Synthesis, Electronic Structure, and Reactivity Studies of a 4-Coordinate Square Planar Germanium(Ⅳ) Cation

摘要

A tetra-coordinate, square planar germanium- (Ⅳ) cation [(TPFC)Ge]~+ (TPFC = tris(pentafluorophenyl)- corrole) was synthesized quantitatively by the reaction of (TPFC)Ge-H with [Ph_3C]~+[B(C_6F_5)_4]~-. The highly reactive [(TPFC)Ge]~+ cation reacted with benzene to form phenyl complex (TPFC)Ge-C_6H_5 through an electrophilic pathway. The key intermediate, a σ-type germylium-benzene adduct, [(TPFC)Ge(η~1-C_6H_6)]~+, was isolated and characterized by single-crystal X-ray diffraction. Deprotonation of [(TPFC)Ge- (η~1-C_6H_6)]~+ cation led to the formation of (TPFC)Ge-C_6H_5. [(TPFC)Ge]~+ also reacted with ethylene and cyclopropane in benzene at room temperature to form (TPFC)Ge-CH_2CH_2C_6H_5 and (TPFC)Ge-CH_2CH_2CH_2C_6H_5, respectively. The observed electrophilic reactivity is ascribed to the highly exposed cationic germanium center with novel frontier orbitals comprising two vacant sp-hybridized orbitals that are not conjugated to π-system. The three electron-withdrawing pentafluorophenyl groups on the corrole ligand also enhance the electrophilicity of the cationic germanium corrole.