The coordination geometry around the manganese in decacarbonyldimanganese 0

Around the manganese atom, there are five $\mathrm{CO}$ ligands and one Mn occupying octahedron vertices. For octahedral geometry, the more appropriate hybridization is ${\mathrm{d}}^2{\mathrm{sp}}^3$ that produces six hybrid orbitals pointing towards $\mathrm{CO}$ and $\mathrm{Mn}$.

The octahedral shape of molecules is the shape of molecules where six atoms or ligands or groups of atoms are arranged in a systematic way around a central dogma or atom. The Octahedral Shape of Molecules molecules has eight faces.