Zintl phases of arsenic and molecular compounds containing Zintl-type polyarsenide ions are of fundamental interest in basic and applied sciences.U nfortunately,t he most obvious and reactive arsenic source for the preparation of defined molecular polyarsenide compounds,y ellowa rsenic As 4 ,i sv ery inconvenient to prepare and neither storable in pure form nor easy to handle.Herein, we present the synthesis and reactivity of elemental As 0 nanoparticles (As 0 Nano ,d= 7.2 AE 1.8 nm), which were successfully utilized as ar eactive arsenic source in reductive f-element chemistry.S tarting from [Cp* 2 Sm] (Cp* = h 5 -C 5 Me 5 ), the samarium polyarsenide complexes [(Cp* 2 Sm) 2 (m-h 2 :h 2 -As 2 )] and [(Cp* 2 Sm) 4 As 8 ]w ere obtained from As 0 nano ,therebygenerating the largest molecular polyarsenide of the f-elements and circumventing the use of As 4 in preparative chemistry.Zintl phases and Zintl ions have been thoroughly investigated in the solid state and molecular chemistry for decades. [1] Particularly,p olypnictides (Pn = P, As,S b, Bi) feature arich chain and cage chemistry with, for example,the polycyclic [P 7 ] 3À anion as one of the most prominent examples. [2] When it comes to molecular coordination compounds,w hich incorporate polypnictide ions,p revious research has been almost entirely focused on transition metals and phosphorus.