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The series of complexes [XRu(CO)(L–L)(L′)2][PF6] (X = H, TFA, Cl; L–L = 2,2′-bipyridyl, 1,10-phenanthroline, 5-amino-1,10-phenanthroline and 4,4′-dicarboxylic-2,2′-bipyridyl; L′2 = 2PPh3, Ph2PC2H4PPh2, Ph2PCH＝CHPPh2) have been synthesized from the starting complex K[Ru(CO)3(TFA)3] (TFA = CF3CO2) by first reacting with the phosphine ligand, followed by reaction with the L–L and anion exchange with NaPF6. In the case of L–L = phenanthroline and L′2 = 2PPh3, the neutral complex Ru(Ph3P)(CO)(1,10-phenanthroline)(TFA)2 is also obtained and its solid state structure is reported. Solid state structures are also reported for the cationic complexes where L–L = phenanthroline, L2 = 2PPh3 and X = Cl and for L–L = 2,2′-bipyridyl, L2 = 2PPh3 and X = H. All the complexes were characterized in solution by a combination of 1H and 31P NMR, IR, mass spectrometry and elemental analyses. The purpose of the project was to synthesize a series of complexes that exhibit a range of excited-state lifetimes and that have large Stokes shifts, high quantum yields and high intrinsic polarizations associated with their metal-to-ligand charge-transfer (MLCT) emissions. To a large degree these goals have been realized in that excited-state lifetimes in the range of 100 ns to over 1 μs are observed. The lifetimes are sensitive to both solvent and the presence of oxygen. The measured quantum yields and intrinsic anisotropies are higher than for previously reported Ru(II) complexes. Interestingly, the neutral complex with one phosphine ligand shows no MLCT emission. Under the conditions of synthesis some of the initially formed complexes with X = TFA are converted to the corresponding hydrides or in the presence of chlorinated solvents to the corresponding chlorides, testifying to the lability of the TFA Ligand. The compounds show multiple reduction potentials which are chemically and electrochemically reversible in a few cases as examined by cyclic voltammetry. The relationships between the observed photophysical properties of the complexes and the nature of the ligands on the Ru(II) is discussed. [Copyright &y& Elsevier]

Abstract: Treatment of unsaturated [Os3(CO)8{μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] (2) with t BuNC at room temperature gives [Os3(CO)8(CNBu t )){μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] (3) which on thermolysis in refluxing toluene furnishes [Os3(CO)7(CNBu t ){μ3-Ph2PCHP(Ph)C6H4}(μ-H)2] (4). Reaction of the labile complex [Os3(CO)9(μ-dppm)(NCMe)] (5) with t BuNC at room temperature affords the substitution product [Os3(CO)9(μ-dppm)(CNBu t )] (6). Thermolysis of 6 in refluxing toluene gives 4. On the other hand, the reaction of unsaturated [Os3(CO)9{μ3-η2-C7H3(2-Me)NS}(μ-H)] (7) with t BuNC yields the addition product [Os3(CO)9(CNBu t ){μ-η2-C7H3(2-Me)NS}(μ-H)] (8) which on decarbonylation in refluxing toluene gives unsaturated [Os3(CO)8(CNBu t ){μ3-η2-C7H3(2-Me)NS}(μ-H)] (9). Compound 9 reacts with PPh3 at room temperature to give the adduct [Os3(CO)8(PPh3)(CNBu t ){μ-η2-C7H3(2-Me)NS(μ-H)] (10). Compound 8 exists as two isomers in solution whereas 10 occurs in four isomeric forms. The molecular structures of 3, 6, 8, and 10 have been determined by X-ray diffraction studies. [Copyright &y& Elsevier]

Abstract: The reactions of 2-amino-anthracene with [Os3(CO)10(CH3CN)2] have been studied and the products structurally characterized by spectroscopic, X-ray diffraction, photophysical and electrochemical techniques. At room temperature in CH2Cl2 two major, isomeric products are obtained [Os3(CO)10(μ-η2-(N-C(1))-NH2C14H8)(μ-H)] (1, 14%) and [Os3(CO)10(μ-η2-(N-C(3))-NHC14H9)(μ-H)] (2, 35%) along with a trace amount of the dihydrido complex [Os3(CO)9(μ-η2-(N-C(3))-NHC14H8)(μ-H)2] (3). In refluxing tetrahydrofuran only complexes 2 and 3 are obtained in 24% and 28%, respectively. A separate experiment shows that complex 1 slowly converts to 2 and that the rearrangement is catalyzed by adventitious water and involves proton transfer to the anthracene ring. Complex 1 is stereochemically non-rigid; exhibiting edge to edge hydride migration while 2 is stereochemically rigid. Complex 3 is also stereochemically non-rigid showing a site exchange process of the magnetically nonequivalent hydrides typical for trinuclear dihydrides. Interestingly, 2 decarbonylates cleanly to the electronically unsaturated 46e− cluster [Os3(CO)9(μ3-η2-(N-C(3))-NHC10H9)(μ-H)] (4, 68%) in refluxing cyclohexane, while photolysis of 2 in CH2Cl2 yields only a small amount of 3 along with considerable decomposition. The mechanism of the conversion of 1 to 2 and the dependence of the product distribution on solvent are discussed. All four compounds are luminescent with compounds 1–3 showing emissions that can be assigned to radiative decay associated with the anthracene ligand. Complexes 1–3 all show irreversible 1e− reductions in the range of −1.85–2.14V while 4 shows a nicely reversible 1e− wave at −1.16V and a quasi-reversible second 1e− wave at −1.62V. Irreversible oxidations are observed in the range from +0.35 to +0.49V. The relationship between the cluster ligand configurations and the observed electrochemical and photochemical behavior is discussed and compared with that of the free ligand. [Copyright &y& Elsevier]

The complex [Ru(tpy)(CO)2TFA]+[PF6]- (where tpy = 2,2′:6′,2″-terpyridine and TFA = CF3CO2-) (1) has been synthesized and fully characterized spectroscopically. The X-ray structure of the complex has been determined. The photopysical properties of the ruthenium complex and the free ligand tpy have been investigated at room temperature and at 77 K in acetonitrile solution and in the solid state. Their electronic spectra are highly influenced by intermolecular stacking interactions, both in solution and in the solid state. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been performed to characterize the electronic structure and the excited states of [Ru(tpy)(CO)2TFA]+[PF6]- and tpy. TDDFT calculations on three different conformations of free ligand have been performed as well. Absorption and emission spectra of tpy have been studied at different temperatures and concentrations in order to have a better understanding of this ruthenium derivative's properties. The absorption spectrum of 1 is characterized by metal-perturbed ligand-centered (LC) bands in the UV region. No metal-to-ligand charge transfer (MLCT) bands are observed in the visible for the complex. Only at high concentrations (10-4 M) does a very weak band appear at 470 nm. At 77 K and low concentrations, solutions of 1 exhibit a major 3LC emission band centered at 468 nm (21.4 × 10-3 cm-1). When the concentration of the complex is increased, an unstructured narrow emission at 603 nm (16.6 × 10-3 cm-1), with a lifetime of 10 μs, dominates the emission spectrum in glassy acetonitrile. This emission originates from a π-π stacked dimeric (or oligomeric) species. TDDFT calculations performed on a tail-to-tail dimer structure, similar to that seen in the solid state, ascribe the transition to a triplet excited state, where intermolecular metal (d) → ligand (π*, polypyridine) charge transfer occurs. A good estimate of the transition energy is also obtained (623 nm, 1.94 eV). [ABSTRACT FROM AUTHOR]

Abstract: We report a combined experimental and computational study of new rhenium tricarbonyl complexes based on the bidentate heterocyclic N–N ligands 2-(4-methylpyridin-2-yl)benzo[d]-X-azole (X=N–CH3, O, or S) and 2-(benzo[d]-X-azol-2-yl)-4-methylquinoline (X=N–CH3, O, or S). Two sets of complexes are reported. Chloro complexes, described by the general formula Re(CO)3[2-(4-methylpyridin-2-yl)benzo[d]-X-azole]Cl (X=N–CH3, 1; X=O, 2; X=S, 3) and Re(CO)3[2-(benzo[d]-X-azol-2-yl)-4-methylquinoline]Cl (X=N–CH3, 4; X=O, 5; X=S, 6) were synthesized heating at reflux Re(CO)5Cl with the appropriate N–N ligand in toluene. The corresponding pyridine set {Re(CO)3[2-(4-methylpyridin-2-yl)benzo-X-azole]py}PF6 (X=N–CH3, 7; X=O, 8; X=S, 9) and {Re(CO)3[2-(benzo[d]-X-azol-2-yl)-4-methylquinoline]py}PF6 (X=N–CH3, 10; X=O, 11; X=S, 12) was synthesized by halide abstraction with silver nitrate of 1–6 followed by heating in pyridine and isolated as their hexafluorophosphate salts. All complexes have been fully characterized by IR, NMR, electrochemical techniques and luminescence. The crystal structures of 1 and 7 were obtained by X-ray diffraction. DFT and time-dependent (TD) DFT calculations were carried out for investigating the effect of the organic ligand on the optical properties and electronic structure of the reported complexes. [Copyright &y& Elsevier]

The density functional theory method has been applied to gain insights into the regioselectivity of nucleophilic attack and protonation of electron-deficient benzoheterocycle triosmium clusters. We report our computational results on the reaction of the green 46-electron triosmium clusters Os3(CO)9(μ3-η²-(LH))(μ-H) (L = benzoxazole, 1a; benzothiazole, 1b; dihydroquinoline, 1c; 1,3-dehydroindoline, 1d; 4H-3,1-benzoxazine, 1e) with hydride (H-) and proton (H+) in order to elucidate factors affecting the observed differences in the structure of the kinetic products of these reactions. Transition-state calculations for the interconversion of the anionic tautomers resulting from H- attack on the clusters 1a-e show that the activation energies of these anionic clusters are considerably lower than the previously reported barriers for related neutral clusters. Calculations also reveal that the structures of the kinetic products resulting from sequential H-/H+ attack are determined by the protonation process. [ABSTRACT FROM AUTHOR]

Abstract: Treatment of [(μ-H)Os3(CO)10(μ-OMe)] (1) with dppm {dppm=bis(diphenylphosphino)methane} at 110°C gave the known compound [Os3(CO)10(μ2-η2-dppm)] (2) and the new compound [(μ-H)Os3(CO)8(μ-OMe)(μ2-η2-dppm)] (3). A similar reaction of 1 with dppe {dppe=bis(diphenylphosphino)ethane} afforded two products, [(μ-H)Os3(CO)8(μ-OMe)(μ1-η2-dppe)] (5) and [(μ-H)Os3(CO)8(μ-OMe)(μ2-η2-dppe)] (6) which differ in the mode of bonding of the dppe ligand. The reaction of 1 with dppp {dppp=bis(diphenylphosphino)propane} at 110°C gave exclusively [(μ-H)Os3(CO)8(μ-OMe)(μ2-η2-dppp)] (7) which exists as two isomers in solution. Compounds 2, 3, and 5–7 are also obtained in almost similar yields from reactions of [(μ-H)Os3(CO)9(μ-OMe)(MeCN)] (4) with the appropriate diphosphine at ambient temperature. The reaction of 1 with PPh2H at 110°C gave the new compounds [(μ-H)Os3(CO)9(μ-OMe)(PPh2H)] (8) and [(μ-H)2Os3(CO)7(μ-PPh2)2(PPh2H)] (10) and the previously reported compound [(μ-H)2Os3(CO)8(μ-PPh2)2] (9). The molecular structures of 3 and 8 were determined by single crystal X-ray diffraction. In compound 3, the dppm ligand bridges the same Os–Os edge as the hydride and the methoxide ligand. In 8, the PPh2H ligand occupies a ‘pseudo’ axial site on one of the osmium atoms bearing the bridging hydride and methoxide ligand. [Copyright &y& Elsevier]

Abstract: Heating [Os3(CO)10(μ-dppm)] (1) with two equivalents of PhSSPh in toluene under reflux provided three new triosmium compounds [(μ-H)Os3(CO)7(μ-SPh){μ3-η4-Ph2PCHP(Ph)C6H4}] (2), [Os3(CO)8(μ-SPh)2(μ-dppm)] (3) and [(μ-H)Os3(CO)7(μ-η2-SC6H4)(μ-SPh)(μ-dppm)] (4) in 20%, 21% and 26% yields, respectively. In contrast, a similar reaction of 1 with two equivalents of PhTeTePh in refluxing toluene gave the binuclear compound [Os2(CO)4(μ-TePh)2(μ-dppm)] (6) in 15% yield, and two 50 electron isomeric compounds 5 and 7 with the formula [Os3(CO)8(μ-TePh)2(μ-dppm)] in 20% and 23% yields, respectively. Thermolysis of 3 at 110°C afforded 4 in 53% yield which on further thermolysis in refluxing octane at 128°C gave 2 in 45% yield. Thermolysis of 3 in refluxing octane also gave 2 in 50% yield. The new compounds, 2–7, were all spectroscopically characterized, and the X-ray structures of 2, 3 and 7 have been determined. Compound 2 contains a bridging SPh ligand and a μ3,η4-Ph2PCHP(Ph)C6H4 ligand, formed by two kinds of C–H activation, including orthometallation of a phenyl group as well as an unusual activation of the methylene group of the dppm ligand. The molecular structure of 3 reveals that two SPh groups span the open Os–Os edge of the Os3 triangle, while the dppm ligand bridges one of the closed Os–Os edges. In compound 7, one TePh group spans the open Os–Os edge, while the other spans one of the two closed Os–Os edges and the dppm ligand bridges the third Os–Os vector. [Copyright &y& Elsevier]

Treatment of Mn2(CO)10 with 3,4-toluenedithiol and 1,2-ethanedithiol in the presence of Me3NO·2H2O in CH2Cl2 at room temperature afforded the dinuclear complexes Mn2(CO)6(μ-ρ4-SC6H3(CH3)S-SC6H3(CH3)S) (1), and Mn2-(CO)6(μ-ρ4-SCH2CH2S-SCH2CH2S) (2), respectively. Similar reactions of Re2(CO)10 with 3,4-toluenedithiol, 1,2-benzenedithiol, and 1,2-ethanedithiol yielded the dirhenium complexes Re2(CO)6(μ-ρ4.SC6H3(CH3)S-SC6H3(CH3)S) (3), Re2(CO)6(μ-ρ4-SC6H4S-SC6H4S) (4), and Re2(CO)6(SCH2CH2S-SCH2CH2S) (5), respectively. In contrast, treatment of Mn2(CO)10 with 1,3-propanedithiol afforded the trimanganese compound Mn3(CO)6(μ-ρ2-SCH2CH2-CH2S)3 (6), whereas Re2(CO)10 gave only intractable materials. The molecular structures of 1, 3, and 6 have been determined by single-crystal X-ray diffraction studies. The dimanganese and dirhenium carbonyl compounds 1–5 contain a binucleating disulfide ligand, formed by interligand disulfide bond formation between two dithiolate ligands identical in structure to that of the previously reported dimanganese complex Mn2(CO)6(μ-ρ4-SC6H4S-SC6H4S). Complex 6, on the other hand, forms a unique example of a mixed-valenca trimangenese carbonyl compound containing three bridging 1,3-propanedithiolate ligands. The solution properties of 6 have been investigated by UV-vis and EPR spectroscopies as well as electrochemical techniques. [ABSTRACT FROM AUTHOR]

Abstract: Treatment of the electronically unsaturated cluster [(μ-H)Os3(CO)8(Ph2PCH2P(Ph)C6H4)] (1) with HCl gas at ambient temperature in dichloromethane afforded (μ-H)Os3(CO)8(μ-Cl)(μ-dppm) (2) and [(μ-H)Os3(CO)7(η1-Cl)(μ-Cl)2(μ-dppm)] (3). Thermolysis of 2 at 110 °C led to an isomer of 2, 4. A similar reaction of 1 with HBr gas gave [(μ-H)Os3(CO)8(μ-Br)(μ-dppm)] (5) as the only product which does not isomerize at 110 °C. In sharp contrast, treatment of 1 with HF gas gave the protonated species [(μ-H)2Os3(CO)8(Ph2PCH2P(Ph)C6H4)]+ (6). Treatment of 1 with CF3CO2H also gave cation 6 whereas CH3CO2H yielded [(μ-H)Os3(CO)8(μ-η2-CH3CO2)(μ-dppm)] (7). Structures of 2, 3, 4 and 6 were established crystallographically. In 2, both the chloride and the hydride ligands simultaneously bridge the same Os–Os edge and the dppm spans another Os–Os bond whereas in 4, all the three ligands bridge the same Os–Os edge. Compound 3 is comprised of an open Os3 arrangement in which one chloride bridges the open Os⋯Os edge, another chloride and a hydride mutually bridge an Os–Os bond and the third chloride is terminally coordinated to one of the Os atoms of the dppm bridged edge. The cation 6 consists of a triangle of osmium atoms in which the shortest Os–Os edge is bridged by a hydride and the metallated phenyl ring and the longest edge is bridged by another hydride and the diphosphine ligand. [Copyright &y& Elsevier]

Abstract: We have studied the ability of several bioorganometallic clusters [(μ-H)Os3(CO)9(L)(μ3-η2-(Q-H))], where L=[P(C6H4SO3Na)3] or [P(OCH2CH2NMe3I)3], and Q=quinoline, 3-aminoquinoline, quinoxaline or phenanthridine, of inhibiting telomerase, a crucial enzyme for cancer progression. In general, quinolines have shown interesting biological properties, especially in inhibiting enzymes. For example, the 2,3,7-trichloro-5-nitroquinoxaline (TNQX) exhibited strong anti-telomerase activity in vitro. Among the quinoline-clusters under study, only the negatively charged ones (by virtue of the sulfonated phosphines) exhibited good anti-telomerasic activity on semi-purified enzyme in a cell-free assay, while they were ineffective in vitro on Taq, a different DNA-polymerase. On the contrary, the treatment of breast cancer MCF-7 cell line did not evidence any activity of these clusters, suggesting a low aptitude for crossing cell membrane. Furthermore, all clusters exhibited non-specific, acute cytotoxicy, probably due to accumulation on cell membranes by virtue of their amphiphilic character. A detailed study of Os uptake and accumulation in MCF-7 cells supported this hypothesis. [Copyright &y& Elsevier]

The reaction of [Ru3(CO)10(mu-dppm)] (1) with dppmSe at 66 °C affords [Ru3(CO)8(mu-dppm)2] (2), [Ru3(CO)7(mu3-CO)(mu3-Se)(mu-dppm)] (3), [Ru3(CO)5(mu3-CO)(mu3-Se)(mu-dppm)2] (4) and [Ru3(CO)6(mu3-CO)(mu3-Se)(mu-dppm)(mu1-Ph2PCH2P(double bond; length as m-dashO)Ph2)] (5) in 7%, 5%, 9% and 33% yields, respectively. A similar reaction between 1 with dppmS gives [Ru3(CO)7(mu3-S)2(mu-dppm)] (6), [Ru3(CO)7(mu3-CO)(mu3-S)(mu-dppm)] (7) [Ru3(CO)5(mu3-CO)(mu3-S)(mu-dppm)2] (8) and [Ru3(CO)6(mu3-CO)(mu3-S)(mu-dppm)(mu1-Ph2PCH2P(double bond; length as m-dashO)Ph2)] (9) in 8%, 7%, 14% and 35% yields, respectively. Treatment of 1 with PhSeSePh at 66 °C affords the dinuclear compound [Ru2(CO)4(mu-SePh)2(mu-dppm)] (10) in 14% yield. Thermolysis of 5 and 9in refluxing toluene at 110 °C gives 4 and 8, respectively. The molecular structures of 4, 9 and 10 have been determined by single-crystal X-ray diffraction studies. The cores of the new clusters 4, 5, 8 and 9 consist of metal triangles capped by mu3-sulfur or selenium atoms with the bidentate ligand bridging in equatorial positions. In compounds 4 and 8, two bidentate dppm ligands bridge the Ru3 triangle in such a way that each ligand bridges two ruthenium atoms and one Ru-Ru edge remains unbridged. Compounds 5 and 9 contain one bridging dppm ligand and one dangling dppm mono-oxide ligand Ph2PCH2P(double bond; length as m-dashO)Ph2 coordinated to the rear metal atom at an equatorial position. The molecular structure of 10 shows classical "sawhorse" structure with two bridging SePh ligands as well as the dppm ligand. [ABSTRACT FROM AUTHOR]

The synthesis and solution chemistry of the water soluble clusters [Os3(CO)9(μ-η2-Bz)(μ-H)L+] (HBz=quinoxaline, L+=[P(OCH2CH2NMe3)3I3], 1) along with its negatively charged analog [Os3(CO)9(μ-η2-Bz)(μ-H)L-] (L-=[P(C6H4SO3)3Na3], 2) are reported. In addition, we have examined the reduction potentials of the complexes [Os3(CO)9(μ-η2-Bz)(μ-H)L] (HBz=phenanthridine, L=L+ (3); HBz=5,6 benzoquinoline, L=L+ (4); HBz=3-amino quinoline, L=L+ (5); HBz=3-amino quinoline, L=L- (6). The neutral analog of 1 and 2 [Os3(CO)9(μ-η2-Bz)(μ-H) PPh3] (Bz=quinoxaline, 7) was also examined for comparison. Both compounds 1 and 2 show pH dependent NMR spectra that are interpreted in terms of the extent of protonation of the uncoordinated quinoxaline nitrogen which impacts the degree of aggregation of the clusters in aqueous solution. Compound 1 undergoes a reversible 1e- reduction in water while 2 undergoes a quasi-reversible 1e- reduction at more negative potentials as expected from the difference in charge on the phosphine ligand. Compound 7 undergoes a marginally reversible CV in methylene chloride at a potential intermediate between the positively and negatively charged clusters. The overall stability of the radical anions of 1, 2 and 7 is somewhat less than the corresponding decacarbonyl [Os3(CO)10(μ-η2-Bz)(μ-H)] (HBz=quinoxaline). While complexes 1 and 2 show reversible 1e- reductions, all the other complexes examined show 1e- and/or two 1e- irreversible reductions in aqueous and non-aqueous solvents. The potentials for these complexes follow expected trends relating to the charge on the phosphine and the pH of the aqueous solutions. The ligand dependent trends are compared with those of the previously reported corresponding decacarbonyls. The interactions of the positively and negatively charged clusters with albumin have been investigated using the transverse and longitudinal relaxation times of the hydride resonances as probes of binding to the protein. Evidence of binding is observed for both the positive and negative clusters but the positive and negative clusters exhibit distinctly different rotational correlation times. Two additional complexes [Os3(CO)9(μ-η2-Bz)(μ-H)L] (HBz=2-methylbenzimidazole, L=L+ (8); L=L- (10) and HBz=quinoline-4-carboxaldehyde, L=L+ (9); L=L- (11)) are reported in connection with these studies. [Copyright &y& Elsevier]

The reactions of [Os3(CO)10(MeCN)2], [Ru3(CO)12], [(μ-H)Os3(CO)8{Ph2PCH2P(Ph)C6H4}], [Os3(CO)10(μ-dppm)] and [Ru3(CO)10(μ-dppm)] with 2-mercapto-1-methylimidazole are reported. The labile cluster [Os3(CO)10(MeCN)2] reacts with 2-mercapto-1-methylimidazole at 25 °C to give [(μ-H)Os3(CO)10{μ-SC&z.dbnd6;NCH&z.dbnd6;CHN(CH3)}] (1) whereas the corresponding reaction of [Ru3(CO)12] with the ligand at 68 °C gives [(μ-H)Ru3(CO)9{μ3-η2-SC&z.dbnd6;NCH&z.dbnd6;CHN(CH3)}] (2). Both [(μ-H)Os3(CO)8{Ph2PCH2P(Ph)C6H4}] and [Os3 (CO)10(μ-dppm)] react with 2-mercapto-1-methylimidazole at 25 and 110 °C, respectively, to give [(μ-H)Os3(CO)8{μ-SC&z.dbnd6;NCH&z.dbnd6;CHN(CH3)(μ-dppm)] (3). In contrast [Ru3(CO)10(μ-dppm)] reacts with 2-mercapto-1-methylimidazole at 68 °C to yield the known compound [Ru3(CO)7(μ3-CO)(μ3-S)(μ-dppm)] (4). The structures of 1–3 have been determined by X-ray crystallography. [Copyright &y& Elsevier]

[Display omitted] • Novel Rh-containing non-phosphorous supported catalysts for tandem hydroformylation-hydrogenation were obtained. • Tertiary nitrogen atoms of the polymer anchored on material's surface promote aldehyde hydrogenation over Rh active centers. • Catalysts showed high activity (hydroformylation TOF 206 h−1) and chemoselectivity. • Catalyst K N performed stable hydroformylation yield at least in the first 5 cycles with a decrease in alcohol selectivity. Non-phosphorous rhodium-containing catalysts for direct conversion of olefins to alcohols via tandem hydroformylation/hydrogenation have been designed and synthesized. Interaction between Rh(acac)(CO) 2 and tertiary amino groups on the surface of mesoporous hybrid organic-inorganic supports yielded materials which were successfully used in the tandem process. Data obtained for a selected catalyst K N demonstrate that rhodium is in the Rh+1 state highly dispersed on the surface and is bonded with nitrogen atoms both before and after use. Evaluation of the catalytic performance shows high activity (hydroformylation TOF 312 h−1), chemoselectivity and stable hydroformylation yield at least in the first 5 cycles with a decrease in alcohol selectivity. The influence of temperature, reaction time, total pressure, and molar CO/H 2 ratio of syngas on oxygenate yields is described. Type of the hydroformylation active sites and possible pathways for the observed decrease in hydrogenation are discussed. [ABSTRACT FROM AUTHOR]

The site preference for ligand substitution in the benzothiazolate-bridged cluster HOs 3 (CO) 10 (μ-1,2-N,C-η 1 ,κ 1 -C 7 H 4 NS) (1) has been investigated using PPh 3 . 1 reacts with PPh 3 in the presence of Me 3 NO to afford the mono- and bisphosphine substituted clusters HOs 3 (CO) 9 (PPh 3 )(μ-1,2-N,C-η 1 ,κ 1 -C 7 H 4 NS) (2) and HOs 3 (CO) 8 (PPh 3 ) 2 (μ-1,2-N,C-η 1 ,κ 1 -C 7 H 4 NS) (3), respectively. 2 exists as a pair of non-interconverting isomers where the PPh 3 ligand is situated at one of the equatorial sites syn to the edge-bridging hydride that shares a common Os-Os bond with the metalated heterocycle. The solid-state structure of the major isomer establishes the PPh 3 regiochemistry at the N-substituted osmium center. DFT calculations confirm the thermodynamic preference for this particular isomer relative to the minor isomer whose phosphine ligand is located at the adjacent C-metalated osmium center. 2 also reacts with PPh 3 to give 3. The locus of the second substitution occurs at one of the two equatorial sites at the Os(CO) 4 moiety in 2 and gives rise to a pair of fluxional stereoisomers where the new phosphine ligand is scrambled between the two equatorial sites at the Os(CO) 3 P moiety. The molecular structure of the major isomer has been determined by X-ray diffraction analysis and found to represent the lowest energy structure of the different stereoisomers computed for HOs 3 (CO) 8 (PPh 3 ) 2 (μ-1,2-N,C-η 1 ,κ 1 -C 7 H 4 NS). The fluxional behavior displayed by 3 has been examined by VT NMR spectroscopy, and DFT calculations provide evidence for stereoselective tripodal rotation at the Os(CO) 3 P moiety that serves to equilibrate the second phosphine between the two available equatorial sites., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Anchoring Rh complexes to the surface of a silica polyamine composite, which has a poly(allylamine) covalently grafted to the surface of amorphous silica gel, yielded a material that proved to be an effective and novel heterogeneous catalyst for hydroformylation of unsaturated compounds. Surface amino groups of the material were modified with phosphines by covalent and ionic coupling. The modified materials were then treated with Rh(acac)(CO) 2 , giving the catalysts K-1 and K-2. Catalysts were characterized by solid-state NMR spectroscopy, IR spectroscopy, XPS, TEM, and elemental analysis. The activity and stability of K-1 and K-2 were then studied for the hydroformylation of selected unsaturated compounds. Hydroformylation of terminal double bonds occurred selectively in the presence of internal double bonds. Characterization of the catalysts and the problems encountered with the supported catalysts are discussed. Catalyst K-1 is reusable and can be applied to the hydroformylation of linear olefins, styrene, 4-vinylcyclohexene, and dienes, as well as representative terpenes and other unsaturated hydrocarbons in a batch reactor.

Luminescent ruthenium diimine complexes have been covalently bound to the surface of a silica polyamine composite (SPC) using peptide coupling agents. The loading of the complexes using this route is quite low (~0.01-0.04 mmol/g) leaving sufficient surface amines to coordinate added metal ions. When the composite particles containing the Ru complexes are exposed to solutions of Cu 2+ , Ni 2+ or Zn 2+ , luminescence is quenched with efficiencies that follow concentration dependence and the relative binding affinities of the ions. When heavy metal ions such as mercury or lead are adsorbed onto the same surface, luminescence is enhanced by a factor of ~3.5. When the complexes are exposed to these metals in solution, no quenching or enhancement is observed. Both phenomena were shown to be the result of adsorption of the cations onto the polyamine surface by using the Stern-Volmer relationship. The mechanism of both quenching and enhancement is discussed and the options for further development of this novel metal sensing technique are presented.

New heterogeneous hydrogenation catalysts, based on Pd nanoparticles and polypropyleneimine (PPI) dendrimers of the third generation that have been covalently grafted to a silica surface modified with polyallylamine (PAA) have been synthesized. The final products were characterized by TEM, XPS, and solid-state NMR spectroscopy. The synthesized materials are effective catalysts for selective hydrogenation of dienes to monoenes and phenyl acetylene to styrene at very high substrate/Pd ratios with turnover rates higher than related Pd nanoparticle catalysts. The synthesized catalysts can be reused without any loss of activity in the case of styrene and isoprene.

Ruthenium complexes of the general formula [Ru(CO)(H)(L 2 )(L' 2 )][PF 6 ] (L 2 = trans- 2PPh 3 , L' = η 2 -4,4'-dicarboxybipyridine ( 1 ); L 2 = trans -2Ph 2 PCH 2 CH 2 COOH, L' 2 = bipyridine ( 2 ); L 2 = Ph 2 PCHCHPPh 2 , L' = η 2 -5-amino-1,10-phenanthroline ( 3 ); L 2 = trans- 2PPh 3 , L' 2 = η 2 -4-carboxaldehyde-4'-methylbipyridine ( 4 )) have been shown to have longer emission lifetimes and higher quantum yields in solution compared with more symmetrical molecules such as [Ru(bpy) 3 ][Cl] 2 . Compound 4 is obtained as a mixture with the corresponding acetal, 4' . These less symmetrical complexes have been covalently immobilized on the surface of silica polyamine composites, and their photophysical properties have been studied. The surface-bound complexes have been characterized by solid-state CPMAS 13 C, 31 P, and 29 Si NMR, UV-vis, and FT-IR spectroscopies. Excited-state lifetime studies revealed that, in general, the lifetimes of the immobilized complexes are 1.4 to 8 times longer than in solution and are dependent on particle size (300-500 μm versus 10-20 nm average diameter silica gels), polymer structure (linear poly(allylamine) versus branched poly(ethylenimine)), and the type of surface tether. One exception to this trend is the previously reported complex [Ru(bpy) 2 (5-amino-1,10-phenanthroline)][PF 6 ] 2 ( 5 ), where only a slight increase in lifetime is observed. Only minor changes in emission wavelength are observed for all the complexes. This opens up the possibility for enhanced heterogeneous electron transfer in photocatalytic reactions.

A sol-gel method has been developed for the synthesis of composite materials analogous to the previously reported and commercialized silica polyamine composite (SPC) materials made from amorphous silica. Monolithic xerogels were formed using a two-step procedure with no templating agent using acid catalyzed followed by base catalyzed hydrolysis. This reaction was followed by (1)H NMR. Initial sol-gels were formed using a methyltrimethoxysilane (MTMOS) and 3-chloropropyltrimethoxysilane (CPTMOS) mixture. Elemental analyses and (13)C CPMAS NMR confirmed incorporation of both monomeric units into the surface structure. Some control over surface morphology was achieved by adjusting synthetic conditions. The resulting xerogels were reacted with poly(allylamine) (PAA) to give composite materials which showed much lower metal ion capacities than the commercially available amorphous silica analogs. The low degree of reaction of the chloropropyl groups indicated they were not surface-available to the polyamine. Addition of tetramethoxysilane (TMOS) produced a structural matrix and resulted in higher chloride utilization (reaction of surface chloropropyl groups with the polyamine). The ratio of the three siloxane monomeric components was varied until the resulting polyamine composite xerogels had metal capacities comparable with the commercialized SPC materials. These composites had narrower average pore size distributions and fewer small pores. Further modification of these composites with metal selective ligands showed material characteristics similar to those of commercially available SPC materials. Subjecting a composite made by the sol-gel route to one thousand load-strip cycles with Cu(2+) shows essentially no loss in metal capacity, and this robustness compares favorably with that observed for the SPC made from amorphous silica gels., (© 2012 American Chemical Society)

This perspective report summarizes recent work on the interactions of the triosmium clusters of general formula Os(3)(CO)(9)(μ(3)-η(2)-L-H)(μ-H) (L = bicyclic benzoheterocycle) with DNA and proteins. The early work focused on how the structure of the benzoheterocycle influenced the binding of the cluster to plasmid DNA, albumin and the inhibition of telomerase. Later, selective binding of the triosmium clusters to guanine was targeted using a range of alkylating functionalities. In connection with these efforts some very recent unpublished work will be presented. Suggestions for future directions in this area and a summary of the problems and difficulties encountered will be discussed.

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.

Treatment of Mn(2)(CO)(10) with 3,4-toluenedithiol and 1,2-ethanedithiol in the presence of Me(3)NO.2H(2)O in CH(2)Cl(2) at room temperature afforded the dinuclear complexes Mn(2)(CO)(6)(mu-eta(4)-SC(6)H(3)(CH(3))S-SC(6)H(3)(CH(3))S) (1), and Mn(2)(CO)(6)(mu-eta(4)-SCH(2)CH(2)S-SCH(2)CH(2)S) (2), respectively. Similar reactions of Re(2)(CO)(10) with 3,4-toluenedithiol, 1,2-benzenedithiol, and 1,2-ethanedithiol yielded the dirhenium complexes Re(2)(CO)(6)(mu-eta(4)-SC(6)H(3)(CH(3))S-SC(6)H(3)(CH(3))S) (3), Re(2)(CO)(6)(mu-eta(4)-SC(6)H(4)S-SC(6)H(4)S) (4), and Re(2)(CO)(6)(SCH(2)CH(2)S-SCH(2)CH(2)S) (5), respectively. In contrast, treatment of Mn(2)(CO)(10) with 1,3-propanedithiol afforded the trimanganese compound Mn(3)(CO)(6)(mu-eta(2)-SCH(2)CH(2)CH(2)S)(3) (6), whereas Re(2)(CO)(10) gave only intractable materials. The molecular structures of 1, 3, and 6 have been determined by single-crystal X-ray diffraction studies. The dimanganese and dirhenium carbonyl compounds 1-5contain a binucleating disulfide ligand, formed by interligand disulfide bond formation between two dithiolate ligands identical in structure to that of the previously reported dimanganese complex Mn(2)(CO)(6)(mu-eta(4)-SC(6)H(4)S-SC(6)H(4)S). Complex 6, on the other hand, forms a unique example of a mixed-valence trimangenese carbonyl compound containing three bridging 1,3-propanedithiolate ligands. The solution properties of 6 have been investigated by UV-vis and EPR spectroscopies as well as electrochemical techniques.

The variable temperature (1)H and (13)C NMR and EPR spectra of the stable radical anions [Os(3)(CO)(9)(micro(3)-eta(2)-L)(micro-H)] (LH=phenanthridine, 1; 5,6-benzoquinoline, 2), and [Os(3)(CO)(10)(micro(3)-eta(2)-L)(micro-H)] (LH=quinoxaline, 3) are reported. The radical anions 1(-), 2(-), and 3(-) can be prepared by both exhaustive electrolysis and partially by chemical reduction with cobaltocene and with sodium dispersion (only with sodium dispersion in the case of 3(-)). DFT calculations on 1-3 reveal that the LUMO for the electron-deficient compounds 1 and 2 involves significant contributions from both the heterocyclic ligand and the two metal atoms bridged by the ligand and the micro-hydride. The character of this orbital rationalizes the previously observed regioselective reactions of these complexes with nucleophiles. In contrast, the LUMO for the electron precise 3 involves only ligand-based orbitals. Partial chemical reduction of 1 and 2 requires an excess of either cobaltocene or sodium, and their (1)H and (13)C NMR spectra reveal selective line broadening of those proton resonances that are predicted by DFT calculations to bear the greatest amount of free spin density. The variable temperature behavior of the partially chemically reduced species of 1 and 2 indicates that electron transfer between the reduced/unreduced cluster pair and between the cobaltocene/cobaltocenium pair occurs on the NMR timescale. The radical anions of 1 and 2 prepared by exhaustive electrolysis show an EPR signal at room temperature, while the NMR signals are uniformly broadened. Compound 3 appears to be partially reduced by sodium at room temperature and shows uniformly broadened (1)H NMR resonances at room temperature that sharpen significantly at -80 degrees C. The temperature dependence of the spectra are discussed in terms of the effects of relative electron nuclear relaxation processes, chemical exchange, and the results of the DFT calculations.