Tetraalkyl titanium and zirconium metal chloride catalyst systems for ethylene polymerization

Coordination polymerization of olefins has become an industrially important, yet still poorly understood enterprise. The ethylene polymerization activity of (neophyl)_nZrCl_4-n shows a twentyfold increase from n = 4 to n = 3 and a further tenfold increase to n = 2. The heterogeneous MR₄/TiCl₄ catalysts (M = Ti, R = benzyl; M = Zr, R = benzyl, neophyl) have been developed. To explore the breadth of extendability, other metal chlorides (main group and transition metal) were substituted for TiCl₄. Indeed, excess AlCl₃ or MgCl₂ and the MR₄ compounds also produced ethylene polymerization catalysts. The inactivity of corresponding (neophyl)₄Ti systems is attributed to sterics. The abovementioned catalysts highlight the necessity of alkyl and chloride ligands at the transition metal catalyst centers.     

Reaction of Nitrogen(I) Oxide with Nitrogen-fixing Systems on the Basis of Lithium,Chlorotrimethylsilane, and Transition Metal Compounds

Reaction of nitrogen(I) oxide with nitrogen-fixing systems Li/Me₃SiCl/MCl _n (MCl _4n = CrCl₃, CoCl₂, Cp₂TiCl₂, FeCl₃, CuCl₂). In these systems nitrogen(I) oxide, molecular nitrogen, and air nitrogen undergo reductive silylation to tris(trimethylsilyl)amine. The efficiency of the process was estimated by the molar ratio of the tris(trimethylsilyl)amine formed to metal chloride MCl _n n. The reaction of N₂O with the nitrogen-fixing systems including CoCl₂ and Cp₂TiCl₂ is not exhausted by the reduction of the former to molecular nitrogen and its subsequent fixation by transition metal complexes.     

Tin(IV), titanium(IV) and vanadium(IV) chloride complexes with 2-aminobenzimidazole and 2(2′-aminophenyl) benzimidazole

Summary 2-Aminobenzimidazole (abi) and 2(2-aminophenyl)benzimidazole (apbi) react with tin, titanium and vanadium tetrachlorides to yield complexes of formulae: [MCl₄(abi)](M=Sn or Ti), [TiCl₄(abi)₂], [VCl₃(abi-H)] ((abi-H) being the deprotonated ligand) and [MCl₄(apbi)] (M=Sn, Ti or V).Abi is monodentate, with the metal in a pseudooctahedral environment, so that a dimeric structure is proposed for [SnCl₄(abi)] and [TiCl₄(abi-], monomeric for [TiCl₄(abi)₂] and polymeric for [VCl₃(abi-H)]. Apbi acts as a bidentate ligand in all complexes showing a hexacoordinated environment for the metal.     

A reality check on using NaAlH4 as a hydrogen storage material

Sodium aluminum hydride or sodium alanate (NaAlH₄) has been considered as a potential material for hydrogen storage. Although its theoretical hydrogen storage capacity is 5.5 wt.% at 250 °C, the material still has its drawback in the regeneration issue. With the use of certain catalysts, the regeneration problem can somewhat be alleviated with added benefits in the decrease in the hydrogen decomposition temperature and the increase in the decomposition rate. This work summarizes what we have learned from the decomposition of NaAlH₄ with/without catalysts and co-dopants. The decomposition was carried out using a thermovolumetric apparatus. For the tested catalysts—HfCl₄, VCl₃, TiO₂, TiCl₃, and Ti—the decomposition temperature of the hydride decreases; however, they affect the temperature in the subsequent cycles differently and TiO₂ appears to have the most positive effect on the temperature. Sample segregation and the morphological change are postulated to hinder the reversibility of the hydride. To prevent the problems, co-dopants—activated carbon, graphite, and MCM-41—were loaded. Results show that the hydrogen reabsorption capacity of HfCl₄- and TiO₂-doped NaAlH₄ added with the co-dopants increases 10–50% compared with that without a co-dopant, and graphite is the best co-dopant in terms of reabsorption capacity. In addition, the decomposition temperature in the subsequent cycles of the co-dopant doped samples decreases about 10–15 °C as compared to the sample without a co-dopant. Porosity and large surface area of the co-dopant may decrease the segregation of bulk aluminum after the desorption and improve hydrogen diffusion in/out bulk of desorbed/reabsorbed samples.     

Syntheses,characterization and adduct formation of chloride-2,4,6-trimethylphenoxide derivatives of titanium and zirconium

Chloride phenoxides of type MCl_4-n(OAr′)_n (where M = Ti or Zr; n = 1, 2 or 3) have been prepared by the interaction of the metal chlorides with 2,4,6-trimethylphenol (Ar′OH). The mixed chloride phenoxides showed considerable reactivity as Lewis acids towards bases, resulting in addition complexes of general formula MCl_4-n(OAr′)_nL₂ (where L = primary or tertiary aromatic amines, or oxygen- or phosphorus-containing bases). These complexes have been characterized by IR and the ¹H NMR studies, conductivity measurements, molecular weight measurements (in the case of soluble products), thermogravimetric and mass spectral studies.     

Polymer-supported Ziegler–Natta catalyst for the polymerization of isoprene

A polymer-supported Ziegler–Natta catalyst, polystyrene-TiCl₄AlEt₂Cl (PS–TiCl₄AlEt₂Cl), was synthesized by reaction of polystyrene–TiCl₄ complex (PS–TiCl₄) with AlEt₂Cl. This catalyst showed the same, or lightly greater catalytic activity to the unsupported Ziegler–Natta catalyst for polymerization of isoprene. It also has much greater storability, and can be reused and regenerated. Its overall catalytic yield for isoprene polymerization is ca. 20 kg polyisoprene/gTi. The polymerization rate depends on catalyst titanium concentration, mole ratio of Al/Ti, monomer concentration, and temperature. The kinetic equation of this polymerization is: R_p = k[M]^0.30[Ti]^0.41[Al]^1.28, and the apparent activation energy ΔE_act = 14.5 kJ/Mol, and the frequency factor A_p = 33 L/(mol s). The mechanism of the isoprene polymerization catalyzed by the polymer-supported catalyst is also described. © 1993 John Wiley & Sons, Inc.     

Tandem mass spectrometry of peptides. Relationship between translational energy loss and fragment ion mass

Incident ion energy E₁ and collision gas pressure have been adjusted so as to obtain a satisfactory tandem mass spectrum of the m/z 1882 ion formed from valme-gramicidin A (relative molecular mass 1881). Translational energy losses ΔE have been determined (at E_i = 14.8 keV) from the precise positions of a large number of fragment ion peaks in the spectrum. The variation in ΔE for different fragment ions is great and the magnitudes of ΔE are large (being commonly of the order of 10² eV). It is shown how very large energy losses ΔE can arise, if the parent ion decomposes to a small fragment ion which itself collides and decomposes further. Implications of the dependence of ΔE upon fragment ion mass for the scan laws of four-sector instruments are discussed briefly.     

A Tunable Trifluoromethyliodonium Reagent

Four complexes of MCl₄ (M=Ti, Zr, Hf) with the hypervalent trifluoromethyl iodine reagent trifluoromethyl‐1,3‐dihydro‐3,3‐dimethyl‐1,2‐benziodoxole ( 1 ,=L) are described. With TiCl₄, an I?O bond cleavage occurs, leading to the formation of the trifluoromethyliodonium alcoholate complexes [Ti₂Cl₆(L)₄]Cl₂ ( 2 a ) and Ti₂Cl₈(L) ( 2 b ). Reactions with ZrCl₄ and HfCl₄ form the complexes ZrCl₄(L)₂ ( 3 ) and HfCl₄(L)₂ ( 4 ), respectively, wherein the original I?O bond is retained and elongated compared to that in free 1 . Therefore, the reactivity of 1 can be easily and practically fine‐tuned by addition of different metal chlorides, following the order ZrCl₄/HfCl₄<TiCl₄<2 TiCl₄. Complexes 2 a , 3 , and 4 are remarkably bench‐stable forms of activated reagent 1 , while 2 b is readily accessible in situ. 2 a and 2 b represent the first “real” trifluoromethyliodonium reagents derived from iodanes, that is, with the I?O bond being completely cleaved. The new complexes were shown to be useful for the trifluoromethylation of para‐toluenesulfonate under aprotic conditions.     

Die Kristallstrukturen von PPh4[MCl5(NCMe)] · MeCN (M = Ti,Zr), zwei Modifikationen von PPh4[TiCl5(NCMe)] und von cis‐TiCl4(NCMe)2 · MeCN

The Crystal Structures of PPh₄[MCl₅(NCMe)] · MeCN (M = Ti, Zr), two Modifications of PPh₄[TiCl₅(NCMe)] and of cis ‐TiCl₄(NCMe)₂ · MeCN The title compounds were obtained by reactions of TiCl₄ or ZrCl₄, respectively, with PPh₄Cl and acetonitrile in the presence of S₂Cl₂. PPh₄[TiCl₅(NCMe)] · MeCN is unstable and emanates the incorporated acetonitrile. PPh₄[TiCl₅(NCMe)] forms the two modifications aP114 and mP228, the latter being more stable. The crystal structures were determined by X‐ray diffraction. Triclinic PPh₄[TiCl₅(NCMe)]‐(aP114) crystallizes in a distorted variety at the tetragonal AsPh₄[RuNCl₄] type, i. e. with PPh₄⁺ ions that are piled to columns in the c direction; the [TiCl₅(NCMe)]^– ions are tilted vs. this direction and thus cause the symmetry reduction from P4/n to P1. PPh₄[TiCl₅(NCMe)] · MeCN and PPh₄[ZrCl₅(NCMe)] · MeCN also have the same packing principle as in AsPh₄[RuNCl₄] with a symmetry reduction from P4/n to P112₁/n and a doubled c axis. Instead, PPh₄[TiCl₅(NCMe)]‐(mP228) has a packing with (PPh₄⁺)₂ pairs. Orthorhombic TiCl₄(NCMe)₂ · MeCN contains molecules having two acetonitrile ligands attached to the Ti atom in a cis configuration.     

Gasförmige Komplexe von Trichloriden,Tetrachloriden und Pentachloriden mit Aluminiumchlorid

Gaseous Complexes of Trichlorides, Tetrachlorides, and Pentachlorides with Aluminium Chloride The equilibria have been determined with the solid chlorides TiCl₃, VCl₃, ScCl₃, NdCl₃, ZrCl₄, TaCl₅, (NbCl₅) (double cells which contain AlCl₃ and MCl_x respectively; mass spectrometer). The complexes contain 1 AlCl₃/MCl_x. ZrAl₂Cl₁₀ molecules also have been observed. With MoCl₃ and WCl₆ AlCl₃ complexes could not be found. The ΔHº and ΔSº values have been discussed in connection with literature data. Complexes containing more as 1 AlCl₃/LnCl₃ (Ln ? Nd, Sm, Gd) also are included in the discussion.     

Thermodynamische und strukturelle Untersuchungen an den Verbindungen der Systeme KCl/MCl2 (M  Ca,Cd, Co,Ni)

Thermodynamic and Structural Investigations on Compounds of the Systems KCl/Mcl₂ (M=Ca, Cd, Co, Ni) . The formation of ternary chlorides according to the equation nKCl + MCl₂ = K_nMCl_n+2 with M = Ca, Cd, Co, Ni was investigated with a galvanic cell for solid electrolytes. Additionally to the Gibbs energies for the solid reactions, ΔG_R, the entropies, ΔS_R, and enthalpies, ΔH_R were determined by the dependence of the e.m.f. on temperature. But the stability of the double chlorides is given by the free enthalpy of synproportionation from the neighboured compounds. In case of RbSrCl₃ and RbPbCl₃ (stable only at higher temperature) the synproportionation is endothermic; the loss of enthalpy is compensated by a gain of entropy. The same is valid for K₂CoCl₄. Lattice parameters were measured for the modifications of KCaCl₃; the structure of KCdCl₃ was refined by single crystal measurements.     

Thermodynamic determination of solvation potentials of various metal chlorides by (1,4-dioxane + water) mixtures through EMF measurements

The EMF data of different metal chlorides (2:1 electrolytes) were obtained by using a cell [M_X Hg|MCl₂ (m)|AgCl–Ag] at two temperatures. Stock solutions of metal chlorides (CoCl₂, CuCl₂ and ZnCl₂) were prepared by weight in 1,4-dioxane–aqueous mixtures. There was a significant change in the EMF values with change of metal chloride, its concentration and solvents composition. The standard electrode potential (E°) values of the above cell were calculated from the measured EMF of these mixtures. The standard thermodynamic functions (ΔG°, ΔH° and ΔS°) and respective transfer parameters of MCl₂ from water to 20, 45 and 70% dioxane–water mixtures were also evaluated. Equilibrium dissociation constants (K₁ and K₂) as well as the degrees of dissociation (α₁ and α₂) were obtained by iterative procedures. The data were analyzed in terms of solute–solvent interactions depending on standard and transfer thermodynamic parameters and mean activity coefficients (γ_±) of electrolytes.     

Cationic polymerization with titanium(iv) compounds: Living polymerization and possibility of stereoregulation

This paper deals with the development of living cationic polymerizations and the possibility of stereoregulation therein based on the modulation of the Lewis acid activators by their ligands. For this, titanium(IV) chlorides [TiCl₄-n(OR)n] with various alkoxy or aryloxy groups were synthesized and employed for the cationic polymerizations of isobutyl vinyl ether (IBVE) in conjunction with HCl-IBVE adduct. Living polymerizations were feasible with the titanium chlorides [TiCl₂(OR)₂] disubstituted with isopropoxy or phenoxy groups in CH₂Cl₂ at −15°C. The meso (isotactic) contents of the polymers obtained with TiCl₂(OR)₂ at −78°C became larger (up to 86%) with bulkier o-substituents of phenoxy groups on the titanium compounds.     

Titanium and zirconium complexes with aminoiminophosphorane ligands

A series of titanium and zirconium complexes based on aminoiminophosphorane ligands [Ph₂P(Nt‐Bu)(NR)]₂MCl₂ ( 4 , M = Ti, R = Ph; 5 , M = Zr, R = Ph; 6 , M = Ti, R = SiMe₃; 7 , M = Zr, R = SiMe₃) have been synthesized by the reaction of the ligands with TiCl₄ and ZrCl₄. The structure of complex 4 has been determined by X‐ray crystallography. The observed very weak interaction between Ti and P suggests partial π‐electron delocalization through both Ti and P. The complexes 4–7 are inactive for ethylene polymerization in the presence of modified methylaluminoxane (MMAO) or i‐Bu₃Al–Ph₃CB(C₆F₅)₄ under atmospheric pressure, and is probably the result of low monomer ethylene concentration and steric congestion around the central metal. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis,structure and ethylene polymerization of group 4 complexes with phosphinoamide ligands

Group 4 complexes containing diphosphinoamide ligands [Ph₂PNR]₂MCl₂ (3: R = ^tBu, M = Ti; 4: R = ^tBu, M = Zr; 5: R = Ph, M = Ti; 6: R = Ph, M = Zr) were prepared by the reaction of MCl₄ (M = Ti; Zr) with the corresponding lithium phosphinoamides in ether or THF. The structure of [Ph₂PN^tBu]₂TiCl₂ (3) was determined by X‐ray crystallography. The phosphinoamides functioned as η²‐coordination ligands in the solid state and the Ti? N bond length suggests it is a simple single bond. In the presence of modified methylaluminoxane or i‐Bu₃Al/Ph₃BC(C₆F₅)₄, catalytic activity of up to 59.5 kg PE/mol cat h bar was observed. Copyright © 2005 John Wiley & Sons, Ltd.     

STUDIES ON THE KINETICS OF PROPYLENE POLYMERIZATION WITH THE COMPLEXTYPE TiCl_3 CATALYST

The active center concentration C_p, the rate constant k_p, and the activation energy of chain propagation E_p in the polymerization of propylene with complex-type TiCl_3-(C_2H_5)_2AlCl catalyst system were studied. The Mn was corrected by (?) value determined by GPC. The values thus obtained for C_p, k_p, and E_p at 50℃were 3.01 mol/mol Ti, 6.27 1/mol·sec, and 5.10 Kcal/mol respectively.The kinetic parameters were compared with those obtained from conventional TiCl_3·AlCl_2 catalyst, showing that the higher activity of the complex-type catalyst over the conventional catalyst is not only due to the higher C_p of the former, but to a greater extent due to the increase of the k_p value.     

A SCF Xα MO study of the optical and Ti2p core photoemission spectra of TiCl4

SCF Xα MO calculations on the ground state and optical excitation transition states of TiCl₄ accurately predict the energies of its UV absorption peaks. Calculations on the Ti2p core ion state and associated transition states indicate that the recently observed low energy (4.0 eV) Ti2p satellite arises from ligand to metal charge transfer excitations while the satellite at high energy (9.4 eV), similar to those previously observed in Ti(IV) compounds, can be attributed to transitions from the highest filled orbitals to empty orbitals with Cl3pTi4s. 4p antibonding character.     

Ti掺杂的MgH2和Mg2NiH4的放氢性能

以TiF₃和Ti(OBu-n)₄为催化剂, 研究了Ti离子掺杂对MgH₂和Mg₂NiH₄放氢性能的影响. 结果表明, 未掺杂的MgH₂起始放氢温度为420 ℃, 掺杂TiF₃和Ti(OBu-n)₄后分别降低到360和410 ℃; Mg₂NiH₄在掺杂TiF₃后放氢温度由230 ℃降低到220 ℃, 而掺杂Ti(OBu-n)₄后没有变化. 可见无论对MgH₂或Mg₂NiH₄, 在降低放氢温度方面TiF₃都明显优于Ti(OBu-n)₄. 另外, 研究还发现, TiF₃掺杂对MgH₂放氢动力学有显著的提高, 但对Mg₂NiH₄没有明显的提高. 结合XRD和FTIR的测试分析, 我们认为: 催化作用很大程度上取决于氢化物自身的晶体结构和催化剂的电子结构; 降低氢化物放氢温度和提高动力学性能的原因是催化剂与氢化物之间的相互作用削弱了氢化物中Mg—H或Ni—H键, 使得活泼的H…H原子对容易形成, 从而有利于H₂的释出.     

Pyridine adsorption on small Nin‐cluster (n = 2,3,4): A study of geometry and electronic structure

Adsorption of pyridine on Ni_n‐clusters (with n = 2,3,4) is studied by quantum chemical calculations at B3LYP/LANL2DZ and B3LYP/6‐311G^** levels. First, Ni_n‐clusters are investigated for accessible structure and electronic states. The lowest electronic state with four unpaired electrons is predicted for Ni₄‐cluster based on geometry and electronic structure, showing that the cluster stability nicely depends on number of unpaired electrons. Correction for basis set superposition error of metal‐metal bond is appreciable and has increasing effect on cluster binding energy. Next, adsorption of pyridine in planar and vertical adsorption modes is investigated on rhombus Ni₄‐cluster. The vertical mode is found (at B3LYP/6‐311G^** level) as the most favorable adsorption mode. Adsorption energy (ΔE_ads) depends on cluster size; adsorption on Ni₄‐cluster is most favorable with ΔE_ads = ?207.33 kJ/mol. The natural bond orbital analysis reveals the charge transfer in adsorbate/metal‐cluster. Results of investigations for the Ni₂‐ and Ni₃‐cluster are also presented. © 2012 Wiley Periodicals, Inc.     

Reactions of 2-pyridylphenylacetonitrile and 1,2-dicyano-1,2-di(phenyl)-1,2-di(2-pyridyl)ethane with titanium(IV), vanadium(IV), chromium(III) and iron(III) chlorides

Summary 2-Pyridylphenylacetonitrile (ppa) is oxidized by iron(III) chloride in dry ethanol to 1,2-dicyano-1,2-di(phenyl)-1,2-(2-pyridyl)ethane (dcppe). When 1,2-dichloroethane or ether are used as solvents, a 31 complex of dcppe with iron trichloride, [(FeCl₃)₃(dcppe)] is obtained.Titanium(IV), vanadium(IV) and chromium(III) chlorides react with ppa and dcppe, giving complexes of general formulae [MCl₄(ppa)] (M = Ti or V), [CrCl₃(ppa)_n] (n = 2 or 3), [(MCl₄)₂(dcppe)] (M = Ti or V) and [CrCl₃(dcppe)].