Complex sentence: In this compound, each of the iridium atoms is bonded to the other three, forming a tetrahedral cluster, which, unlike Co 4 (CO) 12, has exclusively terminal carbonyl ligands.
Split into simpler sentences: In this compound each iridium centre is bonded to the three others, forming a tetrahedral cluster. Unlike Co 4 (CO) 12, this Ir 4 cluster exclusively features terminal carbonyl ligands.