Synthesis and Reactivity of Cationic Group 4 Tropocoronand Complexes

Abstract

The tropocoronand complexes [M(TC-3,3)(CH2Ph)2] (M = Zr, Hf) react with either oxidants or protic reagents to afford the five-coordinate cations [M(TC-3,3)(CH2Ph)]+, in which the benzyl ligand interacts weakly in an η2 manner with the group 4 metal center. Isocyanides react with the resulting cations to afford ketenimine complexes, whereas benzophenone inserts into the M−C bond to yield [M(TC-3,3){η1-OCPh2(CH2Ph)}]+. These properties reflect the greater electron-releasing character of the tropocoronand ligands compared to cationic zirconium complexes of other tetraaza macrocyclic ligands and to zirconocenes.