The compounds [NEt,],[Ni$e,(Se,),(Se,)] axNEt& (x= 0, 1) and [NEt&[Ni.,Te4(Te2)2(Te3)41 have been prepared from the reaction in DMF of Ni(S2COEt)2 with L&Se and Se or Li,Te and Te, respectively. These compounds result from spontaneous assembly reactions in which Nix1 centers are oxidized to Niw with concomitant reduction of Se-or Te-containing species. The anion [Ni,Se4(Se&(Se,)]"-possesses a N&Se, cubane core and has five Se,'-chains and one Se,'-chain bridging the Ni atoms on the cubane faces. The anion [Ni,Te,(Te2),(Te&14has a N&Ted cubane core and has two Tez2-chains bridging Ni atoms on opposite faces of the cubane core and four Te,'-chains bridging the NiIV atoms on the remaining cubane faces. The presence of NiN is necessitated by charge balance. As expected for such d6 systems the compounds are diamagnetic. The [Ni,Se,(Se,),(Se,)]'anion exhibits a sharp, albeit complex, "Se NMR spectrum with fifteen resonances at 6 103, 134, 289, 361, 387, 401, 411, 470, 660, 680, 726, 749, 773, 789 and 804 ppm. The [Ni4Te,(Te2)2(Teg),]4-anion exhibits a simpler '=Te NMR spectrum with five resonances at 6 -632, -324, 65, 325 and 766 ppm. In the cubane anions each Ni atom is in a distorted octahedral environment, being coordinated by three Se or Te atoms in the cubane framework and by three Se or Te atoms in chains that bridge to the other three Ni atoms. While the bridging Ser2-chains appear to produce little strain on the Ni4Se4 cubane core, the 2-Se, chain distorts it, as evidenced from the Ni-Ni distances, the Se,U,-Se,,r, distances and the cubane bond angles. In contrast, the bridging Tea'chains distort the Ni,Te, cubane core as evidenced from the Ni-Ni distances, the Tecub-Tecub distances and the cubane bond angles; the Tez2-chains produce less strain. [NEt,],[Ni$e,(SeS)~(Se,)l*NEt&l crystallizes in the monoclinic space group CL-P2Jn with a =21.817(4), b = 14.319(l), c=26.421(5) A, /?=112.69(2)", I'=7615 A3 and Z = 4 ( -120 "C). [NEt4]4[Ni4Te4(Te2)2(Te3)~] crystallizes in the triclinic space group C,'-Pi with a = 14.399(2), b = 15X3(2), c = 18.069(3) A, cu=70.97(1), /3=79.05(l), y=74.2O(l)O, I'=3564 A3 and Z=2 (-167 "C).