Vers le développement de matériaux à transition de spin : synthèse de différents complexes mono-oxo de rhénium (V) et étude de leur écart HOMO-LUMO

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Structural study of acidic metallocavitands and characterization of their interactions with Lewis bases

We report the synthesis and characterization of tantalum−boronate trimetallic clusters of the general formula {[Cp*Ta]3(μ2-RB(O)2)3(μ2-OH)(μ2-O)2(μ3-OH)} (R = i-Bu (Ta3-iBu), C6H5 (Ta3-Ph), 2,5-(CH3)2(C6H3) (Ta3-2,5Me), 3,5-(CH3)2(C6H3) (Ta3-3,5Me), and 3,5-(CF3)2(C6H3) (Ta3-3,5CF3)). 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(μ2-MesB(O)2)2[MesB(OH)(O)]2(μ2-OH)2} (Mes = 2,4,6-(CH3)3C6H2 (Ta2-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

Coordination of a bifunctional ligand to a rhodium(III) dimethyl complex : Lewis acidity enhancement by chelation

The addition of the ambiphilic compound (Me2PCH2AlMe2)2 (1) to Cp*RhMe2(DMSO) (DMSO ) dimethylsulfoxide) (2) gives Cp*RhMe2(PMe2CH2AlMe2‚DMSO) (3‚DMSO). The addition of Lewis acids (LA) such as La(dbm)3 (dbm ) dibenzoylmethane) and AlMe3 to a solution of complex 3‚DMSO gives a competition reaction that results in the formation of LA‚DMSO and Cp*RhMe2(PMe2CH2AlMe2) (3). When heated to 40 °C, complex 3 ionizes to a putative zwitterionic species, Cp*Rh+Me(PMe2CH2AlMe3 -) (3′), which is converted to [Cp*Rh(Me)(µ2 -η2 -Me2PCH2)]2 (4) irreversibly. Spin saturation transfer experiments demonstrated that the rate of the methyl abstraction by the alane moiety was 0.76 ( 0.09 s-1 , while the rate of abstraction of the methyl in Cp*RhMe2(PMe3) by AlMe3 was 0.10 ( 0.02 s-1 . The zwitterionic species 3′ could be trapped in solution by addition of PMe3 to afford both Cp*Rh+Me(PMe3)(Me2- PCH2AlMe3 -) (5) and [Cp*Rh+Me(PMe3)(Me2PCH2AlMe2)]AlMe4 - (6). When compound 1 was added to complex 3′, the formation of the zwitterionic complex Cp*Rh+Me(η2 -Me2PCH2Al-Me2CH2PMe2) (7) was observed

Synthesis and characterization of tantalum(V) boronate clusters : multifunctional Lewis acid cages for binding guests

Open and shut cases: Tantalum(V) boronate clusters [(Cp*Ta)3(μ2‐η2‐RBO2)3(μ2‐O)2(μ2‐OH)(μ3‐OH)] (Cp*=η5‐C5Me5; 1: R=Ph, 2: R=iBu) with Lewis acidic cavities were prepared. Whereas the cavity of 2 is blocked by the iBu groups, that of 1 is open and can bind Lewis basic guests such as ketones (see picture) by interaction with one boronate and one μ3‐OH ligand

27e Colloque annuel de l'AQPC

Titre de l'`écran-titre (visionné le 26 sept. 2008)