meso-helicate-type dinucleartitanium(IV) complexes Mn[(ligand)3Ti2] (n = 4: M = Li, Na, K, Cs; n = 2: M = Ca, Sr), which are formed by metal-directed self-assembly of alkyl-bridged bis(catecholate) ligands in the presence of basic alkali-metal or alkaline-earth metal salts, can be monitored by dynamic NMR spectroscopy. The free-energy barrier (ΔG‡) of this process is influenced by the nature of the ligand, the
A controlling influence on the self-assembly in the complexation reaction of a mixture of methylene- and ethylene-bridged bis(catechol) ligands (1-H4 and 2-H4 , respectively) with titanium(IV) ions is exerted by alkali metal cations (see scheme). Thus, not a complicated mixture of complexes, but as a result of a self-recognition of the ligands only well-defined products are formed.