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

Abstract

We report the synthesis and characterization of tantalum-boronate trimetallic clusters of the general formula {[Cp*Ta](3)(mu(2)-RB(O)(2))(3)(mu(2)-OH)(mu(2)-O)(2)(mu(3)-OH)} (R = i-Bu (Ta(3)-iBu), C(6)H(5) (Ta(3)-Ph), 2,5-(CH(3))(2)(C(6)H(3)) (Ta(3)-2,5Me), 3,5-(CH(3))(2)(C(6)H(3)) (Ta(3)-3,5Me), and 3,5-(CF(3))(2)(C(6)H(3)) (Ta(3)-3,5CF(3))). Three of these complexes feature a 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. We also report the synthesis of {[Cp*Ta](2)(mu(2)-MesB(O)(2))(2)[MesB(OH)(O)](2)(mu(2)-OH)(2)} (Mes = 2,4,6-(CH(3))(3)C(6)H(2) (Ta(2)-Mes)). All complexes have been characterized by NMR and X-ray diffraction studies, and the steric and electronic effects on the boronate ligands have been investigated. The physical properties of the interaction between the tantalum-boronate clusters and tetrahydrofuran and acetone have been studied by thermogravimetric analysis, FT-IR, and Density Functional Theory calculations to characterize the molecular interactions in the resulting adducts.

Phosphate‐Triggered Self‐Assembly of N‐[(Uracil‐5‐yl)methyl]urea: A Minimalistic Urea‐Derived Hydrogelator

“…To date, only a single other example of a monometallic transition‐metal boronate complex can be found in the Cambridge Structural Database;37 this consists of a platinum(II) boronate complex 38. We note that polymetallic tantalum,39 copper40 and zirconium41 boronato complexes have also been characterised by X‐ray diffraction. Platinum(II) complexes with chelating dehydro(arylboronic anhydride) ligands have also been reported 42.…”

Cavitands Incorporating a Lewis Acid Dinickel Chelate Function as Receptors for Halide Anions

“…One very successful approach to bind halide anions is chelation by Lewis acids, and several examples of multidentate Lewis-acids incorporating d-block and p-block metals have now been reported . Of these, the cascade complexes with closed-shell structures have received much attention. − The analogous chemistry of metallocavitands featuring an open binding site has been investigated far less frequently. − …”

Synthesis of tetrathiafulvalene-containing zirconium(IV) pincers and metallocavitands for hosting fullerenes

“…These structures may find use in a large array of applications as chemical sensors, nanoscale reaction vessels [22,23], containers for drug delivery [24,25], molecular switches [26][27][28][29] and memory storage devices [30]. Our research group has developed in the past few years an aggregation approach to access trimetallic conical structures with tantalum [31][32][33].…”

“…These metallocavitands can be prepared in good to excellent yield via the one-step reaction of Cp*TaMe4 with aryl boronic acids [33]. Example of a tantalum metallocavitand obtained by X-ray crystallography [32].…”

“…The cavity can be easily expanded to reach an upper rim area of 175 Å 2 by the introduction of spacers on the aryl boronate moiety [31]. The tantalum metallocavitands have demonstrated hosting capabilities for Lewis bases such as acetone and tetrahydrofuran via hydrogen bonding and electrostatic interactions [32]. Owing to their hosting properties, high yielding synthesis and ease of manipulation, we wanted to expand this concept to the capture of fullerenes, namely C60 and C70.…”