Bulletin of Japan Society of Coordination Chemistry
Online ISSN : 1883-1737
Print ISSN : 1882-6954
ISSN-L : 1882-6954
Volume 71
Displaying 1-7 of 7 articles from this issue
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  • Kohtaro Osakada
    2018 Volume 71 Pages 3-11
    Published: May 31, 2018
    Released on J-STAGE: August 24, 2018
    JOURNAL FREE ACCESS

    Transition metal complexes, having the coordination bonds with strong covalent-bond characters, undergo various bondforming reactions, similar to the organo-transition metal complexes with a metal-carbon s-bond. This article reviews recent studies by the author and his co-workers on the multinuclear complexes of group 10 transition metal complexes having bridging Si- and Ge-ligands. Triangular triplatinum(0) complexes having three bridging diarylsilylene ligands are newly prepared, and undergo skeletal rearrangement on addition of alkynes. The complex with SiPh2 ligands catalyzes hydrosilylation of aromatic aldehydes and ketones with H2SiPh2. Detailed studies on the dipalladium and diplatinum complexes with bridging Si- and Geligands revealed unique chemical properties, such as activation of the Si–H bond of the ligand as well as bond forming reactions of the bridging germylene with germyl ligands. Tetra-, penta-, hexa-, and octa-nuclear Pd and Pt complexes with the bridging silylene and germylene ligands are obtained from heating a mixture of the metal-phosphine complexes, precursor of the Si- and Ge-ligands, and scavenger of the auxiliary ligands. Thus formed complexes react with metal halides and with the Si- and Gecompounds to produce new multinuclear transition metal complexes. The reactions occur reversibly because of kinetic lability of the multinuclear complexes with the bridging Si- and Ge-ligands.

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  • Yuzhong Liu, Omar M. Yaghi
    2018 Volume 71 Pages 12-17
    Published: May 31, 2018
    Released on J-STAGE: August 24, 2018
    JOURNAL FREE ACCESS

    Transition metal ions as a template method has been widely used in the field of supramolecular chemistry. The metal complexation is advantageous in making complex supramocluar architectures because it pre-organizes the ligands into a desirable orientation which faciliatates the following ring-closing reaction, with shorter synthetic steps and generally higher yield. In a similar fashion, this synthetic strategy has recently been adopted to make extended materials by linking the metal-coordinated building blocks with design principles of reticular synthesis. Individual building units are stitched together through strong covalent bond formation to yield long covalent molecular threads that are woven two- or three-dimensionally (2D or 3D), at regular intervals templated by the metal ions. For example, by linking functionalized tetrahedrally-shaped metal complexes with linear links through reversible imine bond formation, crystalline 3D covalent organic frameworks with diamond topology, COF-505 and COF-112, have been constructed by design. In particular, the metal templates can be post-synthetically removed so that the threads have high degrees of freedom to move in respect to each other, which leads to unusal mechanical properties of the woven materials.

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  • Janina Willkomm, Erwin Reisner
    2018 Volume 71 Pages 18-29
    Published: May 31, 2018
    Released on J-STAGE: August 24, 2018
    JOURNAL FREE ACCESS

    Converting sunlight into storable chemical energy carriers, such as dihydrogen (H2), through light-driven splitting of water is a widely studied approach to secure future energy supplies and sustainability. Molecular complexes based on inexpensive and earthabundant 3d transition metals have been extensively explored as catalysts for the reduction of water to H2. Among these, cobalt complexes with an oxime functionality (i.e., cobaloxime and cobalt diimine-dioxime) efficiently reduce protons in pure water with low to moderate overpotentials, and they have been shown to remain active under aerobic conditions. Based on their simple and straightforward synthesis in addition to their excellent electrochemical properties, they are often applied as the first-choice catalyst when testing new materials or introducing new concepts for H2 evolution. In this review, their basic electrochemical and electrocatalytic properties as well as mechanistic investigations will be summarized, followed by an overview of their application in photocatalysis. Finally, their integration with (nano)materials for (photo)electrocatalytic H2 evolution is presented and discussed.

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  • Hiroshi Sato
    2018 Volume 71 Pages 30-38
    Published: May 31, 2018
    Released on J-STAGE: August 24, 2018
    JOURNAL FREE ACCESS

    Porous materials with infinite number of nanometer-sized pores are ubiquitous materials in our daily life as functional substances that efficiently separate or remove small molecules such as gas molecules. Recently, a new porous material called“porous coordination polymer (PCP)” or “metal–organic framework (MOF)” has been developed and actively studied because of their prominent functions for storage, separation, catalysis, etc. The advantage for the synthesis of PCP/MOF is its designable framework obtained by combinations of metal ions and organic ligands for various sizes, shapes and chemical properties of pores at the molecular level. One of the unique features of PCP/MOF compared with other conventional porous materials is that it is crystalline, but it can flexibly change its structure and provide exotic porous properties. In this review, we will present the synthesis, functions and mechanisms of unique porous functional materials in which “rigidity” and “flexibility” act in concert with each other. Especially, we will focus on the PCPs/MOFs showing (1) guest-responsive and (2) photo-responsive properties.

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  • Shohei Tashiro
    2018 Volume 71 Pages 39-48
    Published: May 31, 2018
    Released on J-STAGE: August 24, 2018
    JOURNAL FREE ACCESS

    In this account, a new method for the creation of porous functional materials based on the self-organization of metallomacrocycles is described. For instance, the authors have developed a new series of porous molecular crystals, metal–macrocycle frameworks (MMFs), through crystallization of Pd3-macrocycles. It was also found that MMFs with multiple binding pockets on the pore surface served as excellent host frameworks for precise molecular arrangement, chiral recognition, sizespecific catalytic reaction, and in situ observation of a molecular adsorption process. In addition, the one-dimensional assembly of metallomacrocycles is also described as another approach for the construction of metal-modified pores and various metal arrays. This method is therefore one of the promising ways to develop unique porous materials such as highly efficient and selective catalysts based on the precise arrangement of guest compounds and metal ions in the pores.

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  • Yoshiaki Nishibayashi
    2018 Volume 71 Pages 49-55
    Published: May 31, 2018
    Released on J-STAGE: August 24, 2018
    JOURNAL FREE ACCESS

    This paper describes our recent progress in catalytic nitrogen fixation by using transition metal-dinitrogen complexes as catalysts. Novel reaction systems for the catalytic transformation of molecular dinitrogen into ammonia and hydrazine undermild reaction conditions have been achieved by the molybdenum-, iron-, cobalt-, and vanadium-dinitrogen complexes as catalysts. New findings presented in this paper may provide a new approach to the development of economical nitrogen fixation in place of energy-consuming Haber-Bosch process.

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  • Yasutaka Kitagawa, Toru Saito, Kizashi Yamaguchi
    2018 Volume 71 Pages 57-68
    Published: May 31, 2018
    Released on J-STAGE: August 24, 2018
    JOURNAL FREE ACCESS

    A broken-symmetry (BS) method is now widely used for systems that involve (quasi) degenerate frontier orbitals because of their lower cost of computations. The BS method splits up-spin and down-spin electrons into two differentspatial orbitals. Within the BS method, therefore, a singlet spin state of the degenerate system is expressed as a spinpolarized state e.g. a singlet diradical. However the spin-polarized wavefunction suffers from a serious problem calleda spin contamination error. An approximate spin projection (AP) method can eliminate the error from the BS solution by assuming the Heisenberg model, and one can obtain molecular energies and its derivatives without the error. In thisaccounts, we illustrate a theoretical background of the BS and AP methods, starting from a bond dissociation of the simplest H2 molecule. And we also show some examples of its application especially for Cr(II)2 complex that is a typicalspin-polarized system with a multiple bond.

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