Calcium alkoxyalanates : II. Advances in the synthesis

Simple syntheses of calcium alkoxyalanates starting from NaAlH₄, CaCl₂ and alcohols involving evolution of hydrogen and separation of sodium chloride are reported. More complex methods, which allow the preparation of calcium alkoxyllalanates without loss of hydride hydrogen from NaAlH₄, CaCl₂, NaOR and AlX₃ (X = OR, Cl) have also been developed.     

Calcium alkoxyalanates : I. Synthesis and physicochemical characterization

Soluble calcium alkoxyalanates, Ca[AlH_4?n(OR)_n]₂, in which n ranges from 1 to 3, generally complexed with tetrahydrofuran, have been obtained by partial alcoholysis of calcium alanate with various branched aliphatic alcohols and with 2-methoxyethanol in toluene. With a few exceptions X-ray powder diffraction patterns and infrared AlH absorptions indicate that the calcium alkoxyalanates are individual molecular species.     

Darstellung von tetrakis(trimethylsilyl)lithiumalanat

Trimethylchlorosilane reacts with aluminum and lithium in the presence of mercury under formation of tetrakis(trimethylsilyl)lithiumalanate.     

Cleavage by halogens of carboncobalt bonds in organometallic complexes of cobalt(III) : II. Organobis(dimethylglyoximato)cobalt(III) complexes

The reaction between organocobaloximes and ICl in chloroform has been studied. In absence of an excess of added chloride ion the reaction is electrophilic in character; in presence of an excess of chloride ion both oxidative dealkylation and radical attack can occur.     

Thermal studies on oxalate complexes. II. Complexes of iron (III) and chromium (III)

The decomposition of solid K₃[Fe(C₂O₄)₃] · 2 H₂O and K₃[Cr(C₂O₄)₃] · 3 H₂O has been studied using TGA and DSC. After dehydration, the chromium compound was found to decompose by the loss of CO in two steps, the loss of CO₂ and additional CO, and finally the loss of CO₂. The final product appears to be either K₃CrO₃ or the mixed oxides of chromium and potassium. Kinetic parameters and enthalpy data are presented for these reactions. In the case of K₃[Fe(C₂O₄)₃] · 2 H₂O, dehydration is followed by the loss of CO₂ and CO, CO₂ alone, and finally CO. The final product appears to be a basic carbonate of the type K₃[FE(O)₂(CO₃)]. Kinetic and thermal data are presented for most of these decomposition reactions.     

Stability and thermodynamics of La(III)-, Pr(III)-, Nd(III)-, Gd(III)- and Eu(III)-p-nitrobenzaldehyde thiosemicarbazone systems

Three complexes containing bidentate N-2,3-dimethylphenylglycine, (2,3-HDPG), N-2,4-dimethylphenylglycine, (2,4-HDPG) and N-2-ethylphenylglycine, (2-HEPG) acids have been prepared and characterized. These compounds have the general formula Zn(2,3-DPG)₂·2 H₂O, Zn(2,4-DPG)₂ and Zn(2-EPG)₂·2 H₂O, respectively. The structure of the complexes as inferred from their chemistries have been found to be compatible with the infrared spectral data. The thermal behaviour of these complexes has been studied from their TG, DTG and DSC diagrams obtained in a dynamic atmosphere of pure air. Heats of dehydration have been calculated from DSC curves.     

Fluorimetric determination of iron(III) by a kinetic method

A sensitive and relatively interference-free method for the kinetic determination of iron(III) is described. The method is based on the catalytic action of this ion on the autoxidation process of 4,8-diamino-1,5-dihydroxyanthraquinone-2,6-disulfonate (disodium salt), to produce a strong pink fluorescence that increases with time. The reaction is monitored at 585 nm, when excited at 525 nm, and the initial rate method is applied to perform the analytical procedure. The influence of reaction variables and the effect of foreign ions are discussed. Iron(III) contents between 0.1 and 1 μg ml^?1 can be determined with R.S.D. of ± 3.7%.     

Separation of trans-1,2-cyclohexanediaminetetra-acetic acid chelates of bismuth(III), iron(III) and copper(II) by reversed-phase paired-ion chromatography

Trans-1,2-cyclohexanediaminetetra-acetic acid (DCTA) chelates of bismuth(III), iron(III) and copper(II) have been separated by two techniques using reversed-phase paired-ion chromatography. In one, the chelates in aqueous solution were separated within 20 min on a 6.0 × 300 mm ERC-ODS column with 10⁻²M tetrabutylammonium ion (TBA⁺) in methanoi-water mixture (45:55 v/v) as eluent. In the other, the metal ions in aqueous solution were separated within 10 min by direct injection into an ERC-ODS column with 10⁻²M TBA⁺/10⁻³M DCTA in methanoi-water mixture (40:60 v/v) as eluent.     

The formation of cobalt acetylides by direct reaction at cobalt(III)

A new method is described for the preparation of cobalt(III) acetylides, in which monosubstituted alkynes are treated directly with cobalt(III) forms of quadridentate Schiff base compounds in methanol.     

Synthesis and properties of alkyldicyclopentadienyl-vanadium(III) compounds

The compounds Cp₂VR (R = CH₃, C₂H₅, n-C₃H₇, n-C₄H₉, n-C₅H₁₁, CH₂C(CH₃)₃ or CH₂Si(CH₃)₃) have been prepared from Cp₂ VCl and RMgX in n-pentane. The air-sensitive compounds are stable at room temperature, but decompose between 65 and 138°C. The thermal stability decreases in the order R = CH₃ CH₂Si(CH₃)₃ > C₂H₅ > CH₂C(CH₃)₃ > n-C₅H₁₁ > n-C₄H₉ > n-C₃H₇. Compounds with R = i-C₃H₇ or t-C₄H₉ could not be obtained.     

Thermal and X-ray diffraction investigations of some lanthanum(III) and neodymium(III) oxide-alkali persulfate binary systems

Different molar ratios of La₂O₃ or Nd₂O₃:Na₂/K₂S₂O₈ have been prepared, and the results of their TG and DTA investigations, under an atmosphere of static air, are reported. The effects of either La₂O₃ or Nd₂O₃ on the thermal decomposition of the persulfates from ambient to 1050°C, using a derivatograph, have been studied. It has been found that La₂O₃ lowers the initial decomposition temperatures of these alkali persulfates through catalytic activity. Nd₂O₃ shows little or no catalytic effect and therefore it acts as an insulator. Intermediate and final products are identified by X-ray diffraction analysis. The stoichiometric molar ratios of the solid state reactions are 1:3::R₂O₃:M₂S₂O₈. (R = La or Nd. M = Na or K), which give double salts of formulae: NaLa(So₄)₂, KLa(SO₄)₂, NaNd(SO₄)₂, and KNd(SO₄)₂. No sulfates or oxysulfates of lanthanum or neodymium have been identified.     

Darstellung und charkterisierung von pentahalogenomonocarbonylosmaten(III)

By decarbonylation of trans-[OsBr₄(CO)₂]^- and exchange of the pure halogen monocarbonyls [OsX₅(CO)]^2? (X Cl, Br, I) can be prepared and isolated as stable salts with various cations. The complexes are characterized by UV-VIS and vibrational spectra and the observed bands are assigned. The stability and behaviour in solution are comparable with similar hexahalo- or pentahalo-nitrosyl compounds.     

Thermal decomposition of some dihalotetramminecobalt(III) nitrates

The thermal decomposition of some dihalotetramminecobalt(III) nitrates [tetrammire =(NH₃)₄, (NH₃)₂(en), (NH₃)(dien), (en)₂, (pn)₂, (trien), etc.] with different degrees of chelation was studied by various thermoanalytical techniques. A partial oxidation—reduction was observed for these complexes above 200°C which was indicated by a rapid TG mass-loss and a large exothermic DTA peak. A relative order thermal stability is reported.     

Polarographic studies on bipyridine complexes: III. Polarography of tris(2,2′-bipyridine) complexes of chromium(I), chromium(0), vanadium(0), titanium(0) and molybdenum(0)

Polarograms and cyclic voltammograms for tris(2,2′-bipyridine) complexes of V(0), Cr(0), Cr(I), Ti(0) and Mo(0) in N,N-dimethylformamide are reported. The reversible half-wave potentials for the following redox systems in lower oxidation states are determined: Cr(?I)/Cr(?II), Cr(?II)/Cr(?III), V(I)/V(0), V(0)/V(?I), V(?I)/V(?II), V(?II)/V(?III), Ti(0)/Ti(?I), Ti(?I)/Ti(?II), Mo(?I)/Mo(?II) and Mo(?II)/Mo-(?III). On the basis of the half-wave-potential shift caused by the methyl substitution of ligands, it is concluded that each excess electron of the reductant species of the redox systems, V(bipy)₃^?/V(bipy)₃^2?, Cr(bipy)₃/Cr(bipy)₃^?, Cr(bipy)₃^?/Cr(bipy)₃^2? and Cr(bipy)₃^2?/Cr(bipy)₃^3? (bipy=2,2′-bipyridine), occupies a ligand π^*-orbital and that of the V(bipy)₃²⁺/V(bipy)₃⁺ and V(bipy)₃⁺/V(bipy)₃ systems a metal t_2g-orbital. The apparent π-character of the excess electron of the redox systems Cr(bipy)₃⁺/Cr(bipy)₃ and V(bipy)₃/V(bipy)₃^? is discussed. It is pointed out that the relative electron affinities of trisbipyridine complexes can be determined from the half-wave potential data. The lowest π^*-orbitals of V(bipy)₃^?, Cr(bipy)₃ and Fe(bidy)₃²⁺ become higher in this order. This suggests that the electrostatic interaction between a π^*-electron and the residual charge on the central metal ion predominantly accounts for the observed π^*-level shift.     

The thermal degradation of a polyurethane foam containing the flame-retardant tetrakis(2-chloroethyl) ethylenediphosphate using simultaneous thermal analysis-mass spectrometry

Polyurethane foam (PU) samples prepared as an industrial product from a polyether polyol and toluene diisocyanate and containing 6% tetrakis(2-chloroethyl) ethylenediphosphate as flame retardant have been subjected to simultaneous TA-MS (thermogravimetry-differential thermal analysis-derivative thermal analysis-mass spectrometry) in static air until residual char products have been formed. The thermal decomposition and the detection of toxic compounds released from the PU as a function of temperature are described.     

Reactions of metal carbonyl complexes III. Synthesis and reactions of Mn(CO)3(Triphos)X(X = Cl,Br, I)

The halopentacarbonylmanganese(I) complexes, Mn(CO)₅X(X = Cl, Br, I), react with PPh(CH₂CH₂PPh₂)₂(Triphos) to give two isomers of fac-Mn(CO)₃(Triphos)X in which the Triphos ligand is only coordinated to the manganese atom through two of its three phosphorus atoms. The fac-Mn(CO)₃(Triphos)X complexes may be considered as “monodentate ligands” in that the free phosphorus atoms readily displace CO and other groups in a variety of metal carbonyls to give a series of novel bimetallic complexes, e.g. Br(CO)₃Mn(Triphos)Cr(CO)₅ and I(CO)₃Mn(Triphos)Mn(CO)₄I. The reactions of Mn(CO)₂[P(OMe)₃](Triphos)Br with Cr(CO)₅THF and Mn(CO)₃(Triphos)X(X = Br, I) with O₂ (and O₃) to produce Br(CO)₂[P(OMe)₃]Mn(Triphos)Cr(CO)₅ and fac-Mn(CO)₃(Triphos=O)X, respectively, are also described. The IR-active COstretching absorptions exhibited by the new complexes are discussed.     

Spectrophotometric determination of microamounts of gold(III) with propericiazine

Propericiazine is proposed as a new reagent for the spectrophotometric determination of gold(III). The reagent forms an orange-red-colored species with gold(III) instantaneously in 4–8 M phosphoric acid. The orange-red species exhibits maximum absorbance at 511 nm. Beer's law is valid over the concentration range 0.1–7.0 μg/ml. The molar absorptivity is found to be 3.85 × 10⁴ liter mol⁻¹ cm⁻¹. The effects of acidity, time, order of addition of reagents, temperature, reagent concentration, and diverse ions are investigated.     

Mechanisms of the reactions of chloromethanes with trimethylstannylsodium. Synthesis of tetrakis[trimethylstannyl]methane.

The reactions of CCl₄, CHCl₃, and CH₂Cl₂ with trimethylstannylsodium in tetraglyme have been examined. Tetrakis[trimethylst?annyl]methane can be obtained by reaction with CCl₄ in yields of about 40%. Among other products which have been characterized in varying degree are the following: trichloromethyltrimethylstannane, bis[trimethylstannyl]dichloromethane, tris[trimethylstannyl]methane, and hexamethyldistannane, The first step in the reaction leads to the formation of the trichloromethyl anion, and dichlorocarbene has been trapped with 2,3- dimethyl-2-butene. Dichlorobis[trimethylstannyl]methane reacts with Me₃SnNa to form tetrakis[trimethylstannyl]methane in 85% yield. When the reaction was carried out in the presence of $\text{t}$-butyl alcohol the only product formed was bis[trimethylstannyl]methane, indicating carbanionic intermediates. Chloroform yields tetrakis[trimethylstannyl]methane and bis[trimethylstannyl]methane, but no detectable tris[trimethylstannylmethane. Trapping experiemtns with 3-pentanol and 2,3-dimethyl-2-butene indicate the intermediacy of dichloromethyl anion and of dichlorocarbene. Methylene chloride yields bis[trimethylstannyl]methane. No intermediates could be trapped by added alcohol.     

A thermogravimetry/differential thermal analysis,evolved gas analysis and pyrolysis/gas chromatography—mass spectrometry study of tetrakis (diethyldithiocarbamato)tin(IV)

The thermal decomposition of tetrakis(diethyldithiocarbamato)tin(IV) has been studied by TG/DTA, EGA and P/GC-MS techniques. From the P/GC-MS analysis, it is apparent that the denticity of the dithiocarbamate ligand influences the mechanism of decomposition. Initially, the monodentate ligands decompose by a radical mechanism to form tetraethylthiuramdisulphide which decomposes further into carbon disulphide and diethylamine. The intermediate formed, bis(diethydithiocarbamato)tin(II), decomposes in two different ways. The bidentate ligands decompose with the liberation of carbon disulphide and tetraethylthiourea, whereas the monodentate ligands, formed as a result of the high temperatures, decompose to produce S-ethyl N,N-diethyldithiocarbamate and ethylisothiocyanate. The overall thermal decomposition mechenism of tetrakis(diethyldithiocarbamato)tin(IV) is complex and the primary decomposition involved both ionic and radical recombination reactions.     

Synthetic studies of organodi-π-cyclopentadienyl- titanium (III) derivatives

Two synthetic routes to compounds of the type π-Cp₂Ti^IIIR (R=CH₃, CH₂Si(CH₃)₃, C₆F₅) have been investigated: (a) chemical reduction of π-Cp₂Ti^IV(R)Cl by zinc or aluminum metal in tetrahydrofuran, and (b) conventional organometallic syntheses using organo-lithium or -magnesium reagents and [π-Cp₂Ti^IIICl]₂. The preferred route is via an organolithium reagent, since chemical reduction gives a mixture of products. Green, monomeric complexes (R = CH₂Si(CH₃)₃, C₆F₅) were isolated and characterised. From the reaction of π-Cp₂Ti^IVCl₂ and trimethylsilylmethyllithium in a 1/1 ratio, π-CpTi^IV [CH₂Si(CH₃)₃]₃ was obtained. Unlike π-Cp₂Ti^IIIC₆F₅, π-Cp₂Ti^IIICH₂Si(CH₃)₃ does not form a blue complex with molecular nitrogen.