Migration Insertion Research Articles

Synthesis and migration insertion polymerization (MIP) of CpFe(CO)2(CH2)6PPh2(FpC6P) for PFpC6P: macromolecule stability, degradability and redox activity

CpFe(CO)2(CH2)6PPh2 (FpC6P) is synthesized as a monomer for bulk migration insertion polymerization (MIP). Due to the presence of a longer alkyl spacer in FpC6P, intramolecular cyclization reactions, which are observed during the MIP of CpFe(CO)2(CH2)3PPh2 (FpC3P), were completely suppressed under the conditions of the polymerization. The resultant PFpC6P is soluble in common organic solvents and stable enough for GPC analysis. However, the polymer degrades in solution over a few days because the PFpC6P chain is constructed from relatively weak metal coordination bonds. In the presence of an oxidant, e.g. H2O2, degradation of the polymers was accelerated. When the solution was exposed to LED light (wavelength: 400–410 nm), degradation was completed in 20 minutes with CO release first followed by the dissociation of phosphine. DSC analysis indicates that PFpC6P has a Tg of ca. 68 °C, which is lower than that of PFpC3P (ca. 99 °C). TGA analysis reveals that PFpC6P is thermally stable up to 170 °C and leaves a ca. 35.2% char yield at 676 °C after three stages of weight loss. CV data shows that the polymer in DMF has reversible redox activity, with an oxidation peak at 0.74 V and a reduction peak at 0.56 V (relative to a Ag electrode).

Synthesis, Cyclization, and Migration Insertion Oligomerization of CpFe(CO)2(CH2)3PPh2 in Solution

Cyclopentadienyldicarbonyl[(diphenylphosphino)propyl]iron (CpFe(CO)2(CH2)3PPh2, FpP), containing both Fp and phosphine groups, was synthesized as a difunctional monomer for migration insertion polymerization (MIP). FpP underwent either intra- or intermolecular reactions in solution. When a solution with low FpP concentration (ca.1% by weight) was left at 25 °C, FpP was quantitatively converted to the five-membered-ring species 1 via CO release. On the other hand, when a solution at the same low concentration was heated to 70 °C in the dark, an intramolecular migration insertion reaction was promoted, leading to a high conversion of FpP (ca. 70%) to the six-membered cyclic Fp acyl derivatives 2. At the same temperature with an increase in the concentration of FpP to 10% by weight, intermolecular MIR became predominant (ca. 90%) with a low yield of ring molecules (ca. 10%). Solution polymerization of FpP (ca. 20% by weight) was therefore performed at 70 °C, which generated both THF-soluble and -insoluble ma...

1,6-Carbene Transfer: Gold-Catalyzed Oxidative Diyne Cyclizations

In the presence of a gold catalyst an unprecedented oxidative cyclization of diynes takes place. The reaction cascade is initiated by an oxygen transfer from a N-oxide onto a gold-activated alkyne. The formed α-oxo carbene is transferred across the second alkyne yielding a stabilized vinyl carbene/cation. Alkyl migration or sp(3)-CH insertion then terminates the catalytic cycle by formation of highly substituted functionalized indenones. A 1,6-carbene shift could be supported by the oxidation of the vinyl carbene. This protocol represents an attractive alternative to procedures which are based on the metal-catalyzed decomposition of hazardous, not easily accessible, diazo compounds.

FRI0038 Differential in vitro migration of synovial fibroblasts from diseased and healthy joints

BackgroundActivated synovial fibroblasts (SF) are key mediators of inflammation and joint destruction in rheumatoid arthritis (RA), their activated phenotype has been likened to that of cancer associated fibroblasts. Two major...

Migration Insertion Polymerization: A Route to Metal-Containing Polymers

Migration Insertion Polymerization: A Route to Metal-Containing Polymers

From Sex to Gender: The Feminisation of Migration and Labour-Market Insertion in Spain and Portugal

The aim of this article is to study the feminisation and masculinisation of migration and the insertion of the migrant population into the labour market in Spain and Portugal from the perspective of gender. Rather than focusing on the appearance of the demand for migrant labour in social reproduction work, we analyse the situation of both men and women in highly feminised and masculinised activities by studying the impact each exerts on the other, and the way in which this conditions the gender breakdown of the migrant population. We provide a historical view of the work of migrants in the care and cleaning sectors, comparing it with male migrant employment—mostly in construction—and analysing the gendered breakdown of migrant communities. We argue that, in contrast to the generally accepted discourse on the international scene, there has not been a steady evolution in the feminisation of migrant labour in Spain and Portugal. Instead, the presence of migrant women on the labour market fluctuates in accordance with a specific set of variables: welfare state and care regimes, immigration policies, historical links influencing the national origin of migrants, the housing situation, labour markets and the respective economic situations in the construction industry and in domestic and care work.

Migration Insertion Polymerization (MIP) of Cyclopentadienyldicarbonyldiphenylphosphinopropyliron (FpP): A New Concept for Main Chain Metal-Containing Polymers (MCPs)

We report a conceptually new polymerization technique termed migration insertion polymerization (MIP) for main chain metal-containing polymer (MCP) synthesis. Cyclopentadienyldicarbonyldiphenylphosphinopropyliron (FpP) is synthesized and polymerized via MIP, resulting in air stable poly(cyclopentadienylcarbonyldiphenylphosphinobutanoyliron) (PFpP) displaying narrow molecular weight distribution. The backbone of PFpP contains asymmetric iron units connected by both phosphine coordination and Fe-acyl bonds, which is representative of a new type of polymer. Furthermore, PFpP is tested to be soluble in a wide range of organic solvents and shown to possess reactive Fp end groups. PFpP amphiphiles have therefore been prepared via an end group migration insertion reaction in the presence of oligoethylene phosphine.

Regioselectivity of styrene carbonylation in the presence of palladium(II) complexes

The influence of a catalyst on regioselectivity of styrene carbonylation in ionic liquids catalyzed by palladium(II) complexes was studied. The mechanism of the migration insertion of styrene at the palladium-hydrogen bond determining the regioselectrivity of the whole reaction, which is treated as electrophilic addition to the multiple bond of styrene, was studied. A study of the structure of intermediate complexes formed at this stage was performed using the B3LYP method of density functional theory.

A novel flow cytometry‐based assay to study leukocyte–endothelial cell interactions in vitro

Interactions between peripheral blood mononuclear cells (PBMC) and the endothelium critically determine vascular repair and reparative angiogenesis, but also pathological processes, such as atherosclerosis. Current methodology to study these interactions mostly regards PBMC as a homogenous population or it restricts its focus on individual cell types and therefore does not appreciate the differential behavior of individual PBMC subpopulations, which synergize or antagonize each other to obtain the overall effect. We therefore developed a flow cytometry-based in vitro assay to assess multiple parameters of interaction between several individual populations of PBMC and an endothelial monolayer. Freshly isolated, unlabelled human PBMC were left to adhere to or transmigrate through a monolayer of fluorescence-labeled human aortic endothelial cells grown to confluence on the filter membrane of sterile transwell migration inserts. Monocyte chemoattractant protein-1 (MCP-1) was applied as a chemoattractant to the lower compartment of the migration chamber. After 6 h, transmigrating PBMC were harvested from the lower compartment, while nonadherent and adhering cell populations were harvested from the upper compartment by sequential washing/detachment. All three cell fractions were then individually stained with fluorescence-labeled monoclonal antibodies and analyzed by flow cytometry. Quantification was achieved by the usage of counting beads. Endothelial cells were separated from PBMC during the analysis by a multiparametric gating strategy. Using the newly established assay, we observed distinct migration patterns for inflammatory CD14(hi) CD16(neg) and resident CD16(pos) monocytes. These cell types differed in their basal adhesion and transmigration patterns as well as their responses to the CCR2 ligand MCP-1. This assay allows for the parallel study of interactions between multiple individual leukocyte populations and an endothelial layer. Several readouts can be derived from the same experiment, like the composition of adhering and transmigrating cell fractions or the individual adhesion/migration behavior of several distinct cell types.

Effect of the ligand nature on the regioselectivity of the styrene carbonylation in the presence of palladium(II) complexes

226 This study dealt with the influence of halide ligands on the regioselectivity of the styrene carbonylation reaction in ionic liquids without phosphine ligands. The stage of migration insertion of styrene into the Pd–H bond in the hydride π complex [HPdX(sty rene)L] (II; X = Cl, Br) was modeled. The energies of the most important reaction states were considered, and the effect of the acidity of hydride palladium π complexes with styrene on the yield of complexes was examined.

A novel PPGA-based clustering analysis method for business cycle indicator selection

A new clustering analysis method based on the pseudo parallel genetic algorithm (PPGA) is proposed for business cycle indicator selection. In the proposed method, the category of each indicator is coded by real numbers, and some illegal chromosomes are repaired by the identification and restoration of empty class. Two mutation operators, namely the discrete random mutation operator and the optimal direction mutation operator, are designed to balance the local convergence speed and the global convergence performance, which are then combined with migration strategy and insertion strategy. For the purpose of verification and illustration, the proposed method is compared with the K-means clustering algorithm and the standard genetic algorithms via a numerical simulation experiment. The experimental result shows the feasibility and effectiveness of the new PPGA-based clustering analysis algorithm. Meanwhile, the proposed clustering analysis algorithm is also applied to select the business cycle indicators to examine the status of the macro economy. Empirical results demonstrate that the proposed method can effectively and correctly select some leading indicators, coincident indicators, and lagging indicators to reflect the business cycle, which is extremely operational for some macro economy administrative managers and business decision-makers.

Synthesis of electron-rich platinum centers: Platinum 0(carbene)(alkene) 2 complexes

The synthesis and molecular structure of the zero-valent platinum-mono-carbene-bis-alkene complexes [Pt 0(NHC)(dimethyl fumarate) 2] (NHC = 1,3-dimesityl-imidazol-2-ylidene ( 1a); 1,3-dimesityl-dihydroimidazol-2-ylidene ( 2a); diphenyl-dihydroimidazol-2-ylidene ( 2b) are described. Two routes have been evaluated for the synthesis of 1a and 2a, involving reaction of a zero-valent platinum compound either with an isolated carbene ligand, or with an in situ generated carbene ligand. The in situ method proved to be easier and gave similar yields of about 50% after crystallization. Attempts have been made to synthesize similar compounds with N-phenyl and N-alkyl groups, of which the latter met with little success. However, (1,3-diphenyl-dihydroimidazol-2-ylidene)-bis(η 2-dimethyl fumarate) platinum(0) ( 2b) could be obtained in 49% yield, after crystallization, from the appropriate Wanzlick dimer. Compound 1a reacts with H 2 and D 2 in sequences of oxidative addition, migration–insertion involving dimethyl fumarate, and reductive elimination to form neutral hydrido platinum (II) carbene complexes, probably containing a metallacyclic (R)–C O … Pt unit.

Late-Transition-Metal Complexes with Bisazaferrocene Ligands for Ethylene Oligomerization

Herein we report the synthesis, characterization, and ethylene polymerization properties of novel C2-symmetric and unsymmetric bisazaferrocene complexes with late-transition-metal Ni(II) and Pd(II). In the designed complexes, the two sp2-hybridized nitrogen atoms in the azaferrocene rings coordinate to the transition metals with the azaferrocene architecture presenting pentamethyl or pentaphenyl cyclopentadiene (Cp* or Cp°) rings above and below the coordination plane for the purpose of preventing the associative chain transfer processes of ethylene from the axial faces. The Ni(II) and Pd(II) complexes were prepared and characterized by mass spectrometry (MS), 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, and single-crystal X-ray crystallography. Upon activation with methylaluminoxane (MAO), the bisazaferrocene complexes with NiBr2 (2a) and PdCl2 (2b) showed very low activities toward ethylene polymerization. Well-defined preactivated bisazaferrocene-Pd(II) complexes (5 and 6) exhibited relatively high thermal stability for ethylene oligomerization: for example, complex 5 remains active in ethylene oligomerization at temperatures up to 120 °C. They have moderate activities in ethylene polymerizations to form relatively low molecular weight oligomers. The polyethylene oligomers formed have branching densities ranging from 20 to 60 branches/1000 carbons. To overcome the difficulty encountered in the synthesis of complex 6, a novel route was developed to make Pd(Me)Cl complexes with various dinitrogen ligands by in situ ligand substitution reaction. Finally, to gain mechanistic insight into the low reactivity of the bisazaferrocene-PdII complexes (5 and 6) as compared to their α-diimine counterparts, kinetic studies were undertaken to measure the energetic barriers for the first methyl migration and subsequent ethylene consumption. It was found that the insertion barriers (ΔG⧧) for both the first methyl migration and subsequent ethylene insertion for complex 5 were about 2−3 kcal/mol higher than the values for the α-diimine counterparts, which corresponds to a 2-order difference in the rate of polymerization. Variable-temperature experiments further revealed that the higher ethylene insertion barrier for the bisazaferrocene-Pd(II) complexes arises from both higher activation enthalpy (ΔH⧧) and smaller activation entropy (ΔS⧧).

A New Technique for Retrieval or Repositioning of Damaged or Migrated Silicone Punctal Plugs

A new technique for retrieval or repositioning of migrated or malpositioned silicone punctal plugs is described. Malposition is known to occur secondary to either spontaneous migration or forceful insertion. This technique offers considerable advantages over current treatment options including simplicity and minimal trauma to both the plug and the nasolacrimal system.

Propylene polymerization with Ph2C(3-RCp)(Flu)ZrCl2 [R = Me, i-Pr, PhCH2, Me3Si] catalysts activated with MAO and Me2PhNH·B(C6F5)4/i-Bu3Al

Propylene polymerization was conducted with Ph 2 C(R-Cp)(Flu)ZrCl 2 [R = Me, i-Pr, PhCH 2 , Me 3 Si] catalysts in combination with methylaluminoxane (MAO) and dimethylanilinium tetrakis(pentafluorophenyl)borate (Me 2 PhNH. B(C 6 F 5 ) 4 ) as cocatalyst; the dependence of the stereoregularity of poly(propylene) on cocatalysts and bulkiness of the substituents in β-position of the cyclopentadienyl ligand was studied. Methyl and i-propyl substituted metallocene catalysts produce hemi-isotactic poly(propylene). These results are in good agreement with the results of the isopropylidene bridged metallocene analogue. The benzyl substituted metallocene catalyst produces syndiotactic poly(propylene) regardless of the cocatalyst. This means that this substituent group does not affect migration insertion of propylene. Stereoregularity of poly(propylene) obtained with diphenylmethylidene(3-trimethylsilylcyclopentadienyl)(fluorenyl)zirconium dichloride (Ph 2 C(Me 3 SiCp)(Flu)ZrCl 2 ) as a catalyst was significantly influenced by the cocatalyst. Me 2 PhNH. B(C 6 F 5 ) 4 /triisobutylaluminium(i-Bu 3 Al) produces poly(propylene) with 65% racemic and 23% meso pentads at 40°C, whereas the MAO activated catalyst produces isotactic rich poly(propylene). Fractionation experiments indicated that Me 2 PhNH. B(C 6 F 5 ) 4 /i-Bu 3 Al forms two active sites, one of them being the same as that of the MAO activated catalyst, the other one producing syndiotactic rich poly(propylene).

Bis-Allylic Hydroxylation of Polyunsaturated Fatty Acids by Hepatic Monooxygenases and Its Relation to the Enzymatic and Nonenzymatic Formation of Conjugated Hydroxy Fatty Acids

[14C]Linoleic acid was incubated with phenobarbital-induced rat liver microsomes and formation of cis-trans-conjugated hydroxy fatty acids was investigated. 13-Hydroxy-9Z,11E-octadecadienoic acid (13-HODE), 9-hydroxy-10E,12Z-octadecadienoic acid (9-HODE), and three novel metabolites were identified, viz. 1 1-hydroxy-9Z,12Z-octadecadienoic acid (li-HODE), 8-HODE, and14-HODE. 11-HODE (59% R), the main product, was unstable and converted to 9(R, S)-HODE and 13(R, S)HODE in acidic media. All metabolites contained oxygen from O2. Experiments under oxygen-18 gas showed that 13-HODE and 9-HODE contained equal or less amounts of oxygen-18 than the other metabolites. In the former case, 9-HODE and 13-HODE were formed with stereo-selectivity (80-82% R). [11S-2H]Linoleic acid was metabolized to 13R-HODE with loss of deuterium (24% 2H) and to 9R-HODE with deuterium retention (95% 2H), while [11R-2H]linoleic acid was metabolized to 13R-HODE that largely retained the label (71% 2H) and to 9R-HODE that lost most of the label (22% 2H). These data indicated that P450 catalyzed abstraction of the pro-R hydrogen at C11, double bond migration and suprafacial oxygen insertion at C9 to give 9R-HODE, while abstraction of the pro-S hydrogen at C11, followed by double bond migration and oxygen insertion, yielded 13R-HODE. Hepatic microsomes of the cynomolgus monkey metabolized 18:2n-6 as above and 20:4n-6 to 13-hydroxyeicosatetraenoic acid, likely formed in analogy with li-HODE. In summary, one mechanism in the biosynthesis of cis-trans-conjugated hydroxy fatty acids by P450 involves suprafacial hydrogen abstraction and oxygen insertion. In addition, hydrolysis of the unstable bis-allylic hydroxy metabolites may contribute to the formation of conjugated hydroxy fatty acids.

Formation of acetylcholine receptor clusters in chick myotubes: migration or new insertion?

Experiments were performed to study the feasibility of two mechanisms of acetylcholine receptor (ACHR) accumulation in chick myotubes: diffusion and trapping of previously dispersed surface receptors and localized insertion of new receptors at accumulation sites. Fluorescence photobleaching recovery (FPR) measurements indicated that the majority of diffusely distributed ACHRs in chick myotube membranes were mobile whereas nearly all receptors within high density clusters were effectively immobile. Unlike previous reports, two rates of ACHR movement characterized the mobile population. Moreover, we found that the estimated diffusion coefficient depended critically on the objective (spot size) used to assay recovery from bleaching. Implications of this finding for mechanisms of receptor immobilization are discussed. Extracts of chick brain, known to increase the number of surface receptors, did not alter receptor mobility. Extracts of Torpedo electric organ that increase the number of receptor aggregates, decreased the mobile fraction of ACHRs. Simulations of the diffusion and trapping mechanism indicated that captured receptors should congregate around the periphery of a receptor patch during the first hour after they were inserted into the membrane. However, newly inserted ACHRs were found to be located centrally within receptor patches under neurites, and this was not consistent with an exclusive diffusion-trapping mechanism. We also studied the mobility of ACHRs near points of contact made by cholinergic growth cones. The rate of receptor movement was increased in the vicinity of growth cones, but the magnitude of this effect was small.

Termination reactions of C5–C12cycloalkyl radicals and carbenes

Reactions of C5–C12 cycloalkyl radicals and carbenes produced during radiolysis, vacuum-u.v. photolysis, and decomposition of cycloalkanone p-tosylhydrazones were investigated. The disproportionation to combination ratios of radicals are ca. 1 and agree with the ratios of linear secondary radicals. The disproportionation of smaller cycloalkyl radicals yields cis-cycloalkenes and cycloalkanes; from C9 and C10cis- and trans-cycloalkenes and cycloalkanes and from C11 and C12trans-cycloalkenes and cycloalkanes are produced. Both atoms of H2 given off in the elimination reaction from excited cycloalkane molecules originate from the same carbon atom and in this process carbenes are formed. Rearrangement of small (C5, C6) and large (C11, C12) cycloalkylcarbenes in the solvent of the given cycloalkane occurs by 1,2-hydrogen migration. C7–C10 carbenes rearrange both by hydrogen atom migration and transannular insertion.

Alumina: Catalyst and support: XXXI. Dehydrogenation of 2-phenylbutane-2-C 14

2-Phenylbutane-2-C 14 was synthesized and submitted to dehydrogenation in the presence of a “nonacidic” chromia-alumina catalyst in a flow system at 487 °. Skeletal rearrangement occurred to yield n-butylbenzenes and n-butenylbenzenes. After a selective hydrogenation the n-butylbenzene fraction consisted of almost equal amounts of 1-phenylbutane-1-C 14 and 1-phenylbutane-2-C 14. The skeletal isomerization is explained by a radical mechanism involving phenyl migration and methyl carbon insertion (1,2-vinyl migration). The sec-butylbenzene fraction, especially at the beginning of the experiment, retained the radiocarbon in its original position.