Triosmium Carbonyl Clusters Research Articles

Copper carbene complexes. Synthesis and structural analysis of a chloro-bridged dicopper cation and the triosmium-copper carbene cluster complex HOs3(CO)11[µ-Cu(IPr)

The chloro-bridged carbene-substituted dicopper salt [{(IPr)Cu}2(µ-Cl)][PF6], 1, IPr = [N,N′-bis(2,6-diisopropylphenyl)imidazolin-2- ylidene], was synthesized by the reaction of (IPr)CuCl with Tl[PF6]. Reaction of 1 with the anion, [HOs3(CO)11]− of the salt [PPN][HOs3(CO)11], 2 yielded the Cu - Os heterometallic cluster complex, HOs3(CO)11[µ-Cu(IPr)], 3, the first example of Cu - Os bimetallic cluster complex containing a N-heterocyclic carbene ligand. Compounds 1 and 3 were characterized by IR, 1H NMR and structurally by single-crystal X-ray diffraction analysis. Compound 3 contains a triosmium carbonyl cluster with a bridging Cu(IPr) group on one edge of the cluster and a terminally-coordinated hydrido ligand on one of the Cu-bridged osmium atoms.

Towards understanding the mode of action of the cytotoxic triosmium carbonyl cluster Os3(CO)10(NCCH3)2: Its reactivity with amino acids and oligopeptides

The reactions of the triosmium carbonyl cluster Os3(CO)10(NCCH3)2 (1) with a number of protected amino acids, tri- and pentapeptides were examined. The results show that reaction with the side chains follow the order: -SH > -COOH > -CONH2, and there is a slight preference for the longer side chain of glutamic acid over aspartic acid. The trends observed are retained under physiological conditions and in the peptides.

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.

Double activation of the diphosphinite pincer proligand by a triosmium carbonyl cluster

The reaction between 1,3-bis(diphenylphosphinite)-benzene and Os3(CO)10(MeCN)2 affords complex Os3(CO)10[1,3-(PhPO)2C6H4]. A thermolysis of this cluster in refluxing toluene results in the activation of O–PPh2 and C–H bonds and the formation of unsaturated triosmium cluster Os3(μ-H)(μ-PPh2)(CO)7[(C6H3(O)(OPPh2)] that possesses a remarkable structure with the pseudo-pincer ligand containing a bridging μ-η1-aryl group.

Carboxylated Chalcone and Benzaldehyde Derivatives of Triosmium Carbonyl Clusters: Synthesis, Characterization and Biological Activity Towards MCF-7 Cells

The activated cluster Os3(CO)10(CH3CN)2 (1) reacts readily with a number of carboxylated chalcones and benzaldehydes (2a−j) to afford products with the general formula Os3(CO)10(µ-H)(µ-O2CR) (3a–j). The structures of all the novel clusters have been characterized by IR and 1H NMR spectroscopy, as well as mass spectrometry and elemental analysis. Single-crystal X-ray diffraction analysis has also been carried out for one of the carboxylated chalcones and two of the derivatized clusters. The activity of some of the derivatized clusters against the ER+ breast carcinoma MCF-7 cancer cell line has also been evaluated.

A dual-mode biosensor combining transition metal carbonyl-based SERS and a colorimetric readout for thiol detection

A fast SERS and colorimetric dual-modal assay for thiol detection was developed using a triosmium carbonyl cluster as a smart probe.

Opening of Carborane Cages by Metal Cluster Complexes: The Reaction of a Thiolate-Substituted Carborane with Triosmium Carbonyl Cluster Complexes

The reaction of Os3(CO)10(NCMe)2 with closo-o-(1-SCH3)C2B10H11 has yielded the complex Os3(CO)9[μ3-η(3)-C2B10H9(SCH3)](μ-H)2, 1, by the loss of the two NCMe ligands and one CO ligand from the Os3 cluster and the coordination of the sulfur atom and the activation of two B-H bonds with transfer of the hydrogen atoms to the cluster. Reaction of 1 with a second equivalent of Os3(CO)10(NCMe)2 yielded the complex Os3(CO)9(μ-H)[(μ3-η(3)-1,4,5-μ3-η(3)-6,10,11-C2B10H8S(CH3)]Os3(CO)9(μ-H)2, 2, that contains two triosmium triangles attached to the same carborane cage. The carborane cage was opened by cleavage of two B-C bonds and one B-B bond. The B-H group that was pulled out of the cage became a triply bridging group on one of the Os3 triangles but remains bonded to the cage by two B-B bonds. When heated to 150 °C, 2 was transformed into the complex Os3(CO)9(μ-H)[(μ3-η(3)-μ3-η(3)-C2B10H7S(CH3)]Os3(CO)9(μ-H), 3, by the loss of two hydrogen atoms and a rearrangement that led to further opening of the carborane cage. Reaction of 1 with a second equivalent of closo-o-(1-SCH3)C2B10H11 has yielded the complex Os3(CO)6)(μ3-η(3)-C2B10H9-R-SCH3) (μ3-η(3)-C2B10H10-S-SCH3)(μ-H)3, 4a, containing two carborane cages coordinated to one Os3 cluster. Compound 4a was isomerized to the compound Os3(CO)6(μ3-η(3)-C2B10H9-R-SCH3)(μ3-η(3)-C2B10H10-R-SCH3)(μ-H)3, 4b, by an inversion of stereochemistry at one of the sulfur atoms by heating to 174 °C.

Synthesis, Characterization and Electrochemistry of Some Metal Carbonyl Clusters Derived from Ferrocenylethynylpyridine

The chemical reactivity of ferrocenylethynylpyridine ligand with some metal complexes has been studied. Ligation of this ferrocenyl-functionalized pyridyl metalloligand with triosmium carbonyl cluster [Os3(CO)10(NCMe)2] via oxidative addition led to a new supramolecular heterobimetallic cluster [Os3(CO)10(μ-H){μ-NC5H3C≡C(η5-C5H4)Fe(η5-C5H5)}] 1 in good yield. Coordination of Co2(CO)8 with the alkyne functionality of 1 gave another new heterotrimetallic cluster complex [Os3(CO)10(μ-H){μ-NC5H3{C2Co2(CO)6}(η5-C5H4)Fe(η5-C5H5)}] 2 in which the molecule possesses a Co2C2 core adopting the pseudo-tetrahedral geometry having the alkyne bond lying perpendicular to the Co–Co vector. Characterization of 1 and 2 by IR and 1H NMR spectroscopies indicated that these complexes consist of an orthometalated trinuclear carbonyl cluster unit rigidly connected to a ferrocenyl unit. Electrochemical studies on 1 and 2 revealed that both of them undergo a reversible one-electron oxidation at iron followed by an irreversible oxidation of the Os3 cluster core. Another simple mononuclear zinc(II) complex [ZnCl2{(NC5H4C≡C(η5-C5H4)Fe(η5-C5H5)}2] 3 was also prepared for comparison of the electrochemical data with those of 1 and 2.

Cytotoxic Triosmium Carbonyl Clusters: A Structure–Activity Relationship Study

A structure-activity relationship (SAR) study of the triosmium carbonyl cluster Os3 (CO)10 (NCCH3 )2 was carried out with a series of clusters of the general formula Os3 (CO)12-n Ln , cationic osmium clusters and a hemi-labile maltolato-Os cluster. The SAR results showed that good solubility in DMSO and at least one vacant site are required for cytotoxicity. In vitro evaluation of these new compounds showed that some are selectively active against estrogen receptor (ER)-independent MDA-MB-231 breast cancer cell lines relative to ER-dependent MCF-7 breast cancer cells, suggesting that the compounds have a different biological target specific to MDA-MB-231 cells. In particular, the maltolato cluster exhibits strong antiproliferative activity, with an IC50 value of 3 μM after only 24 h incubation. Additionally, biochemical assays conducted with the cationic cluster show that it induces apoptosis, although a biological target has not yet been identified. Further research to establish the molecular targets of these compounds and to develop improved organometallic clusters as potential breast cancer therapeutics is underway.

Unsaturated Triosmium Carbonyl Cluster Complexes with Bridging Aryl Ligands: Structures, Bonding, and Transformations

Reactions of Os3(CO)10(NCMe)2, 1, with the series of aryl-gold complexes ArylAu(PPh3) [Aryl = phenyl = Ph, 2-naphthyl = 2-Np (2-C10H7) and 1-pyryl (1-C16H10)] have provided the series of electronically unsaturated triosmium complexes Os3(CO)10(μ-η1-Ar)(μ-AuPPh3) [2, Ar = phenyl = Ph; 3, Ar = 2-naphthyl = 2-Np (2-C10H7); and Ar = 4 and 5, 2-pyryl and 4-pyryl], containing bridging η1-Ar ligands and a bridging Au(PPh3) group that bridges the same unsaturated Os–Os bond in the 46-electron cluster complex. All new compounds were characterized by single-crystal X-ray diffraction analyses. A DFT computational analysis of 2 has revealed that bonding of the bridging phenyl ligand to the metal atoms consists of a combination of delocalized σ-bonding between the ipso-carbon atom and the two proximate metal atoms and π-donation from the π-orbitals of the ring to those same metal atoms. There is no significant metal to ring π-back-bonding. Compound 3 exists as two isomers, 3a and 3b. Compound 3a contains a μ-η1-2-Np l...

Direct Evidence for the Attack of a Free N‐Heterocyclic Carbene at a Carbonyl Ligand: A Zwitterionic Osmium Carbonyl Cluster

A key suspect arrested: The initial site of attack of a free N-heterocyclic carbene (NHC) on the triosmium carbonyl cluster [Os3(CO)12] was found to be a carbonyl ligand. The stable zwitterionic species thus formed (blue background in the scheme) was characterized crystallographically. CO substitution proceeds from this intermediate by the loss of a CO group and migratory deinsertion.

Hydride Dynamics in Triosmium and Triruthenium Carbonyl Clusters: Synthesis, Reactivity and Dynamics of a Trihydrido Quinoline-4-Carboxaldehyde Triosmium Cluster

An overview of the dynamical processes involving the hydrido ligand in triosmium and triruthenium carbonyl clusters is presented. The relationship between the mechanisms of hydride motions and the other ligands in the cluster are discussed for mono- di- and trihydrido-clusters. In addition, the reactivity of the electron deficient 46e− cluster, (μ-H)(μ3-η2-C9H5N-4-CHO)Os3(CO)9 (1) with hydrogen is reported. The reaction gives two isomeric trihydrido clusters, H(μ-H)2(μ3-η2-C9H5N-4-CHO)Os3(CO)8 (2) and (μ-H)3(μ3-η2-C9H5N-4-CHO)Os3(CO)8 (2′) in low yield along with trace amounts of other hydrido clusters. Reaction of the inseparable mixture of 2 and 2′ with triphenylphosphine at ambient temperatures gives two related addition products H(μ-H)2(μ-η2-C9H5N-4-CHO)Os3(CO)8PPh3 (3) and (μ-H)3(μ-η2-C9H5N-4-CHO)Os3(CO)8PPh3 (3′) in a 5:1 ratio. These results contrast with the previously reported trihydrido-derivatives of triosmium μ3-η2-imidoyl clusters where only analogues of 2 and 3 are obtained. Clusters 2 and 2′ are rigid on the NMR time scale while 3 exhibits dynamical behavior in the temperature range of −50 to +25 °C. Cluster 3′ is stereochemically rigid in this temperature range. The dynamical behavior of 3 involves the exchange of the terminal and bridging hydrides coupled with tripodal motion of the phosphine substituted osmium atom, a process virtually identical to previously reported trihydrides of the μ3-η2-imidoyl triosmium clusters.

Complexation and activation of the bisfulleroid C64H4 with triosmium carbonyl clusters

Reaction of C64H4 (1) and Os3(CO)10(NCMe)2 in refluxing chlorobenzene affords (μ-H)Os3(CO)9(μ,η4-C64H3) (2) and Os(CO)3(η4-C64H4) (3). Compound 2 apparently arises from C–H bond activation of 1 to generate an η4-dienyl motif. In contrast, compound 3 is produced by insertion of one osmium atom into a pentagonal ring of 1, together with the Os3 cluster fragmentation. Complexes 2 and 3 have been characterized by IR, NMR, and mass spectroscopies. The structure of 3·C7H8 was determined by a single-crystal X-ray diffraction study.

Synthesis, Characterization and Structural Properties of Some Heterobimetallic Carbonyl Clusters Derived from Diethynylsilane and Diethynyldisilane Ligands

We report the synthesis of some heterobimetallic carbonyl clusters of groups 8 and 9 derived from diethynylsilane and diethynyldisilane ligands. The triosmium carbonyl clusters containing a pendant acetylene unit [(μ-CO)Os3(CO)9(μ3-η2-HC≡C-E-C≡CH)] [E = Si(CH3)2, Si(CH3)2–Si(CH3)2 and SiPh2] were prepared and subsequently used for mixed-metal cluster formation. New diyne complexes of the type [{(μ-CO)Os3(CO)9}{Co2(CO)6}(μ3-η2:η2-diyne)] and [{(μ-CO)Os3(CO)9}{(μ-H)Ru3(CO)9}(μ3-η2:μ3-η2, η2-diyne)] [diyne = HC≡CSi(CH3)2C≡CH, HC≡CSi(CH3)2–Si(CH3)2C≡CH or HC≡CSi(Ph)2C≡CH] have been prepared in good yields from the reaction of [(μ-CO)Os3(CO)9(μ3-η2-HC≡C-E-C≡CH)] with a molar equivalent of [Co2(CO)8] and [Ru3(CO)12], respectively. All the new heterobimetallic compounds have been characterized by IR and 1H NMR spectroscopy and mass spectrometry. The X-ray crystal structures and computational analyses based on density functional theory of these three molecules have been studied. Structurally, the dicobalt species adopts a pseudo-tetrahedral Co2C2 core with the alkyne bond which lies essentially perpendicular to the Co–Co vector. For the mixed osmium–ruthenium analogue, the hexanuclear carbonyl cluster consist of two trinuclear metal cores with the μ3-(η2-||) bonding mode for the acetylene group in the former case and the μ3-η2, η2 bonding mode in the latter one.

Complexation and C–H bond activation of 2,2′:6′,2″-terpyridyl molecules on triosmium carbonyl clusters: Synthesis and characterization of the double-cluster {Cp 3Fe 4(CO) 4(C 5H 4-terpyridyl)Os 3( μ-H)(CO) n} ( n = 9, 10)

Cp 3Fe 4(CO) 4(4′-C 5H 4-2,2′:6′,2″-terpyridine) (abbreviated as Fe 4tpyH) reacts with Os 3(CO) 10(NCMe) 2 in hot methylcyclohexane to generate the double cluster ( μ-H)Os 3( μ, η 2-Fe 4tpy)(CO) 10 ( 1) and ( μ-H)Os 3( μ, η 3-Fe 4tpy)(CO) 9 ( 2). Similar reaction of 4′-( p-FC 6H 4)-2,2′:6′,2″-terpyridine (abbreviated as FtpyH) and Os 3(CO) 10(NCMe) 2 affords ( μ-H)Os 3( μ, η 2-Ftpy)(CO) 10 ( 3) and ( μ-H)Os 3( μ, η 3-Ftpy)(CO) 9 ( 4). On the other hand, treating the pristine molecule 2,2′:6′,2″-terpyridine (abbreviated as TpyH) with Os 3(CO) 10(NCMe) 2 only isolates ( μ-H)Os 3( μ, η 2-Tpy)(CO) 10 ( 5). These compounds are generated by complexation and C–H bond activation of pyridyl groups on triosmium framework, and have been characterized by IR, NMR, and mass spectroscopies. The structure of 4 is determined by a single-crystal X-ray diffraction study.

Theoretical topological analysis of the electron density in a series of triosmium carbonyl clusters: [Os 3(CO) 12], [Os 3(μ-H) 2(CO) 10], [Os 3(μ-H)(μ-OH)(CO) 10], and [Os 3(μ-H)(μ-Cl)(CO) 10

A number of local and integral topological parameters of the electron density for the triosmium triangular carbonyl clusters [Os 3(CO) 12] ( 1), [Os 3(μ-H) 2(CO) 10] ( 2), [Os 3(μ-H)(μ-OH)(CO) 10] ( 3), and [Os 3(μ-H)(μ-Cl)(CO) 10] ( 4) have been calculated and interpreted under the perspective of the relativistic and non-relativistic Quantum Theory of Atoms in Molecules (QTAIM). These results have allowed a comparison between topological properties of related but different atom–atom interactions, such as different Os–Os bond orders, H-bridged versus X-bridged (X = OH, Cl) and ligand-unbridged Os–Os interactions, and Os–H versus Os–OH and Os–Cl interactions. For compound 1, an interaction of 3c–2e type between the three metal atoms has been found. The local topological parameters of the unbridged Os–Os bonds in compound 2 differ considerably from those of the bridged Os–Os bond, for which a bond path was nevertheless observed. The calculated topological indexes indicate that bridging OH and Cl ligands are more efficient than bridging hydride ligands in delocalizing the electron density of bridged metal atoms; in fact, no direct bond path has been found for the interaction between bridged Os atoms in 3 or 4, although a non-negligible delocalization index δ(Os⋯Os) has been obtained for these non-bonding interactions. A multicenter 4c–4e interaction is proposed to exist in the bridged parts, Os 2(μ-H)(μ-X) (X = H ( 2), OH ( 3), Cl ( 4)), of compounds 2– 4. Compared with compound 2, the smaller electron density shared by the bridged Os atoms in compounds 3 and 4 is compensated by a greater electron density shared by the atoms in Os–X (X = O, Cl) bonds.

Complexes containing bridging tin- and germanium-substituted metallocarboxylate ligands from the reactions of Ph 3SnOH and Ph 3GeOH with Os 3(CO) 12 in the presence of base

The first examples of bridging tin- and germanium-substituted metallocarboxylate ligands have been obtained from the reactions of Ph 3SnOH and Ph 3GeOH with Os 3(CO) 12 under basic conditions. Two products: Os 3(CO) 10(μ-η 2-O=COSnPh 3)(μ-OMe), 1 (18% yield) and Os 3(CO) 10(μ-OMe)(μ-OH), 2 (6.9% yield) were obtained from the reaction of Ph 3SnOH with Os 3(CO) 12 in the presence of [Bu 4N]OH in methanol solvent. The compound Os 3(CO) 10(μ-η 2-O=COGePh 3)(μ-OMe), 3 (7.3% yield) was prepared similarly by using Ph 3GeOH in place of Ph 3SnOH. Each of the products 1– 3 were characterized structurally by single-crystal X-ray diffraction analysis. Compounds 1 and 3 each contain an μ-η 2-O=COMPh 3, M = Sn or Ge ligand bridging a pair of osmium atoms in a triosmium carbonyl cluster complex.

Fluorous triosmium clusters. Preparation, properties, and reactivity of Os 3(CO) 11{P(CH 2CH 2(CF 2) 5CF 3) 3} and Os 3(CO) 10{P(CH 2CH 2(CF 2) 5CF 3) 3} 2. Crystal structure of Os 3(CO) 9(PPh 3) 2{P(CH 2CH 2(CF 2) 5CF 3) 3}. Ring opening metathesis polymerization of norbornene by (μ-H) 2Os 3(CO) 9{P(C 6H 4-4-CH 2CH 2(CF 2) 7CF 3)

Several fluorous phosphine ligand triosmium carbonyl cluster derivatives, e.g., Os 3(CO) 11{P(CH 2CH 2(CF 2) 5CF 3) 3} ( 1) and Os 3(CO) 10{P(CH 2CH 2(CF 2) 5CF 3) 3} 2 ( 2) have been synthesized in order to assess their properties in fluorocarbon, or fluorous, phases. Cluster 1 reacts with PPh 3 above 100 °C to substitute one or two carbonyl ligands and provide the mixed ligand derivatives Os 3(CO) 10(PPh 3){P(CH 2CH 2(CF 2) 5CF 3) 3}, ( 3) and Os 3(CO) 9(PPh 3) 2{P(CH 2CH 2(CF 2) 5CF 3) 3}, ( 4). The crystal structure of 4 has been determined by single crystal X-ray diffraction. At circa 102 °C and 1 atm H 2, 1 will form the unsaturated compound (μ-H) 2Os 3(CO) 9{P(CH 2CH 2(CF 2) 5CF 3) 3} ( 5) in modest yield. Compound 5 and the related compound (μ-H) 2Os 3(CO) 9{P(C 6H 4-4-CH 2CH 2(CF 2) 7CF 3) 3} ( 6) are obtained more cleanly by treating (μ-H) 2Os 3(CO) 10 with the corresponding fluorous phosphine ligand at room temperature followed by decarbonylation in refluxing hexane. Compounds 1– 6 have been characterized by employment of IR and 1H NMR and 31P NMR spectroscopy. Partition coefficients between fluorous and non-fluorous solvents have been determined. The use of 6 as a ROMP catalyst with norbornene in a variety of organic and universal solvents is described.

Reaction of multifunctional molecule (Ph 2P( o-C 6H 4)CH [dbnd]NCH 2CH 2) 3N with triosmium carbonyl clusters

Reaction of (Ph 2P( o-C 6H 4)CH NCH 2CH 2) 3N with 3 equiv. of Os 3(CO) 10(NCMe) 2 at ambient temperature affords the triple cluster [Os 3(CO) 10Ph 2P( o-C 6H 4)CH NCH 2CH 2] 3N ( 1) through coordination of the phosphine and imine groups. Thermolysis of 1 in benzene leads to decarbonylation and C–H/C–N bond activation of the ligand to generate (μ-H)Os 3(CO) 8(μ 3-Ph 2P( o-C 6H 4)CH NC CH 2) ( 2). The molecular structure of 2 has been determined by an X-ray diffraction study.

Complexation and metallation of Ph 2PC [tbnd]C(CH 2) 5C [tbnd]CPh 2 in triosmium carbonyl clusters

Reaction of Ph 2PC C(CH 2) 5C CPh 2 with Os 3(CO) 10(NCMe) 2 affords Os 3(CO) 10(μ,η 2-(Ph 2P) 2C 9H 10) ( 1) and the double cluster [Os 3(CO) 10] 2(μ,η 2- (Ph 2P) 2C 9H 10) 2 ( 2), through coordination of the phosphine groups. Thermolysis of 1 in toluene generates Os 3(CO) 7(μ-PPh 2)(μ 3,η 5-Ph 2PC 9H 10) ( 3) and Os 3(CO) 8(μ-PPh 2)(μ 3,η 6-Ph 2P(C 9H 10)CO) ( 4). The molecular structures of 1, 3, and 4 have been determined by an X-ray diffraction study. Both 3 and 4 contain a bridging phosphido group and a carbocycle connected to an osmacyclopentadienyl ring, which are apparently derived from C–P bond activation and C–C bond rearrangement of the dpndy ligand governed by the triosmium clusters.