The nitrosoguanidinate complex [Ni{NH═C(NMe)NN(O)}] (1) was cocrystallized with I and sym-trifluorotriiodobenzene (FIB) to give associates 1·2I and 1·2FIB. Structures of these solid species were studied by XRD followed by topological analysis of the electron density distribution within the framework of Bader's approach (QTAIM) at the M06/DZP-DKH level of theory and Hirshfeld surface analysis. Our results along with inspection of XRD (CCDC) data, accompanied by the theoretical calculations, allowed the identification of three types of Ni···I contacts. The Ni···I semicoordination of the electrophilic nickel(II) center with electron belt of I was observed in 1·2I, the metal-involving halogen bonding between the nucleophilic nickel(II)-d center and σ-hole of iodine center was recognized and confirmed theoretically in the structure of [FeNi(CN)(IPz)(HO)] (IPz = 4-N-coordinated 2-I-pyrazine), whereas the arrangement of FIB in 1·2FIB provides a boundary case between the semicoordination and the halogen Ni···I bondings. In 1·2I and 1·2FIB, noncovalent interactions were studied by variable temperature XRD detecting the expansion of noncovalent contacts with preservation of covalent bond lengths upon the temperature increase from 100 to 300 K. The nature and energies of all identified types of the Ni···I noncovalent interactions in the obtained (1·2I and 1·2FIB) and in the previously reported ([FeNi(CN)(IPz)(HO)], [NiL](I)·2I (L = o-phenylene-bis(dimethylphosphine), [NiL]I (L = 1,4,8,11-tetra-azacyclotetradecane), Ni(en)][AgI] (en = ethylenediamine), and [NiL](ClO) (L = 4-iodo-2-((2-(2-(2-pyridyl)ethylsulfanyl)ethylimino)methyl)-phenolate)) structures were studied theoretically. The estimated strengths of these Ni···I noncovalent contacts vary from 1.6 to 4.1 kcal/mol and, as expected, become weaker on heating. This work is the first emphasizing electrophilic-nucleophilic dualism of any metal center toward noncovalent interactions.

Fluorinated iodoarenes such as 1,4-diiodotetrafluorobenzene (1,4-FIB) and 1,3,5-triiodotrifluorobenzene (1,3,5-FIB) were cocrystallized with the nitrosoguanidinate-nickel­(II) species [Ni­{NHC­(NRR′)­NN(O)}2] (RR′ = Me2 1, RR′ = MePh 2, RR′ = (CH2)5 3) and structures of three adducts were studied by X-ray crystallography. The Hirshfeld surface analysis for the X-ray structures of 1•(1,4-FIB), 2•2­(1,3,5-FIB), and 3•2­(1,4-FIB) revealed that crystal packing is determined primarily by intermolecular contacts involving hydrogen and halogen atoms. In addition, FIBs are linked to the O atom of the nitroso-group via π-hole of the arene cores thus representing an unreported noncovalent bonding pattern for iodofluorobenzenes; it belongs to lone pair­(O)−π hole interactions, lp­(O)−πh. Results of DFT calculations followed by QTAIM analysis at the M06/DZP-DKH level of theory revealed that estimated energies of the lp­(O)−πh interactions are 1.3–2.2 kcal/mol (in experimental X-ray geometries of model supramolecular adducts) or 0.9–2.4 kcal/mol (in equilibrium optimized geometries of model supramolecular adducts). The geometry optimization procedure for model adducts does not change significantly the structural motifs of these systems indicating that lp­(O)−πh contacts are not determined exclusively by crystal packing effects, but also exist in the isolated “gas phase” form. Our processing of the CCDC database and the theoretical calculations for TAXZAW01, featuring the shortest O···arene distance, revealed five additional structures with overlooked lp­(O)−πh contacts involving iodofluoroarene cores.

The nitrosoguanidinate complexes [Ni{NH[double bond, length as m-dash]C(NR)NN(O)}] (R = Me1, (CH)O 2, (CH)3, (CH)4, (Me)Ph 5, Ph6, (p-MeCH)7) were obtained in low-to-moderate (12-26%) yields but reproducible yields in an unexpected metal-mediated reaction in MeOH between the nickel salt NiCl·2HO, N,N-disubstituted cyanamides NCNR, and the amidoxime MeC([double bond, length as m-dash]NOH)NH. These complexes were formed along with a spectrum of cyanamide-oxime coupling products. The IR and X-ray data indicate the delocalization within the NNO and NCN systems of the nitrosoguanidinate ligand. This delocalization was additionally confirmed by inspection of Wiberg bond indices for the selected bonds. In the X-ray structure of 5, the rare metallophilic contacts NiNi between stacks of the square-planar complexes were detected and these non-covalent interactions were studied by non-relativistic and relativistic DFT calculations and topological analysis of the electron density distribution within the framework of Bader's theory (QTAIM method). The estimated strength of the NiNi interactions is 1.3-1.9 kcal mol and they are mostly determined by crystal packing effects and weak attractive interactions between adjacent metal centers due to the overlapping of their d and p orbitals.

The reaction of NiCl2•2H2O with acetamidoxime (MeC(NH2)=NOH) in the presence of PhCN in MeOH gave the cationic dimetallic complex [1]Cl4, bearing bridging O‐coordinated aminonitrone and chelating imidoylamidoxime ligands, derived from amidoxime‐PhCN coupling. The experimental data and theoretical calculations (M06/MDF10(Ni) and 6–31G*(other atoms) indicated that the aminonitrone form of amidoxime was stabilized only as a μ2‐O‐bridging ligand, whereas Noxime‐coordination was preferred rather than O‐coordination for monodentate‐coordinated amidoximes.