A facile route to hetero-bimetallic Ti(iv)-alkali metal calix[4]arene complexes

Abstract

Deprotonation of calix [4]arenes by alkali metal in methanol using simple benchtop procedures is effective in the formation of novel monomeric and dimeric titanium() complexes. For the larger alkali metal cations, K ϩ and Cs ϩ , favourable complexation within the π-basic calix[4]arene cavity facilitates the formation of monomeric titanium() complexes when oligomer formation is inhibited by an acetylacetonate ligand. In contrast, the smaller Li ϩ and Na ϩ ions preferentially form dimeric complexes with exo-bridging alkali and titanium() metal centres. A dimeric complex is also obtained for potassium in the absence of acetylacetonate. The solid state structures of the K-Ti and Na-Ti calix[4]arene dimer complexes show different structural characteristics depending on the nature of the alkali metal.

Calixarenes as platforms for the construction of multimetallic complexes

“…This is where the group 1 metalÁ Á Áp interactions occur. Results for the tantalum(V) studies highlight the comparatively weak binding of Li + and Na + ions within the cavity of the calix [4]arene, and explains why the titanium(IV) chemistry outlined above [9] does not extend to the use of sodium and lithium. Other examples of mixed transition-alkali metal calix[4]-arene complexes prepared under similar circumstances include those of tungsten with potassium [14], Fig.…”

“…A detailed study on the effect of these variables on mixed alkali-metal-titanium calixarene complexes has recently appeared [9]. Mono-calixarene K/Cs-Ti complexes, 1 and 2, Fig.…”

“…3. Molecular projection of Cs-Ti calix[4]arene complexÕ dotted lines represent CsÁ Á Á.p interactions[9].…”

Organometallic cavitands: Cation–π interactions and anion binding via π-metallation

“…A similar hetero bimetallic system investigated the influence of alkali metal on the coordination of calix [4]arenes with titanium(IV) [60,61]. By deprotonating the lower phenolic rim with potassium metal and introducing 1 equiv.…”

11 Titanium, zirconium and hafnium

“…57 Both monomeric and dimeric alkali-metal Ti(IV) calix [4]arene complexes have been synthesised. 58 ). The ion, described as a soluble metal-oxide analogue, has a giant ''tetrapod''-shaped molecule (inscribed to a sphere with a diameter of y32 A ˚), made up of four tri-Ti IV -1,2,3-substituted a-Dawson substructures, four Ti(OH) 3 bridging groups, and one encapsulated Cl 2 ion, overall having approximately T d symmetry, containing 16 edge-and/or corner-shared TiO 6 octahedra, a greater number of these octahedra than that found in other titanium(IV)-substituted polyoxotungstates.…”