The Crystal structures of tetra-n-Butylammonium salts of GaCl4 −, GaBr4 − and GaI4 −

Tetra-n-butylammonium salts of Ga, Ga and have been prepared from stoichiometric amounts of GaX3 and Bu4NX in methanol. Their crystal structures have been determined by single crystal X-ray diffraction. The Bu4N[GaCl4] and Bu4N[GaBr4] salts crystallize in the orthorhombic system, space group Pnna, whereas the Bu4N[GaI4] salt crystallizes in the monoclinic system, space group P21/n. For all compounds there are four molecules per unit cell. The structures consist of distorted tetrahedral ions and Bu4N+ cations. In the tetrahedral Ga and Ga anions there are two pairs of Ga–X distances: 2.163(2), 2.174(2) Å and 2.297(2), 2.316(3) Å, respectively. In the ion there are four Ga–I distances: 2.537(2), 2.539(2), 2.549(2) and 2.554(2) Å. The results show that the significantly greater increase in Ga–X distance on passing from Br to I than from Cl to Br results in lower symmetry and is accompanied by greater distortion of the tetrahedron.