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In this study, we aimed to assess the processes controlling compositional change in a Northern Andean paramo highly affected by human-induced disturbances over the last few decades (La Rusia, Colombia). Along the 3000–3800 m asl altitudinal range, we randomly sampled fifty 10 × 10 m plots. Therein, we measured altitude and variables related to soil conditions (i.e., moisture, nutrient contents, bulk density, and texture), occurrence of human-induced disturbances (i.e., fire, vegetation clearing, potato cultivation, and cattle grazing), and land-use history. We also recorded richness and abundance of plant species, identifying them as exotic or native. We differentiated four groups of plots according to their species composition. The groups had significant differences in altitude, soil conditions, land-use history, and particularly, in richness of exotic species and exotic/native cover ratio. They could be ascribed to shrub- and grass-paramo vegetation types based on their relative dominance of woody and herbaceous species; however, these groups were not arranged according to the hypothetical composition of altitudinal belts, but rather formed a mosaic of patches. This mosaic was determined not only by altitude but also by soil conditions and disturbance history of sites. Our results corroborate recent findings which highlight shrub- and grass-paramo vegetation types as patches of contrasting species composition and structure that depend on local environmental variables, as well as human-induced disturbances as a major determinant of compositional discontinuities in these ‘high mountain’ tropical ecosystems. Resumen Este trabajo fue realizado con el objetivo de evaluar los procesos que controlan los cambios composicionales en un paramo fuertemente afectado por las perturbaciones de origen humano durante las ultimas decadas (La Rusia, Colombia). A lo largo del gradiente altitudinal entre los 3000 y los 3800 m s.n.m., se muestrearon de forma aleatoria 50 parcelas de 10 × 10 m. En estas se midio la altitud y las variables ambientales relacionadas con la humedad, el contenido en nutrientes, la densidad aparente y la textura del suelo, la ocurrencia de perturbaciones humanas como el fuego, la tala, el cultivo de papa y el pastoreo, y la historia de uso humano. Tambien se registro el numero y la abundancia de especies vegetales, determinando el origen exotico o nativo de las mismas. Se diferenciaron cuatro grupos de parcelas en funcion de su composicion especifica. Estos mostraron diferencias significativas en altitud, condiciones del suelo, historia de uso humano, y especialmente, en riqueza de especies exoticas y cociente especies exoticas/nativas. Dichos grupos podian estar relacionados con los tipos de vegetacion asociados habitualmente al sub-paramo y al paramo en funcion de la dominancia relativa de lenosas y herbaceas en los mismos, sin embargo, no parecian estar distribuidos segun el esquema hipotetico de los cinturones vegetales, sino formando un mosaico de parches. Dicho mosaico estaba determinado no solo por la altitud, sino tambien por las condiciones del suelo y la historia de uso humano de las diferentes zonas del paramo. Nuestros resultados corroboran los de estudios recientes que sugieren que los tipos de vegetacion asociados al sub-paramo y al paramo normalmente no aparecen formando cinturones, sino mosaicos de parches en funcion de variables ambientales locales, y tambien los de aquellos que senalan a las perturbaciones humanas como el principal determinante de las discontinuidades composicionales en los ecosistemas de alta montana tropical.

Amide and lithium aryloxide gallates [Li(+){RGaPh(3)}(-)] (R = NMe(2), O-2,6-Me(2)C(6)H(3)) react with the μ(3)-alkylidyne oxoderivative ligand [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CH)] (1) to afford the gallium-lithium-titanium cubane complexes [{Ph(3)Ga(μ-R)Li}{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CH)] [R = NMe(2) (3), O-2,6-Me(2)C(6)H(3) (4)]. The same complexes can be obtained by treatment of the [Ph(3)Ga(μ(3)-O)(3){Ti(η(5)-C(5)Me(5))}(3)(μ(3)-CH)] (2) adduct with the corresponding lithium amide or aryloxide, respectively. Complex 3 evolves with formation of 5 as a solvent-separated ion pair constituted by the lithium dicubane cationic species [Li{(μ(3)-O)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-CH)}(2)](+) together with the anionic [(GaPh(3))(2)(μ-NMe(2))](-) unit. On the other hand, the reaction of 1 with Li(p-MeC(6)H(4)) and GaPh(3) leads to the complex [Li{(μ(3)-O)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-CH)}(2)][GaLi(p-MeC(6)H(4))(2)Ph(3)] (6). X-ray diffraction studies were performed on 1, 2, 4, and 5, while trials to obtain crystals of 6 led to characterization of [Li{(μ(3)-O)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-CH)}(2)][PhLi(μ-C(6)H(5))(2)Ga(p-MeC(6)H(4))Ph] 6a.

The pseudo-octahedral dichlorido imido hydridotris(3,5-dimethylpyrazolyl)borate niobium and tantalum compounds [MTp*Cl2(NtBu)] (M = Nb (1a), Ta (1b); Tp* = BH(3,5-Me2C3HN2)3) were prepared in better yields by treatment of equimolar quantities of MCl3(NtBu)py2 and KTp* in toluene at reflux. Reactions of 1a,b with a small excess of LiNMe2 (1:1.2 ratio) in toluene gave the corresponding chlorido dimethylamido derivatives [MTp*Cl(NMe2)(NtBu)] (M = Nb (2), Ta (3)). Mixed methyl dimethylamido [MTp*Me(NMe2)(NtBu)] (M = Nb (4), Ta (5)) complexes were synthesized in good yields by heating for several days a mixture of 2 or 3 and MgClMe, in a 1:1 molar ratio. However, the reactions of 1a,b with excess LiNMe2 led to bis(dimethylamido) complexes [MTp*(NMe2)2(NtBu)] (M = Nb (6), Ta (7)) as unitary species. 4 and 5 reacted with B(C6F5)3 to give the cation-like complexes [MTp*(NMe2)(NtBu)]+[BMe(C6F5)3]− (M = Nb (8), Ta (9)), whereas in the case of complexes 6 and 7 the reaction led to [MTp*(NMe2){N(Me)═CH2-κ1N}(NtBu)]+[...

A series of heterometallic metallamacrocycles have been constructed from self-assembly reactions between the fluorinated Au(I) organometallic compounds [(AuC6F4py)2(μ2-diphosphane)] [diphosphane = bis(diphenylphosphanyl)methane (dppm) (1), 1,2-bis(diphenylphosphanyl)ethane (dppe) (2), trans-1,2-bis(diphenylphosphanyl)ethylene (dppet) (3), 1,3-bis(diphenylphosphanyl)propane (dppp) (4), 1,4-bis(diphenylphosphanyl)butane (dppb) (5), and 4,4′-bis(diphenylphosphanyl)-1,1′-biphenyl (dppdph) (6)] and the cis-blocked complexes [M(P–P)(H2O)2](OTf)2 (M = Pd) (P–P = dppp, dppf) (a,c), (M = Pt) (P–P = dppp, dppf) (b,d). Changes of the backbone of the diphosphanes were seen to have an influence on the resulting species. While the self-assembly reactions involving [(AuC6F4py)2(μ2-dppm)] (1), [(AuC6F4py)2(μ2-dppb)] (5), and [(AuC6F4py)2(μ2-dppdph)] (6) donors gave exclusively [2 + 2] heterometallomacrocycles, the assemblies arising from [(AuC6F4py)2(μ2-dppe)] (2) as well as the combinations between [(AuC6F4py)2(μ2-dppp)...

With the correct choice of the solvothermal conditions, we have achieved the unprecedented in situ formation of the free radical form of the anthraquinone-1,5-disulfonate molecule, and its favorable organization. The semiquinone radicals are coordinated to rare-earth cations to produce a 2D framework with a very high charge mobility and electric conductivity through the π-π-interactions. The existence of AQDS 3- anion radicals is proven on the base of: i) the electrical neutrality: elemental analyses for the different lanthanide RPF-8 bulks, the maximum residual electron densities in the structure, rule out the existence of any other neutralizing ion, ii) the geometrical modifications in the antraquinone molecules, and iii) although less definitive, due to the low magnetic moment μ = 0.39 μ B, the exhibited paramagnetism for the La (3+) with no unpaired electrons. © 2012 The Royal Society of Chemistry., This work has been supported by Spanish MCYT Projects Mat 2007-60822, 2010-17571, and 2008-06542-C04, the Project Consolider-Ingenio CSD2006-2001, and the Project of Comunidad Autónoma de Madrid (S2009/MAT-1756).

The compound [Ru(CN(t)Bu)4(Cl)2], 1, reacts with I2, yielding the halogen-bonded (XB) 1D species {[Ru(CN(t)Bu)4(I)2]·I2}n, (2·I2)n, whose building block contains I(-) ligands in place of Cl(-) ligands, even though no suitable redox agent is present in solution. Some isolated solid-state intermediates, such as {[Ru(CN(t)Bu)4(Cl)2]·2I2}n, (1·2I2)n, and {[Ru(CN(t)Bu)4(Cl)(I)]·3I2}n, (3·3I2)n, indicate the stepwise substitution of the two trans-halide ligands in 1, showing that end-on-coordinated trihalides play a key role in the process. In particular, the formation of ClI2(-) triggers electron transfer, possibly followed by an inverted coordination of the triatomic species through the external iodine atom. This allows I-Cl separation, as corroborated by Raman spectra. The process through XB intermediates corresponds to reduction of one iodine atom combined with the oxidation of one coordinated chloride ligand to give the corresponding zerovalent atom of I-Cl. This redox process, explored by density functional theory calculations (B97D/6-31+G(d,p)/SDD (for I and Ru atoms)), is apparently counterintuitive with respect to the known behavior of the corresponding free halogen systems, which favor iodide oxidation by Cl2. On the other hand, similar energy barriers are found for the metal-assisted process and require a supply of energy to be passed. In this respect, the control of the temperature is fundamental in combination with the favorable crystallizations of the various solid-state products. As an important conclusion, trihalogens, as XB adducts, are not static in nature but are able to undergo dynamic inner electron transfers consistently with implicit redox chemistry.

New neutral and anionic fluoroaryl gold(I) complexes featuring terminal pyridine rings were prepared following different strategies. The homoleptic anionic compounds NBu4[Au(C5F4N)2] (1) and NBu4[Au(C6F4py)2] (2) were obtained by reacting [AuCl(tht)] (tht = tetrahydrothiophene) with the organolithium derivatives of BrC5F4N and BrC6F4py, respectively. This route required the previous synthesis of the new fluorinated compound BrC6F4py, which was produced by a Stille cross-coupling between (4-pyridyl)trimethylstannane and 1,4-dibromotetrafluorobenzene. The neutral phosphane compounds [Au(C6F4N)(PPh3)] (3) and [Au(C6F4py)(PPh3)] (4) were obtained by treatment of [AuCl(PPh3)] with the organolithium reagents LiC6F4N and LiC6F4py, respectively. However, this synthetic strategy failed for organogold compounds containing a polyphosphane ligand. Consequently, an alternative synthetic procedure, based on displacement reactions of the weakly coordinated tht ligand from [Au(C6F4py)(tht)] by the appropriate polyphospha...

Two cases of anomalous phase transitions in Ce intermetallics are presented. In CeIn2 multiple signatures of a first order paramagnetic-ferromagnetic transition at 22 K have been experimentally detected. We discuss possible mechanisms for such behaviour and the new studies in the La1-xCexIn2 series. In the he case of CeNi1-xCux the low temperature ferromagnetic long range order appears owing to a magnetic cluster percolation process, from a cluster glass state established above the ferromagnetic state.

Herein, we describe the synthesis and characterization of a sulfonate-containing N-donor ligand in its sodium salt and acid forms, Na2[(DES)MeN(CH2)2NMe(DES)]·2H2O (1) and [(DES)MeN+H(CH2)2N+HMe(DES)]·H2O (2), and its corresponding metal complexes, [{(DES)MeN(CH2)2NMe(DES)}M(H2O)2]·nH2O [M = Ni (3), Co (4), Cu (5) and Zn (6)]. Treatment of HIV-infected MT-2 cells with Ni, Co and Cu complexes inhibit virus replication up to 50–70 % both in pre- and post-infected cells as a result of dual preventive and therapeutic behaviour.

We have investigated the crystallographic, magnetic and thermodynamic properties of the as-cast and annealed Ce 2 NiSi 3 alloys, crystallizing in the AlB 2 -type hexagonal structure. The DC-magnetic susceptibility data show that the as-cast sample exhibits an antiferromagnetic (AFM) ordering below T N = 3.8 K, whereas the annealed sample shows, at 4.2 K, a magnetic transition of AFM nature and, around 2.5 K, an additional anomaly. The specific heat shows a peak with c max = 7.4 J / mol K at 3.8 K for the as cast sample, which shifts to lower temperatures when the magnetic field increases, consistent with the antiferromagnetic nature of the transition. On the other hand, in the annealed alloy, the maximum of the specific heat peak reaches 9.3 J / mol K at 4.2 K, and no additional anomalies were observed. The different magnetic behavior between the as-cast and annealed samples is attributed to thermal effects on the structural disorder of nickel and silicon atoms, as already observed in other isotypic R 2 TSi 3 alloys, where R=U or Ce, and T= transition metal.

We report measurements on the thermal and electronic transport properties for the YbNiAl2 compound. At low temperatures, the electrical resistivity exhibits a logarithmic increase below a local minimum at 23 K, followed by a sharp decrease into the coherent/magnetically ordered state below 4.8 K. From the magnetic contribution to the specific heat ( c m a g ), a Kondo temperature T K = 5 K and an entropy value of 0.8Rln2 at the transition are estimated. The extrapolation of c m a g / T vs T plot to lower temperatures gives an estimate of the electronic coefficient γ 0 = 300 mJ/mol K2, which classifies this compound as a moderate heavy-fermion system. The magnetoresistance shows a single impurity Kondo scaling, with a single-ion characteristic temperature T ∗ = − 1.2 K. This negative sign implies the presence of strong ferromagnetic correlations, as suggested from the previously reported magnetization data. The results indicate that the YbNiAl2 alloy is an antiferromagnetic Kondo lattice system with a similar energy scales of the Kondo and RKKY interactions.

A series of carbosilane dendritic ligands of general formula Gn-[CH(3,5-Me 2 pz) 2 ] m and their corresponding palladium(II) complexes Gn-[CH(3,5-Me 2 pz) 2 Pd(X)Cl] m (X = Cl or Me) containing four (m = 1) or eight (m = 2) terminal bis(pyrazolyl)methane moieties, along with their corresponding mono-metallic counterparts (m = 0), have been synthesized. An appropriate choice of poly(pyrazolyl)methane ligand has allowed us to overcome the steric and solubility issues that previously limited the synthesis of polymetallic dendrimers containing (scorpionato)palladium complexes. The evaluation of these complexes as catalyst precursors in the Heck reaction between p-iodotoluene and methyl acrylate is also reported.

Neutral and cationic {bis(3,5-dimethylpyrazol-1-yl)methane}-palladium(II) complexes of general formula [PdClX{RCH(3,5-Me 2 pz) 2 }] (X=ClorMe) or [PdMe(MeCN){RCH(3,5-Me 2 pz) 2 }]-[BAr f 4 ], where R is a benzyl or benzyloxycarbonyl group or a poly(aryl ether) Frechet-type dendron, have been synthesized and fully characterized, including by X-ray diffraction methods in some cases. These palladium complexes have been evaluated as catalyst precursors in the Heck reaction between para-iodotoluene and methyl acrylate. The active catalytic species formed from these precursors are apparently not coordinated to the bis(pyrazolyl)methane ligands.

Anewhalf-sandwichimidocompound, [Nb{η 5 -C 5 H 3 (SiMe 3 }-C1 2 (NtBu)] (1), was isolated by treatment of [Nb{η 5 -C 5 H 3 (SiMe 3 ) 2 }Cl 4 ] with 1 equiv. LiNHtBu in hexane. Alkylimido derivatives [Nb{η 5 -C 5 H 3 (SiMe 3 ) 2 }RR'(NtBu)] (R = Cl, R' = Me 2; R = R' = Me 3, CH 2 SiMe 3 4) can be prepared by reaction of 1 with the appropriate alkylating reagent. Silsesquioxane ligand [Si 8 O 12 Cl(iBu) 7 ] (5a) can be obtained by treatment of [Si 7 O 9 (OH) 3 (iBu) 7 ] with 1 equiv. silicon tetrachloride in the presence of triethylamine. Ligand 5a reacts with NH 3 (g) at low temperatures to yield an amido derivative, [Si8O 12 (NH 2 )(iBu) 7 ] (5b), whereas the reaction of the trisilanol with excess BuLi leads to the corresponding lithium salt [Li 3 Si 7 O 12 (iBu) 7 ] (5c). A dichlorido(silsesquioxanylimido)-niobium compound [Nb{η 5 -C 5 H 3 (SiXMe 2 )(SiMe 3 )}Cl 2 -{NSi 8 O 12 (iBu) 7 }] (X = Cl 6a, Me 6b) can be prepared by reaction of 1 equiv. tetrachloridoniobium complex [Nb{η 5 -C 5 H 3 (SiXMe 2 )(SiMe 3 ))Cl 4 ] (X = Cl, Me) and amidosilses-quioxane 5b. From 6b, three new alkyl derivatives, [Nb{η 5 -C 5 H 3 (SiMe 3 ) 2 }XY(NSi 8 O 12 R 7 )] (R = iBu, X = Cl, Y = Me 7; X = Y = Me 8, CH 2 SiMe 3 9), were isolated by usual alkylation reactions. Alternatively, protonolysis reaction of trisilanol [Si 7 O 9 R 7 (OH) 3 ] with [Nb{η 5 -C 5 H 3 (SiXMe 2 )(SiMe 3 ))Cl 4 ] (X = Cl) in the presence of triethylamine produces a dichlorido derivative, [Nb{η 5 -C 5 H 3 (SiMe 3 )(Me 2 SiOSi 7 O 11 R 7 - K 2 O,O)}-Cl 2 ] (R = iBu 10), which can be transformed into an imido complex, [Nb{η 5 -C 5 H 3 (SiMe 3 )(Me 2 SiOSi 7 O 11 R 7 -κ 2 O,O)}-(NtBu)] (R = iBu 11), by reaction with LiNHtBu, whereas for X = Me, a chlorido complex, [Nb{η 5 -C 5 H 3 (SiMe 3 ) 2 }Cl(Si 7 O 12 R 7 - K 3 O,O,O)1] (R = iBu 12), can be isolated. Alkylation of 10 and 12 leads to dimethyl, trimethylsilylmethylidene and methyl derivatives 13, 14 and 15, respectively. Alkylimidoniobium complexes 2-4 react with carbon monoxide or xylyl isocyanide at room temperature to give acylimidoniobium [Nb{η 5 -C 5 H 3 (SiMe 3 ) 2 )R(NtBu)[C(R')O- K 2 C,O}] (R = Cl, R' = Me 16; R = R' = Me 17, CH 2 SiMe 3 18) and iminoacylimidoniobium [Nb(η 5 -C 5 H 3 (SiMe 3 ) 2 }R(NtBu){C(Me)NAr-κ 2 C,N}] (Ar = 2,6-Me 2 C 6 H 3 ; R = Cl 21, Me 22) compounds by simple insertion reactions. However, compound 13 reacts with CO and 2,6-Me 2 C 6 H 3 NC, leading to enediolato [Nb{η 5 -C 5 H 3 (SiMe 3 )-(Me 2 SiOSi 7 O 11 R 7 -K 2 O,O)}{O(Me)C=C(Me)O-κ 2 O,O}] (R = iBu 19) and azaniobacyclopropane [Nb(η 5 -C 5 H 3 (SiMe 3 )-(Me 2 SiOSi 7 O 11 R 7 -κ 2 O,O)}(CMe 2 NAr-κ 2 C,N)] (R = iBu, Ar = 2,6-Me 2 C 6 H 3 20) derivatives through intermolecular coupling between two acyl groups and by a double methyl migration processes, respectively. All new compounds have been characterized by IR spectrophotometry, 1 H, 13 C{ 1 H} and 29 Si( 1 H} NMR spectroscopy and elemental analysis.

We report measurements on the thermal and magnetic properties in the temperature range 2–300 K for the YbNiAl 2 compound which crystallizes in the orthorhombic MgCuAl 2 -type structure (space group Cmcm). At zero magnetic field, AC-magnetic susceptibility data show a peak in the real component consistent with an antiferromagnetic order below T N = 4.8 K . A field-induced ferromagnetic order is observed from the zero field cooled and field cooled curves of DC-magnetic susceptibility at different magnetic fields with a transition to a ferromagnetic state between 9 and 10 kOe. It is further confirmed by the isothermal magnetization curves as a function of the magnetic field at several temperatures, showing two metamagnetic transitions at H 1 = 8 kOe and H 2 = 9.3 kOe . The results are compared to those reported for other Yb–Ni–Al compounds.

The proline-catalyzed aldol reaction of racemic 2-(2′-pyrimidyl)ferrocenecarbaldehyde with acetone in DMSO at room temperature constitutes as the first example of an organocatalytic kinetic resolution of a planar-chiral compound. The selectivity factor of the kinetic resolution is 9.2, and the stereochemical outcome of the process can be easily rationalized by the standard mechanistic model of the proline-catalyzed aldol reaction.

In this study we examined the size-structures and allometric relationships between height and diameter over 2 y in populations of the pioneer tree Trema micrantha on a large landslide (Casita Volcano, Nicaragua). The landslide comprised three different zones (erosional, depositional and transitional) based on fertility and geomorphological stability. We attempted to analyse the development of canopy hierarchies and intraspecific competition, and the existence of different growth strategies, within the T. micrantha populations of the different landslide zones. Vegetation was surveyed in 2810 × 10-m plots in which a total number of 307 T. micrantha individuals were recorded and tagged. In the depositional zones, size-hierarchies and one-sided competition for light were apparent and, among the short stems (0.0–2.5 m) of the understorey, plastic responses to shade consisting in a marked increase in height in relation to diameter were evident. In the erosional zones, size-hierarchies were not apparent. All stems were small and, among them, the shortest ones (0.0–1.0 m) were dead whereas the tallest (>1.5 m) grew slowly, increasing their diameter to a greater extent than their height. Our study shows that T. micrantha individuals developed different growth strategies in the different areas of the landslide and suggests that this species allocates resources to growth and survival differently depending on environmental conditions. Trema micrantha is a highly versatile species capable of dealing not only with extremely infertile substrates and conditions of high light availability, but also with partially shaded environments such as those in secondary forests.

This study examined the main changes in the herbaceous communities during the first four years of succession in a large landslide on Casita Volcano, Nicaragua, located in a densely populated area that has a tropical dry climate. Our main objective was to determine the major pathways of change in community features, such as richness, biovolume, species composition, and abundances of plant traits and to verify if they varied between the different landslide areas based on abiotic heterogeneity and landscape context. Number, percent cover, mean height and traits of herbaceous species, and several abiotic factors related to fertility and geomorphological stability of substrates were sampled in 28 permanent plots. Environmental heterogeneity strongly influenced early successional changes in the herbaceous communities during the four years of the study. Biovolume increased in the unstable and infertile areas and decreased in the stable and fertile landslide areas. In most zones, species richness decreased significantly because of the expansion of a few dominant species that developed a large cover and excluded other species. Those dominant species were mainly responsible for changes in species composition and included annual forbs, e.g., Calopogonium mucunoides and Stizolobium pruriens, graminoids that have rhizomes or stolons, e.g., Hyparrhenia rufa, and perennial nitrogen-fixing forbs, e.g., Clitoria ternatea. They might be important in determining future successional patterns on the Casita Volcano landslide.

Private urban greenspaces, called ‘patios’ in Latin America, can act as important refuges for wildlife in scattered growing cities of the tropics. We studied the presence and abundance of the black spiny-tailed iguana (Ctenosaura similis) in patios of Leon city (Nicaragua). Forty patios were structurally characterized and abundances of iguanas were determined through surveys of inhabitants supported by observations of specimens and burrows. Patio area and maximum tree height were variables positively related with presence and abundance of iguanas and presence of burrows. The permeability of fences for iguana movements and the presence of preferred trees for food were also related to presence and abundance of iguanas. Stepwise selection model for abundance of iguanas included number of preferred trees, maximum tree height and permeability of fences. The presence of iguanas was only explained by maximum tree height. Our results show that the indigenous-root types of patios offer the most adequate conditions for the establishment and maintenance of iguana populations among the studied cases. In the light of these results, management practices to preserve the Ctenosaura similis populations in urban patios are suggested.

2-(N-aryliminomethyl)pyrrole precursors (2,6-R2-C6H3-N CH-2-C4H3NH) (R = Me, IH; R = iPr, IIH) were prepared and transformed into their corresponding sodium salts (Na+I− and Na+II−) by treatment with NaH. Both salts readily react with [NiBr2(DME)] (DME = 1,2-dimethoxyethane) to give the respective bis{2-(N-arylimino-κN-methyl)pyrrolide-κN}nickel(II) complexes (1, 2) in almost quantitative yields. The oxidative addition of IH to [Ni(COD)2] (COD = 1,5-cyclooctadiene) results in the formation of 3, which is a mono(iminomethylpyrrolide)-η3-(cyclic-allyl)-type organonickel(II) complex. The crystal structure of compound 1 has been established by X-ray diffraction studies.

Early succession on large landslides in highly humanized areas that have a tropical dry climate is not well studied. This study documented vegetation recovery during the first 4 years after disturbance at a landslide on Casita Volcano, Nicaragua. We aimed to determine the main pathways and causes of change in community features, such as richness, biovolume, and species composition and verify the role played by environmental heterogeneity. Data consisting on number, covers and mean height of woody species and several abiotic factors related to fertility and stability of substrates were obtained from permanent plots in previously defined zones. Pathways of early succession were highly contingent on abiotic heterogeneity and landscape context and were mainly controlled by abiotic factors associated with fertility of substrates, and incidence of human disturbances. Those results might form the basis of a model of early succession on landslides located in densely populated areas within tropical dry ecosystems. Our results suggest that, rather than focusing research on large-scale disturbances, the study of succession in landslides of the type that occurred on Casita Volcano must point towards the response of ecosystems to a much more complex disturbance regime, in which human-induced disturbances play a major role.

Addition of diisopropylzinc, diethylzinc, and isopropylmagnesium chloride to readily available 2-(2′-pyrimidyl)ferrocenecarbaldehyde takes place with high diastereoselectivity to afford exclusively the α-ferrocenyl alcohol of ( R ∗ ,p R ∗ ) configuration. On the other hand, the addition of ethyl- and methylmagnesium bromide leads to diastereomeric mixtures in which the major isomer has the ( S ∗ ,p R ∗ ) configuration. A unified mechanistic model accounting for this stereochemical outcome is proposed.

A conceptual and analytical framework to assess ecological integrity at a landscape level. A concep tual and methodological approach for the ecological integrity analysis at landscape level is presented. The aim is providing a tool for land planning and nature conservation. With this purpose the meaning of integrity and related concepts are discussed, and a model to evaluate landscape integrity by a comprehensive scheme is proposed. The first index is based in metrics of landscape ecology theory (connectivity, cover of both conservation areas and human managed land, etc.) to evaluate the different ecosystem fragments pattern. The second one, an ecosystems integrity index, is focused to evaluate remnants with a structure close to maturity and evaluates the mathematical distance to a reference hypothetical composition. Finally, the agricultural area is evaluated by a coherence index, with emphasis in ecological processes but also including the natural structures with conservation functions. These indexes are combined in a model that facilitates the joint consideration of their values and the comparison with theoretical scenarios. The model allows us to develop a concurrent management of relevant variables that usually are associated to different environmental qualities. Because of its characteristics and the intermediate scale of application, the model constitutes an important tool for matching ecosystem integrity and land planning. Both are actions and concept and relevant for nature conservation and landscape management, but in general independently considered., El trabajo constituye una aproximación conceptual y metodológica para el análisis de la integridad ecológica, como instrumento aplicable a la planificación del territorio y la conservación de la naturaleza a escala de paisaje. Con dicho fin se discuten las acepciones de integridad y conceptos próximos y se presenta un modelo de evaluación que considera la integridad del paisaje como resultado de la interacción de tres índices. El primero (integridad espacial) utiliza métricas de la ecología del paisaje (conectividad y cobertura de áreas naturales y áreas de uso humano) y evalúa la distribución de los fragmentos de los distintos tipos de ecosistemas existentes en el territorio. El segundo, un índice de integridad ecosistémica, se centra en los fragmentos con estructura más próxima a la madurez y valora su distancia numérica a ecosistemas de referencia. Por último, en el área sometida a usos agrícolas, se aplica un índice de coherencia ecológica de los usos del suelo que tiene en los elementos naturales con funciones de conservación. Estos índices son articulados mediante un modelo que facilita una visión simultánea de sus valores, así como su comparación con escenarios teóricos. El modelo permite manejar de forma simultánea variables relevantes que comúnmente se presentan como asociadas a aspectos diferentes de la calidad del entorno. Por sus características y escala intermedia de aplicación puede constituir una herramienta importante para enlazar conceptos y actuaciones, relevantes para la conservación de la naturaleza, pero que suelen manejarse por separado, en concreto la integridad ecosistémica y con la planificación del territorio.

We described the plant communities on a large landslide in a human-dominated area of tropical dry forest landscape (Casita Volcano, Nicaragua) and in the adjacent forest, 3 yr after landslide occurrence. At both sites, we determined the relationships between spatial changes in environmental factors and the spatial distribution of species and plant traits. Subsequently, we tested the hypothesis that the compositional similarity between the landslide and the forest increased with a decrease in the distance from the forest edge and the width of the landslide. In the forest, the spatial distribution of species and plant traits was determined mainly by an elevational gradient that was associated with the amount of bare soil, whereas, on the landslide, there was no such gradient but species distributions were influenced mostly by the presence of residual agricultural and forest soils and human disturbance. We did not find an increase in compositional similarity between the landslide and the forest at the edge or in the narrow zones of the landslide. Compared to other landslides, the recovery process was strongly influenced by the extreme abiotic heterogeneity, climate seasonality, and human use in the area. The study of succession in tropical dry landslides located in densely populated zones should focus on understanding the response of regional ecosystems to a complex disturbance regime in which human-induced disturbances play a major role.

The reaction of [Pt(μ-Cl)(κ,η 2 -COE-MeO)] 2 ( 2 ) (COE-MeO = 2-methoxy-5-cycloocten-1-yl) with trispyrrolylphosphine yields [PtCl{P(pyrl) 3 }(κ,η 2 -COE-MeO)] ( 3 ), in contrast to the crown-cycle complex [Pd(μ-Cl) {P(pyrl) 3 }] 8 ( 1 ) obtained with the analogous palladium complex. The different reactivity has been explained in terms of the higher lability of the carbon–carbon double bond in the starting palladium compound, as compared with the related platinum derivative. The reaction of 1 with the ligand 2-[(pyridin-2-ylmethylene)aminophenol], (HNN′O), in the presence of thalium salt and NEt 3 , yields the complex [Pd(κ 3 N , N ′, O -py-CH N-C 6 H 4 O)(P(O)(pyrl) 2 )] ( 5 ), which contains, for the first time, a di( N -pyrrolyl)phosphonato- P ligand. Treatment of [PdCl(κ 3 N , N ′, O -py-CH N-C 6 H 4 O)] with P(pyrl) 3 gives the amido derivative [PdCl{κ 3 P , N , N -(P(pyrl) 2 -O-C 6 H 4 -N-CH(CH 2 -CO-CH 3 )-py)}] ( 7 ), which displays a N–Pd–P–O–C 2 six-membered metallacycle. In addition, the latter compound has been able to insert an acetone molecule into its framework. The crystal structures of 5 and 7 were solved by X-ray diffraction analysis.

Trichloro methyl [Nb{η 5 -C 5 H 3 (SiXMe 2 )(SiMe 3 )}Cl 3 Me] (X = Cl, 2 ; Me, 3 ), dichloro dimethyl [Nb{η 5 -C 5 H 3 (SiXMe 2 )(SiMe 3 )}Cl 2 Me 2 ] (X = Cl, 4 ; Me, 5 ) and tetramethyl [Nb{η 5 -C 5 H 3 (SiXMe 2 )(SiMe 3 )}Me 4 ] (X = Me, 6 ; Cl, 7 ) niobium complexes were synthesized by treatment of starting tetrachloro derivatives [Nb{η 5 -C 5 H 3 (SiXMe 2 )(SiMe 3 )}Cl 4 ] (X = Cl, 1a ; Me, 1b ) with dimethyl zinc or chloro methyl magnesium in different proportions and conditions. A mixture of trichloro methyl and dichloro dimethyl tantalum complexes [Ta{η 5 -C 5 H 3 (SiClMe 2 )(SiMe 3 )}Cl 4− x Me x ] ( x = 1, 8 ; 2, 9 ) in a 2:1 molar ratio was obtained in the reaction of [Ta{η 5 -C 5 H 3 (SiClMe 2 )(SiMe 3 )}Cl 4 ] ( 1c ) with 0.5 equivalents of ZnMe 2 in toluene at low temperature. 8 could be isolated as single compound when 1 equivalent of 1c was added to the mixtures of 8 and 9 , while the reaction of 1c with 1.5 equivalents of dimethyl zinc gave 9 as unitary product. However, [Ta{η 5 -C 5 H 3 (SiMe 3 ) 2 }Cl 4 ] ( 1d ) reacts with 0.5 equivalents of alkylating reagent giving the trichloro methyl compound [Ta{η 5 -C 5 H 3 (SiMe 3 ) 2 }Cl 3 Me] ( 10 ) in good yield. On the other hand, [Ta{η 5 -C 5 H 3 (SiMe 3 ) 2 }Cl 4 ] ( 1d ) reacts with 2 equivalents of MgClMe in hexane at room temperature giving a mixture of dichloro dimethyl and chloro trimethyl complexes[Ta{η 5 -C 5 H 3 (SiMe 3 ) 2 }Cl 4− x Me x ] ( x = 2, 11 ; 3, 12 ), while the use of 4 equivalents of MgClMe converts 1c into the tetramethyl derivative [Ta{η 5 -C 5 H 3 (SiClMe 2 )(SiMe 3 )}Me 4 ] ( 13 ). Finally, a tetramethyl tantalum complex [Ta{η 5 -C 5 H 3 (SiMe 3 ) 2 }Me 4 ] ( 14 ) was prepared by reaction of [Ta{η 5 -C 5 H 3 (SiXMe 2 )(SiMe 3 )}Cl 4 ] (X = Cl, 1c ; Me, 1d ) with 5 (X = Cl) or 4 (X = Me) equivalents of MgClMe in diethyl ether (X = Cl) or hexane (X = Me), respectively, as solvent. All the complexes were studied by IR and NMR spectroscopy and the molecular structure of the complex 11 was determined by X-ray diffraction methods.

European agriculture is increasingly involved in nature conservation. Careful assessment of the ecosystems created by agriculture is essential for the evaluation of the sustainability of the interaction between agriculture and these systems. We consider two main requirements for agricultural sustainability: (a) ecological integrity: the maintenance of ecosystem functionality and (b) ecological coherence: the appropriate connection between the production system and the underlying ecosystem. This viewpoint emphasizes the sustaining capacity of the ecosystem as the basis of agricultural production, independent of its conventional economic value (profitability). The application of these ideas implies the investigation of relationships between both the different functions of agriculture and the dimensions relevant for the evaluation of the sustainability of agriculture. We apply a multidimensional evaluation model to some characteristic Spanish agricultural landscapes and compare the results with contrasting reference scenarios. The value of each dimension of sustainability is assessed using a semi-quantitative procedure. Results show that strongly contrasting agricultural systems can be categorized into well-defined groups on the basis of the sustainability dimensions. These groups play an increasingly divergent role in nature conservation. This analysis contributes to the discussion of consequences of European policies on the conservation of agricultural landscapes.

In view of the wide applicability and versatility of titanium based Lewis acids in selective organic synthesis including asymmetric synthesis, we have synthesized a family of mono and polyatomic titanium derivatives. The polymetallic complexes prepared are bridged by pyridimine, quinone and triazine based ligands. The synthesis of [{Ti(O–i-Pr)3(Oddbf)}2] (1), [Ti(O–i-Pr)2(Oddbf)2] (2), [{Ti(O–i-Pr)2(Oddbf)(OMent)}2] (3) (ddbfO = 2,3-dihydro-2,2-dimethyl-benzofuranoxo; MentO = (1R,2S,5R)-(−)-menthoxo), [{Ti(O–i-Pr)3(OMenpy)}2] (4), [Ti(O–i-Pr)2(OMenpy)2] (5) (MenpyO = (1S,2S,5R)-(−)-menthoxo-pyridine); [{(Ti(OR)3)2L}n] (RO = isopropoxo, (1R,2S,5R)-(−)-menthoxo) (6–11) and [{(Ti(O–i-Pr)3)3L}n] (12) was accomplished from a Lewis acid such as Ti(O–i-Pr)4, [{Ti(O–i-Pr)3(OMent)}2] or [Ti(OMent)4] and chelating ligands (ddbfOH = 2,3-dihydro-2,2-dimethyl-benzofuranol; MenpyOH = (1R,2S,5R)-(−)-5-methyl-2-isopropyl-1-(2′-pyridinyl)cyclohexan-1-ol; LH2 = 4,6-dihydroxy-2,5-diphenyl-pyrimidine, 2,4-dihydroxy-5,6-dimethyl-pyrimidine, 5,8-dihydroxy-1,4-napthoquinone, 2,5-dihydroxy-1,4-benzoquinone and LH3 = cyanuric acid) that provide a rigid framework for the metal centre. The molecular structure of 5 has been determined by single crystal X-ray diffraction studies.

The reaction of lithiated picolines and [TiCl3(η(5)-C5Me5)] leads to several bridging or terminal imido compounds, each of which can be selectively formed by controlling the stoichiometry and temperature. Specifically, the dinuclear imido-bridged [TiCl(η(5)-C5Me5)(μ-NR)]2 (1a, NR = 2-imido-3-picoline; 1b, NR = 2-imido-5-picoline) species and the unusual Ti-Li imido-amido heterobimetallic complex [{Li(THF)}{Ti(η(5)-C5Me5)(NR)(NHR)2}] (2a, NR = 2-imido-3-picoline; 2b, NR = 2-imido-5-picoline) were isolated. Compounds 2 are in effect the first structurally characterized examples of titanium(IV) coordinated to terminal imido-pyridines. DFT-D calculations for 2a denote a multiple bond character between titanium and the imido ligand and a strong polarization of the electron density by the alkali cation in spite of the lack of intermetallic bonding.

The [bis(silyl)cyclopentadienido]tetrachloroniobium and -tantalum complexes [MCp^Cl 4 ] [Cp^ = η 5 -C 5 H 3 (SiClMe 2 )-(SiMe 3 ); M = Nb 3, Ta 4] were synthesized by reaction of the pentachlorides MCl 5 with C 5 H 3 (SiClMe 2 )(SiMe3)2 (1). Although the Lewis acidity of tetrachloro complexes 3 and 4 is lower than that of the pentahalides, two adducts [M{η 5 -C5H3(SiClMe2)(SiMe 3 )}Cl 4 (CNAr)] (Ar = 2,6-Me 2 C 6 H 3 ; M = Nb 5, Ta 6) have been isolated by reaction with ArNC. Complexes 3 and 4 react with tert-butylamine or lithium amides to afford the dichloroimido and amidochloroimido complexes [M{η 5 -C 5 H 3 (SiClMe 2 )(SiMe 3 )}Cl 2 (NR)] (R = tBu, M = Nb 7, Ta 8; R = Me, M = Nb 9) and [Ta{η 5 -C 5 H 3 (SiClMe 2 )(SiMe 3 )}-Cl(NHtBu)(NtBu)] (10), respectively. In addition, 7 and 8 can be prepared by treatment of the pentachlorides with [C 5 H 3 (SiMe 2 NHtBu)(SiMe 3 ) 2 ] (2) by elimination of 1. The tetrachloro compound 3 reacts with four equivalents of tBuNH 2 to give the constrained-geometry derivative [Nb{η 5 -C 5 H 3 (Si-Me 2 NtBu-KN)(SiMe 3 )}Cl(NtBu)] (11), whereas the treatment of toluene solutions of 3 and 4 with H 2 NCH 2 CH 2 NH 2 in the presence of triethylamine leads to the trichloro complexes [M{η 5 -C 5 H 3 (SiMe 2 NCH 2 CH 2 NH 2 -κ 2 N,N)(SiMe3)}Cl 3 ] (M = Nb 12, Ta 13). All the reported complexes were studied by IR and NMR spectroscopy and the molecular structures of complexes 3 and 5 were determined by X-ray diffraction methods.

Alkylation of [TaCp*Cl 4 ] (Cp' = η 5 -C 5 Me 5 ) with 3 equiv. of MgCl(CH 2 SiMe 3 ) gives the chloridotris(trimethylsilylmethyl) complex [TaCp*Cl(CH 2 SiMe 3 ) 3 ] (1). TaCp*Cl 2 Me 2 reacts with 2 equiv. of LiR (R = CH 2 Ph, CH 2 SiMe 3 ) to give the mixed alkyl derivatives [TaCp*Me 2 R 2 ] (R = CH 2 Ph, 2; CH 2 SiMe 3 , 3). The dimethyldineopentyl complex [TaCp*Me 2 (CH 2 -CMe 3 ) 2 ] (4) was obtained by reaction of TaCp*Cl 2 -(CH 2 CMe 3 ) 2 with 2 equiv. of LiMe. The treatment of a toluene solution of TaCp*Cl 2 Me 2 with 2 equiv. of neophyllithium in a standard vacuum line gave a mixture of three compounds, [(TaCp*Me 2 (CH 2 CMe 2 Ph)} 2 (μ-O)] (5), [TaCp*Me 2 -(CH2CMe2-o-C6H4-K2C,C)] (6) and [TaCp*Me(CH 2 CMe 2 Ph)-(CH 2 )] (7), which were identified by NMR spectroscopy. However, when the reaction was carried out under rigorously anhydrous conditions, only complexes 6 and 7 were isolated. A chlorido(trimethylsilylmethyl) (trimethylsilylmethylidene) complex [TaCp*Cl(CH 2 SiMe 3 )(CHSiMe 3 )] (8) was prepared by heating 1 at 60 °C, or by leaving it at room temperature for a long time. A 3:2 (9/10) mixture of [TaCp*MeR-(CHSiMe 3 )] (R = CH 2 SiMe 3 , 9; Me, 10) was obtained by thermal treatment of 3, which was accompanied by the evolution of CH 4 and SiMe 4 . However, irradiation of a [D 6 ]benzene solution of 3 with a sun lamp gave a mixture of 9 and [TaCp*(CH 2 SiMe 3 )R(CH 2 )] (R = Me, 11; CH 2 SiMe 3 , 12) in a 2:1:1 (9/11/12) ratio. When a [D 6 ]benzene solution of 4 was heated at 60 °C, a mixture of the (alkyl)(neopentylidene) derivatives [TaCp*MeR(CHCMe 3 )] (R = Me, 13; CH 2 CMe 3 , 14) in a 4:1 (13/14) ratio was detected by NMR spectroscopy, while irradiation with a sun lamp produced a mixture of alkylidene complexes [TaCp*(CH2CMe3)R(CH2)] (R = Me, 15; CH 2 CMe 3 , 16) in a 3:1 (15/16) ratio. On the other hand, the alkylation of TaCp*Cl 2 (CH 2 CMe 3 ) 2 with 2 equiv. of LiCH 2 SiMe 3 gave the (alkyl)(alkylidene) complex [TaCp*(CH 2 CMe 3 )(CH 2 SiMe 3 )(CHCMe 3 )] (17) with the elimination of SiMe 4 , whereas the treatment of TaCp*Cl 2 -(CH 2 SiMe 3 ) 2 with the appropriate reagent gave [TaCp*(CH 2 R)(CH 2 SiMe 3 )(CHR')] (R = R' = Ph, 18; R = CMe 2 Ph, R' = SiMe 3 , 19) with the elimination of SiMe 4 and CMe 3 Ph, respectively. All compounds were studied by IR and NMR spectroscopy, and the molecular structures of complexes 1, 4 and 5 were determined by X-ray diffraction methods.

A series of carbosilane dendritic compounds Gn-ONNMem, containing one (n = 0), four (n = 1), eight (n = 2), or 16 (n = 3) terminal pyridylimine ligands, substituted with m methyl groups (m = 0, 2, ...

A variety of bisalkoxo titanium dichloride THF adducts [Ti(OR)2Cl2(thf)2] {OR = adamantanoxo (9), (1R,2S,5R)-(−)-menthoxo (10), (1S-endo)-(−)-borneoxo (11)} have been prepared and characterized by spectroscopic techniques. The molecular structure of 11 has been determined by single-crystal X-ray diffraction studies. The parent Lewis acid bisalkoxo titanium dichloride derivatives and related alkoxo complexes [Ti(OR)2(OPri)2]2 have been tested as initiators in ring-opening polymerization of e-caprolactone and l -lactide.

The processes underlying the positive effect exerted by woody species on other plant species can be grouped into a physical effect due to the canopy itself (mainly amelioration of temperature and light extremes), and an edaphic effect (nutrient enrichment). Both groups of effects are present in the savanna-like systems originated by Retama sphaerocarpa in the Iberian Peninsula. The consequences of these shrubs for the spatial heterogeneity induced in the herbaceous community are not well known. The herbaceous community was sampled by means of radial transects around 20 adult shrubs, from the canopy centre to the open areas among the shrubs, both northwards and southwards. Floristic composition, diversity and pasture mean height change both along the inside–outside gradient, and from north to south. As a nutrient enriched environment, the centre of the understorey showed the lowest species richness and evenness, and the highest standing crop. In contrast, the environmentally stressful open areas showed the highest number of species and evenness, and the lowest standing crop. This general effect is only partially due to nutrient availability, and is not homogeneous around the shrub, as open area conditions penetrate into the understorey driving the herbaceous community towards that of open areas. An individual shrub effect is also suggested by our results. Different conditions are thus provided by R. sphaerocarpa understoreys, favouring different subsets of species from the general pool, and therefore defining shrub canopies as sources of spatial heterogeneity in the whole savanna-like system.

Muon spin relaxation measurements have been performed over the wide temperature range from 0.4 to 200 K in some representative CeNi 1 - x Cu x compositions ( 0.2 ⩽ x ⩽ 0.6 ) where a cluster-glass phase at temperatures above the ferromagnetic ground state has been characterized by AC–DC magnetization measurements. The analysis of these data reveals the presence of a highly inhomogeneous magnetic state at temperatures above the freezing temperature T f (seen by AC susceptibility) that runs into the paramagnetic regime. This inhomogeneous magnetic state consists of long-range ordered and non-ordered fractions, the latter increasing with temperature. An unusual strong dependence of the μ SR magnetic response on magnetic field history such as zero field cooling vs. field cooling within the intermediate magnetically inhomogeneous range is found. The present analysis considering also previous neutron scattering, magnetic characterization, specific heat allows us to present a complete description of the system. We propose that the long-range magnetic order at low temperature is achieved by a percolative process of magnetic clusters that become static below T f .

Chloro methyl and dimethyl azatantalacyclopentene complexes [TaCp*Cl2-xMex(CHCHCMe2NAr-κ2C,N)] (Cp* = η5-C5Me5; Ar = 2,6-Me2C6H3; x = 1, 2; 2, 3) can be prepared by reaction of [TaCp*Cl2(CHCHCMe2NAr-κ2C,N)] (1a) with dimethylzinc and chloromethylmagnesium, respectively. Reaction of 1a with dibenzylmagnesium leads to the monoalkylated complex [TaCp*Cl(CH2Ph)(CHCHCMe2NAr-κ2C,N)] (4). The alkylation of [TaCp*Cl2{C(Ph)CHCMe2NAr-κ2C,N}] (1b) with 2 equiv of chloromethylmagnesium at low temperature gave the dimethyl azatantalacyclopentene complex [TaCp*Me2{C(Ph)CHCMe2NAr-κ2C,N}] (5), which at room temperature decomposes, giving the dimethyl(imido) complex [TaCp*Me2(NAr)] (7), identified by NMR spectroscopy. Alkylation of 1b with 0.5 equiv of dibenzylmagnesium leads to the monobenzyl complex [TaCp*Cl(CH2Ph){C(Ph)CHCMe2NAr-κ2C,N}] (6); however treatment with 1 equiv of the alkylating reagent gave the dibenzyl(imido) [TaCp*(CH2Ph)2(NAr)] (8) in a mixture with 6 as minor component. Moreover, 1a reacts with 1 equiv ...

Rod-like organogold(I) complexes [AuR(CNC6H4O(O)CC6H4OC10H21-p)] were prepared and their liquid crystal behaviour was studied. Depending on the nature of R, the synthetic methodology was different. Thus, for R = substituted alkynyl ligands, the new compounds were prepared in two steps:(i) reaction of [AuCl(tht)] (tht = tetrahydrothiophene) with R′C CH(R′ = C5H4N, C6H4C N, C6H4C CC5H4N) in the presence of NaOAc to give insoluble [Au(C CR′)]n; (ii) reaction of the latter polymers with the isonitrile CNC6H4O(O)CC6H4OC10H21-p.For R = fluorinated aryls, the complexes were prepared by displacement of tht from the compounds [AuR(tht)] (R = C5F4N, C6F4C5H4N, C6F5) with isonitrile.In addition, an unexpected ionic derivative [Au(C CC5H4NC10H21)2][Au(C CC5H4N)2] was formed in the reaction between [PPh4][Au(C CC5H4N)2] and C10H21I. All these compounds have been characterized by IR and NMR spectroscopy and mass spectrometry. The X-ray crystal structure of the compound with R = C CC5H4N shows a linear molecule in which the gold atom is surrounded by the pyridine-containing acetylene and the isonitrile ligand, and no direct gold–gold interaction occurs. Six of the neutral compounds are liquid crystals and their optical, thermal and thermodynamic data were analyzed and compared in terms of molecular polarizability.

The crown ether phosphanes PAr*Ph2 (1) and PAr*2R [Ar* = 3,4-(18-crown-6)-phenyl; R = Me (2); R = Ph (3)], prepared from PCl2R and Ar*Li, have been studied. The syntheses and characterization of their oxides (4–6), and their BH3 (7–9), PdCl2 (10–12), and PtCl2 (13–15) complexes are reported. The molecular structure of the borane complex PAr*2Ph·BH3 (9) has been determined by X-ray structural analysis. Spectroscopic data suggest that phosphanes 1–3 have similar electronic properties and steric requirements to the corresponding phenylphosphane ligands PPh2Me and PPh3. Crown ether methylphosphane 2 and its complexes are remarkably water soluble, but 1 and 3 are only slightly soluble. Palladium(II) complexes 14 and 15 have been tested as catalysts in the Stille coupling of phenyltrichlorostannanes and aryl iodides in water. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

An amorphous GdNiAl sample was prepared by mechanical grinding performed on a crystallised intermetallic. The treatment changes greatly the ferromagnetic behaviour of this compound; its Curie temperature decreases from 57 K (unmilled sample) to 29 K (milled sample). Specific heat and magnetisation measurements reveal that amorphous GdNiAl exhibits an interesting magnetocaloric effect; for an applied magnetic field of 5 T a change of ≅8.9 J/kg K is observed at 36 K for the isothermal magnetic entropy.