The reaction of m-terphenyl amine (2,6-bis-(2,4,6-trimethylphenyl)aniline, m-Ter = m-terphenyl = 2,6-bis-(2,4,6-trimethylphenyl)) and ECl(3) (E = P, As) in the presence of different bases (Et(3)N, n-BuLi, LDA, DBU) and under different reaction conditions was studied. The reaction with excess Et(3)N yielded m-Ter-N(H)-AsCl(2) for E = As, while for E = P m-Ter-N(PCl(2))(2) was formed. m-Ter-N(H)-ECl(2) was obtained in the reaction of m-terphenyl amine with n-BuLi and ECl(3) for E = As and P. Further treatment of m-Ter-N(H)-PCl(2) with Et(3)N led to the formation of 1,3-dichloro-cyclo-1,3-diphospha-2,4-diazane, a synthesis protocol which cannot be applied to the analogous arsenic species. 1,3-dichloro-cyclo-1,3-diarsa-2,4-diazane was isolated when DBU was added to m-Ter-N(H)-AsCl(2) at low temperature (-80 °C).