Non-metallocene
140344053
Uranocenium: Synthesis, Structure, and Chemical Bonding.
Abstraction of iodide from (e5 C5 i Pr5 )2 UI] (1) produced the cationic uranium(III) metallocene (e5 C5 i Pr5 )2 U] (2) as a salt of [B(C6 F5 )4 The structure of 2 consists of unsymmetrically bonded cyclopentadienyl ligands and a bending angle of 167.82deg at uranium. Analysis of the bonding in 2 showed that the uranium 5f orbitals are strongly split and mixed with the ligand orbitals, thus leading to non negligible covalent contributions to the bonding. Investigation of the dynamic magnetic properties of 2 revealed that the 5f covalency leads to partially quenched anisotropy and fast magnetic relaxation in zero applied magnetic field. Application of a magnetic field leads to dominant relaxation by a Raman process.
Angewandte Chemie
Fu-Sheng Guo Yan-Cong Chen Ming-Liang Tong Akseli Mansikkamaki Richard A Layfield
46948139
Oligomerization of 2 chloroallyl alcohol by 2 pyridinecarboxylate complex of chromium(III) new highly active and selective catalyst
The new 2 pyridinecarboxylate (2 pic) complex of chromium(III) has been designed and synthesized as a new highly active and selective oligomerization catalyst. The crystal structure of the new compound has been determined by X ray diffraction. The composition and purity of [Cr(2 pic)2(OH2)2]NO3 have been confirmed by several spectroscopic methods and the elemental analysis. Furthermore, the new complex has been investigated towards its catalytic activity for the oligomerization of 2 chloro 2 propen 1 ol under the atmospheric pressure and at room temperature. It has turned out that the novel catalyst exhibits a very high catalytic activity. Consequently, [Cr(2 pic)2(OH2)2]NO3 belongs to a new generation of non metallocene catalysts.
Scientific Reports
Joanna Drzezdzon Artur Sikorski Lech Chmurzynski Dagmara Jacewicz
103220050
A Methylene bridged salicylaldiminato tridentate [ONS] binuclear titanium complex for ethylene norbornene copolymerization
ABSTRACT A binuclear titanium complex Ti2La with methylene bridged salicylaldiminato tridentate [ONS] ligand bearing octylthio sidearm was synthesized and used for the copolymerization of ethylene and norbornene (E NB) The complex exhibited activity over 106 g/mol(Ti).h.atm and high degree incorporation of co monomer (up to 49.9 mol affording high molecular weight copolymers with narrow molecular weight distribution. The E NB copolymers produced by Ti2La/MMAO contained NN dyad and NNN triad sequences even at low norbornene feeds, in contrast to the observation of such sequences only at high level of NB incorporation for most other catalyst systems. The monomer reactivity ratios were calculated to be rE 14.62 and rN 0.08, of which the rN value was much larger than that from non metallocene titanium catalyst systems. The catalytic performances of the binuclear complex Ti2La and its mononuclear analogue TiLb were also compared, with the binuclear complex exhibiting higher catalytic activity and NB incorporation ratio due to the binuclear cooperative effect, and producing much higher molecular weight copolymer due to the increased steric hindrance caused by close proximity of two growing chains. To the best of our knowledge, this is one of the few examples of binuclear catalyst for E NB copolymerization with high activity and efficient incorporation of norbornene. GRAPHICAL ABSTRACT A non metallocene binuclear titanium complex was prepared and used for ethylene norbornene (E NB) copolymerization. The complex demonstrated higher catalytic activity and incorporation of norbornene in comparison with those of its mononuclear analogue, showing apparent positive "comonomer effect" The insertion ratios of NB could be flexibly tuned through changing of the NB feed. The E NB copolymers contained NN dyad and NNN triad sequences even at low NB feeds and incorporation due to the high activity of the catalyst system.
Xiong-Bin Chen Yi Zeng Zhi-da Lan Qingliang You Tingcheng Li Xiangdan Li Daohong Zhang Guangyong Xie
103478479
The investigation of terpolymerization of ethylene/propylene/o cl a vinyl monomers catalyzed by Cat.L Pd catalyst
We investigated the terpolymerization of ethylene/propylene/o Cl a vinyl monomers to obtain polar terpolymers by non metallocene catalyst Cat.L Pd through coordination polymerization directly. The functional o Cl a vinyl monomer inserted into the polymeric molecules changed the properties of the obtained polymers. The optimum catalyst Cat.L Pd and polymerization conditions were optimized for the terpolymerization. The structure and properties of the terpolymers were characterized by FTIR, 13C (1H) NMR, DSC and GPC. The optimum incorporation content of 11 chloro 1 undecylene within the terpolymer chains is up to 3.58 mol% The polar monomers did not carry out the homopolymerization itself, but efficiently joined the terpolymerization with ethylene and propylene. Propylene monomer was in favor of the copolymerization with ethylene beside its homopolymerization. But polypropylene segments were not observed within the terpolymer chains. Compared to the polar monomers and propylene, ethylene was the most efficient monomer for joining the terpolymerization of ethylene/propylene/o Cl a vinyl monomers, and longer segments of polyethylene were produced within the terpolymer chains. M w up to 2x105 g/mol of the terpolymers was obtained by the catalyst system. The terpolymer molecular weight distribution (MWD) was about 2 to 3, implying the terpolymerization behavior followed the single site mechanism.
Wang Fan Xianghui Shi Feng Nan Hongming Li Wang Qiucan Yuan Hongchao Qigu Huang Wantai Yang
227039164
Interaction of metallocene dichlorides with apo human transferrin: A spectroscopic study and cytotoxic activity against human cancer cell lines.
Metallocene dichlorides (Cp2M(IV)Cl2) are the first class of small and hydrophobic organometallic compounds classified as anticancer agents against numerous cancer cell lines and tumors. In this study, the antiproliferative activities of Cp2VCl2,Cp2NbCl2, Cp2HfCl2 and Cp2ZrCl2were assessed on two human cancer cell lines (HT 29 and MCF 7) using MTT assay. Spectroscopic studies were also conducted using these and other known metallocene dichlorides on apo human transferrin (apo hTf) at pH 7.4. UV Vis and CD showed that their interaction with apo hTf could induce conformational changes of its secondary structure during binding process. In fluorescence, a decrease in intensity of the emission peak was observed when the apo hTf:Cp2M(IV)Cl2 complex is being formed, probably due to changes in the microenvironment of its tyrosine and tryptophan residues. Among all metallocene dichlorides studied, Cp2VCl2 has the strong ability to quench the intrinsic fluorescence of apo hTf through a static quenching mechanism. The association constants for each protein compound complex were also determined at different temperatures (296 K, 303 K, 310 K, and 317 K) based on fluorescence quenching results. Positive enthalpy changes (DH) and entropy changes (DS) as well as negative free energies (DG) suggest that hydrophobic interactions are the main intermolecular forces involved in the binding process, probably via an endothermic and spontaneous reaction mechanism. The distance, r, between donor (apo hTf) and acceptor (Cp2M(IV)Cl2) obtained according to Forster's theory of non radiation energy transfer suggest that the energy transfer from apo hTf to Cp2M(IV)Cl2 occurs with high probability and distances obtained by FRET with high accuracy.
International journal of molecular biology
Jorge R Guette Fernandez Xiomara Narvaez Pita Enrique Melendez Elsie I Pares Matos
104269706
Post and Non metallocenes for Olefin Insertion Polymerization
Moritz C Baier Stefan Mecking
212688007
The duality of electron localization and covalency in lanthanide and actinide metallocenes+
Previous magnetic, spectroscopic, and theoretical studies of cerocene, Ce(C8H8)2, have provided evidence for non negligible 4f electron density on Ce and implied that charge transfer from the ligands occurs as a result of covalent bonding. Strong correlations of the localized 4f electrons to the delocalized ligand p system result in emergence of Kondo like behavior and other quantum chemical phenomena that are rarely observed in molecular systems. In this study, Ce(C8H8)2 is analyzed experimentally using carbon K edge and cerium M5,4 edge X ray absorption spectroscopies (XAS) and computationally using configuration interaction (CI) calculations and density functional theory (DFT) as well as time dependent DFT (TDDFT) Both spectroscopic approaches provide strong evidence for ligand metal electron transfer as a result of Ce 4f and 5d mixing with the occupied C 2p orbitals of the C8H82 ligands. Specifically, the Ce M5,4 edge XAS and CI calculations show that the contribution of the 4f1, or Ce3+ configuration to the ground state of Ce(C8H8)2 is similar to strongly correlated materials such as CeRh3 and significantly larger than observed for other formally Ce4+ compounds including CeO2 and CeCl62 Pre edge features in the experimental and TDDFT simulated C K edge XAS provide unequivocal evidence for C 2p and Ce 4f covalent orbital mixing in the d antibonding orbitals of e2u symmetry, which are the unoccupied counterparts to the occupied, ligand based d bonding e2u orbitals. The C K edge peak intensities, which can be compared directly to the C 2p and Ce 4f orbital mixing coefficients determined by DFT, show that covalency in Ce(C8H8)2 is comparable in magnitude to values reported previously for U(C8H8)2. An intuitive model is presented to show how similar covalent contributions to the ground state can have different impacts on the overall stability of f element metallocenes.
Chemical science
Danil E Smiles Enrique R Batista Corwin H Booth David L Clark Jason M Keith Stosh Anthony Kozimor Richard L Martin Stefan G Minasian David K Shuh S Chantal E Stieber Tolek Tyliszczak
202033836
Lanthanides and actinides: Annual survey of their organometallic chemistry covering the year 2018
This review summarizes the progress in organo f element chemistry during the year 2018. A continuing trend for many years, which remained important in 2018, was the synthesis and investigation of reactive trivalent lanthanide mono and bis(alkyl) or (benzyl) complexes supported by a variety of non cyclopentadienyl ligands such as amidinates, b diketiminates or NHC ligands. An important contribution was the synthesis of the homoleptic, solvent free dibenzyl complexes [Ln(CH2Ph)2]n (Ln Eu, Sm, Yb) which served as precursors for the synthesis of the first divalent lanthanide imides (THF)Ln(m3 NDipp)]4. Lanthanide carbene chemistry has also been of growing interest. Functionalized NHC ligands were employed to unveil new reactivity as demonstrated in the synthesis of homoleptic lanthanide complexes with aryloxide tethered NHC ligands, Ln(LR)3 (LR 2 O 3,5 tBu2C6H2(1 C{N(CH)2N(R) R iPr, tBu, Mes) which reacted with CO2 by selective insertion into Ln C(NHC) bonds. A diverse reactivity towards small unsaturated molecules was observed for phosphino and thiophosphinoyl alkylidene lanthanide complexes as well as for phosphinidene lanthanide complexes. Furthermore, the trinuclear mixed oxo/alkyl complexes L13Ln3(m2 CH3)3(m3 CH3)(m3 O) (with L1 PhC(NC6H3iPr2 2,6)2; Ln Sc, Y, Lu, Dy) undergo non redox oxygen transfer with PhNCS or CS2 despite the presence of reactive Ln alkyl bonds. The synthesis of pseudo Grignard reagents PhLnI (Ln Eu, Yb) was investigated and their synthetic potential in organometallic chemistry demonstrated. The first lanthanide cyclobutadienyl complexes were obtained as anionic "tuck in" complexes [M{e4 C4(SiMe3)4}{e4 C4(SiMe3)3 k (CH2SiMe2)]2 (Ln Y, Dy) showing square shaped cyclobutadienyl ligands. Further progress has been made in the understanding of "new" divalent lanthanide chemistry, especially the influence of the ligand size. The small CpMe ligand formed highly reactive complexes, e.g. [K(crypt)[Y(CpMe)3] with the larger lanthanides, which reacted with the solvent to give unprecedented reductive THF ring opening. However, with smaller lanthanides the complexes (18 crown 6)K(m CpMe)K(18 crown 6)[CpMe3Ln] (Ln Tb, Ho) displaying an inverse sandwich as counter cation, could be isolated. The reactivity of the highly bulky complex SmCpAr Et2 (CpAr Et C5(4 EtC6H4)5) towards a large range of small molecules was investigated, revealing only reaction with cuminil to afford the first trivalent lanthanide decaaryllanthanidocene complex SmCpAr Et2(Ar'C(O)C(O)Ar' (Ar' 4 iPrC6H4) Following the important discovery of recent years on SMM (single molecule magnet) behavior of Dy metallocenes, the quest for even better SMMs continued in 2018. Several new record holding complexes were synthesized based on polyisopropyl cyclopentadienyl complexes, with the best complex to date being (C5iPr5)(C5Me5)Dy] [BAr4] showing magnetic hysteresis up to 80 K and an effective energy barrier to reversal of magnetization Ueff 1541 cm 1. Several remarkable lanthanide arene complexes have been prepared and structurally characterized. For example, the bimetallic inverse sandwich La2+ complex salt [K(18 crown 6)(THF)2](Cp''2La)2(m e6:e6 C6H6)*THF (Cp' C5H3(SiMe3)2 1,3) reduces hydrocarbons such as naphthalene, anthracene, or cyclooctatetraene to give La3+ complexes of the hydrocarbon anions. Samarium arene bonding has also been observed in the rare samarium(II) aryloxide Sm(OAriPr6)2 [AriPr6 C6H3 2,6 (C6H2 2,4,6 iPr3)2] and in the remarkable tetranuclear samarium(II) inverse sandwich complex (u e6:e6 C7H8)[KSmL3]2 (L OSi(OtBu)3) Several new triple decker complexes of the type Ln2(COT')3 (COT' bis(trimethylsilyl)cyclooctatetraenyl dianion) have been isolated and structurally characterized. The synthesis and structural characterization of four unsolvated divalent lanthanide cyclononatetraenyl sandwich complexes, Ln(Cnt)2 (Ln Sm, Eu, Tm, Yb; Cnt e9 cyclononatetraenyl) have also been achieved. Single crystal X ray diffraction studies revealed that these neutral sandwich complexes are rigorously linear. A rare heterobimetallic [1] ferrocenophane terbium(III) complex has been found to exhibit single ion magnet behavior. Reduction of the scandium precursor Sc(nacnac)(OAr)(OCP) (nacnac [ArNC(CH3)]2CH, Ar 2,6 iPr2C6H3) with KC8 afforded a binuclear scandium complex comprising a unique [OCPPCO]4 central motif formed through P P radical coupling. Heterobimetallic Sm/Co polyarsenides (CptttCo)2As4Sm(C5Me4R)2] (Cpttt 1,2,4 C5H2tBu3, R Me, nPr) were synthesized from the reaction of divalent Sm complexes Cp*2Sm, Cp*2Sm(THF)2 or (C5Me4nPr)2Sm with (CptttCo)2(m,e2:2 As2)2] while the Sm/Sb multimetallic complex (Cp*2Sm)4(m4,e2:2:2:2 Sb8) was synthesized from the oxidation of Cp*2Sm with activated antimony. The chemistry of endohedral lanthanide metallofullerenes continued to be an active field of research in 2018. Significant achievements have also been made in the area of organolanthanide catalysis. For example, a variety of highly active lanthanide catalysts for the polymerization of polar substituted styrene monomers as well as the polymerization of 2 vinylpyridine have been developed. Half sandwich complexes of scandium have been successfully employed in the copolymerization of myrcene with ethylene and propylene. New organolanthanide catalyzed reactions include the diastereo and enantioselective C(sp) H addition of terminal alkynes to 3,3 substituted cyclopropenes and the catalytic hydrothiomethylation of olefins and dienes with a series of methyl alkyl sulfides. Moreover, the first time scandium catalyzed C(sp3) H alkylation of N,N dimethyl anilines with olefins has been investigated. Significantly less results over previous years have been published in 2018 on the use of organolanthanide precursors in materials science. The synthesis and reactivity of complexes with actinide element multiple bonds, e.g. AcC, AcN, AcP, is a highly active research area. The synthesis of uranium(IV) silyl phosphino carbene complexes was reported, among which the bis(carbene) complex [U{C(SiMe3)(PPh2)(BIMPTMS)(u Cl)Li(TMEDA)(u TMEDA)0.5]2 (36% showing a 3 center U C P character and a short UCcarbene bond. A rare U(IV) imido species [K(THF)3](PN)U(NH)(iPr2P(C6H3Me)N(C6H2Me2CH2) was isolated, in which one of the PN ligands has been cyclometallated. This complex was proposed to have been formed by the addition of the ligand C H of a nearby methyl group to a uranium nitride intermediate. The synthesis and the diverse reactivity of the first base free terminal phosphinidene thorium(IV) complex, Th(CptBu3)2(PR) towards heterounsaturated small molecules was reported. The functionalization of CO and tert butyl nitrile have been reported for a Th(IV) bis(phosphido) complex, (C5Me5)2Th{P(Mes)(H)}2, involving intramolecular proton transfer reactions. The synthesis and characterization of the first Np(II) organometallic complex [K(crypt)[Np(Cp')3] (crypt 2,2,2 cryptand, Cp' C5H3(SiMe3)2) was achieved by reduction of a trivalent precursor. The synthesis and characterization of a neutral U(II) complex, U(NHAriPr6)2, and the very reactive uranium(III) cation [U(NHAriPr6)2][BArF24] supported by an amido bis(arene) ligand was reported. Good progress has been made in metallofullerene chemistry of the actinides, as evidenced by the structural characterization of the dimetallic actinide endohedral metallofullerene (EMF) U2@C80, revealing short U U bonding inside the cage. Actinide complexes have also found new applications in catalysis, as shown by the first example of selective hydroboration of aldehydes and ketones using actinide catalysis. Previous article in issue
Coordination Chemistry Reviews
Frank T Edelmann Joy H Farnaby Florian Jaroschik Bradley Wilson
208058298
Investigation of melt flow instabilities in SBR: influence of MWD and microstructure at in situ pressure fluctuations as detected by capillary rheology
During the extrusion process of molten polymers, flow instabilities occur which manifest themselves as distortions on the surface and volume of the extrudates1. These phenomena include sharkskin or surface melt fracture, slip stick or periodic melt fracture and gross melt fracture or large amplitude periodic and/or non periodic chaotic anomalies2. In this study the pattern formation of the melt flow instabilities of pure SBR samples which are produced by solution (anionic) or emulsion polymerization are investigated. Those SBR have different bimodal and broad molecular weight distributions (MWD) and microstructure. This study use a high sensitive in situ mechanical pressure instability detection system3,4 in polymer processing equipment in combination with offline and online optical analysis. Thus, the characteristic frequency pattern of instabilities as a function of the apparent shear rate is correlated with the influence of the MWD and the microstructure of the material. INTRODUCTION The characteristic frequency of the melt fracture and the wall slip behavior of solutions of polymerized bimodal SBR resins, and emulsion polymerized SBR with broad MWD were investigated and compared in this study. Linear oscillatory rheological measurements have been done to obtain the linear rheological parameters as reptation and entanglement time, plateau modulus, zero shear viscosity and the molecular entanglement weight. By comparing the flow curve observed by capillary rheology measurements with the linear viscoelastic (LVE) data, it was observed that the apparent slip increased with content of low molecular weight (MW) component.5 It was empirically observed that the onset stress of sharkskin melt fracture was proportional to the plateau modulus. For polyethylene, it was proposed that the distinct separation of the two modes of the bimodal resin, especially the high content of small chains could cause the significant wall slip, and unusual melt fracture behaviors.5 Based on literature review for the bimodal metallocene PE6, first reported that the addition of low MW component drastically increased the melt flow index. Munoz Escalona et al.7 found that the bimodal metallocene PE in the capillary flow showed more shear thinning behavior than the unimodal PEs of similar MW. Hence, lower viscosities in extrusion flow could be obtained with the bimodal resins. In this report upon to those previous studies, we discuss similar outcome for SBR materials and we correlate them with the characteristic frequency pattern of instabilities. EXPERIMENTAL The experimental setup is based on a Gottfert Rheotester 2000 capillary rheometer with a slit die 0.2 x 3 x 30 mm3. The die is equipped with three high sensitivity piezoelectric pressure transducers, see Fig. 1, and has an aspect ratio of W/H 15, where W and H are Investigation of melt flow instabilities in SBR: influence of MWD and microstructure at in situ pressure fluctuations as detected by capillary rheology Christos K. Georgantopoulos1, Ingo F. C. Naue1, Andrea Causa2, Luciano Garro2, and Manfred Wilhelm1 1Karlsruhe Institute of Technology (KIT) Institute for Chemical Technology and Polymer Chemistry, D 76131 Karlsruhe, Germany 2Pirelli Tyre SpA, Viale Piero e Alberto Pirelli 25, 20126 Milan, Italy ANNUAL TRANSACTIONS OF THE NORDIC RHEOLOGY SOCIETY, VOL. 27, 2019
Christos K Georgantopoulos Ingo F C Naue Andrea Causa Luciano Garro Manfred Wilhelm
4006582
Cyclometalated Complexes of Platinum and Gold with Biological Properties: State of the Art and Future Perspectives.
BACKGROUND The inherent problems accompanying chemotherapy necessitate the development of new anticancer approaches. The development of compounds that can disrupt cancerous cellular machinery by novel mechanisms, via interactions with proteins and non canonical DNA structures (e.g. G quadruplexes) as well as by alteration of the intracellular redox balance, is nowadays focus of intense research. In this context, organometallic compounds of the noble metals Pt and Au have become prominent experimental therapeutic agents. This review provides an overview of the Pt(II) and Au(III) cyclometalated compounds with a chelating ring containing a strong C M s bond to improve the stability of the compounds with respect to ligand exchange reactions and biological reduction. Furthermore, these properties can be easily tuned by modification of either the anionic cyclometalated or the ancillary ligands. Special focus has been set to C^N, C^N^C, C^N^N and C^N^S platinum(II) and gold(III) pincer complexes regarding their synthesis and biological mechanisms of action as anticancer agents. METHODS A structured search of both chemical and medicinal databases for peerreviewed research literature has been conducted. The quality of retrieved papers was appraised using standard tools. The synthesis as well as the chemical and biological properties of the described compounds were carefully reviewed and described. The findings were outlined using a conceptual framework. RESULTS In this review we included 155 papers, the majority originating from high impact papers on the synthesis and biological modes of platinum(II) and gold(III) compounds. Among them, 17 papers were highlighted to give an introduction to the use of Pt and Au compounds with medicinal properties, mainly focussing on coordination compounds. The synthesis and medicinal properties of organometallic compounds of various metals (such as Fe, Ru, Ti) were outlined in 51 papers. These compounds included metallocenes, metallo arenes, metallo carbonyls, metallo carbenes (e.g. N heterocyclic carbenes) and alkynyl complexes. The C^N, C^N^C, C^N^N and C^N^S pincer complexes of platinum( II) (46 papers) and gold(III) (44 papers) were discussed concerning their synthesis, stability and advantages to develop therapeutic compounds. We strove to show the consistent development of C^N, C^N^C, C^N^N and C^N^S platinum(II) and gold(III) pincer complexes regarding their synthesis and biological modes from the early beginnings to the most recent findings. CONCLUSION This review supplies a profound overview of the development of organometallic compounds for medicinal purposes, setting special focus to the synthesis and stability of C^N, C^N^C, C^N^N and C^N^S pincer complexes of platinum(II) and gold(III) and their use as anticancer agents.
Current medicinal chemistry
S Jurgens Fritz E Kuhn Angela Casini