Organogermyl,Organostannyl, and Organoplumbyl Phosphines,Arsines, Stibines,and Bismuthines

The preparation, properties, and reactions of the compounds named in the title are described, with particular reference to the possible participation of (p→d)_π components in the bonding between the group IVB and the group VB elements.     

Pi bonding and negative hyperconjugation in mono-, di-, and triaminoborane, -alane, -gallane, and -indane

A systematic quantum chemical investigation of mono-, di-, and triaminoborane, -alane, -gallane, and -indane is carried out to determine quantitatively the effects of pi bonding and negative hyperconjugation on structures, energetics, and rotational barriers in these systems. Pi bonding plays a significant role in the aminoborane compounds, but becomes rapidly less significant in the aminoalanes, -gallanes, and -indanes. For each main-group metal X investigated, X-N rotational barriers are found to be essentially equal depending only on the number of remaining in-plane amino groups. The contribution of negative hyperconjugation to reducing rotational barriers, as assessed from natural bond orbital (NBO) delocalization energies, is independent of the pyramidalization of the out-of-plane amino group, and is also dependent only on the number of rotated groups. Optimized tris[bis(trimethylsilyl)amino]-substituted structures of boron, aluminum, gallium, and indium are found to compare quite well with available experimental structural data, and exhibit X-N torsion angles that are independent of the central metal atom.     

Transition-metal-free O-, S-, and N-arylation of alcohols, thiols, amides, amines, and related heterocycles

A new protocol for the Ullmann-type arylation process of different aromatic heterocycles without any transition-metal catalyst, implying the use of a combination of an excess of potassium hydroxide and dimethyl sulfoxide, is described. The reaction can be performed between a broad range of starting nucleophiles including phenol, alcohols, amines, nitrogen-containing five-membered systems such as pyrazoles, imidazoles, and indoles, and amides with haloarenes, iodide and bromide derivatives giving the best results, the possible pathway involving the in situ generation of the corresponding benzyne intermediate. When the reaction was performed with 2-iodoaniline and either carboxamides or isothiocyanato derivatives, the corresponding benzoazole derivatives were obtained.     

Structural, magnetic, and spectroscopic studies of YAgSn, TmAgSn, and LuAgSn

The rare earth-silver-stannides YAgSn, TmAgSn, and LuAgSn were synthesized from the elements by arc-melting and subsequent annealing. The three stannides were investigated by X-ray powder and single-crystal diffraction: NdPtSb type, P6₃mc, Z=2, a=468.3(1), pm, wR₂=0.0343, 353 F² values, 12 variables for YAgSn, and ZrNiAl type, P6¯2 m, a=726.4(2), , wR₂=0.0399, 659 F² values, 15 variables for TmAgSn, and a=723.8(2), , wR₂=0.0674, 364 F² values, 15 variables for LuAgSn. Besides conventional laboratory X-ray data with monochromatized Mo radiation, the structures were also refined on the basis of synchrotron data with , in order to clarify the silver-tin ordering more precisely. YAgSn has puckered, two-dimensional [AgSn] networks with Ag-Sn distances of 278 pm, while the [AgSn] networks of TmAgSn and LuAgSn are three-dimensional with Ag-Sn distances of 279 and 284 pm for LuAgSn. Susceptibility measurements indicate Pauli paramagnetism for YAgSn and LuAgSn. TmAgSn is a Curie-Weiss paramagnet with an experimental magnetic moment of 7.2 μ_B/Tm. No magnetic ordering is evident down to 2 K. The local environments of the tin sites in these compounds were characterized by ¹¹⁹Sn Mössbauer spectroscopy and solid-state NMR (in YAgSn and LuAgSn), confirming the tin site multiplicities proposed from the structure solutions and the absence of Sn/Ag site disordering. Mössbauer quadrupolar splittings were found in good agreement with calculated electric field gradients predicted quantum chemically by the WIEN2k code. Furthermore, an excellent correlation was found between experimental ¹¹⁹Sn nuclear magnetic shielding anisotropies (determined via MAS-NMR) and calculated electric field gradients. Electronic structure calculations predict metallic properties with strong Ag-Sn bonds and also significant Ag-Ag bonding in LuAgSn.     

Pyrenes,Peropyrenes, and Teropyrenes: Synthesis,Structures, and Photophysical Properties

The design of a relatively simple and efficient method to extend the π‐conjugation of readily available aromatics in one‐dimension is of significant value. In this paper, pyrenes, peropyrenes, and teropyrenes were synthesized through a double or quadruple benzannulation reaction of alkynes promoted by Brønsted acid. This novel method does not involve cyclodehydrogenation (oxidative aryl–aryl coupling) to arrive at the newly incorporated large arene moieties. All of the target compounds were synthesized in moderate to good yields and were fully characterized with the structures unambiguously confirmed by X‐ray crystallography. As expected, photophysical characterization clearly shows increasing red‐shifts as a function of extended conjugation within the fused ring systems.     

Borinium, borenium, and boronium ions: synthesis, reactivity, and applications

Boron cations are elusive and highly electrophilic species that play a key role in the chemistry of boron. Despite early interest in the chemistry of boron cations, until recently they have largely remained chemical curiosities. However, hints at harnessing their potential as potent electrophiles have begun to appear and developments in weakly coordinating anion technology suggest that this is an area of research that is ripe for exploration. It has been nearly 20 years since the last major review on boron cations; herein we summarize the progress in the area since that time.     

Mild, powerful, and robust methods for esterification, amide formation, and thioesterification between acid chlorides and alcohols, amines, thiols, respectively

We developed two efficient practical methods for esterification, amide formation, and thioesterification between acid chlorides and alcohols, amines, thiols, respectively. The present mild and robust reaction was performed by two separate methods both by combining cheap and readily available amines, N-methylimidazole, and N,N,N′,N′-tetramethylethylenediamine (TMEDA). Method A uses catalytic N-methylimidazole and TMEDA with an equimolar amount of K₂CO₃, whereas Method B uses equimolar amounts of N-methylimidazole and TMEDA. The salient features are as follows. (i) With regard to reactivity, Method B was superior to Method A for esterification and thioesterification, whereas cost-effective Method A was superior to Method B for amide formation. (ii) Amide formation proceeded smoothly between acid chlorides and less nucleophilic and stereocongested amines such as 2,6-dichloroaniline. (iii) This protocol was applied to the successful synthesis of two agrochemicals, bromobutide and carpropamid.     

Pyrenes,Peropyrenes, and Teropyrenes: Synthesis,Structures, and Photophysical Properties

The design of a relatively simple and efficient method to extend the π‐conjugation of readily available aromatics in one‐dimension is of significant value. In this paper, pyrenes, peropyrenes, and teropyrenes were synthesized through a double or quadruple benzannulation reaction of alkynes promoted by Brønsted acid. This novel method does not involve cyclodehydrogenation (oxidative aryl–aryl coupling) to arrive at the newly incorporated large arene moieties. All of the target compounds were synthesized in moderate to good yields and were fully characterized with the structures unambiguously confirmed by X‐ray crystallography. As expected, photophysical characterization clearly shows increasing red‐shifts as a function of extended conjugation within the fused ring systems.     

Structure and properties of HOO,HOS, HSO,HSS, FSO,FOS and FSS

High quality SCF-MO calculations are reported for the title molecules, including geometry optimization. One-electron properties are presented and discussed, and relative stabilities of (HOS, HSO) and (FOS, FSO) compared. Little experimental geometric data are available at present, but the calculated and experimental geometries of HO₂ agree well.     

Acrolein polymerization: Monodisperse,homo, and hybrido microspheres,synthesis, mechanism,and reactions

Monodisperse polyacrolien (PA) microspheres were obtained by a single step process via two mechanisms: (a) aqueous polymerization of acrolein under alkaline conditions and (b) aqueous radical polymerization of acrolein by irradiation with a cobalt source. The diameter of the former microspheres can be varied from 0.04 up to 8 μm. The monodispersity of the system is also discussed. The diameter of the latter microspheres can be varied up to 0.2 μm. Hybrido PA microspheres were formed by grafting PA microspheres of average diameter of 0.1 μm obtained by irradiation onto the surface of PA microspheres produced by the alkaline mechanism. The aldehyde content of the microspheres prepared by irradiation is much higher than those of the microspheres formed under alkaline conditions. The aldehyde groups were used for the covalent binding of ligands containing primary amino groups, such as proteins and drugs, in a single step under physiological pH.     

Intermetallic compounds of the heaviest elements and their homologs: the electronic structure and bonding of MM', where M=Ge, Sn, Pb, and element 114, and M'=Ni, Pd, Pt, Cu, Ag, Au, Sn, Pb, and element 114

Fully relativistic (four-component) density-functional theory calculations were performed for intermetallic dimers MM', where M=Ge, Sn, Pb, and element 114, and MM'=group 10 elements (Ni, Pd, and Pt) and group 11 elements (Cu, Ag, and Au). PbM and 114M, where M are group 14 elements, were also considered. The results have shown that trends in spectroscopic properties-atomization energies D(e), vibrational frequencies omega(e), and bond lengths R(e), as a function of MM', are similar for compounds of Ge, Sn, Pb, and element 114, except for D(e) of PbNi and 114Ni. They were shown to be determined by trends in the energies and space distribution of the valence ns(MM')atomic orbitals (AOs). According to the results, element 114 should form the weakest bonding with Ni and Ag, while the strongest with Pt due to the largest involvement of the 5d(Pt) AOs. In turn, trends in the spectroscopic properties of MM' as a function of M were shown to be determined by the behavior of the np(1/2)(M) AOs. Overall, D(e) of the element 114 dimers are about 1 eV smaller and R(e) are about 0.2 a.u. larger than those of the corresponding Pb compounds. Such a decrease in bonding of the element 114 dimers is caused by the large SO splitting of the 7p orbitals and a decreasing contribution of the relativistically stabilized 7p(1/2)(114) AO. On the basis of the calculated D(e) for the dimers, adsorption enthalpies of element 114 on the corresponding metal surfaces were estimated: They were shown to be about 100-150 kJ/mol smaller than those of Pb.     

Metal-Directed Formation of Tetra-, Hexa-, Octa-, and Nonanuclear Complexes of Magnesium,Calcium, Manganese,Copper, and Cadmium

Efficacious metal control of self-assembly of dialkylketipinate dianions leads to completely different supramolecular assemblies. The structures of grid 1 , double-decker 2 , triple-decker 3 , and metalla-spherand 4 were characterized by X-ray crystallographic analyses or by NMR spectroscopy.     

Formation,structure, composition,and catalytic properties of Ni-, Cu-, Mn-, Fe-, and co-containing films on aluminum

Layers containing oxygen compounds of copper and nickel and(or) of one of transition metals (manganese, cobalt, iron) were formed on an aluminum alloy by the plasma-electrolytic oxidation method. The layers were characterized by means of X-ray phase analysis, X-ray fluorescence microanalysis, and scanning electron microscopy and tested in the reaction of CO oxidation to CO₂.     

Seven germacranolides,eupaglehnins A,B, C,D, E,and F,and 2alpha-acetoxyepitulipinolide from Eupatorium glehni

Four new germacrane-type sesquiterpenoids with unsaturated acids as esters at the 8-position, two chlorine atom-containing lactones, 2alpha-acetoxyepitulipinolide, and 12 previously known compounds have been isolated from the MeOH extract of Eupatorium glehni (Compositae) and their structures have been determined on the basis of spectral data analyses.     

Catalysis in the Synthesis of S,N-Heterocycles and O,N-, S,N-, and O,S,N-Macroheterocycles

The review systemizes and generalizes published data on the catalytic syntheses of six-, seven-, and eight-membered S,N-heterocycles and O,N-, S,N-, and O,S,N-macroheterocycles.     

Cubane, cuneane, and their carboxylates: a calorimetric, crystallographic, calculational, and conceptual coinvestigation

[reaction: see text] This study is a multinational, multidisciplinary contribution to the thermochemistry of dimethyl1,4-cubanedicarboxylate and the corresponding isomeric, cuneane derivative and provides both structural and thermochemical information regarding the rearrangement of dimethyl 1,4-cubanedicarboxylate to dimethyl 2,6-cuneanedicarboxylate. The enthalpies of formation in the condensed phase at T = 298.15 K of dimethyl 1,4-cubanedicarboxylate (dimethyl pentacyclo[4.2.0.0.(2,5)0.(3,8)0(4,7)]octane-1,4-dicarboxylate) and dimethyl 2,6-cuneanedicarboxylate (dimethyl pentacyclo[3.3.0.0.(2,4)0.(3,7)0(6,8)]octane-2,6-dicarboxylate) have been determined by combustion calorimetry, delta(f) H(o)m (cr)/kJ x mol(-1) = -232.62 +/- 5.84 and -413.02 +/- 5.16, respectively. The enthalpies of sublimation have been evaluated by combining vaporization enthalpies evaluated by correlation-gas chromatography and fusion enthalpies measured by differential scanning calorimetry and adjusted to T = 298.15 K, delta(cr) (g)Hm (298.15 K)/kJ x mol(-1) = 117.2 +/- 3.9 and 106.8 +/- 3.0, respectively. Combination of these two enthalpies resulted in delta(f) H(o)m (g., 298.15 K)/kJ x mol(-1) of -115.4 +/- 7.0 for dimethyl 1,4-cubanedicarboxylate and -306.2 +/- 6.0 for dimethyl 2,6-cuneanedicarboxylate. These measurements, accompanied by quantum chemical calculations, resulted in values of delta(f) Hm (g, 298.15 K) = 613.0 +/- 9.5 kJ x mol(-1) for cubane and 436.4 +/- 8.8 kJ x mol(-1) for cuneane. From these enthalpies of formation, strain enthalpies of 681.0 +/- 9.8 and 504.4 +/- 9.1 kJ x mol(-1) were calculated for cubane and cuneane by means of isodesmic reactions, respectively. Crystals of dimethyl 2,6-cuneanedicarboxylate are disordered; the substitution pattern and structure have been confirmed by determination of the X-ray crystal structure of the corresponding diacid.     

Rare-Earth-compound nanowires, nanotubes, and fullerene-like nanoparticles: synthesis, characterization, and properties

Various low-dimensional nanostructures, such as nanowires, nanotubes, nanosheets, and fullerene-like nanoparticles have been selectively synthesized from rare-earth compounds (hydroxides, fluorides) based on a facile hydrothermal method. The subsequent dehydration, sulfidation, and fluoridation processes lead to the formation of rare-earth oxide, oxysulfide, and oxyhalide nanostructures, which can be functionalized further by doping with other rare-earth ions or by coating with metal nanoparticles. Owing to the interesting combination of novel nanostructures and functional compounds, these nanostructures can be expected to bring new opportunities in the vast research areas of and application in biology, catalysts, and optoelectronic devices.