Jahn-Teller Distortion Quiz and Flashcards: Octahedral Metal Ions

What is the significant role of Rh(I) and Ir(I) in organometallic catalysis?

What is the result of dissolving planar Ni(II) complexes in a good donor solvent?

What is the characteristic of Lifschitz salts?

What is the result of a mixture of square planar and octahedral complexes in solution?

What is the factor that determines the preference for square planar over tetrahedral geometry?

What is the consequence of a mixture of square planar and tetrahedral complexes in solution?

What is the role of the crystal field in determining the geometry of a complex?

What is the Jahn-Teller effect relevant to?

What is the significance of the Lifschitz salts in the context of organometallic catalysis?

What is the result of the expansion of the coordination sphere of Rh(I) and Ir(I) in organometallic catalysis?

Jahn-Teller Effect

A non-linear molecule in a degenerate electronic state will distort to remove degeneracy
Observed in octahedral metal ions with specific electron configurations:
- d1, d2, d4 (HS or LS), d5 (LS), d6 (HS), d7 (HS or LS), and d9
Effects are most obvious when the eg* level is unevenly occupied (e.g., HS d4, LS d7, and d9)

Structural Consequences of Jahn-Teller Effect

With bidentate ligands:
- Often cannot form conventional tris-chelate complexes
- Ligand backbone cannot accommodate axial elongation at the metal
With monodentate ligands:
- Substantial axial elongation
- May lose one or both axial ligands

Ligand-Field Stabilization Energies (LFSE)

LFSEs are greater for octahedral than tetrahedral complexes
In octahedral complexes, LFSE is greater due to the splitting of degenerate energy levels

Jahn-Teller Distortion

In Cu2+, there are two ways to arrange eg* electrons, leading to elongation of bonds:
- (dz2)2(dx2-y2)1: elongation on the z-axis
- (dz2)1(dx2-y2)2: elongation in the xy plane
Elongation on the z-axis is favored due to symmetry arguments
Net result: bonds on the z-axis elongate, and bonds in the xy plane compress

Other Configurations

Jahn-Teller distortions are also expected for:
- Tetrahedral metal ions in the ground state: d1, d3, d4, d8, and d9
- Other configurations may also exhibit Jahn-Teller distortions

Square Planar Complexes

Rh(I) and Ir(I) are often square planar with p acceptor ligands
May expand their coordination sphere (important in organometallic catalysis)
Planar/octahedral equilibria can be finely balanced, leading to anomalous magnetic behavior
Examples: Lifschitz salts, [Ni(L-L)2]X2 (sq. pl) or [Ni(L-L)2X2] (oct.)

This quiz covers the Jahn-Teller distortion effects in octahedral metal ions, including the ground state and high-spin or low-spin configurations. It also explains the uneven occupancy of t2g and eg* levels and its effects on the complex.