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We review the known chemistry of the cyaphide ion, (C≡P) - . This remarkable diatomic anion has been the subject of study since the late nineteenth century, however its isolation and characterization eluded chemists for almost a hundred years. In this mini-review, we explore the pioneering synthetic experiments that first allowed for its isolation, as well as more recent developments demonstrating that cyaphide transfer is viable in well-established salt-metathesis protocols. The physical properties of the cyaphide ion are also explored in depth, allowing us to compare and contrast the chemistry of this ion with that of its lighter congener cyanide (an archetypal strong field ligand and important organic functional group). Recent studies show that the cyaphide ion has the potential to be used as a versatile chemical regent for the synthesis of novel molecules and materials, hinting at many interesting future avenues of investigation., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Gold(III) π-complexes have been authenticated recently with alkenes, alkynes, and arenes. The key importance of Pd II π-allyl complexes in organometallic chemistry (Tsuji-Trost reaction) prompted us to explore gold(III) π-allyl complexes, which have remained elusive so far. The (P,C)Au III (allyl) and (methallyl) complexes 3 and 3' were readily prepared and isolated as thermally and air-stable solids. Spectroscopic and crystallographic analyses combined with detailed DFT calculations support tight quasi-symmetric η 3 -coordination of the allyl moiety. The π-allyl gold(III) complexes are activated towards nucleophilic additions, as substantiated with β-diketo enolates., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

It is well known that alkynes act as π-acids in the formation of complexes with metals. We found unprecedented attractive Au-π interactions in diacetylene-modified [core+exo]-type [Au 8 ] 4+ clusters. The 4-phenyl-1,3-butadiynyl-modified cluster has unusually short Au-C α distances in the crystal structure, revealing the presence of attractive interactions between the coordinating C≡C moieties and the neighboring bitetrahedral Au 6 core, which is further supported by IR and NMR spectra. Such weak interactions are not found in mono-acetylene-modified clusters, which indicates that they are specific for diacetylenic ligands. The attractive Au-π interactions are likely associated with the low energy of the π* orbital in the diacetylenic moieties, into which the valence electrons of the gold core may be back donated. The [Au 8 ] 4+ clusters show clear red-shifts of >10 nm with respect to the corresponding mono-acetylenic clusters in UV/Vis absorption bands, which indicates substantial electronic perturbation effects of the Au-π interactions., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The intrinsic features of (hetero-arene)-metal interactions have been elusive mainly because the systematic structure analysis of non-anchored hetero-arene-metal complexes has been hampered by their labile nature. We report successful isolation and systematic structure analysis of a series of non-anchored indole-palladium(II) complexes. It was revealed that there is a σ-π continuum for the indole-metal interaction, while it has been thought that the dominant coordination mode of indole to a metal center is the Wheland-intermediate-type σ-mode in light of the seemingly strong electron-donating ability of indole. Several factors which affect the σ- or π-character of indole-metal interactions are discussed., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)