Coordination Structure of Samarium Diiodide in a Tetrahydrofuran-Water Mixture.

Chemoselective reductive conversion of organic and inorganic compounds has been developed by the combination of samarium(II) diiodide (SmI2) and water. Despite the extensive previous studies to elucidate the role of water in the reactivity of SmI2, the direct structural data of the reactive Sm2+-water complexes, SmI2(H2O)n, in an organic solvent-water mixture have not been reported experimentally so far. Herein, we performed the structure analysis of the Sm2+-water complex in tetrahydrofuran (THF) in the presence of water by in situ X-ray absorption spectroscopy using high-energy X-rays (Sm K-edge, 46.8 keV). The analysis revealed the dissociation of the Sm2+-I bonds in the presence of ≥ eight equivalents of water in the THF-water mixture. The origin of the peak shift in the UV/visible absorption spectra after the addition of water into SmI2/THF solution was proposed based on electron transitions simulated with time-dependent density-functional-theory calculations using optimized structures in THF or water. The obtained structural information provides the fundamental insights for elucidating the reactivity and chemoselectivity in the Sm2+-water complex system.

Synthesis and Reactivity of Cobalt-Dinitrogen Complexes Bearing Anionic PCP-Type Pincer Ligands toward Catalytic Silylamine Formation from Dinitrogen.

A series of cobalt(I)-dinitrogen complexes bearing anionic 4-substituted benzene-based PCP-type pincer ligands are synthesized and characterized. These complexes work as highly efficient catalysts for the formation of silylamine from dinitrogen under ambient reaction conditions to produce up to 371 equiv of silylamine based on the cobalt atom of the catalyst.

Design, synthesis and reactivity of dimolybdenum complex bearing quaterphenylene-bridged pyridine-based PNP-type pincer ligand.

Dimolybdenum complexes bearing 3,3'''-(1,1':3',1'':3'',1'''-quaterphenylene)-bridged pyridine-based PNP-type pincer ligand are designed and prepared according to DFT calculations on the cleavage step of dinitrogen-bridged dimolybdenum complexes bearing polyphenylene-bridged pyridine-based PNP-type pincer ligands. The dimolybdenum complexes are found to work as effective catalysts toward ammonia formation from dinitrogen with samarium diiodide as a reductant and water as a proton source under ambient reaction conditions.

Catalytic nitrogen fixation using visible light energy.

The synthesis of ammonia from atmospheric dinitrogen, nitrogen fixation, is one of the essential reactions for human beings. Because the current industrial nitrogen fixation depends on dihydrogen produced from fossil fuels as raw material, the development of a nitrogen fixation reaction that relies on the energy provided by renewable energy, such as visible light, is an important research goal from the viewpoint of sustainable chemistry. Herein, we establish an iridium- and molybdenum-catalysed process for synthesizing ammonia from dinitrogen under ambient reaction conditions and visible light irradiation. In this reaction system, iridium complexes and molybdenum triiodide complexes bearing N-heterocyclic carbene-based pincer ligands act as cooperative catalysts to activate 9,10-dihydroacridine and dinitrogen, respectively. The reaction of dinitrogen with 9,10-dihydroacridine is not thermodynamically favoured, and it only takes place under visible light irradiation. Therefore, the described reaction system is one that affords visible light energy-driven ammonia formation from dinitrogen catalytically.

Preparation and reactivity of molybdenum complexes bearing pyrrole-based PNP-type pincer ligand.

Molybdenum complexes bearing an anionic pyrrole-based PNP-type pincer ligand have been prepared and have been found to work as catalysts for the conversion of N2 into NH3 under ambient conditions.

Dynamics Gradient of Polymer Chains near a Solid Interface.

The relaxation dynamics of polyisoprene (PI) and nitrile butadiene rubber (NBR) chains at the SiO2 interface were directly probed as a function of distance from the SiO2 surface using time-resolved evanescent wave-induced fluorescence anisotropy, dielectric relaxation spectroscopy, and sum-frequency generation spectroscopy. We found the presence of the dynamics gradient of chains in the interfacial region with the SiO2 surface and tried to assign it to the two kinds of adsorbed chains, namely, loosely and strongly adsorbed, at the interface. The segmental relaxation of chains in the strongly adsorbed layer at the interface could be slower than that of bulk chains by more than 10 orders.

Catalytic reduction of dinitrogen to tris(trimethylsilyl)amine using rhodium complexes with a pyrrole-based PNP-type pincer ligand.

Rhodium complexes bearing an anionic pyrrole-based PNP-type pincer ligand are synthesised and found to work as effective catalysts for the transformation of molecular dinitrogen into tris(trimethylsilyl)amine under mild reaction conditions. This is the first successful example of rhodium-catalysed dinitrogen reduction under mild reaction conditions.