Ligand Design for Site-Selective Metal Coordination: Synthesis of Transition-Metal Complexes with η6-Coordination of the Central Ring of Anthracene

A polycyclic aromatic ligand for site-selective metal coordination was designed by using DFT calculations. The computational prediction was confirmed by experiments: 2,3,6,7-tetramethoxy-9,10-dimethylanthracene initially reacts with (C₅H₅)Ru(MeCN)₃]BF₄ to give the kinetic product with a (C₅H₅)Ru]⁺ fragment coordinated at the terminal ring, which is then transformed into the thermodynamic product with coordination through the central ring. These isomeric complexes have markedly different UV/Vis spectra, which was explained by analysis of the frontier orbitals. At the same time, the calculations suggest that electrostatic interactions are mainly responsible for the site selectivity of the coordination.