Halogen-Bonded Assemblies in Half-Sandwich Noble Metal Complexes with Bis(4-iodopyrazol-1-yl)methane: Structural and Computational Analyses

Four half-sandwich noble metal complexes containing bis(4-iodopyrazol-1-yl)methane ligand (bpmI), [M(p-cym)(bpmI)Cl]Cl (M = Ru2+ and Os2+), and [M(bpmI)(Cp*)Cl]Cl (M = Rh3+ and Ir3+) were synthesized and characterized by single-crystal X-ray diffraction analysis. C–I···Cl halogen bonds between the iodine atoms of the bis(4-iodopyrazol-1-yl)methane and the Cl– anions were found to be the structure-defining contacts for all complexes. Bis(4-iodopyrazol-1-yl)methane acts as both the bidentate ligand and 180°-orienting halogen bond donor in these half-sandwich complexes, which further assemble into halogen-bonded polymeric chains. The existence and noncovalent nature of these interactions were confirmed by the topological analysis of the electron density distribution with the help of the atoms in molecules (AIM) approach, followed by noncovalent interactions analysis of the reduced density gradient (RDG). The influence of the nature of the metal center and the presence of solvate molecules on the halogen bond strength was analyzed.