New and easy protocols for radical reactions have been developed.

Rhodium-diene complexes with the Tp iPr ligand, Tp iPr Rh(diene) (Tp iPr ) hydridotris(3,5-diisopropylpyrazolyl)borate; diene ) 1,5-cyclooctadiene (cod) (1), norbornadiene (nbd) (2)), are prepared by treatment of [Rh(µ-Cl)(diene)] 2 with KTp iPr or TlTp iPr . The structure of 1, characterized by X-ray crystallography, contains the κ 2 -coordinated Tp iPr ligand, and its central Rh atom adopts a square-planar geometry, whereas the unit cell of 2 contains two independent molecules: a square-planar structure with a κ 2 -coordinated Tp iPr ligand similar to 1 and a trigonal-bipyramidal one with a κ 3 -coordinated Tp iPr ligand. Although 1 H and 13 C NMR spectroscopy does not provide any information concerning the coordination geometry due to the interconversion between the square-planar and trigonal-bipyramidal structures, which occurs at a rate much faster than the NMR time scale, IR analysis reveals that the bands observed around 2470 and 2540 cm -1 are assigned to the B-H stretching vibrations of the square-planar and trigonal-bipyramidal structures, respectively. Thus, the ν(B-H) value can be used as an indicator of the hapticity of a Tp iPr ligand (κ 2 (∼2470 cm -1 ) vs κ 3 (>2530 cm -1 )) as compared with related Tp iPr ML n -type complexes.

A new M(2)L(4) molecular capsule with an aromatic shell was prepared using two Pd(II) ions and four bisanthracene ligands. The self-assembled capsule possesses a cavity with a diameter of ~1 nm that can encapsulate medium-sized spherical and planar molecules as well as a very large molecule (C(60)) in quantitative yields. The encapsulated guests are fully segregated and shielded from the external environment by the large anthracene panels.

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Trifluoromethyl (CF3) and difluoromethyl (CF2H) groups are versatile structural motifs, especially in the fields of pharmaceuticals and agrochemicals. Thus, the development of new protocols for tri- and difluoromethylation of various skeletons has become a vital subject to be studied in the field of synthetic organic chemistry. For the past decades, a variety of fluoromethylating reagents have been developed. In particular, bench-stable and easy-to-use electrophilic fluoromethylating reagents such as the Umemoto, Yagupolskii-Umemoto, Togni, and Hu reagents serve as excellent fluoromethyl sources for ionic and carbenoid reactions. Importantly, the action of catalysis has become a promising strategy for developing new fluoromethylations. For the past several years, photoredox catalysis has emerged as a useful tool for radical reactions through visible-light-induced single-electron-transfer (SET) processes. Commonly used photocatalysts such as [Ru(bpy)3](2+) and fac-[Ir(ppy)3] (bpy = 2,2'-bipyridine; ppy = 2-pyridylphenyl) have potential as one-electron reductants strong enough to reduce those fluoromethylating reagents, resulting in facile generation of the corresponding fluoromethyl radicals. Therefore, if we can design proper reaction systems, efficient and selective radical fluoromethylation would proceed without any sacrificial redox agents, i.e., via a redox-neutral process under mild reaction conditions: irradiation with visible light, including sunlight, below room temperature. It should be noted that examples of catalytic fluoromethylation of compounds with carbon-carbon multiple bonds have been limited until recent years. In this Account, we will focus on our recent research on photoredox-catalyzed fluoromethylation of carbon-carbon multiple bonds. First, choices of the photocatalyst and the fluoromethylating reagent and the basic concept involving a redox-neutral oxidative quenching cycle are explained. Then photocatalytic trifluoromethylation of olefins is discussed mainly. Trifluoromethylative difunctionalization reactions, i.e., simultaneous introduction of the CF3 group and a different functional group across carbon-carbon double bonds, are in the middle of the discussion. Oxy-, amino-, and ketotrifluoromethylation allow us to synthesize various organofluorine compounds bearing C(sp(3))-CF3 bonds. In addition, the synthesis of valuable trifluoromethylated alkenes is also viable when the olefins have an appropriate leaving group or undergo deprotonation. The present reaction system features high functional group compatibility and high regioselectivity. Furthermore, future prospects, especially trifluoromethylative difunctionalization of alkynes and difluoromethylation of alkenes, are also discussed.