Organofluorine binding to sodium and thallium(I) in molecular fluoroalkoxide compounds

Abstract

The compounds (NaOR[sub f])[sub 4] (R[sub f] = CH(CF)[sub 3])[sub 2], Zr(OR[sub f])[sub 4] (2), Zr(OR[prime][sub f])[sub 4] (R[prime][sub f] = CMe(CF[sub 3])[sub 2]) (3), Na[sub 2]Zr(OR[sub f])[sub 6](C[sub 6]H[sub 6])[sub n] (4a when n = 1 and 4b when n = 2), and Tl[sub 2]Zr(OR[sub f])[sub 6] (5) have been synthesized and characterized by IR, multinuclear NMR, and mass spectrometry and (for 1, 3, 4a, b, and 5) X-ray diffraction structure determinations. The heavy fluorination of the molecular periphery makes all of these molecular compounds highly volatile. In addition, all X-ray structures (except that of 3) show evidence of intramolecular ([open quotes]secondary[close quotes]) bonding interactions between numerous organofluorines and the electrophiles sodium or thallium. The benzene in both solid compounds 4 forms a [pi]-complex to sodium. The absence of benzene in 5 leads to additional intermolecular Tl-F interactions. The reality of these electrophile-F interactions is further supported by the fact that [sup 205]Tl and [sup 19]F NMR studies show Tl-F coupling of a magnitude consistent with direct bonding. Moreover, variable-temperature [sup 205]Tl and [sup 19]F NMR studies reveal facile migration of both Tl electrophiles over the entire periphery of the Zr(OR[sub f])[sub 6] octahedron. Cleavage of C-F bonds ismore » evident in the electron impact mass spectra of these molecules, and especially from the fact that chemical vapor deposition of (NaOR[sub f])[sub 4] onto silica at 285 [degrees]C gives NaF, not Na[sub 2]O. These ground-state metal-organfluorine interactions appear to provide a facile reaction channel for rupture of the strong C-F bond. 58 refs., 8 figs., 8 tabs.« less