Nucleophilicity of the Nitrile N Atom Whose Lone Pair Is Blocked by Metal Coordination. The π-Hole Interaction between an Arene Carbon and the Metal-Bound Nitrile Nitrogen

Cocrystallization of CuI with NCNMe2 in the presence of substituted perfluoroarenes─iodoperfluorobenzene (IFB), 4,4'-diiodoperfluorobiphenyl (4,4'-FIBP), and 4-bromoperfluorobenzonitrile (4-BrFBN)─led to the formation of three types of adducts 1·2(IFB), 1·4,4'FIBP, and 1·4-BrFBN (1 is Cu4I4(NCNMe2)4), all studied by X-ray crystallography. In these cocrystals, the coordinated nitrile N atom (whose electron pair is engaged in metal coordination) still acts as an electron donor, forming π-hole interactions, specifically, π-holearene···Nnitrile, with the perfluoroarenes. These interactions were examined in the context of their occurrence alongside other interactions involving C atoms of the electron-deficient aromatic rings and nucleophilic atoms of the copper cluster. Comprehensive theoretical calculations, including MEP, QTAIM/NCI plot analysis, EDA, ELF projections, and ETS-NOCV calculations, revealed that the nitrile ligand N atom maintains significant negative potential and that π-hole interactions are energetically more favorable than σ-hole interactions in the studied systems. This nucleophilicity is based on a noticeable contribution of the heterocumulene form, Cu-N-═C═N+Me2, in the resonance hybrid of Cu-bound NCNMe2: a phenomenon influenced by both the coordination and the conjugation between the NR2 and CN groups The discovery of π-holearene···Nnitrile contacts adds a new dimension to our understanding of coordinated push-pull nitriles, in particular dialkylcyanamides, revealing that the coordinated nitrile N atom can still function as a nucleophile in noncovalent binding.

Copper-Catalyzed, Ligand-Controlled N(sp3)- or N(sp)-Selective Arylation of Cyanamides

Cyanamides possess both nucleophilic and electrophilic centers, and their arylation reactions are known to proceed at N(sp3) and C(sp) sites, leading to N-aryl cyanamides or amidines. N(sp) selectivity has also been reported only in the presence of amines, thus leading to guanidines. Herein, we report a general copper-catalyzed ligand-controlled Chan-Lam-Evans arylation of cyanamides proceeding regioselectively at the N(sp3) or N(sp) atoms and leading to either N-aryl cyanamides or dissymmetric carbodiimides. The nature of the ligand, either a bipyridine or a diamine, controls the product distribution and thus offers a divergent entry to useful building blocks from readily available cyanamides.

Copper(II) Prevents the Saccarine-Dialkylcyanamide Coupling by Forming Mononuclear (Saccharinate)(Dialkylcyanamide)copper(II) Complexes

The reaction in the system CuII/sacNa(H)/NCNR2 (sacNa(H) = sodium saccharinate (saccharin); R = Me, Et) results in the formation of the complexes [Cu(sac)2(NCNR2)(H2O)2] (R = Me 1, Et 2) instead of the expected products derived from the saccharin–cyanamide coupling. Complexes 1, 2, and hydrate 1·2H2O were characterized by IR, AAS (Cu%), TGA, and also by single-crystal X-ray diffraction for 1 and 1·2H2O. An integrated computational study of model structure 1 in the gas phase demonstrates that the Cu–Ncyanamide and Cu–Nsac coordination bonds exhibited a single bond character, polarized toward the N atom and almost purely electrostatic, with the calculated vertical total energies for the Cu–Ncyanamide and Cu–Nsac of 43.6 and 156.4 kcal/mol, respectively. These data confirmed that the copper(II) completely blocks the nucleophilic centers of ligands via coordination, thus preventing the saccharin–cyanamide coupling.

Highly soluble Cu(i)-acetonitrile salts as building blocks for novel phosphorus-rich organometallic-inorganic compounds

The synthesis of the air-stable and highly soluble Cu(i)-acetonitrile salts [Cu(CH3CN)3.5][FAl] (1) ([FAl] = FAl{OC(C6F10)(C6F5)}3) and [Cu(CH3CN)4][TEF] (2) ([TEF] = Al{OC(CF3)3}4) is presented. Compound 1 reacts with the organometallic polyphosphorus complexes [Cp2Mo2(CO)4(η2-P2)] (A) and [(Cp*Fe(η5-P5)] (B) and salt 2 reacts with B to form one new (3) and three unprecedented (4-6) phosphorus-rich Cu(i) dimers with the general formulas [Cu2(μ,η1:η1-A)2(η2-A)2][FAl]2 (3), [Cu2(μ,η1:η1-A)2(η1-CH3CN)4][FAl]2 (4), [Cu2(μ,η1:η1-B)2(η1-CH3CN)4][FAl]2 (5) and [Cu2(μ,η1:η1-B)2(η1-CH3CN)4][TEF]2 (6).

Halobismuthates with halopyridinium cations: appearance or non-appearance of unusual colouring

A series of chloro- and bromobismuthate complexes with bromopyridinium cations were prepared and characterized by XRD analysis and diffuse reflectance spectroscopy.