Lewis Superacidic Tellurenyl Cation-Induced Electrophilic Activation of an Inert Carborane.

The aryltellurenyl cation [2-(tBuNCH)C6 H4 Te]+ , a Lewis super acid, and the weakly coordinating carborane anion [CB11 H12 ]- , an extremely weak Brønsted acid (pKa =131.0 in MeCN), form an isolable ion pair complex [2-(tBuNCH)C6 H4 Te][CB11 H12 ], in which the Brønsted acidity (pKa 7.4 in MeCN) of the formally hydridic B-H bonds is dramatically increased by more than 120 orders of magnitude. The electrophilic activation of B-H bonds in the carborane moiety gives rise to a proton transfer from boron to nitrogen at slightly elevated temperatures, as rationalized by the isolation of a mixture of the zwitterionic isomers 12- and 7-[2-(tBuN{H}CH)C6 H4 Te(CB11 H11 )] in ratios ranging from 62 : 38 to 80 : 20.

Hetero Diels-Alder Reactions of Masked Dienes Containing Heavy Group†15 Elements.

Treatment of N,C,N-chelated organopnictogen(I) compounds ArE (1-3) (Ar=2,6-(RN=CH)2 C6 H3 , E/R=As/Dmp (1), Sb/tBu (2), and Bi/tBu (3), where Dmp=2,6-Me2 C6 H3 ) with various electron-deficient alkynes RC≡CR' (R/R'=CO2 Me (DMAD), R/R'=H/CO2 Me, or R/R'=NC5 F4 ) affords different types of heterocyclic compounds. In these reactions, 1-3 act as hidden dienes and participate in hetero-Diels-Alder (DA) reactions, a feature that has been only rarely reported for heavier pnictogen compounds. In this way, reactions of 1 furnished the set of 1-arsanaphthalenes 4-6. The most likely mechanism involves two steps, that is, an arsa-DA reaction giving a 1-arsa-1,4-dihydro-iminonaphthalene, followed by CH→NH proton migration. In contrast, this reaction sequence terminates at the first step in the case of the antimony analogue 2, thus giving the 1-stiba-1,4-dihydro-iminonaphthalenes 7 and 8. Reactions of the bismuth congener 3 gave one of two products depending on the alkyne used. Reaction of 3 with DMAD gave 1-bisma-1,4-dihydro-iminonaphthalene 9, whilst its reaction with two equivalents of HC≡C(CO2 Me) gave bismacyclohexadiene (10). All compounds have been characterized by NMR, IR, and Raman spectroscopies and X-ray diffraction analysis. The experimental data were complemented by a computational study, including a description of the reaction profiles of the hetero-DA reactions and an assessment of the aromaticities of the heterocyclic naphthalene derivatives.

Reversible C=C Bond Activation by an Intramolecularly Coordinated Antimony(I) Compound.

The reaction of N,C,N-chelated stibinidene ArSb (1) (Ar=C6 H3 -2,6-(CH=NtBu)2 ) with selected N-alkyl/aryl-maleimides RN(C(O)CH)2 (R=Me, tBu, Ph) gave the addition products with bridged bicyclic [2.2.1] structure containing an antimony atom at the bridgehead position, fused with a 6-membered benzene and a 5-membered N-alkyl/aryl-pyrrolidine ring. These compounds were completely characterized. More importantly, additional studies showed that these reactions are reversible in solution, thereby representing an unprecedented reversible activation of a C=C bond by an antimony(I) compound.

Homolytic, Heterolytic, Mesolytic - As You Like It: Steering the Cleavage of a HC(sp3 )-C(sp3 )H Bond in Bis(1H-2,1-benzazaborole) Derivatives.

A set of (3,3')-bis(1-Ph-2-R-1H-2,1-benzazaborole) compounds, in which R=tBu (Bab-tBu)2 , R=Dipp (Bab-Dipp)2 or R=tBu and Dipp (Bab-Dipp)(Bab-tBu), was synthesized and fully characterized using 1 H, 11 B, 13 C, and 15 N NMR spectroscopy as well as single-crystal X-ray diffraction analysis. The central HC(sp3 )-C(sp3 )H bond with restricted rotation at the junction of both 1H-2,1-benzazaborole rings displayed an intriguing reactivity. It was demonstrated that this bond is easily mesolytically cleaved using alkali metals to form the respective aromatic 1Ph-2R-1H-2,1-benzazaborolyl anions M+ (THF)n (Bab-tBu)- (M=Li, Na, K) and K+ (THF)n (Bab-Dipp)- . Furthermore, the central HC(sp3 )-C(sp3 )H bond of bis(1H-2,1-benzazaborole)s is also homolytically cleaved either by heating or photochemical means, giving corresponding 1Ph-2R-1H-2,1-benzazaborolyl radicals (Bab-tBu). and (Bab-Dipp). , which rapidly self-terminate. Nevertheless, their formation was unambiguously established by NMR analysis of the reaction mixtures containing products of the self-termination of the radicals after heating or irradiation. (Bab-Dipp). radical was also characterized using EPR spectroscopy. Importantly, it turned out that the essentially non-polarized HC(sp3 )-C(sp3 )H bond in (Bab-tBu)2 is also cleaved heterolytically with 2 equiv of MeLi, giving the mixture of Li+ (SOL)n (Bab-tBu)- (SOL=THF or Et2 O) and lithium methyl-substituted borate complex Li+ (SOL)n (Bab-tBu-Me)- in a diastereoselective fashion.

Habitat modifies the relationship between grass and herbivore species richness in a South African savanna.

The savanna ecosystem is dominated by grasses, which are a key food source for many species of grazing animals. This relationship creates a diverse mosaic of habitats and contributes to the high grass species richness of savannas. However, how grazing interacts with environmental conditions in determining grass species richness and abundance in savannas is still insufficiently understood. In the Kruger National Park, South Africa, we recorded grass species and estimated their covers in 60 plots 50 × 50 m in size, accounting for varying proximity to water and different bedrocks. To achieve this, we located plots (i) near perennial rivers, near seasonal rivers, and on crests that are distant from all water sources and (ii) on nutrient-rich basaltic and nutrient-poor granitic bedrock. The presence and abundance of large herbivores were recorded by 60 camera traps located in the same plots. Grass cover was higher at crests and seasonal rivers than at perennial rivers and on basalts than on granites. The relationship between grass species richness and herbivore abundance or species richness was positive at crests, while that between grass species richness and herbivore species richness was negative at seasonal rivers. We found no support for controlling the dominance of grasses by herbivores in crests, but herbivore-induced microsite heterogeneity may account for high grass species richness there. In contrast, the decrease in grass species richness with herbivore species richness at seasonal rivers indicates that the strong grazing pressure over-rides the resistance of some species to grazing and trampling. We suggest that the relationships between grasses and herbivores may work in both directions, but the relationship is habitat-dependent, so that in less productive environments, the effect of herbivores on vegetation prevails, while in more productive environments along rivers the effect of vegetation and water supply on herbivores is more important.

Do invasive species perform better in their new ranges?

A fundamental assumption in invasion biology is that most invasive species exhibit enhanced performance in their introduced range relative to their home ranges. This idea has given rise to numerous hypotheses explaining "invasion success" by virtue of altered ecological and evolutionary pressures. There are surprisingly few data, however, testing the underlying assumption that the performance of introduced populations, including organism size, reproductive output, and abundance, is enhanced in their introduced compared to their native range. Here, we combined data from published studies to test this hypothesis for 26 plant and 27 animal species that are considered to be invasive. On average, individuals of these 53 species were indeed larger, more fecund, and more abundant in their introduced ranges. The overall mean, however, belied significant variability among species, as roughly half of the investigated species (N=27) performed similarly when compared to conspecific populations in their native range. Thus, although some invasive species are performing better in their new ranges, the pattern is not universal, and just as many are performing largely the same across ranges.

Disentangling the role of environmental and human pressures on biological invasions across Europe.

The accelerating rates of international trade, travel, and transport in the latter half of the twentieth century have led to the progressive mixing of biota from across the world and the number of species introduced to new regions continues to increase. The importance of biogeographic, climatic, economic, and demographic factors as drivers of this trend is increasingly being realized but as yet there is no consensus regarding their relative importance. Whereas little may be done to mitigate the effects of geography and climate on invasions, a wider range of options may exist to moderate the impacts of economic and demographic drivers. Here we use the most recent data available from Europe to partition between macroecological, economic, and demographic variables the variation in alien species richness of bryophytes, fungi, vascular plants, terrestrial insects, aquatic invertebrates, fish, amphibians, reptiles, birds, and mammals. Only national wealth and human population density were statistically significant predictors in the majority of models when analyzed jointly with climate, geography, and land cover. The economic and demographic variables reflect the intensity of human activities and integrate the effect of factors that directly determine the outcome of invasion such as propagule pressure, pathways of introduction, eutrophication, and the intensity of anthropogenic disturbance. The strong influence of economic and demographic variables on the levels of invasion by alien species demonstrates that future solutions to the problem of biological invasions at a national scale lie in mitigating the negative environmental consequences of human activities that generate wealth and by promoting more sustainable population growth.

Palladium(II) and Platinum(II) Bis(Stibinidene) Complexes with Intramolecular Hydrogen-Bond Enforced Geometries.

The coordination capability of two N,C,N pincer coordinated stibinidenes, i. e. bis(imino)- [2,6-(DippN=CH)2 C6 H3 ]Sb (1) or imino-amino- [2-(DippN=CH)-6-(DippNHCH2 )C6 H3 ]Sb (2) toward palladium(II) and platinum(II) centers was examined. In the course of this study, seven new square-planar bis(stibinidene) complexes were synthesized and characterized by NMR, IR, Raman, UV-vis spectroscopy and single crystal (sc)-X-ray diffraction analysis. In all cases, both stibinidene ligands 1 or 2 adopt trans positions, but differ significantly in the torsion angle describing mutual orientation of aromatic rings of the stibinidenes along the Sb-Pd/Pt-Sb axes. Furthermore, majority of complexes form isomers in solution most probably due to a hindered rotation around Sb-Pd/Pt bonds caused by bulkiness of 1 and 2. This phenomenon also seems to be influenced by the absence/presence of a pendant -CH2 NH- group in 1/2 that is able to form intramolecular hydrogen bonds with the adjacent chlorine atom(s) attached to the metal centers. The whole problem was subjected to a theoretical study focusing on the role of hydrogen bonds in structure architecture of the complexes. To describe the UV-vis spectra of these highly coloured complexes, TD-DFT calculations were employed. These outline differences between the stibinidene ligands, the transition metals as well as between the charge of the complexes (neutral or anionic).

N-Coordinated tellurenium(II) and telluronium(IV) cations: synthesis, structure and hydrolysis.

A set of N-coordinated tellurium(II) compounds containing either C,N-chelating ligands CNR (where CN = 2-(RNCH)C6H4, R = tBu or Dipp; Dipp = 2,6-iPr2C6H3) or N,C,N pincer ligands NCNR (where NCN = 2,6-(RNCH)2C6H4, R = tBu or Dipp) were synthesized. In the case of C,N-chelated compounds, the reaction of CNDippLi with Te(dtc)2 (where dtc = Et2NCS2) in a 1 : 1 molar ratio smoothly provided the carbamate CNDippTe(dtc) which upon treatment with 2 eq. of HCl provided the chloride CNDippTeCl. In contrast, the analogous conversion of NCNRLi with Te(dtc)2 surprisingly furnished ionic bromides [NCNRTe]Br as a result of the exchange of dtc by Br coming from nBuBr present in the reaction mixture. Furthermore, the reaction of CNDippTeCl or [NCNRTe]Br with silver salts AgX (X = OTf or SbF6) provided the expected tellurenium cations [CNDippTe]SbF6 and [NCNRTe]X. To further increase the Lewis acidity of the central atom, the oxidation of selected compounds with 1 eq. of SO2Cl2 was examined yielding stable compounds [CNtBuTeCl2]X and [NCNtBuTeCl2]X. The oxidation of the Dipp substituted compounds proved to be more challenging and an excess of SO2Cl2 was necessary to obtain the oxidized products [CNDippTeCl2]SbF6 and [NCNDippTeCl2]SbF6, which could solely be characterized in solution. Compounds [CNtBuTeCl2]OTf and [NCNtBuTeCl2]OTf were shown to undergo a controlled hydrolysis to the corresponding telluroxanes. All compounds were studied by multinuclear NMR spectroscopy in solution and for selected compounds solid state 125Te NMR spectroscopy and single-crystal X-ray diffraction analysis were performed. The Lewis acidity of the studied cations was examined by the Gutmann-Beckett method using Et3PO as the probing agent. The Te-N chalcogen bonding situation of selected compounds has also been examined computationally by a set of real-space bonding indicators.

Plant extinctions and introductions lead to phylogenetic and taxonomic homogenization of the European flora.

Human activities have altered the composition of biotas through two fundamental processes: native extinctions and alien introductions. Both processes affect the taxonomic (i.e., species identity) and phylogenetic (i.e., species evolutionary history) structure of species assemblages. However, it is not known what the relative magnitude of these effects is at large spatial scales. Here we analyze the large-scale effects of plant extinctions and introductions on taxonomic and phylogenetic diversity of floras across Europe, using data from 23 regions. Considering both native losses and alien additions in concert reveals that plant invasions since AD 1500 exceeded extinctions, resulting in (i) increased taxonomic diversity (i.e., species richness) but decreased phylogenetic diversity within European regions, and (ii) increased taxonomic and phylogenetic similarity among European regions. Those extinct species were phylogenetically and taxonomically unique and typical of individual regions, and extinctions usually were not continent-wide and therefore led to differentiation. By contrast, because introduced alien species tended to be closely related to native species, the floristic differentiation due to species extinction was lessened by taxonomic and phylogenetic homogenization effects. This was especially due to species that are alien to a region but native to other parts of Europe. As a result, floras of many European regions have partly lost and will continue to lose their uniqueness. The results suggest that biodiversity needs to be assessed in terms of both species taxonomic and phylogenetic identity, but the latter is rarely used as a metric of the biodiversity dynamics.

The reactivity of antimony and bismuth N,C,N-pincer compounds toward K[BEt3H] - the formation of heterocyclic compounds vs. element-element bonds vs. stable terminal Sb-H bonds.

The oxidative addition of CF3SO3CH2Si(CH3)3 (NpSiOTf) toward organopnictogen(I) N,C,N-pincer compounds, i.e. [2,6-(DippNCH)2C6H3]E (1-E, where E = Sb, Bi; Dipp = 2,6-iPr2C6H3) produced compounds [2,6-(DippNCH)2C6H3]E(NpSi)(OTf) (2-E, where E = Sb, Bi). By analogy, the in situ reduction of [2,6-(Me2NCH2)2C6H3]ECl2 (3-E, where E = Sb, Bi) followed by treatment with NpSiOTf or MeI gave compounds [2,6-(Me2NCH2)2C6H3]E(R)(X) (R/X = NpSi/OTf 4-E, where E = Sb, Bi; R/X = Me/I 5-Sb). The reactivity of these compounds toward 1 eq. of K[BEt3H] was examined showing remarkable differences depending both on the ligand backbone and the pnictogen used. Thus in the case of 2-E, the addition of the hydride across the imino-function was achieved thereby yielding azapnicta-heterocyclic compounds [2-(DippNCH2)-6-(DippNCH)C6H3]E(NpSi) (6-E, where E = Sb, Bi). The same reaction of 4-Bi produced dibismuthine {[2,6-(Me2NCH2)2C6H3]Bi(NpSi)}2 (7-Bi), but in the case of 4/5-Sb the analogous distibines {[2,6-(Me2NCH2)2C6H3]Sb(R)}2 (R = NpSi7-Sb, Me 8-Sb) were not formed directly and hydrides [2,6-(Me2NCH2)2C6H3]Sb(R)H (R = NpSi9-Sb, Me 10-Sb) could be isolated instead. Nevertheless, heating of both 9-Sb and 10-Sb led to an activation of a labile Sb-H bond and the formation of distibines 7/8-Sb.

Water availability, bedrock, disturbance by herbivores, and climate determine plant diversity in South-African savanna.

To identify factors that drive plant species richness in South-African savanna and explore their relative importance, we sampled plant communities across habitats differing in water availability, disturbance, and bedrock, using the Kruger National Park as a model system. We made plant inventories in 60 plots of 50 × 50 m, located in three distinct habitats: (i) at perennial rivers, (ii) at seasonal rivers with water available only during the rainy season, and (iii) on crests, at least ~ 5 km away from any water source. We predicted that large herbivores would utilise seasonal rivers' habitats less intensely than those along perennial rivers where water is available throughout the year, including dry periods. Plots on granite harboured more herbaceous and shrub species than plots on basalt. The dry crests were poorer in herb species than both seasonal and perennial rivers. Seasonal rivers harboured the highest numbers of shrub species, in accordance with the prediction of the highest species richness at relatively low levels of disturbance and low stress from the lack of water. The crests, exposed to relatively low pressure from grazing but stressed by the lack of water, are important from the conservation perspective because they harbour typical, sometimes rare savanna species, and so are seasonal rivers whose shrub richness is stimulated and maintained by the combination of moderate disturbance imposed by herbivores and position in the middle of the water availability gradient. To capture the complexity of determinants of species richness in KNP, we complemented the analysis of the above local factors by exploring large-scale factors related to climate, vegetation productivity, the character of dominant vegetation, and landscape features. The strongest factor was temperature; areas with the highest temperatures reveal lower species richness. Our results also suggest that Colophospermum mopane, a dominant woody species in the north of KNP is not the ultimate cause of the lower plant diversity in this part of the park.

Beyond simple hetero Diels-Alder cycloadditions. A new type of element-ligand cooperativity at N,C,N-coordinated arsinidene and stibinidene centres in the reaction with an electron-deficient alkyne.

The reactivity of two types of organopnictogen(I) N,C,N-pincer ligand coordinated compound, i.e. [2,6-(DippNCH)2C6H3]E (1-E, where E = As, Sb, Bi; Dipp = 2,6-iPrC6H3) and [2-(DippNCH)-6-(DippNHCH2)C6H3]E (6-E, where E = As or Sb), toward an electron-deficient alkyne, i.e. dimethyl acetylenedicarboxylate (DMAD), is reported. All reactions represent remarkable examples of element-ligand cooperation (ELC). In the first step, all compounds react via dearomatization of a latent heteropnictole ring producing rare examples of hetero Diels-Alder (DA) adducts. These compounds then smoothly convert to 1-arsanaphthalenes via hydrogen migration, thereby recovering the aromatic 10π-electron system. Furthermore, in the case of bis(imino) derivatives of 1-E, heating of DA adducts in pyridine led to a hydrogenation of the triple bond of DMAD with the concomitant recovery of the univalent pnictinidene centre, which is in turn able to activate the second molecule of DMAD. In contrast, the non-symmetric derivative of 6-As upon heating in pyridine produced bicyclic trivalent arsenic compounds as a result of an attack of the pendant secondary NH group into the arsa-heterocyclic system. For 6-Sb, a remarkable stoichiometric hydrogenation of the DMAD molecule was observed by NMR spectroscopy involving the reductive elimination of dimethylfumarate in the final step of the reaction sequence. The whole study is accompanied by a theoretical survey that describes the main thermodynamic parameters of the reported reactions and explains the reaction pathways observed in the experiments.

Thirteen moth species (Lepidoptera, Erebidae, Noctuidae) newly recorded in South Africa, with comments on their distribution.

Background: Thanks to the high diversity of ecosystems and habitats, South Africa harbours tremendous diversity of insects. The Kruger National Park, due to its position close to the border between two biogeographic regions and high heterogeneity of environmental conditions, represents an insufficiently studied hotspot of lepidopteran diversity. During our ecological research in the Kruger National Park, we collected abundant moth material, including several interesting faunistic records reported in this study. New information: We reported 13 species of moths which had not yet been recorded in South Africa. In many cases, our records represented an important extension of the species' known distribution, including two species (Ozarbagaedei and O.persinua) whose distribution ranges extended into the Zambezian biogeographic region. Such findings confirmed the poor regional knowledge of lepidopteran diversity.

Ecological impacts of invasive alien plants: a meta-analysis of their effects on species, communities and ecosystems.

Biological invasions cause ecological and economic impacts across the globe. However, it is unclear whether there are strong patterns in terms of their major effects, how the vulnerability of different ecosystems varies and which ecosystem services are at greatest risk. We present a global meta-analysis of 199 articles reporting 1041 field studies that in total describe the impacts of 135 alien plant taxa on resident species, communities and ecosystems. Across studies, alien plants had a significant effect in 11 of 24 different types of impact assessed. The magnitude and direction of the impact varied both within and between different types of impact. On average, abundance and diversity of the resident species decreased in invaded sites, whereas primary production and several ecosystem processes were enhanced. While alien N-fixing species had greater impacts on N-cycling variables, they did not consistently affect other impact types. The magnitude of the impacts was not significantly different between island and mainland ecosystems. Overall, alien species impacts are heterogeneous and not unidirectional even within particular impact types. Our analysis also reveals that by the time changes in nutrient cycling are detected, major impacts on plant species and communities are likely to have already occurred.

Does the intensive grazing and aridity change the relations between the dominant shrub Artemisia kopetdaghensis and plants under its canopies?

The interspecific plant interactions along grazing and aridity stress gradients represent a major research issue in plant ecology. However, the combined effects of these two factors on plant-plant interactions have been poorly studied in the northeast of Iran. To fill this knowledge gap, 144 plots were established in 12 study sites with different grazing intensities (high vs. low) and climatic characteristics (arid vs. semiarid) in northeastern Iran. A dominant shrub, Artemisia kopetdaghensis, was selected as the model species. Further, we studied changes in plant life strategies along the combined grazing and aridity stress gradients. In this study, we used relative interaction indices calculated for species richness, Shannon diversity, and species cover to determine plant-plant interactions using linear mixed-effect models (LMM). The indicator species analysis was used to identify the indicator species for the undercanopy of shrub and for the adjacent open areas. The combined effects of grazing and aridity affected the plant-plant interactions and plant life strategies (CSR) of indicator species. A. kopetdaghensis showed the highest facilitation effect under high stress conditions (high grazing, high aridity), which turned into competition under the low stress conditions (low grazing, low aridity). In the arid region, the canopy of the shrub protected ruderals, annual forbs, and grasses in both high and low grazing intensities. In the semiarid region and high grazing intensity (low aridity/high grazing), the shrubs protected mostly perennial forbs with C-strategy. Our findings highlight the importance of context-dependent shrub management to restore the vegetation damaged by the intensive grazing.

(N),C,N-Coordinated Heavier Group 13-15 Compounds: Synthesis, Structure and Applications.

The aim of this review is to summarize recent achievements in the field of (N),C,N-coordinated group 13-15 compounds not only regarding their synthesis and structure, but mainly focusing on their potential applications. Relevant compounds contain various types of N-coordinating ligands built up on an ortho-(di)substituted phenyl platform. Thus, group 13 and 14 derivatives were used as single-source precursors for the deposition of semiconducting thin films, as building blocks for the preparation of high-molecular polymers with remarkable optical and chemical properties or as compounds with interesting reactivity in hydrometallation processes. Group 15 derivatives function as catalysts in the Mannich reaction, in the allylation of aldehydes or activation of CO2 . They were used as transmetallation reagents in transition metal catalysed coupling reactions. The univalent species serve as ligands for transition metals, activate alkynes or alkenes and are utilized as catalysts in the transfer hydrogenation of azo-compounds.

Effects of livestock grazing on soil, plant functional diversity, and ecological traits vary between regions with different climates in northeastern Iran.

Understanding the responses of vegetation characteristics and soil properties to grazing in different precipitation regimes is useful for the management of rangelands, especially in the arid regions. In northeastern Iran, we studied the responses of vegetation to livestock grazing in three regions with different climates: arid, semiarid, and subhumid. In each region, we selected 6-7 pairwise sampling areas of high versus low grazing intensity and six traits of the present species were recorded on 1 m2 plots-five grazed and five ungrazed in each area. The overall fertility was compared using the dissimilarity analysis, and linear mixed-effect models were used to compare the individual fertility parameters, functional diversity indices, and species traits between the plots with high and low grazing intensity and between the climatic regions. Both climate and grazing, as well as their interaction, affected fertility parameters, functional diversity indices, and the representation of species traits. Grazing reduced functional evenness, height of the community, the representation of annuals, but increased the community leaf area. In the subhumid region, grazing also reduced functional richness. Further, grazing decreased the share of annual species in the semiarid region and seed mass in the arid region. Larger leaf area and seed mass, smaller height and lower share of annuals were associated with intensive grazing. Species with large LA and seed mass, lower height and perennials can be therefore presumed to tolerate trampling and benefit from high nutrient levels, associated with intensive grazing. By providing a detailed view on the impacts of overgrazing, this study highlights the importance of protection from grazing as an effective management tool for maintaining the pastoral ecosystems. In general, the composition of plant traits across the pastures of northeastern Iran was more affected by intensive grazing than by the differences in climate.

Antimony(i) → Pd(ii) complexes with the (µ-Sb)Pd2 coordination framework.

The reaction of the antimony(i) compound ArSb (1) (where Ar = C6H3-2,6-(CH[double bond, length as m-dash]NtBu)2) with various dimeric allyl palladium(ii) complexes [Pd(η3-allyl)(µ-X)]2 (where allyl = C3H5 or C3H4Me; X = Cl or CF3CO2) in a 1 : 1 stoichiometric ratio gave unique complexes with the µ-ArSb moiety bridging two palladium fragments, i.e. [{Pd(η3-C3H5)Cl}2(µ-ArSb)] (2), [{Pd(η3-C3H4Me)Cl}2(µ-ArSb)] (3) and [{Pd(η3-C3H5)(CF3CO2)}2(µ-ArSb)] (4). Compound 1 serves formally as a 4e donor in 2-4. The treatment of 2 with another equivalent of ArSb led to the formation of the [Pd(η3-C3H5)(Cl)(µ-ArSb)] complex (5), proving that 1 is able to function as a 2e donor in target complexes as well. The structures of 2-5 were described in detail both in solution (NMR and mass spectrometry) and in the solid state (single crystal X-ray diffraction analysis). DFT methods were used to compare bonding in the 1 : 1 (5) and 1 : 2 (2) complexes. Furthermore, a comprehensive 121Sb Mössbauer spectroscopic investigation of complexes 2 and 5 along with parent ArSbCl2 (6) and 1 was performed. For comparison, complexes [Fe(CO)4(ArSb)] (7) and [Mo(CO)5(ArSb)] (8) were also included in this study.