Catalysis by heteropolyacid—VII. catalytic oxidation of cyclohexanol by dodecamolybdate

In the oxidation of cyclohexanol to cyclohexanone and the further oxidation to adipic acid, a dodecamolybdo-heteropolyanion (HPA) functions catalytically in the presence of aqueous hydrogen peroxide, whereas the HPA without hydrogen peroxide reacts only stoichiometrically. Air- or oxygen-passing through the refluxing system of cyclohexanone and the HPA in the presence of active charcoal, without hydrogen peroxide, has also promoted the oxidation catalytically. Since both hydrogen peroxide and aeration in the presence of active charcoal convert the reduced-form (blue) of the HPA produced by the oxidation of substrate to the oxidized-form (yellow), they play a role as a promoter or a reoxidizing reagent for the oxidation by the HPA. The reoxidizing effect of the aqueous hydrogen peroxide is much the more effective.     

The preparation and electrochemistry of manganese(II) complexes of an unsaturated pentadentate macrocyclic ligand

The preparation of a series of six and seven coordinate manganese(II) complexes [Mn^(II)(L)X]⁺, and [Mn^(II)(L)X₂]^2? (X = halide, water, triphenylphosphine oxide, imidazole, 1-methyl imidazole and pyridine) incorporating the pentadentate planar macrocylic ligand L is described. Cyclic voltammetry of these complexes in acetonitrile each shows a reversible one-electron reduction wave near - 1.4 V vs a Ag/AgNO₃ reference electrode. Quantitative reduction of these complexes by controlled potential electrolysis at a platinum gauze at - 1.4 V yields the corresponding one-electron reduction products which have been shown by ESR spectroscopy to be manganese(II)-ligand radical species, the electron being thought to reside on the di-imino pyridine moiety of the macrocyclic ligand. No metal reduced species could be isolated even in the presence of π-acceptor ligands such as CO or phosphines.     

Thermal decomposition of anionic organoaluminum compounds : V. The preparation and crystal structure of the (isopropylideneamino)dimethylaluminum dimer

The thermolysis of K[Al₂(CH₃)₆SCN] at 120° leads to the formation of [(CH₃)₂AlNC(CH₃)₂]₂. Verification of the dimeric configuration of (isopropylidenamino)dimethylaluminum has been obtained from three-dimensional X-ray data measured by counter methods. [(CH₃)₂AlNC(CH₃)₂]₂ crystallizes in the triclinic space group P$\text{1}$ with cell dimensions a 7.027(4), b 7.760(4), c 8.583(4) Å, α 115.70(5)°, β 105.72(5)°, γ 92.38(5)°, and ?_calc 0.94 g/cm³ for Z = 1. Leastsquares refinement gave a final conventional R value of 0.058 for 1230 independent reflections. Proposed structures of the parent 2/1 complex, as well as mechanisms for the formation of (isopropylidenamino)dimethylaluminum are discussed.     

A new synthetic procedure for the preparation of pyridinium tetrafluoroborate and hexafluorosilicate

Pyridinium tetrafluoroborate (C₅H₅NHBF₄) and pyridinium hexafluorosilicate [(C₅H₅NH)₂SiF₆] have been prepared in good yields and high purity by the reaction of pyridinium poly(hydrogen fluoride) with oxides and acids of boron and silicon respectively. The salts have been characterised by melting points, IR, ¹H and ¹⁹F NMR spectroscopy and chemical analysis.     

Metal π-allyl chemistry III. The preparation of π-allylpalladium complexes from palladium(II) salts

A number of routes for the preparation of π-allylpalladium complexes from palladium(II) salts were investigated with a view to obtaining a quantitative yield. Quantitative yields were obtained rapidly when a stream of ethylene was passed through an aqueous solution of Na₂PdCl₄ and the allylic chloride, and more slowly on vigorously shaking an aqueous solution of Na₂PdCl₄ with a 3-fold excess of allyl chloride.Spectroscopic evidence is presented to confirm that the first stage of the reaction of allylic compounds with palladium(II) salts involves the formation of an olefinic complex. It is found that such palladium(II)olefin complexes of CH₂CHCH₂X are very much less susceptible to nucleophilic attack when X = Cl than when X = C₅H₁₁, OH or OAc, which are all attacked rapidly by nucleophilic solvents, such as methanol, with deposition of palladium metal.     

The preparation and coordination chemistry of 2,2′:6′,2″-terpyridine macrocycles—1

A range of 6,6″-disubstituted derivatives of 2,2′: 6,2″-terpyridine have been prepared with the intention of forming macrocycles incorporating the 2,2′: 6′,2$\text{-}\text{?}$terpyridyl moiety. A high yield route to 6,6″-bis(methylhydrazino-4′-phenyl-2,2′:6′,2″-terpyridine is described, and a number of complexes of this novel pentadentate ligand have been prepared.     

ESR studies on the preparation of the sulphite radical anion,SO3−., in aqueous solution

The sulphite radical anion, SO₃^?., was generated from the redox reactions between the bisulphite ion, HSO₃^?, and transition-metal i     

Ligand promoted reductive elimination from Zr(IV). The preparation of zirconacycles from alkylzirconium(IV) hydrides and alkynes

Alkynes induce reductive elimination of alkane from Cp₂Zr(H)(R); zirconacyclopentadienes are formed as well.     

The preparation and crystal structure of bis(bis(diphenyl-phosphino)ethane)carbonylformylosmium(II) hexafluoroantimonatedichloromethane (1/1)

Reaction of trans[Os(CO)₂(dppe)₂]²⁺ with [KHB(OPrⁱ)₃] gives the formyl complex trans[Os(CHO)(CO)(dppe)₂][SbF₆] which is thermally very stable; the crystal structure shows it to have trans stereochemistry and a long Os-C bond.     

Solid state properties and catalytic behavior of the α- and β-vanadium bronzes

Decomposition of isopropanol (IPA) on V₂O₅, Li_0.02V₂O₅, Na_0.02V₂O₅, Na_0.06V₂O₅, Li_0.33V₂O₅, and Na_0.33V₂O₅ has been studied in the temperature range 186–300°C. The first four catalysts (α-phase) show predominately dehydration, whereas the last two (β-phase) have comparable dehydration and dehydrogenation activity. Dehydration activity increases with alkali metal concentration within the α-phase, but falls sharply on the β-phase catalysts. This difference is attributed to the different rate determining steps for the reaction on the α- and β-phase catalysts. X-ray and ir spectral data show that the β-phase catalysts are much more stable than the α-phase. A mechanism for the dehydration of IPA based on the electrical resistivity, ESR spectra, and kinetic data has been proposed.     

The preparation and X-ray crystal and molecular structure of (α,1,2-η-6-methylbenzyl) bis(triphenylphosphine)rhodium(I)

Reaction of [RhCl(PPh₃)₃] with [o-MeC₆H₄CH₂MgBr] affords high yields of the non-fluxional complex, [Rh(CH₂C₆H₄Me)(PPh₃)₂] which has been shown crystallographically to contain a 1-3-η-benzyl group bound through the phenyl carbon atom that is not substituted with the methyl group. Crystals of this compound are triclinic, space group P$\text{1}$, with a = 10.561(6). b = 17.705(3), c = 10.934(4) Å, α = 80.69(3), β = 116.86(4), γ = 102.30(4)° and Z = 2. The structure was solved via the heavy-atom method and refined to R = 0.032 using 5379 diffractometer data with I > 1.56(I). Attempts to prepare π-bonded xylylene complexes from this compound by reaction with base have been unsuccessful, but protonation followed by recrystallisation from acetone gives [Rh{(CH₃)₂CO}₂(PPh₃)₂]BF₄.     

Enamine chemistry—XXII: The preparation of 4-acylaminopent-3-en-2-ones and the corresponding enamino-thiones

Acylation of 4-aminopcnl-3-en-2-one, 5, with different acid chlorides, RCOCl(R = Me, Me₂CH, Me₃C, C₆H₅, CICH₂) gives only N-acylated products, 6, in high yields. The N-acylated enaminones, 5, are shown only to exist m the Z-s-Z form in solution. The UV spectra of 6 are discussed and an additional increment to the Dabrowski-Table²¹ is given. The reaction of 6 with 2,4-bis(4-methoxyphenyl)-1,2,3,4-dithiadiphosphetane 2,4-disulfide, 2, at room temperature in DME gives the corresponding enamino-thiones, 7, in good yields. The ¹H and ¹³C NMR spectra of 6 and 7 are discussed.     

Some comments on the mechanism of the preparation of (Et4N)2B10H10 by thermolysis of Et4NBH4

The volatile intermediate Et₃NBH₃ was isolated during the thermolysis of Et₄NBH₄ at 185°C for 16 hr under dynamic vacuum. The rate of decomposition of Et₄NBH₄ was studied. Separate thermolyses of Et₄NBH₄ (or Et₃NBH₃) with closo B₉H₉^2?nido B₉H^?₁₂, or arachno B₉H₁₄^? did not produce B₁₀H₁₀^2? as the major product. These results are inconsistent with the “build-up” mechanism previously proposed for the thermolytic convertion of BH ₄^? to B₁₀H₁₀^2? and a new mechanism is required.     

The kinetics of the oxidation of iodide and thiocyanate ions by 12-tungstocobaltate(III)

The rates and mechanism of the reaction of 12-tungstocobaltate(III) anion with thiocyanate and iodide ions have been examined in aqueous acidic solution and constant ionic strength I = 1.00M (LiClO₄). The reactions follow second-order kinetics, i.e. first-order in both the oxidant and the reductant and the rate constants are found to be independent of hydrogen ions in the range [H⁺] = 0.10–1.00M. Outer-sphere mechanism is postulated for the systems based on the relative inertness of the oxidant and linear free energy relations are employed in demonstrating that in the reaction involving thiocyanate ion, the rate determining step is the diffusion apart of the product while the corresponding step in the iodide reaction is the electron transfer. The latter reaction is also catalysed by both bromide and chloride ions and this is rationalised in terms of possible stabilization of atomic iodine as product by these halide ions.     

The study of molecular motions in substituted ferrocenes by means of NMR spectroscopy

The proton magnetic resonance spectra for ferrocene derivatives have been investigated in the solid state at a frequency of 27.5 MHz and at temperatures within the range 4.2–300 K. Evidence for re-orientation in various substituent groups and cyclopentadienyl rings has been deduced on the basis of the temperature dependence of the second moment of the PMR lines. The experimentally observed decrease in the second moment has been compared with the calculated contributions of different molecular groups to the second moment thus enabling an identification of these groups. In computing the second moment, account has been taken of both intra- and intermolecular dipole-dipole interactions. It is shown that the introduction of substituents into some ferrocene rings affects the magnitude of the re-orientation energy for both the substituted and unsubstituted rings. The change of the re-orientation energy of the substituted and unsubstituted rings in substituted ferrocenes with the structure and electronic properties of the substituents is discussed.     

A new method for the preparation of Ru(IV) in non-complexing acid medium: Evidence for tetrameric Ru(IV)

A new method for the preparation of Ru(IV) in acid solutions is described. This method, avoiding the preparation of the highly reactive RuO₄, is based on the stoichiometric oxidation of Br^? ion of K₂RuBr₆ by BrO₃^? ion. Easy to control and reproducible the process leads to solutions of a well-known composition consisting of the tetrameric Ru(IV) ion.     

Syntheses of N-silylformamidines by the hydrosilylation of carbodiimides

The hydrosilylation of carbodiimides was found to proceed at higher temperatures in the presence of catalytic amounts of palladium chloride or tris-(triphenylphosphine)chlororhodium to afford N-silylformamidines in high yield. These were found to be good precursors to formamidines and N-acetyl-formamidines.     

The extraction of molybdenum(VI) from perchloric acid solution by tri-n-butyl phosphate

The extraction of molybdenum(VI) by tri-n-butyl phosphate (TBP) from 1 M NaClO₄ medium has been investigated as a function of molybdenum concen