The Influence of the growing polymer chain on the catalytic complex in homogeneous ziegler-natta polymerization: Density functional calculations on model systems TiCI2R+ and ZrCl2R+

The influence of the growing chain on the electronic structure of soluble Ziegler-Natta catalysts was investigated through quantum-mechanical calculations for model systems MCI₂R⁺ with M = Ti, Zr and R = C_nH_2n+1 where n = 1–7. The theoretical results show an increase in the energy of the Lowest Unoccupied Molecular Orbital (LUMO) of the cation and a decrease of the transition metal charge in the early stages of polymerization. This behaviour could explain the experimentally observed initial acceleration of the monomer insertion rate as reported in literature for ethylene polymerization with TiCp₂CH₃Cl·AlCl₂CH₃ system.     

Fluorenyl based syndiotactic specific metallocene catalysts structural features,origin of syndiospecificity

The stereochemistry of propylene insertion/propagation reactions with a variety of C_s symmetric fluorenyl- containing single site catalysts is discussed. Our recent results indicate that independent of the chemical composition of the ancillary ligand fragments, or nature of the transition metal, active sites with local C_s symmetry and enantiotopic coordination positions behave syndioselectively in the general context of chain migratory insertion mechanism. Perfect bilateral symmetry neither exists nor is required in these processes. In this context the mechanism of syndiospecific polymerization is revisited by taking into account the structural characteristics and catalytic behavior of the original metallocene based (η⁵-C₅H₄-CMe₂-η⁵-C₁₃H₈) MCl₂/ MAO; M = Zr ( 1 ), Hf ( 2 ) catalyst systems and new syndiotactic specific systems including (η⁵-C₅H₄-CPh2-η5-3,6-di-tBut-C₁₃H₆)ZrCl₂ ( 3 ), η¹,η⁵-(μMe₂Si)(3,6-di-tBut-Flu)(t-ButN)MCl₂/ MAO; M =Ti ( 4 ), Zr ( 5 ) and η¹,η⁵-(μMe₂Si)(2,7-di-tBut-Flu)(t-ButN)MCl₂/ MAO; M = Ti ( 6 ), Zr ( 7 ).     

Direktsynthese von orthometallierten Ketonen des Typs RCO (o-C6H4)Mn(CO)4−nLn (R = Alkyl- und Arylrest,n = 0, 1, 2, L = Ligand)

Direct Synthesis of Orthometallated Ketones of the Type RCO(o-C₆H₄)Mn(CO)_4?nL_n (R = Alkyl and Aryl Groups, n = 0, 1, 2, L = Ligand) The starting materials of the type RMn(CO)_5?nL_n und (C₆H₅)₂ Hg react to the products of the type RCO(o-C₆H₄)Mn(CO)_4?nL_n[n = 0, R = Ch₃, C₂H₅, C₃H₇, C₆H₅,CH₂; R = C₆H₅, n = 1, L = E(C₆H₅)₃, E = P, As, Sb; R = C₆H₅, n = 2, L = P(OR′)₃, R′ = C₆H₅, CH₃, C₂H₅, C₃H₇]. Steps of their complex reaction pathway are proposed. These orthometallated substances have been characterized by means of ¹H-n.m.r., i.r. and u.v. spectroscopic measurements. The determination of the molecular structure of the two compounds RCO(o-C₆H₄)Mn(CO)₃L [R = C₂H₅, L = CO; R = C₆H₅, L = As(C₆H₅)₃] show that both contain a planar heterocyclic five-membered ring of the type .     

Organometallic Niobium and Tantalum Complexes with Primary Phosphine Ligands: Syntheses and Molecular Structures of [Cp*MCl4(PH2R)] (M = Nb,Ta; Cp* = C5Me5;R = But,Ad, Cy,Ph, 2, 4, 6‐Me3C6H2 (Mes))

The reaction of [Cp*MCl₄] (M = Nb, Ta; Cp* = C₅Me₅) with PH₂R in toluene at room temperature gives the primary phosphine complexes [Cp*MCl₄(PH₂R)] [Cp* = C₅Me₅; M = Nb: R = Bu^t ( 1a ), Ad ( 2a ), Cy ( 3a ), Ph ( 4a ), 2, 4, 6‐Me₃C₆H₂ (Mes) ( 5a ); M = Ta: R = Bu^t ( 1b ), Ad ( 2b ), Cy ( 3b ), Ph ( 4b ), Mes ( 5b )] in high yield. 1—5 were characterized spectroscopically (NMR, IR, MS) and by crystal structure determinations. The starting material [Cp*TaCl₄] is monomeric in the solid state, as shown by crystal structure determination.     

Equilibrium phase behavior of aqueous two-phase systems containing 17R4/L64 and citrates

The cloud points (CPs) of the copolymers 17R4 and L64 were first measured, and then the effects of salts ((NH₄)₃C₆H₅O₇, K₃C₆H₅O₇) on 17R4 and L64 were researched. After finishing the work described above, the temperature (278.15, 283.15, and 288.15) K of aqueous two-phase systems was determined, which consist of 17R4-(NH₄)₃C₆H₅O₇, 17R4-K₃C₆H₅O₇, L64-(NH₄)₃C₆H₅O₇, and L64-K₃C₆H₅O₇. Finally, the liquid–liquid equilibrium (LLE) data of binodal curve and the tie line for 17R4-(NH₄)₃C₆H₅O₇ aqueous two- phase systems (ATPSs) 17R4-K₃C₆H₅O₇ ATPSs, L64-(NH₄)₃C₆H₅O₇ ATPSs, and L64-K₃C₆H₅O₇ ATPSs were obtained. Nonlinear fitting of the empirical equation was used for making the diagram. The results showed that the change in the size of the two-phase areas increases with the increase of temperature. The capacity of the salts to induce phase segregation follows the Hofmeister series, that is, K₃C₆H₅O₇?>?(NH₄)₃C₆H₅O₇. In addition, the findings also showed that the phase separation ability of 17R4 is better than that of L64.     

Kinetic study of thermal degradation of di-, chlorodi- and triorganotin(IV) complexes of 2-[(2,6-dichlorodiphenyl)amino]benzene acetate

The organotin complexes of the general formulae R₂SnL₂, R₂SnLCl and R₃SnL where R = C₄H₉, C₆H₅, and C₇H₇ and L = 2-[(2,6-dichlorodiphenyl)amino]benzene acetate, were subjected to thermal decomposition by thermogravimetric analysis (TGA). The decomposition of these compounds occurs mostly in two steps. Kinetic parameters such as order of reaction (n), activation energy (Ea), enthalpy (ΔH^?) and entropy (ΔS^?) of activation were calculated by using the Coats and Horowitz methods. The calculated values are in good agreement with observed TG values that confirm the structural integrity of the complexes.     

Reactions of transition metal σ-acetylide complexes: IX. Preparation and properties of some cycloheptatrienylvinylidene complexes

Addition of [C₇H₇][PF₆] to iron, ruthenium or osmium alkynyl complexes has given eight cationic cycloheptatrienylvinylidene derivatives [M{C C(C₇H₇)R}(L)₂ (η-C₅H₅)][PF₆] (M = Fe, Ru or Os; R = Me, Pr, Ph or C₆F₅; L = PPh₃, L₂ = dppm or dppe; but not all combinations). With Fe(C₂Ph)(CO)₂(η-C₅H₅), only [Fe(CO)₂(thf)(η-C₅H₅)][PF₆] was obtained. Reactions of the new complexes are characterised by loss of the C₇H₇ group. The NMR spectra and FAB mass spectra are described in detail.     

Über Chalkogenolate. 139. Untersuchungen über Dialkylester von Chalkogenokohlensäuren. 2. O,Se- und S,Se-Dialkylmonothiomonoselenocarbonate

On Chalcogenolates. 139. Studies on Dialkyl Esters of Chalcogenocarbonic Acids. 2. O,Se- and S, Se-Dialkyl Monothiomonoselenocarbonates The hitherto unknown esters RSe? CS? OR′, where R = C₂H₅, ⁿC₃H₇ and R′ = C₂H₅, ⁿC₃H₇, are formed by reaction of NaSeR with Cl? CS? OR′ and of RSe? CS? Cl with HOR′. At the first time, the esters RSe? CO? SR′ with R = R′ = C₂H₅, ⁿC₃H₇ have been prepared by reaction between NaSeR and Cl? CO? SR′. The compounds have been characterized by means of diverse spectroscopic methods.     

Transition metal chemistry of phosphorus based ligands. Ruthenium(II) chemistry of bis(phosphino)amines, X2PN(R)PX2 (R=H or Ph, X=Ph; R=Ph, X2=O2C6H4)

Reactions of CpRuCl(PPh₃)₂ with bis(phosphino)amines, X₂PN(R)PX₂ (1 R=H, X=Ph; 2 R=X=Ph; 3 R=Ph, X₂=O₂C₆H₄) give neutral or cationic mononuclear complexes depending on the reaction conditions. Reaction of 1 with CpRuCl(PPh₃)₂ gives one neutral complex, [CpRu(Cl)(η²-Ph₂PN(H)PPh₂)] (4) and two cationic complexes, [CpRu(η²-Ph₂PN(H)PPh₂)(η¹-Ph₂PN(H)PPh₂)]Cl (5) and [CpRu(PPh₃)(η²-Ph₂PN(H)PPh₂)]Cl (6), whereas the reaction of 2 with CpRuCl(PPh₃)₂ leads only to the isolation of cationic complex, [CpRu(PPh₃)(η²-Ph₂PN(Ph)PPh₂)]Cl (7). The catechol derivative 3, in a similar reaction, affords an interesting mononuclear complex [CpRu(PPh₃){η¹-(C₆H₄O₂)PN(Ph)P(O₂H₄C₆)}₂]Cl (8) containing two monodentate bis(phosphino)amine ligands. The structural elucidation of the complexes was carried out by elemental analyses, IR and NMR spectroscopic data.     

Effets electroniques en stereochimie—III : Réduction asymétrique de phénylalkylcétones diversement substituées par des organomagnésiens aromatiques chiraux

The asymmetric reduction of phenylalkylketones p-X-C₆H₄COR (X = H, R = C₂H₅, ¹C₃H₇, ¹C₄H₉ and R = C₂H₅, X = CH₃, OCH₃, Cl, CF₃) with chiral aromatic Grignard reagents p-YC₆H₄-CH(C₂H₅) CH₂MgCl (Y = H, OCH₃, CF₃) give optically active phenylalkylcarbinols. The absolute configuration and the enantiomeric excess depends on electronic effects of substituents carried by the organomagnesium reagent and/or ketone.     

Study on the equilibrium in the MCl2?CH3OH?H2O System (M = Sr2+, Ba2+) at 25°C and 50°C

Studies on the equilibrium in the system MCl₂? CH₃OH? H₂O at 25°C and 50°C (M = Sr²⁺, Ba²⁺) show that the dehydration in the water-methanol systems proceeds stepwise and all possible lower crystal hydrates may be obtained at 25°C depending on the molar ratio for the mixed solvent. The dehydration and solvation processes in the three-component system MCl₂? CH₃OH? H₂O (M = Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺) have been considered in general and compared with those in the bromide system.     

(Cycloheptatrienyl)hydridotungsten Complexes

Carbonyl(cycloheptatrienyl)iodo(phosphorus donor)tungstens ([WI(C₇H₇)(CO)L]; L = P(OMe)₃, 1a ; L = P[O(i-Pr)]₃, 1b ; L = PPh₃, 1c ) were prepared from dicarbonyl(cycloheptatrienyl)iodotungsten ([WI(C₇H₇)(CO)₂)] via a carbonyl-substitution process. Similarly, bromocarbonyl(phosphorus donor)(1,2,4,6-tetramethylcycloheptatrienyl)tungstens ([WBr(Me₄C₇H₃)(CO)L]; L = P(OMe)₃, 6a ; L = P[O(i-Pr)]₃, 6b ; L = PPh₃, 6c ) were obtained from the reaction of bromodicarbonyl(1,2,4,6)-tetramethylcycloheptatrienyl)tungsten ([WBr(Me₄C₇H₃)(CO)₂]; 4 ) with L. The reduction of 1a - c , 4 , and 6a , b with sodiumdihydridobis(2-methoxyethoxy)aluminium in toluene led to stable hydrido complexes [WH(R₄C₇H₃)(CO)L] (R = H, L = P(OMe)₃, 2a ; R = H, L = P[O(i-Pr)]₃, 2b ; R = H, L = PPh₃, 2c ; R = Me, L = P(OMe)₃, 7a ; R = Me, L = P[O(i-Pr)]₃, 7b ; R = Me, L = CO, 7d ). Complexes 2a and 7b were characterized by X-ray structure analyses.     

Vapour-liquid equilibrium data for the systems C2H6 + N2, C2H4 + N2, C3H8 + N2, and C3H6 + N2

High pressure vapour-liquid equilibrium data for the C₂H₆ + N₂, C₂H₄ + N₂, C₃H₈ + N₂, and C₃H₆ + N₂ systems are presented. The data are obtained isothermally in the range from 200 K to 290 K. For each point of data, temperature, pressure and liquid and vapour phase mole fractions are measured.Values for the vapour phase mole fractions are calculated from the obtained pressure, temperature and liquid phase mole fractions. The calculated values are compared with the experimental results, and it is found that the average mean deviation between calculated and experimental mole fractions is less than 0.009 for the systems considered in this work.     

DIORGANOTELLURBIS (ALKYLXANTHOGENATE), TEIL II

Abstract

Diphenyltelluriumbis(alkylxanthates) as well as telluracyclopentane-1,1-bis(alkylxanthates) of the general formula R₂Te(S₂COR')₂ and C_4H8Te(S₂COR′)₂ (R = C₆H₅ and R′ = CH₃, C₂H₅, i-C₃H₇) are obtained by reaction of diphenyltellurium-dichloride or telluracyclopentane-1,-diiodide with sodium-xanthates. The insertion of CS₂ into the corresponding organotelluriumbis-alkoxydes is only successful in the case of the cyclic compound. Diphenyltelluriumbis-alkoxydes react with decomposition. This decomposition in substance and in solution is investigated.

Man erhält Diphenyltellurbis(alkylxanthogenate), sowie Telluracyclopentan-1,1-bis(alkylxanthogenate) der Formel R₂Te(S₂COR′)₂ bzw. C₄H₈Te(S₂COR′)₂ mit R = C₆H₅, R′ = CH₃, C₂H₅, i-C₃H₇, durch Umsetzung von Diphenyltellurdichlorid bzw. Telluracyclopentan-1,1-diiodid mit den entsprechenden Natriumxanthogenaten. Prinzipiell führt auch die Einschiebung von CS₂ in Telluracyclopentan-1,1-bisalkoholate zu den entsprechenden Xanthogenatverbindungen. Bei der Umsetzung von CS₂ mit Diphenyltellurbis(alkoholaten) konnten nur die, für diese Xanthogenatverbindungen charakteristischen Zersetzungsprodukte isoliert werden. In diesem Zusammenhang wurde die thermische und solvensabhängige Zersetzung untersucht.     

KINETIC EFFECTS OF SURFACTANT / POLYMER MIXTURES UPON ACIDIC HYDROLYSIS OF HYDROXAMIC ACIDS

The influence of surfactant / polymer (polyethylene glycol, PEG, mol. wt. = 400) mixtures upon the acidic hydrolysis of two N-substituted hydroxamic acids, i.e., R(CO). N(OH)R' : R = C₆H₅, R' = C₆H₅;4-CH₃C₆H₄ has been studied using cationic (CTAB, TTAB and CPC) and nonionic (TX-100 and Brij-35) surfactants. An inhibitory effect was observed. The results have been explained by Porinoy - Menger model. The critical aggregation concentration and polymer saturation point of the corresponding systems have also been measured with the conductivity and surface tension methods.     

A tandem mass spectrometry study of the gas phase RSC6H5Cr+L (R = H,C6H5; L = arene) and C6H5SSC6H5Cr+ ions

Ion-molecule reactions of chromium containing ions with arylsulfides have been studied in the gas phase and their products have been characterized by tandem mass spectrometry. C₆H₅SH and (C₆H₅)₂S react as typical aromatic compounds and give rise to Cr⁺C₆H₅SR] and RC₆H₅Cr⁺QH₅SR′ [R = H, CH₃, CH(CH₃)₂; R′ = H, C₆H₅] ions. Metastable ion mass spectra of the latter species show that the metal is more strongly bound to diphenylsulfide than to alkylbenzenes. C₆H₅SSC₆H₅ reacts with chromium-containing ions to form only Cr⁺(C₆H₅SSC₆H₅). The decomposition characteristics of this ion and, in particular, the presence of a recovery signal in the neutralization-reionization mass spectrum are in keeping with the formation of a 1,2-dithia[2]cyclophane complex ion, which rearranges into a structurel(s) that contains Cr?S bond(s). No evidence was found for metal atom insertion into S?S, C?S, or S?H bonds.     

Über Chalkogenolate. 140. Untersuchungen über Dialkylester von Chalkogenokohlensäuren. 3. S,Se-Dialkyldithiomonoselenocarbonate Existenzbeweis von Alkylselenoxanthaten [S2C?SeR]−

On Chalcogenolates. 140. Studies on Dialkyl Esters of Chalcogenocarbonic Acids. 3. S,Se-Dialkyl Dithiomonoselenocarbonates. Evidence for the Existence of Alkyl Selenoxanthates [S₂C? SeR]^? The esters RSe? CS? SR′ with R = R′ = C₂H₅, ⁿC₃H₇ as well as with R = ⁿC₃H₇ and R′ = C₂H₅ have been produced by three different methods. The compounds have been characterized by means of electron absorption, infrared, nuclear magnetic resonance (¹H, ¹³C, and ⁷⁷Se), and mass spectra. The unstable alkyl selenoxanthates M[S₂C? SeR], where M = Na, K and R = C₂H₅, ⁿC₃H₇, are formed by reaction of carbon disulfide with the corresponding alkane selenolate. Freshly prepared they react with alkyl iodides R′I to yield RSe? CS? SR′.     

Systematische untersuchungen über das verhalten von organozinn-verbindungen gegenüber flüssigem schwefeldioxid : I. Reaktionen von tetraalkylstannanen mit flüssigem SO2

The SO₂ insertion into teraalkyltin compounds, R₄Sn (R = CH₃, C₂H₅, n-C₃H₇, i-C₃H₇, n-C₄H₉), was investigated depending on the presence of water, reaction temperature and reaction time. According to eqns. (1)–(5), the reaction products R₃SnO₂SR, R₂Sn(O₂SR)₂, (R₃Sn)₂SO₄, R₂SnSO₄ and R₂SnSO₃ were isolated. Especially; at low temperatures (<0°) the following order of decreasing reactivity of the teraorganostannanes toward SO₂ is established: R = C₂H₅ > CH₃ > n-C₃H₇ > n-C₄H₉ > i-C₃H₇     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. 55. Darstellung und Eigenschaften von Niobocenium- und Tantalocenium-Salzen – Kristall- und Molekülstruktur von [(C5H5)2NbCl2][BF4] · CH3CN

Contributions to the Chemistry of Organo Transition Metal Compounds. 55. Preparation and Properties of Niobocenium and Tantalocenium Salts — Crystal and Molecular Structure of [(C₅H₅)₂NbCl₂][BF₄] · CH₃CN Niobocenium and tantalocenium compounds of the type [(C₅H₅)₂MCl₂]X (X = BF₄, PBh₄, PF₆) were synthesized from the metallocene dichlorides and ferricenium salts, [(C₅H₅)₂Fe]X, in methylene dichloride or tetrahydrofuran. With acetonitrile as solvent [(C₅H₅)₂MCl₂]X · CH₃CN complexes are formed. Stable methyl compounds of the type [(C₅H₅)₂M(CH₃)₂]X were obtained, when (C₅H₅)₂Ta(CH₃)₂ is oxidized by means of ferricenium salts. The new complexes were characterized by elemental analysis, i. r., and ¹H n.m.r. spectra. The structure of [(C₅H₅)₂NbCl₂][BF₄] · CH₃CN has been determined by X-ray structure analysis. The compound crystallizes in the orthorhombic space group Cmcm with a = 8.324(12), b = 19.581(13), c = 9,563(8) Å and Z = 4. The coordination geometry of the Nb atom is tetrahedrally.