Phase relationships and some magnetic properties of spinels in the systems M1−xNixCr2S4 where M = Mn,Fe, Co

Phase relationships between spinel and defect NiAs structures in the systems M_1?xNi_xCr₂S₄ (where M = Mn, Fe, Co) were investigated. It was found that the spinel structure is stable between x = 0 and x = 0.3 when M = Mn or Fe. When M = Co the spinel is formed in the region x = 0 to x ～ 0.4. The apparent stabilization of the defect NiAs phase by Ni²⁺ may be related to the strong sixfold site preference of Ni²⁺. Curie temperatures of all three ferrimagnetic systems increases with increasing Ni²⁺ substitution. This is probably due to higher NiS covalency.     

The preparation of bis- and tris-(trimethylsilyl)acetic acid

Contrary to an earlier report, lithiation of tris(trimethylsilyl)methane followed by carbonation does not yield the acid (Me₃Si)₃CCO₂H, (I), if an alkali extraction step is included in the work up; the product is actually the acid (Me₃Si)₂CHCO₂H, (II). The acid (I) can be obtained if the alkali extraction is omitted. Separate experiments have confirmed that (I) is rapidly converted into (II) by aqueous or methanolic base.     

Spectral characterisation of nitroarenes and polycyclic aldehydes, ketones, quinones and amines

Three methods are introduced for the post-chromatographic spectral characterisation of carbonyl and nitro compounds. Most often, elution from the chromatogram is necessary, but sometimes fluorescence spectra can be obtained directly from the chromatograra. The usefulness and sensitivity of the methods have been demonstrated for a variety of nitroarenes and polycyclic aldehydes, ketones, quinones and amines.     

Fluxional behaviour of π-bonded acetylenes

Some cationic five coordinate complexes of formula [Os(CO)(NO)L₂A]PF₆ (L = tertiary phosphine, A = an acetylene) have been prepared by reaction of the appropriate acetylene with [Os(CO)(NO)L₂(acetone)]PF₆; the variable temperature ¹H NMR spectra of some of these indicate that the coordinated π-acetylene undergoes fluxional behaviour.     

Chromatographic detection of scandium

Scandium was readily detected by paper chromatography using methyl acetate as the solvent and quinalizarin for the developer. The reddish-violet color formed with scandium resembled the colers obtained with thorium, titanium, zirconium and the rare earths, but the difference in R_F values gave definite separation of these elements. Positive chromatographs were obtained by using 0.01 ml of solution 0.005M respect to scandium.     

Organomercury compounds XX Reactions of lithium polyfluorobenzenesulphinates with mercuric salts

The lithium polyfluorobenzenesulphinates, Li O₂SR (R = C₆F₅, $\text{p}$-HC₆F₄, $\text{m}$-HC₆F₄, or $\text{o}$-HC₆F₄), and the dilithium tetrafluorobenzenedisulphinates, $\text{p}$- and $\text{o}$-(LiO₂S)₂C₆F₄, have been prepared by reaction of the appropriate polyfluoroaryllithium compounds with sulphur dioxide. All compounds were isolated as hydrates and gave the corresponding $\text{S}$-benzylthiouronium salts on treatment with $\text{S}$-benzylthiouronium chloride. From reactions of the lithium sulphinates with suitable mercuric salts in water, generally at room temperature, the derivatives RHgX (R = C₆F₅, X = Cl, Br, CH₃CO₂, or PhSO₂; R = $\text{p}$-HC₆F₄, X = Cl, Br, or CH₃CO₂; R = $\text{m}$-HC₆F₄, X = Cl or Br; R = $\text{o}$-HC₆F₄, X = Cl), $\text{p}$-(XHg)₂C₆F₄ (X = Cl, Br, or CH₃CO₂), and $\text{o}$-(XHg)₂C₆X₄ (X = Cl or Br) have been prepared. Similarly, the bispolyfluorophenylmercurials R₂Hg (R = C₆F₅, $\text{p}$-HC₆F₄, or $\text{m}$-HC₆F₄) have been prepared from the corresponding lithium sulphinates and either mercuric salts or polyfluorophenylmercuric halides in aqueous $\text{t}$-butanol. A possible mechanism for the sulphur dioxide elimination reactions is discussed.     

The different steric environments of the 5-exo- and 5-endo- substituent for a pair of isomeric tricarbonyl(methoxycyclohexa-1,-diene)irons

A shift reagent has been employed to demonstrate the sterically-hindered environment of the methoxy group in tricarbonyl(5-endo-methoxycyclohexa-1,-diene)iron relative to that of the methoxy group in the 5-exo analogue.     

Synthesis of 5,12-diazadibenz[a,h]anthracene

5, 12-Diazadibenz[a,h]anthracene ( 20 ) was synthesized in 21% overall yield for seven steps. Salient features of the synthesis include the initial, one-step conversion of trans, trans-1,4-bis-(β-nitrovinyl)benzene into 2,2″-dinitro-p-terphenyl by Diels-Alder condensation plus elimination, monocyclization of the derived 2,2″-diformylamino-p-terphenyl to give 8-(2-amino-1-phenyl)-phenanthridine ( 10 ) in the presence of fortified polyphosphoric acid, and accomplishment of a second cyclization step only after reduction of the heteroring in 10 (by means of diisobutyl-aluminum hydride) plus formylation. The 6-methyl and 6,13-dimethyl derivatives of 20 were prepared similarly.