The development of complexes featuring low‐valent, multiply bonded metal centers is an exciting field with several potential applications. In this work, we describe the design principles and extensive computational investigation of new organometallic platforms featuring the elusive manganese‐manganese bond stabilized by experimentally realized N‐heterocyclic carbenes (NHCs). By using DFT computations benchmarked against multireference calculations, as well as MO‐ and VB‐based bonding analyses, we could disentangle the various electronic and structural effects contributing to the thermodynamic and kinetic stability, as well as the experimental feasibility, of the systems. In particular, we explored the nature of the metal‐carbene interaction and the role of the ancillary η6 coordination to the generation of Mn2 systems featuring ultrashort metal‐metal bonds, closed‐shell singlet multiplicities, and positive adiabatic singlet‐triplet gaps. Our analysis identifies two distinct classes of viable synthetic targets, whose electrostructural properties are thoroughly investigated.

In the present work, we revisit the spectrum of the hexacyanocobaltate(III) ion, [Co(CN) 6 ] 3− , which has been considered a prototype complex in the coordination chemistry, with modern quantum chemistry methods. The main features have been describing by revealing the role of different effects, such as vibronic coupling, solvation and spin−orbit coupling. The UV−vis spectrum is composed by two bands ( 1 A 1g → 1 T 1g and 1 A 1g → 1 T 2g ), characterized by singlet−singlet metalcentered transitions, and a more intense third one, characterized by charge transfer transition. There is also a small band shoulder. The first two are symmetry-forbidden transitions in the O h group. Their intensity can only be explained by a vibronic coupling mechanism. For the band shoulder, additional to vibronic coupling, spin−orbit coupling is also necessary, since the transition is characterized as singlet to triplet, 1 A 1g → 3 T 1g .

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This work presents some modifications in the post-synthetic processing for a classical arsenic reagent: AsI3. In comparison with the widely used analog, the trichloride, arsenic triiodide presents several advantages such as low toxicity, air stability, and low volatility. It was used as a synthetic precursor in the preparation of a variety of arsenic(III) derivatives like arsines, arsenites, and thioarsenites. Besides that, AsI3 was submitted to a diversity-oriented Grignard reaction in the preparation of a homologous series of trialkyl arsines ranging from AsC3H9 to AsC12H27. The series was analyzed by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry to provide a trialkyl arsines library that can be used for the direct analysis of natural samples.