Structures and trends of neutral MXxsolvent4−x tetrahedra and anionic [MX4]2− tetrahalometallates of zinc(ii), cadmium(ii) and mercury(ii) with benzopyridine- and benzopyrazine-type N-donor ligands or cations

Abstract

Zinc, cadmium and mercury dihalides were reacted with benzopyridine- and benzopyrazine-type N-donor molecules acridine (acr), phenazine (phe), quinoline (quin) and quinoxaline (quinox) as ligands or cations. The solid-state structures of 16 novel, zero-dimensional reaction products were studied by X-ray diffraction. Seven of the compounds were prepared in the presence of an inorganic acid, HX, which resulted in the formation of anionic tetrahalometallates, [MX₄]²⁻, with either Cd²⁺ or Hg²⁺ as the cationic metal center and quinolinium (quin-H), quinoxalinium (quinox-H), acridinium (acr-H) or phenazinium (phe-H) as the counter cation. The other nine compounds contain Zn²⁺ as the tetrahedral cationic node. Five of the nine Zn²⁺ compounds are neutral, and four are ionic. Three of the four ionic Zn²⁺ compounds contain an anionic tetrahalometallate inorganic moiety, [ZnX₄]²⁻, while the inorganic component of the fourth ionic Zn²⁺ compound is coordinated by three halido ligands and one aqua ligand, [ZnX₃(H₂O)]⁻. Structural trends, hydrogen bonding interactions and aromatic interactions are identified. In addition, it is observed that in the case of the neutral phenazine or acridine compounds, the size of the organic molecule prevents coordination of the molecule to the metal ion.