(Isocyano Group π-Hole)....[dz2-MII] Interactions of (Isocyanide)[MII] Complexes, in which Positively Charged Metal Centers (d8-M=Pt, Pd) Act as Nucleophiles

Inspection of the X-ray structures of the newly prepared trans-[M-II(CNXyl)(2)(DAPT)(2)]Cl(BF4) (M=Pd, Pt; Xyl=2,6-Me2C6H3; DAPT=4,6-diaminopyrimidine-2(1H)-thione) complexes and the appropriate Hirshfeld molecular surface analysis allowed the recognition of the previously unknown pi-hole...metal interactions between a ligated isocyano group (acting as a pi-hole donor) and the positively charged d(8)-Pt-II and d(8)-Pd-II metal centers (acting as nucleophiles); this is the first identification of pi-hole...metal interactions with triple-bond species. Results of DFT calculations followed by the topological analysis of the electron density distribution within the framework of Bader's theory (quantum theory of atoms in molecules, QTAIM) confirmed the presence of these contacts. The electrostatic surface potential calculations indicated that pi-hole .. metal contacts are formed upon interaction between the electrophilic isocyano C atom (pi-hole donor) and the nucleophilic dz2 orbital of the metal centers, which act as pi-hole acceptors. Available CCDC data were processed from the perspective of the pi-hole...metal interactions with isocyanide ligands, and their analysis disclosed the role of metal nucleophilicity in the corresponding pi-hole acceptor ability.