Dehydrocoupling reactions of borane-secondary and -primary amine adducts catalyzed by group-6 carbonyl complexes: formation of aminoboranes and borazines.

Photoirradiation of a solution of BH(3).NHR(2) (1a: R = Me, 1b: R = 1/2C(4)H(8), 1c: R = 1/2C(5)H(10), 1f: R = Et) containing a catalytic amount of a group-6 metal carbonyl complex, [M(CO)(6)] (M = Cr, Mo, W), led to dehydrogenative B-N covalent bond formation to produce aminoborane dimers, [BH(2)NR(2)](2) (2a-c, f), in high yield. During these reactions a borane sigma complex, [M(CO)(5)(eta(1)-BH(3).NHR(2))] (3), was detected by NMR spectroscopy. Similar catalytic dehydrogenation of bulkier amineboranes, BH(3).NH(i)Pr(2) (1d) and BH(3).NHCy(2) (1e, Cy = cyclo-C(6)H(11)), afforded monomeric products BH(2) horizontal lineNR(2) (4d, e). The reaction mechanism of the dehydrocoupling was investigated by DFT calculations. On the basis of the computational study, we propose that the catalytic dehydrogenation reactions proceed via an intramolecular pathway and that the active catalyst is [Cr(CO)(4)]. The reaction follows a stepwise mechanism involving NH and BH activation. Dehydrocoupling of borane-primary amine adducts BH(3).NH(2)R (1g: R = Me, 1h: R = Et, 1i: R = (t)Bu) gave borazine derivatives [BHNR](3) (5g-i).

Visibility of LED Blocks Mounted on Crosswalk Boundaries for low Visual Capacity.

According to the WHO, about 80% of visually impaired persons in the world are with low visual capacity. It is considered that LVs' safe independent mobility will be improved as employing Tactile Walking Surface Indicators (TWSIs). In the night, guidelines for constructing warning blocks, a kind of tactile surface indicator, have not been well established. Therefore, crossing crosswalks is one of the most dangerous situations for visually impaired persons. We thus developed novel LED blocks that indicate crosswalk boundaries between sidewalks and roadways. This study addresses the LED blocks under various environmental illuminations and illumination from the opposite side of the crossing.

Formation of Isomeric Tetrathiotungstate Clusters [{Cp*Ru(CO)}2 (WS4 ){W(CO)4 }] by the Reaction of [Cp*2 Ru2 S4 ] with [W(CO)3 (MeCN)3 ].

Thermal and photochemical interconversion occurs between the isomeric pair of tetrathiotungstate [WS4 ]2- clusters 1 and 2, which were formed by thermolysis of [Cp*2 Ru2 S4 ] and [W(CO)3 (MeCN)3 ] [Eq. (1)] and then structurally characterized. During synthesis, a dramatic redistribution of ligands between the Ru and W atoms takes place without the loss of any CO and S ligands.

Sarcoidosis complicated with major pulmonary artery obstruction and stenosis.

A 34-year-old woman with bilateral pulmonary infiltrates was diagnosed with sarcoidosis. She refused corticosteroid treatment despite a worsening of the pulmonary infiltrate, and thereafter developed dyspnea following hemoptysis 6 years later. The upper lobe branches of the pulmonary artery were obstructed and the left main pulmonary artery was narrowed by mediastinal soft tissue, thus complications of granulomatous mediastinitis and fibrosing mediastinitis were suspected. The mediastinal soft tissue regressed, following the administration of corticosteroids, whereas the vascular obstruction and narrowing remained unchanged. Although the obstruction or stenosis of major pulmonary vessels is rare in sarcoidosis, such potential developments should be considered when mediastinal soft tissue appears in follow-up examinations.

Synthesis of silylene and silyl(silylene)metal complexes.

In 1987, two research groups published the first-ever reports on the synthesis of silylene complexes and presented structural evidence. Since then, a range of synthetic methods have been developed and a number of silylene complexes have been prepared. In 1988, we reported on the first base-stabilized bis(silylene) complexes that can be regarded as being masked silyl(silylene) complexes. These complexes occupy a unique position among silylene and silyl(silylene) complexes in that they provide a convenient tool for studying the reactivity of coordinated silylenes. They are stable enough to be isolated, but the bond between the silylene silicon atom and the internal base can easily be cleaved by thermal perturbation to generate real silyl(silylene) complexes. To date, a number of base-stabilized bis(silylene) complexes have been prepared in which the central metals range from group 5 to group 9. Only two base-free silyl(silylene) complexes have been prepared. One is prepared by reacting a platinum complex with a stable silylene; the other is produced by the photolysis of a tungsten complex in the presence of a hydrodisilane.

Reversible cleavage and recombination of an acetylenic carbon-carbon bond on a tetrairon cluster coupled with a two-electron redox reaction.

Two-electron reduction of [(eta5-C5H4Me)4Fe4(mu3-CH)2(mu3-CO)2](PF6)2 (1) results in the coupling of two methylidyne ligands to form (eta5-C5H4Me)4Fe4(HCCH)(mu3-CO)2 (2), the two-electron oxidation of which reproduces 1. Structures of 1 and 2 were determined by X-ray diffraction analysis.

Synthesis and structures of one- and two-electron oxidized forms of bis(acetylene)tetrairon clusters Cp'(4)Fe(4)(HCCH)(2) (Cp' = Cp, eta5-C(5)H(4)Me).

Air-oxidation of Cp'(4)Fe(4)(HCCH)(2) (Cp' = Cp (1a), C(5)H(4)Me (1b)) in an NH(4)PF(6)/CH(3)CN solution afforded the one-electron oxidized clusters [Cp'(4)Fe(4)(HCCH)(2)](PF(6)). Oxidation of 1a with excess AgBF(4) in THF afforded [1a](BF(4)), while that of 1b with excess AgBF(4) gave [1b](BF(4))(2). The X-ray crystal structure analysis of [1a](BF(4)) revealed that the monocationic cluster retains the butterfly-type Fe(4)(mu4-eta(2):eta(2):eta(1):eta(1)-HCCH)(2) framework similar to that of the neutral cluster. The average Fe-Fe bond length is shorter by 0.029 A than that in the neutral cluster. Electrochemical oxidation of 1a and 1b in 0.1 M NH(4)PF(6)/CH(3)CN solution at +0.30 and +0.25 V versus Ag/10 mM AgNO(3), respectively, afforded the two-electron oxidized clusters [1a](PF(6))(2) and [1b](PF(6))(2). The X-ray crystal structure analysis for [1b](BF(4))(2) shows that the butterfly-type cluster core is retained but shrinks more of those of neutral and monocationic clusters. The four Fe-Fe bonds in [1b](BF(4))(2) are unequivalent: one Fe-Fe bond (2.397(1) A) is apparently shorter than the others (2.439(2)-2.461(2) A).

Phosphasilaferracyclopropane: an activator of small molecules having polarized single, double, and aromatic unsaturated bonds.

Irradiation of Cp*(CO)2FeSiMe2PPh2 resulted in the formation of phosphasilaferracyclopropane 2, which readily reacted with small organic molecules with polarized bonds to yield 3-5.