Inorganic Chemistry, Vol.40, No.20, 5169-5176, 2001
Spectroscopic and structural studies on polyfluorophenyl tellurides and tellurium(IV) dihalides
Bis(fluorophenyl) tellurides R2Te (R = C6F2H3 (1), CF3C6F4 (2), CF3C6F4OC6F4 (3), and C6F5 (4)) are synthesized by the facile reaction of Na2Te with bromo-fluorobenzenes, RBr. The corresponding bis(fluorophenyl)tellurium(IV) dihalides. R(2)TeHal(2) (Hal = F, Cl, and Br) (5-16), are obtained by the oxidation 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), and Br (13)) and R2TeCl2 (R = C6F2H3 (9), CF3C6F4 (10), CF3C6F4OC6F4 (11), and C6F5 (12)), the coalescence temperatures, T-c, and free enthalpies, DeltaG(double dagger). of rotation of the TeC bonds are determined, The activation enthalpies for the dichlorides/dibromide 9-13 are in the range of 14.4-15.2 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 shorter than the sum of the van der Waals radii, leading to different networks of association.