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Pd-catalyzed reaction of olefins is sometimes accompanied by isomerization of the Pd center along the aliphatic chain (chain walking). The chain walking reaction enables synthesis of polyolefins with regulated structure, via C-C bond formation between vinyl or vinylene groups with the carbon atom at a remote position of the olefin monomers. The chain walking reaction also allows synthesis of poly(arylene alkenylene)s by three-component polycondensation of diiodoarenes, non-conjugated dienes and nucleophiles. Polycondensation of diols, diacids, and diamines with long alkylene chain, obtained by chain-walking alkoxycarbonylation, affords long-chain polyesters and polyamides.Chain walking reaction enables synthesis of polyolefins with regulated structure, via C-C bond formation between vinyl or vinylene group with the carbon atom at a remote position of the olefin monomers. The chain walking reaction also allows synthesis of poly(arylene alkenylene)s, and syntheses of diols, diacids, and diamines with long alkylene chain, usable for polycondensation.

Vinylcycloalkanes with 12-, 15-, and 21-membered rings were synthesized from commercially available cycloalkanones or cycloalkyl carboxylic acids derived from malonate and ω-bromo-α-alkenes. Pd complexes with diimine ligands promoted the isomerization polymerization of vinylcycloalkanes with 15- and 21-membered rings to afford polymers having cycloalkylene groups in the main chain. Vinylcycloheneicosane with a 21-membered ring afforded polymers with Mnup to 9700, whereas vinylcycloalkanes with smaller ring sizes (8- and 12-membered rings) yielded oligomers with Mn= 720–1600.

1,1-Disubstituted ethylene derivatives with oxygen functionalities, such as methallyl and isoprenyl ethers and acetate, were employed as comonomers with α-olefins catalyzed by Pd–diimine complexes. A mixture of a chloro(methyl)palladium complex with α-diimine ligand having 2,4,6-trimethylphenyl groups at the coordinated N atoms (I) and Na+B{C6H3(CF3)2-3,5}4–catalyzes the copolymerization of 1-decene with methallyl tert-butyl ether (1) at 0 °C to produce copolymers with comonomer content of 9.7 mol %. Methallyl acetate (2) undergoes copolymerization with 1-decene to afford the corresponding copolymers with comonomer content of 1.0 to 3.3 mol %. Nuclear magnetic resonance analyses of the copolymers of 1-decene with 1and 2revealed that no significant β-alkoxy or β-acetate elimination takes place during the polymerization and that the insertion mode of the comonomer determines the location of the monomer on either the main chain or the terminal of the copolymer. Related compounds, isoprenyl tert-butyl ether (3), isoprenyl acetate (4), and isoprenyl trimethylsilyl ether (5), undergo copolymerization with 1-decene or 1-hexene to afford the corresponding copolymers with comonomer content of 1.0 to 6.2 mol %. The reaction with a higher concentration of a comonomer results in the formation of polymers with higher comonomer content.

Polycondensation reactions of 2,5-dialkoxy-1,4-diiodobenzene with N,N′-ω-dialkenylpyromellitic diimide and N,N′-ω-dialkenyl naphthalenetetracarboxylic diimide in the presence of a Pd(OAc)2–NaOAc catalyst produce six polymers containing the two aromatic groups connected alternatingly by alkenylene spacers. 1H NMR spectrum of a polymer prepared from 2,5-bis(dodecyloxy)-1,4-diiodobenzene and N,N′-(10-undecenyl)pyromellitic diimide (poly(1a-IA)) indicates that the polymerization involves 2,1- and 1,2-insertion of a vinyl group into the Pd–Ar bond in 70:30 selectivity. Matrix-assisted laser deportion/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) spectra of poly(1a-IA) and a polymer from 2,5-bis(dodecyloxy)-1,4-diiodobenzene with N,N′-dialkenyl naphthalenetetracarboxylic diimide (poly(1a-IIA)) contained a series of polymer fragments with Mnup to 4500. Measurement of electrospray ionization MS (ESI-MS) of the polymers revealed formation of cyclic molecules for 1:1 and 2:2 oligomers. Hydrogenations of poly(1a-IA) by using [Ir(cod)(py)(PCy3)]+PF6–(cod = 1,5-cycloctadiene; PCy3= tricyclohexylphosphine) catalyst and of poly(1a-IIA) by a mixture of p-toluenesulfonyl hydrazide (TSH) and tripropylamine (TPA) produce the poly(arylene alkylene)s with saturated spacers in 93% degree of hydrogenation. The absorption spectrum of poly(1a-IA) in CHCl3shows an absorption edge at 410 nm, which is at a longer wavelength than that of a mixture of the monomers (370 nm). Light-scattering measurement of the solution (1.00 mmol L–1) indicates the presence of aggregates with a hydrodynamic radius of 48 nm. The polymers exhibit weak elasticity at room temperature, as determined by dynamic viscoelasticity analysis (DMA), and it becomes negligible on heating to 75–80 °C (polymer with pyromellitic diimide groups) and 110–122 °C (polymer with naphthalenetetracarboxylic diimide groups). The above properties of the polymers are attributed to attractive interaction between the electron-rich alkoxyphenylene and the electron-deficient aromatic diimide groups both in solution and in the solid state.

This article focuses on the synthesis and thermal properties of poly(oligomethylene-cyclopentylene)s and poly(oligomethylene-cyclohexylene)s with regulated regio- and stereochemistry. Pd complexes with diimine ligands promote controlled isomerization polymerization of 4-alkylcyclopentenes to afford polymers with 1,3-trans-cyclopentylene groups and oligomethylene spacers alternating along the polymer chain. Pd complexes with a C2symmetric structure enable isospecific polymerization of 4-alkylcyclopentenes, and the resultant isotactic polymers show liquid-crystalline properties. Cyclopolymerization of 1,6-heptadiene by bis(imino)pyridine Fe and Co catalysts produces poly(ethylene-1,2-cyclopentylene) with cisand trans-stereochemistry, respectively. Synthesis of poly(oligomethylene-1,4-cyclohexylene)s with transor cisstructure can be achieved by Pd-catalyzed isomerization polymerization of alkenylcyclohexanes or methylenecyclohexanes. The polymers with 1,4-trans-cyclohexylene show a high melting point that depends on the length of the oligomethylene spacer in the polymer. The thermal properties of the poly(oligomethylene-cyclopentylene)s and poly(oligomethylene-cyclohexylene)s are compared to those of previously reported polymers with different regio- or stereochemistry. Synthesis and thermal properties of poly(oligomethylene-cyclopentylene)s and poly(oligomethylene-cyclohexylene)s with regulated regio- and stereochemistry are described. Pd complexes with diimine ligands promote controlled isomerization polymerization of 4-alkylcyclopentenes and alkenylcyclohexanes to afford poly(oligomethylene-1,3-cyclopentylene)s with transstructure and poly(oligomethylene-1,4-cyclohexylene)s with transor cisstructure, respectively. Poly(ethylene-1,2-cyclopentylene) with cisand trans-stereochemistry can be obtained by Fe- and Co-catalyzed cyclopolymerization of 1,6-heptadiene, respectively. The thermal properties of the poly(oligomethylene-cyclopentylene)s and poly(oligomethylene-cyclohexylene)s are compared to those of previously reported polymers with different regio- or stereochemistry.

Dipalladium complex with a macrocyclic ligand having two diimine sites catalyzes copolymerization of ethylene with acrylic anhydride to afford the copolymer containing the repeating unit from acrylic anhydride. The obtained copolymer contains the cyclic and acyclic anhydride groups in high content (up to 5.7 mol %) in the main chain. It is contrasted with that the monopalladium complex with the diimine ligand catalyzes the reaction to yield the copolymer having the polar group at the end of branches with lower content (0.8 mol %). Decreased ethylene pressure of the reaction using the dipalladium catalyst results in increase in the polar comonomer unit content. Methanolysis of the copolymer takes place smoothly to give the polymer with both carboxylic acid and ester groups in the polymer chain.

Three fused π-conjugated imidazole compounds were synthesized by acid-catalyzed intramolecular cyclization of arylimidazole derivatives having protected aldehyde group. The optical properties were investigated in detail through the absorption/emission spectra, time-resolved fluorescence spectroscopies, and theoretical calculations.Three fused π-conjugated imidazole compounds were synthesized by the acid-catalyzed intramolecular cyclization of arylimidazole derivatives having the protected aldehyde group. The optical properties were investigated in detail through the absorption/emission spectra, time-resolved fluorescence spectroscopies, and theoretical calculations.

The electric field inside semiconductor devices is a key physical parameter that determines the properties of the devices. However, techniques based on scanning probe microscopy are limited to sensing at the surface only. Here, we demonstrate the direct sensing of the internal electric field in diamond power devices using single nitrogen–vacancy (NV) centers. The NV center embedded inside the device acts as a nanoscale electric field sensor. We fabricated vertical diamond p-i-n diodes containing the single NV centers. By performing optically detected magnetic resonance measurements under reverse-biased conditions with an applied voltage of up to 150 V, we found a large splitting in the magnetic resonance frequencies. This indicated that the NV center senses the transverse electric field in the space-charge region formed in the i-layer. The experimentally obtained electric field values are in good agreement with those calculated by a device simulator. Furthermore, we demonstrate the sensing of the electric field in different directions by utilizing NV centers with different N–V axes. This direct and quantitative sensing method using an electron spin in a wide-band-gap material provides a way to monitor the electric field in operating semiconductor devices.

We report Kelvin probe force microscopy (KPFM) analysis results for a diamond lateral p–n junction diode, which consists of a junction between band conduction and hopping conduction layers, and discuss the potential spatial distribution in the device. KPFM analysis was performed in order to clarify the real device operation mechanism because it can be used to determine surface potential profiles. The lateral p–n junction diode was fabricated using a selective growth technique for heavy phosphorus doping, resulting in hopping conduction layers. In the static state, the KPFM analysis results for the depletion layer width and built‐in potential were thought to be reasonable for a diamond p–n junction diode. In addition, the potential profile was obtained, even during the application of different bias voltages. These results indicate that KPFM analysis is appropriate for diamond devices.

Diamond lateral p–n junctions were fabricated on (111) substrates by selective growth of n‐type diamond around a p‐type layer. We investigated the effects of both the step‐flow growth direction of n‐type diamond and the crystal face of the p‐type sidewalls on the structure and electrical properties of the lateral p–n junctions. The direction of the step‐flow growth clearly influenced the morphologies of the p–n junctions. We also found that the crystal faces of the p‐type sidewalls had an effect on the quality of the lateral p–n junctions. The two facing p–n junctions obtained in this study becomes an n–p–n structure, which could be a key structure for metal‐oxide‐semiconductor field‐effect transistors with an inversion channel.

We succeeded in the formation of a graphene-on-diamond (GOD) structure by the graphitization of a diamond (111) surface. Before the graphitization, atomically flat diamond (111) surfaces were formed by homoepitaxial lateral growth. The graphene layers, which were formed on the atomically flat diamond (111) surfaces horizontally, were observed by cross-sectional high-resolution transmission electron microscopy.

Abstract

Recent advances in polymerization of allyl and diallyl monomers catalyzed by homogeneous Ziegler-Natta catalysts are reviewed. Zirconocene catalysts are effective for copolymerization of ethylene or propylene with Al-masked allyl monomers, as well as homopolymerization of allylsilanes. Phosphine-sulfonate Pd complexes promote the copolymerization of ethylene with various polar allyl monomers, in the absence of a masking agent. Late transition metal catalysts promote stereoselective cyclopolymerization of diallyl monomers having various polar functional groups. The cyclopolymerization of alkyl-substituted diallyl monomers by Pd diimine complexes affords the polymer having alternating oligomethylene and trans-1,2-cyclopentene groups.

We demonstrated high-voltage on/off switching with a vacuum switch by electron emission from a diamond p--i--n diode using negative electron affinity. An equivalent electrical circuit was modeled to evaluate and discuss the performance and potential of switches such as a high-voltage switch for high-voltage dc power grids.

Pd complexes with diimine ligands promoted the controlled cyclopolymerization of 1,6-dienes and 1,6,11-trienes to afford polymers containing 1,2-trans-cyclopentane groups with well-regulated stereochemistry. The polymerization proceeded with quantitative cyclization of the monomer, even under bulk conditions or in copolymerization reactions with ethylene and a-olefins. The polymerization of monomers with oligomethylene spacers yielded polymers with five-membered rings that are accurately distributed along the polymer chain. 4-Alkylcyclopentenes and alkenylcyclohexanes were also polymerized by Pd–diimine complexes to afford polymers with 1,3-trans-cyclopentane groups and 1,4-trans-cyclohexane groups, respectively. Pd complexes with a C2symmetrical structure promoted the isospecific polymerization of 4-alkylcyclopentenes, and the resultant isotactic polymers showed liquid crystalline properties. The mechanism of the polymerization reaction has been revealed.

Pd complexes with diimine ligands promote polymerization of cyclopentenes, 1,6‐dienes, and 1,6,11‐trienes to afford polymers having 1,2‐ or 1,3‐five‐membered ring in every repeating unit. The Pd complexes with C2symmetrical structure catalyze the polymerization reactions to produce polymers with high stereoselectivity. Some of the obtained polymers show characteristic properties such as thermoreversible gelation and liquid crystal formation. Ni complexes bring about the cyclopolymerization of the dienes to afford polymers containing five‐ and/or six‐membered rings in controlled stereochemistry.

A new homologous series of isoflavone-based ethers, 7-(4-bromoalkyloxy)-3-(4′-decyloxyphenyl)-4H-1-benzopyran-4-ones were synthesized and characterized. The mesomorphic properties of all homologues were investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Enantiotropic smectic A (SmA) phase was observed for all homologues. The structure–property study was carried out by comparing the mesomorphic behavior of the homologues with those previously reported analogues. The bromine atom from the alkyloxy side chain of the benzene ring fused to the heterocyclic moiety was found to be capable of changing the mesomorphic properties.

We have investigated the carrier transport of a single‐crystal diamond p+‐i‐n+junction diode fabricated using low‐resistance hopping p+and n+layers, which showed high‐performance diode characteristics. By comparing the diode characteristics of the p+‐i‐n+junction with those of the p+‐n+diode and metal/n+/metal structure, the following results were obtained. The carrier transport of the p+‐i‐n+junction is described using the band conduction caused by the free carriers, although the current transport in both p+and n+layers is mainly by the hopping conduction. The i‐layer in the p+‐i‐n+junction provides a low‐resistance layer for the forward current and a good blocking layer for the reverse current. The contact resistance of the n+/metal layer affects the carrier transport of the p+‐i‐n+diode, which lacks the ohmic property even with the phosphorous concentration around 1020cm−3.

The contact metallization to ntype diamond is a key subject for realizing diamond bipolar devices. We have proposed the selective growth technique using the patterned surface morphology and 〈111〉 directional growth, and have achieved the heavily P doping even on 001 diamond. The objective of this research is to demonstrate the availability of this selective grown ndiamond onto a stack junction diode in order to reduce the series resistance of ntype layer. The pinstructure with and without nlayer were fabricated on 001oriented IIb substrate by plasmaenhanced chemical vapor deposition CVD and conventional lithography technique, and their electrical properties are evaluated by current–voltage and capacitance–voltage measurements. Thanks to the selective grown nlayer, good diode characters are obtained: i a decrease in threshold voltage and ii an increase in forward current without any degradation of reverse characteristics. The results clearly indicate that the selective growth technique is useful for fabricating the 001oriented bipolar junction devices.

We successfully improved a merged diamond diode, namely a Schottkypn diode SPND, which is composed of a fully depleted ntype active layer sandwiched between a highly doped ptype layer and a Schottky metal. According to the analysis of operation mechanisms based on band diagrams, we increased the acceptor concentration in the ptype layer in order to decrease the onresistance RonS, and increased the ntype layer width to reach higher blocking voltage Vblock. Consequently, much lower RonSof 0.03 mΩ cm2and higher Vblockthan those of the previously reported diamond SPND were achieved simultaneously. Thus, we elucidated experimentally that the diamond SPND has no tradeoff relationship between RonSand Vblock, and is suitable for lowloss highpower switching devices.

Cationic Pd complexes, prepared from [PdCl(ArNC12H6NAr)(Me)] and Na[B{3,5(CF3)2C6H3}4] (NaBARF), catalyze the cyclopolymerization of 4,4‐disubstituted 1,6‐heptadienes. The polymers produced contain a trans‐fused five‐membered ring in each repeating unit. NMR spectroscopy and FAB mass spectrometry of the polymers formed indicated that the initiation end of the chain contains either the cyclopentyl group derived from the preformed Pd–monomer complex or a hydrogen atom left on the Pd center by the chain‐transfer reaction. The stable cyclopentylpalladium species are involved in both initiation and propagation steps and undergo isomerization into (cyclopentylmethyl)palladium species followed by the insertion of a CHCH2bond of a new monomer molecule into the PdCH2bond. Copolymerization of 1,6‐heptadiene derivatives with ethylene, catalyzed by the Pd complexes, yields polymers that contain transfive‐membered rings and branched oligoethylene units. Copolymerization of isopropylidene diallylmalonate with 1‐hexene affords a polymer with 26 % diene incorporation. The copolymerization consumes 1‐hexene more readily than isopropylidene diallylmalonate, although gel permeation chromatography and NMR spectroscopy of the polymers produced show the formation of copolymers rather than of a mixture of homopolymers. Polymerization of 1‐hexene initiated with a Pd–barbiturate complex and terminated with 5‐allyl‐5‐hexylpyrimidine‐2,4,6(1H,3H,5H)‐trione/Et3SiH leads to polyhexene with barbiturate moieties at both terminal ends. Addition of 5‐hexyl‐2,4,6‐triaminopyrimidine to a toluene solution of the telechelic poly(1‐hexene) converts the solution into gel.

We successfully fabricated a diamond diode, namely a Schottky p–n diode SPND, which is composed of a fully depleted ntype active layer sandwiched between a highly doped ptype layer and a Schottky metal. The diamond SPND showed a high forward current density over 4000 A cm−2at 6 V with a low builtin voltage ∼1.5 V at room temperature while maintaining a high rectification ratio of ∼1010. Further improvement of the high forward current density characteristics was found at high temperature. The SPND can be realized with higher forward current density than that of conventional diamond Schottky barrier diode, p–n diode, and recently proposed merged diodes, while maintaining the high rectification ratio.

Copolymerization of hepta‐1,6‐diene with ethylene using a cobalt–bis(imino)pyridine complex affords a polymer that contains trans‐1,2‐five‐membered rings in the repeating unit from hepta‐1,6‐diene. The ratio of the repeating units of diene to those of ethylene is controlled from 3: 97 to 50:50, depending on the reaction conditions. Isotope‐labeling reactions reveal that the major chain transfer pathway involves β‐hydrogen elimination of the polymer end formed after ethylene insertion.

The electrical properties of 001 ntype diamond were characterized by measuring the current voltage and capacitance voltage at different temperatures. Clear ntype rectification characteristics were confirmed from Tintype diamond Schottky diodes. From the capacitance properties, the net donor density and Schottky barrier height were experimentally determined to be ∼5.4 × 1017cm–3and ∼4.5 eV, respectively. The electrical activity of doped phosphorus atoms in 001 ntype diamond is discussed in comparison with 111. © 2008 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim

Recent clinical evidences indicate that statins may have beneficial effects on the functional recovery after ischemic stroke. However, the effect of delayed postischemic treatment with statins is still unclear. In the present study, we evaluated the effects of fluvastatin in the chronic stage of cerebral infarction in a rat model.

Summary: Pd complexes prepared from [PdCl(Me)(L)] (L = N-ligands) and NaBARF catalyze the alternating copolymerization of 7‐methylenedibenzo[a,c]bicyclo[4.1.0]heptane with CO to produce the polyketone. Pd complexes with substituted 1,10‐phenanthroline ligands produce the polymer with narrow molecular weight distribution. Addition of 4‐tert‐butylstyrene to the growing polymer after consumption of the initially charged monomer, results in polymer growth to afford an AB‐type block copolyketone. A Pd complex with an optically active bisoxazoline ligand produces the optically active polymer with narrow polydispersity. The addition of DBU to a solution of polyketone converts the cis‐fused six‐membered rings into the trans‐fused rings via epimerization of the CH carbon attached to the carbonyl group.Addition of I to cationic Pd complexes catalyzes the ring-opening copolymerization of the monomer with CO to produce the polyketone, &bond;(C(&dbond;CH2)&bond;C14H10&bond;CO)n&bond; (II).

Seven Pd-complexes with optically active bis[dihydroxazole]-type ligands promote asymmetric alternating copolymerization of 7-methylenebicyclo[4.1.0]heptane with CO, which produces an optically active polyketone, &bond;[C(&dbond;CH2)&bond;CO&bond;C6H10]n&bond;. The reaction under increased CO pressure (> 5 4;atm) affords a polymer that contains monomer units with the cis-cyclohexane-1,2-diyl group almost exclusively. The polyketone exhibits positive or negative optical rotation depending on the Pd-complex. The highest and lowest [α]$\rm{_{{D}}^{25} }$ of the polymer obtained are + 68.9 and − 76.1, respectively. Addition of dibutylcuprate to a solution of the polymer in the presence of Me3SiCl transforms the enone groups of the polymer to silyl enol ether groups, which are ozonized to (silyloxy)oxirane moieties.

The cobalt and nickel complexes promote addition polymerization of substituted methylenecyclopropanes as well as their copolymerization with ethylene to afford the polymers that contain three-membered rings. The homopolymerization of 2-aryl-1-methylenecyclopropane catalyzed by [CoCl2(L)]–MMAO (L = bis(1-iminoalkyl)pyridine ligand) at -40 °C produces the polymers with a narrow molecular weight distribution. The copolymer of ethylene and 2-aryl-1-methylenecyclopropane is also obtained by using the same catalyst. The ratio of the two monomer units varies in the range from 0 to 0.5 depending on the concentration of ethylene and 2-aryl-1-methylenecyclopropane. 13C{1H} NMR spectrum of the alternating copolymer exhibits a single sharp signal for each carbon of the repeating units. Ethylene and 7-methylenebicyclo[4.1.0]heptane also undergo alternating copolymerization to produce the polymer having the C4 repeating unit containing a bicyclic group. Heating the polymer at 130 °C causes ring-opening isomerization to afford the polymer having a C=C double bond in the main chain. Mixtures of [Ni(p-C3H5)Br]2, a diimine ligand, and cocatalysts such as NaBARF and Et2AlCl, initiate the copolymerization of ethylene with 2-aryl-1-methylenecyclopropane to give a random copolymer with a low molecular weight (Mn= 1000–2000).

Alternating copolymerization of 7-methylenebicyclo4,1,0heptane with CO in thf is promoted by catalysts prepared from Pd complexes, PdClMeL L chelating diimine or diamine, and NaBARF BARF BC6H3CF32-3,54−, to produce the polyketone containing enone and 1,2-cyclohexane units. The Pd complexes with Schiff-base type diimines, 2,9-disubstituted 1,10-phenanthroline, and tmen are effective as catalysts to afford the polyketone containing mainly the cis-1,2-disubstituted cyclohexane ring. Polymerization in thf using Schiff-base diimine as the ligand for Pd produces product with a narrow molecular weight distribution MwMn 1.10–1.19. The increase in molecular weight during polymerization and polymer growth caused by addition of new monomer indicates living polymerization. The reaction catalyzed by cationic Pd complexes with 2,2′-bipy and phen, prepared from NaBARF and PdClMeL L 2,2′-bipy, phen in CH3CN, produces polymer that contains both trans- and cis-disubstituted cyclohexane rings in almost equal amounts. Heating of the polymer with cis-disubstituted cyclohexane in the presence of sodium o-chlorophenolate induces epimerization of the polymer into thermodynamically more stable polyketones with trans-disubstituted cyclohexane.

Alternating copolymerization of 7-methylenebicyclo[4,1,0]heptane with CO in thf is promoted by catalysts prepared from Pd complexes, PdCl(Me)L (L = chelating diimine or diamine), and NaBARF (BARF = [B{C₆H₃(CF₃)₂-3,5}₄]−), to produce the polyketone containing enone and 1,2-cyclohexane units. The Pd complexes with Schiff-base type diimines, 2,9-disubstituted 1,10-phenanthroline, and tmen are effective as catalysts to afford the polyketone containing mainly the cis-1,2-disubstituted cyclohexane ring. Polymerization in thf using Schiff-base diimine as the ligand for Pd produces product with a narrow molecular weight distribution (M_w/M_n = 1.10–1.19). The increase in molecular weight during polymerization and polymer growth caused by addition of new monomer indicates living polymerization. The reaction catalyzed by cationic Pd complexes with 2,2'-bipy and phen, prepared from NaBARF and PdCl(Me)L (L = 2,2'-bipy, phen) in CH₃CN, produces polymer that contains both trans- and cis-disubstituted cyclohexane rings in almost equal amounts. Heating of the polymer with cis-disubstituted cyclohexane in the presence of sodium o-chlorophenolate induces epimerization of the polymer into thermodynamically more stable polyketones with trans-disubstituted cyclohexane.

Co2(CO)8 catalyzes the ring-opening copolymerization of propylene oxide with CO to afford the polyester in the presence of various amine cocatalysts. The ¹H and ¹³C{¹H} NMR spectra of the polyester, obtained by the Co2(CO)8–3-hydroxypyridine catalyst, show the following structure &bond;[CH2&bond;CH(CH3)&bond;O&bond;CO]n&bond;. The Co2(CO)8–phenol catalyst gives the polyester, which contains the partial structural unit formed through the ring-opening copolymerization of tetrahydrofuran with CO. The bidentate amines, such as bipyridine and N,N,N',N'-tetramethylethylenediamine, enhance the Co complex-catalyzed copolymerization, which produces the polyester with a regulated structure. Acylcobalt complexes, (RCO)Co(CO)n (R = Me or CH2Ph), prepared in situ, do not catalyze the copolymerization even in the presence of pyridine. This suggests that the chain growth involves the intermolecular nucleophilic addition of the OH group of the intermediate complex to the acyl–cobalt bond, forming an ester bond rather than the insertion of propylene oxide into the acyl–cobalt bond. Co2(CO)8&bond;Ru3(CO)12 mixtures also bring about the copolymerization of propylene oxide with CO. The molar ratio of Ru to Co affects the yield, molecular weight, and structure of the produced copolymer. The catalysis is ascribed to the Ru&bond;Co mixed-metal cluster formed in the reaction mixture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4530–4537, 2002

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No Abstract Supporting information for this article is available on the WWW under http://www.angewandte.com or from the author.

No Abstract Supporting information for this article is available on the WWW under http://www.angewandte.com or from the author.

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Dichlorotitanium {2,2'-methylenebis(6-tert-butyl-4-methylphenolate)} (2) brought about living homopolymerization and copolymerization of cyclic carbonates with 6- and 7-membered rings to give the corresponding polycarbonates with narrow molecular weight distribution. ¹H and ¹³C NMR studies of the polycarbonates obtained by 2 showed the presence of terminal hydroxy groups at both polymer ends, although no signals assignable to a chlorobutyl group or bisphenolate group were observed. ¹H and ¹³C NMR spectroscopy of the polymerization system showed that the cyclic carbonate molecule is coordinated to the titanium complex, whereas the structure of the titanium complex was almost unchanged throughout the polymerization. The polymerization is considered to proceed via a nucleophilic attack of hydroxy groups at the polymer ends on the cyclic carbonates activated by 2.

The copolymerization of oxetane with glutaric anhydride was found to proceed with bulky titanium bisphenolate (1) as the initiator. The 1H NMR spectrum of the produced copolymer shows that the copolymer contains both alternating units and oxytrimethylene units in the polymer main chain. 1was also effective for the copolymerization of oxetane with other cyclic acid anhydrides, affording the corresponding copolymers. With the titanium bisalkolate complex (4), a copolymer rich in alternating sequences was obtained.

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Amphiphilic initiator systems consisting of bulky nucleophiles as propagating species and bulky electrophiles (Lewis acids) as monomer activators bring about high‐speed living anionic polymerization of polar vinylic and heterocyclic monomers to give narrow molecular weight distribution (MWD) polymers.

3,7-Dihydro-8-chlorostyryl-6-phenylethynyl-2-imidazo[1,2- a]pyrazin-3-one ( 5a) prepared from 2-amino-3,5-diphenylethynylpyrazine by condensation with methylglyoxal showed bimodal luminescence in DMSO, i.e., orange-colored luminescence under acidic to neutral conditions and yellow-colored luminescence under basic conditions. The large bathochromic shift of chemiluminescence caused by a styryl group at the 8 position was established by synthesizing 3,7-dihydro-8-styryl-6-phenylethynyl-2-imidazo[1,2- a]pyrazin-3-one ( 5b).

Dinuclear Co and Fe complexes with a double-decker structure supported by macrocyclic ligands having two bis(imino)pyridine and xanthene groups were synthesized. The dinuclear Fe complex catalyzes ethylene oligomerization in the presence of MMAO or Me3Al to give oligoethylene with ethyl and/or propyl branches due to cooperative interaction of two Fe centers.

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Living ring-opening polymerization of 2-alkoxy-1-methylenecyclopropanes has been achieved by -allyl Pd complexes to afford polymers having alkoxy and vinylidene groups in the repeating units. A cyclic dinuclear Pd complex has been synthesized and utilized for the synthesis of cyclic polymers and block copolymers with narrow molecular weight distribution.

Ethylene polymerization initiated by early–late transition-metal complexes afforded a polymer with different branched structures and properties depending on the type of late transition-metal.

The crystal structure of a new complex, trans-[PdCl2(NH=CPh2-?N)2], shows an association of the two molecules via intermolecular N–H···Cl hydrogen bonds. The 1H NMR signal of the N–H hydrogen in CDCl3changes its position depending on the concentration and temperature of the solution.

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