We report the first full geometry optimizations of the Creutz–Taube ion at the MP2 and gradient-corrected DFT levels of theory (B3LYP). The MP2-optimized geometry matches the experimentally observed structures much more closely than that obtained at the DFT level. DFT Ru–N bond distances are uniformly 0.04–0.18Å too long, while MP2 calculations yield Ru–N distances within 0.01–0.05Å. We attribute this difference to the enhanced ionic character of the Ru–N bond in the MP2 calculations. For [Ru(NH 3 ) 6 ] 2+ , we have shown that charge distributions calculated at higher levels of theory (MP3, MP4 and QCISD) are consistent with the MP2 results but are significantly different than those obtained at the DFT level (B3LYP, BLYP, BPW91, G96LYP and G96PW91).