Synthesis, structures and coordination behaviour of [As(NR)_3]~(3-) trianions

摘要

Re-examination of the X-ray structure of the imido As(III) complex previously formulated as [{As(N~tBu)_3}_2Li_6](centre dot)benzene (1(centre dot)benzene) indicates that the disorder within the [{As(N~tBu)_3}_2Li_6] cage can be better explained by the molecular formulae [{As(N~tBu)_3}_2Li_6](centre dot)[LiNH~tBu]_6 or [{As(N~tBu)_3}Li_3(centre dot)(~tBuNHLi)_3]. The syntheses and X-ray structures of the new complexes [{As(N(2-MeO-C_6H_4)_3)}_2Li_6(centre dot)2TMEDA] (3) and [As{N(2-py)}_3(centre dot)LiN(2-py)(centre dot)3thf[_2(centre dot)2thf(4(centre dot)2thf), containing [As(NR)_3]~(3-) anions, are reported. Attempts to prepare the heteroloeptic trianion [As(NCy)_2(NCH_2Ph)]_3~- via reaction of the arsazane dimer [CyNHAs(mu#-NCy)]_2 (5) with PhCH_2NHLi (1:6 equivalents) led to the unexpected formation of Zintl compound containing the As_7~(3-) anion. The X-ray structure of [As_7Li_3(centre dot)3(CyNH_2)3thf] 6 is also reported.