Substitution and Isomerization of Asymmetric β-Diketonato Rhodium(I) Complexes: A Crystallographic and Computational Study

Ligand substitution of PPh3 for CO in the asymmetric square-planar β-diketonato complex [Rh(PhCOCHCOCH2CH3)(CO)2] leads to formation of the monosubstituted [Rh(PhCOCHCOCH2CH3)(CO)(PPh3)] product. Two geometrical product isomers are possible, which unexpectedly crystallize in the same crystal lattice. DFT calculations of the substitution reaction support a two-step mechanism, involving temporary dissociation of a β-diketonato ligand and formation of a square-planar intermediate. Analysis of the mechanisms involved in product isomerization suggests several noncatalyzed and solvent-assisted interconversion pathways.