazo)imidazole, p-R–C 6H 4–N N–C 3H 2–NN–1-R′, where R = H ( a), Me ( b), Cl ( c) and R′ = Me ( 2), Et ( 3), CH 2Ph ( 4) have been synthesized from the reaction of cis– trans– cis-[OsBr 2(RaaiR′) 2] with phen in the presence of aqueous AgNO 3 in ethanol. The structure of [Os(phen)(ClaaiEt) 2](PF 6) 2 was confirmed by X-ray diffraction study. Electronic spectra exhibit a strong MLCT band at 490–512 nm along with weak transition at longer wavelength 865–880 nm. Cyclic voltammetry of the complexes shows two metal redox couples, Os(III)/Os(II) at 0.9–1.0 V and Os(IV)/Os(III) at 1.4–1.6 V versus SCE, and three successive ligand reductions. The EHMO calculation using crystallographic parameters of the complex has been compared with analogous Ru and Os complexes. A correlation between electronic properties and MO results is also reported.

Theoretical investigations of the reactivity of MO4 and the electronic structure of Na2[MO4(OH)2], where M=Ru, Os, and Hs (element 108)

Abstract Fully relativistic, four-component, density functional theory calculations (4c-DFT) were performed for [MO4(OH)2]2- and Na2[MO4(OH)2], where M=Ru, Os, and Hs. The electronic structure of the Hs complex ion was shown to be similar to that of the Os complex ion, though [HsO4(OH)2]2- should be more covalent than the lighter congeners in group 8, by analogy with MO4. The calculations of the free energy change, Δ G r, of the [MO4(OH)2]2- and Na2[MO4(OH)2] formation reactions from the volatile tetroxides and NaOH have shown that HsO4 should be slightly less reactive than OsO4, with the difference in ΔG r being less than 52 kJ/mol. In the experimental study of the deposition of OsO4 and HsO4 on the surface of NaOH in the presence of water, such a difference in reactivity has not yet been clearly revealed. The anionic complex of Ru(VIII) was found to be much less stable than those of Os and Hs. Also, Delta;G r for the formation of [RuO4(OH)2]2- from RuO4 was found to be ∼300 kJ/mol more positive than ΔG r for analogous reactions of Os and Hs, which explains why the Ru(VIII) complex is not known. The ionic radii, IR(Hs8+)=0.454 Å for CN=4, IR(Os8+) = 0.49 Å and IR(Hs8+) = 0.54 Å for CN=6, have been obtained on the basis of the calculations of bond lengths in MO4, as well as via a correlation between R max of the outer np obitals and IR of the 5d and 6d elements, respectively.