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Yttrium alkyl complexes Cp* 2 YR react with CH bonds of alkenes to form either yttrium allyl complexes or yttrium vinyl complexes. Less substituted alkenes react faster, consistent with prior alkene coordination. The selectivity of the reaction of Cp* 2 YR with CH bonds is allylic CH 3 ≫vinyl CH≫allylic CH 2 . Propene is readily metallated by Cp* 2 YR giving the η 3 -allyl complex Cp* 2 Y(η 3 -CH 2 ⋯ CH  CH 2 ) which does not react further with propene. This explains why Cp* 2 YR (R=alkyl, H) complexes make poor propene polymerization catalysts.

Homogeneous polymerization catalysts composed of transition metals have been highly attractive in the last two decades because of their high activity and high selectivity for synthesis of well-defi...

The title complexes (CH2 CHCH2CH2C5H4)2Ln Cl·2THF (Ln=Sm, Y, Dy, Er) were synthesized as air and moisture sensitive free-flowing oils that have been fully characterized by MS, EA and IR. The EA and IR results indicate the presence of coordinated THF molecules. No evidence of intra-molecular coordination of the butenyl side-chain was observed. In association with Al(i-Bu)3, the complexes have shown high activity for the bulk polymerization of MMA. At a MMA/catalyst (MMA/cat) molar ratio of 2000, temperature of 80 °C and polymerization time of 30 h, the catalyst system produced at a 70% conversion a syndiorich polymer (rr=62%), Mη=1.65×106. Effects of temperature, time and molar ratios of MMA/catalyst and catalyst/cocatalyst on the polymerization have been studied. The result showed that higher temperature, longer time and Al/catalyst molar ratio=10 are conditions suitable for polymerization.

The half-sandwich imido tantalum dichloride (η5-C5Me4H)Ta(NtBu)Cl2 is prepared directly from the reaction of the neutral constrained-geometry ligand Me2Si(C5Me4H)(tBuNH) and TaCl5 in refluxing tolu...

Select recent advances in the area of stereoselective polymerization catalysis are surveyed. Although heterogeneous catalysts are the pillars of the chemical industry, homogeneous polymerization catalysts offer unmatched opportunities for the precision synthesis of new polymer architectures. In addition, these discrete ‘single-site’ catalysts offer extraordinary potential to examine reaction pathways at the molecular level via mechanistic studies. This article will examine discrete catalysts for stereoselective polymerization, with an emphasis on technologically important processes.

Research on "post-metallocene" polymerization catalysis ranges methodologically from fundamental mechanistic studies of polymerization reactions over catalyst design to material properties of the polyolefins prepared. A common goal of these studies is the creation of practically useful new polyolefin materials or polymerization processes. This Review gives a comprehensive overview of post-metallocene polymerization catalysts that have been put into practice. The decisive properties for this success of a given catalyst structure are delineated.

This paper reviews the findings of quantitative structure–activity relationship (QSAR) studies focusing on single-site polymerization catalysts, with special attention paid to the use of 3D-QSAR tools. Such tools reveal the fine details of catalyst structure that may be correlated with polymerization activity or the properties of the synthesized polymer. The introduction of effective single-site polymerization catalysts, in addition to allowing scientists to synthesize new tailor-made polymers, has enabled a detailed theoretical analysis of the synthesis process. The benefits of single-site polymerization for theoretical studies include easy elucidation of the catalyst structure, a well-defined mechanism of action, and the fact that experiments can be systematically conducted on catalyst series featuring different substitution patterns. Using QSAR methods, experimental results can be related to theoretical measurements through statistical or chemometric tools. These tools have been extensively and success...

As an alternative to the standard Cossee mechanism, in which olefin insertion involves two sites at a single metal centre, we have investigated a true dinuclear alternative where the chain switches between two different metal centres at each insertion. The corresponding dinuclear variations of  hydrogen elimination (BHE) and  hydrogen transfer to monomer (BHT) were also investigated. Surprisingly, calculations indicate that the barriers for both insertion and BHT at two different metal centres are rather similar to those for the more usual mononuclear mechanisms. Dinuclear BHE is more competitive as a chain transfer mechanism, although it always has a higher barrier than BHT. In any system where polymerization at an unknown aluminium active species is believed to occur, dinuclear insertion should be considered as a real alternative to the "standard" mononuclear mechanism. However, from the systems we have studied the prospects for designing highly active, high-MW Al polymerization catalysts (i.e. significantly better than trialkylaluminium) appear just as dim for dinuclear as for mononuclear species.

Discovery of effective homogeneous transition metal catalysts for olefin polymerization must be one of the most dramatic technologies for polymer synthesis in the 1980s. Especially, development of group 4-metallocene catalysts not only improved the property of manufactured polyolefins but also made us possible to synthesize new type polyolefins. A large number of studies have also been made on structure and property of the resultant polyolefins with the advance of catalyst technology. Over the past few years, trend in catalyst development has moved from modification of group 4-metallocene catalysts to search for new generation catalysts, such as non-metallocene catalysts and late transition-metal catalysts. Some of the new catalysts can proceed specific polymerizations, which are not achieved with existent olefin polymerization catalysts. Although, there are some subjects for the manufacturing of new catalysts and polyolefins, the technologies are progressing rapidly. In this review, we highlight not only the development of polymerization catalysts but also the polyolefins obtained with the new catalysts in the last decade.

Direct insertion of ethylene into the chromium−carbon bond in singly charged bis(imido)chromium(VI) cations has been investigated for n-alkyl and benzyl as starting polymer chains. Frontside coordination of ethylene takes place without activation to give a stable complex. Subsequent insertion into the Cr−alkyl bond requires a free energy of activation of 15 kcal/mol and an even higher barrier in the case of a benzyl ligand. Near the transition state, the reaction coordinate is dominated by inversion of the metal complex. Ethylene coordination in the backside mode requires considerable activation, and the additional increase in free energy through loss of entropy makes direct coordination unlikely. An indirect route to the β-agostic backside π-complex is found by inversion of the corresponding frontside ethylene−chromium complex. This rearrangement takes place via a transition state that has comparable or slightly lower free energy than that of direct insertion starting from the frontside π-complex. Howeve...

CpTiCl 2 (OR) (R=Cyclohexyl, CH 2 Ph, C 6 H 4 -Bu t -p, n Bu, i Bu, CH 2 CHCH 2 ) are synthesized, characterized and tested as syndiotactic polymerization catalysts of styrene. The structure and nature of the R group has a great effect on the activity of catalysts. Unsaturated groups and the conjugation of unsaturated groups with oxygen result in the drop of activity; while a more hindered R group increases activity.

A theoretical study has been carried out on two types of olefin polymerization catalysts based on the same M(III) centers (M = Ti, V, Cr) but different (mono) anionic ligand designs. The first system contains a mono-β-diiminato ligand that binds through the two imine nitrogens to the M(III) center and has the nitrogen lone-pairs perpendicular to the NMN coordination plane. It is shown that the generic mono-β-diiminato ligand system without bulky substituents on the nitrogen has barriers (kcal/mol) for insertion (Ti: 10.7; V: 12.2; Cr: 10.4) quite similar to the β-hydrogen transfer process (BHT) (Ti: 11.2; V: 9.8; Cr: 8.4), which serves as the chain-terminating step. The close proximity of the two barriers is in line with findings for other bidentate nitrogen ligands, where bulky aryl groups on the nitrogens were required in order to increase the BHT barrier relative to insertion and ensure acceptable molecular weights. The second system contains a bridged diamide ligand in which the ligand backbone ...

After a short comparative analysis of different macromolecular ligands reported in the relevant literature, the presentation will be centered on the results obtained in the authors' laboratory using structurally defined inorganic supports in terms also of their macromolecular structure. Zeolites and mesomorphous silica can link, after proper chemical modification of their surface with MAO, unmodified metallocene complexes through cage entrapment and weak interactions, thus allowing the transfer from the solution to the solid phase. The metallocene complexes in their new phase are characterized by the catalytic behavior in olefin polymerization after activation with MAO. A decrease of productivity is generally observed depending on the type of support. The steric hindrance provided by the support is evidenced by the depression of chain transfer rate with formation of higher molecular weight polymers. Also shape selectivity is observed during copolymerization of ethylene with a-olefins having variable size. These steric effects are released when going from HY zeolite to MCM silica.

The ligands aminobis(N-ethylenesalicylidenimine) (SalenN3H3) and aminobis(N-propylenesalicylidenimine) (SalpenN3H3) were used to form the bimetallic complexes SalenN3H{AlMe2}2 (1), SalpenN3H{AlMe2}2 (2), SalenN3H{AlMeCl}2 (3) and SalpenN3H{AlMeCl} (4). When extracted in THF 3 and 4 redistribute to form the ionic compounds [SalenN3H{Al(THF)}]+ [AlMe2Cl2]− (5) and [SalpenN3H{Al(THF)}]+ [AlMe2Cl2]− (6). The compounds were characterized by Mp analyses, 1H-NMR and IR, and in the case of 2 and 6 by X-ray crystallography. Additionally, the potential of 5 and 6 to serve as propylene oxide polymerization catalysts was examined.

A series of five-coordinate bis(phenolate) titanium hydrocarbyl complexes (MBP)Ti(η2-R)R' was prepared, with MBP = 2,2'-methylenebis(4-methyl-6-tert-butylphenolate), R = C6H4(o-CH2NMe2); R' = Cl, OSO2CF3, Me, CH2CMe3 or R = CH2C6H4(o-NMe2); R' = Cl, Me. A structure determination of (MBP)Ti[η2-C6H4(o-CH2NMe2)]OSO2CF3 showed the metal to have a distorted trigonal bipyramidal coordination geometry. Cationic four-coordinate derivatives [(MBP)Ti(η2-R)]+ were generated by reacting the R' = Me derivatives with the Lewis acid B(C6F5)3. These cations were found to undergo stoichiometric insertions of ethene and propene into the Ti-C bond, as seen by 1D and 2D-NMR spectroscopy and quenching reactions with CD3OD.

One-pot synthesis of poly(cyclic ortho ester)s by the reaction of potassium perfluoroalkanoates with epibromohydrin (EBH) using quaternary onium salts is described. The reaction of potassium trifluoroacetate (KTFA) with EBH using quaternary onium salts such as tetrabutylphosphonium bromide (TBPB) produces the polymer with five-membered cyclic ortho ester structure in the backbone. This means that quaternary onium salts act as phase-transfer catalysts in the first step and polymerization catalysts in the second step during the reaction.

The synthesis and characterization of novel bimetallic, neutrally charged dinickel 2,7-diimino-1,8-dioxynaphthalene polymerization catalysts is reported. Ethylene polymerizations as well as ethylene-co-norbornene copolymerizations display increased catalytic activity, methyl branch formation, and comonomer enchainment selectivity versus the monometallic analogues. Furthermore, these systems turn over in the absence of cocatalyst under mild conditions.

The synthesis and catalytic activity in ethylene polymerization of new vanadium complexes of 2,2′-oxydiethanethiolate [O(CH2CH2S)22–] are described; the complexes [V(µ-DIPP)2{O(CH2CH2S)2}Li(MeCN)2] and [V(DIPP){O(CH2CH2S)2}(py)] [DIPP = (OC6H3Pri2-2,6)–] have been structurally characterized.

The present work details the synthesis and structural characterization of six-coordinate aluminium cations derived from the single starting material, Salen(tBu)AlCl 1 [Salen(tBu) = N,N′-ethylenebis(3,5-di-tert-butylsalicylideneimine)]. They are of formula [Salen(tBu)Al(base)2]+X– and contain various combinations of base and counter anion; H2O, Cl– 2, MeOH, Cl– 3, MeOH, BPh4– 4, MeOH, OTs– 5. With thf as base and OTs– as the anion, the neutral complex, Salen(tBu)Al(thf)(OTs) 6 is obtained. MeOH can be added to 6 to displace the thf and produce 5. In contrast the addition of acetophenone to 2 does not displace the H2O but produces the hydrogen-bonded complex 2· · ·2(acetophenone) 7. All of the compounds were characterized spectroscopically and, in the case of 3, 5 and 7, by X-ray crystallography. Compounds 1–3 were examined for activity as oxirane polymerization catalysts.

Ortho lithiation is achieved by the treatment of tBuLi to the lithium carbamate compounds derived from 2-R-1,2,3,4-tetrahydroquinolines (R = H, methyl, n-butyl, tert-butyl, and 6-tert-butoxyhexyl), which enables the facile construction of the o-phenylene-bridged (Me4C5, indenyl, or fluorenyl)/amido titanium complexes. The titanium complex derived from 2-methyltetrahydroquinoline exhibits higher activity, higher 1-octene incorporation, and higher molecular weight in ethylene/1-octene copolymerization than the standard CGC, [Me2Si(η5-Me4C5)(NtBu)]TiCl2.

Exo,exo derivatives of the efficient catalyst precursors (diisodicyclopentadienyl)titanium and -zirconium dichloride substituted at the central position have been synthesized. These compounds have been characterized by solution NMR measurements, which also permitted the calculation of rotational barriers. The solid-state structures of exo,exo-bis(3-diphenylphosphinoisodicyclopentadienyl)titanium and -zirconium dichloride were determined by X-ray crystallography. Unfortunately, after activation by methylalumoxane, these complexes are shown to serve as poor catalysts for the polymerization of propene.

Statistical analyses were carried out on patents that deal with metallocenes (see Editor’s note1) that can be used as catalyst (component) for the (co)polymerization of olefins, polymerization catalysts containing these metallocenes, polymerization processes employing these catalysts, polymers obtained by such processes, blends containing these polymers, and further uses of these polymers or blends containing them, and on patents dealing with alumoxanes. A comparison of the number of patents granted in the United States and by the EPO shows that in the US more than twice the number of patents have been granted in these technical areas as compared to Europe. In the field of alumoxanes, where about 20 patents have been granted, only one opposition has been filed. In the field of metallocenes, it was found that 61 oppositions have been filed at the EPO against about 200 granted patents, or about five times the overall figure for oppositions at the EPO, indicating a high prevalence of oppositions in this field. An analysis of the grounds for the oppositions revealed that all oppositions are filed at least on the grounds of lack of inventive step and/or lack of novelty. It turned out that the patents proprietary to different companies active in the field of metallocenes are not equally opposed, e.g. 60% of the patents granted to Exxon are opposed, whereas about 8% of the patents granted to Hoechst are opposed. Also the various companies in the field oppose a distinctly different number of patents. It was also found that in many opposition cases the same proprietor and the same opponent are a party. A family tree of US family members and their European relatives of patents dealing with metallocenes is discussed, showing further marked differences between the situation in the US and in Europe.

Ethylene-bridged bis(N,N-diisopropyl-1-aminoboratabenzene-4-yl)zirconium dichloride (5a), dimethylsilyl-bridged bis(N,N-diisopropyl-1-aminoboratabenzene-4-yl)zirconium dichloride (7a), and dimethylmethylene-bridged (cyclopentadienyl)(N,N-diisopropyl-1-aminoboratabenzene-4-yl)zirconium dichloride (6a) have been prepared. X-ray crystal structures of the dimethyl derivatives of 5 and 7 show that the complexes closely resemble the corresponding ansa-zirconocenes. When activated by excess methylaluminoxane, 5a, 6a, and 7a are catalysts for the polymerization of olefins.

The crystallization of MnCl2 in tetrahydrofuran results in the formation of polymeric [MnCl2(THF)1.6] (1) with an unexpected structure. This species represents the first crystallographically defined example of tetranuclear [Mn4(μ3-Cl)2(μ2-Cl)4Cl2(THF)6] units linked by MnCl2(THF)2 moieties. Our observations highlight the importance of the M4X6 core present in 1 as a component of α-olefin polymerization catalysts.

A semiempirical theoretical method (ICONC) which includes core-core repulsion to the energy terms was used to characterize the 2,2,6,6-tetramethylpiperidine (TMPiP)/MgCl2 system and the ethyl benzoate (EB)/MgCl2 system by modeling TMPiP and EB adsorption on the (110) face of β-MgCl2.

The title compound has been prepared from Cp-2*LaCl2K(THF)(2) and 1-PhC3H4K-(THF)(0.5) in THF suspension, forming yellow single crystals from hexane solution which were characterized in solid state and in solution by elementary analysis, IR, C-13- and variable temperature H-1-NMR spectroscopy and a crystal structure determination. Space group P1, Z = 2, T = 130 K, a = 8.595(1), b = 10.770(1), c = 17.903(5) angstrom, alpha = 93.54(1)degrees, beta = 98.30(1)degrees, gamma = 112.42(1)degrees, R = 0.0249.

The structural features of heterogeneous polymerization catalysts and of heterogenized homogeneous catalysts are shortly summarized. Main data on structural, surface chemical and catalytic behavior of Ziegler-Natta, Phillips type and heterogenized “single-site” polymerization catalysts (metallocene and postmetallocene) used in the industry are discussed. Heterogenization of homogeneous catalysts for chemical applications is also shortly discussed.

16 pags. ; 8 figs. ; 3 schems., This paper reviews the findings of quantitative structure−activity relationship (QSAR) studies focusing on single-site polymerization catalysts, with special attention paid to the use of 3D-QSAR tools. Such tools reveal the fine details of catalyst structure that may be correlated with polymerization activity or the properties of the synthesized polymer. The introduction of effective single-site polymerization catalysts, in addition to allowing scientists to synthesize new tailor-made polymers, has enabled a detailed theoretical analysis of the synthesis process. The benefits of single-site polymerization for theoretical studies include easy elucidation of the catalyst structure, a well-defined mechanism of action, and the fact that experiments can be systematically conducted on catalyst series featuring different substitution patterns. Using QSAR methods, experimental results can be related to theoretical measurements through statistical or chemometric tools. These tools have been extensively and successfully used in the field of drug design. © 2014 American Chemical Society, This study received financial support from the CICYT (project MAT2012-36341).

Preface ... ix 1. Academia and Industrial Pilot Plant Operations and Safety ... 1 Joel J. Justin 2. Thermodynamics as a Tool for Laboratory and Chemical Safety in the Undergraduate Chemistry Curriculum ... 25 Elmer B. Ledesma and Mary K. Moore 3. Considerations for Scale-Up DDS Moving from the Bench to the Pilot Plant to Full Production ... 37 Frankie Wood-Black 4. Management of Change: Pilot Plant Scale ... 47 Neal Langerman 5. Transitioning Culture: Teaching and Modeling Workplace Behavior ... 53 M. A. Thomson and W. Killian 6. Blast Energy and Damage Assessment from the Mechanical Explosion of Compressed Gas Cylinders ... 59 Elmer B. Ledesma 7. A Practical Method of Neutralizing Cr(VI) in Phillips Polymerization Catalysts ... 73 Kathy S. Collins and Max P. McDaniel 8. Scale Up in Brewing: Factors in Changing Batch Size from 5 Gallons to 15 Barrels ... 85 C. J. Archambault, W. R. W. Gerds, and A. M. Mills Editors' Biographies ... 91 Indexes Author Index ... 95 Subject Index ... 97

As modifications of the effective catalyst precursor [dimethylsilanediylbis(benz[e]indenyl)]zirconium dichloride, the ansa-zirconocene complexes Me2Si(cyclopenta[c]phenanthryl)2ZrCl2, Me2Si(cyclope...

Four possible structures of C 2 -symmetric bis(fluorenyl)zirconium complexes are presented. Three bis(fluorenyl)zirconocene complexes have been prepared and tested for the polymerization of propylene and ethylene. rac / meso -Dichloro[ η 10 -(1,2-ethanediyl)bis ( 7H- benzo[c]fluoren -7- ylidene)zirconium ( 10 10 ∗ ) seems to be the most active polymerization catalysts for ethylene.

Temperature-programmed calcination of basic chromium(III) acetate impregnated onto a high surface area silica support and chromium(III) acetylacetonate dry-blended with silica has been studied by quadrupole mass spectrometry and infrared spectroscopy. In both cases the same reactive intermediate has been identified.

The compound [HNMe2Ph][NpB(C6F5)3] (Np = (CH3)3CCH2) reacts with dimethylzirconocenes to give active propylene polymerization catalysts which are significantly more active and give higher molecular weight polypropylene than do the catalysts obtained using B(C6F5)3; the [NpB(C6F5)3]− anion is for steric reasons more weakly coordinating than is [MeB(C6F5)3]−.

By treating cyclodextrin(CD) with methylaluminoxane (MAO such as PMAO or MMAO) or trimethylaluminium (TMA) followed by Cp2ZrCl2, CD/PMAO/Cp2ZrCl2, CD/MMAO/Cp2ZrCl2 and CD/TMA/Cp2ZrCl2 catalysts were prepared. The catalysts were analyzed by 13C-CP/MAS NMR spectrometer and ICP to examine the structure of catalyst and content of Zr and Al. Ethylene polymerization was conducted with MAO or TMA as cocatalyst. Styrene polymerization was also carried out with α-CD/MMAO/Cp*TiCl3 and α-CD/TMA/Cp*TiCl3 catalysts. While the ordinary trialkylaluminium such as TMA as well as MAO can be used as cocatalyst for ethylene polymerization, only MAO could initiate the styrene polymerization with α-CD supported catalysts.

Electrochemistry of (p-CH3PhNC)6Cr+3 and optical spectroscopy of [1,2-(9-fluorenyl)2C2H4]ZrMe+ have been used to craft scales of coordinating ability of various anions. Coordinating ability also influences the barriers to intramolecular rearrangement in (RCp)2ZrMe+ as well as activity of zirconocenium ions as polymerization catalysts.

Weakening the sidearm donor of amine bis(phenolate) titanium and zirconium polymerization catalysts causes a 10-fold enhancement in activity of the former and no difference in activity of the latter, while increasing the termination to propagation ratios in both.

The coordination strength of various phosphine oxides OPR3 toward the olefin polymerization catalyst (P∧O)PdMe (P∧O = κ2-P,O-Ar2PC6H4SO2O with Ar = 2-MeOC6H4) as compared to that of dmso has been determined. Equilibrium constants KL for the reaction 1-dmso + L ⇆ 1-L + dmso range from 3.5 for electron-rich OPBu3 to 10–3 for electron-poor OP(p-CF3C6H4)3. Complexes derived from more strongly coordinating phosphine oxides, i.e. [(P∧O)PdMe(L)] (1-L; L = OPBu3, OPOct3, OPPh3) have been isolated and fully characterized. Additionally, 1-OPBu3 and 1-OPPh3 were analyzed by X-ray diffraction analyses. Complexes derived from weakly coordinating phosphine oxides have eluded isolation due to loss of phosphine oxide and formation of barely soluble multinuclear palladium complexes 1n by bridging coordination of the sulfonate group to various Pd centers. Hence, the (P∧O)PdMe fragment 1 exhibits an intrinsic limitation with respect to coordination of weak donors. Species 1 generated in situ in the absence of additional lig...

Over the past 15 years, ring-opening metathesis polymerization (ROMP) and related techniques, such as the metathesis-based 1-alkyne polymerization and cyclopolymerization, have established themselves as highly valuable and potent tools for the synthesis of functional supports and surfaces. In this chapter, the polymerization from and to surfaces using either ROMP or 1-alkyne polymerization, as well as the synthesis of functional supports, whether inorganic or organic, is summarized. In this context, both ‘grafting-from’ and ‘grafting-to’ techniques in combination with well-defined catalytic systems suitable for these purposes will be discussed. Special consideration will be given to the specific properties of the different supports used and created, that is, silica, silicon, and organic supports and the particular requirements for the polymerization catalysts used. The obtained surface-modified materials will be discussed in view of their applications, which are so far mainly located in the areas of separation science, catalysis, and molecular electronics.

An equimolar mixture of Cp*Ti(CH3)3 (2) and Ph3C+[B(C6F5)4]− (1) forms a highly active and syndioselective catalyst for the polymerization of styrene, producing 96% syndiotactic polystyrene (PS) at an activity of 0.91 × 107 g PS (mol Ti)−1 (mol styrene)−1 h−1. Both activity and syndioselectivity can be increased using tri–isobutylaluminum (TIBA) to scavenge the system. ESR measurements indicate that the polymerization proceeds via titanium(IV) intermediates. Catalysts derived from 2/methylaluminoxane (MAO) as well as Cp*TiCl3/MAO also function as syndioselective styrene polymerization catalysts, but are less active than the ‘cationic’; system derived from 1 and 2.

The reaction between NaNH2 and B(C6F5)3 affords the amidodiborate anion [H2N{B(C6F5)3}2]-, the structure of which shows multiple intramolecular NH···F hydrogen bonding. Reaction with HCl affords [H(OEt2)2][H2N{B(C6F5)3}2], while treatment of zirconocene dimethyls with [CPh3][H2N{B(C6F5)3}2] gives highly active alkene polymerization catalysts.