Titanium complexes supported by an [OSSO]-type bis(phenolato) ligand based on a trans-cyclooctanediyl platform: synthesis, structures, and 1-hexene polymerization

trans-Cyclooctanediyl-bridged [OSSO]-type ligand 4 reacts with TiCl(4)(thf)(2) in toluene to produce the corresponding titanium(IV) dichloro complexes as an inseparable mixture of cis-α isomer 6a and cis-β isomer 6b in a ratio of 2:1, whereas treatment of dilithio salt of 4 with TiCl(3)(thf)(3) in Et(2)O afforded chloride-bridged dimeric titanium(III) complex 8, which indicated the antiferromagnetic character in a nonpolar solvent solution. Di(isopropoxy) titanium(IV) complex 10 having a C(2)-symmetric cis-α configuration was synthesized by the reaction of 4 with Ti(O(i)Pr)(4) in toluene as yellow crystals. Moreover, the reaction of 4 with Ti(NEt(2))(4) in toluene resulted in the unexpected formation of [OSSO]-type bis(phenolato)-bridged dinuclear diamido titanium(IV) complex 11, which adopted a distorted tetrahedral geometry on the titanium center. These titanium complexes were characterized on the basis of their NMR spectroscopic data, and the molecular structures of complexes 8, 10, and 11 were established by single crystal X-ray diffraction. The titanium(IV) and (III) complexes 6 and 8 upon activation with a cocatalyst in toluene polymerized 1-hexene isospecifically to produce poly(1-hexene) having high molecular weight (M(w) = 22,000-52,000 g mol(-1)) and relatively narrow polydispersity (M(w)/M(n) = 1.7-1.8), albeit with low activity [0.27-1.0 g mmol(cat)(-1) h(-1)].     

Stereoselective synthesis of 2-alkenylaziridines and 2-alkenylazetidines by palladium-catalyzed intramolecular amination of alpha- and beta-amino allenes.

Whereas palladium-catalyzed reaction of N-arylsulfonyl-alpha-amino allenes with an aryl iodide (4 equiv) in the presence of potassium carbonate (4 equiv) in DMF at around 70 degrees C affords the corresponding 3-pyrroline derivatives, the reaction in refluxing 1,4-dioxane under otherwise identical conditions yields exclusively or most predominantly the corresponding 2-alkenylaziridines bearing an aryl group on the double bond. Similarly, N-arylsulfonyl-beta-amino allenes can be also cyclized into the corresponding alkenylazetidines bearing a 2,4-cis-configuration under palladium-catalyzed cyclization conditions in DMF.     

Structure of a 1:1 molecular complex of trans-9,10-dihydroxy-9,10-diphenyl-9,10-dihydroanthracene with ethanol

X-ray analysis of the title complex revealed hydrogen-bonded chains comprising two crystallographically independent types of $\text{trans}$-9,10-dihydroxy-9,10-diphenyl-9,10-dihydroanthracene molecules, in which the central 1,4-cyclohexadiene rings are respectively flat and very slightly puckered, with the ethanol molecules attached exclusively to the latter type.     

Synthesis of bis(pyrrol-2-yl)arenes by Pd-catalyzed cross coupling

2-Borylpyrrole was prepared from 2-iodopyrrole almost quantitatively and then reacted with dihaloarenes under typical reaction conditions of Suzuki-Miyaura cross coupling to give bis(pyrrol-2-yl)arenes in good yields, while the cross coupling reaction of 2-iodopyrrole with 1,4-phenylenebisboronic acid was susceptible to oxidative self-coupling to produce 4,4′-bis(pyrrol-2-yl)biphenyl as a byproduct. These bis(pyrrol-2-yl)arenes showed strong fluorescence.     

Infrared seed inspection system (IRSIS) on painted car shells

This paper describes a newly-developed automated thermal system for detection of seeds on newly painted car shells. The system’s novel approach is to use thermal emission; previously applied techniques relied on light reflection strategies. The system is described beginning with analytical modeling of the underlying detection theory to verification on a pilot run in an automotive production line. Parker’s flash procedure, using a thermal detector, was performed to extract the thermal properties of inspected panels. New computer logic developed in-house for processing the acquired thermograms is also presented.     

Crystal growth of polyethylene from dilute solution: Growth kinetics of {110} twins and diffusion-limited growth of single crystals

We have studied the growth kinetics of {110} twins and single crystals of polyethylene in dilute solution of tetrachlorethylene. In terms of {110} twins, we succeeded in obtaining twins without {100} sectors, using a relatively high molecular weight fraction M_w > 10⁴. It is confirmed that the growth is enhanced at the reentrant corner of the twins, and the enhanced growth face inclines to the {110} face because of consecutive generation of steps at the corner. These facts are strong evidence for nucleation-controlled growth of single crystals. The growth rates and obliquity are measured at various supercoolings and concentrations. From consideration of kinetics of steps on the growth face, the following rates and velocity are independently determined from the experimental data: nucleation rate on a flat face, velocity of step propagation, and generation rate of steps at the reentrant corner. The supercooling dependence strongly supports regime II growth. The results on concentration dependence show that the velocity of steps is proportional to concentration over the whole range examined, and the nucleation rate is independent of it in the usual range and becomes proportional to it in the lower range. This concentration dependence of nucleation rate is attributed to the density of adsorbed polymer on the growth face. From this evidence, it is suggested that the rate of travel of steps is limited by volume diffusion of solute polymer, whereas the growth face is saturated with adsorbed polymer at ordinary concentrations. This contradictory situation could be explained by the hypotheses that the saturation density is rather low and that surface diffusion of adsorbed polymer is much slower than volume diffusion of solute polymer. The lower limit of the rate of folding is also determined for the first time from the velocity of step propagation. As regards the single crystals, it is found that the habit maintains a lozenge shape with sharpened points, even at very high supercooling (δT < 50°C) if the concentration is very dilute. Diffusion-limited growth is verified for the first time at the higher supercoolings, where the growth rate is almost independent of supercooling. The growth rate becomes almost equivalent to the velocity of steps determined in the experiments with twins, and this fact will support the accuracy of the evaluation of the step velocity. The order of magnitude of the growth rate obtained agrees with the value which is calculated from the balance between the flux of solute polymer to the growth face and the rate of growth of single crystals.     

Controlled radical polymerization of 2‐hydroxyethyl methacrylate initiated by photofunctional 2‐(N,N‐diethyldithiocarbamyl)isobutyric acid

We demonstrated that density functional theory calculations provide a reliable and quantitative prediction of the trends in C? S bond dissociation energies using several model compounds as photoinitiator. On the basis of this information, we designed a possible photofunctional initiator for the polymerization of hydrophilic vinyl monomers. Photopolymerization of 2‐hydroxyethyl methacrylate (HEMA) hydrophilic monomer was carried out in ethanol initiated by 2‐(N,N‐diethyldithiocarbamyl)isobutyric acid (DTCA) under UV irradiation. We performed the first‐order time‐conversion plots in this polymerization system, and the straight line in the semilogarithmic coordinates indicated first order in monomer. The molecular weight of the poly(2‐hydroxyethyl methacrylate) (PHEMA) increased with increasing conversion. The molecular weight distribution (M_w/M_n) of the PHEMA was about 1.5. Methyl methacrylate (MMA) could also be polymerized in a living fashion with such a PHEMA precursor as a macroinitiator because PHEMA exhibited a dithiocarbamate (DC) group at its terminal end. This system could be applied to the architecture of amphiphilic block copolymers. It was concluded that these polymerization systems proceeded with controlled radical mechanism. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 76–82, 2004