Chapter 20: Practice Flashcards
mupasar
Explain why the CFSE for a low-spin d 5 configuration contains a 2P term
The CFSE for a low-spin d5 configuration contains a 2P term due to the presence of two electrons in the lower energy t2g level, leading to pairing energy (P).
Given that [Co(OH2)6]^3+ is low-spin, explain why it is possible to predict that [Co(bpy)3]^3+ is also low-spin.
Predicting the Spin State of [Co(bpy)₃]³⁺
Metal Ion: The metal ion remains the same, Co³⁺.
Ligand: 2,2’-bipyridine (bpy) is a strong-field ligand.
Strong-field ligands induce a larger energy splitting (Δ₀) compared to weak-field ligands. This larger splitting further favors the low-spin configuration.
Given that Co³⁺ inherently favors low-spin complexes, and bpy is a strong-field ligand that further enhances the energy splitting, it is reasonable to predict that [Co(bpy)₃]³⁺ will also be a low-spin complex.
in low-spin [Co(NH3)6]3+, 18 electrons (six from Co3+ and two from each ligand) occupy the a1g, t1u, eg and t2g MOs;
In high-spin [CoF6]3-, 18 electrons are available, 12 occupying the a1g, t1u and eg MOs, four the t2g level, and two the eg level
The complexes [NiCl2(PPh3)2] and [PdCl2(PPh3)]2 are paramagnetic and diamagnetic respectively. What does
this tell you about their structures?
The fact that the complex [NiCl2(PPh3)2] is paramagnetic and [PdCl2(PPh3)2] is diamagnetic indicates that the complexes have different structures due to the number of unpaired electrons in each:
[NiCl2(PPh3)2]
This complex is paramagnetic because it has unpaired electrons. This is due to the fact that nickel (Ni) is a 3d metal , and chlorine is a weak field ligand that is unable to pair the electrons in nickel.
[PdCl2(PPh3)2]
This complex is diamagnetic because it has no unpaired electrons. This is due to the fact that palladium (Pd) is a 4d metal, and the high value of crystal field splitting energy (Δ) favors pairing of electrons.
The anion [Ni(SPh)4]2 is tetrahedral. Explain why it is paramagnetic.
In a tetrahedral complex, the d-orbitals split into two sets: e and t₂.
Thiolate ligands (SPh⁻) are weak-field ligands. Weak-field ligands do not cause significant splitting of the d-orbitals.
The presence of unpaired electrons makes the complex paramagnetic.
Therefore, the tetrahedral geometry and the weak-field ligands contribute to the paramagnetic behavior of [Ni(SPh)₄]²⁻.
A _____________ donates electrons to the metal centre in an interaction that involves a filled ligand orbital and an empty metal orbital.
π-donor ligand
A ________________ accepts electrons from the metal centre in an interaction that involves a filled metal orbital and an empty ligand orbital.
π-acceptor ligand
Show that Cr(CO)6 obeys the 18-electron rule
The Cr(0) centre has six valence electrons.
CO is a π-acceptor ligand, and each CO ligand is a 2-electron donor. The total electron count at the metal centre in Cr(CO)6
6+ (6 x 2) = 18.
a) How many electrons does a PPh3 ligand donate? (b)Use your answer to (a) to confirm that the Fe centre in
Fe(CO)4(PPh3) obeys the 18-electron rule.
2
What is the oxidation state of each metal centre in the complexes in question
(a) Fe(CO)5
(b) Ni(CO)4
(c) [Mn(CO)5]-
(d) Mo(CO)6
(a) 0
(b) 0
(c) -1
(d) 0
Show that an s1 configuration corresponds to a 2S term
For a single electron, S = 1/2.
For an s orbital, l = 0
For total angular momentum
In this case, J = |0 - 1/2| to |0 + 1/2| = 1/2.
Multiplicity (2S+1): 2(1/2) + 1 = 2
Orbital Angular Momentum (L): 0 corresponds to S
Show that a d1 configuration corresponds to a 2D term
For a single electron, S = 1/2.
For an d orbital, l = 2
For total angular momentum
In this case, J = |0 - 1/2| to |0 + 1/2| = 3/2.
