Preparative and Electrochemical Investigations on the Electron Sponge Behavior of Cobalt Telluride Clusters: CO Substitution in [Co 11 Te 7 (CO) 10 ] n − Ions ( n =1, 2) by PMe 2 Ph and Crystal Structure of [Co 11 Te 7 (CO) 5 (PMe 2 Ph) 5 ]

The reaction of the cluster salts [Cp ${^{{\ast}}_{2}}$ Nb(CO) 2 ] n [Co 11 Te 7 (CO) 10 ] (Cp*=C 5 Me 5 ; n =1, 2) with excess PMe 2 Ph gave the neutral, dark brown clusters [Co 11 Te 7 (CO) 6 (PMe 2 Ph) 4 ] ( 5 ) and [Co 11 Te 7 (CO) 5 (PMe 2 Ph) 5 ] ( 6 ) with 147 metal valence electrons. The new compounds were characterized by IR spectroscopy, elemental analyses, and mass spectrometry. The molecular structure of 6 was determined by X‐ray crystallography. Like its precursor anion, it consists of a pentagonal‐prismatic [Co 11 Te 7 ] core, but with a ligand sphere composed of five CO and five PMe 2 Ph 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 [Co 11 Te 7 (CO) 10− m (PMe 2 Ph) 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 n between +1 and −4 corresponding to metal valence electron counts of between 146 and 151.