[Co(NH3)6]3+ and [CoF6]3- are respectively known as:

🧠 Both Are Co(III) — d⁶ — Differ Only in Ligand

$[\mathrm{Co(NH_3)_6}]^{3+}$: NH₃ is a strong-field ligand → $\Delta_o > P$ → low-spin → $t_{2g}^6 e_g^0$ → 0 unpaired.

$[\mathrm{CoF_6}]^{3-}$: F⁻ is a weak-field ligand → $\Delta_o < P$ → high-spin → $t_{2g}^4 e_g^2$ → 4 unpaired.

🗺️ Terminology Map

| Term | Meaning | |---|---| | Spin paired / low-spin / inner-orbital | Strong field, $\Delta_o > P$, electrons pair within $t_{2g}$ | | Spin free / high-spin / outer-orbital | Weak field, $\Delta_o < P$, electrons spread to $e_g$ |

So $[\mathrm{Co(NH_3)_6}]^{3+}$ is spin paired (low-spin / inner-orbital). $[\mathrm{CoF_6}]^{3-}$ is spin free (high-spin / outer-orbital).

⚡ Inner vs Outer Orbital (VBT Language)

In VBT terminology:

• Inner-orbital complex = low-spin = uses inner (n−1)d orbitals for hybridisation → $d^2sp^3$.
• Outer-orbital complex = high-spin = uses outer nd orbitals → $sp^3d^2$.

For Co(III) d⁶: NH₃ pushes electrons to pair (inner orbital, $d^2sp^3$); F⁻ leaves them spread (outer orbital, $sp^3d^2$).

⚠️ Don't Confuse "Spin Free" with "Unpaired"

"Spin free" doesn't mean "all spins unpaired" — it means electrons are free to occupy higher $e_g$ orbitals (not forced to pair below). Some pairing within $t_{2g}$ may still occur due to Hund's rule.

$\boxed{\text{Answer: (2) Spin paired Complex, Spin free Complex}}$