Upgrade of Weak σ-hole Bond Donors via Cr(CO)3 Complexation.

Molecular recognition mediated by s-hole interactions is enhanced as the electrostatic potential at the σ-hole becomes increasingly positive. Traditional methods to strengthen σ-hole donor ability of atoms such as halogens often involve covalent modifications, such as, introducing electron-withdrawing substituents (neutral or positively charged) or electrochemical oxidation. Metal coordination, a relatively underexplored approach, offers a promising alternative.

Nucleophilicity of the Nitrile N Atom Whose Lone Pair Is Blocked by Metal Coordination. The π-Hole Interaction between an Arene Carbon and the Metal-Bound Nitrile Nitrogen.

Cocrystallization of CuI with NCNMe in the presence of substituted perfluoroarenes─iodoperfluorobenzene (IFB), 4,4'-diiodoperfluorobiphenyl (4,4'-FIBP), and 4-bromoperfluorobenzonitrile (4-BrFBN)─led to the formation of three types of adducts ·2(IFB), ·4,4'FIBP, and ·4-BrFBN ( is CuI(NCNMe)), all studied by X-ray crystallography. In these cocrystals, the coordinated nitrile N atom (whose electron pair is engaged in metal coordination) still acts as an electron donor, forming π-hole interactions, specifically, π-hole···N, with the perfluoroarenes. These interactions were examined in the context of their occurrence alongside other interactions involving C atoms of the electron-deficient aromatic rings and nucleophilic atoms of the copper cluster.

Key-to-lock halogen bond-based tetragonal pyramidal association of iodonium cations with the lacune rims of beta-octamolybdate.

The structure-directing "key-to-lock" interaction of double σ-(I)-hole donating iodonium cations with the O-flanked pseudo-lacune rims of [β-MoO] gives halogen-bonded iodonium-beta-octamolybate supramolecular associates. In the occurrence of their tetragonal pyramidal motifs, deep and broad σ-(I)-holes of a cation recognize the molybdate backbone, which provides an electronic pool localized around the two lacunae. The halogen-bonded I⋯O linkages in the structures were thoroughly studied computationally and classified as two-center, three-center bifurcated, and unconventional "orthogonal" I⋯O halogen bonds.

Intermolecular Metal-Involving Pnictogen Bonding: The Case of σ-(Sb)-Hole···d[Pt] Interaction.

Cocrystallizations of -[PtX'(NCNR)] (R = Me, X' = Cl , Br , I ; R = (CH), X' = I ) with SbX (X = Cl, Br, I) gave 1:2 cocrystals ·2SbCl, ·2SbBr, ·2SbCl, ·2SbBr, ·2SbI, and ·2SbI. In all six X-ray structures, the association of the molecular coformers is achieved mainly by Sb···d[Pt] metal-involving intermolecular pnictogen bonding. Density functional theory (DFT) calculations (based on experimentally determined geometries) using both gas-phase and solid-state approximations revealed that a σ-(Sb)-hole interacts with an area of negative potential associated with the d-orbital of the positively charged platinum(II) sites, thus forming a pnictogen bond whose energy falls in the range between -7.

Metal-Induced Enhancement of Tetrel Bonding. The Case of C⋅⋅⋅X-Ir (X=Cl, Br) Tetrel Bond Involving a Methyl Group.

In X-ray structures of the isomorphic mer-[IrX(THT)(CNXyl)] (X=Cl 1, Br 2; THT=tetrahydrothiophene; Xyl=2,6-MeCH-) complexes, we revealed short intermolecular contacts between the C-atom of an isocyanide methyl group and halide ligands of another molecule. Geometrical consideration of the X-ray data and analysis of appropriate DFT studies allowed the attribution of these contacts to C⋅⋅⋅X-Ir (X=Cl, Br) tetrel bond. Specifically, through the application of DFT calculations and various theoretical models, the presence of tetrel bonding interactions was validated, and the contribution of the C⋅⋅⋅X-Ir interaction was assessed.