A topological isomer of ferrocene: Theoretical approach for transition metal complexes with conjugated all trans cyclodecapentaene

We demonstrate the ability of all-trans DPEN as a suitable ligand for transition metals by DFT computation [B3LYP/6-311+G(2d,p) and BP86 level]. The iron complex Fe(DPEN) is a unique topological isomer of ferrocene.     

Microwave-resonance-induced resistivity: evidence of ultrahot surface-state electrons on liquid 3He

Measurements of the dc resistivity of surface-state electrons on liquid helium exposed to microwave radiation are reported. It is shown that the resonant microwave excitation of surface-state electrons is accompanied by a strong increase in their resistivity, which is opposite to the result expected from the previously used two-level model. We show that even a very small fraction of electrons excited to the first excited state and decaying back due to vapor-atom scattering strongly heat the electron system, causing a population of higher subbands. The calculated resistivity change is in good agreement with the observed data.     

Salt‐Free Reduction of Nonprecious Transition‐Metal Compounds: Generation of Amorphous Ni Nanoparticles for Catalytic C–C Bond Formation

A salt‐free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6‐tetramethyl‐1,4‐bis(trimethylsilyl)‐1,4‐diaza‐2,5‐cyclohexadiene ( 1 ), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)₂ (acac=acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C? C bond‐forming reactions of aryl halides in the presence of excess amounts of 1 . By examination of high‐magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity.     

2,2′-Bipyridyl formation from 2-arylpyridines through bimetallic diyttrium intermediate

An alkylyttrium complex supported by an N,N′-bis(2,6-diisopropylphenyl)ethylenediamido ligand, (ArNCH₂CH₂NAr)Y(CH₂SiMe₃)(THF)₂ (1, Ar = 2,6-ⁱPr₂C₆H₃), activated an ortho-phenyl C–H bond of 2-phenylpyridine (2a) to form a (2-pyridylphenyl)yttrium complex (3a) containing a five-membered metallacycle. Subsequently, a unique C(sp²)–C(sp²) coupling of 2-phenylpyridine proceeded through a bimetallic yttrium intermediate, derived from an intramolecular shift of the yttrium center to an ortho-position of the pyridine ring in 3a, to yield a bimetallic yttrium complex (4a) bridged by two-electron reduced 6,6′-diphenyl-2,2′-bipyridyl. Aryl substituents at the ortho-position of the pyridine ring were key in order to destabilize the μ,κ²-(C,N)-pyridyldiyttrium intermediate prior to the C(sp²)–C(sp²) bond formation.     

One‐Step Borylation of 1,3‐Diaryloxybenzenes Towards Efficient Materials for Organic Light‐Emitting Diodes

The development of a one‐step borylation of 1,3‐diaryloxybenzenes, yielding novel boron‐containing polycyclic aromatic compounds, is reported. The resulting boron‐containing compounds possess high singlet‐triplet excitation energies as a result of localized frontier molecular orbitals induced by boron and oxygen. Using these compounds as a host material, we successfully prepared phosphorescent organic light‐emitting diodes exhibiting high efficiency and adequate lifetimes. Moreover, using the present one‐step borylation, we succeeded in the synthesis of an efficient, thermally activated delayed fluorescence emitter and boron‐fused benzo[6]helicene.     

Construction of carbocyclic ring of indoles using ruthenium-catalyzed ring-closing olefin metathesis

The selective synthesis of substituted indoles was achieved by the ring-closing olefin metathesis (RCM)/elimination sequence or the RCM/tautomerization sequence of functionalized pyrrole precursors. The RCM/elimination sequence was also applied to double ring closure to yield a substituted carbazole.     

Oxidant-free direct coupling of internal alkynes and 2-alkylpyridine via double C-H activations by alkylhafnium complexes

We have developed a novel oxidant-free direct cross-coupling reaction of 2,6-lutidine and internal alkynes leading to five-membered carbocyclic compounds mediated by nonmetallocene cationic hafnium alkyl complexes. Mechanistic studies of the coupling reaction showed that the reaction begins with C(sp(3))-H bond activation via σ-bond metathesis, after which the coordinatively unsaturated hafnium center mediates further insertion, migration, and β-H elimination reactions to give five-membered carbocycles from readily available substrates.     

Projection of Si 1s photoexcited orbitals into resonant Auger electron spectra in KLL decays of Si(CH3)4 and SiF4

Spectator resonant KL(23)L(23) Auger electron spectra have been measured in the Si 1s photoexcitation region of Si(CH(3))(4) using monochromatized undulator radiation combined with a hemispherical electron spectrometer. The broad peak with high intensity in a total ion yield spectrum, coming mainly from excitation of a 1s electron into the 6t(2) vacant orbital, induces a spectator Auger decay in which the excited electron remains in its excited orbital. The component on the higher energy side of this peak through 1s excitation into a Rydberg orbital produces resonant Auger decays in which the excited Rydberg electron moves into a slightly higher Rydberg orbital, or is partly shaken up to a significantly higher Rydberg orbital. These findings of Si(CH(3))(4) indicate a clear contrast to those for SiF(4), in which the 1s excitation into a Rydberg orbital induces a shake-down phenomenon as well as a shake-up one. The results of these molecules exhibit a clear splitting effect among excited orbitals which are smeared out by overlapping due to lifetime widths and due to densely populated levels in the 1s electron excitation spectrum. This is consistent with the calculation on photoexcitation within the framework of density functional theory.