The reaction of cis-[PdCl(CNXyl)] (Xyl = 2,6-MeCH) with various 1,3-thiazol- and 1,3,4-thiadiazol-2-amines in chloroform gives a mixture of two regioisomeric binuclear diaminocarbene complexes. For 1,3-thiazol-2-amines the isomeric ratio depends on the reaction conditions and kinetically (KRs) or thermodynamically (TRs) controlled regioisomers were obtained at room temperature and on heating, respectively. In CHCl solutions, the isomers are subject to reversible isomerization accompanied with the cleavage of Pd-N and С-N bonds in the carbene fragment XylNCN(R)Xyl. Results of DFT calculations followed by the topological analysis of the electron density distribution within the formalism of Bader's theory (AIM method) reveal that in CHCl solution the relative stability of the regioisomers (∆G = 1.2 kcal/mol; ∆G = 3.2 kcal/mol) is determined by the energy difference between two types of the intramolecular chalcogen bonds, viz. S•••Cl in KRs (2.8-3.0 kcal/mol) and S•••N in TRs (4.6-5.3 kcal/mol). In the case of the 1,3,4-thiadiazol-2-amines, the regioisomers are formed in approximately equal amounts and, accordingly, the energy difference between these species is only 0.1 kcal/mol in terms of ∆G (∆G = 2.1 kcal/mol). The regioisomers were characterized by elemental analyses (C, H, N), HRESI-MS and FTIR, 1D (H, C) and 2D (H,H-COSY, H,H-NOESY, H,C-HSQC, H,C-HMBC) NMR spectroscopies, and structures of six complexes (three KRs and three TRs) were elucidated by single-crystal X-ray diffraction.

The dihalomethane-halide H 2 C(X)-X•••X -(X = Cl, Br) halogen bonding was detected in a series of the cis-[PdX(CNCy){C(NHCy)=NHC 6 H 2 Me 2 NH 2 }]X•CH 2 X 2 (X = Cl, Br) associates by single-crystal XRD followed by DFT calculations. Although ESP calculations demonstrated that the σ-hole of dichloromethane is the smallest among all halomethane solvents (the maximum electrostatic potential is only 2.6 kcal/mol), the theoretical DFT calculations followed

In the current study, we evaluated the solubility of a number of organometallic species and showed that it is noticeably improved in diiodomethane when compared to other haloalkane solvents. The better solvation properties of CH I were associated with the substantially better σ-hole-donating ability of this solvent, which results in the formation of uniquely strong solvent-(metal complex) halogen bonding. The strength of the halogen bonding is attenuated by the introduction of additional halogen atoms in the organometallic species owing to the competitive formation of more favourable intermolecular complex-complex halogen bonding. The exceptional solvation properties of diiodomethane and its inertness towards organometallic species make this solvent a good candidate for NMR studies, in particular, for the acquisition of spectra of insensitive spins.

A new application for bis­(cyclometalated) iridium­(III) species containing ancillary acyclic diaminocarbene ligands, viz. for sensing of mercury­(II) ions, is disclosed. A family of bis­(cyclometalated) iridium­(III) species supported by both parent isocyanide and acyclic diaminocarbene ligands was prepared, and their electrochemical and photophysical properties were evaluated, revealing efficient blue-green phosphorescence in solution with quantum yields of up to 55%. We uncovered that the photophysical properties of these complexes are dramatically altered by the presence of metal ions and that the complex [Ir­(ppy)2(CN)­{C­(NH2)­(NHC6H4-4-X)}] with an ADC ligand reacts selectively with Hg2+ ions, enabling its use for sensing of mercury­(II) ions in solution. The limit of detection was as low as 2.63 × 10–7 M, and additional mechanistic studies indicated the formation of an unusual dinuclear iridium­(III) cyclometalated intermediate, bridged by a mercury dicyano fragment as a driving force of mercury sensing.

The isocyanide trans‐[PdBr2(CNC6H4‐4‐X′)2] (X′=Br, I) and nitrile trans‐[PtX2(NCC6H4‐4‐X′)2] (X/X′=Cl/Cl, Cl/Br, Br/Cl, Br/Br) complexes exhibit similar structural motif in the solid state, which is determined by hitherto unreported four‐center nodes formed by cyclic halogen bonding. Each node is built up by four Type II C−X′⋅⋅⋅X−M halogen‐bonding contacts and include one Type I M−X⋅⋅⋅X−M interaction, thus giving the rhombic‐like structure. These nodes serve as supramolecular synthons to form 2D layers or double chains of molecules linked by a halogen bond. Results of DFT calculations indicate that all contacts within the nodes are typical noncovalent interactions with the estimated strengths in the range 0.6–2.9 kcal mol−1.