Hierarchical, Lithium‐Templated Assembly of Helicate‐Type Complexes: How Versatile Is This Reaction?

Catechol ligands that bear carbonyl functions such as esters or aldehydes in the 3‐position ( 1a – c ‐H 2 ) form triple‐stranded, helicate‐type complexes [Li 3 ( 1a – c ) 6 Ti 2 ] – with titanium(IV) and the corresponding double‐stranded compounds [Li 2 ( 1a – c ) 4 B 2 ] with boron(III) in hierarchical, lithium‐templatedprocesses. The related 8‐hydroxyquinoline ligands 2a , b ‐H can be used for the formation of similar complexes[Li 3 ( 2a , b ) 6 M 2 ] + with cobalt(II), nickel(II), or zinc(II). A prerequisite for the formation of the lithium‐bridged dimers is a negative charge of the mononuclear complexes, which are able to electrostatically attract the lithium cations and thus compensate the repulsion between the cations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)