Manganese-carbonyl complex geometry

The first metallocarborane of this geometry to be synthesized was an unexpected product. In an attempt to prepare a ten-vertex manganese carbonyl complex, the C2B7Hii2 ion, discussed in Section VII, was reacted with BrMn(CO)5. Surprisingly, the only metal-containing compound isolated from the reaction mixture had just 6 boron atoms (36, 50). The course of the reaction may be outlined as follows ... 

Organometallic Molecules.— With one exception, all the complexes in this section are manganese carbonyls. They are mostly mononuclear and with octahedral geometry around the manganese atom. 

In the cobalt complex, each cobalt atom has a trigonal bipyramidal coordination geometry, whereas, in the manganese complex, each manganese atom is octahedrally coordinated. In both cases, the equatorial carbonyl groups are bent towards the central mercury atom. The structures of the related compounds... 

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