Intermolecular Metal-Involving Pnictogen Bonding: The Case of σ-(Sb III )-Hole···d z 2 [Pt II ] Interaction.

Cocrystallizations of trans -[PtX' 2 (NCNR 2 ) 2 ] (R 2 = Me 2 , X' = Cl 1a , Br 1b , I 1c ; R 2 = (CH 2 ) 5 , X' = I 2c ) with SbX 3 (X = Cl, Br, I) gave 1:2 cocrystals 1a ·2SbCl 3 , 1b ·2SbBr 3 , 1c ·2SbCl 3 , 1c ·2SbBr 3 , 1c ·2SbI 3 , and 2c ·2SbI 3 . In all six X-ray structures, the association of the molecular coformers is achieved mainly by Sb III ···d z 2 [Pt II ] 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 z 2 -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.