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Mesoporous silica-supported Rh complexes alongside organic functional groups enable 1,4-addition reaction in water.

Iron carbide clusters with near-sub-nanometer size have been synthesized by employing a tetraphenylmethane-cored phenylazomethine dendrimer generation 4 (TPM-DPAG4) as a molecular template. Magnetic measurements reveal that these iron carbide clusters exhibit a magnetization-field hysteresis loop at 300 K. The data indicate that these iron carbide clusters are ferromagnets at room temperature.

Ultrasmall particles exhibit structures and/or properties that are different from those of the corresponding bulk materials; in this context especially ultrasmall precious-metal particles have been extensively investigated. In this study, we targeted the transition base-metal Mo and succeeded in systematically producing Mo oxycarbide/carbide particles with diameters of 1.7 ± 0.7, 1.4 ± 0.5, 1.3 ± 0.4, 1.2 ± 0.3, 1.0 ± 0.3, and 0.8 ± 0.2 nm on a carbon support using the carbothermal hydrogen reduction method at 773 K and a diphenylazomethine-type dendrimer as a template. The formation and properties of the particles were confirmed using X-ray photoelectron spectroscopy, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images, and X-ray absorption fine structure (XAFS) studies. We found that Mo particles with a diameter of 1.3 nm or greater formed carbides such as β'-Mo2C, whereas smaller particles formed oxycarbides, indicating a size-dependent transformation in the phase or composition of the particles. Thus, this work demonstrated a new concept, subnano-transformation, which would be a new class of phase transformation based on the concept of the size dependence in such an ultrasmall scale. In addition, the movement of Mo atoms within a cluster and on the fringes of a nanoparticle was also demonstrated during continuous time-course high-resolution HAADF-STEM observation.

Ultrasmall particles, different from the larger size nanoparticles, have recently attracted significant attention in the scientific community in nanotechnology for catalytic, electronic and optical applications; however, their magnetic properties remain unexplored due to the difficult structural analysis. A challenging issue is to develop a preparation method for iron oxide particles (IOPs) with fine size control, and to determine the dependence of magnetic properties on the morphology and crystallinity of the magnetic particles. However, synthetic approaches to obtain IOPs, regarded as one of the new fields of magnetic nanoparticles, have been significantly limited. This article reported a developed synthetic method to prepare IOPs on carbon supports using pulsed arc plasma deposition (APD) in flowing oxygen gas, which clarified the finely-controlled formation of IOPs on graphene nanosheets. Structural characterization of the IOPs revealed the formation of crystalline γ-Fe2O3 ultrasmall particles with oxygen deficiency. The pulsed APD method for IOPs is the first simple and convenient technique to not only prevent significant aggregation and contamination by organic compounds and avoid the need for thermal pretreatment, but also provide uniform crystalline nano-order particles.

Correction for ‘A Pd–bisphosphine complex and organic functionalities immobilized on the same SiO2 surface: detailed characterization and its use as an efficient catalyst for allylation’ by Ken Motokura et al., Catal. Sci. Technol., 2016, DOI: 10.1039/c6cy00593d.

Double-activation catalysis by a rhodium complex/tertiary amine catalyst for the 1,4-addition of organoboronic acids was investigated. A rhodium complex and a tertiary amine were co-immobilized on the same silica surface by silane-coupling reactions followed by complexation of the Rh species. Structures of the Rh complex and tertiary amine on the silica surface were determined by solid-state 13C and 29Si MAS NMR, XAFS, and XPS measurements. The immobilized tertiary amine accelerated the Rh-catalyzed 1,4-addition of phenylboronic acid to cyclohexenone. The role of the anchored tertiary amine in the 1,4-addition reaction was clarified by solid-state 11B MAS NMR: it activates the arylboronic acid forming a four-coordinate boron species, which then accelerates the transmetallation step in the Rh complex-catalyzed 1,4-addition. The silica-supported Rh complex/tertiary amine catalyst system could be applicable to the reaction of various aryl- and even alkyl-boronic acids.

Pt4-cluster/SiO2catalyst, prepared from the [Pt4(µ-CH3COO)8] cluster, has shown remarkably high catalytic activity with 100% selectivity to CO2 and H2 for the decomposition of formic acid as compared with the Pt-particle/SiO2 catalyst. In order to elucidate the genesis and the mechanism for catalysis by Pt4-cluster/SiO2, the samples were characterized by kinetics, Pt LIII-edge extended X-ray absorption fine structure (EXAFS), and FTIR spectroscopy. EXAFS and IR data revealed that the surface structure of the catalyst changed from the tetramer to dimers during an induction period, then to monomers which were active for the catalysis. Eventually Pt particles were formed which were of much lower catalytic activity. The structural transformations of the Pt4-cluster/SiO2 catalyst are discussed in relation to the catalytic reaction profiles.