The metal-chain complexes (X)[Os(CO)3(CNBu)]3Mn(CO)5 (X=Cl, Br, I)

In what is a new metal-chain forming reaction, (X)[Os(CO)₃(CNBu^t)]₃Mn(CO)₅ (X=Cl, Br, I) complexes have been prepared by the successive addition of Os(CO)₄(CNBu^t) to Mn(CO)₅(X) in hexane. The crystal structure of the iodo derivative reveals it to contain an approximately linear Os₃ Mn chain of metal atoms.     

How the electronic and steric properties of the ligand can determine the stability of the asymmetric dinuclear carbonyl-phosphite Rh(0) complex (CO)2(P(O-o-tBuPh)3)Rh-Rh(P(O-o-tBuPh)3)(CO)3

Theoretical studies have shown that the low basicity of the phosphite ligand P(O-o-^tBuPh)₃ in the Rh(0) complex (CO)₂(P(O-o-^tBuPh)₃)Rh-Rh(P(O-o-^tBuPh)₃)(CO)₃ favours the non-bridged structure over the bridged one, but is not responsible for the absence of the expected sixth carbonyl in the structure. The steric effects of the bulky ligand play an important role in the unusual stability of the asymmetric complex.     

Photochemistry of Os(bipy)2(CO3). Photoreduction of carbonate to formaldehyde

The complex Os(II)(bipy)₂(CO₃) undergoes a photoredox reaction in acetonitrile/H₂O yielding [Os(VI)(bipy)₂(O)₂]^2 + and formaldehyde. The reactive excited state is suggested to be of the (Os(II) to π* carbonate) MLCT type.     

New evidence on the factors affecting bridging and semibridging character of carbonyl ligands. The structures of Mn2(CO)7(μ-SCH2CH2S) and its phosphine derivatives Mn2(CO)7-X(PMe2Ph)X(μ-SCH2CH2S), × = 1,2

The new ethanedithiolate—dimanganese carbonyl complex, Mn₂(μ-SCH₂CH₂S)(CO)₇, 1 , was prepared in 28% yield from the reaction of 1,2,5,6-tetrathiacyclooctane with Mn₂(CO)₉(NCMe). Complex 1 was characterized crystal-lographically. It contains two Mn(CO)₃ groups joined by a Mn–Mn bond of 2.6470(6) Å in length, a dihapto-bridging ethanedithiolate ligand, and one strong semibridging CO ligand. The reaction of 1 with PMe₂Ph yielded two derivatives: Mn₂(μ-SCH₂CH₂S)(CO)₆(PMe₂Ph), 2 , and gem-Mn₂(μ-SCH₂CH₂S)(CO)₅(PMe₂Ph)₂, 3a , in 48% and 6% yields, respectively. When heated at 40 °C, compound 3a was transformed into three isomers, iso-gem-Mn₂(μ-SCH₂CH₂S)(CO)₅(PMe₂Ph)₂, 3b , 1,2-Mn₂(μ-SCH₂CH₂S)(CO)₅(PMe₂Ph)₂, 3c , and cis-Mn₂(μ-SCH₂CH₂S)-(CO)₅(PMe₂Ph)₂, 3d . Compounds 3b and 3c were characterized by single-crystal X-ray diffraction analyses. The introduction of phosphine ligand into the complexes strongly affects the semibridging character of the carbonyl ligand.     

Synthesis,structure and stability of fac-[FeII(CO)3X3]1− (X = Br,I)

fac-[Fe^II(CO)₃X₃]^1? (X = Br, I) are synthesized and their structures have been determined. They are the first crystallographically characterized iron tricarbonyl trihalide complexes. fac-[Fe^II(CO)₃X₃]^1? (X = Br, I) are fairly thermally stable and therefore lead themselves as excellent starting materials for the preparation of various iron carbonyl complexes since both the halide and carbonyl ligands are substitutionally labile.     

Variable temperature13C MAS NMR of KFe2Mn(CO)12 in the solid state and as aCatalyst precursor on a carbon support

Variable temperature¹³C MAS NMR spectra are reported for¹³CO-enriched KFe₂Mn(CO)₁₂ as a solid and also as dispersed clusters on a carbon support. The spectrum of KFe₂Mn(CO)₁₂ at 300 K agrees with the proposed structure for this cluster and shows that the cluster is static. Two bridging carbonyl resonances are clearly resolved and, by comparison with¹³C MAS NMR spectra of Mn₂(CO)₁₀ and Fe₂(CO)₉, all terminal resonances for the cluster can be assigned. When the cluster is supported on carbon, two broad resonances are observed at room temperature which are assignable to KFe₂Mn(CO)₁₂ and a decomposition product, Mn₂(CO)₁₀. The carbonyl ligands in both supported clusters are completely averaged, and KFe₂Mn(CO)₁₂ on the carbon surface demonstrates fluxional behavior similar to that observed for the cluster in solution. For this fluxional process, activation energies of 0.6 kcal/mol and 0.5 kcal/mol are estimated for carbon-supported KFe₂Mn(CO)₁₂ and Mn₂(CO)₁₀, respectively.     

Effect of nitrogen-donor ligands on the stability of the photolysis products of Mn2(CO)10

The photolysis of Mn₂(CO)₁₀ in the presence of nitrogen donor ligands has been investigated in various solvents. The disproportionation reaction has been found to be strongly dependent on the solvent and on the temperature. The substitution of CO with the nitrogen donor ligand takes place on the anion Mn(CO)^?₅. The polymeric ligand poly(4-vinylpyridine) manifests a stabilizing effect on the substitution product.     

Synthesis,Cytotoxicity, and Insight into the Mode of Action of Re(CO)3 Thymidine Complexes

Nucleoside analogues are extensively used in the treatment of cancer and viral diseases. The antiproliferative properties of organorhenium(I) complexes, however, have been scarcely explored to date. Herein we present the syntheses, characterization, and in vitro evaluation of Re^I(CO)₃ core complexes of thymidine and uridine. For the binding of the Re^I(CO)₃ core, a tridentate dipicolylamine metal chelate was introduced at positions C5′, C2′, N3, and C5 with spacers of various lengths. The corresponding organometallic thymidine complexes were fully characterized by IR and NMR spectroscopy and mass spectrometry. Their cytotoxicity was assessed against the A549 lung carcinoma cell line. Toxicity is dependent on the site and mode of conjugation as well as on the nature and the length of the tether. Moderate toxicity was observed for conjugates carrying the rhenium moiety at position C5′ or N3 (IC₅₀=124–160 μM ). No toxicity was observed for complexes modified at C2′ or C5. Complex 53 , with a dodecylene spacer at C5′, exhibits remarkable toxicity and is more potent than cisplatin, with an IC₅₀ value of 6.0 μM . To the best of our knowledge, this is the first report of the antiproliferative properties of [M(CO)₃]⁺¹–nucleoside conjugates. In competitive inhibition experiments with A549 cell lysates and purified recombinant human thymidine kinase 1 (hTK‐1), enzyme inhibition was observed for complexes modified at either N3 or C5′, but our results suggest that the toxicity cannot be attributed solely to interaction with hTK‐1.     

Oxidative addition of halogens to MoRu(CO)6(dppm)2

Halogens oxidatively add to MoRu(CO)₆(μ-dppm)₂ (1) at ambient temperature to yield [(CO)₂Mo(μ-X)(μ-CO)(μ-dppm)₂Ru(CO)₂]⁺[Mo(CO)₄X₃]⁻, where X=Cl (2) or I (3), dppm=Ph₂PCH₂PPh₂, and the μ-CO is semi-bridging. Complexes 2 and 3 have been characterized by elemental analysis, conductivity, and NMR spectroscopy, while the molecular structure of 3 has been determined by X-ray crystallography. Ignoring a weak metal–metal bond interaction, the cation of 3 is most easily described as pseudo-octahedral at Ru(II) and Mo(0) centres; the anion is a monocapped octahedron that has been described previously.     

Substitution of CO Ligand by P(OPh)3 in Radical Cations of the Cymantrene Family: Relationships of Substitution Rates to E1/2 Values and Carbonyl IR Frequencies

A series of piano-stool complexes of the cymantrene family (cymantrene = Mn(η⁵-C₅H₅)(CO)₃, 1) undergoes facile replacement of a carbonyl ligand by P(OPh)₃ when oxidized by one-electron in CH₂Cl₂/[NBu₄][B(C₆F₅)₄]. Data on the previously characterized complexes 1, Mn(η⁵-C₅H₄NH₂)(CO)₃ (3) and Mn(η⁵-C₅Me₅)(CO)₃ (6) have been supplemented by cyclic voltammetry (CV) and IR spectroscopy on Mn(η⁵-C₅H₄Me)(CO)₃ (2), Mn(η⁵-C₅H₄I)(CO)₃ (4), and Mn(η⁵-C₅H₄C(O)H)(CO)₃ (5). The substitution rates, determined by digital simulations of CV scans, ranged from 4 M^?1 s^?1 for 6 ⁺ to 3 × 10⁵ M^?1 s^?1 for 5 ⁺. In general, a more strongly donating cyclopentadienyl substituent slows down the CO substitution rate. For mono-cyclopentadienyl substituted complexes, the logarithm of k_sub is shown to increase linearly with either the weighted average of the CO stretching frequencies or the E_1/2 value of the redox process. An exception to this generalization is the amine-substituted complex 3, for which the CO-substitution rate is higher than predicted by its E_1/2 potential. The substitution rate of the pentamethylated Cp complex 6 ⁺ is slowed by about an order of magnitude owing to steric effects. The efficacy of this method to predict the CO-substitution rate of a cymantrene-tagged molecule was tested with a cymamtrene-derivatized diarylethene complex, 7. The measured P(OPh)₃-for-CO substitution rate of 3.7 × 10² M^?1 s^?1 for 7 ⁺ was very close to that predicted by the E_1/2 value of 7. A ligand electronic parameter, E_L, of 0.62 was determined for the triphenylphosphite ligand. These studies build on the previous CO substitution-rate analyses by Sweigart and others.     

A novel dianionic seven-coordinate complex of tungsten(II), [WCl3(GeCl3)(CO)3]2−: Synthesis,spectroscopic properties and X-ray crystal structure

A new dianionic complex of tungsten(II), [(WCl₃(GeCl₃)(CO)₃]²⁻ (1²⁻), containing the piperidinium cations [Hpip]⁺ as the counter ions, has been obtained from the reaction between [W(CO)₄(pip)₂] and GeCl₄ in dichloromethane solution, and its molecular structure has been elucidated by single-crystal X-ray diffraction studies. The chemical properties of complex 1 were investigated by IR and NMR spectroscopy in solution.     

Tetra- and hexanuclear cage molecules based on diruthenium tetracarbonyl sawhorse units: Synthesis and molecular structure of [{Ru2(CO)4(PPh3)2}2(O2CCH2CO2)2] and [{Ru2(CO)4(PMe3)2}3(O2CC6H4CO2)3]

The thermal reaction of Ru₃(CO)₁₂ with malonic acid, followed by the addition of the corresponding ligand, yields the tetranuclear ruthenium complexes [{Ru₂(CO)₄L₂}₂(O₂CCH₂CO₂)₂] (L = PPh₃: 1, L = 3,5-Me₂NC₅H₃: 2), while the reaction of Ru₃(CO)₁₂ with terephthalic acid, followed by the addition of the corresponding ligand, gives rise to the formation of the hexanuclear ruthenium complexes [{Ru₂(CO)₄L₂}₃(O₂CC₆H₄CO₂)₃] (L = PMe₃: 3, L = 3,5-Me₂NC₅H₃: 4). The single-crystal X-ray structure analyses for 1 and 3, reveal both cages to consist of Ru₂(CO)₄ sawhorse units, 1 being a molecular loop, while 3 is a molecular triangle.     

A triheterometallic cluster: synthesis and structural characterisation of a cyclopentadienyl-substituted pentanuclear cluster based on an Os3CoRu metal core

The ionic coupling of the carbonyl cluster anion [Os₃Co(CO)₁₃]⁻ (1) with [Ru(η⁵-C₅H₅)(NCMe)₃]⁺ affords the new pentanuclear triheterometallic cluster Os₃CoRu(CO)₁₃(η⁵-C₅H₅) (2) as well as the known bimetallic cluster compounds HOs₃Ru(CO)₁₁(η⁵-C₅H₅) and Os₃Ru₂(CO)₁₁(η⁵-C₅H₅)₂. The crystal structure of cluster 2 shows that the metal framework is based on a trigonal bipyramid (approximate C_s symmetry) with the Ru, Co and an Os atom occupying the equatorial metal plane.     

X-ray single-crystal structure and magnetic properties of KMn(H2O)5Ru2(CO3)4·5H2O: A layered soft magnet

The temperature manipulation induces the aggregation of Ru₂(CO₃)₄^3 − paddle-wheel precursors and Mn^2 + ions in lower temperature ~ 10 °C forming layer structural complex, K[Mn(H₂O)₄Ru₂(CO₃)₄]·5H₂O (1). It composes of new negative layer {Mn(H₂O)₅Ru₂(CO₃)₄}_nⁿ⁻, and magnetic exchanges between spin centers result in ordering below 3.8 K. The observed critical temperature is like the previously reported 3D hetero-metallic carbonates H_0.3K_0.7Mn[Ru₂(CO₃)₄](H₂O)_5.5, which demonstrates that it is independent of the interlayer connecting in such heterometallic complexes based on square-grid layer {Ru₂(CO₃)₄}_n³ⁿ⁻.     

Synthesis,Characterization, and Reactivity of trans-Ru(X)(Cl)(nbd)(dppb) (X = H,Cl; nbd = 2,5-norbornadiene; dppb = 1,4-bis(diphenylphosphino)butane), Including the X-ray Crystal Structure of the Dichloride

The ruthenium (II) diene complexes [Ru(X)(Cl)(nbd)(dppb)] (X = Cl, H; nbd = 2,5-norbornadiene; dppb = PPh₂(CH₂)₄PPh₂) have been prepared and characterized spectroscopically. The X-ray crystal structure of RuCl₂(nbd)(dppb) (crystal data at 22°C: space group P1, a = 10.896 (1) Å, b = 15.168(2) Å, c = 10.829 (1) Å, α = 103.02(1)°, β = 107.08(1)°, γ = 81.65(1)°, Z = 2, R = 0.054 for 6420 reflections) shows an octahedral geometry at Ru, with the chloro ligands slightly distorted from a trans configuration (Cl)(1)-Ru-C1(2) = 168.4°); the unit cell contains two molecules of the complex and one molecule of benzene. Reaction of this complex with H₂, in presence of Proton Sponge (PS, 1,8-bis(dimethylamino)naphthalene) as base, is complicated by initial dissociation of nbd, and [Ru₂Cl₅(dppb)₂]⁻-PSH⁺ is the major product. A minor product, the hydrido(diene) complex trans-RuCl(nbd)(dppb) 5 , characterized spectroscopically, is more effectively synthesized from (a) trans-Ru(H)Cl(nbd)(PPh₃)₂, 1 , and dppb, or (b) reaction of RuCl₂(dppb)-(PPh₃) with H₂ in presence of nbd and PS. Complex 5 is unreactive toward H₂ or CO while 1 has been shown previously to give η²-H₂ and norbornenoyl derivatives, respectively; the differences in reactivity are discussed.     

Coordination of a Schiff base as an iminium-phenone zwitterion in a double ligand-bridged fac-[Re(CO)3]+ dimer

The ligand-bridged dimers [Re(CO)₃(μ-H₂salet)]₂ (1) and [{Re(CO)₃}₂(μ-salpd)] (2) are formed by the reactions of [Re(CO)₅Cl] with the potentially heptadentate Schiff base 2,2′,2″-tris(salicylideneimino)triethylamine (H₃salet) and the hexadentate N¹-(3-(2-hydroxybenzylidene-amino)propylamino)ethyl)-benzylidenepropane-1,3-diamine (H₂salpd) respectively. In 1, the two H₂salet ligands bridge two fac-[Re(CO)₃]⁺ moieties. Mono-dentate coordination is by a neutral phenone oxygen atom, generated by the conversion of one salicylideneimine entity to an iminium zwitter-ion. In 2 each fac-[Re(CO)₃]⁺ core resides in a ‘3 + 0’ environment. In both complexes π–π interaction between the phenolate rings contribute to the stability. The crystal structures of 1 and 2 were determined by X-ray single crystal diffraction. Spectroscopic results are also reported.     

Umsetzungen des Pentamethylcyclopentadienyl‐Halbsandwichkomplexes Cp*Ta(CO)4 mit Chlor,Brom und Iod

The reaction of Cp*Ta(CO)₄ ( 1 ) (Cp* = η⁵‐pentamethylcyclopentadienyl, η⁵‐C₅Me₅) with chlorine leads to Cp*TaCl₄ ( 2a ), whereas the corresponding reactions with bromine or iodine give the oxo‐bridged complexes [Cp*TaX₃]₂(μ‐O) (X = Br ( 3b ), I ( 3c )). The oxygen atom apparently stems from a carbonyl ligand. In the presence of air, the binuclear complexes 3a , b are converted into mononuclear Cp*Ta(O)X₂ ( 4b , c ). The X‐ray structural determination of [Cp*TaBr₃]₂(μ‐O) ( 3b ) confirms a linear Ta–O–Ta bridge with a Ta–O distance of 190,4(1) pm.     

A new binuclear Cr(III) citrate anion: Synthesis,characterization and crystal structure of [Cr(CO(NH2)2)6]2[Cr2(CO(NH2)2)2(C6H4O7)2]3

The new anion [Cr₂(CO(NH₂)₂)₂(C₆H₄O₇)₂]^2 − has been isolated in the complex [Cr(CO(NH₂)₂)₆]₂[Cr₂(CO(NH₂)₂)₂(C₆H₄O₇)₂]₃. The crystals of this complex were obtained by a one-pot synthetic method using 1:1 molar ratio of hexaureachromium(III) chloride and trisodium citrate in aqueous medium. It was characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction analysis. The compound crystallizes in space group R‾3 of the trigonal system with three formula units in a cell of dimensions a = b = 24.7461(4) Å, c = 13.7204(3) Å and γ = 120°. The crystal structure comprises the columns consisting of [Cr(CO(NH₂)₂)₆]^3 + cations surrounded by a cylinder of complex anions, [Cr₂(CO(NH₂)₂)₂(C₆H₄O₇)₂]^2 − which are packed in a honeycomb-like manner. This supramolecular architecture is formed and stabilized by inter- and intramolecular NH⋯O hydrogen bonds.     

WGSR catalyzed by cis-[Rh(CO)2(amine)2]PF6 heterogenised on poly(4-vinylpyridine)

This paper describes catalytic activation studies of the water–gas shift reaction by cis-[Rh(CO)₂(amine)₂]PF₆ (amine = 4-picoline, 3-picoline, 2-picoline, pyridine, or 2,6-lutidine) heterogenised on poly(4-vinylpyridine) in aqueous 2-ethoxyethanol. The effect of varying the nature of the amine was investigated. The rhodium complexes bearing 4-picoline (4-pic) ligands proved to be most active among those surveyed, and displaying turnover frequencies for hydrogen production of 8.9 mol of H₂ per mole of Rh per day for 9.4x10^-5 mol cis-[Rh(CO)₂(4-pic)₂]PF₆/1.00 g poly(4-vinylpyridine), P(CO) = 0.9 atm at 100°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and crystal structure of the mixed-valence trinuclear cobalt complex {[Co(CN)3(tBuNC)2](μ-CN)[Co(tBuNC)4](μ-CN)[Co(CN)3(tBuNC)2]}

The mixed-valence trinuclear cobalt compound {[Co(CN)₃(^tBuNC)₂](μ-CN)[Co(^tBuNC)₄](μ-CN)[Co(CN)₃(^tBuNC)₂]} is produced from the reaction of CoCl₂ with KCN and tert-butylisocyanide. In the resulting structure two cobalt atoms formally show the oxidation state +III, whereas the central cobalt still exhibits the formal oxidation state +II. All cobalt atoms are octahedrally coordinated by cyanide and isocyanide ligands. The supramolecular structure is determined by C–H⋯O and C–H⋯N hydrogen bonds linking acetone molecules to the trimeric complex as well as connecting the complex units into infinite chains.