Intermolecular Metal-Involving Pnictogen Bonding: The Case of σ-(SbIII)-Hole···dz2[PtII] Interaction.

ABSTRACT

Cocrystallizations of trans-[PtX'2(NCNR2)2] (R2 = Me2, X' = Cl 1a, Br 1b, I 1c; R2 = (CH2)5, X' = I 2c) with SbX3 (X = Cl, Br, I) gave 12 cocrystals 1a·2SbCl3, 1b·2SbBr3, 1c·2SbCl3, 1c·2SbBr3, 1c·2SbI3, and 2c·2SbI3. In all six X-ray structures, the association of the molecular coformers is achieved mainly by SbIII···dz2[PtII] 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 dz2-orbital of the positively charged platinum(II) sites, thus forming a pnictogen bond whose energy falls in the range between -7.3 and -16.9 kcal/mol.