Reverse Sandwich Structures from Interplay between Lone Pair- π-Hole Aetom-Directed C•••dz2[M] and Halogen Bond Interactions

4-Bromo- and 4-iodo-5-nitrophthalonitriles (BNPN and INPN, respectively) were cocrystallized with the metal acetylacetonates [M(acac)(2)] (M = Pd (1), Pt (2)) to give the three adducts 1 center dot 23NPN, 2 center dot 2BNPN, and 1.2INPN, exhibiting reverse arene sandwich solid-state structures. The inspection of the XRD data for the adducts revealed new types of (lone pair)[M]center dot center dot center dot pi-hole noncovalent interactions, namely atomdirected C center dot center dot center dot d(z)2[M] noncovalent contacts. In addition, C-X center dot center dot center dot(O,O) (X = I, Br) bifurcated halogen bonds (XBs) along with some other types of short contacts were recognized. The XRD experiments were supported by Hirshfeld surface analysis and DFT calculations: i.e., topological analysis of the electron density distribution within the framework of the QTAIM method at the omega B97XD/DZP-DKH level of theory. Estimated energies of all studied noncovalent contacts vary from 0.6 to 3.8 kcal/mol.