A synthetic and structural study of the formation of cyclic [(RP)nE]− anions and Zintl compounds using E(NMe2)3 (E = As, Sb)

The low-temperature reactions of aliphatic primary phosphines and phosphides with E(NMe2)(3) (E=As, Sb) give cyclic anions of the type [(RP)(n)E](-). At higher temperatures Zintl compounds containing E-7(3-) anions are generated. In contrast, related reactions using aryl phosphines lead to the direct formation of Zintl compounds even at low temperature. The reactions of aliphatic and aryl arsines follow a similar pattern to that of the corresponding phosphines. The syntheses and X-ray structures of several complexes containing [(RP)(n)E](-) (n=3 or 4) and E-7(3-) anions are reported.