A general and efficient synthesis of sulfonylbenzotriazoles from N-chlorobenzotriazole and sulfinic acid salts

One-pot reactions of sulfinic acid salts (produced from organometallic reagents with SO2) with N-chlorobenzotriazole gave the corresponding N-alkane-, N-arene-, and N-heteroenesulfonylbenzotriazoles 3a-j in 41-93% yields. Reagents 3a-j are efficient sulfonylating agents, reacting at 20-80 degrees C with various primary and secondary aliphatic amines to yield the corresponding sulfonamides in 64-100% yields.     

Bifunctional pincer-type organometallics as substrates for organic transformations and as novel building blocks for polymetallic materials

The reactivity of the bifunctionalized ligand NC(Br)N-I 1 [IC(6)H(2)(CH(2)NMe(2))(2)-3,5-Br-4] has been studied as a versatile synthon for organic and/or organometallic synthesis. Chemoselective metalation (M = Pd, Pt, Li) at the C(aryl)-I or C(aryl)-Br bonds was achieved by choosing the appropriate metal precursors. In this way a series of Pt(II) and Pd(II) complexes were prepared that have a second functional group available for further reactions. These Pt(II) and Pd(II) complexes were subjected to a wide range of organic and organometallic reactions, revealing the remarkable stability of their M-C sigma-bond and opening an easy route for the synthesis of mono- and (hetero)bimetallic building blocks. The scope of the chemistry of such building blocks shows that they are good candidates for use in the synthesis of dendrimers, bioorganometallic systems, or polymetallic materials. The X-ray crystal structures of the most representative complexes (2, 3a, 19, 20, and 24) are also reported.     

Flow-injection amperometric determination of oxalate with immobilized oxalate oxidase

Oxalate is immobilized on controlled-pore glass and is used on-line in a glass minicolumn (2.5×25 mm). The hydrogen peroxide formed is detected amperometrically. Oxalate (6×10^?6?9×10^?4 M) is determined in a flowing stream of pH 3.5 citrate (or succinate) buffer. As little as 20 ng (in 40 μl; 5.7×10^?6 M) of oxalate can be detected. Copper inhibition can be removed either by adding EDTA to the carrier stream or incorporating a chelating-resin minicolumn into the flow system prior to the enzyme column.     

Flow-injection determination of sulphite and assay of sulphite oxidase

Sulphite (1–80 × 10^?5 M) in formaldehyde-stabilized solutions is determined by injection into a flowing stream of pH 8.5 phosphate buffer, passing through a mini-column of sulphite oxidase immobilized on controlled-pore glass, with amperometric detection of the hydrogen peroxide produced. Sulphite oxidase (5–100 U l^?) is determined by injection into a flowing stream of formaldehyde-stabilized 2 × 10^?3 M sodium sulphite in pH 8.0 phosphate buffer; hydrogen peroxide is again monitored.     

The dimensions of the alternating polyesteramide 6NT6

The Flory-Williams rotational isomeric state models describing the conformational characteristics of polyesters and polyamides are combined to calculate the dimensions of the alternating polyesteramide (PEA) of the type 6NT6. The calculated ratio of unperturbed dimensions $\text{(〈r}{}^2\text{〉}{}_{\mathrm{o}}\text{/M}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ is $\text{1.03}\text{A}\text{?}\text{/gmole}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ in excellent agreement with the value $\text{1.00}\text{A}\text{?}\text{/gmole}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ recently obtained from an intrinsic viscosity-molecular weight study of PEA.     

Synthesis and characterisation of a series of alkylmagnesium amide and related oxygen-contaminated "alkoxy" compounds

Synthesised either by an unusual tert-butyl metathesis between tert-butyllithium and a n,s-butylmagnesium amide or by reaction of an alkyl Grignard reagent and a sodium amide, five tert-butylmagnesium amides, Bu(t)MgDBA (5)(DBA=dibenzylamide), Bu(t)MgDA (6)(DA=diisopropylamide), Bu(t)MgHMDS (7)(HMDS=1,1,1,3,3,3-hexamethyldisilazide), Bu(t)MgTMP (8)(TMP=2,2,6,6-tetramethylpiperidide) and Bu(t)MgNCy2 (9)(cy=cyclohexyl) have been isolated as crystalline solids. All five amides have been characterised by X-ray crystallography and solution NMR spectroscopic studies. The former studies reveal a common dimeric molecular structure with amido bridges in a planar (MgN)2 ring and terminal Bu(t) ligands on the Mg atoms. Also described is the dodecameric primary amide [Bu(n)MgN(H)Dipp]12 (10a) and its monomeric solvate Bu(n)MgN(H)Dipp.TMEDA (10b)(Dipp=2,6-diisopropylphenyl; TMEDA=N,N,N',N'-tetramethylethylenediamine). The crystal structures of the oxo-insertion products Bu(t)MgOBu(t).THF (11), Bu(t)Mg(mu-OBu(t))(mu-TMP)MgTMP (12) and Mg(OBu(n))HMDS.solv [solv=THF (13a) or Et2O (13b)], made fortuitously during the course of this work, are also presented.     

Some past achievements and future perspectives in main group chemistry

A survey of some recent developments and past achievements in low-valent main group chemistry is presented. Some emerging implications of this area of chemistry in materials science, catalysis and new reagent development are also discussed.     

Dependence of ion hydration on the sign of the ion's charge

The solvation of simple ions in water is studied using molecular dynamics simulations with a polarizable force field. Previous simulations using this potential demonstrated that anions are more favorably solvated in water than cations. The present work is an attempt to explain this result by examining the effects of ions on the surrounding water structure, with particular focus on the first solvation shell and its interactions with the surrounding water. We conclude that while the first solvation shell surrounding cations is frustrated by competition between ion-water and water-water interactions, solvation of anions is compatible with good water-water interactions.     

Catenated polysulfur ligands: the pentasulfides of di-η5-cyclopentadienyl-zirconium(IV) and -hafnium(IV)

The thiols Cp₂M(SH)₂, where M = Ti and Zr, react to form the complexes Cp₂MS₅ when treated with mono- and di-sulfur transfer reagents. Treatment of Cp₂MCl₂ with Li₂S₂ and sulfur gave Cp₂MS₅, M = Ti, Zr and Hf, in better yield. The new Zr and Hf complexes have a six-membered MS₅ ring in a chair conformation similar to the previously observed for M = Ti. Variable temperature NMR studies show that the barriers to MS₅ ring inversion decrease in the order Ti > Hf > Zr.     

Propane fuel cells using phosphoric-acid-doped polybenzimidazole membranes

Propane fuel cells using H(3)PO(4)-doped polybenzimidazole polymer membranes produce low and unsustainable current densities at temperatures up to 250 degrees C under anhydrous conditions. Stable intermediate species blocked the surface of noble metal anode catalysts, and the intermediate species could not react further into desorbable final products. In contrast, when water was introduced by light humidification (S(r) 0.08%) of the propane stream, sustainable and higher current densities were achieved. Water participated in the reaction sequence to form surface-bound hydrocarbon and then oxygen-containing intermediates and thereby generated CO and CO(2) as the only carbon-containing products.