MEASUREMENTS OF STRUCTURAL AND QUADRUPOLAR COUPLING PARAMETERS FOR 1-CHLOROFERROCENE USING MICROWAVE SPECTROSCOPY

Author Institution: Department of Chemistry, University of ArizonaRotational spectra for two isotopomers of monochloroferrocene were measured using pulsed beam Fourier transform microwave spectroscopy. This was the first structural study for 1-Chloroferrocene and the first structural study of any substituted ferrocene in the gas phase. Transitions were observed for $^{35}Cl$ and $^{37}Cl$ isotopomers in the 4-10 GHz range. Chlorine quadrupole coupling strengths and rotational constants were obtained from the data. For $^{35}Cl$ the rotational constants and quadrupole coupling strengths are A=1370.009(8) MHz, B=767.342(1) MHz, C=634.8834(6) MHz, $eQq_{aa}=-9.06(4)$ MHz, $eQq_{bb}=-28.43(6)$ MHz, and for $^{37}Cl$, A = 1362.23(2) MHz, B=751.623(2)MHz and C=622.324(1)MHz, $eQq_{aa}=-8.78(17)$ MHz and $eQq_{bb}=^{-}20.79(9)$ MHz. These measured rotational constants were used to determine the following structural parameters of 1-chloroferrocene: $r(Fe-(C_{5}H_{5}) = 1.594(20)$ {\AA}, $r(Fe-(C_{5}H_{4}cl)) = 1,699(13)$ {\AA}, $r(C-Cl) =1,7204(9)$ {\AA} and $r(C-C) = 1,4329(7)$ {\AA}. These results support a trend of increasing $^{5}\eta$-Fe-Cp bond length upon electronegative substitution of the ring. No evidence for internal rotation was observed in the microwave spectrum