ORGANOFLUORINE BINDING TO SODIUM AND THALLIUM(I) IN MOLECULAR FLUOROALKOXIDE COMPOUNDS

The compounds (NaOR(f))4 (R(f) = CH(CF)3)2), Zr(OR(f))4 (2), Zr(OR(f'))4 (R(f)' = CMe(CF3)2) (3), Na2Zr-(OR(f))6(C6H6)n (4a when n = 1 and 4b when n = 2), and Tl2Zr(OR(f))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 (''secondary'') 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 Tl-205 and F-19 NMR spectra show Tl-F coupling of a magnitude consistent with direct bonding. Moreover, variable-temperature Tl-205 and F-19 NMR studies reveal facile migration of both Tl electrophiles over the entire periphery of the Zr(OR(f))6 octahedron. Cleavage of C-F bonds is evident in the electron impact mass spectra of these molecules, and especially from the fact that chemical vapor deposition of (NaOR(f))4 onto silica at 285-degrees-C gives NaF, not Na2O. These ground-state metal-organofluorine interactions appear to provide a facile reaction channel for rupture of the strong C-F bond.