Osmium Carbonyl Clusters Research Articles

The growth of higher nuclearity carbonyl clusters of ruthenium and osmium

In this review the synthetic and structural chemistry of osmium and ruthenium clusters is described with emphasis on the studies carried out during the 1980s and 1990s when research in the area was prolific. The methods of cluster synthesis are discussed as are the techniques used to characterise the complexes. The electron counting methods that are used to predict and rationalise the cluster structures are highlighted. Emphasis is placed on the synthetic methods used to build high nuclearity carbonyl clusters of osmium and ruthenium, namely vacuum pyrolysis, the linking of cluster fragments with bridging ligands, and the development of methodologies used to build higher nuclearity mixed-metal clusters.

Ligand substitution in the osmium carbonyl cluster Os2(CO)8(µ3-SbPh)Os(CO)3(Cl)2: Towards derivatives of the osmostibine metalloligand

Derivatisation of the osmium carbonyl cluster Os2(CO)8(µ3-SbPh)Os(CO)3(Cl)2, 1, the precursor to the metalloligand Os2(CO)8(µ-SbPh), 2, was explored as a route to derivatives of the latter. The reaction of 1 with PPh3 in different stoichiometries and under trimethylamine N-oxide activation in CH3CN led to mono-, di-, tri- and tetra-substitution by PPh3 and CH3CN. The first substitution occurred at the Os(CO)3Cl2 “spike” and although subsequent substitution favoured CH3CN at the osmostibine moiety, the latter was not readily displaced by PPh3. Substitution at the “spike” also shut down release of the substituted osmostibine. The CH3CN-substituted osmostibine could, however, be generated in situ through the bis-acetonitrile derivative of 1 by conversion of the Os(CO)2(NCCH3)Cl2 “spike” back into its removable Os(CO)3Cl2 form through reaction with CO gas, and was then trapped with W(CO)5(NCCH3).

Inhibition of Thioredoxin Reductase by Triosmium Carbonyl Clusters.

Tumor cells are characterized by increased reactive oxygen species production in parallel with an enhanced antioxidant system to avoid oxidative damage. The inhibition of antioxidant systems is an effective way to kill cancer cells, and the thioredoxin system or, more specifically, the cytosolic selenocysteine-containing enzyme thioredoxin reductase (TrxR) has become an interesting target for cancer therapy. We show here that the known cytotoxic and apoptosis-inducing osmium carbonyl cluster Os3(CO)10(NCCH3)2 (1) is a nonsubstrate inhibitor of mammalian TrxR, with an IC50 of 5.3 ± 0.9 μM. It inhibits TrxR selectively over the closely related glutathione reductase (GR) and in the presence of excess reduced glutathione (GSH). This inhibition has also been demonstrated in cell lysates, suggesting that TrxR inhibition is a potential apoptotic pathway for 1.

In Search of Multi-Stage Mutation Resistant HIV Drugs: A DFT Study

Aims: Searching of highly active (activity at the pico molar level) multi-stage, mutation registrant HIV-1 drug through theoretical and computational methodologies. Background: Recent advances of computational methodology to predict the important properties of a drug, like IC50, LogP, CC50, etc., assist in model and in-silico characterization of compounds as drug for variant deadly diseases. The drug potency of thio-propionate derivatives of iron, ruthenium and osmium carbonyl clusters are reported as less toxic,water-soluble, easy metabolic and effective as cancer drugs. Objective: The study of the drug-like activity of organo-metallic clusters of group-8 metals as HIV drug using the latest computational aids is the objective of the present research. Method: Quantum computational methodologies are used to predict the IC50, and LogP, CC50 of the modeled compounds. Density Functional Theory (DFT) calculations are used where it is required. Molecular docking methods are used for the study of the metabolic probability of the compound which has the best activity as an HIV drug. Result: It is observed that IC50 of Ru5(CO)14(µ−H)(µ−S(CH2)2COO−)Na+ is only 220 pico-mole as HIV-1 capsid -A inhibitor. Its inhibition activities in other enzymatic processes involved in the HIV life cycle in the human body are also studied and compared with the most used market available drugs. This modeled compound has supreme activity and less toxicity compared to the FDA approved drugs chosen for the comparison. Conclusion: From this study, it could be concluded that this modeled compound would be a multi-stage, mutation resistant HIV drug. Other: These findings would enrich the HIV drug search. Funding Statement: None to declare Declaration of Interests: None to declare

Metal carbonyl-gold nanoparticle conjugates for highly sensitive SERS detection of organophosphorus pesticides

The binding of organometallic osmium carbonyl clusters onto the surface of gold nanoparticles (10OsCO-Au NPs) greatly enhanced the CO stretching vibration signal at ~2100cm−1, which is relatively free from interference due to the absorbance of biomolecules. By utilizing the acetylcholinesterase (AChE) mediated hydrolysis of acetylthiocholine to thiocholine where the activity of AChE is inhibited by the presence of organophosphate pesticides (OPPs), the subsequent thiocholine-induced aggregation of 10OsCO-Au NPs can be monitored by the change in color of the NPs solution and the variation in intensity of the SERS CO signal. The change in color offers a fast pre-screening method, whereas monitoring via SERS is used for greater accuracy and lower limit of detection (0.1 ppb) for quantitative detection. Its potential as a quick and accurate method of OPPs monitoring in consumer products was demonstrated in the detection of OPPs in real spiked samples such as beer.

Antiproliferative activity of ruthenium and osmium clusters with phosphine ligands

New ruthenium and osmium carbonyl clusters with 1,3,5-triaza-7-phosphatricyclo-[3.3.1.13.7]decane and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane ligands were synthesized using Me3NO as an initiator. The data on antiproliferative activity of new compounds against ovarian carcinoma cell cultures A2780 (cisplatin-sensitive) and A2780cisR (cisplatin-resistant) are reported. The dependence of cytotoxicity on the number of phosphine ligands was demonstrated.

Generating Formulas of Transition Metal Carbonyl Clusters of Osmium, Rhodium and Rhenium

<p>The series for carbonyl clusters of transition metals have been developed. They may be considered to be formed with a fragment centered around the 14 electron valence content. The capping series are based on the fragment of 12 electron valence content. The formulas of clusters can be decomposed into series from which the shapes of clusters may be predicted. The electron counting numbers of carbonyl clusters can be identified.</p>

High nuclearity carbonyl clusters as near-IR contrast agents for photoacoustic in vivo imaging.

High nuclearity carbonyl clusters of ruthenium and osmium are found to exhibit good photoacoustic (PA) activity in the near-IR (NIR) region. Their potential as PA contrast agents for full body imaging has been demonstrated for the first time with mice; intravenous administration of the osmium carbonyl cluster Na2[Os10(μ6-C)(CO)24] afforded up to a four-fold enhancement of the PA signal in various tissues. The cluster exhibits low toxicity, high stability and superior PA stability compared to the clinically approved NIR dye, indocyanine green.

Oxidative Addition across Sb–H and Sb–Sb Bonds by an Osmium Carbonyl Cluster: Trapping the Intermediate

The cluster Os3(CO)11(NCCH3) oxidatively adds across the Sb–H bond in SbPh2H to afford the clusters Os3(CO)11(H)(μ-SbPh2) and Os3(CO)11(μ-H)(μ-SbPh2)Os3(CO)11. Similarly, its reaction with Sb2Ph4 afforded Os3(CO)11(μ-SbPh2)2Os3(CO)11 as the major product. In both cases, the intermediate from the oxidative addition reaction was trapped as a W(CO)5 adduct.

Organometallic carbonyl clusters: a new class of contrast agents for photoacoustic cerebral vascular imaging

We report, for the first time, the use of a water-soluble organometallic compound as a stable, reliable and high-contrast photoacoustic contrast agent. This gives a significantly higher contrast than that achievable with alternatives such as single-walled carbon nanotubes. Image enhancement of the rat cerebral cortex vasculature was observed using in vivo dark-field photoacoustic microscopy.

Metal Carbonyl–Gold Nanoparticle Conjugates for Live‐Cell SERS Imaging

Conjugates of organometallic osmium carbonyl clusters and gold nanoparticles show a strong carbonyl signal in surface-enhanced Raman spectroscopy. The ease of bio-functionalization and the high stability and good dispersibility in aqueous solution make these conjugates excellent candidates for biomedical applications, as demonstrated by live-cell imaging with the carbonyl signals of OM-NP(PEG)-L conjugates.

The effect of solvents on the stability of the products of electrochemical reactions of iron, ruthenium, and osmium carbonyl cluster compounds

The electrochemical reactions of carbonyl cluster compounds M3(CO)12 (M = Fe, Ru, Os) were compared with those of [Fe5C(CO)14]2− and [Fe6C(CO)16]2− in different aprotic solvents. The stability of electrochemically generated products of these clusters in the studied solvents was shown to grow in the following order: tetrahydrofuran < acetone < dichloromethane < acetonitrile.

Correction to Mechanism and Activation Parameters for the κO to μ,κ2O,O′ Bonding Mode of the Maleic Acid Ligand on an Osmium Carbonyl Cluster

Correction to Mechanism and Activation Parameters for the κ<i>O</i> to μ,κ²<i>O</i>,<i>O</i>′ Bonding Mode of the Maleic Acid Ligand on an Osmium Carbonyl Cluster

ChemInform Abstract: High Nuclearity Clusters and Beyond

Abstract Separate series of neutral and anionic osmium carbonyl clusters based on 3–20 osmium atoms have been prepared and characterised in the solid by single crystal X-ray analysis and in solution largely by 13 C NMR spectroscopy and vibrational analysis (IR). They appear to fall into two distinct series, viz ., those which follow a polytetrahedral, non-metallic growth sequence, e.g. [Os 3 (CO) 12 ] and [Os 3 (CO) 11 ] 2− , [Os 4 (CO) 14 ] and [Os 4 (CO) 13 ] 2− , [Os 5 (CO) 16 ] and [Os 5 (CO) 15 ] 2− , and [Os 6 (CO) 18 ] and [Os 6 (CO) 17 ] 2− , and those which apparently follow the route to bcc packing, e.g. [Os 6 (CO) 18 ] 2− , [Os 7 (CO) 21 ] and [Os 7 (CO) 20 ] 2− , [Os 8 (CO) 23 ] and [Os 8 (CO) 22 ] 2− , [Os 9 (CO) 24 ] 2− , [Os 10 (CO) 26 ] 2− and [Os 10 C(CO) 24 ] 2− , and [Os 20 (CO) 40 ] 2− . Alternatively, the species [Os 4 (CO) 14 ] and [Os 4 (CO) 13 ] 2− , [Os 10 (CO) 26 ] 2− and [Os 10 C(CO) 24 ] 2− and [Os 20 (CO) 40 ] 2− may be viewed as forming a ‘magic number’ sequence of clusters corresponding to the tetrahedral growth pattern, viz . 4, 10, and 20. Also described are the syntheses of mixed Os-C and Os-Hg clusters. The former bear a close resemblance to the carboranes in their structural features, whereas the Os-Hg clusters represent examples of linked cluster systems containing both transition metal and main group cluster domains. The geometric relevance that all these structures bear to the ‘metallic state’ is discussed.

Osmium Carbonyl Clusters on Gold and Silver Nanoparticles as Models for Studying the Interaction with the Metallic Surface

The surface−cluster interactions between four classes of clusters, viz., (i) those which may be expected to interact directly via the cluster core, (ii) those with a spacer carrying a free thiol functional group, (iii) those with a spacer carrying a free alcohol functional group, and (iv) those with a spacer carrying a free carboxylic acid functional group, with metallic substrate and nanoparticles of silver, and to a lesser extent gold, were examined and compared. In most cases, the clusters interact with both types of surfaces (substrate and nanoparticles) via the tethered functional group. However, cluster fragmentation is commonly observed to occur on the metallic nanoparticle surface.

Osmium Carbonyl Clusters Containing Labile Ligands Hyperstabilize Microtubules

A study into the possible molecular targets of the osmium carbonyl cluster Os(3)(CO)(10)(NCCH(3))(2) (2) in the ER- breast carcinoma (MDA-MB-231) cell line was carried out. Infrared and (1)H NMR analyses of cells treated with 2 showed the formation of carboxylato- and thiolato-bridged clusters from the interaction with intracellular carboxylic acid and sulfhydryl residues. The cytotoxicity of 2 was reduced in the presence of fetal bovine serum, and measurement with Ellman's reagent as well as fluorescence confocal microscopy with tetramethylrhodamine-5-maleimide staining all demonstrated binding to intracellular sulfhydryl groups leading up to cell disruption. Tubulin-FITC antibody staining of treated cells showed disruption of the microtubules, and a tubulin polmerization assay showed that 2 induced hyperstabilization of the microtubules.

The deposition of osmium carbonyl clusters onto inorganic oxide surfaces: A ToF-SIMS and IR spectroscopic study of the surface species

The interaction between the osmium clusters [Os 3(CO) 12], [Os 3(CO) 10(μ-H) 2], [Os 3(CO) 10(μ-H)(μ-OH)], and a series containing a free functional group, viz., [Os 3(CO) 10(μ-H)(μ- S ∧ EH )] (where = alkyl ∧ chain or an aromatic ring, E = COO, S or O), with SiO 2, ZnO and In 2O 3, was examined by ToF-SIMS and IR spectroscopy. While the interaction with the silica surface is mostly via an O atom or the functional group, the interaction with the ZnO and In 2O 3 surfaces is more complex.

Osmium Carbonyl Clusters: A New Class of Apoptosis Inducing Agents

Osmium carbonyl clusters, especially the cluster [Os(3)(CO)(10)(NCCH(3))(2)], were found to be active against four cancer cell lines, namely, ER+ breast carcinoma (MCF-7), ER- breast carcinoma (MDA-MB-231), metastatic colorectal adenocarcinoma (SW620), and hepatocarcinoma (Hep G2). The mode of action was studied in MCF-7 and MDA-MB-231 cell lines by a number of morphological and apoptosis assays, all of which pointed to the induction of apoptosis.

Ruthenium and osmium carbonyl clusters incorporating stannylene and stannyl ligands

The reaction of [Ru(3)(CO)(12)] with Ph(3)SnSPh in refluxing benzene furnished the bimetallic Ru-Sn compound [Ru(3)(CO)(8)(mu-SPh)(2)(mu(3)-SnPh(2))(SnPh(3))(2)] which consists of a SnPh(2) stannylene bonded to three Ru atoms to give a planar tetra-metal core, with two peripheral SnPh(3) ligands. The stannylene ligand forms a very short bond to one Ru atom [Sn-Ru 2.538(1) A] and very long bonds to the other two [Sn-Ru 3.074(1) A]. The germanium compound [Ru(3)(CO)(8)(mu-SPh)(2)(mu(3)-GePh(2))(GePh(3))(2)] was obtained from the reaction of [Ru(3)(CO)(12)] with Ph(3)GeSPh and has a similar structure to that of as evidenced by spectroscopic data. Treatment of [Os(3)(CO)(10)(MeCN)(2)] with Ph(3)SnSPh in refluxing benzene yielded the bimetallic Os-Sn compound [Os(3)(CO)(9)(mu-SPh)(mu(3)-SnPh(2))(MeCN)(eta(1)-C(6)H(5))] . Cluster has a superficially similar planar metal core, but with a different bonding mode with respect to that of . The Ph(2)Sn group is bonded most closely to Os(2) and Os(3) [2.786 and 2.748 A respectively] with a significantly longer bond to Os(1), 2.998 A indicating a weak back-donation to the Sn. The reaction of the bridging dppm compound [Ru(3)(CO)(10)(mu-dppm)] with Ph(3)SnSPh afforded [Ru(3)(CO)(6)(mu-dppm)(mu(3)-S)(mu(3)-SPh)(SnPh(3))] . Compound contains an open triangle of Ru atoms simultaneously capped by a sulfido and a PhS ligand on opposite sides of the cluster with a dppm ligand bridging one of the Ru-Ru edges and a Ph(3)Sn group occupying an axial position on the Ru atom not bridged by the dppm ligand.

New triosmium–iridium clusters: Synthesis and molecular structure of [Os 3Ir 2(Cp ∗) 2(μ-OH)(μ-CO) 2(CO) 8Cl] ( 1), [Os 3IrCp ∗(μ-OH)(CO) 10Cl] ( 2), [Os 3IrCp ∗(μ-H)(μ-Cl)(η 3,μ 3-C 5H 2N(NH 2)Br)(CO) 9] ( 3) and [Os 3IrCp ∗(μ-Cl) 2(η 2,μ 3-C 5H 3N(NH)Br)(CO) 7] ( 4)

The trinuclear osmium carbonyl cluster, [Os 3(CO) 10(MeCN) 2], is allowed to react with 1 equiv. of [IrCp ∗Cl 2] 2 (Cp ∗ = pentamethylcyclopentadiene) in refluxing dichloromethane to give two new osmium–iridium mixed-metal clusters, [Os 3Ir 2(Cp ∗) 2(μ-OH)(μ-CO) 2(CO) 8Cl] ( 1) and [Os 3IrCp ∗(μ-OH)(CO) 10Cl] ( 2), in moderate yields. In the presence of a pyridyl ligand, [C 5H 3N(NH 2)Br], however, the products isolated are different. Two osmium–iridium clusters with different coordination modes of the pyridyl ligand are afforded, [Os 3IrCp ∗(μ-H)(μ-Cl)(η 3,μ 3-C 5H 2N(NH 2)Br)(CO) 9] ( 3) and [Os 3IrCp ∗(μ-Cl) 2 (η 2,μ 3-C 5H 3N(NH)Br)(CO) 7] ( 4). All of the new compounds are characterized by conventional spectroscopic methods, and their structures are determined by single-crystal X-ray diffraction analysis.