Solid-State Packing of the Square-Planar [Rh^I(H₂bim)(CO)₂]₂[A] Complexes (H₂bim = 2,2-biimidazole; [A] = 2[Cl], 2[Rh^ICl₂(CO)₂], [Fe^IICl₄], [Co^IICl₄])

A series of ionic rhodium(I) complexes with the 2,2-biimidazole (H2bim) ligand were synthesized and characterized. The square-planar Rh(I) complexes were synthesized by reductive carbonylation of the RhCl3 in the presence of H2bim and a sacrificial metal surface (Fe or Co) in an autoclave (50 bar, 125 °C, 3–30 h). The solid-state structures of the complexes were determined by single-crystal X-ray diffraction. The basic backbone of all of the complexes was a 16-electron [RhI(H2bim)(CO)2]+ cation. The reaction conditions (reaction time, sacrificial metal surface) determined the counteranion. The cationic [RhI(H2bim)(CO)2]+ was obtained in crystalline form with four different anions: [Cl]−, [RhICl2(CO)2]−, [FeIICl4]2−, and [CoIICl4]2−. All of the complexes were crystallized as dinuclear [RhI(H2bim)(CO)2]22+ moieties in which the distances between the RhI centers were in the range of 3.28–3.38 Å. These dinuclear systems, held together by weak metal–metal interactions between two [RhI(H2bim)(CO)2]+ units, were connected to each other via weak interactions between the metal and the π system of the H2bim ligand of the neighboring molecule, or via the π interactions between aromatic ligands. The anion was found to have an essential impact on the crystal packing and separation of the metal centers in the complexes. The interactions between the nearest H2bim ligands in the crystal structure were also dependent on the nature and size of the counteranion and also on the interactions between the cation and the anion.