ansa-Metallocene Derivatives : IV. Synthesis and molecular structures of chiral ansa-titanocene derivatives with bridged tetrahydroindenyl ligands

A synthesis for racemic ethylene-bis(4,5,6,7-tetrahydro-1-indenyl)titanium dichloride is described. The molecular structures of this compound, of its meso- isomer and of a binaphtholate complex of the (S,S)-enantiomer have been determined. Cleavage of this binaphtholate complex gives the pure (S,tS)-enentiomer.     

ansa-Metallocene derivatives: VIII. Syntheses and crystal structures of ethylene-bridged titanocene and zirconocene derivatives with permethylated ring ligands

Ethylene-bridged titanocene and zirconocene derivatives with permethylated ring ligands, C₂H₄(C₅(CH₃)₄)₂TiCl₂ and C₂H₄(C₅(CH₃)₄)₂ZrCl₂, have been synthesized and their crystal structures determined.     

The reaction of allene with β-diketonatoiridium(I) complexes: formation and crystal structure of a new bis-β-allylic derivative of iridium(III)

The reaction of allene with (Hfacac)Ir(η-C₈H₁₄)₂ to give a new bis-η-allylic complex of iridium(III) containing an allene tetramer is described; the X-ray structure of this compound is reported.     

Thermal studies on purine complexes. VII. 8-theophylline derivatives and their silver(I) complexes

Four theophylline derivatives: 8-ethyltheophylline (ETH), 8-isopropyltheophylline (IPH), 8-propyltheophylline (PRH), and 8-phenyltheophylline (FTH) have been synthesized and characterized by spectroscopic techniques and thermal analysis. The melting points of these theophylline derivatives increase with the molecular weight, from 263.8°C (ETH) to 384.7°C (FTH). The values of the fusion enthalpy increase in the same order, from 28.4 kJ mol⁻¹ (ETH) to 36.5 kJ mol⁻¹ (FTH).

The interaction of these theophylline derivatives with Ag(I) has been studied by means of spectroscopic techniques, TG, DTG and DSC. In all cases, the pyrolysis of these compounds gave metallic silver.     

Organocobalt complexes IX. The insertion of acetylenes into butenolide complexes; crystal structure of a dicobalt complex with a novel five-carbon bridge

Preparative thin layer chromatography has yielded the first-pure insertion products from acetylenes and butenolide dicobalt hexacarbonyls; the structure of one such product has been determined by X-ray crystallography and a related formulation is suggested for the other isomer formed in comparable amounts.     

Antiferromagnetic complexes involving metalmetal bonds : I. Synthesis and molecular structure of an antiferromagnetic dimer with a CrCr bond

The binuclear complex (C₅H₅)₂Cr₂(S)(SCMe₃)₂ was prepared by refluxing a solution of chromocene and t-butylmercaptane in heptane. The structure of the product was determined by single crystal X-ray diffraction. The chronium atoms are linked by a sulphide bridge (SCr 2.24 Å;, <CrSCr 74.1° and two SCMe₃ bridges (CrS 2.38 Å;, <CrSCr 68.3–69.3°). The two cyclopentadienyl ligands (CC 1.41 Å;, CrC 2.23 Å;) are in apical positions, their ring planes being parallel to each other. The complex is an antiferromagnet (?2J cm^?1) despite the small CrSCr angles and short chromiumchromium distance (2.689 Å;) indicative of strong CrCr bonding.     

Synthesis and structure of the 1,1′-trimethylenebenzene- cyclopentadienyliron cation.

1,1′-Bis(3-phenylpropyl)ferrocene reacts with AlCl₃/Al inheptane to yield 1,1′trimethylenebenzenecyclopentadienyliron hexafluorophosphate (I). The structure of complex I was established by X-ray analysis.     

The crystal structure of copper bromide telluride

The crystal structure of CuBrTe has been determined. The compound is tetragonal with unit cell dimensions a = 16.417Å, c = 4.711Å, Z = 16, and space group I4₁/amd. Three-dimensional counterdiffraction intensity data (MoKα) were refined with full-matrix least-squares to a conventional unweighted R of 0.066. The structure consists of infinite tellurium spirals with bromine tetrahedra interspersed. Two basic types of disordered copper atoms were found. One type is at the center of the bromine tetrahedra and has several possible locations for each atom. The other type of copper lies on two possible sites in a distorted tetrahedral environment with tellurium and two bromine atoms as nearest neighbors.     

Dynamics and structure of some tricarbonylferrole-iron tricarbonyl derivatives

A series of compounds of the formula Fe₂(CO)_6-x(PR₃)_x(R′C₂R″)₂ (x = 0, R′ and R″ = Ph, R′ and R″ = H, R′ = Ph and R″ = H; x = 1, K = Ph or n-Bu, and R′ and R″ = Ph) were studied by ¹³C NMR to observe their solution properties. The tricarbonylferrole unit was found to be static from ?125 to +95° C, while the π-Fe(CO)₃ group appeared to be fluxional over the same temperature range. Definite assignments of the carbonyl carbon and ferrole ring carbon resonances have been made. A low temperature single crystal X-ray study of Fe₂(CO)₅PPh₃(PhC₂Ph)₂ demonstrated that the phosphine ligand was attached to the ferrole iron contrary to previous belief based on chemical evidence.     

The crystal structure of Li2WO4II: A structure related to spinel

Li₂WO₄II, synthesized at 3 kbar and 630°C, has tetragonal symmetry, $\text{I4}{}_1\text{amd}\text{, a = 11.954(2)}$ and c = 8.410(1)Å, Z = 16, D_calc = 5.78 g cm^?3. The structure was determined by countermeasuring 469 independent reflections from a single crystal and was refined up to R = 0.032 by the full-matrix least-squares method. It is based on cubic closest packing of oxygen atoms and is closely related to the β-phase structure of Mg₂SiO₄. W and Li(2) are in octahedral sites and Li(1), in tetrahedral sites. Four Li(1)O₄ tetrahedra form a Li₄O₁₂ group, WO₆ and Li(2)O₆ construct a octahedral double chain along the a axis, and four WO₆ octahedra build a W₄O₁₆ group by sharing their octahedral edges.     

The crystal and molecular structure of bis(triphenylsilicon) carbodiimide

The structure of (Ph₃SiN)₂C has been determined by single crystal X-ray diffraction. The structure was solved by direct methods and refined to R = 0.071 for 593 independent diffractometer data. The crystals are rhombohedral, R$\text{3}$ with a = b = c 18.201(20) Å, α = β = γ = 48.82(2)°, and Z = 4. The three crystallographically independent molecules each have linear SiNCNSi chains lying along the crystallographic threefold axes; in two of the molecules the central carbon atom lies on a centre of symmetry. Principal mean bond lengths and angles are: Si, 1.696(25); SiC, 1.846(20); NC, 1.164(30); CC, 1.387(14) Å; CSi, 108.2(6); and CSiC, 110.8(6)°.     

Single-crystal growth and crystal structure refinement of CuAlO2

Single crystals of the delafossite-type compound CuAlO₂ were grown from Al₂O₃Cu₂O melt by a slow-cooling method from 1200°C. Three types were found in as-grown crystals (single crystals, short-columnar twin crystals with concave angles, and laminar twin crystals). The twinning form is similar to the spinel-type twin. CuAlO₂ is rhombohedral, $\text{R}\text{3}\text{m, a = 2.8604(7), c = 16.953(5)}\text{A}\text{?}$, Z = 3, Dx = 5.12 g/cm³ and Dm = 5.06 g/cm³. The crystal structure of CuAlO₂ was analyzed by means of single-crystal X-ray diffraction with a conventional R value = 0.038. The value of the U₁₁ component of the thermal parameter of Cu⁺ was twice as large as U₃₃.     

The interaction of 1,1,3,3-tetrakis(trifluoromethyl)allene with sodium derivatives of iron and rhenium carbonyl compounds. Synthesis and structure of the σ- and π-complexes

1,1,3,3-Tetrakis(trifluoromethyl)allene reacts with π-C₅H₅Fe(CO)₂- and Re(CO)₅- to give σ-complexes. The iron σ-complex, when refluxed in decalin or exposed to UV radiation, is transformed to the π-allylidene analogue. Structures of the σ-complexes are determined from IR, Raman, ¹⁹F NMR and X-ray spectral data.     

Cobalt(I) and cobalt(III) derivatives from the reactions of phosphine ligands with cobalt(II) salts containing low-coordinating anions

Complexes of the type [Co(CO)_n(P)_5?n]ClO₄, [CoH₂(P)₄]ClO₄, [CoH(P)₅](ClO₄)₂ and [CoHX(F)₄]ClO₄ (P = secondary or tertiary phosphine) have been prepared from Co(ClO₄)₂·6 H₂O and phosphine in isopropyl alcohol.     

Hydrodynamic voltammetry at channel electrodes: Part VII. Current transients at double channel electrodes

Expressions for the transient current at the downstream electrode in response to galvanostatic electrolysis at the upstream electrode in the channel flow cell were derived by applying double Laplace transformation when the electrode reaction at the upstream electrode is kinetically controlled. The ratio of the transient current to the steady state current or the transient collection efficiency was calculated as a function of electrode geometry and θ

, where U_m is the mean flow velocity in the channel cell, D the diffusion coefficient of the electroactive species, b the half height of the channel, x₁ the length of the upstream electrode and t the time elapsed since the beginning of the galvanostatic electrolysis at the upstream electrode. Curves for the transient collection efficiency can be applied to evaluating the amount of adsorption at the upstream electrode when metal at the electrode is anodically dissolved in solution. Digital simulation was carried out. Transient curves, obtained analytically, were in good agreement with those evaluated from the digital simulation. In order to allow one to draw transient curves readily, we derived a simple approximate equation.     

Polysilane derivatives of the transition metals III. Preparations and spectra of manganese and iron derivatives

The preparations of derivatives of Mn(CO)₅, Mn(CO)₄PPh₃ and π-Cp(CO)₂Fe containing the polysilyl ligands (Me₃Si)_nMe_3?nSi— (n = 1–3) are presented. The infrared and proton NMR spectra of the compounds are given and for the Mn(CO)₅ derivatives, force constants are derived and discussed in terms of the σ-donor/π-acceptor properties of the silyl ligands.     

Transition metal methylene complexes : III. Methylene (CH2), a carbonyl analogous ligand; crystal structure of μ-methylenebis(carbonyl-η5-cyclopentadienylrhodium)(Rh—Rh

μ-Carbonylbis(carbonyl-ν⁵-cycopentadienylrhodium)(Rh—Rh) reacts with N-methyl-and N-ethyl-N-nitrosourea in boiling benzene to yield the dinuclear, diamagnetic, neutral rhodium complexes μ-methylene- (A) and μ-ethylidenebis(carbonyl-η⁵-cyclopentadienylrhodium)(Rh—Rh) (B), respectively. Deuterium labelled experiments prove the origin of the metal-stabilized methylene ligand to be the alkyl group of the organic precursor. This new method of preparation of transition metal—methylene complexes may be used as an alternative to the commonly used diazo method; the latter method was shown to work with diazodiethylmalonate and dicarbonyl-η⁵-cyclopentadienylrhodium, the reaction yielding μ-bis(ethoxycarbonyl)methylenebis(carbonyl-η⁵-cyclopentadienylrhodium)(Rh—Rh).Compound A crystallizes in the triclinic system, P$\text{1}$, and with cell constants of a 803.42(5), b 909.98(6), c 938.81(2) pm, α 74.402(3), β81.923(3), and γ 83.685(6)°. The unit cell volume and the calculated density are 651.6 ų and 2.069 g cm^-3, for one molecule in the asymmetric unit. The molecular geometry of μ-CH₂[η⁵-C₅H₅Rh(CO)]₂ was established from 2718 unique reflections collected with a computer-controlled diffractometer and refined to a final R(F) = 0.0379. The molecular parameters derived from the single-crystal X-ray study conform to a remarkable degree with those found for μ-CO[η⁵-C₅H₅Rh(CO)]₂. Thus, the bridging ligands CH₂ and CO seem to be analogous in their effects on the structural characteristics of the molecular framework of the two molecules.     

Rhodium(I) phosphine complexes containing bidentate unsaturated thio ligands: II. Reactions with O2 and H2

The rhodium(I) complexes (Ph₃P)₂Rh[Me₂NC(S)NC(S)NMe₂], (Ph₃P)₂Rh[SC(S)NMe₂] and (Ph₃P)₂Rh[PhNC(S)NMe₂] react with O₂ to give 1/1 dioxygen adducts. In solution, trans-(Ph₃P)₂Rh(O₂)[Me₂NC(S)NC(S)NMe₂], cis- and trans-(Ph₃P)₂Rh(O₂)[SC(S)NMe₂] and cis- and trans-(Ph₃P)₂Rh(O₂)[PhNC(S)NMe₂] are observed. For (Ph₃P)₂Rh(O₂)[PhNC(S)NMe₂], there is a solvent effect on the initial cis—trans ratio and the rate of O=PPh₃ formation. In C₆H₆, O=PPh₃ formation from (Ph₃P)₂Rh(O₂)[PhNC(S)NMe₂] is inhibited by additional PPh₃.The reaction of (Ph₃P)₂Rh[Ph₂PC(S)NPh] with O₂ in the presence of additional PPh₃ gives O=PPh₃ and cis-(Ph₃P)₂Rh(O₂)[Ph₂P(O)C(S)NPh] as the only products. The same complex also can be prepared from (Ph₃P)₂Rh[Ph₂P(O)C(S)NPh] and O₂.Only (Ph₃P)₂Rh[PhNC(S)NMe₂] reacts with H₂ at room temperature to give (Ph₃P)₂RhH₂[PhNC(S)NMe₂], which is a catalyst for cyclohexene hydrogenation.     

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.     

Automatic microanalyzers: VII. Automatic analyzer for rapid microdetermination of sulfur

A commercially available analyzer for determination of sulfur (0.5–100%) in organic and some inorganic compounds is described. It involves combustion of the sample at high temperature (1050 °C) to form SO₂ and SO₃ in a vertical reactor. SO₃ is reduced to SO₂ and nitrogen oxides to N₂ on copper at 850–900 °C. At this temperature the chemical reactions of SO₂ and copper are minimized so that SO₂ is obtained quantitatively in this range.Use of a vertical reactor and an autosampler makes an easy and complete automation of the sulfur determination possible. With this automation, great improvements are noticed in accuracy and precision over manual methods. The average time for a single determination is about 8 min.