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In the area of metal cluster chemistry, a butterfly cluster compound usually describes tetrametallic clusters containing five M-M bonds. A prototype of this motif is e4(CO)16sup>2−. Most butterfly clusters have additional
In the area of metal cluster chemistry, a butterfly cluster compound usually describes tetrametallic clusters containing five M-M bonds. A prototype of this motif is e4(CO)16sup>2−. Most butterfly clusters have additional bridging ligand
In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually r ...
s. One example is the penta phosphide Rh4(CO)5(PPh2)5− where all Rh---Rh edges are bridged by PPh2. A carbide-containing butterfly cluster is e4C(CO)12sup>2− where the carbide is bonded to all four Fe centers.{{cite journal, authors=Sappa, E.; Tiripicchio, A.; Carty, A. J.; Toogood, G. E., title=Butterfly Cluster Complexes of the Group VIII Transition Metals, journal=Progress in Inorganic Chemistry, year=1987, volume=35, page=437, doi=10.1002/9780470166369.ch5, isbn=9780470166369
Bonding in such clusters is often discussed in the context of polyhedral skeletal electron pair theory. This theory predicts that tetrametallic clusters with 60 valence electrons will adopt tetrahedral geometry with six M-M bonds. Tetrahedral clusters is classified as ''nido'' clusters. By addition of 2e, the 60e cluster opens one edge, as manifested in the butterfly motif.
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