Osmium Catalysts for Acceptorless and Base-Free Dehydrogenation of Alcohols and Amines: Unusual Coordination Modes of a BPI Anion

A novel type of catalyst precursors for the dehydrogenation of hydrogen carriers based on organic liquids has been discovered. Complexes OsH6(PiPr3)2 (1) and OsH(OH)(CO)(PiPr3)2 (2) react with 1,3-bis(6'-methyl-2'-pyridylimino)isoindoline (HBMePI) to give OsH3{¿2-Npy,Nimine-(BMePI)}(PiPr3)2 (3) and OsH{¿2-Npy,Nimine-(BMePI)}(CO)(PiPr3)2 (4). The unprecedented ¿2-Npy,Nimine coordination mode of BMePI is thermodynamically preferred with Os(IV) and Os(II) metal fragments and allows for preparation of BMePI-based dinuclear metal cations. Treatment of OsH2Cl2(PiPr3)2 (5) with 0.5 equiv of HBMePI in the presence of KOtBu affords the chloride salt of the bis(osmium(IV)) dinuclear cation [{OsH3(PiPr3)2}2{µ-(¿2-Npy,Nimine)2-BMePI}]+ (6). Related homoleptic bis(osmium(II)) complexes have been also synthesized. Complex 4 reacts with the bis(solvento) [OsH(CO){¿1-O-[OCMe2]2}(PiPr3)2]BF4 to give [{OsH(CO)(PiPr3)2}2{µ-(¿2-Npy,Nimine)2-BMePI}]BF4 (7), whereas the addition of 0.5 equiv of HBMePI to {OsCl(¿6-C6H6)}2(µ–Cl)2 (8) affords [{OsCl(¿6-C6H6)}2{µ-(¿2-Npy,Nimine)2-BMePI}]Cl (9). The reactions of 4 with 8 and {OsCl(¿6-p-cymene)}2(µ–Cl)2 (10) lead to the heteroleptic cations [(PiPr3)2(CO)HOs{µ-(¿2-Npy,Nimine)2-BMePI}OsCl(¿6-arene)]+ (arene = C6H6 (11), p-cymene (12)). The electronic structrure and electrochemical properties of the dinuclear complexes were also studied. Complexes 3 and 4 are efficient catalyst precursors for the acceptorless and base-free dehydrogenation of secondary and primary alcohols and cyclic and lineal amines. The primary alcohols afford aldehydes. The amount of H2 released per gram of heterocycle depends upon the presence of a methyl group adjacent to the nitrogen atom, the position of the nitrogen atom in the heterocycle, and the size of the heterocycle

The Efficiency of Gravitational Bremsstrahlung Production in the Collision of Two Schwarzschild Black Holes

We examine the efficiency of gravitational bremsstrahlung production in the process of head-on collision of two boosted Schwarzschild black holes. We constructed initial data for the characteristic initial value problem in Robinson-Trautman spacetimes, that represent two instantaneously stationary Schwarzschild black holes in motion towards each other with the same velocity. The Robinson-Trautman equation was integrated for these initial data using a numerical code based on the Galerkin method. The final resulting configuration is a boosted black hole with Bondi mass greater than the sum of the individual mass of each initial black hole. Two relevant aspects of the process are presented. The first relates the efficiency $\Delta$ of the energy extraction by gravitational wave emission to the mass of the final black hole. This relation is fitted by a distribution function of non-extensive thermostatistics with entropic parameter $q \simeq 1/2$; the result extends and validates analysis based on the linearized theory of gravitational wave emission. The second is a typical bremsstrahlung angular pattern in the early period of emission at the wave zone, a consequence of the deceleration of the black holes as they coalesce; this pattern evolves to a quadrupole form for later times.Comment: 16 pages, 4 figures, to appear in Int. J. Modern Phys. D (2008

A tumor-stroma targeted oncolytic adenovirus replicated in human ovary cancer samples and inhibited growth of disseminated solid tumors in mice

Targeting the tumor stroma in addition to the malignant cell compartment is of paramount importance to achieve complete tumor regression. In this work, we modified a previously designed tumor stroma-targeted conditionally replicative adenovirus (CRAd) based on the SPARC promoter by introducing a mutated E1A unable to bind pRB and pseudotyped with a chimeric Ad5/3 fiber (Ad F512v1), and assessed its replication/lytic capacity in ovary cancer in vitro and in vivo. AdF512v1 was able to replicate in fresh samples obtained from patients: (i) with primary human ovary cancer; (ii) that underwent neoadjuvant treatment; (iii) with metastatic disease. In addition, we show that four intraperitoneal (i.p.) injections of 5 × 10(10) v.p. eliminated 50% of xenografted human ovary tumors disseminated in nude mice. Moreover, AdF512v1 replication in tumor models was enhanced 15-40-fold when the tumor contained a mix of malignant and SPARC-expressing stromal cells (fibroblasts and endothelial cells). Contrary to the wild-type virus, AdF512v1 was unable to replicate in normal human ovary samples while the wild-type virus can replicate. This study provides evidence on the lytic capacity of this CRAd and highlights the importance of targeting the stromal tissue in addition to the malignant cell compartment to achieve tumor regression.Fil: Lopez, Maria Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; ArgentinaFil: Rivera, Angel A.. University Of Alabama At Birmingahm; Estados UnidosFil: Viale, Diego Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; ArgentinaFil: Benedetti, Lorena Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; ArgentinaFil: Cuneo, Nicasio. Hospital Municipal de Oncología Marie Curie; ArgentinaFil: Kimball, Kristopher J.. University Of Alabama At Birmingahm; Estados UnidosFil: Wang, Minghui. University Of Alabama At Birmingahm. School Of Medicine. Division Of Human Gene Therapy; Estados UnidosFil: Douglas, Joanne T.. University Of Alabama At Birmingahm. School Of Medicine. Division Of Human Gene Therapy; Estados UnidosFil: Zhu, Zeng B.. University Of Alabama At Birmingahm. School Of Medicine. Division Of Human Gene Therapy; Estados UnidosFil: Bravo, Alicia I.. Provincia de Buenos Aires. Ministerio de Salud. Hospital Interzonal de Agudos "eva Peron"; ArgentinaFil: Gidekel, Manuel. Universidad de la Frontera; ChileFil: Alvarez, Ronald D.. University Of Alabama At Birmingahm; Estados UnidosFil: Curiel, David T.. University Of Alabama At Birmingahm. School Of Medicine. Division Of Human Gene Therapy; Estados Unidos. University of Washington; Estados UnidosFil: Podhajcer, Osvaldo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; Argentin

Differential effect of obesity on bone mineral density in White, Hispanic and African American women: a cross sectional study

Osteoporosis is a major public health problem with low bone mass affecting nearly half the women aged 50 years or older. Evidence from various studies has shown that higher body mass index (BMI) is a protective factor for bone mineral density (BMD). Most of the evidence, however, is from studies with Caucasian women and it is unclear to what extent ethnicity plays a role in modifying the effect of BMI on BMD. A cross sectional study was performed in which records of postmenopausal women who presented for screening for osteoporosis at 2 urban medical centres were reviewed. Using logistic regression, we examined the interaction of race and BMI after adjusting for age, family history of osteoporosis, maternal fracture, smoking, and sedentary lifestyle on BMD. Low BMD was defined as T-score at the lumbar spine < -1. Among 3,206 patients identified, the mean age of the study population was 58.3 ± 0.24 (Years ± SEM) and the BMI was 30.6 kg/m(2). 2,417 (75.4%) were African Americans (AA), 441(13.6%) were Whites and 348 (10.9%) were Hispanics. The AA women had lower odds of having low BMD compared to Whites [Odds ratio (OR) = 0.079 (0.03–0.24) (95% CI), p < 0.01]. The odds ratio of low BMD was not statistically significant between White and Hispanic women. We examined the interaction between race and BMD. For White women; as the BMI increases by unity, the odds of low BMD decreases [OR = 0.9 (0.87–0.94), p < 0.01; for every unit increase in BMI]. AA women had slightly but significantly higher odds of low BMD compared to Whites [OR 1.015 (1.007–1.14), p <0.01 for every unit increase in BMI]. This effect was not observed when Hispanic women were compared to Whites. There is thus a race-dependent effect of BMI on BMD. With each unit increase in BMI, BMD increases for White women, while a slight but significant decrease in BMD occurs in African American women

Exploring new physics frontiers through numerical relativity

The demand to obtain answers to highly complex problems within strong-field gravity has been met with significant progress in the numerical solution of Einstein's equations - along with some spectacular results - in various setups. We review techniques for solving Einstein's equations in generic spacetimes, focusing on fully nonlinear evolutions but also on how to benchmark those results with perturbative approaches. The results address problems in high-energy physics, holography, mathematical physics, fundamental physics, astrophysics and cosmology

Novel coordination modes of a BPI anion in osmium complexes

Resumen del trabajo presentado a la X International School on Organometallic Chemistry “Marcial Moreno Mañas”, celebrada en Ciudad Real (España) del 5 al 7 de julio de 2017.1,3-Bis(2-pyridylimino)isoindolates (BPIs) are a class of polydentate nitrogen-donor monoanionic ligands which usually form Npy,Niso,Npy-pincer complexes with transition metals, although a few compounds present other coordination modes. BPI complexes are of interest in homogeneous catalysis in different organic reactions including upgrading ethanol to 1-butanol, hydroboration of ketones and nitriles, hydrogenation of alkynes, among others. Recently in our group, the Npy,Nimine-bidentate-chelate and Npy,Nimine,Nimine,Npy-tetradentatebridge coordination modes of the 1,3-bis(6’-methyl-2’-pyridylimino)isoindolinate anion have been discovered. In the present contribution, we will show the preparation of novel BPI osmium complexes and some preliminary studies in catalytic reactions.Peer reviewe

N–H and C–H Bond Activations of an Isoindoline Promoted by Iridium- and Osmium-Polyhydride Complexes: A Noninnocent Bridge Ligand for Acceptorless and Base-Free Dehydrogenation of Secondary Alcohols

The elusive C–H bond activation of an organic fragment contained in many biologically active molecules and the use of the resulting noninnocent ligand in bimetallic catalysis applied to the acceptorless and base-free dehydrogenation of secondary alcohols has been performed by using the polyhydrides IrH5(PiPr3)2 (1) and OsH6(PiPr3)2 (2). Complex 1 activates the N–H bond of 1,3-bis(6′-methylpyridyl-2′-imino)isoindoline (HBMePHI) to give the mononuclear complex IrH2{κ2-Npy,Nimine(BMePHI)}(PiPr3)2 (3). Both 1 and 2 activate the C(sp2)–H bond at position 4 of the core isoindoline of the BMePHI ligand of 3. The reactions lead to the homobinuclear complex (PiPr3)2H2Ir{μ-(κ2-Npy,Nimine-BMePI-κ2-Nimine,C4iso)}IrH2(PiPr3)2 (4) and the heterobinuclear compound (PiPr3)2H2Ir{μ-(κ2-Npy,Nimine-BMePI-κ2-Nimine,C4iso)}OsH3(PiPr3)2 (5), respectively. The metalated carbon atom of 4 and 5 has a marked nucleophilic character. Thus, it adds the proton of alcohols to afford the respective cations [(PiPr3)2H2Ir{μ-(κ2-Npy,Nimine-BMePHI-κ2-Npy,Nimine)}IrH2(PiPr3)2]+ (6) and [(PiPr3)2H2Ir{μ-(κ2-Npy,Nimine-BMePHI-κ2-Npy,Nimine)}OsH3(PiPr3)2]+ (7), and the corresponding alkoxide. The mononuclear complex 3 and the binuclear compounds 4 and 5 are efficient catalysts for the acceptorless and base-free dehydrogenation of secondary alcohols. The binuclear complexes 4 and 5 are significantly more active than 3. The catalytic synergism is a consequence of the mutual electronic influence of the metals through the bridge. X-ray diffraction analysis data of the structures of 3–5 and the reactivity of 4 and 5 support a noninnocent character of the bridging ligand.Financial support from the MINECO of Spain (Projects CTQ2017-82935-P (AEI/FEDER, UE) and RED2018-102387-T), Gobierno de Aragón (Group E06_20R and project LMP148_18), FEDER, and the European Social Fund is acknowledged. A.I.N. thanks the MINECO for his predoctoral fellowship.Peer reviewe

Alternative conceptual approach to the design of bifunctional catalysts: An osmium germylene system for the dehydrogenation of formic acid

The reaction of the hexahydride OsH6(PiPr3)2 with a P,Ge,P-germylene-diphosphine affords an osmium tetrahydride derivative bearing a Ge,P-chelate, which arises from the hydrogenolysis of a P–C(sp3) bond. This Os(IV)–Ge(II) compound is a pioneering example of a bifunctional catalyst based on the coordination of a σ-donor acid, which is active in the dehydrogenation of formic acid to H2 and CO2. The kinetics of the dehydrogenation, the characterization of the resting state of the catalysis, and DFT calculations point out that the hydrogen formation (the fast stage) exclusively occurs on the coordination sphere of the basic metal center, whereas both the metal center and the σ-donor Lewis acid cooperatively participate in the CO2 release (the rate-determining step). During the process, the formate group pivots around the germanium to approach its hydrogen atom to the osmium center, which allows its transfer to the metal and the CO2 release.Financial support was provided by the MICINN of Spain (PID2020-115286GB-I00/AEI/10.13039/501100011033, RED2018-102387-T, and PID2019-104652GB-I00), Gobierno de Aragón (E06_20R and LMP148_18), FEDER, and FSE.Peer reviewe

Preparation and degradation of rhodium and iridium diolefin catalysts for the acceptorless and base-free dehydrogenation of secondary alcohols

Rhodium and iridium diolefin catalysts for the acceptorless and base-free dehydrogenation of secondary alcohols have been prepared, and their degradation has been investigated, during the study of the reactivity of the dimers [M(μ-Cl)(η4-C8H12)]2 (M = Rh (1), Ir (2)) and [M(μ-OH)(η4-C8H12)]2 (M = Rh (3), Ir (4)) with 1,3-bis(6′-methyl-2′-pyridylimino)isoindoline (HBMePHI). Complex 1 reacts with HBMePHI, in dichloromethane, to afford equilibrium mixtures of 1, the mononuclear derivative RhCl(η4-C8H12){κ1-Npy-(HBMePHI)} (5), and the binuclear species [RhCl(η4-C8H12)]2{μ-Npy,Npy-(HBMePHI)} (6). Under the same conditions, complex 2 affords the iridium counterparts IrCl(η4-C8H12){κ1-Npy-(HBMePHI)} (7) and [IrCl(η4-C8H12)]2{μ-Npy,Npy-(HBMePHI)} (8). In contrast to chloride, one of the hydroxide groups of 3 and 4 promotes the deprotonation of HBMePHI to give [M(η4-C8H12)]2(μ-OH){μ-Npy,Niso-(BMePHI)} (M = Rh (9), Ir (10)), which are efficient precatalysts for the acceptorless and base-free dehydrogenation of secondary alcohols. In the presence of KOtBu, the [BMePHI]− ligand undergoes three different degradations: alcoholysis of an exocyclic isoindoline-N double bond, alcoholysis of a pyridyl-N bond, and opening of the five-membered ring of the isoindoline core.Financial support from the MCI, projects CTQ2017-82935-P, PID2019-108429RB-I00, and RED2018-102387-T, the Gobierno de Aragón (Group E06_17R), Fundación Ramón Areces (XVIII Concurso Nacional de Ayudas a la Investigación en Ciencias de la Vida y de la Materia CIVP18A3938), Fondo Europeo de Desarrollo Regional (FEDER), and the European Social Fund (FSE) is acknowledged. A.I.N. and A.C. thank the MINECO (Spain) for a predoctoral fellowship and Juan de la Cierva-Incorporación Fellowship, respectively.Peer reviewe