The Covalent AuI-AuI Bond in (AuF)n (n = 2∼4): A Perspective to Understand the Closed-Shell AuI···AuI Interaction

The nature of closed-shell Au^I···Au^I attraction is still a conundrum in theoretical chemistry. However, for Au₂F₂ with a zigzag conformation, the d¹⁰-d¹⁰ closed-shell interaction between the AuF monomers is demonstrated as a coordinate covalent bond. Chemical bonding analysis reveals that the strong Au^I···Au^I attraction is caused by the participation of the extraordinary active 5d orbital of Au. Based on our study, one of the 5d orbitals of the Au atom is activated to hybridize with its 6s and 6p orbitals to form hybridized dsp² orbitals, where each Au atom is both an electron donor (Lewis base) and acceptor (Lewis Acid) in dimerization. Actually, the closed-shell Au^I···Au^I interaction in the zigzag conformation of Au₂X₂ (X = F, Cl, Br, I, or NH₂) is covalent. Our results provide a rather simple but clear-cut example, where mysterious Au^I···Au^I attractions can be possibly explained by the covalent bond theory.

Experimental and theoretical evidence of attractive interactions between dianions: [PdCl4]2-⋯[PdCl4]2

Inspection of the arrangement of tetrachloridopalladate(II) centers in a crystalline solid places the Cl of one [PdCl₄]^2- directly above the Pd center of its neighbor. A survey of the CSD provides 22 more examples of such MX₄^2-⋯MX₄^2- complexes, with M being a Group 10 metal and X = Cl, Br, or I. Quantum calculations attribute this arrangement to a π-hole bond wherein Cl lone pairs of one unit transfer charge to vacant orbitals above the Pd center of its neighbor. The stabilizing effect of this bond must overcome the strong Coulombic repulsion between the two dianions, which is facilitated by a polarizable environment as would be present in a crystal, but much more so when the effects of the neighboring counterions are factored in. These conclusions are extended to other [MX₄]^2- homodimers, where M represents other members of Group 10, namely Ni and Pt.

Bi- and trinuclear coinage metal complexes of a PNNP ligand featuring metallophilic interactions and an unusual charge separation

A selective synthesis of bi- and trinuclear complexes featuring a tetradentate monoanionic PNNP ligand is presented. The binuclear coinage metal complexes show a typical fourfold coordination for Cu and Ag, which changes to a bifold coordination for Au. The latter is accompanied by an unusual charge separation. Optical properties are investigated using photoluminescence spectroscopy and complemented by time-dependent density-functional-theory calculations. All compounds demonstrate clearly distinguished features dependent on the metals chosen and differences in the complex scaffold.

Words in supramolecular chemistry: the ineffable advances of polyiodide chemistry

Polyiodide chemistry has a rich history deeply intertwined with the development of supramolecular chemistry. Technological and theoretical interest in polyiodides has not diminished in the last decade, quite the contrary; yet the advances this perspective intends to cover are muddled by the involution of supramolecular vocabulary, preventing their unbiased discussion. Herein we discuss the pressing necessity of ordering the current babel of novel - and less so - supramolecular terms. Shared decisions at the community level might be required to shape the field into a harmonious body of knowledge, dominated by concepts rather than words. Secondary, σ-hole and halogen bonding schools of thought are all addressed here, together with their respective impact on the field. Then, on the basis of a shared vocabulary, a discussion of polyiodide chemistry is presented, starting with a revisited view of triiodide. The contemporary fields of supramolecular caging and polyiodide networks are then discussed, with emphasis on how the terms we choose to use deeply affect scientific progress.

Not Only Hydrogen Bonds: Other Noncovalent Interactions

In this review, we provide a consistent description of noncovalent interactions, covering most groups of the Periodic Table. Different types of bonds are discussed using their trivial names. Moreover, the new name “Spodium bonds” is proposed for group 12 since noncovalent interactions involving this group of elements as electron acceptors have not yet been named. Excluding hydrogen bonds, the following noncovalent interactions will be discussed: alkali, alkaline earth, regium, spodium, triel, tetrel, pnictogen, chalcogen, halogen, and aerogen, which almost covers the Periodic Table entirely. Other interactions, such as orthogonal interactions and π-π stacking, will also be considered. Research and applications of σ-hole and π-hole interactions involving the p-block element is growing exponentially. The important applications include supramolecular chemistry, crystal engineering, catalysis, enzymatic chemistry molecular machines, membrane ion transport, etc. Despite the fact that this review is not intended to be comprehensive, a number of representative works for each type of interaction is provided. The possibility of modeling the dissociation energies of the complexes using different models (HSAB, ECW, Alkorta-Legon) was analyzed. Finally, the extension of Cahn-Ingold-Prelog priority rules to noncovalent is proposed.