A proton NMR investigation of metalmetal bonding in trimethyltin-aluminium, -gallium, -indium and -thallium organometallic compounds

Proton NMR data for the Group III methyl derivatives, MMe₃ and LiMMe₄ are compared with NMR data for the novel tin—Group III-metal bonded species, Li[Me₃SnMMe₃] (M  Al, Ga, In and Tl) and for Li[(Me₃Sn)_n-TlMe_4?n] (n = 0 to 4), reported here for the first time.The presence of tinmetal bonding in these derivatives is established by the observed tin-across-metal coupling constants and for the thallium derivatives by the additional observation of thallium-across-tin coupling.The variation in the magnitudes of ²J(SnCH), ²J(TlCH), ³J(SnMCH) and ³J(TlSnCH) are reported as a function of M and as a function of the number of Me₃Sn groups bond to thallium in the [(Me₃Sn)_nTIME₄?_n]^?anions. Proposals concerning the factors governing the changes in these coupling constants and the chemical shifts are presented.     

Preparation,structures and reactivity of two new addition compounds of carbodiimides with ditungsten hexa-t-butoxide

The reactions of ditungsten hexa-t-butoxide, W₂(OCMe₃)₆, with dicyclohexylcarbodiimide, C₆H₁₁NCNC₆H₁₁, and diisopropylcarbodiimide, Me₂CHNCNCHMe₂, afford the 1:1 adducts, [W(OCMe₃)₃]₂(μ-C₆H₁₁NCNC₆H₁₁), 1, and [W(OCMe₃)₃]₂(μ-C₃H₇NCNC₃H₇), 2, respectively. These products were each shown by X-ray crystallography to be structurally homologous to the previously reported [W(OCMe₃)₃]₂(μ-CH₃C₆H₄NCNC₆H₄CH₃) and similar to [W(OCMe₃)₃(μ-C₆H₅NCO). It has been shown that the [W(OCMe₃)₃]₂(μ-RNCNR) compounds fail to react with further RNCNR, with PhNCO, PMe₃, LiOCMe₃ or LiOCHMe₂, CO or CO₂, and also that [W(OCMe₃)₃]₂(μ-PhNCO) does not afford any defined product when treated with C₆H₁₁NCNC₆H₁₁. Compounds 1 and 2 were fully characterized by IR and NMR spectroscopy and by X-ray crystallography. Compound 1 crystallizes in space group C2/c with unit cell dimensions a = 13.481(3) Å, b = 18.129(4) Å, c = 18.244(2) Å, β = 97.54(1)°, V = 4420(2) ų, Z = 4. It was refined to R = 0.0375, R_w = 0.0475. Compound 2 crystallizes in space group P2₁/c with unit cell dimensions a = 14.752(2) Å, b = 12.157(3) Å, c = 22.189(3) Å, β = 97.03(2)°, V = 3949(2) ų, Z = 4. The structure was refined to R = 0.053, R_w = 0.059. Each molecule has C₂-symmetry, with two W(OCMe₃) units united by RNCNR bridges across WW distances of 2.490(1) and 2.485(1) Å for 1 and 2, respectively.     

1,2-dimetallacyclo-1,2-hexyne compounds of molybdenum and tungsten

From the reactions between 1,4-dilithiobutane and 1,2-M₂Cl₂(NMe₂)₄ compounds in hydrocarbon solvents, the 1,2-dimetallacyclo-1,2-hexyne compounds M₂(CH₂)₄(NMe₂)₄(MM), where M = Mo and W, have been obtained as yellow—orange, volatile microcrystalline compounds. Spectroscopic data are consistent with expectations based on previous studies of gauche 1,2-M₂R₂(NMe₂)₄ compounds in solution and a structural model based on the observed molecular structure of 1,2-Mo₂Et₂(NMe₂)₄ is presented and compared with the observed molecular structure of Mo₂(CH₂)₄(NMe₂)₄ found in the solid state. Pertinent bond distances (Å) and angles (°) are: Mo—Mo = 2.200(1), Mo—N = 1.96(1) (averaged), Mo—C = 2.165(8) (averaged), Mo—Mo—N = 105(1), Mo—Mo—C = 97(1).     

Solvolytic behaviour and the solubilities of various inorganic compounds, lewis acids and bases in fused monobromo acetic acid solvent system—II

Solubilities and the solvolytic behaviour of various inorganic compounds, Lewis acids and bases in fused monobromoacetic acid at 60 ± 0.5°C are discussed. Ionic compounds are fairly soluble, iodides and thiocyanates being comparatively more soluble than chlorides and bromides. Tetraalkyl ammonium halides are highly soluble in this solvent. Conductometric and spectroscopic studies of various Lewis acids and bases in fused monobromoacetic acid indicate their solvolytic behaviour and their subsequent ionization. The solvolyses products BBr₃·CH₂BrCOOH and SbCl₅·CH₂BrCOOH have been observed to be the strongest Bronsted acids. Auto-ionization of this solvent has been supported by acid/base titrations.     

On the net charges in cyclopentadienyl metal compounds

An attempt was made to estimate the net charges of a number of cyclopentadienyl metal compounds on the basis of ¹⁹F NMR data for p-fluorophenylcyclopentadienyl metal compounds. The investigated compounds can be clearly divided into four groups according to the polarity of metal-cyclopentadienyl bond: covalent compounds (derivatives of Fe, Ru, Os, Rh and Pd) with a net charge on the η-C₅H₅ ring in the range from ?0.19 to ?0.29, the so-called ionic compounds (derivatives of Li, Na and K) with a net charge on the ring ?0.64 ÷ ?0.72, and compounds with an intermediate character of the bond (derivatives of Cu, Mg and T1) with a net charge of ?0.44 ÷ ?0.46; the net charge on the rings of cyclopentadienyl manganese tricarbonyl and -rhenium tricarbonyl is near to zero. When the effective charge on the ring is near ?0.44 the cyclopentadienyl metal compounds are able to dissociate into ions in solution.     

Reactivity of polychlorophenylmercury compounds with 1,10-phenanthroline

The action of 1,10-phenanthroline (phen) on the THF solutions of RHgCl (R = 2,5-C₆H₃Cl₂; 2,3,4? and 2,4,6-C₆H₂Cl₃; 2,3,4,5?, 2,3,4,6?, and 2,3,5,6-C₄HCl₄ and C₆Cl₅) gives RHgCl (phen) when R contains two chlorine substituents in ortho (R = 2,4,6-C₆H₂Cl₃; 2,3,4,6?, and 2,3,5,6-C₆HCl₄ and C₆Cl₅), but the symmetrisation reaction occurs when R = 2,5-C₆H₃Cl₂; 2,3,4-C₆H₂Cl₃ and 2,3,4,5-C₆HCl₄. The action of phen on HgR₂ only gives HgR₂ (phen) when R = 2,3,4,5-C₆HCl₄. Compounds of the type RHgMe do not react with phen. These results indicate that steric citects are as important as the electronegativity of R in the formation of tetracoordinated mercury compounds.     

Resonance induced properties in monothiocarbamates derived from aromatic amines: comparison of the coordination chemistry of indole and indoline monothiocarbamates

The syntheses of two new monothiocarbamate ligands and selected transition element complexes of each are reported. The complexes of indoline-N-carbothioate (intc) prepared are: NiL₂·1.5H₂O, ZnL₂, NiL₂·2py, ZnL₂·2py. The complexes of indole N-carbothioate (iltc) are: NiL′₂, ZnL′₂, Cul′. IR spectral results support a bidentate ligand behavior for both new monothiocarbamates except in ZnL₂·2py. Comparison of the IR spectral features of bis(indolylcarbamoyl)-disulfide with that of coordinated indole-N-carbothioate allowed an assignment of the C-S and C-O vibrational frequencies. Evidence for differences in major resonance contributions to the electronic structures of each new ligand are presented. The crystal structure of the bis(indolylcarbamoyl)disulphide is also presented and a comparison is made to pyrrole-N-carbothioate, another aromatic amine monothiocarbamate. The disulphide crystallizes in the centrosymmetric monoclinic space group P2₁/c with a = 15.64(4)Å, b = 5.228(1)Å, c = 19.271(7)Å, β = 97.20(2)°, V = 1564(1)ų, d(obsd)(calcd) = (1.50)(1.52) for a molecular weight = 356.1 and Z = 4. Diffraction data were collected with a Syntex P$\text{1}\text{-}$ diffractiometer with CuKα radiation. Least squares refinement resulted in R_f = 7.0% for all 1213 non zero reflections have (I)> 3σ(I).     

the 31P NMR chemical shifts of four-, five- and six-coordinate phosphorus(V) compounds

There appears to be a correlation between the ³¹P chemical shift differences between A⁺ and AX (Δ₁), and between A⁺ and AX₂^? (Δ₂), where A⁺ is a phosphonium ion and X is an anionic ligand. This relationship holds for a wide range of substituents on phosphorus, despite the expected changes in hybridisation along the series, and is very useful for predicting the shifts of new or unknown species.     

Molar excess volumes and molar excess enthalpies of methylenebromide + aromatic hydrocarbon mixtures

Molar excess volumes V^e and molar excess enthalpies H^e of binary methylenebromide (i) +benzene. +toluene, and + o^?, + m^? and + p-xylene (j) mixtures have been determined at 298.15 and 308.15 K. The data have been analysed in terms of recent approaches for solutions of nonelectrolytes, and the results suggest that these mixtures are characterised by specific interactions between the components. Self-volume interaction coefficients V_iiV_jj have also been evaluated.     

The reaction of methylborylene with cyclohexene and some other olefinic compounds

Some potential methylborylene-generating systems were investigated, using cyclohexene as the trapping agent. Methylborylene, generated by the system 2C₈K/MeBBr₂, reacts with cyclohexene to yield 2-methyl-2-boratricyclo-[7.4.0.0^3.8]-tridecane (MBTT) Ia. In the course of the work an isomer of MBTT was synthesized along a completely different route and compared with Ia. With the system 2C₈K/MeBBr₂, only cyclic olefins were converted to analogues of MBTT. An acyclic olefin and a conjugated diene yielded only haloboration products. Possible mechanisms leading to the formation of MBTT Ia are discussed.     

Synthesis and some reactions of tris (pentafluorophenyl) antimony compounds

(C₆F₅)₃Sb has been found to react with interhalogens and halo-pseudohalogens, IX(X = Cl, Br, N₃ and NCO), pseudohalogen (SCN), and elemental sulphur to give oxidative addition products (I–VI). (C₆F₅)₃SbS(VI) may also be prepared by the reaction of (C₆F₅)₃SbCl₂ with H₂S. Metathetical reactions of (C₆F₅)₃SbCl₂ with appropriate metallic salts yield covalent pentacoordinate disubstituted products (V, VII–XII) of the general formula, (C₆F₅)₃SbY₂ (Y = NCS, NCO, ?ONCMe₂, ?ONCMePh $\text{?NCO(CH}{}_2\text{)}{}_2\text{C}$O and p-NO₂C₆H₄OCO). Treatment of (C₆F₅)₃SbCl₂ with aqueous NaN₃ gives the binuclear oxo-bridge compound, [(C₆F₅)₃SbOSb(C₆F₅)₃](N₃)₂·(III) and (IV) are also accessible by displacement reaction of (I) or (II) with the corresponding metallic salt. Molecular weight, conductance measurements, and IR spectra on the new organoantimony(V) derivatives have been obtained.Reductive cleavage reactions of (C₆F₅)₃SbS with hexaaryldileads, Ar₆Pb₂(Ar = Phenyl, p-tolyl) produce (C₆F₅)₃Sb and the corresponding bis(triaryllead) sulphide but treatment of (C₆F₅)₃SbX₂(X = NCO, Cl) with Ar₆Pb₂ gave Ar₄Pb and Ar₂PbX₂ together with (C₆F₅)₃Sb.(C₆F₅)₃SbCl₂ and bis(triorganotin)sulphides undergo exchange of anionic groups.     

Thermal decomposition of inorganic and organometallic compounds of tin-I. Triphenyltin hydroxide

The thermal decomposition of triphenyltin hydroxide in the temperature range 25–400°C has been studied. The decomposition products formed at each stage have been isolated and characterised. A decomposition scheme involving a reductive-elimination reaction is proposed. The proportions of this reaction and the accompanying reaction are dependent on the mode of heating.     

Absorption spectra of dysprosium compounds in nonaqueous solutions. Spectral intensity analysis

Absorption spectra of dysprosium compounds were measured in amides and D₂O within the 5500–35000 cm^?1 region and in alcohols within the 7000–34300 cm^?1 region. The oscillator strengths of f-f absorptions bands below 35000 cm^?1 were determined. The intensities of the Dy³⁺ ground state absorption were analyzed according to the Judd-Ofelt theory of forced electric dipole transitions.A good fit to the measurements was obtained with the intensity parameter given in Tables 4–6. The polarizability effect on the intensity of the f-f transition with high value matrix elements U⁽⁴⁾ and U⁽⁶⁾ were considered.     

μ-Peroxodicobalt(III) complexes containing aromatic ligands

A series of new μ-peroxodicobalt(III) complexes have been prepared and characterized. Studies of the chemical and physical properties of these complexes were carried out using IR, electronic and NMR spectroscopy along with conductivity, magnetic susceptibility and thermogravimetric measurements. The complexes [Co₂(dpk·dien)₂ (dpk·H₂O)O₂] (ClO₄)₄·H₂O, [Co₂(dpk)₄(py)₂O₂](ClO₄)₄·4H₂O, [Co₂(dpk·H₂O₄(py)₂O₂] (ClO₄)₄, and [Co₂(dpk)₂(terpy)₂O₂](ClO₄)₄ were prepared by bubbling oxygen through a solution containing Co(NO₃)₂, NaClO₄, and the appropriate ligand mixture. Electronic spectral studies are consistent with the formulation as binuclear peroxo complexes. Thermogravimetric studies reveal the stoichiometric loss of O₂ and H₂O below 100°C. The auxiliary ligands, pyridine (py), diethylenetriamine (dien) and terpyridine (terpy) are lost at higher temperatures. Molar conductance of these complexes is indicative of a 4:1 electrolyte while magnetic susceptibility measurements indicate the diamagnetic character of the above four complexes. Three additional complexes of Co(II) containing di-2-pyridyl ketone (dpk) and terpy were prepared to compare spectral changes upon oxygenation.     

A sample mounting technique for the dynaminc mechanical analysis of cellulose and paper sheets

A sample clamp assembly has been devised for the dynamic mechanical analysis of thin cellulose and paper sheets. The assembly, used with the DuPont 981 DMA, provides an arched sample cross-section to prevent buckling deformation of the sample. The applicability of this technique is demonstrated by measurements on original and thermally-aged newsprints.     

Mechanisms of addition of primary aromatic amines and cyclohexylamine to tricarbonyl(cycloheptatrienyl)tungsten cation

X-substituted anilines (X = H, 2-Me, 4-Me or 2-Cl) and cyclohexylamine are shown to add to the tropylium ring of cation [(η)-C₇H₇)W(CO)₃]⁺ to give the corresponding ring adducts of tricarbonyl(cyclohepta-1,3,5-triene)tungsten. Kinetic studies have demonstrated that the anilines form the triene ring adducts via the rapid pre-equilibrium formation of a π-complex, which rearranges in a rate-determining fashion to form a cationic triene intermediate [(1–6-η-C₆H₇.NH₂R)-W(CO)₃]⁺ (R = C₆H₅, 2-MeC₆H₄, 4-MeC₆H₄ or 2-ClC₆H₄); from this the final product is rapidly formed via amine- or solvent-assisted proton loss. With the aliphatic cyclohexylamine, the cationic triene intermediate is formed directly, followed by competing rate-determining solvent- and amine-assisted proton removal.     

Cyclopalladation compounds of the 2-pyridylhydrazone derivatives of p-substituted acetophenones and acetylthiophenes

Cyclopalladation occurs for 2-pyridylhydrazones(HL) of p-methyl-, p-methoxy-, p-chloro-, and p-nitro-acetophenone, and 3-acetyl- and 2-acetyl-thiophene with lithium tetrahalopalladate to give the complexes [PdXL] (X = Cl and Br) and some iodo complexes are prepared by metathesis of the chloro complexes with lithium iodide. These complexes are characterized spectroscopically. The hydrazones are coordinated to palladium through benzene or thiophene ortho-carbon, hydrazone-nitrogen, and pyridine ring-nitrogen atoms forming fused five-membered chelate rings.     

Phase equilibria for the separation of aromatic and nonaromatic compounds using mixed solvents. Part I. The system n-heptane—toluene—N-methylpyrrolidone/monoethyleneglycol

The solvent combination of N-methylpyrrolidone (NMP) and monoethyleneglycol (MEG) is used in industry for the separation of aromatics and nonaromatics (Arosolvan process).In this paper experimental results obtained for the system n-heptane—toluene—N-methylpyrrolidone/monoethyleneglycol are presented. Liquid—liquid equilibrium compositions were obtained at three different temperatures (50°C, 60°C, 70°C). For each temperature, three different solvent compositions corresponding to weight ratios of NMP/MEG equal to $\text{50}\text{50}$, $\text{62}\text{38}$ and $\text{70}\text{30}$ were considered. The different sets of experimental results obtained are correlated using the NRTL equations.Equilibrium compositions obtained using an industrial solvent mixture (NMP/MEG-$\text{58}\text{42}$) are compared with data based on the use of purified solvents.     

Esca studies on the structure of amorphous addition complexes of tin dichloride with aromatic schiff bases

The ESCA characterization of three similar new amorphous addition complexes of tin dichloride with tetradentate aromatic Schiff bases has been carried out. The results support the previously proposed ionic structure.