Nickel(II) complexes with the formula NiX₂L₂

Question

Nickel(II) complexes with the formula NiX₂L₂, where X⁻ is Cl⁻ or N-bonded NCS⁻ and L is the monodentate triphenylphosphine ligand P(C₆H₅)₃, can be square planar or tetrahedral.

(a) Draw crystal field energy-level diagrams for a square planar and a tetrahedral nickel(II) complex, and show the population of the orbitals.

Accepted Answer

Identify the electron configuration of the central metal ion, Nickel(II) $$(Ni^{2+}). $$Nickel in its +2 oxidation state has a $$d^{8}$$ electron configuration.. Understand the difference in geometry for square planar and tetrahedral complexes. In square planar complexes, the ligands are arranged at 90-degree angles around the central metal in the same plane. In tetrahedral complexes, the ligands are arranged at approximately 109.5 degrees in a three-dimensional structure.. Draw the crystal field splitting diagram for a square planar complex. In this geometry, the d-orbitals split into two non-degenerate orbitals (d_{$$z^{2}$$} and d_{$$x^{2}-y$$^{2}$$}) at higher energy, and three degenerate orbitals (d_{xy}, d_{xz}, d_{yz}) at lower energy.. Draw the crystal field splitting diagram for a tetrahedral complex. Here, the d-orbitals split differently: two orbitals (d_{xy}, d_{xz}, d_{yz}) are at lower energy, and three orbitals (d_{z$$^{2}$$} and d_{x$$^{2}$$-y^{2}$$}) are at higher energy.. Populate the orbitals with the $$d^{8}$$ electrons of $$Ni^{2+}$$ according to the Aufbau principle, Hund's rule, and the Pauli exclusion principle, for both square planar and tetrahedral diagrams. In square planar, fill the lower energy set first, then the higher; in tetrahedral, distribute the electrons starting from the lower energy orbitals.

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Key Concepts

Crystal Field Theory

Ligand Field Splitting

Coordination Geometry