Synthesis and crystal chemistry of octahedral rhodium(III) chloroamines

Rhodium(III) octahedral complexes with amine and chloride ligands are the most common starting compounds for preparing catalytically active rhodium(I) and rhodium(III) species. Despite intensive study during the last 100 years, synthesis and crystal structures of rhodium(III) complexes were described only briefly. Some [RhCl_x(NH₃)_6-x] compounds are still unknown. In this study, available information about synthetic protocols and the crystal structures of possible [RhCl_x(NH₃)_6−x] octahedral species are summarized and critically analyzed. Unknown crystal structures of (NH₄)₂[Rh(NH₃)Cl₅], trans–[Rh(NH₃)₄Cl₂]Cl·H₂O, and cis–[Rh(NH₃)₄Cl₂]Cl are reported based on high quality single crystal X-ray diffraction data. The crystal structure of [Rh(NH₃)₅Cl]Cl₂ was redetermined. All available crystal structures with octahedral complexes [RhCl_x(NH₃)_6-x] were analyzed in terms of their packings and pseudo-translational sublattices. Pseudo-translation lattices suggest face-centered cubic and hexagonal closed-packed sub-cells, where Rh atoms occupy nearly ideal lattices.