Pnictogen Bonds between Electrophilic Pnictogens and Nucleophilic Metal Centers: A Combined Database Survey and Theoretical Investigation

d⁸ and d¹⁰ metal centers showing nucleophilic properties can function as Lewis bases in the establishment of pnictogen bonding (PnB). In this work, PnB interactions between electrophilic pnictogens (R₃Pn) and nucleophilic metal centers (Ni/Pd and Ag/Au) were systematically studied by quantum chemical calculations combined with a search of the Cambridge Structural Database (CSD). Owing to the increased nucleophilicity, d⁸ metal centers generally form enhanced PnBs with R₃Pn relative to d¹⁰ ones, leading to a partially covalent character of Pn···Ni/Pd contacts. In most cases, a certain amount of charge is transferred from the metal compounds to the donor molecules. Energy decomposition analysis revealed that the attraction of metal-involving PnBs originates mainly from the electrostatic interaction, while the orbital term and the dispersion component also play an important role. In addition, a number of crystal structures consisting of metal-participating PnBs were collected from the CSD, to provide crystallographic evidence of such interactions.