Measurements of Structural and Quadrupolar Coupling Parameters for Chloroferrocene Using Microwave Spectroscopy

Rotational spectra for two isotopomers of chloroferrocene were measured using pulsed-beam Fourier transform microwave spectroscopy. Transitions were observed for ³⁵Cl and ³⁷Cl isotopomers in the 4-10 GHz range. Chlorine quadrupole coupling strengths and rotational constants were obtained from the data. The rotational constants and quadrupole coupling strengths for ³⁵Cl are A = 1370.009(8) MHz, B = 767.342(1) MHz, C = 634.8834(6) MHz, eQq_aa = -9.06(4) MHz, and eQq_bb = -28.43(6) MHz and for ³⁷Cl are A = 1362.23(2) MHz, B = 751.623(2) MHz, C = 622.324(1) MHz, eQq_aa = -8.78(18) MHz, and eQq_bb, = -20.76(9) MHz. These measured rotational constants were used to determine the following structural parameters of chloroferrocene: r(Fe-(C₅H₅)) = 1.594(20) Å, r(Fe-(C₅H₄Cl)) = 1.699(13) Å, r(C-C) = 1.7204(9) Å, and r(C-C) = 1.4329(7) Å. No evidence for internal rotation was observed in the microwave spectrum.