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Ethylene polymerization using (arylimido)(aryloxo)vanadium complexes of type, VCl2(N-2,6-Me2C6H3)(OAr) [OAr=O-2,6-Me2C6H3 (1), O-2,6-iPr2C6H3 (2), O-2,6-Ph2C6H3 (3), and O-2,6-tBu2-4-MeC6H2 (4)], has been explored in the presence of MAO. The substituents on the aryloxo ligand were found to play an essential role for the catalytic activity, and effect of both Al/V molar ratio and temperature for the activity depended upon the substituents. High catalytic activity was observed especially at low temperature of 0 °C when 3 was used as the catalyst precursor, whereas 1 showed the highest activity at 25 °C. However, 2–MAO catalyst showed extremely low activity for styrene polymerization. [Copyright &y& Elsevier]

Ethylene slurry polymerization using Cp*TiCl 2 (O-2,6- i Pr 2 C 6 H 3) in the presence of supported solid MAO cocatalysts proceeded without decrease in the activity compared to the homogeneous system; unique characteristics by 1 in the copolymerization with 1-hexene (activity, comonomer incorporation) observed in the homogeneous system have also been preserved. [Display omitted] • Supported MAO cocatalysts for efficient ethylene (co)polymerization. • Control of morphology in olefin polymerization using supported molecular catalysts. • Efficient ethylene copolymerization by supported Cp*TiCl 2 (O-2,6- i Pr 2 C 6 H 3) catalyst. Ethylene slurry polymerization using Cp*TiCl 2 (O-2,6- i Pr 2 C 6 H 3) in the presence of supported solid MAO cocatalysts proceeded without decreasing in the activity compared to the homogeneous system, affording polymers with controlled shape replicated from the original support. Unique characteristics by 1 in the ethylene/1-hexene copolymerization observed in the homogeneous system (high catalytic activity, efficient 1-hexene incorporation, temperature dependence) have also been preserved in this catalysis, affording high molecular weight poly(ethylene- co -1-hexene)s with unimodal molecular weight distributions as well as with high 1-hexene contents. [ABSTRACT FROM AUTHOR]

Die Synthese von Polyarylenvinylenen mit verschiedenen Endgruppen wird von K. Nomura et al. in der Zuschrift auf S. 5372 ff. beschrieben. Die endfunktionalisierten Poly(9,9′‐dialkylfluorenvinylen)‐Derivate (EF‐PFVs) wurden durch 1) die Synthese von EF‐PFVs mit Vinyl‐Enden durch Molybdän‐katalysierte acyclische Dienmetathese und Terminierung mit einem Aldehyd und 2) anschließende Olefin‐Metathese mit einer Vinyl‐Einheit sowie Wittig‐Kupplung mit einem weiteren Aldehyd erhalten. [ABSTRACT FROM AUTHOR]

The synthesis of high-molecular-weight ( M n up to 62,000 g/mol) polyesters has been achieved by acyclic diene metathesis (ADMET) polymerization of α,ω-dienes prepared from biobased bis(undec-10-enoate) and diols [ethylene glycol ( M1 ), propylene glycol ( M2 ), 1,9-nonanediol ( M3 ), 1,4-benzenedimethanol ( M4 ), and hydroquinone ( M5 )] using ruthenium-carbene catalysts. Replacement of the solvent during the ADMET polymerization was effective for obtainment of the high-molecular-weight polymers (expressed as P1 - P5 ). The melting temperatures ( T m ) in the resultant polyesters were dependent upon the diol (middle) segment employed, and the polymer prepared from M5 exceeded 100 °C (a T m value of 122.5 °C). The polymerization of M3 and M4 in the presence of 1,4- cis -diacetoxy-2-butene (DAB, as the chain transfer agent) afforded the telechelic polyesters [ P3(OAc) 2 and P4(OAc) 2 , respectively] containing acetoxy end groups exclusively. The resultant polymers containing hydroxy group termini [ P3(OH) 2 and P4(OH) 2 ], prepared by the selective deprotection of the acetoxy end groups, were treated with AlEt 3 followed by addition of ε-caprolactone to afford the ABA-type triblock copolymers exclusively, through a living ring-opening polymerization. The depolymerization (hydrolysis) under basic conditions (NaOH aqueous solution) of P3 was explored., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Synthesis of high molecular weight polyesters prepared by acyclic diene metathesis (ADMET) polymerization of bis(undec-10-enoate) with isosorbide ( M1 ), isomannide ( M2 ), and 1,3-propanediol ( M3 ) and the subsequent hydrogenation have been achieved by using a molybdenum-alkylidene catalyst. The resultant polymers ( P1 ) prepared by the ADMET polymerization of M1 (in toluene at 25 °C) possessed high M n values ( M n = 44400-49400 g/mol), and no significant differences in the M n values and the PDI ( M w / M n ) values were observed in the samples after the hydrogenation. Both the tensile strength and the elongation at break in the hydrogenated polymers from M1 ( HP1 ) increased upon increasing the molar mass, and the sample with an M n value of 48200 exhibited better tensile properties (tensile strength of 39.7 MPa, elongation at break of 436%) than conventional polyethylene, polypropylene, as well as polyester containing C 18 alkyl chains. The tensile properties were affected by the diol segment employed, whereas HP2 showed a similar property to HP1 .

A catalytic chemical upcycling methodology for polyesters has been developed. Commodity polyesters, such as polyethylene terephthalate (PET), are depolymerized with morpholine by using a Cp*TiCl 3 catalyst under ambient pressure without any additives, which provides morpholine amides exclusively. The method can also apply to other polyesters, polybutylene terephthalate (PBT), polyethylene adipate (PEA), polybutylene adipate (PBA), and polybutylene succinate (PBS), as well as an actual PET waste of a 50 g postconsumer beverage bottle. The product, morpholine amide, is a versatile building block in organic chemistry, and the synthetic utility has thus been demonstrated by further transformations, such as hydrolysis, selective reductive conversions, and Grignard reaction., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Synthesis of bottlebrush polymers (BBPs) and block copolymers by Z -/ E -specific living ring-opening metathesis polymerization (ROMP) of N-substituted-norbornene-2,3-dicarboximides containing long alkyl chains ( n -octadecyl, n -tetradecyl, etc.) has been attained by the vanadium(V)-alkylidene catalysts V(CHSiMe 3 )(ArN)[OC(CF 3 ) 3 ](PMe 3 ) 2 [Ar = 2,6-Cl 2 C 6 H 3 ( 1 ), C 6 F 5 ( 2 )] and V(CHSiMe 3 )(2,6-F 2 C 6 H 3 N)(OC 6 Cl 5 )(PMe 3 ) 2 ( 3 ). The ROMPs using 1 afforded the BBPs with exclusive Z selectivity (98 to >99% cis ) even at high temperature (up to 80 °C) in the presence of PMe 3 , whereas the ROMPs using 3 gave the BBPs with high E selectivity (90% trans ). These ROMPs proceeded in a living manner (even at 80 °C using 1 ), affording various (amphiphilic) block copolymers while maintaining high E / Z selectivity. The resultant Z - and E -selective BBPs especially prepared from N -( n -octadecyl)norbornene-2,3-dicarboximide possessed different melting temperatures due to different degrees of interpolymer alkyl side chain interaction (side chain crystallization).

Acyclic diene metathesis (ADMET) polymerization of an α,ω-diene monomer of bis(undec-10-enoate) with isosorbide ( M1 ) using a RuCl 2 (IMesH 2 )(CH-2-O i Pr-C 6 H 4 ) ( HG2 , IMesH 2 = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) catalyst and conducted at 50 °C (in vacuo) in ionic liquids (ILs) afforded higher-molecular-weight polymers ( P1 , M n = 32 200-39 200) than those reported previously ( M n = 5600-14700). 1- n -Butyl-3-methyl imidazolium hexafluorophosphate ([Bmim]PF 6 ) and 1- n -hexyl-3-methyl imidazolium bis(trifluoromethanesulfonyl)imide ([Hmim]TFSI) were suitable as effective solvents among a series of imidazolium salts and the pyridinium salts. The polymerization of α,ω-diene monomers of bis(undec-10-enoate) with isomannide ( M2 ), 1,4-cyclohexanedimethanol ( M3 ), and 1,4-butanediol ( M4 ) in [Bmim]PF 6 and [Hmim]TFSI also afforded the higher-molecular-weight polymers. The M n values in the resultant polymers did not decrease even under the scale-up conditions (300 mg to 1.0 g scale, M1 , M2 , and M4 ) in the polymerizations in [Hmim]TFSI; the subsequent reaction of P1 with ethylene (0.8 MPa, 50 °C, and 5 h) gave oligomers (proceeded via depolymerization). Tandem hydrogenation of the resultant unsaturated polymers ( P1 ) in a [Bmim]PF 6 -toluene biphasic system upon the addition of Al 2 O 3 (1.0 MPa H 2 at 50 °C) gave the corresponding saturated polymers ( HP1 ), which waswere isolated by a phase separation in the toluene layer. The [Bmim]PF 6 layer containing the ruthenium catalyst could be recycled without a decrease in the activity/selectivity of the olefin hydrogenation at least eight times., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Ethylene copolymerizations with 2-methyl-1-pentene, 1-dodecene (DD), vinylcyclohexane (VCH), [Me 2 Si(C 5 Me 4 )(N t Bu)]TiCl 2 ( 1 ), Cp*TiMe 2 (O-2,6- i Pr 2 -4-RC 6 H 2 ) [R = H ( 2 ), SiEt 3 ( 3 )]-borate, and [A(H)] + [BAr 4 ] - [Ar = C 6 F 5 ; A(H) + = N + (H)Me( n -C 18 H 37 ) 2 , N + (H)(CH 2 CF 3 )( n -C 18 H 37 ) 2 , HO + ( n -C 14 H 29 ) 2 ·O( n -C 14 H 29 ) 2 , HO + ( n -C 16 H 33 ) 2 ·O( n -C 16 H 33 ) 2 ; Ar = C 10 F 7 , A(H) + = HO + ( n -C 14 H 29 ) 2 ·O( n -C 14 H 29 ) 2 ( B5 ), N + (H)(CH 2 CF 3 )( n -C 18 H 37 ) 2 ] catalyst systems conducted in methylcyclohexane (MCH) exhibited better comonomer incorporation than those conducted in toluene (in the presence of methylaluminoxane (MAO) or borate cocatalysts). The activity was affected by the borate cocatalyst and 1 , 3 - B5 catalyst systems in MCH and showed the highest activity in the ethylene copolymerizations with VCH and DD., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Fatty acid ethyl esters (FAEEs) derived from vegetable oils and ethanol are promising bio-based chemicals for various applications such as biofuel, monomers for polyesters, and fine chemicals. However, the limited conversion and yield are obtained in the conventional methods due to low boiling point of ethanol that thus requires conducting the reaction at low temperature. This work demonstrates high yield of FAEEs from soybean, rice bran and palm oil with ethanol by performing the transesterification at high temperatures of 150-200°C by using CaO catalyst in a high pressure reactor. The results demonstrate the complete reaction for all vegetable oils with low ethanol to oil molar ratio of 6:1 and 1 wt.% CaO catalyst. Higher reaction temperature results in faster reaction while keeping high conversion of ≥ 99.0%. The unsaturated components in FAEE products are consistent with their original fatty acid chain. Moreover, the high conversion can be achieved even in the reaction conducted with low ethanol to oil molar ratio of 4.5:1 and 0.5 wt.% CaO catalyst at 180 °C in the palm oil transesterification. The catalyst can be reused for at least 3 times with the conversion higher than 94.0%. In addition, the activation energy (E a ), enthalpy of activation (ΔH ‡ ), entropy of activation (ΔS ‡ ) and Gibbs free energy of activation (ΔG ‡ ) are also obtained.

A series of oligo(thiophene)-modified "soluble" star-shaped ring-opening metathesis polymerization (ROMP) polymers were prepared by sequential living ROMP of norbornene and a cross-linking agent using a molybdenum-alkylidene catalyst, followed by Wittig-type coupling for termination with oligo(thiophene) carboxaldehydes. The resultant star-shaped ROMP polymers displayed unique emission properties affected by the core size and arm repeat units as well as the kind of oligothiophene coated. The effects of the thiophene groups on photophysical properties of star-shaped/linear polymers were studied via time-resolved fluorescence spectroscopy. Fluorescence lifetimes were determined in THF as 400, 640, 730, and 820 ps for Star 3TPh , Linear 3TPh , Star 4T, and Linear 4T , respectively. A significant enhancement of the nonradiative rate constants k nr in the star-shaped polymers results in relatively lower fluorescence quantum yields and shorter fluorescence lifetimes compared to the corresponding linear polymers., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

A series of ethylene copolymers with long-chain α-olefins [LCAOs, 1-dodecene (DD), 1-tetradecene (TD), 1-hexadecene (HD)] and various LCAO contents were prepared, and their thermal properties, including effects of LCAO content and side chain length, were explored. The Cp*TiCl 2 (O-2,6- i Pr 2 -4-SiEt 3 -C 6 H 2 )-MAO catalyst system afforded rather high-molecular-weight copolymers with unimodal molecular weight distributions and uniform compositions (confirmed by DSC thermograms). In addition to the melting temperatures ( T m values) corresponding to the so-called main chain crystallization (samples with low LCAO contents, the T m value decreased upon increasing the LCAO content) and the side chain crystallization [polymer samples with high LCAO contents, by intermolecular interaction of side chains as observed in poly(DD), poly(TD), and poly(HD)], the other T m value was observed, especially in poly(ethylene- co -HD)s (assumed to be due to co-crystallization of the branch and the main chain through an interaction of the main chain and the long side chains). The presence of another crystalline phase in poly(ethylene- co -HD)s was also suggested by a wide-angle X-ray diffraction (WAXD) analysis. These T m values in poly(ethylene- co -TD)s and poly(ethylene- co -DD)s with rather high TD or DD contents were affected by the heating conditions in the measurement of DSC thermograms (5 or 10 °C/min), suggesting that the driving force for formation of the crystal packing (observed as T m ) is weak and affected by the alkyl side chain lengths., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Transesterification of ethyl-10-undecenoate (derived from castor oil) with 1,4-cyclohexanedimethanol over a recyclable Cu-deposited V 2 O 5 catalyst afforded 1,ω-diene, the corresponding cyclohexane-1,4-diylbis(methylene) bis(undec-10-enoate), a promising monomer for the synthesis of biobased polyesters, in an efficient manner. Deposition of Cu plays an important role in proceeding the reaction with high selectivity, and both the activity and the selectivity are preserved for five recycled runs by the addition of the substrates. The present catalyst was effective for transesterification with other alcohols, especially primary alcohols, demonstrating a possibility of using this catalyst for efficient conversion of plant oil to various fine chemicals., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Time-resolved fluorescence anisotropy measurements were performed on three-branched star-shaped polymers, based on precisely synthesized poly(9,9-di- n -octyl-fluorene vinylene)s containing C 6 F 5 end groups. The star-shaped polymers showed identical fluorescence spectra, fluorescence lifetimes, and quantum yields to those of the reference single-chain oligomer. However, a rapid fluorescence anisotropy decay was observed in two kinds of star-shaped polymers, while such decay was not seen in the corresponding single-chain oligomer. On the basis of the analysis using an incoherent hopping model, the observed rapid anisotropy decay is attributable to energy hopping processes between branches within a single polymer species, and its rate was deduced to be ca.100 ps depending upon the core part.

Remarkable effects of SiMe 3 and SiEt 3 para-substituents in the phenoxide-modified half-titanocenes, Cp*TiCl 2 (O-2,6- i Pr 2 -4-R-C 6 H 2 ) [R=SiMe 3 (6), SiEt 3 (7)], toward the catalytic activities in ethylene copolymerizations with 2-methyl-1-pentene, 1-decene, 1-dodecene and with 9-decen-1-ol (DC-OH) have been demonstrated. The activities by 6, 7 at 50 °C showed higher than those conducted at 25 °C in all cases in the presence of MAO cocatalyst. Efficient synthesis of high-molecular-weight (HMW) ethylene copolymers incorporating DC-OH (or 5-hexen-1-ol, HX-OH) has been attained in the copolymerization by 7, which showed better DC-OH (HX-OH) incorporation at 50 °C to afford the HMW copolymers, poly(ethylene-co-DC-OH)s, with high activities (activity 1.21-3.81×10 5  kg-polymer mol -1 -Ti h, M n =6.55-10.0×10 4 , DC-OH 2.3-3.6 mol %)., (© 2020 Wiley-VCH GmbH.)

We herein report the functionalization of plant oil with norbornene (NB) and subsequent polymerization to prepare biobased thermoset films and biobased binders for silicon/mesocarbon microbead (MCMB) composite electrodes for use in lithium-ion batteries. A series of NB-functionalized plant oils were prepared as biobased thermoset films via ring-opening metathesis polymerization (ROMP) in the presence of a second-generation Grubbs catalyst with tunable thermomechanical properties. Increasing the catalyst loading and cross-linking agent increased cross-link density, storage modulus ( E '), and glass transition temperature ( T g ), while the numbers of unreacted or oligomeric components in the films were reduced. High number of NB rings per triglyceride in the plant oil encouraged monomer incorporation to form a polymer network, therefore accounting for the high T g and E ' values. Furthermore, the NB-functionalized plant oil and 2,5-norbornadiene (NBD) were copolymerized as bioderived binders for silicone/MCMB composite electrodes of lithium-ion batteries via ROMP during electrode preparation. Cell performance investigation showed that the silicone/MCMB composite electrode bearing the NBD-cross-linked NB-functionalized plant oil binder exhibited a higher C-rate and cycle-life performance than that using a conventional poly(vinylidene fluoride) (PVDF) binder. Finally, the electrode based on the bioderived binder exhibited a high specific charge capacity of 620 mA h g -1 at 0.5 C., Competing Interests: The authors declare no competing financial interest., (© 2020 American Chemical Society.)

Acyclic diene metathesis (ADMET) polymerization of biobased α,ω-dienes of bis(undec-10-enoate) with diols (1,4-butanediol, isosorbide, isomannide, and 1,4-cyclohexanedimethanol) afforded high-molecular weight unsaturated polyesters, and subsequent tandem hydrogenation (H 2 1.0 MPa, 50 °C, 3 h) gave the saturated polymers upon addition of a small amount of Al 2 O 3 (1.0-1.7 wt %). Subsequent reaction of the unsaturated polymers with ethylene afforded the oligomers (by depolymerization and degradation)., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

Light-active dinuclear iridium pentahydride complexes catalyze the decomposition of formic acid to generate H 2 by irradiation (λ =395 nm) under ambient temperature and base-free conditions. The catalyst activity is sensitive to light producing H 2 under light irradiation, but with no reaction being observed in the absence of light or when the light is switched off, thereby demonstrating the clear ON/OFF switching ability of this system. Importantly, the dinuclear structure of the catalyst is sufficiently stable to be maintained under the catalytic conditions employed herein.

X-ray absorption near edge structures (XANES) of vanadium and titanium complexes were investigated with time-dependent density functional theory (TDDFT). In particular, observed characteristic K-edge features in the presence of chloride ligands were assigned. Although TDDFT includes a large systematic error attributed to the 1s core energy levels of transition metals, pre-edge spectral shapes could be reproduced by a simple energy shift in the calculated excitation energies. The doublet peak in the pre-edge region was assigned to dipole-allowed transitions from 1s to 3d + 4p hybridized orbitals, while a characteristic shoulder peak in the chloride complex was assigned to excitations of chloride 4p orbitals. A similar but weak absorption band was computed for the methyl complex as excitation to C-H σ* orbitals. However, because these excitations were highly dependent on the direction of the C-H bonds, the shoulder peak was not experimentally observed because of methyl free rotation. Hence, the intensity of the shoulder peak was proportional to the number of chloride ligands unless other ligands contribute to this energy region and, therefore, could be used to detect the presence or absence of chloride ligands in unknown compounds, such as reaction intermediates.

Copolymerizations of 1-decene (DC) with 1,9-decadiene (DCD), 1-dodecene (DD) with 1,11-dodecadiene (DDD), and 1-tetradecene (TD) with 1,13-tetradecadiene (TDD), using Cp*TiMe 2 (O-2,6- i Pr 2 C 6 H 3 ) ( 1 )-[Ph 3 C][B(C 6 F 5 ) 4 ] (borate) catalyst in the presence of Al i Bu 3 /Al( n -C 8 H 17 ) 3 proceeded in a quasi-living manner in n -hexane at -30 to -50 °C, affording ultrahigh molecular weight (UHMW) copolymers containing terminal olefinic double bonds in the side chain with rather low PDI ( M w / M n ) values. In the DC/DCD copolymerization, the resultant copolymer prepared at -40 °C possessed UHMW ( M n = 1.40 × 10 6 after 45 min) with low PDI ( M w / M n = 1.39); both the activity and the PDI value decreased at low polymerization temperature ( M n = 5.38 × 10 5 , M w / M n = 1.18, after 120 min at -50 °C). UHMW poly(TD- co -TDD) was also obtained in the copolymerization at -30 °C ( M n = 9.12 × 10 5 , M w / M n = 1.51, after 120 min), using this catalyst., Competing Interests: The authors declare no conflicts of interest.

(Arylimido)vanadium(V) dichloride complexes containing anionic N -heterocyclic carbene (NHC) ligands that contain weakly coordinating B(C 6 F 5 ) 3 moieties (WCA-NHC) of the type [V(NAr)Cl 2 (WCA-NHC-Ar')] ( 5 , Ar = 2,6-Me 2 C 6 H 3 , Ar' = 2,6- i Pr 2 C 6 H 3 ) showed significant catalytic activity for ethylene polymerization in the presence of Al cocatalysts (MAO and Al i Bu 3 ); the activity by the 5 -MAO catalyst (19 500 kg-PE/mol-V·h; TOF 11 600 min -1 ) is the highest among those reported using the other (imido)vanadium(V) complexes in the presence of MAO, and the 5 -Al i Bu 3 catalyst showed higher activity (66 000 kg-PE/mol-V·h; TOF 39 200 min -1 ). The V K-edge X-ray absorption near-edge structure (XANES) analyses (in toluene) strongly suggest the formation of certain vanadium(III) species by reduction with Al i Bu 3 accompanying structural changes; the EXAFS analysis suggests the presence of the arylimido ligand and one V-Cl bond (2.34 ± 0.04 Å), which is longer than those [2.1901(8)-2.2462(8) Å] in the reported (imido)vanadium(V) complexes. The XANES analysis of [V(NAr)Cl 2 (OAr)] strongly suggests the formation of the other vanadium(III) species by reduction with Me 2 AlCl or Et 2 AlCl, and the EXAFS analysis suggests the presence of the arylimido ligand and two V-Cl bonds (2.45 ± 0.03 Å). The XANES spectra showed no significant changes in both the pre-edge peak(s) and the edge peak when these complexes were treated with MAO, suggesting that the basic geometry and the high oxidation state were preserved under these conditions., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)

Low-pressure hydrogenation of carbon dioxide (CO2) has been achieved using a trinuclear iridium hexahydride complex 1. Complex 1 is ligated with a light-absorbing diphosphine ligand to induce light-sensitizing ability. Under photoirradiation, 1 catalyzes CO2 hydrogenation under low-pressure conditions (H2 (5 atm) and CO2 (5 atm)) and at ambient temperature to yield the corresponding formate in high yield.

Synthesis of new polyesters by acyclic diene metathesis (ADMET) polymerization of α,ω-diene, 4-allyl-2-methoxyphenyl 10-undecenoate (M1), prepared from bio-renewable eugenol and castor oil (undecenoate), have been demonstrated. Ruthenium-carbene (called second generation Grubbs) catalyst afforded polymers with unimodal molecular weight distributions ( M n = 12 700, M w / M n = 1.85). The polymerization in the presence of a triarm cross-linker, 5-formylbenzene-1,2,3-triyl tris(undec-10-enoate), also afforded polymers with certain uniform network structures., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Reactions of a series of (arylimido)vanadium(V) trialkyl complexes, V(NAr')(CH 2 SiMe 3 ) 3 (Ar' = C 6 H 5 , 2-MeC 6 H 4 , 2,6-Me 2 C 6 H 3 , 2,6-Cl 2 C 6 H 3 ), with various phenols (ArOH, Ar = 2,6-F 2 C 6 H 3 , 2,6-Cl 2 C 6 H 3 , 2,6-Me 2 C 6 H 3 , 2,6- i Pr 2 C 6 H 3 , 2- t BuC 6 H 4 , 2,6- t Bu 2 C 6 H 3 ; 1.0 equiv) affording V(NAr')(CH 2 SiMe 3 ) 2 (OAr) were conducted in C 6 D 6 at 25 °C, and the effects of both arylimido ligands and phenols on the substitution rate were explored. Sterically hindered arylimido ligands showed lower reactivity, and the reaction proceeded in the order: Ar' = 2,6-Me 2 C 6 H 3 < 2,6-Cl 2 C 6 H 3 < 2-MeC 6 H 4 < C 6 H 5 . This order is somewhat different from that obtained from the chemical shifts in V(NAr')(CH 2 SiMe 3 ) 3 in the 51 V NMR spectra. The conversions with various disubstituted phenols increased in the order: 2,6- i Pr 2 C 6 H 3 OH < 2,6-Me 2 C 6 H 3 OH < 2,6-Cl 2 C 6 H 3 OH < 2,6-F 2 C 6 H 3 OH, irrespective of the kind of arylimido ligands. The reactions of V(NAr')(CH 2 SiMe 3 ) 3 with 2,6- t Bu 2 C 6 H 3 OH (1.0 or 3.0 equiv) did not take place even upon heating at 60 °C. These results suggest that the reactions proceed via coordination of ArOH toward vanadium, and the reactivity is highly dependent on steric bulk of both the arylimido ligand and the phenol., Competing Interests: The authors declare no competing financial interest.

Highly active catalysts for the ring-opening metathesis polymerization (ROMP) of cyclic olefins (norbornene, cyclopentene, cycloheptene) can be generated in situ by premixing V(CHSiMe 3 )(NC 6 F 5 )(O-2,6- i Pr 2 C 6 H 3 )(PMe 3 ) 2 (1) with 1.0 equiv. of C 6 F 5 OH or C 6 Cl 5 OH via the immediate phenoxy exchange; the activity was affected by the kind of phenol added [activity (TOF) in the ROMPs of norbornene: 46 200 min -1 (upon addition of C 6 F 5 OH) vs. 37.3 min -1 (by 1)].

Cross-metathesis of unsaturated fatty acid methyl esters (methyl oleate (MO), methyl petroselinate (MP), and methyl erucate (ME), obtained from vegetable oils) with eugenol (obtained from clove oil) proceeded under green, mild conditions (in 2-propanol or ethanol at 50 °C) in the presence of a ruthenium-carbene catalyst (called a second-generation Grubbs catalyst). These metathesis reactions proceeded with both high conversion (>90% of MO, MP) and selectivity (>98%) even with low catalyst loading (0.1 mol % Ru)., Competing Interests: The authors declare no competing financial interest.

New di- and trinuclear iridium (Ir) penta- and hexahydride complexes containing light-absorbing diphosphine ligands have been developed. The trinuclear Ir complex possessed a higher absorption coefficient (standardized per Ir) than that of the parent mononuclear Ir complex, indicating the assembly effect. The trinuclear complex showed high reactivity toward catalytic hydrogenation of diphenylacetylene under mild conditions, and the reaction was considerably accelerated under photoirradiation.

Precise synthesis of soluble star-shaped polymers has been achieved by adopting living ring-opening metathesis polymerisation (ROMP) using a molybdenum-alkylidene catalyst with sequential addition of norbornene and cross-linking agent; the method provides efficient one-pot synthesis of high molecular weight end-functionalised star-shaped polymers ( M n = >1.37 × 10 5 ) with more arms (branching) with rather low PDI values ( M w / M n = 1.17-1.37) under the optimised conditions., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Reactions of Nb(NAr)(N=C t Bu 2 ) 3 ( 3a , Ar = 2,6-Me 2 C 6 H 3 ) with 1.0, 2.0, or 3.0 equiv of Ar'OH (Ar' = 2,6- i Pr 2 C 6 H 3 ) afforded Nb(NAr)(N=C t Bu 2 ) 2 (OAr'), Nb(NAr)(N=C t Bu 2 )(OAr') 2 , or Nb(NAr)(OAr') 3 , respectively (at 25 °C), whereas the reaction with 2.0 equiv of 2,6- t Bu 2 C 6 H 3 OH afforded Nb(NAr)(N=C t Bu 2 ) 2 ( O -2,6- t Bu 2 C 6 H 3 ) upon heating (70 °C) without the formation of bis(phenoxide) and the reaction of 3a with 2.0 equiv of 2,4,6-Me 3 C 6 H 2 OH afforded Nb(NAr)(N=C t Bu 2 )( O -2,4,6-Me 3 C 6 H 2 ) 2 (HN=C t Bu 2 ). Similar reactions of 3a with 1.0 equiv of (CF 3 ) 3 COH or 2.0 equiv of (CF 3 ) 2 CHOH afforded Nb(NAr)(N=C t Bu 2 ) 2 [OC(CF 3 ) 3 ](HN=C t Bu 2 ) or Nb(NAr)(N=C t Bu 2 )[OCH(CF 3 ) 2 ] 2 (HN=C t Bu 2 ), respectively. On the basis of their structural analyses and the reaction chemistry, it was suggested that these reactions proceeded via coordination of phenol (alcohol) to Nb and the subsequent proton (hydrogen) transfer to the ketimide (N=C t Bu 2 ) ligand. The reaction of Nb(NAr)(N=C t Bu 2 ) 2 (OAr') with 1.0 equiv of 2,4,6-Me 3 C 6 H 2 OH gave the disproportionation products Nb(NAr)(N=C t Bu 2 )(OAr') 2 and Nb(NAr)(N=C t Bu 2 )( O -2,4,6-Me 3 C 6 H 2 ) 2 (HN=C t Bu 2 ) with 1:1 ratio, clearly indicating the presence of the above mechanism and the fast equilibrium (between the ketimide and the phenoxide). The reaction of 3a with 1.0 or 2.0 equiv of C 6 F 5 OH afforded Nb(N=C t Bu 2 ) 2 (OC 6 F 5 ) 3 (HN=C t Bu 2 ) as the sole isolated product, which was formed from once generated Nb(NAr)(N=C t Bu 2 ) 2 (OC 6 F 5 )(HN=C t Bu 2 ) by treating with C 6 F 5 OH., Competing Interests: The authors declare no competing financial interest.

Optical properties of three types of terthiophene (3T) functionalized conjugated triarm (star-shaped) polymers consisting of poly(9,9-di- n -octyl-fluorene-2,7-vinylene) (PFV) arms and different [2,4,6-tri(biphenyl)benzene (TBP), 1,3,5-tri(benzyl)benzene (TBB), and triphenylamine (TPA)] cores, prepared by combined olefin metathesis with Wittig coupling, have been studied. Relative intensities [increases in the higher vibronic bands, (0, 1) fluorescence (FL)] of the fully conjugated TPA-core polymers, TPA(PFV-3T) 3 , in the fluorescence (FL) spectra in tetrahydrofuran (toluene) solution were higher than those in the other triarm polymers, TBP(PFV-3T) 3 , TBB(PFV-3T) 3 , whereas no significant differences were observed in their UV-vis spectra; notable temperature dependences were not observed in the UV-vis and FL spectra (at -5, 25, and 55 °C). Remarkable differences were not observed in the spectra in these polymer thin films, whereas λ max values red-shifted due to the formation of J -type aggregates. The observation for the time-resolved study well corresponds to results for the steady-state fluorescence measurements. The observed unique emission by the star-shaped (triarm) polymer containing the TPA core would be assumed to be due to a difference in nature of the core (higher coplanarity) compared to that of the others., Competing Interests: The authors declare no competing financial interest.

(Imido)vanadium(V) dichloride complexes containing 2-(2'-benzimidazolyl)-6-methylpyridine ligand (L) of type V(NR)Cl 2 (L) [R = 1-adamantyl (Ad, 1 ), C 6 H 5 ( 2 ), and 2,6-Me 2 C 6 H 3 ( 3 )] have been prepared, and their structures were determined by X-ray crystallography as distorted trigonal bipyramidal structures around vanadium. Reactions with ethylene using 1-3 in the presence of methylaluminoxane (MAO) afforded a mixture of oligomer and polymers, and the compositions were affected by the imido ligand employed. By contrast, 1-3 exhibited remarkable catalytic activities for ethylene polymerization in the presence of Me 2 AlCl; the phenylimido complex ( 2 ) exhibited the highest activity [80 100 kg-PE/mol-V·h turn over frequency (TOF, 2 850 000 h -1 , 792 s -1 )]. The ethylene copolymerizations with norbornene afforded ultrahigh-molecular-weight copolymers with uniform molecular weight distributions and compositions [e.g., M n = 1.71-2.66 × 10 6 , M w / M n = 2.27-2.53]. On the basis of V nuclear magnetic resonance ( 51 V NMR), electron spin resonance, and V K-edge X-ray absorption near-edge structure (XANES) spectra of the catalyst solution, the observed difference in the catalyst performance in the presence of (between) MAO and Me 2 AlCl cocatalyst should be due to the formation of different catalytically active species with different oxidation states. Apparent changes in the oxidation state were observed in the (especially in the NMR and XANES) spectra upon addition of Me 2 AlCl, whereas no significant changes in the spectra were observed in presence of MAO., Competing Interests: The authors declare no competing financial interest.

The NMR chemical shifts of vanadium ( 51 V) in (imido)vanadium(V) dichloride complexes with imidazolin-2-iminato and imidazolidin-2-iminato ligands were calculated by the density functional theory (DFT) method with GIAO. The calculated 51 V NMR chemical shifts were analyzed by the multiple linear regression (MLR) analysis (MLRA) method with a series of calculated molecular properties. Some of calculated NMR chemical shifts were incorrect using the optimized molecular geometries of the X-ray structures. After the global minimum geometries of all of the molecules were determined, the trend of the observed chemical shifts was well reproduced by the present DFT method. The MLRA method was performed to investigate the correlation between the 51 V NMR chemical shift and the natural charge, band energy gap, and Wiberg bond index of the V═N bond. The 51 V NMR chemical shifts obtained with the present MLR model were well reproduced with a correlation coefficient of 0.97.

A series of neutral and cationic palladium(II) complexes containing C 2 -symmetric bis(oxazoline) (BOX) ligands, (BOX)PdCl 2 ( 2a - d ), (BOX)Pd(Me)Cl ( 3a - d ), and [(BOX)PdMe(2,6-Me 2 C 5 H 3 N)] + PF 6 - ( 4a - d ) [BOX: 2,2'-(2-propylidene)bis{(4 R )-4-phenyl-5,5-dimethyl-2-oxazoline}, 2,2'-methylenebis{(4 R )-4-phenyl-5,5-dimethyl-2-oxazoline}, 2,2'-methylenebis{(4 R )-4,5,5-triphenyl-2-oxazoline}, and 2,2'-methylenebis{(4 R ,5 S )-4,5-diphenyl-2-oxazoline}], were prepared, and their structures were determined by X-ray crystallography. It was found that substituents at the 5-position (Ph, Me) in addition to substituents on the bridgehead carbon directly affect the structure around palladium, especially the BOX bite angle and the dihedral angles between the phenyl rings at the 4-position and the N 2 Pd plane. Treatment of the bridged methylene proton in the BOX ligand ( 1b - d ) with KH afforded the anionic BOX ligand; also, the neutral Pd complexes, (BOX)PdMe(2,6-Me 2 C 5 H 3 N) ( 5b - d ), could thus be prepared by reaction with Pd(Me)Cl(cod) (cod = 1,5-cyclooctadiene); 5b - d showed strong coordination to Pd, as demonstrated by X-ray crystallographic analysis., Competing Interests: The authors declare no competing financial interest.

Syntheses and structural determination of rhodium complexes ligated by diphosphines containing light-harvesting fluorene backbones are presented. In these rhodium complexes, the rhodium center is surrounded by a light-absorbing diphosphine unit. The presence of Rh-Rh bonding interactions is suggested by density functional theory studies.

Reported examples for synthesis of vanadium-alkylidene complexes and some selected reactions have been summarized. (Imido)vanadium(v)-alkylidene complexes exhibit catalytic activities for ring-opening metathesis polymerization (ROMP) of cyclic olefins; V(CHSiMe 3 )(N-2,6-Cl 2 C 6 H 3 )(OC 6 F 5 )(PMe 3 ) 2 exhibited remarkable catalytic activities for ROMPs of norbornene derivatives, polymerized cyclopentene and cis-cyclooctene. Highly cis-specific (living) ROMPs of norbornene have been achieved by V(CHSiMe 3 )(N-2,6-X 2 C 6 H 3 )[OC(CF 3 ) 3 ](PMe 3 ) 2 (X = H, Cl), and the activity increased at high temperature (50 and 80 °C) without a decrease in cis specificity (98%) in the presence of PMe 3 .

Ring-opening metathesis polymerization (ROMP) of various cyclic olefins especially using three (arylimido)vanadium(V)-alkylidene catalysts, V(CHSiMe3)(N-2,6-Cl2C6H3) (OC6F5) (PMe3)2 (3), V(CHSiMe3) (NR)[OC(CF3)3](PMe3)2 [R = Ph (6), 2,6-Cl2C6H3 (7)] have been explored. Complex 3 exhibited the highest catalytic activity (ex. TOF = 603 000 h(-1), 168 s(-1)) for ROMP of norbornene (NBE) among a series of (imido)vanadium(V)-alkylidenes, and the cis-specific living ROMPs of NBE proceeded with remarkable activities (TOF = 125 000-157 000 h(-1) at 25 °C) by the fluorinated alkoxo analogues (6, 7). The activities by 6, 7 increased at high temperature (50 and 80 °C) and/or upon addition of PMe3 without decrease in the cis selectivity (98%). The ROMPs in the presence of 1-hexene by 3, 7 proceeded without significant decrease in the activities, and the Mn values could be controlled by degree of chain transfer (cross metathesis). These dichlorophenylimido analogues (3, 7) were effective for ROMPs of various norbornene derivatives; ROMP of cyclooctene took place by 3, and the activity increased at high temperature (50, 80 °C).

(Arylimido)vanadium(V)-alkylidene complexes, V(CHSiMe3)(N-2,6-X2C6H3)(OC6F5)(PMe3)2 [X = Me (2), Cl (4)], exhibited remarkable catalytic activities for ring-opening metathesis polymerization (ROMP) of norbornene, and the ROMP by 2 proceeded in a living manner, affording ultrahigh molecular weight polymers. Cis-specific ROMP was achieved with the alkoxo analogues, V(CHSiMe3)(N-2,6-X2C6H3)[OC(CH3)(CF3)2]-(PMe3)2 [X = Me (5), Cl (6)]. Both the activity and the selectivity increased upon addition of PMe3, even at 50 °C.

Poly(9,9-di- n -octylfluorene-2,7-vinylene)s containing F-BODIPY [PFV-(F-BODIPY) 2 ] and Zn(II)-porphyrin have been prepared by olefin metathesis of the vinyl group in the PFV chain ends followed by subsequent Wittig-type coupling. An introduction of tris(2,5-dialkoxy-1,4-phenylene vinylene) into PFV-(F-BODIPY) 2 has also been achieved. The emission properties can be modified by the PFV chain length, chromophore, and the middle segment: PFV-(F-BODIPY) 2 exhibits white-light emission with high quantum efficiency.

The synthesis and structural analysis of the hetero-bimetallic M-Al complexes MMe[(O-2,4-(t)Bu2C6H2-6-CH2)2(μ2-O-2,4-(t)Bu2C6H2-6-CH2)N][Me2Al(μ2-O(i)Pr)] [M = Zr, Hf], prepared from M(O(i)Pr)[{(O-2,4-(t)Bu2C6H2)-6-CH2}3N] by treating with 1.0 equiv. of AlMe3, have been explored: these complexes exhibited catalytic activities for ethylene polymerisation in n-octane in the presence of methylaluminoxane (MAO). The Zr-Al analogue showed high catalytic activities affording polymers with unimodal molecular weight distributions.

The precise synthesis of chemically, analytically pure oligo(2,5-dialkoxy-1,4-phenylene vinylene)s [OPVs, alkoxy = O(CH2)2OSi(i)Pr3] with strictly controlled repeat units (up to 15 repeat units) and well-defined end groups has been achieved by a combined olefin metathesis reaction of 2,5-dialkoxy-1,4-divinylbenzene or their derivatives with a molybdenum-alkylidene complex and the subsequent Wittig-type cleavage with their dicarboxaldehyde analogues. The effects of the repeat units and the end functional groups toward their UV-vis and the fluorescence spectra have been clearly demonstrated.

A series of (imido)vanadium dichlorido complexes containing chelate anionic donor ligands of the type, VCl2(L)(NR) [R = 1-adamantyl (Ad), L = 2-(2,6-Me2C6H3)NCH2(C9H6N) (2), 8-(2,6-Me2C6H3)NCH2(C9H6N) (3); L = 2-(2,6-R'2C6H3)NCH2(C5H4N), R = 2-MeC6H4, R' = Me (4a), (i)Pr (4b); L = 2-(2,6-Me2C6H3)NCH2(C5H4N), R = 4-MeC6H4 (5), 3,5-Me2C6H3 (6)], have been prepared and identified. The reactions with ethylene by 2,3 in the presence of methylaluminoxane (MAO) afforded a mixture of high molecular weight polyethylene and oligomers. Reactions with ethylene by VCl2[2-(2,6-R'2C6H3)NCH2(C5H4N)](NAd) (1a,b), 4-6 afforded 1-butene with high selectivities (>92%), and the activities by 4a,b are at the same level as those in 1a,b. The activities by 5,6 were lower than 4a,b and were at the same level of that by VCl2[2-(2,6-Me2C6H3)NCH2(C5H4N)](NPh). These results thus suggest that both the chelate anionic donor and the imido ligands play a role for both the activity and the selectivity.

A facile synthesis of oligo(thiophene)-modified (coated) "soluble" star (ball)-shaped polymers has been achieved via sequential living ring-opening metathesis polymerization (ROMP) of norbornene and a cross-linking reagent using Mo(CHCMe(2)Ph)(N-2,6-(i)Pr(2)C(6)H(3))(O(t)Bu)(2) as the initiator and oligo(thiophene) carboxaldehydes for termination. The resultant star-shaped ROMP polymers containing ter- and tetrathiophene moieties exhibit unique emission properties due to an integration of the ROMP polymers (arranged functionalities): the blue emission was tuned to the white emission upon addition of 2-[2-[(E)-4-(dimethylamino)styryl]-6-methyl-4H-pyran-4-ylidene]malononitrile.

Various block (graft) copolymers have been prepared by combination of acyclic diene metathesis (ADMET) polymerization of 9,9-dialkyl-2,7-divinyl-fluorene with Cu-catalyzed atom transfer radical polymerization (ATRP) of styrene using macroinitiators prepared by introduction of initiating functionalities into poly(9,9-dialkylfluorene-2,7-vinylene)s (PFVs) chain ends: a precise synthesis of the amphiphilic ABCBA-type block copolymers has also been attained by subsequent combination with click reaction after modification of the chain end with NaN 3 .

Various half-sandwich titanium complexes containing iminoimidazolidide ligands, CpTiCl(2)[1,3-R(2)(CH(2)N)(2)C=N] (1a-d) [R = Ph (a), 2,6-Me(2)C(6)H(3) (b), cyclohexyl (c), (t)Bu (d)], have been employed as the catalyst precursors for ethylene polymerisation, syndiospecific styrene polymerisation, and copolymerisation of ethylene with 1-hexene in the presence of MAO cocatalyst; 1d showed the highest catalytic activity for ethylene polymerisation whereas 1b showed the highest activity for syndiospecific styrene polymerisation., (This journal is © The Royal Society of Chemistry 2011)

Selected examples concerning effects of both cyclopentadienyl fragment (Cp') and anionic donor ligand (Y) in nonbridged modified half-titanocenes of the type, Cp'TiX(2)(Y) (X = halogen, alkyl), as new type of olefin polymerisation catalysts have been reviewed. These complexes displayed unique characteristics not only for ethylene (co)polymerisation but also for syndiospecific styrene polymerisation, ethylene/styrene copolymerisation; precise fine tuning of the ligand substituents plays an important role for the successful (co)polymerisation; a different mechanistic consideration for the syndiospecific styrene polymerisation, which can explain the copolymerisation behaviour in this catalysis, has also been introduced., (This journal is © The Royal Society of Chemistry 2011)

Salt metathesis of (2,6-xylylimido) vanadium trichloride (1) with the unsolvated or the TMEDA lithium p-Et benzamidinate complexes (2 and 3, respectively, in 1 : 2 V : Li molar ratio) yields bis[N,N'-bis(trimethylsilyl) p-Et benzamidinate](2,6-xylylimido)VCl (4) as dark brown, diamond-shaped crystals. When equimolar amounts of complexes 1 and 2 are reacted, a mixture of the bis (4) and mono (5) imidovanadium amidinates results. A similar mixture is also obtained by a ligand metathesis reaction of the bis amidinate complex 4 and complex 1. When the synthesis of the mono amidinate 5 is attempted with the TMEDA lithium amidinate complexes 3 or the 3-pyridyl derivative (7) (in 1 : 1 V : Li molar ratio) a redox reaction takes place to produce (kappa(2)-TMEDA)(2,6-xylylimido)V(IV)Cl(2) (6) as crystalline, mustard-yellow plates. The activity of complex 4 in ethylene polymerization was negligible with MAO or MAO\(CPh(3))(+)[B(C(6)F(5))(4)](-) as co-catalysts.

(Imido)vanadium(V) complexes containing the (2-anilidomethyl)pyridine ligand, V(NR)Cl(2)[2-ArNCH(2)(C(5)H(4)N)] (R = 1-adamantyl (Ad), cyclohexyl (Cy), phenyl), exhibit remarkably high catalytic activities (e.g. TOF = 2 730 000 h(-1) (758 s(-1)) by V(NAd)Cl(2)[2-(2,6-Me(2)C(6)H(3))NCH(2)(C(5)H(4)N)) for ethylene dimerization in the presence of MAO, affording 1-butene exclusively (selectivity 90.4 to >99%). The steric bulk of the imido ligand plays an important role in the selectivity (polymerization vs dimerization), and the electronic nature directly affects the catalytic activity (activity: R = Ad > Cy > Ph).

Recent efforts concerning nonbridged half-titanocenes containing anionic donor ligand of the type, Cp'TiX(2)(Y) [Cp' = cyclopentadienyl group; X = halogen, alkyl; Y = anionic ancillary donor ligands such as aryloxo, ketimide etc.], as new types of olefin polymerisation catalysts have been reviewed. It has been demonstrated that these complexes displayed unique characteristics especially for ethylene copolymerisation affording new polymers by efficient incorporation of bulky olefins (so called "traditionally unreactive" monomers in transition metal catalysed coordination polymerisation), that have not been attained by the ordinary catalysts.

Tris(pyrazolyl)borate titanium(IV) complexes containing aryloxo ligand of type, TpTiCl(2)(OAr) [Tp = HB(pyrazolyl)(3); Ar = 2-(i)PrC(6)H(4), C(6)F(5), 2,6-Ph(2)C(6)H(3)], have been prepared, identified, and the structures of TpTiCl(2)(OC(6)F(5)), TpTiCl(2)(O-2,6-Ph(2)C(6)H(3)) have been determined by X-ray crystallography. The 2-(i)PrC(6)H(4) analogue exhibits especially high catalytic activities for ethylene polymerisation in the presence of methylaluminoxane (MAO), and the activity by TpTiCl(2)(OAr) increased in the order: Ar = 2-(i)PrC(6)H(4) > Ph > C(6)F(5) >> 2,6-Ph(2)C(6)H(3) > 2,6-Me(2)C(6)H(3), 2,6-(i)Pr(2)C(6)H(3).