Question #44553

An aqueous solution of \ce{Fe^{2+}} reacts with a bulky, potentially bidentate neutral ligand $L$ at $273\text{ K}$ to form an octahedral complex $X$ with the formula \ce{[FeL_6]^{2+}}. In complex $X$, severe inter-ligand steric crowding forces $L$ to act as a monodentate ligand, resulting in a weak ligand field ($\Delta_o < P$). Upon heating the solution to $350\text{ K}$, complex $X$ undergoes a 'denticity flip', expelling three equivalents of $L$ to relieve steric strain and forming a new octahedral complex $Y$ with the formula \ce{[FeL_3]^{2+}}. In complex $Y$, $L$ acts as a bidentate chelating ligand, and the resulting chelate effect significantly increases the crystal field splitting energy such that $\Delta_o > P$.

Identify the correct set of parameters for the transformation $X \rightarrow Y$ in the following order: [Hybridization change, $\Delta\mu_{eff}$, $\Delta n_{t_{2g}}$]. (Where $\Delta\mu_{eff} = |\mu_{eff}(Y) - \mu_{eff}(X)|$ in Bohr Magnetons, and $\Delta n_{t_{2g}}$ is the change in the number of electrons in the $t_{2g}$ orbitals).