Acid/Base and Solids
What is the name for a species that donates a pair of electrons to another species?
A Lewis base! Lewis bases donate electrons, while Lewis acids are electron acceptors.
True or false: Pi acceptor ligands are named as such because they accept electrons in a backbonding fashion.
True! They accept electrons in the lowest energy orbital set possible!
An improper rotation involves two symmetry elements. What are they?
A rotation, followed by reflection.
There are two criteria for atomic orbitals to combine to form molecular orbitals. What are these criteria?
1. Good spatial overlap, and 2. good energetic overlap.
True or false: A complex with a large splitting energy is more likely to appear orange than blue.
True! A larger splitting energy means a shorter wavelength will promote the d to d transition.
True or false: Al3+ is a harder acid than Ga3+. Explain your reasoning!
True! Hard acids feature high charges and small atomic/ionic sizes.
The chelate effect is related to denticity in which way?
Name the point group for the following molecule:
C6v!
14 eV!
True or false: Ti3+ is just as likely to be elongated as it is compressed.
False! Comparing the changed d orbital diagrams, we see that compression is favored due to even electron pairing.
True or false: Lattice energy calculations consider atoms in their solid state coming together to form a solid.
False! Lattice energy calculations consider atoms starting in their gaseous state --> solid.
Is K3[FeBr6] considered a labile complex? Why or why not?
Yes! This complex is d5 and high-spin, meaning there are electrons in the eg (highest orbital set in this case).
H3O+ has this type of molecular geometry:
Trigonal pyramidal!
List all quantum numbers for the following orbital: 5d
n = 5, l = 2, ml = -2, -1, 0, 1, 2, ms = either + or - 1/2
True or false: More electronegative atoms serving as sigma donors are stronger sigma donors than less electronegative atoms.
False! They would be weaker. They hold onto their electrons more strongly, meaning less electron density is delivered to the metal.
For the following, predict whether or not Keq will be > or < 1 (and pretend the arrow is an eq. arrow)!
Cl3Co-PMe3 + Cl3Ir-NMe3 --> Cl3Co-NMe3 + Cl3Ir-PMe3
Keq > 1 because P and Ir are both softer than Co and N.
True or false: If Rh is in the 3+ state and is surrounded by 6 pi acceptor ligands, there is weak JTD.
False! Rh in the 3+ state means 6 d electrons, and pi acceptor ligands indicate a strong field. There would be no JTD.
Name the point group for the following molecule:
Cs!
True or false: F2+ has a bond order of 1.5.
True! MO theory shows us 8 electrons in bonding orbitals and 5 electrons in anti-bonding orbitals.
True or false: A 17 electron complex with 6 ligands is just as likely to undergo an associative mechanism as it is a dissociative mechanism.
False! Steric crowding is at play here. It would likely undergo dissociation.
Derive the empirical formula for the following solid:
AB3C4
Give the total number of electrons for the following complex (and indicate hapticity/number of electrons donated for each ligand):
Fe is 3+, 5 d electrons, two electrons from all 5 ligands = 15 total electrons
A D2h point group has E, 3 different C2 axes of rotation, 2 different sigma v planes, a sigma h plane, and what other symmetry element?
An inversion center!
Compare the MO diagrams for CO- and CO+. Which has a stronger bond? Explain.
Both have a bond order of 2.5!
Which wavelength of light is absorbed by a complex if the splitting energy of the complex = 4.16 x 10-19 J? What color is the complex in question?
The wavelength absorbed is ~478 nm, and the complex will be reddish-orange in color.