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Ch.21 - Transition Elements and Coordination Chemistry
All textbooksMcMurry 8th EditionCh.21 - Transition Elements and Coordination ChemistryProblem 21.131c
Chapter 21, Problem 21.131c

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.
(c) Draw possible structures for each of the NiX2L2 complexes, and tell which ones have a dipole moment.

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Identify the coordination number and geometry: For the NiX2L2 complexes, where X is Cl- or N-bonded NCS- and L is P(C6H5)3, the coordination number is 4. The possible geometries for coordination number 4 are square planar and tetrahedral.
Draw the square planar structure: Place the Ni atom at the center. Arrange two X ligands opposite each other and two L ligands opposite each other at 90-degree angles around the Ni atom. This arrangement minimizes repulsion between ligands.
Draw the tetrahedral structure: Place the Ni atom at the center. Arrange the four ligands (two X and two L) at the corners of a tetrahedron around the Ni atom. Each ligand is approximately 109.5 degrees apart from the others.
Analyze symmetry for dipole moment: In the square planar structure, if the ligands X and L are different, the structure will have a dipole moment due to the asymmetry in the electron distribution. In the tetrahedral structure, if all ligands are identical or if the pairs of identical ligands are opposite each other, the structure will be nonpolar and have no dipole moment.
Consider the specific ligands: For NiCl2(P(C6H5)3)2, if arranged in a square planar geometry, it will have a dipole moment due to the different electronegativities of Cl and P(C6H5)3. In a tetrahedral arrangement, the molecule could be nonpolar if the Cl and P(C6H5)3 ligands are arranged symmetrically opposite each other.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Coordination Chemistry

Coordination chemistry involves the study of complex compounds formed between metal ions and ligands. In this context, nickel(II) complexes are formed with ligands such as triphenylphosphine and halides. Understanding the nature of these interactions is crucial for predicting the geometry and properties of the resulting complexes.
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Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule. Nickel(II) complexes can adopt different geometries, such as square planar or tetrahedral, depending on the ligands and their steric and electronic properties. This geometry influences the dipole moment and overall polarity of the complex.
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Dipole Moment

The dipole moment is a measure of the separation of positive and negative charges in a molecule, indicating its polarity. Complexes with an asymmetric distribution of charge will have a dipole moment, while symmetric ones may not. Identifying the geometry and ligand arrangement helps determine whether a complex has a dipole moment.
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Related Practice
Textbook Question

Two first-series transition metals have three unpaired electrons in complex ions of the type [MCl4]2-.

(a) What are the oxidation state and the identity of M in these complexes?

(b) Draw valence bond orbital diagrams for the two possible ions.

(c) Based on common oxidation states of first-series transition metals (Figure 21.6), which ion is more likely to exist?

<QUESTION REFERENCES FIGURE 21.6>

Textbook 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.

Textbook 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.

(b) If NiCl2L2 is paramagnetic and Ni(NCS)2L2 is diamagnetic, which of the two complexes is tetrahedral and which is square planar?

Textbook Question

The amount of paramagnetism for a first-series transition metal complex is related approximately to its spin-only magnetic moment. The spin-only value of the magnetic moment in units of Bohr magnetons (BM) is given by sqrt(n(n + 2)), where n is the number of unpaired electrons. Calculate the spin-only value of the magnetic moment for the 2+ ions of the first-series transition metals (except Sc) in octahedral complexes with (a) weak-field ligands and (b) strong-field ligands. For which electron configurations can the magnetic moment distinguish between high-spin and low-spin electron configurations?

Textbook Question

Spinach contains a lot of iron but is not a good source of dietary iron because nearly all the iron is tied up in the oxalate complex [Fe(C2O4)3]3-.

(c) Draw a crystal field energy-level diagram for [Fe(C2O4)3]3-, and predict the number of unpaired electrons. (C2O42- is a weak-field bidentate ligand.)

Textbook Question

Spinach contains a lot of iron but is not a good source of dietary iron because nearly all the iron is tied up in the oxalate complex [Fe(C2O4)3]3-.

(d) Draw the structure of [Fe(C2O4)3]3-. Is the complex chiral or achiral?