The gas phase structure of ethynylferrocene using microwave spectroscopy

Area of Science:

• Organometallic Chemistry
• Molecular Spectroscopy
• Physical Chemistry

Background:

• Ferrocene derivatives are crucial in organometallic chemistry.
• Understanding their precise molecular structure is key to predicting reactivity and properties.
• Microwave spectroscopy offers high-resolution gas-phase structural data.

Purpose of the Study:

• To determine the precise gas-phase structural parameters of ethynylferrocene.
• To investigate the conformation of the cyclopentadienyl rings.
• To compare experimental data with theoretical calculations.

Main Methods:

• Microwave spectroscopy was employed to measure rotational transitions.
• A rigid rotor Hamiltonian with centrifugal distortion constants was used for analysis.
• Isotopomer analysis and Kraitchman methods determined structural parameters and atomic coordinates.

Main Results:

• The gas-phase structure of ethynylferrocene was determined, with Fe-C1 distance at 2.049(5) Å and C-C bond at 1.432(2) Å.
• The ethynyl group exhibits a bend of 2.75(6)° away from the iron atom.
• Analysis confirmed an eclipsed conformation of the cyclopentadienyl rings in the ground vibrational state.

Conclusions:

• The study provides accurate gas-phase structural data for ethynylferrocene.
• The results offer insights into the electronic and steric effects within substituted ferrocenes.
• A reference gas-phase Fe-centroid distance for ferrocene was estimated at 1.65(1) Å.