Halides Held by Bifurcated Chalcogen-Hydrogen Bonds. Effect of μ (S,N-H) Cl Contacts on Dimerization of Cl(carbene)Pd II Species.

The reaction of cis-[PdCl ₂ (CNCy) ₂ ] (1) with thiazol-2-amines (2-10) leads to the C,N-chelated diaminocarbene-like complexes [PdCl{ C(N(H)4,5-R ₂ -thiazol-2-yl)NHCy}(CNCy)] (11-14; 82-91%) in the case of 4,5-R ₂ -thiazol-2-amines (R, R = H, H (2), Me, Me (3), -(CH ₂ ) ₄ - (4)) and benzothiazol-2-amine (5) or gives the diaminocarbene species cis-[PdCl ₂ {C(N(H)Cy)N(H)4-R-thiazol-2-yl}(CNCy)] (15-19; 73-93%) for the reaction with 4-aryl-substituted thiazol-2-amines (R = Ph (6), 4-MeC ₆ H ₄ (7), 4-FC ₆ H ₄ (8), 4-ClC ₆ H ₄ (9), 3,4-F ₂ C ₆ H ₃ (10)). Inspection of the single-crystal X-ray diffraction data for 15-17 and 19 suggests that the structures of all these species exhibit previously unrecognized bifurcated chalcogen-hydrogen bonding μ _(S,N-H) Cl and also Pd ^II ···Pd ^II metallophilic interactions. These noncovalent interactions collectively connect two symmetrically located molecules of 15-17 and 19, resulting in their solid-state dimerization. The existence of the μ _(S,N-H) Cl system and its strength (6-9 kcal/mol) were additionally verified/estimated by a Hirshfeld surface analysis and DFT calculations combined with a topological analysis of the electron density distribution within the formalism of Bader's theory (AIM method) and NBO analysis. The observed noncovalent interactions are jointly responsible for the dimerization of 15-19 not only in the solid phase but also in CHCl ₃ solutions, as predicted theoretically by DFT calculations and confirmed experimentally by FTIR, HRESI-MS, ¹ H NMR, and diffusion coefficient NMR measurements. Available CCDC data were processed under the new moiety angle, and the observed μ _(S,E-H) Cl systems were classified accordingly to E (E = N, O, C) type atoms.