Conformational properties of substituted ferrocenes: Experimental and theoretical studies of the molecular structures of 1,1 '-di-tert-butylferrocene and isopropylferrocene

The molecular structures of 1,1'-di-tert-butylferrocene (1) and isopropylferrocene (2) have been examined by solid-state X-ray crystallography, gas-phase electron diffraction, and DFT and molecular mechanics calculations. Whereas the solid-state structure of 1 has crystallographically imposed staggered C-2h symmetry, electron diffraction and calculations support a mixture of C-2 eclipsed isomers. The eclipsed ring-ring and the:ring-isopropyl conformations found for 2 are essentially identical in the solid and gas phase and are supported by calculations. The molecular mechanics analysis may be extended to other alkylferrocene derivatives.