Preparative and Electrochemical Investigations on the Electron Sponge Behavior of Cobalt Telluride Clusters: CO Substitution in [Co11Te7(CO)10]n−Ions (n=1, 2) by PMe2Ph and Crystal Structure of [Co11Te7(CO)5(PMe2Ph)5]

The reaction of the cluster salts [Cp${^{{\ast}}_{2}}$Nb(CO)2]n[Co11Te7(CO)10] (Cp*=C5Me5; n=1, 2) with excess PMe2Ph gave the neutral, dark brown clusters [Co11Te7(CO)6(PMe2Ph)4] (5) and [Co11Te7(CO)5(PMe2Ph)5] (6) with 147 metal valence electrons. The new compounds were characterized by IR spectroscopy, elemental analyses, and mass spectrometry. The molecular structure of 6was determined by X‐ray crystallography. Like its precursor anion, it consists of a pentagonal‐prismatic [Co11Te7] core, but with a ligand sphere composed of five CO and five PMe2Ph ligands. Detailed electrochemical studies of both reactions reveal that a stepwise substitution of CO ligands in the initial cluster anions takes place leading to intermediate [Co11Te7(CO)10−m(PMe2Ph)m]n−ions (m=1–5; n=1, 2). Each of these intermediates is distinguished by at least one oxidation and two reduction waves, giving rise to a total of 21 redox couples and 27 electroactive species. The electron sponge character of the new compounds is particularly pronounced in 5, which exhibits charges nbetween +1 and −4 corresponding to metal valence electron counts of between 146 and 151.