Spectroscopic and structural studies on polyfluorophenyl tellurides and tellurium(IV) dihalides

Bis(fluorophenyl) tellurides R2Te (R = C6F2H3 (1), CF3C6F4 (2), CF3C6F4OC6F 4 (3), and C6F5 (4)) are synthesized by the facile reaction of Na2Te with b romo-fluorobenzenes, RBr. The corresponding bis(fluorophenyl)tellurium(IV) dihalides. R(2)TeHal(2) (Hal = F, Cl, and Br) (5-16), are obtained by the o xidation of 1-4 with mild halogenating agents (XeF2, SO2O2, and Br-2). The dihalides show temperature-dependent NMR spectra. On the basis of the F-19 NMR spectra of the two series, (C6F2H3)(2)TeHal(2) (Hal = F (5), CI (9), an d Br (13)) and R2TeCl2 (R = C6F2H3 (9), CF3C6F4 (10), CF3C6F4OC6F4 (11), an d C6F5 (12)), the coalescence temperatures, T-c, and free enthalpies, Delta G(double dagger). of rotation of the TeC bonds are determined, The activati on enthalpies for the dichlorides/dibromide 9-13 are in the range of 14.4-1 5.2 kcal mol(-1) and that for the difluoride 5 is considerably lower at 10. 7 kcal mol(-1). In addition to thorough spectroscopic characterization of 1 -16, the crystal structures of the monotellurides 2 and 4 as well as of the tellurium(IV) dihalides 5, 6, 9, 10, and 13 were determined. The dihalides show interesting intermolecular Te . . . Hal contacts, significantly short er than the sum of the van der Waals radii, leading to different networks o f association.