Abstract
Crystal structures of GaX3 (X = Cl (I), Br (II), and I (III)) and AlI3 (IV) were determined at low temperature by single crystal X-ray crystallography. I is monoclinic, space group C2/m with a = 11.948(4), b = 6.855(3), c = 7.050(3) Å, β = 125.69(3)°, Z = 4, R1 = 0.038. II–IV are isotypic to each other: II is monoclinic, space group P21/c with a = 8.874(4), b = 5.637(2), c = 11.006(4) Å, β = 107.81(4)°, Z = 4, R1 = 0.056; III: a = 9.584(3), b = 6.084(2), c = 11.839(4) Å, β = 107.78(3)°, R1 = 0.044; IV: a = 9.591(3), b = 6.069(2), c = 11.902(3) Å, β = 108.05(3)°, R1 = 0.046. The crystal structures I–IV are built of dimeric M2X6 molecules consisting of two MX4 tetrahedra sharing a common XX edge with shorter M-X (terminal) and longer M-X(bridging) distances. The structure of I can not be described in terms of the closest Cl packing, whereas the structures of II–IV are based on slightly distorted cubic closest packing of halogen atoms, which accounts for their strong tendency to twinning.
© 2004 Oldenbourg Wissenschaftsverlag GmbH