Preparation of trimeric and tetrameric bis(trifluoromethyl)arsazene; X-ray study of [(CF3)2AsN]4

Abstract

Two new aminoarsines, (CF₃)₂AsN(SiMe₃)₂(1) and CF₃As[N(SiMe₃)₂]₂(2), are formed by reaction of (CF₃)₂AsCl and (CF₃)AsCl₂ with LiN(SiMe₃)₂. Chlorination of (1) yields [(CF₃)₂As(Cl)N(SiMe₃)]₂(3). On refluxing (3) in n-hexane or n-heptane, the synthesis of trimeric and tetrameric bis(trifluoromethyl)arsazenes, [(CF₃)₂AsN]₃(4) and [(CF₃)₂AsN]₄(5), is accomplished. Pyrolysis of (3) also produced (4) and (5). Crystals of (5) are triclinic, space group P, with a= 991.2(5), b= 1 012.9(6), c= 1 432.8(7) pm, α= 108.21(4), β= 96.03(4), γ= 109.44(4)°, and Z= 2. The structure was solved by direct methods and refined to R 0.069 for 2 183 unique observed diffractometer data. The molecular symmetry approximates to (S₄), with a slight alternation in As–N distances [171.6(7) and 173.2(9) pm].