Controlling the Orientation of Sequential Ligands in the Self-Assembly of Binuclear Coordination Compounds

Abstract

The sequential ligand 5-H3, which contains one catechol and one aminophenol unit, was prepared in a four-step sequence. The two electronically different binding sites of 5 are able to control the metal-directed self-assembly of binuclear coordination compounds with different ligand orientations. In coordination studies with titanium(IV) or gallium(III) ions, this ligand 5 was used to obtain anionic homobinuclear complexes [(5)3Ti2]- and [(5)3Ga2]3- with two ligands orientated in one and the third in the opposite direction (type II structure). On the other hand, if the ligand 5 reacts with a 1:1 mixture of titanium(IV) and gallium(III) ions exclusively, the heterobimetallic complex [(5)3GaTi]2- is formed in a cooperative process. In this coordination compound the three ligands are orientated in one direction (type I structure). For K2[(5)3GaTi]·6DMF·ether, space group P21/c, a = 12.868(3) A, b = 19.902(2) A, c = 27.063(2) A, β = 102.22(1)°, V = 6774(2) A3, Z = 4, and R = 0.071. The structural analysis show...