Structural and conformational investigations of chiral bis(phenylamido)ferrocenes by X-ray crystallography and density functional calculations

X-ray crystallographic structures of the synthesized bis(phenylamido)ferrocene, compound 1, were determined in two forms: cis-conformer (1a) and trans-conformer (1b). Structures 1a and 1b possessed their enantiomeric pairs 1a′ and 1b′, respectively in the crystal structures. B3LYP/LanL2DZ-optimized structures of all conformers of 1 were obtained as Z1, Z2 and E2 and their corresponding enantiomers Z4, Z3 and E2′. Conformers Z1 and E2 are found to be the most stable conformers. The structures of enantiomeric pairs Z1/Z4 and E2/E2′ are in good agreement with crystal structures of 1a/1a′ and 1b/1b′, respectively. Their relative energies are in order Z1 (Z4) < Z2 (Z3) < E2 (E2′). Their interconversion equilibria Z1 ↔ Z2, Z2 ↔ E2 and Z2 ↔ Z3 were found and their reaction energies, thermodynamic quantities, rate, and equilibrium constants were obtained. DFT calculations suggested that different conformations of bis(phenylamido)ferrocene could be ascribed to both thermodynamic and kinetic factors.