The compounds [NEt4]4[Ni4Se4(Se3)5(Se4)]·xNEt4Cl (x=0, 1) and [NEt4]4[Ni4Te4(Te2)2(Te3)4] have been prepared from the reaction in DMF of Ni(S2COEt)2 with Li2Se and Se or Li2Te and Te, respectively. These compounds result from spontaneous assembly reactions in which NiII centers are oxidized to NiIV with concomitant reduction of Se- or Te-containing species. The anion [Ni4Se4(Se3)5(Se4)]4- possesses a Ni4Se4 cubane core and has five Se32- chains and one Se42- chain bridging the Ni atoms on the cubane faces. The anion [Ni4Te4(Te2)2(Te3)4]4- has a Ni4Te4 cubane core and has two Te22- chains bridging Ni atoms on opposite faces of the cubane core and four Te32- chains bridging the NiIV atoms on the remaining cubane faces. The presence of NiIV is necessitated by charge balance. As expected for such d6 systems the compounds are diamagnetic. The [Ni4Se4(Se3)5(Se4)]4- anion exhibits a sharp, albeit complex, 77Se NMR spectrum with fifteen resonances at δ 103, 134, 289, 361, 387, 401, 411, 470, 660, 680, 726, 749, 773, 789 and 804 ppm. The [Ni4Te4(Te2)2(Te3)4]4- anion exhibits a simpler 125Te NMR spectrum with five resonances at δ -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 Se32- chains appear to produce little strain on the Ni4Se4 cubane core, the Se42- chain distorts it, as evidenced from the NiNi distances, the SecubSecub distances and the cubane bond angles. In contrast, the bridging Te32- chains distort the Ni4Te4 cubane core as evidenced from the NiNi distances, the TecubTecub distances and the cubane bond angles; the Te22- chains produce less strain. [NEt4]4[Ni4Se4(Se3)5(Se4)]·NEt4Cl crystallizes in the monoclinic space group C52h-P21/n with a=21.817(4), b=14.319(1), c=26.421(5) Å, β=112.69(2)°, V=7615 Å3 and Z=4 (-120 °C). [NEt4]4[Ni4Te4(Te2)2(Te3)4] crystallizes in the triclinic space group Ci1-P1 with a=14.399(2), b=15.153(2), c=18.069(3) Å, α=70.97(1), β=79.05(1), γ=74.20(1)°, V=3564 Å3 and Z=2 (-167 °C).
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry