Examples Of Such Species Research Articles

Double axial stabilization of a carbenium ion via convergent PO → C+ tetrel bonding.

Our efforts in carbocation chemistry have led us to target examples of such species stabilized intramolecularly by tetrel bonding. Described here is an example of such a compound in which a triaryl carbenium is stabilized intramolecularly by two convergent PO → Ccarbenium interactions, as confirmed by structural studies. The formation of this new motif favorably impacts the reversibility of the first and second reduction of the carbenium center. It also has profound influence on the Lewis acidity of the carbenium center which is lower than that of the unsubstituted parent carbenium by seven orders of magnitude.

Spatial variation of parrotfish assemblages at oceanic islands in the western Caribbean: evidence of indirect effects of fishing?

Fish populations that bear considerable pressure levels tend to show a decline in the average size of individuals, with the small and unexploited species replacing the large and exploited ones. It is important to carry on with their characterization in areas where they are becoming an important source of food for local human populations. An example of such species are parrotfishes, whose responses to external factors such as fishing need to be understood and predicted. In this study, we used a diver-operated stereo-video to examine individual body size, sex ratios and proportion of species of the parrotfish assemblage and analyze them on a qualitative fishing pressure gradient at four oceanic islands in the Colombian Caribbean. We reported over 10,000 occurrences of eleven parrotfish species, of which we estimated the total length of over 90%, grouping them into three size categories (large, medium, and small). Our data showed a spatial variation of parrotfishes' abundances, biomass, and individual body size. Observed differences are size-category-dependent throughout the qualitative fishing pressure. In general, the medium-bodied species had smaller sizes, lower abundances, and thus lower contribution to the total parrotfish biomass at the most heavily fished island. Unexpectedly, we found evidence of possible indirect effects over the small-bodied species Scarus iseri and Scarus taeniopterus with significantly greater abundances, and larger sizes of males of S. iseri, at the higher fishing pressure sites. Overall, our data highlights the extent of the spatial variation in the parrotfish communities at relatively short distances, and present new insights into the responses of parrotfish species on a spectrum of body sizes along a gradient of human pressure.

Role of enemy release and hybridization in the invasiveness of Impatiens balfourii and I. glandulifera.

Comparative studies with taxonomically and geographically paired alien species that exhibit different degrees of success in their invasions may help to identify the factors that determine invasiveness. Examples of such species in Europe include the noninvasive Impatiens balfourii and invasive I. glandulifera. We tested whether the low invasiveness of I. balfourii in Europe may be explained by strong pressure from local enemies. Earlier studies of these two species provided support for their hybridization. We tested this phenomenon as the potential occurrence of I. glandulifera × I. balfourii hybrids might promote the evolution of the invasiveness of I. balfourii. Both species were germinated from seeds collected in 2015 on the Swiss-Italian border in Insubria and utilized in three experiments: (1) a common garden enemy release test (leaf damage or pest pressure), (2) a test of the pressure exerted by a generalist enemy and (3) hybridization test. In the first test, the effect of enemies was assessed by the level of leaf damage and the number of pests. In the second test, a food choice experiment with a generalist herbivore (Cepaea snails) was performed. In the hybridization test, the plants were placed in a climatic chamber for self-pollination and hand cross-pollination. Analyses of enemy release and Cepaea snail preference revealed that I. balfourii experienced higher enemy pressure than I. glandulifera; however, this was not reflected in the performance of the plants. Although I. glandulifera was larger, I. balfourii had greater fecundity. Thus, the invasion success of I. glandulifera could not be unambiguously attributed to its greater degree of release from enemies compared with the noninvasive I. balfourii. Additionally, we did not obtain any evidence of hybridization between the two species. Thus, we obtained no support for the hypothesis that the evolution of the invasiveness of I. balfourii could be enhanced through hybridization with I. glandulifera.

Modeling of selenocysteine-derived reactive intermediates utilizing a nano-sized molecular cavity as a protective cradle.

In the biological functions of selenoproteins, various highly reactive species formed by oxidative modification of selenocysteine residues have been postulated to play crucial roles. Representative examples of such species are selenocysteine selenenic acids (Sec-SeOHs) and selenocysteine selenenyl iodides (Sec-SeIs), which have been widely recognized as important intermediates in the catalytic cycle of glutathione peroxidase (GPx) and iodothyronine deiodinase, respectively. However, examples of even spectroscopic observation of Sec-SeOHs and Sec-SeIs in either protein or small-molecule model systems remain elusive so far, most likely due to their notorious instability. For the synthesis of small-molecule model compounds of these reactive species, it is essential to suppress their very facile bimolecular decomposition such as self-condensation and disproportionation. Here we outline a novel method for the synthesis of stable small-molecule model compounds of the selenocysteine-derived reactive species, in which a nano-sized molecular cavity is used as a protective cradle to accommodate the reactive selenocysteine unit. Stabilization by the molecular cradle led to the successful synthesis of Sec-SeOHs, which are stable in solution at low temperatures, and a Sec-SeI, which can be isolated as crystals. The catalytic cycle of GPx was investigated using the NMR-observable Sec-SeOH models, and all the chemical processes proposed for the catalytic cycle of GPx, including the bypass process from Sec-SeOH to the corresponding cyclic selenenyl amide, were experimentally confirmed. Detailed protocols for the syntheses of selenopeptide derivatives bearing the molecular cradle and for the spectroscopic monitoring of their reactions are provided.

Impacts of a Non-indigenous Ecosystem Engineer, the American Beaver (Castor canadensis), in a Biodiversity Hotspot

Non-native species having high per capita impacts in invaded communities are those that modulate resource availability and alter disturbance regimes in ways that are biologically incompatible with the native biota. In areas where it has been introduced by humans, American beaver (Castor canadensis) is an iconic example of such species due to its capacity to alter trophic dynamics of entire ecosystems and create new invasional pathways for other non-native species. The species is problematic in several watersheds within the Southern California-Northern Baja California Coast Ecoregion, a recognized hotspot of biodiversity, due to its ability to modify habitat in ways that favor invasive predators and competitors over the region's native species and habitat. Beaver was deliberately introduced across California in the mid-1900s and generally accepted as non-native to the region up to the early 2000s; however, articles promoting the idea that beaver may be a natural resident have gained traction in recent years, due in large part to the species' charismatic nature rather than by presentation of sound evidence. Here, we discuss the problems associated with beaver disturbance and its effects on conserving the region's native fauna and flora. We refute arguments underlying the claim that beaver is native to the region, and review paleontological, zooarchaeological, and historical survey data from renowned field biologists and naturalists over the past ~160 years to show that no evidence exists that beaver arrived by any means other than deliberate human introduction. Managing this ecosystem engineer has potential to reduce the richness and abundance of other non-native species because the novel, engineered habitat now supporting these species would diminish in beaver-occupied watersheds. At the same time, hydrologic functionality would shift toward more natural, ephemeral conditions that favor the regions' native species while suppressing the dominance of the most insidious invaders.

How Does the Engineering Species Affect Forest Ecosystems? Changes in Germination and Development Rate of Non-Forest Species Under the Nests of Ardea cinerea L.

Abstract An ecosystem engineer is a species that indirectly changes the availability of resources for other organisms via physical modification of the habitat. A good example of such species is Ardea cinerea L. – a big waterbird that forms colonies up to a few hundreds of nests during the breeding season. The colonies modify the habitat in the close vicinity of the nests mainly through heavy input of organic matter (feces, dropped or regurgitated food leftovers, eggshells, dead birds, etc.), which in turn affects vegetation. In our previous study, we observed that the probability of occurrence of non-forest species under the nests was 29.5 times higher in control plots in two types of forest vegetation (oligotrophic pine forest and riparian mixed forest). Adaptation for long-distance dispersal turned out to be insignificant for the probability of species occurrence, which suggested that the diaspores of those species must have been present in the forest soil before the establishment of the grey heron colony. In the present study, we used the seedling emergence method to compare the structure of the soil seed bank in breeding sites and control plots in two forest ecosystems mentioned above. We also tested whether the increased amount of nitrates in soil had a positive effect on the rate of germination and growth of seedlings. The results have shown that some reservoir of ruderal species was indeed present in the control plots, although their amount was higher under the heronries. We have proved that the number of germinating seeds of ruderal species depends on the concentration of nitrate in the soil of the pine forest. Comparison of the dry weight of 30- and 60-day-old seedlings of Rumex acetosella (pine forest) and Betula pendula (riparian forest) from the control and breeding sites showed an increased size of seedlings coming from the breeding sites of both forest communities.

Feeding – Cleaning Trade-Off: Manta Ray “Decision-Making” as a Conservation Tool

Identifying critical aggregation sites and behavioral patterns of imperiled species contributes to filling knowledge gaps essential for their conservation. Manta rays present a prominent example of such species, the populations of which are declining globally due to directed fishery, by-catch, and other anthropogenic stressors. Our goal was to explore manta ray aggregation sites in the Philippines in order to determine the factors governing the mantas’ visits – a knowledge gap essential to understand manta ecology, facilitate ecosystem-based fishery management, and promote sustainable manta-based ecotourism. Diving surveys, environmental conditions assessment, and autonomous cameras were employed to study manta behavior and visit patterns to a cleaning station cluster on a commonly fished seamount, visited by both Mobula birostris and Mobula alfredi. Our findings reveal several environmental conditions (e.g. sea state, moon illumination, and flow) that serve as predictors of manta presence/absence at the site. We suggest that these conditions affect both the behavior of the manta’s food (i.e. the spatial distribution of plankton) and the cleaner wrasses’ cleaning effectiveness, which consequently influence manta activity. The findings suggest a trade-off between cleaning and foraging: i.e. mantas tend to visit the cleaning stations when environmental conditions are less favorable for foraging but suitable for effective cleaning; while being absent from the cleaning stations when environmental conditions form plankton aggregates, ideal for efficient feeding. This study sheds light on manta behavior and habitat use on dynamic small spatio-temporal scales (i.e. hundreds of meters to a few kilometers, hours to days), and may be applied in the planning of marine protected areas and in fishery management, as well as contribute to enhancing sustainable exploitation of manta rays by local stakeholders, such as ecotourism operators.

New insights into oximic ligands: Synthesis and characterization of 1D chains by the use of pyridine 2-amidoxime and polycarboxylates

The initial study of the ligand blend pyridine-2-amidoxime (pyaoxH2)/1,4-benzenedicarboxylic (H2bdc) or 1,3,5-benzenetricarboxylic acid (H3btc) provided access to four 1D coordination polymers, [Zn(bdc)(pyaoxH2)(DMF)]n (1), {[Ni(bdc)(pyaoxH2)2]·2DMF}n (2·2DMF), {[Mn(bdc)(pyaoxH2)2]·2DMF}n (3·2DMF) and [Ni(Hbtc)(pyaoxH2)2]n (5), and the discrete (0D) compound [Ni(H2btc)2(pyaoxH2)2]·2H2O (4·2H2O), whose further polymerization yielded 5. These compounds are the first metal coordination polymers bearing pyaoxH2 and rare examples of such species with any type of a 2-pyridyl oxime. The crystal structures of the compounds have been determined by single crystal X-ray crystallography, whereas their identity, purity and stability were confirmed by pxrd studies. Thermal stability studies were performed in 1, 2·2DMF, 4·2H2O and 5. The photoluminescence properties of 1 have been studied and revealed a maximum emission peak at 440 nm and a visible shoulder at 467 nm, assigned to the pyaoxH2 and bdc2− ligands, respectively.

η1:η2-P-Pyrazolylphosphaalkene Complexes of Ruthenium(0)

An extended range of novel ruthenium phosphaalkene complexes of the type [Ru{η1-N:η2-P,C-P(pz′)=CH(SiMe2R)}(CO)(PPh3)2] (R = Tol, C6H4CF3-p; pz′ = pzMe2, pzCF3, pzMe,CF3; R = Me, C6H4CF3-p; pz′ = pzPh) have been prepared from the respective ruthenaphosphaalkenyls [Ru{P=CH(SiMe2R)}Cl(CO)(PPh3)2] upon treatment with Lipz′. Where R = C6H4CF3-p and pz′ = pzMe2 the complex is characterized by single crystal X-ray diffraction, only the second example of such species being structurally characterized. This indicates enhanced pyramidalisation of the alkenic carbon center when compared with precedent data (R = Me, pz′ = pz) implying an enhanced Ru→π*PC contribution, which can be correlated with the greater donor power of pzMe2. This is similarly reflected in spectroscopic data that reveal significant influence of the pyrazolyl substituents upon the phosphaalkene, stronger donors imparting significantly enhanced shielding to phosphorus; in contrast, a much lesser influence if noted for the silyl substituents.

Cyclo-Stannasiloxanes Containing both Oxygen Atoms and Methylene Moieties within the Ring and Formation of Related Organotin Oxo Clusters

The syntheses of the 8-membered stannasiloxanes cyclo-[RR′SnOSi(Me2)CH2]2 (5, R = R′ = Ph; 6, R = R′ = t-Bu; 7, R = Me2N(CH2)3, R′ = Ph) is reported. These react with organoelement oxides, providing the novel metallasiloxanes cyclo-[Me2SiCH2(RR′)SnOMO] (8, R = R′ = Ph, M = t-Bu2Sn; 9, R = R′ = t-Bu, M = t-Bu2Sn; 10, R = Me2N(CH2)3, R′ = Ph, M = t-Bu2Sn; 11, R = Me2N(CH2)3, R′ = Ph, M = Ph2Ge). Among these, compound 11 is the first example of such species being composed of four different group 14 elements in the 6-membered-ring skeleton. On contact with moist air compound 8 surprisingly undergoes Sn–Ph bond cleavage, giving the diorganotinoxo cluster [PhSn(CH2Me2SiO)Sn(μ3-O)(μ-OH)t-Bu2]2 (12), which shows a ladder-type structure. The latter reacts with 2 molar equiv of t-Bu2SnO, affording the Sn6-diorganotin oxo cluster [t-Bu2(μ-OH)Sn(μ3-O)SnPh(CH2Me2SiO)Sn-t-Bu2(μ3-O)]2 (13). The compounds have been characterized by NMR spectroscopy, electrospray mass spectrometry, and in the case of compounds 5–7, 12, and 13 also by single-crystal X-ray diffraction analysis.

Ideas and perspectives: on the emission of amines from terrestrial vegetation in the context of new atmospheric particle formation

Abstract. In this article we summarise recent science which shows how airborne amines, specifically methylamines (MAs), play a key role in new atmospheric particle formation (NPF) by stabilising small molecule clusters. Agricultural emissions are assumed to constitute the most important MA source, but given the short atmospheric residence time of MAs, they can hardly have a direct impact on NPF events observed in remote regions. This leads us to the presentation of existing knowledge focussing on natural vegetation-related MA sources. High MA contents as well as emissions by plants was already described in the 19th century. Strong MA emissions predominantly occur during flowering as part of a pollination strategy. The behaviour is species-specific, but examples of such species are common and widespread. In addition, vegetative plant tissue exhibiting high amounts of MAs might potentially lead to significant emissions. The decomposition of organic material constitutes another, potentially ubiquitous, source of airborne MAs. These mechanisms would provide sources, which could be crucial for the amine's role in NPF, especially in remote regions. Knowledge about vegetation-related amine emissions is, however, very limited, and thus it is also an open question how global change and the intensified cycling of reactive nitrogen over the last 200 years have altered amine emissions from vegetation with a corresponding effect on NPF.

Prioritizing West African medicinal plants for conservation and sustainable extraction studies based on market surveys and species distribution models

Sub-Saharan African human populations rely heavily on wild-harvested medicinal plants for their health. The trade in herbal medicine provides an income for many West African people, but little is known about the effects of commercial extraction on wild plant populations. Detailed distribution maps are lacking for even the most commonly traded species. Here we combine quantitative market surveys in Ghana and Benin with species distribution models (SDMs) to assess potential species’ vulnerability to overharvesting and to prioritize areas for sustainable extraction studies. We provide the first detailed distribution maps for 12 commercially extracted medicinal plants in West Africa. We suggest an IUCN threat status for four forest species that were not previously assessed (Sphenocentrum jollyanum, Okoubaka aubrevillei, Entada gigas and Piper guineense), which have narrow distributions in West Africa and are extensively commercialized. As SDMs estimate the extent of suitable abiotic habitat conditions rather than population size per se, their output is of limited use to assess vulnerability for overharvesting of widely distributed species. Examples of such species are Khaya senegalensis and Securidaca longipedunculata, two trees that were reported by market vendors as becoming increasingly scarce in the wild. Field surveys should start in predicted suitable habitats closest to urban areas and main roads, as commercial extraction likely occurs at the shortest cost distance to the markets. Our study provides an example of applying SDMs to conservation assessments aiming to safeguard provisioning ecosystems.

Evolutionary ecology of microsporidia associated with the invasive ladybird Harmonia axyridis.

Invasive species are characterized by the rapid growth and spread of their populations after establishing a foothold in new habitats, and there are now many examples of such species negatively affecting biodiversity and the economy. It is unclear why some species can become successful invaders, whereas most (even if closely related) remain noninvasive. We previously proposed a hypothesis that parasites associated with invading species can promote their invasive success if they are harmless toward the invaders but harmful to their competitors and/or predators in the newly colonized habitat. Here we discuss whether microsporidia that have recently been discovered in the invasive ladybird Harmonia axyridis contribute to its invasive success. We show that all H. axyridis beetles sourced from diverse collection sites all over the world carry abundant microsporidia. This suggests that both native and invasive H. axyridis populations are associated with these tolerated parasites, which were likely to have existed in native populations before expansion rather than being acquired in newly colonized areas. We describe the pathogenesis of the microsporidia during different developmental stages of H. axyridis and we address the possibility that the predation of its infected eggs and larvae by competing native ladybird species may lead to their infection and ultimately to their decline. Finally, we discuss our initial hypothesis: microsporidia that are tolerated by an invasive vector insect can be active against susceptible native competitors and/or predator species.

Self-Assembly of Water-Mediated Supramolecular Cationic Archimedean Solids

Understanding the self-assembly of small structural units into large supramolecular assemblies remains one of the great challenges in structural chemistry. We have discovered that tetrahedral supramolecular cages, exhibiting the shapes of Archimedean solids, can be self-assembled by hydrogen bonding interactions using tricationic N-donors (1 or 2) in cooperation with water (W). Single crystal X-ray analysis shows that cage (2)4(W)6, assembled in an aqueous solution of cation 2 and KPF6, consists of four tripodal trications linked by six water monomers and resembles the shape of a truncated tetrahedron. Similarly, cage (1)4(W6)4 spontaneously self-assembles in an aqueous solution of cation 1 and NH4PF6 and consists of four tripodal cations and four water hexamers. Here, each of the four (H2O)6 units act as tritopic nodes between three distinct tripodal cations forming a polyhedron similar to the cantellated tetrahedron. These two well-defined cages are assembled via total of 12 and 36 hydrogen bonds, respectively. Both cages possess interior solvent-accessible volumes exceeding 1000 Å3. Furthermore, each one of the (H2O)6 clusters in face-centered cubic structure 1b acts as a node between two distinct (1)4(W6)4 units, and thus a solvent-filled tubular three-dimensional network (tube diameter of ∼6.5 Å) is generated that mimics the structure of diamond at the nanometer scale. To our knowledge, this is the first example of such species being formed entirely via hydrogen bonding interactions.

Rational Tuning of the Thiolate Donor in Model Complexes of Superoxide Reductase: Direct Evidence for a trans Influence in FeIII−OOR Complexes

Iron peroxide species have been identified as important intermediates in a number of nonheme iron as well as heme-containing enzymes, yet there are only a few examples of such species either synthetic or biological that have been well characterized. We describe the synthesis and structural characterization of a new series of five-coordinate (N4S(thiolate))Fe(II) complexes that react with tert-butyl hydroperoxide ((t)BuOOH) or cumenyl hydroperoxide (CmOOH) to give metastable alkylperoxo-iron(III) species (N4S(thiolate)Fe(III)-OOR) at low temperature. These complexes were designed specifically to mimic the nonheme iron active site of superoxide reductase, which contains a five-coordinate iron(II) center bound by one Cys and four His residues in the active form of the protein. The structures of the Fe(II) complexes are analyzed by X-ray crystallography, and their electrochemical properties are assessed by cyclic voltammetry. For the Fe(III)-OOR species, low-temperature UV-vis spectra reveal intense peaks between 500-550 nm that are typical of peroxide to iron(III) ligand-to-metal charge-transfer (LMCT) transitions, and EPR spectroscopy shows that these alkylperoxo species are all low-spin iron(III) complexes. Identification of the vibrational modes of the Fe(III)-OOR unit comes from resonance Raman (RR) spectroscopy, which shows nu(Fe-O) modes between 600-635 cm(-1) and nu(O-O) bands near 800 cm(-1). These Fe-O stretching frequencies are significantly lower than those found in other low-spin Fe(III)-OOR complexes. Trends in the data conclusively show that this weakening of the Fe-O bond arises from a trans influence of the thiolate donor, and density functional theory (DFT) calculations support these findings. These results suggest a role for the cysteine ligand in SOR, and are discussed in light of the recent assessments of the function of the cysteine ligand in this enzyme.

Second Half-Reaction of Nitric Oxide Synthase: Computational Insights into the Initial Step and Key Proposed Intermediate

Density functional theory methods have been employed to investigate possible first steps in the second half-reaction of the mechanism of nitric oxide synthases (NOSs). In particular, reactions and complexes formed via transfer of either or both hydrogens of the substrates (NHA) -NHOH group to the Fe-bound O2 were considered. For each of these pathways, the effect of adding an extra electron from tetrahydrobiotperin (H4B) was also examined. The preferred initial pathway involves the simultaneous transfer of both hydrogens of the -NHOH group to the Fe(heme)-O2, without an additional electron, to give the Fe(heme)-HOOH species which lies only marginally higher in energy, 2.5 kcal mol(-1) or less, than the initial bound active site. An alternative mechanism in which only the -NH- proton of the -NHOH group is transferred to the Fe(heme)-O2 to give an Fe(heme)-OOH derivative is found to require only slightly more energy, approximately 2 kcal mol(-1). However, transfer of the proton back to the -NOH nitrogen occurs without a barrier at 298.15 K. Tetrahedral intermediates in which the Fe(heme)-O2 has attached at the guanidinium carbon (C(guan)) of NHA, that is, forms an Fe(heme)-O2-C(guan) link, have also been investigated. All examples of such species considered, that is, with or without hydrogen or electron transfers, lie significantly higher in energy by at least 29.0 kcal mol(-1) than the initial bound active site. Thus, it is suggested that such complexes are not mechanistically feasible. The implications of the present findings for the second half-reaction are also discussed.

On the origin of the optical properties of humic substances.

Absorption and fluorescence spectroscopy and laser photobleaching experiments were employed to probe the origins of the optical properties of humic substances (HS). Luminescence quantum yields and the wavelengths of maximum emission were acquired for Suwannee River humic acid (SRHA) and fulvic acid (SRFA) at an extensive series of excitation wavelengths across the ultraviolet and visible. Laser irradiation at a series wavelength across the ultraviolet and visible was further employed to destroy selectively chromophores absorbing at specific wavelengths, using absorption spectroscopy to follow the absorption losses with irradiation time. The results provide unequivocal evidence that the absorption and emission spectra of these materials cannot result solely from a simple linear superposition of the spectra of numerous independent chromophores. Instead, the long wavelength absorption tail of HS (>350 nm) appears to arise from a continuum of coupled states. We propose that this behavior results from intramolecular charge-transfer interactions between hydroxy-aromatic donors and quinoid acceptors formed by the partial oxidation of lignin precursors. We further propose that these donor-acceptor interactions may be a common phenomenon, occurring within all natural hydroxy- or polyhydroxy-aromatic polymers that form appropriate acceptors upon partial oxidation. Examples of such species include lignin, polyphenols, tannins, and melanins.

Access to Isolable Azomethine Ylides by Photochemical Transformation of 2,3‐Dihydroisoxazoles.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Access to Isolable Azomethine Ylides by Photochemical Transformation of 2,3‐Dihydroisoxazoles

AbstractPhotochemical excitation of the 2,3‐dihydroisoxazoles 19−21 resulted in the formation of the stable azomethine ylides 22, 25, and 28, representing the first isolable examples of such species bearing stabilizing groups only at one end of the 1,3‐dipole. The UV and NMR spectroscopic data of the photoproducts clearly indicate that the iminium and the anionic parts of the azomethine ylide systems are not planar. This conclusion is unambiguously confirmed by crystal structure analysis of 25b, in which a twist angle of 73° was determined between the two polar moieties. In the case of 25d the rotation barrier around the central CN bond amounts to 16 kcal/mol at 333 K. In line with the unusual stability of the ylides is their low reactivity against dipolarophiles. Only the highly reactive N‐methyltriazolidinedione gives formation of the products 33a, 35a−c, and 41, but these are the result not of an initial 1,3‐dipolar cycloaddition but rather of a formal [4+2] addition with involvement of 34a, 36a−c, and 41 as unstable primary products. On heating in refluxing toluene the azomethine ylides are transformed into annulated pyrrole systems (42/43, 46/47, 48/49). In contrast to other examples, the direct thermal transformation of the annulated 2,3‐dihydroisoxazoles into pyrroles is not successful, but the reaction can be achieved by simultaneous thermal and photochemical activation, as shown for the conversion of 19 into the pyrroles 42/43. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

A first transition series pseudotetrahedral oxynitride anion: synthesis and characterization of Ba(2)VO(3)N.

Ammonolysis of reactive oxide precursors affords the vanadium(V) phase Ba(2)VO(3)N that is shown by X-ray and neutron powder diffraction and Raman spectroscopy to contain pseudotetrahedral VO(3)N(4-) anions. This is the first example of such species for the first transition series metals.