Question

The acetylacetonate ion \(\left(\operatorname{acac}^{-}\right)\) CCC(=O)CC=C(C)O forms complexes with many metal ions. Sketch the geometry of \(\mathrm{Fe}(\mathrm{acac})_{3}\)

Short answer

Answer: The coordination geometry of the Fe(acac)₃ complex is octahedral. This is because the complex has a coordination number of 6, with each acac⁻ ligand acting as a bidentate ligand, coordinating to the central iron atom via two donor atoms. Octahedral geometry is typical for complexes with a coordination number of 6.

Step-by-step solution

Identify the central metal ion and ligands

The central atom in this complex is the iron (Fe) atom, and the ligands are the acetylacetonate ions, (acac⁻).

Determine the coordination number of the central metal ion

The coordination number refers to the number of ligand donor atoms attached to the central metal ion. Each acac⁻ ligand acts as a bidentate ligand, which means it uses two donor atoms to coordinate with the central metal ion. Since we have three acac⁻ ligands, the coordination number of the Fe atom is 3 × 2 = 6.

Identify the coordination geometry of the complex

Based on the coordination number, we can predict the coordination geometry of the complex. For a coordination number of 6, the typical geometries are octahedral or distorted octahedral. In this case, the Fe(acac)₃ complex has an octahedral geometry due to the bidentate ligands.

Sketch the geometry of the complex

To sketch the Fe(acac)₃ complex, draw the central iron atom with six coordination sites arranged in an octahedral geometry. Then, attach the acac⁻ ligands so that each one connects to two coordination sites (with the oxygen atoms from the carbonyl and alcohol groups). Be sure to show all the atoms and bonds in the ligands, but it's not essential to include other organic groups in this simplified sketch. It should look like an octahedron surrounding the Fe atom with three acac⁻ ligands bridging every pair of vertices.