Question #44586

The problem tests multiple exceptions to standard Valence Bond Theory (VBT) and Crystal Field Theory (CFT). 1) Steric override: Bulky $PPh_3$ forces $3d^8$ $Ni^{2+}$ into a tetrahedral geometry, bypassing the expected square planar $dsp^2$ hybridization. 2) Heavy metal anomaly: $5d^8$ $Pt^{2+}$ ignores sterics due to massive CFSE, remaining square planar. 3) Octahedral $d^8$ trap: Strong field ligands cannot force pairing in $Oh$ $d^8$ systems. 4) Oxidation state effect: $Co^{3+}$ turns the typically weak-field oxalate into a strong-field ligand. 5) Brown ring anomaly: $Fe^+$ forms a high-spin $d^7$ complex despite the strong $NO^+$ ligand.