Chiroptical Response of Carbon Nanocages Enhanced by Achiral Guests.

Opening up [60]fullerene makes itself inherently chiral without loss of congenital π-conjugation. An immoderately large aperture on [60]fullerene, however, renders the molecule less rigid and therefore it would reduce dissymmetry factors. Herein, we examined supramolecular technique in geometrical reinforcement of chiral open-[60]fullerenes by encasing achiral guests such as Ar, CO, and CHCN.

Dialkyl Carbonate Synthesis Using Atmospheric Pressure of CO.

Dialkyl carbonates (DRCs) are valuable compounds widely used in the industry. The synthesis of DRC from CO has attracted interest as an alternative to the current method, which uses phosgene. However, the reported approaches for DRC synthesis from CO requires high-pressure and high-concentration CO, resulting in elevated costs associated with CO purification and manufacturing facilities.

Electrophilic Behavior of the "Nucleophilic" Pyramidane: Reactivity of Ge-Pyramidane towards Organolithium Reagents.

The particular reactivity of the recently discovered class of the main group element polyhedral clusters, pyramidanes, remains largely unexplored. In this communication, we report the reaction of the germapyramidane with tert-butyllithium leading to the rather unusual organogermanium compound [Li(thf)]⋅2, as the product of the formal insertion of a Ge-apex into the C-Li bond. This reactivity mode exemplifies unusual electrophilic behaviour of a pyramidane, which is a priori considered as a nucleophilic reagent.

Direct Conversion of Low-Concentration CO into -Aryl and -Alkyl Carbamic Acid Esters Using Tetramethyl Orthosilicate with Amidines as a CO Capture Agent and a Catalyst.

Herein, we report the direct conversion of low-concentration CO (15 vol %), equivalent to the CO concentration in the exhaust gas from a thermal power station, into carbamic acid esters (CAEs), which are precursors for pharmaceuticals, agrochemicals, and isocyanates. The reaction was performed using Si(OMe) as a nonmetallic regenerable reagent and 1,8-diazabicyclo[5.4.

Controlled Growth of Platinum Nanoparticles on Amorphous Silica from Grafted Pt-Disilicate Complexes.

Supported platinum nanoparticles are currently the most functional catalysts applied in commercial chemical processes. Although investigations have been performed to improve the dispersion and thermal stability of Pt particles, it is challenging to apply amorphous silica supports to these systems owing to various Pt species derived from the non-uniform surface structure of the amorphous support. Herein, we report the synthesis and characterization of amorphous silica-supported Pt nanoparticles from (cod)Pt-disilicate complex (cod = 1,5-cyclooctadiene), which forms bis-grafted surface Pt species regardless of surface heterogeneity.

From SiO to Alkoxysilanes for the Synthesis of Useful Chemicals.

The transformation of silica (SiO) to useful chemicals is difficult to explore because of the strength of the Si-O bond and thermodynamic stability of the SiO structure. The direct formation of alkoxysilanes from SiO has been explored as an alternative to the carbothermal reduction (1900 °C) of SiO to metallic silicon (Si) followed by treatment with alcohols. The base-catalyzed depolymerization of SiO with diols and monoalcohols afforded cyclic silicon alkoxides and tetraalkoxysilanes, respectively.

N-Aryl and N-Alkyl Carbamates from 1 Atmosphere of CO.

We have successfully isolated and characterized the zinc carbamate complex (phen)Zn(OAc)(OC(=O)NHPh) (1; phen=1,10-phenanthroline), formed as an intermediate during the Zn(OAc) /phen-catalyzed synthesis of organic carbamates from CO , amines, and the reusable reactant Si(OMe) . Density functional theory calculations revealed that the direct reaction of 1 with Si(OMe) proceeds via a five-coordinate silicon intermediate, forming organic carbamates. Based on these results, the catalytic system was improved by using Si(OMe) as the reaction solvent and additives like KOMe and KF, which promote the formation of the five-coordinated silicon species.

Design and assessment of an energy self-supply process producing tetraethyl orthosilicate using rice husk.

Combusting rice husk (RH) generates energy and rice husk ash (RHA) containing high amount of silica. Recent studies showed RHA can directly react with ethanol for producing tetraethyl orthosilicate (TEOS), an important substance for different industries. Nevertheless, this process requires an intensive energy supply.

Bidentate Disilicate Framework for Bis-Grafted Surface Species.

Recent advances in surface organometallic chemistry have enabled the detailed characterization of the surface species in single-site heterogeneous catalysts. However, the selective formation of bis-grafted surface species remains challenging because of the heterogeneity of the supporting surface. Herein, we introduce a metal complex bearing bidentate disilicate ligands, -OSi(O Bu) OSi(O Bu) O-, as a molecular precursor, which has a silicate framework adjacent to the metal (Pt) center.

Fluoride Ion-Initiated Decarboxylation of Silyl Alkynoates to Alkynylsilanes.

This communication describes the development of a metal-free catalytic decarboxylation of silyl alkynoates to alkynylsilanes. Treatment of a silyl alkynoate with a catalytic amount of tetrabutylammonium difluorotriphenylsilicate (TBAT) in ,-dimethylformamide at 150 °C resulted in decarboxylation to give the corresponding alkynylsilane in good to excellent yield (75 → 95%). The TBAT system was applicable to the decarboxylation of sterically demanding silyl alkynoates such as -butyldiphenylsilyl 3-phenylpropiolate.

One-pot catalytic synthesis of urea derivatives from alkyl ammonium carbamates using low concentrations of CO.

To reduce anthropogenic carbon dioxide (CO) emissions, it is desirable to develop reactions that can efficiently convert low concentrations of CO, present in exhaust gases and ambient air, into industrially important chemicals, without involving any expensive separation, concentration, compression, and purification processes. Here, we present an efficient method for synthesizing urea derivatives from alkyl ammonium carbamates. The carbamates can be easily obtained from low concentrations of CO as present in ambient air or simulated exhaust gas.

Synthesis and Structure of Multinuclear Pd(II) Complexes Bridged by Phosphide or Azide Ligands.

The synthesis and structure of phosphide- and azide-bridged multinuclear Pd(II) complexes bearing phosphine ligands [PdX(μ-X')(PR)] (X = Cl and N; X' = PR and N; = 2 and 4) are reported. The oxidative addition of R PCl to Pd(PMe) furnished the phosphide-bridged dinuclear Pd(II) complexes [PdCl(μ-PR )(PMe)] [R' = Pr () and Cy ()]. However, the oxidative addition of (-tolyl)PCl to Pd(PMe) produced a nonbridged mononuclear Pd(II) complex with the bis(-tolyl)phosphinic ligand, -[Pd(PMe){P(O)(-tolyl)}] (), via oxidation of the phosphinyl ligand.

Sustainable Catalytic Synthesis of Diethyl Carbonate.

New sustainable approaches should be developed to overcome equilibrium limitation of dialkyl carbonate synthesis from CO and alcohols. Using tetraethyl orthosilicate (TEOS) and CO with Zr catalysts, we report the first example of sustainable catalytic synthesis of diethyl carbonate (DEC). The disiloxane byproduct can be reverted to TEOS.

Wet and Dry Processes for the Selective Transformation of Phosphonates to Phosphonic Acids Catalyzed by Brønsted Acids.

A "wet" process and two "dry" processes for converting phosphonate esters to phosphonic acids catalyzed by a Brønsted acid have been developed. Thus, in the presence of water, a range of alkyl-, alkenyl-, and aryl-substituted phosphonates can be generally hydrolyzed to the corresponding phosphonic acids in good yields catalyzed by trifluoromethyl sulfonic acid (TfOH) at 140 °C (the wet process). On the other hand, with specific substituents of the phosphonate esters, the conversion to the corresponding phosphonic acids can be achieved under milder conditions in the absence of water (the dry process).

Regioselective Diels-Alder reaction to open-cage ketolactam derivatives of C.

Open-cage ketolactam fullerenes reacted with dienes on the rim of the orifice both regio- and stereoselectively. Unequivocal evidence for the structure of the Diels-Alder adduct was provided by 2D INADEQUATE C NMR studies on C enriched material, as well as via DFT-GIAO calculations. The theoretical calculations successfully model the regioselective and the endo stereoselective reaction, predicting molecular orbital control along with a repulsive steric interaction between the substituents on the nitrogen atom and those on the diene.

Halogen-Free Synthesis of Carbamates from CO and Amines Using Titanium Alkoxides.

A direct synthesis of carbamates from amines and carbon dioxide in the presence of Ti(OR) (R=nBu (1), Me (2), Et (3), nPr (4)) was investigated. Aniline was reacted with titanium n-butoxide (1) in the presence of carbon dioxide (5 MPa) to give the corresponding n-butyl N-phenylcarbamate (BPC) in nearly quantitative yield (99 %) within 20 min. Furthermore, 1 could be regenerated upon reaction with n-butanol during water removal.

A Simple Zinc Catalyst for Carbamate Synthesis Directly from CO.

Several zinc salts were employed as catalysts for the synthesis of carbamates directly from aromatic amines, CO , and silicate esters. Zn(OAc) offered the best performance among the salts tested. The addition of an N-donor ligand such as 1,10-phenanthroline increased the yield.

Synthesis of cyclic sulfites from epoxides and sulfur dioxide with silica-immobilized homogeneous catalysts.

Quaternary ammonium- and amino-functionalized silica catalysts have been prepared for the selective synthesis of cyclic sulfites from epoxides and sulfur dioxide, demonstrating the effects of immobilizing the homogeneous catalysts on silica. The cycloaddition of sulfur dioxide to various epoxides was conducted under solvent-free conditions at 100 °C. The quaternary ammonium- and amino-functionalized silica catalysts produced cyclic sulfites in high yields (79-96 %) that are comparable to those produced by the homogeneous catalysts.

The first halogen-substituted cyclotrigermenes: a unique halogen walk over the three-membered ring skeleton and facial stereoselectivity in the Diels-Alder reaction.

Dark red crystals of the halogen-substituted cyclotrigermenes [(tBu3Si)3Ge3X; X = Cl, Br, I] were obtained in good yields by the reaction of [(tBu3Si)3Ge3]+.TTFPB- (TTFPB- = tetrakis(2,3,5,6-tetrafluorophenyl)borate) with potassium halides (KCl, KBr, or KI) in diethyl ether. The crystal structures of the halogen-substituted cyclotrigermenes reveal a cis-bent Ge=Ge double bond, caused by the introduction of the electronegative halogen atom on the sp3 germanium atom of cyclotrigermene.