Synthesis and Characterization of Tantalum(V) Boronate Clusters: Multifunctional Lewis Acid Cages for Binding Guests

Structural Study of Acidic Metallocavitands and Characterization of their Interactions with Lewis Bases

“…The elemental analyses were performed at the Laboratoire d'analyse élémentaire de l'Université de Montréal. Cp*TaMe4, 29 Ta3-Ph, and Ta3-iBu, 16 were prepared according to literature procedures. The boronic acids were purchased from Aldrich, Alfa…”

“…of water yielded complexes Ta3-Ph and Ta3-iBu, respectively. 16 While both complexes exhibit a typical Ta3O4 core observed in various occasions, 17 only the aryl substituted complex is a metallocavitand, since folding of one alkyl chain in Ta3-iBu fills the void made by the boronate coordination. In order to evaluate the level of freedom available with the steric bulk of substituents on the arylboronic acid, we carried out the synthesis of analogues using boronic acids displaying an increasing amount of steric bulk at the ortho and meta positions since the para position should be easy to modulate without affecting the structure of the cavity.…”

“…We recently reported the facile one-step synthesis of a new metallocavitand interacting strongly with Lewis bases, {[Cp*Ta]3( 2 -PhB(O)2)3( 2 -O)2( 2 -OH)( 3 -OH)} (Ta3-Ph), from Cp*TaMe4 and phenylboronic acid. 16 This new species exhibits interesting features, including a conic cavity somewhat similar to calix[4]arenes, with a pseudo-C3 symmetry. Even more unique is the presence of four acidic sites at the bottom of the cavity that can, in principle, interact with Lewis bases such as ketones.…”