ACTIVATION OF C-H BONDS: PURE ROTATIONAL SPECTROSCOPY OF HZnCH$_3$ (\ {X} $^{1}A_1$)

Author Institution: Department of Chemistry, Department of Astronomy, Steward Observatory, University of Arizona, Tucson, AZ 85721The pure rotational spectrum of HZnCH$_3$ has been observed in its ground electronic state (\ {X} $^{1}A_1$) using both direct absorption and Fourier transform microwave techniques in the frequency range 18-516 GHz. Twelve rotational transitions of this symmetric top species were recorded in K-ladders up to K = 7. The molecule was synthesized from Zn(CH$_3$)$_2$ in an AC discharge and also from Zn (vapor) + CH$_4$ with a DC discharge. From measurements of the spectra of various isotopic species ($^{66}$Zn, $^{67}$Zn, $^{68}$Zn, $^{13}$C, and $^2$H), an accurate structure has been determined. The H-C-H bond angle was found to be $108.7^{irc}$, slightly smaller than that in ZnCH$_3$ or CH$_4$. In addition, nuclear spin-rotation (I $^.$ J) interactions with the methyl hydrogen nuclei and electric quadrupole coupling from the $^{67}$Zn nucleus were resolved in the FTMW spectrum. From these data, hyperfine parameters have been established. The value of eqQ = -109.125(11) MHz indicates that the bonds to zinc are primarily covalent. Detection of this species, especially via the Zn + CH$_4$ pathway, is a good indication of the ability of metal atoms to insert into C-H bonds