WEAKLY COORDINATING ANIONS
Our fluorine chemistry research has also contributed to the chemistry and bonding of groups having electronegativities approaching that of fluorine such as the OIOF4- and F5TeO-groups. The OIOF4- and F5TeO- groups have been shown to be among the most electronegative groups known. Examples of noble-gas derivatives of both ligand groups have been synthesized and characterized. Contributions to the F5TeO-derivative chemistry of other main-group and transition metal elements have also been made. Particularly noteworthy examples are the syntheses of the weakly coordinating and oxidatively resistant pnicogen anion series, M(OTeF5)6-; (M = As, Sb, Bi). They have been exploited to stabilize the novel SbBr4+ cation as well as the AsBr4+ cation and have been used by other workers to stabilize cation-solvent interactions in the solid state. A dramatic illustration of the utility of these anions is the recent syntheses and structural characterizations of room-temperature stable carbocations derived from CFCs (chlorofluorocarbons) and other tetrahalomethanes by oxidation of a halogen ligand (other than fluorine) with XeOTeF5+Sb(OTeF5)6-. The stable carbocations CFCl2+, CFClOTeF5+, CCl3+, CFBr2+, CBr3+, CBr(OTeF5)2+ and C(OTeF5)3+ have thus far been obtained as Sb(OTeF5)6-; salts and characterized by X-ray crystal structure determinations and/or spectroscopically. The CCl3+, CBr3+ and C(OTeF5)3+ salts are stable at room temperature.