The complex [Ni(H₂O)₆]²⁺ is octahedral with Δo = 102 kJ/mol…

In an octahedral field the $t_{2g}$ set lies at $-0.4\,\Delta_o$ and the $e_g$ set at $+0.6\,\Delta_o$. A d electron count of 4 to 7 gives high spin if $\Delta_o < P$ and low spin if $\Delta_o > P$. In a tetrahedral field the $e$ set lies at $-0.6\,\Delta_t$ and the $t_2$ set at $+0.4\,\Delta_t$, with $\Delta_t = \tfrac{4}{9}\Delta_o$. $\text{CFSE} = (-0.4\,n_{t_{2g}} + 0.6\,n_{e_g})\,\Delta_o$ in an octahedron.