Metal-mediated reactions between dialkylcyanamides and acetamidoxime generate unusual (nitrosoguanidinate)nickel(ii) complexes

Abstract

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.

Bromo‐ and Polybromoantimonates(V): Structural and Theoretical Studies of Hybrid Halogen‐Rich Halometalate Frameworks

“…To investigate the nature of Br⋅⋅⋅Br interactions in all new compounds, as well as in the already known Sb V polybromides, we carried out DFT calculations and performed topological analysis of the electron density distribution within the framework of Bader's theory (QTAIM method) for corresponding model supramolecular clusters (obtained from XRD data) featuring Br⋅⋅⋅Br contacts shorter than the sum of Bondi's van der Waals radii . This approach has already been used in our studies of different non‐covalent interactions, for example, hydrogen, halogen, and chalcogen bonding, stacking, as well as metallophilic interactions . The results are summarized in Table S1 (in the Supporting Information; the contour line diagrams of the Laplacian distribution ▿ 2 ρ ( r ), bond paths, and selected zero‐flux surfaces for 3 and 4 are shown in Figures and .…”

1D and 2D Polybromotellurates(IV): Structural Studies and Thermal Stability

“…The DFT calculations and topological analysis of the electron density distribution within the framework of Bader's theory (QTAIM method) were carried out for model supramolecular clusters 1 and 2 (see SI) featuring intermolecular non‐covalent interactions Br ··· Br to quantify energies of these contacts from a theoretical viewpoint. This approach has already been successfully used for different non‐covalent interactions . The results are summarized in Table S1 (SI), the contour line diagrams of the Laplacian distribution ∇ 2 ρ(r), bond paths, and selected zero‐flux surfaces for 1 and 2 are shown in Figure and Figure .…”

2,2′‐Azobispyridine in Phosphorus Coordination Chemistry: A New Approach to 1,2,4,3‐Triazaphosphole Derivatives

“…This approach has already been successfully used by us upon studies of different noncovalent interactions (viz. hydrogen, halogen and chalcogen bonding, metallophilic interactions, stacking) in various organic, organometallic, and coordination compounds . The QTAIM analysis did not reveal the presence of appropriate bond critical points (3, –1) for the intramolecular noncovalent interactions N ··· P in 2 , 4 , and 6 , and negligible values of the Wiberg bond indices for these contacts (viz.…”