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Copper plays many important roles in ethylene chemistry, thus generating significant interest in understanding the structures, bonding, and properties of copper(I)-ethylene complexes. In this work, the ethylene binding characteristics of a series of isolable Cu(I)-ethylene compounds supported by a systematic set of fluorinated and nonfluorinated bis- and tris(pyrazolyl)borate and the related bis(pyrazolyl)methane ligands have been investigated. Through a combination of X-ray absorption spectroscopy and quantum chemical calculations, we characterize their geometric and electronic structures and the role that fluorinated ligands play in lowering the electron density at Cu sites. Such ligands increase the ethylene-to-Cu σ-donor interaction and, correspondingly, decrease the Cu-to-ethylene π back-bonding. This latter interaction leads to a partial vacancy in the Cu 3d level, which manifests experimentally as a low-energy feature in the Cu K pre-edge, allowing for its direct observation and comparison within a series of Cu(I) compounds. The pre-edge feature is reproduced by TD-DFT calculations, and its energy position and total intensity are used to quantitatively probe Cu–ethylene bonding. The variations in the Cu electronic structure influence the stability and overall ethylene bonding strength of these compounds, ultimately showing how substituents on the supporting ligands have a notable effect on their physical and chemical properties.

Bis- and tris-pyridyl borate ligands containing pyridyl donor arms, a methylated boron cap, and a fluorine-lined coordination pocket have been prepared and utilized in coinage metal chemistry. The tris(pyridyl)borate ligand has been synthesized using a convenient boron source, [NBu4][MeBF3]. These N-based ligands permitted the isolation of group 11 metal–ethylene complexes [MeB(6-(CF3)Py)3]M(C2H4) and [Me2B(6-(CF3)Py)2]M(C2H4) (M = Cu, Ag, Au). The gold complexes display the largest coordination-induced upfield shifts of the ethylene 13C resonance relative to that of the free ethylene in their NMR spectra, while the silver complexes show the smallest shift. Solid-state structures of five of these metal–ethylene complexes as well as the related free ligands were established by X-ray crystallography. Surprisingly, all three [MeB(6-(CF3)Py)3]M(C2H4) adopt the rare κ2coordination mode rather than the typical κ3coordination mode of facial capping tridentate ligands. Computational analyses indicate that κ2coordination mode is favored over the κ3-mode in these coinage metal–ethylene complexes and point to the effects CF3-substituents have on κ2/κ3-energy difference. The M–C and M–N bond distances of [MeB(6-(CF3)Py)3]M(C2H4) follow the trend expected based on covalent radii of M(I) ions. The calculated ethylene–M interaction energy of κ2-[MeB(6-(CF3)Py)3]M(C2H4) indicated that the gold(I) forms the strongest interaction with ethylene. A comparison to the related poly(pyrazolyl)borates is also presented.

Treatment of bis(pyrazolyl)borate ligand supported [(CF3)2Bp]Cu(NCMe) with 1,2,3-trisubstituted cyclopropenes produced thermally stable copper(I) η2-cyclopropene complexes amenable to detailed solution and solid-state analysis. The [(CF3)2Bp]Cu(NCMe) also catalyzed [2 + 1]-cycloaddition chemistry of terminal and internal alkynes with ethyl diazoacetate affording cyclopropenes, including those used as ligands in this work. The tris(pyrazolyl)borate [(CF3)2Tp]Cu(NCMe) is a competent catalyst for this process as well. The treatment of [(CF3)2Tp]Cu with ethyl 2,3-diethylcycloprop-2-enecarboxylate substrate gave an O-bonded rather than a η2-cyclopropene copper complex.

Organic azide complexes of copper(I) and silver(I), [(SIPr)CuN(1-Ad)NN][SbF6], [(SIPr)CuN(2-Ad)NN][SbF6], [(SIPr)CuN(Cy)NN][SbF6], and [(SIPr)AgN(1-Ad)NN][SbF6] have been synthesized by using Ag[SbF6] and the corresponding organic azides with (SIPr)CuBr and (SIPr)AgCl (SIPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene). The copper and silver organic azide complexes were characterized by various spectroscopic techniques and X-ray crystallography. Group trends of isoleptic Cu(I), Ag(I), and Au(I) organic azide complexes are presented on the basis of experimental data and a detailed computational study. The νasym(N3) values of the metal-bound 1-AdNNN in [(SIPr)MN(1-Ad)NN]+follow the order Ag < Cu < Au. DFT calculations show that gold(I) forms the strongest bond with 1-AdNNN in this series, while silver has the weakest interaction. Furthermore, auxiliary ligand free coinage metal N-heterocyclic carbene complexes, [(SIPr)M][SbF6], have been synthesized via metathesis reactions of (SIPr)MCl (M = Cu, Ag, Au) with Ag[SbF6]. X-ray crystal structures of dinuclear [(SIPr)Ag]2[SbF6]2and [(SIPr)Au]2[SbF6]2are also reported. They show close metallophilic contacts. [(SIPr)Au]2[SbF6]2reacts with OEt2, SMe2, and CNtBu to afford [(SIPr)Au(OEt2)][SbF6], [(SIPr)Au(SMe2)][SbF6], and [(SIPr)Au(CNtBu)][SbF6] adducts, respectively.

This work describes the reaction of a cyclic trinuclear complex, {[3,5-(CF3)2Pz]Cu}3, with internal alkynes to construct di- and tetranuclear copper(I) complexes with short cuprophilic contacts and the study of their intriguing bonding and photophysical properties, both experimentally and theoretically. For comparison, we have also investigated the related copper(I) trifluoroacetate 3-hexyne complexes so as to deduce and isolate the role played by the supporting pyrazolate ligand on the luminescence of these and related complexes. Some adducts reported herein feature bridging (i.e., μ2–η2,η2-) alkyne coordination modes, which is rare for copper(I)–alkyne complexes documented in the literature. Raman data show red shifts in the average υ̅C≡Cstretching frequency from 2260 cm–1in free 3-hexyne to 2050 cm–1in the terminal η2-/2e-donor alkyne adduct Cu2(μ-[3,5-(CF3)2Pz])2(EtC≡CEt)2(1) and, more drastically, to 1874 cm–1in the bridged μ2–η2,η2-/4e-donor adduct Cu4(μ-[3,5-(CF3)2Pz])4(μ-EtC≡CEt)2(2). The tetranuclear 2-butyne adduct Cu4(μ-[3,5-(CF3)2Pz])4(μ-MeC≡CMe)2(3) also shows a large reduction in υ̅C≡Crelative to that of free 2-butyne. The effects of strengthened copper-alkyne interactions in the bridging relative to terminal alkynes are also reflected in the C—C≡C bending back angles. Photophysical studies in the solid state reveal the significance of the pyrazolate supporting ligand to bestow bright photoluminescence, which is found only for the pyrazolate-supported compounds 1–3but not the trifluoroacetate copper-alkyne complexes Cu2(μ-CF3CO2)2(EtC≡CEt)2(4) and Cu4(μ-CF3CO2)4(μ-EtC≡CEt)2(5). The orange phosphorescence with ∼50 μs lifetime at room temperature in 1–3thermochromically changes to generate additional green/yellow bands at cryogenic temperatures due to suppression of internal conversion from the respective T2→ T1states in each solid, whereas solvent effects lead to additional blue-shifted bands in glassy solvent media. Computational analyses explains the bonding and spectral results and suggest that the major excited-state distortion is due to significant (≥20°) rotation of the alkyne ligands on Cu(I) in the di- or tetranuclear adducts, as opposed to excimeric contraction of cuprophilic Cu(I)···Cu(I) distances. X-ray crystallographic data of 1–3and 5are also presented.

Quantum-chemical density functional theory calculations using the BP86 functional in conjunction with a triple-ζ basis set and dispersion correction by Grimme with Becke-Johnson damping D3(BJ) were performed for the title molecules. The nature of the bonding was examined with the quantum theory of atoms in molecules (QTAIM) and natural bond order (NBO) methods and with the energy decomposition analysis in conjunction with the natural orbital for chemical valence (EDA-NOCV) analysis. The energetically lowest-lying form of Fe2(CO)9is the triply bridged D3hstructure, whereas the most stable structures of Ru2(CO)9and Os2(CO)9are singly bridged C2species. The calculated reaction energies for the formation of the cyclic trinuclear carbonyls M3(CO)12from the dinuclear carbonyls M2(CO)9are in agreement with experiment, as the iron complex Fe2(CO)9is thermodynamically stable in these reactions, but the heavier homologues Ru2(CO)9and Os2(CO)9are not. The metal–CO bond to the bridging CO ligands is stronger than the bonds to the terminal CO ligands. This holds for the triply bridged D3hstructures as well as for the singly bridged C2or C2vspecies. The analysis of the orbital interactions with the help of the EDA-NOCV method suggests that the overall M→CO π backdonation is always stronger than the M←CO σ donation. The bridging carbonyls are more strongly bonded than the terminal CO ligands, and they are engaged in stronger σ donation and π backdonation, but the formation of bridging carbonyls requires reorganization energy, which may or may not be compensated by the stronger metal–ligand interactions. The lower-lying D3hform of Fe2(CO)9and C2structures of Ru2(CO)9and Os2(CO)9are due to a delicate balance of several forces.

The purpose of this study was to investigate the effects of different intervals between static stretching for hip adductor, quadriceps and hamstring muscles and resistance training in repetition performance.

The monoanionic bidentate ligand [(Ph3B)CH(3,5-(CH3)2Pz)2)]−has been prepared from lithium bis(pyrazolyl)methanide and triphenylborane. This useful new ligand is closely related to the well-established bis(pyrazolyl)borate and bis(pyrazolyl)methane ligands but has key differences to both analogues as well. The ethylene, cis-2-butene, and carbon monoxide adducts [(Ph3B)CH(3,5-(CH3)2Pz)2]Cu(L) (where L = C2H4, cis-CH3HCCHCH3, and CO) have been prepared from [(Ph3B)CH(3,5-(CH3)2Pz)2)]Li(THF), copper(I) triflate, and the corresponding coligand. These complexes have been characterized by NMR spectroscopy and X-ray crystallography. In all cases the bis(pyrazolyl) moiety is bound in κ2Nfashion with the BPh3group rotated to sit over the metal center, sometimes coordinating to the metal via phenyl carbons as in [(Ph3B)CH(3,5-(CH3)2Pz)2)]Li(THF) and [(Ph3B)CH(3,5-(CH3)2Pz)2]Cu(CO) or simply hovering above the metal site as in [(Ph3B)CH(3,5-(CH3)2Pz)2)]Cu(C2H4) and [(Ph3B)CH(3,5-(CH3)2Pz)2)]Cu(cis-CH3HCCHCH3). The 13C and 1H resonances of the ethylene carbon and protons of [(Ph3B)CH(3,5-(CH3)2Pz)2)]Cu(C2H4) appear at δ 81.0 and 3.71 ppm in CD2Cl2, respectively. The characteristic CO frequency for [(Ph3B)CH(3,5-(CH3)2Pz)2]Cu(CO) has been observed at υ̅ 2092 cm–1by infrared spectroscopy and is lower than that of free CO suggesting moderate M → CO π-back-donation. A detailed analysis of these complexes has been presented herein.

Background/Objectives:: Several studies reported associations of the lactase gene (LCT) polymorphism −13910C>T (rs4988235) with obesity-related variables and obesity in adults. This study aimed to replicate previously reported associations in a population sample of Portuguese young adults. Subjects/Methods:: We genotyped 447 subjects from central and northern regions of Portugal (mean age 20.81±4.24 years) for the lactase variant −13910C>T (rs4988235), using TaqMan probes. Anthropometric variables (weight, height and body fat) were measured using standardized procedures and body mass index (BMI) (kg/m2) was calculated. Results:: Frequency of genotypes was 35.8% CC (lactase nonpersistent, LNP), 48.1% CT and 16.1% TT, consistent with Hardy–Weinberg equilibrium (P=1). The frequency for the minor −13910 T allele was 0.402. Assuming a dominance model for the lactase persistence (LP) minor T-allele, linear regression models showed statistically significant associations between the LP genotype CT/TT and BMI, fat mass and weight (β=1.114, P=0.003; β=1.309, P=0.007 and β=2.67, P=0.021, respectively) after adjustment for age and sex. In concordance, logistic regression showed significant association between LP genotype CT/TT and overweight/obesity (OR=1.77; CI 1.08–2.92; P=0.023), as well as with high fat percentage ranges (OR=1.58; CI 1.01–2.46; P=0.041), when adjusting for age and sex. No significant interaction was obtained between the LCTpolymorphism and physical activity for BMI (Pint=0.454) or FAT % (Pint=0.421). Conclusions:: In the Portuguese sample of young adults, the lactase −13910C>T polymorphism revealed significant associations with the obesity-related anthropometric variables BMI, fat mass and weight, and previously observed associations with the obesity risk were also confirmed.

The synthesis and characterization of supramolecular assemblies {C60[M3]4}∞consisting of C60and coinage metal pyrazolates [M3](i.e., [(3,5-(CF3)2Pz)M]3, where Pz = pyrazolate and M = Au, Ag, and Cu) are reported. {C60[Cu3]4}∞, {C60[Ag3]4}∞and {C60[Au3]4}∞form isomorphous crystals. The [M3]moieties adopt a concave conformation to complement the convex C60surface. They exist as dimers of trimers (i.e., hexanuclear [M3]2units) that are held together by three close M···M metallophilic interactions at 3.1580(17), 3.2046(7), and 3.2631(7) Å for copper, silver, and gold systems, respectively. The [M3]2moieties surround each C60in a tetrahedral fashion, while each [M3]2is sandwiched by two C60molecules to form a supramolecular 3D assembly.

El objeto de este trabajo es resolver, en parte, la problemática de la visualización de conglomerados de partículas resultantes de métodos numéricos en la ingeniería. Se han desarrollado dos métodos para la eliminación de partículas no visibles desde cualquier punto de observación de la cámara. Estos se distinguen según el tipo de información disponible: modelos de partículas con información del contorno (malla de superficie) y modelos sin información del contorno (métodos sin mallas). En ambos casos, los resultados son buenos, pues se logra eliminar gran cantidad de partículas que no influyen en la imagen final.

Thallium(I) complexes of B-methylated and B-phenylated tris(pyridyl)borates featuring trifluoromethyl groups at the pyridyl ring 6-positions have been synthesized by metathesis using the corresponding potassium salts [MeB(6-(CF3)Py)3]K and [PhB(6-(CF3)Py)3]K with thallium(I) acetate. The closely related tris(pyrazolyl)borate analogue [PhB(3-(CF3)Pz)3]Tl has also been prepared, and comparisons of structural and spectroscopic features between the two scorpionate families are presented. [MeB(6-(CF3)Py)3]Tl displays κ3-coordination of the tris(pyridyl)borate similar to that of tris(pyrazolyl)borate in [MeB(3-(CF3)Pz)3]Tl, while [PhB(6-(CF3)Py)3]Tl and [PhB(3-(CF3)Pz)3]Tl feature κ2-N,Nligand coordination modes with the B-phenyl groups flanking the thallium sites. 19F NMR spectroscopy of [MeB(6-(CF3)Py)3]Tl reveals the presence of a remarkably large 1208 Hz four-bond thallium–fluorine coupling constant in chloroform at room temperature, which is considerably larger than 878 Hz observed for the pyrazolyl borate analogue [MeB(3-(CF3)Pz)3]Tl. Although [PhB(6-(CF3)Py)3]Tl is structurally nonrigid at room temperature in chloroform, at lower temperatures, the ligand arm exchange slows down, revealing 4JTl–F= 1110 Hz. Steric demands of these ligands have been quantified using the buried volume concept. In addition, ligand transfer chemistry from [MeB(6-(CF3)Py)3]Tl and [PhB(6-(CF3)Py)3]Tl to copper(I) under ethylene and computational analyses of the various coordination modes of tris(pyrazolyl)borates and tris(pyridyl)borates are reported.

There is a great heterogeneity in the prevalence of Chronic Obstructive Pulmonary Disease (COPD) across the world. The Burden of Obstructive Lung Disease (BOLD) initiative was started to measure the prevalence of COPD in a standardized way. We aimed to estimate the prevalence of COPD in Portuguese adults aged 40 years or older of a target population of 2,700,000 in the Lisbon region, in accordance with BOLD protocol.

Golden trefoils: Tris(alkyne)gold complex [(coct)3Au][SbF6] (see picture; 1‐SbF6) can be synthesized from cyclooctyne (coct) and AuSbF6generated in situ. Treatment of AuCl with cyclooctyne led to the bis(alkyne)gold complex [Au(coct)2Cl] (2). DFT analysis indicates that the cyclooctyne ligands are net electron donors in 1but overall electron acceptors in 2. AuSbF6is shown to mediate [2+2+2] cycloaddition reactions of alkynes.

Cyclooctin und in situ erzeugtes AuSbF6reagieren zu dem Tris(alkin)gold‐Komplex [(coct)3Au][SbF6] (1‐SbF6; siehe Bild). Die Behandlung von AuCl mit Cyclooctin ergibt den Bis(alkin)gold‐Komplex [Au(coct)2Cl] (2). Eine DFT‐Analyse deutet darauf hin, dass die Cyclooctin‐Liganden in 1insgesamt als Elektronendonoren, in 2hingegen insgesamt als Elektronenakzeptoren auftreten. AuSbF6kann ferner [2+2+2]‐Cycloadditionen von Alkinen vermitteln.

New copperI complexes have been synthesized from the reaction between [CuCH3CN4]PF6or CuI, triphenylphosphane, tertbutyl isocyanide or cyclohexyl isocyanide coligands, and the fluorinated pyrazolylborate ligands sodium trihydro[5trifluoromethylpyrazol1yl]borate and potassium dihydrobis[3trifluoromethylpyrazol1yl]borate. These compounds have been characterized by elemental analysis, FTIR and multinuclear 1H, 13C, 19F and 31P NMR spectroscopy, and ESI mass spectrometry. The solidstate structure of [{H3B[5CF3pz]}CuPPh32] is also reported. This complex features a κ2N,Hbonded trihydropyrazolylborate ligand, a rare Cu–HB bond, and a distorted, pseudotetrahedral copper atom with a large P–Cu–P angle. The solid state structures of [{H2B[3CF3pz]2}CuCNtBu2] and [{H2B[3CF3pz]2}CuCNCy2], which have pseudotetrahedral copper sites, are also reported. The bispyrazolylborate ligand in these complexes acts as a κ2N,N′donor and adopts a flattened boat conformation. © WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009

Despite the interest in them, easily isolable and thermally stable CuI, AgI, and AuI complexes of ethylene are stilllimited and get increasingly sparse as one descends the group 11 triad towards gold. Recently, there have been some notable developments in this field, including the isolation of gold–ethylene complexes and coinage-metal adducts with more than one ethylene molecule on a metal center. This article focuses on the chemistry of coinage-metal–ethylene adducts that have been synthesized and characterized by X-ray crystallography. Thus far, bidentate and tridentate donors based on nitrogen appear to be the ligands of choice forstabilizing species with an M–C2H4 (M = CuI, AgI, and AuI) moiety. Weakly donating ligands and anions are also commonly used, as they do not interfere with and displace the ethylene from the metal center. The ethylene 13C NMR chemical shift provides useful information about the nature of the metal–ethylene interaction. In some adducts (especially those with relatively weak M–C2H4 interactions), the change in the C=C bond length upon coordination to the metal site is difficult to discern because it falls within the errors associated with the crystallographically determined C=C bond length value. IR and Raman C=C stretching data would be useful but, probably due to the very weak nature of the IR band and the lack of convenient access to the Raman instruments, are often not reported. In this microreview, results from some computational and gas-phase spectroscopic studies are also provided for comparison.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Abstract: Epiphytic microorganisms on the phyllosphere of traditional and high-yielding rice varieties were isolated from different agroecological zones of Sri Lanka and screened for theirin vitro andin vivo antagonism againstRhizoctonia solani Kühn AG-1 1A, the sheath blight pathogen of rice. Among a total of 196 bacterial and 91 fungal isolates, 12 bacterial and two fungal isolates which showed more than 50% growth inhibition ofR. solani were tested for theirin vivo antagonism. Among the 14 antagonists tested, six bacterial and one fungal isolate substantially reduced the incidence of sheath blight (by more than 82%) and severity (by more than 92%) of the rice varieties BG94-1 and IR8 grown in a pot experiment under open field conditions. Using five antagonists that showed the bestin vitro antagonism, a pot experiment was conducted to determine whether the presence of indigenous microflora on the rice sheath had any effect on the effectiveness of antagonism. Three isolates (B4, GbB5 and HMWB4) controlled sheath blight incidence and severity equally well in the presence and absence of indigenous microflora. Two isolates (BG352B1 and BG300B1) were more effective when they were introduced into the rice sheath without indigenous microflora. Among the effective antagonists determined by the pot experiment, isolates B4, B16, BG94-1B5, GbB5, HMWB4 and BG379-F2 were tested under field conditions for two consecutive growing seasons. Under field conditions, severity of rice sheath blight was significantly reduced by the application of all the tested antagonists as a spray on rice sheath at a concentration of 108 cfu ml−1, starting 3 days after the development of symptoms and continuing for three applications at 10-day intervals. Antagonistic performances were consistent in the two seasons under field conditions andB. megatarium A (isolate B16) andAspergillus niger (isolate BG379-F2) performed as the most effective antagonists in both seasons. When disease severity was quantified as percentage sheath area covered by the disease lesions, the respective reductions in disease severity were greater than 50% and 61% byB. megaterium A (isolate B16) andAspergillus niger (isolate BG379-F2), respectively, in both seasons.

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Treatment of 1,3,5-triazapentadienes [N{(C3F7)C(Mes)N}2]H and [N{(C3F7)C(Dipp)N}2]H (where Mes = 2,4,6-Me3C6H2; Dipp = 2,6-Pri2C6H3) with n-BuLi in hexane, followed by the crystallization from hexane–THF mixture afforded the corresponding lithium 1,3,5-triazapentadienyl complexes as their THF solvates. X-Ray crystallographic analyses revealed that [N{(C3F7)C(Mes)N}2]Li(THF)2and [N{(C3F7)C(Dipp)N}2]Li(THF) are monomeric in the solid state. [N{(C3F7)C(Mes)N}2]Li(THF)2has a four-coordinate lithium center with a distorted tetrahedral geometry, and features a boat-shaped C2N3Li metallacycle. [N{(C3F7)C(Dipp)N}2]Li(THF) has a three-coordinate lithium atom and a planar, U-shaped C2N3ligand backbone. The synthesis, solid-state structure, and 1H and 19F NMR spectroscopic details of [N{(C3F7)C(Mes)N}2]H are also reported.

The odd–odd 58Co nucleus has been studied with the 51V(10B, p2n) reaction at 33 MeV and 36 MeV incident energy using the γ-spectrometer Saci-Pererê. Excited states up to 8.0 MeV and spin up to 11+ have been observed. DSAM lifetimes for 13 excited states were measured. The results are compared to shell model calculations using the GXPF1 effective interaction, developed for use in the fp shell.

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Tetrahydrobenzimidazoles, on treatment with dimethyldioxirane, rearrange to provide 5-imidazolones exclusively. These rearrangements proceed with a broad range of substrates and with good to excellent levels of diastereoselectivity.

The ethylene adducts of copper(I) tris(pyrazolyl)borates, [HB(3,5-(CF3)2Pz)3]Cu(C2H4), [HB(3-(CF3),5-(C6H5)Pz)3]Cu(C2H4), and [HB(3-(CF3)Pz)3]Cu(C2H4), have been prepared by reacting the corresponding sodium derivative with CF3SO3Cu in the presence of ethylene. They were characterized both in the solid state and in solution using ¹H, ¹³C, and ¹⁹F NMR and IR spectroscopy and by X-ray crystallography. Solid samples of these nonionic copper complexes featuring fluorinated tris(pyrazolyl)borate ligands display notably high stability toward air oxidation and ethylene loss. The ¹H NMR chemical shifts of the copper(I)-bonded ethylene protons appear in the 4.8−5.2 ppm region. The ¹³C signal of copper-coordinated ethylene shows an upfield shift of about 35 ppm, whereas the ¹JC-H shows a minor change (an increase of about 2−5 Hz) compared to the values for free ethylene. X-ray structural data show the presence of pseudo-tetrahedral copper ions and η²-bonded ethylene units and relatively unperturbed ethylene C−C distances. The copper adducts [HB(3,5-(CF3)2Pz)3]Cu(C2H4) and [HB(3-(CF3),5-(C6H5)Pz)3]Cu(C2H4) are competent aziridination catalysts, readily converting a variety of olefins into the corresponding N-tosyl aziridines with N-tosyl phenyliodinane.

The influence of low-lying discrete nuclear states on isotopic abundances in presupernova cores, is discussed. Assuming the hypothesis of nuclear statistical equilibrium (NSE), the Saha equation has been solved for a set of 65 nuclear species (including free protons and neutrons). Experimental data have been used in the calculation of the first terms of the nuclear partition function. The obtained abundances are compared with those evaluated using an energy level density in the computation of the nuclear partition function. We conclude that in future calculations involving isotopic abundances in presupernova cores, the low-lying nuclear states need to be treated as discrete ones when experimental data are available.

The synthesis of several 4-vinylimidazoles via Stille cross-coupling reactions of the corresponding protected 4-iodoimidazoles with tributylvinylstannane is described. These heterocyclic dienes are shown to be effective partners in the Diels−Alder reaction, providing adducts in good yield and exhibiting useful levels of isomer selectivity and stereoselectivity (endo/exo).

The pyridine-based poly(pyridyl)borates are a recent addition to the scorpionate family. Furthermore, pyridyl ring substituted analogues are also rare. The synthesis of a bis(pyridyl)borate featuring trifluoromethyl substituted pyridyl donor arms and its utility in isocyanide and carbonyl chemistry of copper(I) and silver(I) have been described together with related molecules supported by a fluorinated tris(pyridyl)borate, and a comparison to the better-known poly(pyrazolyl)borate relatives. X-ray crystal structures of copper and silver complexes show that the B-arylated, bis- and tris(pyridyl)borate ligands use only two pyridyl moieties for metal ion coordination. Flanking B-aryl groups close to metal sites are also a common feature in copper and silver complexes supported by [Ph2B(6-(CF3)Py)2]−and [t-BuC6H4B(6-(CF3)Py)3]−. The CN stretching frequencies of the t-BuNC complexes of Cu(I) and Ag(I) are notably higher than that of the free t-BuNC. The CO stretch of the analogous fluorinated poly(pyridyl)borate ligand supported metal carbonyls lies closer to that of the free CO, indicating the presence of fairly Lewis acidic metal sites. Metal bound carbonyl stretching frequencies of comparable poly(pyridyl)borate and poly(pyrazolyl)borate have been utilized to gauge the relative donor properties of the two ligand families.

Syntheses and characterizations are described for C−H insertion products derived from 1,3-dimesityldihydroimidazol-2-ylidene (1) with acetylene, acetonitrile, methyl phenyl sulfone, and chloroform. In the reaction with acetylene, both acetylenic H-atoms are reactive so that 1 : 1 and 2 : 1 adducts can be obtained. The acetylene and methyl-phenyl-sulfone adducts are structurally characterized by means of single-crystal X-ray structure determinations. The reactions of 1,3,4,5-tetramethylimidazolidin-2-ylidene (8) with chloroform or chlorodifluoromethane are shown to yield 2-(dihaloalkyl)imidazolium salts that arise from a failure of the intermediate 2-protioimidazolium salt to capture the initially formed halocarbanion.

Abstract: The synthesis and structures of [(i-Pr)2ATI]Li2(thf)(I)(1) and [(i-Pr)2ATI]Ca(thf)2(I)2Li2(thf)2-[(i-Pr)2ATI] (2) (where [(i-Pr)2ATI]=N-isopropyl-2-(isopropylamino)troponiminate) have been described. The lithium atoms in compounds1 and2 occupy positions above and below the plane of the aminotroponiminate ligand. The calcium atom in2 adopts a pseudo-octahedral geometry with two tetrahydrofurans occupying thetrans-positions. Compound1 crystallizes as dimeric units. Crystal data with MoKα at 193 K:1, C17H27ILi2N2O,a=13.217(2)Å,b=9.875(2)Å,c=16.410(4)Å, B=111.41(1)o,V=1993.4(6)Å3, a monoclinic space groupP21/n,Z=4,R=0.029;2, C42H70CaI2Li2N4O4,a=911.390(2)Å,b=30.880(4)Å,c=13,465(2)Å, B=93.85(1)o,V=4724(1)Å3, monoclinic space groupC2/c,Z=4,R=0.027.

3-(Pentafluoroethyl)pyrazole and 3-(heptafluoropropyl)pyrazole were synthesized and fully characterized. These pyrazoles react with NaBH4 to yield sodium salts of [HB(3-(C2F5)Pz)3]^- and [HB(3-(C3F7)Pz)3]^-. The X-ray crystal structure of [HB(3-(C2F5)Pz)3]Na(3-(C2F5)PzH) shows close contacts between the sodium atom and fluorine atoms of the −C2F5 substituents. The copper−carbon monoxide adducts [HB(3-(C2F5)Pz)3]CuCO and [HB(3-(C3F7)Pz)3]CuCO were prepared by the treatment of CuOTf with 1 equiv of the corresponding tris(pyrazolyl)boratosodium under CO. The copper and sodium complexes were characterized by ¹H, ¹³C, and ¹⁹F NMR and IR spectroscopies. IR spectroscopic data of [HB(3-(CF3)Pz)3]CuCO, [HB(3-(C2F5)Pz)3]CuCO, and [HB(3-(C3F7)Pz)3]CuCO did not exhibit a significant difference in the υCO values, but they are notably lower than the corresponding υCO values of the 3,5-disubstituted analog [HB(3,5-(CF3)2Pz)3]CuCO.

In a previous paper we showed that an extended Schrödinger equation (ESE) can lead to critical phenomena. The ESE was defined as an integro-differential Schrödinger equation obtained from the traditional differential Schrödinger equation by extending the local potential to a non-local potential. Here we pursue further this procedure by constructing a class of such ESE which is able to generate the (quantum) squeezing phenomenon. As an example, we discuss a model by Glauber for particle trapping by oscillating fields, in the present perspective.

In this paper we report the difference between the squeezing effect for quadrature operators (describing a photon field or harmonic oscillator) and for spin variables (describing a two-level system), the distinctions coming from the bound and unbound character of the operators involved in the definition of squeezing for each system.

We have performed quasi-particle calculations for the tin isotopes 119Sn, 121Sn and 123Sn, using realistic effective interactions derived from the Paris and Bonn-A NNpotentials. A number-projected one- and three-quasi-particle formalism in the (g72, d52, d32, s12, h112) model space is employed. We have used a folded-diagram method to derive the corresponding model-space effective interaction, starting from the G-matrix elements derived from the above NNpotentials. The G-matrix Pauli-exclusion operator Q2, specified by the shell-model orbitals (n1, n2, n3) = (11, 21, 36), has been treated accurately. An almost pure (h112)3three-quasiparticle structure for the high spin states from J = 172−to 272−of the above nuclei has been observed. With practically no parameter adjustment, our calculated energies are in very good agreement with available experimental data.

The experimental information on the84Kr nuclei is compared with the model calculation in which two neutron holes are coupled to the vibrational field. Based on the lower-order terms of a perturbative expansion of theE2 andM1 transition matrix elements, a simple rule is obtained for the sign and the magnitude of thed (E2/M1) ratios for the transitions between the second and first 2+ states in some vibrational nuclei.

The hypervalent phosphorus compound, 3,7-di-t-butyl-5-aza-2,8-dioxa-1-phosphabicyclo-[3.3.0]octa-2,4,6-triene (ADPO) forms adducts with chromium, tungsten, nickel and palladium metal centers. All four new adducts contain tetrahedral phosphorus atoms as a result of folding of the ADPO unit. This folding of the planar 10-P-3 ADPO molecule to provide an 8-P-3 center for coordination to the transition metal center is the result of the close energy balance between 10-P-3 ADPO and 8-P-3 ADPO and the strength of the phosphorus-metal interaction. In the case of a homoleptic palladium(II) complex, dimerizati on of the coordinated ADPO unit was observed.