title: On the interaction of acetone with electrophilic metallocavitands having extended cavities.
abstract: We report the synthesis and characterization of tantalum-boronate trimetallic clusters of  general formula {[Cp*Ta](3)(μ(2)-RB(O)(2))(3)(μ(2)-OH)(μ(2)-O)(2)(μ(3)-OH)} (R= 4-(C(6)H(5))(C(6)H(4)) (Ta(3)-4Ph), 4-(C(6)H(5)O)(C(6)H(4)) (Ta(3)-4OPh), 4-(C(7)H(7)O)(C(6)H(4)) (Ta(3)-4OBn), 4-(C(8)H(5))(C(6)H(4)) (Ta(3)-4PhEt), and 4-(C(12)H(7))(C(6)H(4)) (Ta(3)-4Napht)). All complexes have been characterized by NMR spectroscopy and X-ray diffraction. The trimetallic species feature a large Lewis acid type cavity allowing for substrate binding in both the solid and the liquid state using a unique electrostatic interaction and a hydrogen bond.  ΔH° and ΔS° values for  association of acetone with the complexes vary between -2.0 and -4.1 kcal·mol(-1) and -3 and 2 cal·mol(-1)·K(-1), respectively, showing weaker binding than smaller cavitands of the same type. The barrier for  acetone exchange at equilibrium is similar for all complexes, and  ΔH(‡) values vary between 8.2 and 11.4 kcal·mol(-1).
authors.affiliation: Département de Chimie, Université Laval, 1045 Avenue de la Médecine, Québec, Québec, Canada, G1 V 0A6.
authors.forename: Christian N
authors.initials: CN
authors.lastname: Garon
authors.forename: Maxime
authors.initials: M
authors.lastname: Daigle
authors.forename: Isabelle
authors.initials: I
authors.lastname: Levesque
authors.forename: Philippe
authors.initials: P
authors.lastname: Dufour
authors.forename: Hassan
authors.initials: H
authors.lastname: Iden
authors.forename: Christian
authors.initials: C
authors.lastname: Tessier
authors.forename: Thierry
authors.initials: T
authors.lastname: Maris
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Morin
authors.forename: Frédéric-Georges
authors.initials: FG
authors.lastname: Fontaine