Kinetics of nucleophilic attack on coordinated organic moieties. XVIII. Nucleophilicity of anions towards the tricarbonyl-(η-benzene) manganese (I) cation.

Kinetic results for the addition of OH^? to [Mn(CO)₃(η-C₆H₆)]⁺ (I) in water (eq. 1, X  OH) obey the expression k_obs  k_OH[OH^?], and give a k_OH value of 290 mol^?1 dm³ s^?1 at 20.0°C and ionic strength of 0.25 mol dm^?3. The analogous reaction of NaCN with I in water fits the two-term expression k_obs = k_OH[OH^?] + k_CN[CN^?], and leads to a k_CN value of 0.8 mol^?1 dm³ s^?1 at 20.0°C and ionic strength of 0.25 mol dm^?3. Interestingly, the related reaction (eq. 1, X  N₃) is too rapid to follow by stopped-flow spectrophotometry, indicating the overall rate trend N₃^? » OH^? » CN^?. This unusual nucleophilicity order, unexpected on the basis of both basicity and polarizability, is similar to that previously observed for anion addition to free carbonium ions.     

A novel ring substitution reaction in a cyclopentadienylruthenium phosphine complex

The reaction between hexafluoroacetone and Ru(PPh₃)₂(π-C₅H₅)[σ-C₂(CO₂Me)₂H] affords a $\text{1}\text{1}$ adduct, containing a coordinated ester group and an intramolecular hydrogen bond; formal insertion of (CF₃)₂CO into a CH bond of the cyclopentadienyl group has also occurred.     

Structure et mecanisme de cristallisation des produits obtenus par hyper-trempe dans les systemes BaO·Fe2O3 et SrO·Fe2O3

Splat cooling applications to the BaO·Fe₂O₃ and SrO·Fe₂O₃ systems are described. The complete study of structural and crystallographic properties is given for several compositions in these systems. The mechanism of the new cristallization after vitrification is explained for these phases. New compounds are formed, so the interest of the method is proved for the study of binary diagrams. Application of these compounds may be possible on the basis of their magnetic properties.     

On the existence of bivalent ions in the apatite channels: A new example—Phosphocalcium cyanamido-apatite

A new apatite, phosphocalcium cyanamido-apatite Ca₁₀(PO₄)₆ CN₂ □, is obtained by treatment under low pressure at high temperature (900–1000°C) of a mixture of the corresponding hydroxyapatite and calcium cyanamide. In this apatite, one CN^2?₂ ion associated with a vacancy replaces two hydroxyl ions in the channels. The formation of a cyanamide-containing apatite also occurs by treatment of an A-type carbonated apatite by ammonia at 600–900°C: in the latter case, the reaction seems more difficult and more limited than in the former. The cyanamido apatite is decomposed by heating in air, and it gives rise first to an A-type carbonated apatite, with release of both ammonia and nitrogen oxide and second to hydroxyapatite by hydrolysis of the A-type carbonated apatite.     

Crystal structure of Fe2P2O7

Fe₂P₂O₇ crystallizes in the $\text{C}\text{1}$ space group with lattice parameters a = 6.649(2)Å, b = 8.484(2)Å, c = 4.488(1)Å, α = 90.04°, β = 103.89(3)°, γ = 92.82(3)°, and ?_cal = 3.86 g/cc. It is essentially isostructural with β-Zn₂P₂O₇. As in the Zn compound, the bridging oxygen atom in the P₂O₇ group shows a high anisotropic thermal motion. It appears that the P-O-P bond angle is linear as a result of extensive π bonding with the p orbitals on the bridging oxygen atom. The high thermal motion is vibration of the atom into cavities in the structure.     

New ferromagnetic materials for magnetic recording: The iron carbonitrides

New ferromagnetic materials derived from iron nitride Fe₄N by partial substitution of nitrogen by carbon have been prepared by nitriding the iron oxalate whose thermal decomposition gives a carburating atmosphere. The morphology of the carbonitride crystallites depends on the elaboration conditions of the precursor. The particle shapes have been examined by electron microscopy. The coercive field can be improved by partially replacing iron by tin. For a composition close to Fe₃Fe_0.6Sn_0.4N_0.7C_0.3 the coercive field reaches 600 Oe. The average size of the microcrystallites was determined by X-ray diffractometry. An investigation of the aging of the material has been also carried out.     

Etude,par RMN large bande du proton,d'hydrogénophosphates et -arséniates d'un métal trivalent (Al,Ga) et de sodium

Eleven aluminum-sodium or gallium-sodium hydrogenphosphates or -arsenates and an aluminum hydrogenarsenate have been studied. The preparation and characteristic properties of the new compounds are described. The wide-band proton-NMR powder spectra have been interpreted by shape function calculation. The models used imply two types of magnetic configuration: one with two spins, the other with three spins located at the apexes of an isosceles triangle. The hydrogen distribution between water molecules and OH groups has been determined and the constitution of the salts has thus been deduced. The constitution of the hydroxyhydrogen salts Na₃Al(OH)(HXO₄)(XO₄) (X = P, As) is confirmed, but two compounds previously considered as orthoarsenates probably contain condensed anions as expressed by the formula NaM^IIIH₃As₃O₁₁ · 2H₂O. The method for interpreting NMR spectra is discussed.     

Organotin complexes of 5-arylazo-8-quinolinols

5-Phenylazo-8-quinolinol (LH) forms di/tri-organotin complexes similar to the well-known organotin oxinates, but 5-(2′-carboxyphenylazo)-8-quinolinol (L′HH′) forms three classes, viz., the carboxylate derivatives of the type R₃SnL′H, the quinolinolates of the type R₂Sn(L′SnR^′₃)₂ and R₃SnL′SnR^′₃. The carboxylates, R₃SnL′H, are 5-coordinate complexes similar to other triorganotin arylazobenzoates and the quinolinolates, R₂Sn (L′H′)₂, closely resemble the corresponding organotin oxinates. Unlike the oxinates, R₂Sn(L′H′)₂ type complexes can, be made water soluble by treatment with aqueous NaHCO₃ whereby R₂Sn(L′Na)₂ type complexes are formed. The binuclear complexes of the type R₂Sn(L′SnR^′₃)₂ contain 5- and 6-coordinate organotin groups in the same ligand.     

Preparation and characterization of adducts of silicon tetrafluoride with thiazoles

Stable solid adducts of silicon tetrafluoride with the following thiazoles have been prepared: 2-aminothiazole, 2-amino-5-methylthiazole, 2-amino-6-methylbenzothiazole, 2-amino-7-nitrobenzothiazole and 2,4-dimethylthiazole. These adducts have been charactertsed by chemical and infrared spectral analysis. In all the cases except that of 2,4-dimethylthiazole (SiF₄·2L) the composition is 1:1. Both exocyclic and endocyclic nitrogen atoms are the coordinating centres in all the four cases while only endocyclic participates in coordination in the case of 2,4-dimethylthiazole. No indication has been found for the involvement of sulphur in coordination. Probable structures of these adducts have been proposed in which silicon is hexacoordinate.     

Phases in the Ba3Fe1+xS5 series: The structure of β-Ba9Fe4S15 and its low-temperature α polymorph

The crystal structure of β-Ba₉Fe₄S₁₅ shows that it is a phase in the infinitely adaptive series of compounds Ba₃Fe_1+xS₅, 0 ? x ? 1. The material is synthesized by reacting a slightly sulfur-rich mixture at 900°C in a sealed quartz ampoule. Lattice constants are a = 25.212(3), Å, b = 9.594(1), Å, c = 12.575(1), Å, Pnma, z = 4. Three thousand thirty-three structure amplitudes were refined to R = 0.049. BaS₆ trigonal prisms share triangular faces to form infinite columns; the columns in turn share edges and create nearly hexagonal enclosures. Within these rings are additional Ba and S and tetrahedral interstices are created which can be occupied by Fe. The variation of the Fe occupancy from ring to ring gives rise to phases in which one dimension is an integral multiple of the 8.5-Å repeat observed in one end member of the series, Ba₃FeS₅. The other end member is Ba₃Fe₂S₅. At temperatures below 900°C a polymorphic phase is formed. Its lattice constants are a = b = 9.634(1), Å, c = 34.311(3)Å, $\text{I4}{}_1\text{a}\text{, z = 4}$. One thousand five hundred eighty-three structure amplitudes were refined to R = 0.0483. Trigonal prisms and bisdisphenoids articulate to form a complex three-dimensional structure. Two of the S atoms in the structure have statistical site occupancies.     

Higher isoprenoids—VIII: Diterpenoids from the oleoresin of hardwickia pinnata part 1: hardwickiic acid

The oleoresin from Hardwickia pinnata Roxb. is shown to be a complex blend of sesquiterpenes and diterpenes. (?)-Copaene, (?)-caryophyllene and humulene account for over 90% of the sesquiterpenes present. The diterpenes, which constitute some 60% of the oleoresin, have been found to consist of a series of closely related new diterpenoids of ent-clerodane type. Evidence leading to the elucidation of the absolute stereostructure of the main diterpenoid-hardwickiic acid—is presented.     

SAPO-34分子筛的氮化及在甲醇制烯烃(MTO)中的应用

甲醇制烯烃(Methanol To Olefin,简称MTO)过程提供了一条不依赖石油的合成乙烯和丙烯的途径,这种合成方法可以在较大范围调节产品中乙烯和丙烯的比例,以满足市场的需求.而且甲醇可以由一些含碳的原料,如:煤、石油残渣、天然气等等这些不能直接转化为乙烯和丙烯的物质先制成合成     

Covalent attachment of lysine to commercial restriction endonucleases

In the present work lysine was coupled through a water-soluble carbodiimide to several restriction enzymes. The work was carried out to assess the effects on enzyme activity of attaching a small molecule to the enzyme carboxyl groups, with the intent of using carboxyl groups for subsequent immobilization of restriction enzymes on solid supports. Lysine was coupled to Eco RI, Bam HI, and Bgl I with partial to complete retention of enzyme activity. The commercial enzymes contained a large relative concentration of bovine serum albumin (BSA). Therefore, commercial Eco RI, a sample of electrophoretically pure Eco RI, and some high purity BSA each were separately labeled with³H-lysine and the products separated by dialysis and polyacrylamide gel electrophoresis. For the commercial Eco RI preparation, 0.9 μmol of lysine was attached to each μmole of the enzyme fraction; lysine was attached to the BSA and enzyme fractions in the ratio 2.3. The results agreed reasonably well with the amount coupled to the high purity Eco RI and the high purity BSA. The results suggest that carbodiimide coupling through enzyme carboxylic acid groups may be a useful approach for subsequent immobilization of restriction enzymes on solid supports.     

Glucoamylase covalently coupled to porous glass

Glucoamylase (EC 3.2.1.3) was immobilized to alkylamine porous glass with glutaraldehyde. The choice and pretreatment of carrier and conditions for immobilization have been investigated. The immobilized enzyme contained about 4.0–8.0% protein and its activity was about 1000–1700 U/g. Some characteristics of the immobilized enzyme and the native enzyme have been comparatively investigated. The optimum temperature and the pH stability of the preparation were almost identical to the native one. However, the optimum pH of bound glucoamylase shifted 1.3 pH units toward the alkaline side compared to the native one. The Michaelis constant(K _m ) of bound glucoamylase for soluble starch was about four times higher than that of the native enzyme, whileK _m values for maltose approached those of the native material. At 45‡C the half-life of IMG was 104 days under operational conditions. Alkaline protease, α-amylase, asparaginase, and penicillin acylase were also chemically coupled to porous glass by the same method and high relative activities were obtained.     

Furans in Synthesis. The Preparation of (±)-Lactaral

The Functionalized Grignard reagent $\text{13}$ reacts with allylic chloride $\text{14}$, in the presence of Li₂CuCl₄, to provide lactarol-THP ether $\text{15a}$ which is subsequently converted to (±)-lactaral $\text{5}$ in 72% overall yield from $\text{13}$.     

Free radical substitution reaction on zirconium and hafnium organometallics

Di-t-butyl nitroxide readily substitutes alkyl zirconocenes and hafnocenes, Cp₂MR₂, by a rate-determining displacement of alkyl radicals to give high yields of O-alkyl-N,N-di-t-butylhydroxylamine and Cp₂M(R)ONBu^t₂. A free radical substitution of di-benzylzirconocene by benzenethiyl radicals yields Cp₂Zr(SPh)₂.     

Enthalpies of reaction of bis(triphenylphosphine)(trans-stilbene)platinum(0) with diphenylcyclopropenone and benzocyclobutenedione

Enthalpies, ΔH(1) ?94.8 ± 6.0 and ΔH(6) ?57.1 ± 5.1 kJ mol^?1, of the following reactions have been measured calorimetrically [Pt(trans-stilbene)(PPh₃)₂](s) + dpcp(g) → (PPh₃)₂Pt(dpcb)(s) + trans-stilbene(g) (1) [Pt(trans-stilbene)(PPh₃)₂](s) + bcbd(g) → (PPh₃)₂Pt(bcpd)(s) + trans-stilbene (g) (6) where dpcp is diphenylcyclopropenone, (PPh₃)₂Pt(dpcb) is (1,1-bistriphenylphosphine)platinadiphenylcyclobutenone, (PPh₃)₂$\text{PtC(Ph)C(Ph)C}$O, bcbd is benzocyclobutene-1,2-dione and (PPh₃)₂Pt(bcpd) is (1,1-bistriphenylphosphine)platinabenzocyclopentanedione,

. It is concluded that the five-membered platinacyclo ring system in (PPh₃)₂Pt(dpcb) is not heavily strained.     

Optisch aktive übergangsmetall-komplexe: LXXXIII. Konfigurationsstabile tetraedrische NiNi′CC′-cluster

The reaction of Ni(C₅H₅)₂ and Ni(C₅H₄COOCH₃)₂ with the acetylene (?)-(R)-C₆H₅CCCONHCH(CH₃)(C₆H₅)(C₆H₅), “CC′”, yields tetrahedral Ni₂C₂ clusters. Besides the compounds with two identical Ni corners (Ni₂CC′ types) also compounds with two different Ni corners (NiNi′CC′ types) are formed. These consist of two diastereomers which, for a given (R)-configuration in the acid amide substituent, differ only in the cluster chirality. They are separated chromatographically and turn out to be configurationally stable with respect to a change of the cluster chirality.