| Abstract: | Crystal Structure and Phase Transitions of As(CH3)4I The crystal structure of α-As(CH3)4I at room temperature was determined using single crystal data: cubic, space group Pa3 , a = 1 198.0(2) pm. Therefore α-As(CH3)4I displays a novel crystal structure, which is not comparable to known AB-Typ structures with respect to the arrangement of anions and the baricenters of the complex cations. Differential thermal analysis showed three phase transitions at 103, 175 and 215°C. The lattice parameters of the high temperature phases (temperature dependent Guinier measurements) are: β-As(CH3)4I (tetragonal): a = 845.2(2) pm, c = 615.0(2) pm; γ-As(CH3)4I (hexagonal): a = 737.7(2) pm, c = 1 082.2(3) pm; and to δ-As(CH3)4I (hexagonal): a = 705.8(2) pm, c = 1 147(1) pm. β-and γ-As(CH3)]4I are isotypic to N(CH3)4Cl and As(CH3)4Br, respectively. |
