Synthesis and Characterization of Cobalttelluride Clusters with the Cubic Body-Centered Co9Te6(CO)8 Core

Reduction of Cp₂NbTe₂H (Cp=tBuC₅H₄) with CH₃Li results in a red-violet solution which reacts with Co₂(CO)₈ to give the neutral cluster {Cp₂Nb(CO)}₂Co₉Te₆(CO)₈] (2) and a mixture of salts, from which Na(THF)₆]Co₉Te₆(CO)₈] (4) was obtained by crystallization from THF in very poor yield, probably due to Na impurities in CH₃Li. Clusters 2 (123 valence electrons) and 4 (122 valence electrons) possess hexacapped cubic Co@Co₈ cores. The structure of 2 was identified by comparison of spectroscopic data with those of parent clusters: Two Cp₂Nb(CO) fragments are fixed at two opposite ₄-Te bridges of the Co₉Te₆(CO)₈ skeleton. A crystal structure determination of 4 shows this compound to contain discrete ions. Nearly equal diameters of ca. 10.5Å for the Co₉Te₆(CO)₈]^– anion and the octahedral Na(THF)₆]⁺ cation as well as electrostatic interactions between them and attractive C–HO contacts may be responsible for the formation of layers throughout the crystal.