sp3d2

sp3d2 refers to a type of hybridization in valence bond theory in which one s, three p, and two d atomic orbitals of a central atom mix to form six equivalent sp3d2 hybrid orbitals. This set of orbitals is oriented toward the corners of a regular octahedron and is used to describe octahedral coordination geometry in many compounds, especially transition metal complexes.

In the valence bond picture, the six ligands donate electron pairs to form sigma bonds using these six hybrid orbitals, resulting in an octahedral arrangement with approximate 90-degree metal–ligand angles. The two d orbitals involved are typically those of appropriate symmetry to participate in bonding with the ligands, often dz^2 and dx^2−y^2, though the exact d-orbital choice is not unique and depends on the specific system.

sp3d2 is a simplified, qualitative description of bonding. Modern interpretations of bonding in coordination compounds often employ molecular orbital theory or ligand field theory rather than explicit hybridization schemes. Thus, sp3d2 (and its interchangeable notation d2sp3) is commonly used as an instructional model to rationalize octahedral geometry, rather than as a precise account of electron distribution.

Applications and examples include octahedral complexes of transition metals such as [Co(NH3)6]3+ and [Fe(H2O)6]3+, as well as non-metal octahedral species like SF6. Limitations arise for elements lacking accessible d orbitals and in cases where strong ligand interactions distort idealized geometry or challenge simple VB descriptions.