Hydrogenase biomimetics with redox-active ligands: Electrocatalytic proton reduction by [Fe2(CO)4(κ2-diamine)(μ-edt)] (diamine = 2,2′-bipy, 1,10-phen)

Diiron complexes bearing redox active diamine ligands have been studied as models of the active site of [FeFe]-hydrogenases. Heating [Fe2(CO)6(μ-edt)] (edt = 1,2-ethanedithiolate) with 2,2′-bipyridine (2,2′-bipy) or 1,10-phenanthroline (1,10-phen) in MeCN in the presence of Me3NO leads to the formation of [Fe2(CO)4(κ2-2,2′-bipy)(μ-edt)] (1-edt) and [Fe2(CO)4(κ2-1,10-phen)(μ-edt)] (2-edt), respectively, in moderate yields. In the solid state the diamine resides in dibasal sites, while both dibasal and apical–basal isomers are present in solution. Both stereoisomers protonate readily upon addition of strong acids. Cyclic voltammetry in MeCN shows that both complexes undergo irreversible oxidation and reduction, proposed to be a one- and two-electron process, respectively. The structures of neutral 2-edt and its corresponding one- and two-electron reduced species have been investigated by DFT calculations. In 2-edt− the added electron occupies a predominantly ligand-based orbital, and the iron–iron bond is maintained, being only slightly elongated. Addition of the second electron affords an open-shell triplet dianion where the second electron populates an Fe–Fe σ* antibonding orbital, resulting in effective scission of the iron–iron bond. The triplet state lies 4.2 kcal mol−1 lower in energy than the closed-shell singlet dianion whose HOMO correlates nicely with the LUMO of the neutral species 2-edt. Electrocatalytic proton reduction by both complexes has been studied in MeCN using CF3CO2H as the proton source. These catalysis studies reveal that while at high acid concentrations the active catalytic species is [Fe2(CO)4(μ-H)(κ2-diamine)(μ-edt)]+, at low acid concentrations the two complexes follow different catalytic mechanisms being associated with differences in their relative rates of protonation

Mixed main group transition metal clusters: Reactions of [Ru 3 (CO) 10 (μ-dppm)] with Ph 3 SnH

Novel dppm-ligated ruthenium-tin clusters have been prepared from the reaction of [Ru3(CO)10(μ-dppm)] with Ph3SnH. At room temperature and in the presence of Me3NO, [Ru3(CO)9(SnPh3) (μ-dppm) (μ-H)] (1) is produced from the formal loss of CO and Sn-H bond oxidative-addition. Treatment of 1 with a further two equivalents of Ph3SnH (in the presence of Me3NO) gave [Ru3(CO)7(SnPh3)2(μ-SnPh2)(μ-dppm)(μ-H)(μ3-H)] (2) which results from both Sn–H and Sn–C bond scission and contains two different hydride environments (μ and μ3) and a μ-SnPh2 moiety. Cluster 2 has 48 CVE (cluster valence electron) with three formal ruthenium-ruthenium bonds; two of those are very long and fall at the extreme end of distances attributed to ruthenium-ruthenium bonds. Thermolysis of 2 at 66 °C liberates benzene to give [Ru3(CO)8(SnPh3)(μ-SnPh2)(μ3-SnPh2)(μ-dppm)(μ-H)] (3). DFT calculations confirm that the hydride bridges one of the Ru-μ-SnPh2 bonds in 3. The solid-state structures of 2 and 3 have been determined by X-ray crystallography, and the bonding and ligand distribution have been investigated by DFT studies. The geometry-optimized structures are consistent with the solid-state structures

Alkyne activation and polyhedral reorganization in benzothiazolate-capped osmium clusters on reaction with diethyl acetylenedicarboxylate (DEAD) and ethyl propiolate

The reactivity of the face-capped benzothiazolate clusters HOs3(CO)9[μ3-C7H3(R)NS] (1a, R = H; 1b, R = 2-CH3) with alkynes has been investigated. 1a reacts with DEAD at 67 °C to furnish the isomeric alkenyl clusters Os3(CO)9(μ-C7H4NS)(μ3-EtO2CCCHCO2Et) (2a and 3a). X-ray crystallographic analyses of 2a and 3a have confirmed the stereoisomeric relationship of these products and the regiospecific polyhedral expansion that follows the formal transfer of the hydride to the coordinated alkyne ligand in HOs3(CO)9(μ-C7H4NS)(2-DEAD). The significant structural differences between the two isomers, as revealed by the solid-state structures, derives from the regiospecific cleavage of one of the three Os-Os bonds in the intermediate alkenyl cluster Os3(CO)9(μ-C7H4NS)(1-EtO2CCCHCO2Et), which follows hydride transfer to the coordinated alkyne ligand in the pi compound HOs3(CO)9(μ-C7H4NS)(2-DEAD). Control experiments confirm the reversibility of the reaction leading to the formation of 2a and 3a. Whereas heating either isomer in refluxing THF or benzene affords a binary mixture containing 2a and 3a, thermolysis in refluxing toluene leads to the activation of the alkenyl ligand and formation of the new cluster Os3(CO)9(μ-C7H4NS)(μ3-EtO2CCCH2) (4). 4 was independently synthesized from 1a and ethyl propiolate at room temperature. The computed mechanisms that account for the formation of 2a and 3a are presented, along with the mechanism for the reaction of 1a with ethyl propiolate to give 4

Reactions of Ru3(CO)10(μ-dppm) with Ph3GeH: Ge–H and Ge–C bond cleavage in Ph3GeH at triruthenium clusters

The activation of Ph3GeH at the dppm-bridged cluster Ru3(CO)10(μ-dppm) [dppm = bis(diphenylphosphino)methane] has been investigated. Ru3(CO)10(μ-dppm) reacts with Ph3GeH at room temperature in the presence of Me3NO to give the new cluster products Ru3(CO)9(GePh3)(μ-dppm)(μ-H) (1) and Ru3(CO)8(GePh3)2(μ-dppm)(μ-H)2 (2) via successive oxidation-addition of two Ge–H bonds. Refluxing 1 in THF furnishes the diruthenium complex Ru2(CO)6(μ-GePh2)(μ-dppm) (3) as the major product (44%), in addition to Ru3(CO)7(μ-CO)(GePh3){μ3-PhPCH2P(Ph)C6H4}(μ-H) (4) and the known cluster Ru3(CO)9(μ-H)(μ3-Ph2PCH2PPh) (5) in 7 and 8% yields, respectively. Heating samples of cluster 2 also afforded 3 as the major product together with a small amount of Ru3(CO)7(GePh3)(μ-OH)(μ-dppm)(μ-H)2 (6). DFT calculations establish the stability of the different possible isomers for clusters 1, 2, and 6, in addition to providing insight into the mechanism for hydride fluxionality in 2. All new compounds have been characterized by analytical and spectroscopic methods, and the molecular structures of 1, 3, and 6 have been established by single-crystal X-ray diffraction analyses

Reversible C-H bond activation at a triosmium centre: A comparative study of the reactivity of unsaturated triosmium clusters Os3(CO)8(μ-dppm)(μ-H)2 and Os3(CO)8(μ-dppf)(μ-H)2 with activated alkynes

Heating a benzene solution of the unsaturated cluster Os3(CO)8(μ-dppm)(μ-H)2 (1) [dppm = bis(diphenylphosphino)methane] with MeO2CCtriple bond; length of mdashCCO2Me (DMAD) or EtO2CCtriple bond; length of mdashCCO2Et (DEAD) at 80 °C furnished the dinuclear compounds Os2(CO)4(μ-dppm)(μ-η2;η1;к1-RO2CCCHCO2R)(μ-H) (3a, R = Me, 3b, R = Et) and the saturated trinuclear complexes Os3(CO)7(μ-dppm)(μ3-η2;η1;η1-RO2CCCCO2R)(μ-H)2 (4a, R = Me, 4b, R = Et). In contrast, similar reactions using unsaturated Os3(CO)8(μ-dppf)(μ-H)2 (2) [dppf = bis(diphenylphosphino)ferrocene] afforded only the trinuclear complexes Os3(CO)8(μ-dppf)(μ-η2;η1-RO2CCHCCO2R)(μ-H) (5a, R = Me; 5b, R = Et) and Os3(CO)7(μ-dppf)(μ3-η2;η1;η1-RO2CCCCO2R)(μ-H)2 (6a, R = Me; 6b, R = Et). Control experiments confirm that 5a and 5b decarbonylate at 80 °C to give 6a and 6b, respectively. Both 5a and 5b exist as a pair of isomers in solution, as demonstrated by 1H NMR and 31P{1H} NMR spectroscopy. DFT calculations on cluster 5a (as the dppf-Me4 derivative) indicate that the isomeric mixture derives from a torsional motion that promotes the conformational flipping of the cyclopentadienyl groups of the dppf-Me4 ligand relative to the metallic plane. VT NMR measurements on clusters 6a and 6b indicate that while the hydride ligand associated with the dppf-bridged Os-Os bond is nonfluxional at room temperature, the second hydride rapidly oscillates between the two non-dppf-bridged Os-Os edges. DFT examination of this hydride fluxionality confirms a “windshield wiper” motion for the labile hydride that gives rise to a time-average coupling of this hydride to both phosphorus centers of the dppf ligand. Thermolysis of 6a and 6b in refluxing toluene yielded Os3(CO)7(μ-dppf)(μ-η2;η1;к1-CCHCO2R) (7a, R=Me; 7b, R=Et). The vinylidene moieties in 7a and 7b derive from the carbon-carbon bond cleavage of coordinated alkyne ligands, and these two products exhibit high thermal stability in refluxing toluene

Iron carbonyl complexes bearing phenazine and acridine ligands: X-ray structures of Fe(CO)(3)(eta(4)-C12H8N2), Fe(CO)(2){P(OMe)(3)}(eta(4)-C12H8N2), Fe(CO)(2)(PPh3) (eta(4)-C13H9N), and Fe(CO)(2)(kappa(1)-dppm) (eta(4)-C12H8N2)

Reactions of Fe3(CO)12 with the heterocycles phenazine and acridine in refluxing benzene afforded the mononuclear complexes Fe(CO)3(η4-C12H8N2) (1a) and Fe(CO)3(η4-C13H9N) (1b), respectively. Treatment of 1a with P(OMe)3 and PPh3 in the presence of Me3NO at room temperature yielded the carbonyl substitution products Fe(CO)2{P(OMe)3}(η4-C12H8N2) (2a) and Fe(CO)2(PPh3) (η4-C12H8N2) (3a), respectively. Similar reactions of 1b yielded Fe(CO)2{P(OMe)3}(η4-C13H9N) (2b) and Fe(CO)2(PPh3) (η4-C13H9N) (3b). Treatment of 1a with the diphosphines dppm and dppf under similar conditions afforded the mononuclear compounds Fe(CO)2(κ1-dppm) (η4-C12H8N2) (4a) and Fe(CO)2(κ1-dppf) (η4-C12H8N2) (4b). Compounds 1a, 2a, 3b, and 4a have been structurally characterized by X-ray crystallography. The ancillary phenazine and acridine ligands in these products adopt an η4-coordination mode by using only the peripheral carbon atoms in one of the carbocyclic rings. Given the rarity of this coordination mode in metal carbonyl complexes, we have performed electronic structure calculations on 1a, and these data are discussed relative to the solid-state structur

Perception and beliefs about mental illness among adults in Karfi village, northern Nigeria

BACKGROUND: This study was designed to examine the knowledge, attitude and beliefs about causes, manifestations and treatment of mental illness among adults in a rural community in northern Nigeria. METHODS: A cross sectional study design was used. A pre-tested, semi-structured questionnaire was administered to 250 adults residing in Karfi village, northern Nigeria. RESULTS: The most common symptoms proffered by respondents as manifestations of mental illness included aggression/destructiveness (22.0%), loquaciousness (21.2%), eccentric behavior (16.1%) and wandering (13.3%). Drug misuse including alcohol, cannabis, and other street drugs was identified in 34.3% of the responses as a major cause of mental illness, followed by divine wrath/ God's will (19%), and magic/spirit possession (18.0%). About 46% of respondents preferred orthodox medical care for the mentally sick while 34% were more inclined to spiritual healing. Almost half of the respondents harbored negative feelings towards the mentally ill. Literate respondents were seven times more likely to exhibit positive feelings towards the mentally ill as compared to non-literate subjects (OR = 7.6, 95% confidence interval = 3.8–15.1). CONCLUSIONS: Our study demonstrates the need for community educational programs in Nigeria aimed at demystifying mental illness. A better understanding of mental disorders among the public would allay fear and mistrust about mentally ill persons in the community as well as lessen stigmatization towards such persons

A Comparison of Levels of Select Minerals in Scalp Hair Samples with Estimated Dietary Intakes of These Minerals in Women of Reproductive Age

The objective of this study was to evaluate daily intake of minerals and concentrations of minerals in hair in women of reproductive age. The study included 77 menstruating women, aged 35.9 ± 9.7 years. Subjects were divided into three groups according to age. All women were healthy. Hair samples were taken from several points of the occipital scalp. The content of minerals in hair samples was determined by flame atomic absorption spectrometry. Dietary intake of the analysed minerals was assayed on the basis of dietary intake interviews from three preceding days and evaluated using the dietetic computer programme. It was shown that calcium and iron daily intake by the women was below the recommended value. Only few women had low concentrations (below reference values) of magnesium, copper and zinc in hair. Statistically significant differences were shown between age groups. Generally, the concentrations of minerals in hair in the younger (19–30 years) and the older women (41–50 years) were higher than in hair of middle-aged women (31–40 years). The content of calcium, magnesium, iron and zinc in daily diets of women correlated inversely with copper level in their hair. Food products with good bioavailability of iron and calcium should be recommended for women of childbearing age in all age groups

Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015

SummaryBackground The Global Burden of Diseases, Injuries, and Risk Factors Study 2015 provides an up-to-date synthesis of the evidence for risk factor exposure and the attributable burden of disease. By providing national and subnational assessments spanning the past 25 years, this study can inform debates on the importance of addressing risks in context. Methods We used the comparative risk assessment framework developed for previous iterations of the Global Burden of Disease Study to estimate attributable deaths, disability-adjusted life-years (DALYs), and trends in exposure by age group, sex, year, and geography for 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks from 1990 to 2015. This study included 388 risk-outcome pairs that met World Cancer Research Fund-defined criteria for convincing or probable evidence. We extracted relative risk and exposure estimates from randomised controlled trials, cohorts, pooled cohorts, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. We developed a metric that allows comparisons of exposure across risk factors—the summary exposure value. Using the counterfactual scenario of theoretical minimum risk level, we estimated the portion of deaths and DALYs that could be attributed to a given risk. We decomposed trends in attributable burden into contributions from population growth, population age structure, risk exposure, and risk-deleted cause-specific DALY rates. We characterised risk exposure in relation to a Socio-demographic Index (SDI). Findings Between 1990 and 2015, global exposure to unsafe sanitation, household air pollution, childhood underweight, childhood stunting, and smoking each decreased by more than 25%. Global exposure for several occupational risks, high body-mass index (BMI), and drug use increased by more than 25% over the same period. All risks jointly evaluated in 2015 accounted for 57·8% (95% CI 56·6–58·8) of global deaths and 41·2% (39·8–42·8) of DALYs. In 2015, the ten largest contributors to global DALYs among Level 3 risks were high systolic blood pressure (211·8 million [192·7 million to 231·1 million] global DALYs), smoking (148·6 million [134·2 million to 163·1 million]), high fasting plasma glucose (143·1 million [125·1 million to 163·5 million]), high BMI (120·1 million [83·8 million to 158·4 million]), childhood undernutrition (113·3 million [103·9 million to 123·4 million]), ambient particulate matter (103·1 million [90·8 million to 115·1 million]), high total cholesterol (88·7 million [74·6 million to 105·7 million]), household air pollution (85·6 million [66·7 million to 106·1 million]), alcohol use (85·0 million [77·2 million to 93·0 million]), and diets high in sodium (83·0 million [49·3 million to 127·5 million]). From 1990 to 2015, attributable DALYs declined for micronutrient deficiencies, childhood undernutrition, unsafe sanitation and water, and household air pollution; reductions in risk-deleted DALY rates rather than reductions in exposure drove these declines. Rising exposure contributed to notable increases in attributable DALYs from high BMI, high fasting plasma glucose, occupational carcinogens, and drug use. Environmental risks and childhood undernutrition declined steadily with SDI; low physical activity, high BMI, and high fasting plasma glucose increased with SDI. In 119 countries, metabolic risks, such as high BMI and fasting plasma glucose, contributed the most attributable DALYs in 2015. Regionally, smoking still ranked among the leading five risk factors for attributable DALYs in 109 countries; childhood underweight and unsafe sex remained primary drivers of early death and disability in much of sub-Saharan Africa. Interpretation Declines in some key environmental risks have contributed to declines in critical infectious diseases. Some risks appear to be invariant to SDI. Increasing risks, including high BMI, high fasting plasma glucose, drug use, and some occupational exposures, contribute to rising burden from some conditions, but also provide opportunities for intervention. Some highly preventable risks, such as smoking, remain major causes of attributable DALYs, even as exposure is declining. Public policy makers need to pay attention to the risks that are increasingly major contributors to global burden. Funding Bill & Melinda Gates Foundation