Square antiprismatic geometry isomers

Several isomeric forms of the first trimetallocarbaborane containing Ni have been isolated and characterized. They have the formula (CpNi)3CBsH5R, where R = H or Me. They are mixed-valence species, Ni -Ni -Ni, with substantial charge transfer. The crystal structure of one isomer was determined, showing a novel nido-geometry, with a monocapped square antiprismatic skeleton (Figiure 9)66... 

The interpretation of the observed proton and C PCS led to the conclusion that the two structural isomers are enantiomeric pairs of diastereoisomers differing in the octadentate ligand conformation, namely, capped square antiprismatic (SA or M) and twisted capped square antipris-matic (TSA or m) geometries, respectively (Figure 5). " The Ln + coordination polyhedral of SA and TSA have two opposite parallel faces occupied by the ligand ring nitrogen... 

---