Homogeneous gold catalysis has attracted intensive interest from synthetic chemists because of its significant advances in the field of carbon-carbon and carbon-heteroatom bond formations. The gold catalysts are generally recognized as soft Lewis acids which allow to activate carbon-carbon multiple bonds towards a variety of nucleophiles under mild conditions. To elucidate the precise catalytic mechanism without speculation, much effort has been devoted to the isolation and characterization of organogold intermediates. In particular, it has been proposed that various alkenylgold complexes play crucial roles as the active species involved in catalytic transformation of alkynes and allenes. This paper overviews recent advances in the synthesis of alkenylgold complexes relevant to catalysis and focuses mainly on mechanistic insights into the intramolecular cyclization of alkyne and allene substrates containing hetero- and carbonucleophiles with the aim of contributing to a further understanding of the unique and distinctive gold-catalyzed reactions.

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Inorganic ligands, such as polyoxovanadates, may offer a new way to further expand the boundary of coordination chemistry for inorganic complexes featuring a part of metal oxide structures. Many industrially important applications require metal oxides that support modern electronics, magnets, sensors, and catalysts. However, because of the complexity of the oxides, it is difficult to elucidate the structure and property relationships. Investigating the reactivity and physical properties by modifying the oxide structures in a systematic manner is challenging to test the hypothesis of a postulated mechanism. For these reasons, designing a model complex to replicate those properties and reactivity is important by utilizing polyoxometalates as all-inorganic ligands. In this article, the fundamental chemistry of polyoxovanadates is described from the point of inorganic ligand system by the classification based on their structural building units.

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Nirtogenases are a class of enzymes that catalyze the reduction of N₂ to NH₃ under ambient conditions in the presence of protons and electrons. The active site of the most prevalent nitrogense is called as the FeMo-cofactor, which is often designated as the M-cluster. It consists of one molybdenum, seven irons, and several sulfur atoms, and represents the most complex metal-sulfur cluster in biology. Some homologues containing vanadium or iron in place of molybdenum exist in alternative nitrogenases, while a precursor of FeMo-cofactor was also identified as an all-iron homologue. Recent crystallographic and biochemical studies on nitrogenases uncovered some important clues about the structurefunction relationship of the nitrogenase active sites, such as the precise structure of the FeMo-cofactor, unique catalytic functions of the FeMo-cofactor and its homologues, and the detailedmechanistic insights in the nitrogen fixation. Transition-metal mediated conversion of small molecules that contain triple bonds has been of interest to the community of coordination chemistry, and this contribution introduces some important progresses in the nitrogenase chemistry/biochemistry made in recent years.

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Inspired by the efficiency displayed by enzymes, self-assembled cages with nanometer-sized cavities have been demonstrated as molecular flasks which can alter reaction pathways to show unusual activity and selectivity by the cavities. In contrast to numerous examples of organic reactions, organometallic catalysts within self-assembled cages are limited. Here, recent examples of gold(I)-catalyzed transformations within self-assembled cages are summarized. These results suggest that confined cavities that can encapsulate organometallic catalysts will provide and stabilize new active species for organometallic reactions which have previously been unobservable.

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