Antonella J. Petrella

A heterobimetallic K2Ti2 complex incorporating two calix[5]arenes: A diverse array of metal–ligand interplay

Reaction of p-tBu-calix[5]arene with potassium metal in a mixture of methanol and THF followed by [Ti(acac)2(OPri)2] affords an unsymmetrical dimeric 1∶1 K/Ti complex built up from a central Ti–O–Ti core with each titanium(IV) centre octahedrally coordinated, bearing an acac and a calix[5]arene encapsulating a potassium ion.

Selective 1,3-complexation of p-tBu-calix[4]arene by [TiCp2Me2]

Reaction of p-tBu-calix[4]arene with dimethyl titanocene results in high yield selective 1,3-dimetallation of the calixarene in the cone conformation by selective cleavage of one methyl group.

2 ∶ 1 Ba/Ti(IV) Heterobimetallic complex based on two calix[6]arenes

Reaction of p-Bu(t)-calix[6]arene with barium metal in methanol then [Ti(OPr(i))4] affords a heterobimetallic complex with a central Ti(IV) attached to two calix[6]arenes in the 1,3-alternate conformation, each with an endo-barium sharing common phenolate groups with the titanium centre.

Titanocene dichloride route to a tetranuclear oxo-bridged monocyclopentadienyl titanium(IV) calix[4]arene complex.

Lithiation of p-tBu-calix[4]arene followed by reaction with titanocene dichloride affords a novel tetranuclear titanium(IV) monocyclopentadienyl complex, wherein a single calix[4]arene in a cone conformation provides O-phenoxy coordination to four titanium atoms, with additional mu-oxo bridging between titanium centres in an eight membered ring.

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

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(IV) complexes. For the larger alkali metal cations, K+ and Cs+, favourable complexation within the π-basic calix[4]arene cavity facilitates the formation of monomeric titanium(IV) complexes when oligomer formation is inhibited by an acetylacetonate ligand. In contrast, the smaller Li+ and Na+ ions preferentially form dimeric complexes with exo-bridging alkali and titanium(IV) 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.